Anesthesiology for Trauma Medicine: Roles, Medications, Airway Management, and Multidisciplinary Team Coordination

Abstract

Given the complex nature of trauma, a highly organized, multidisciplinary approach is necessary to ensure the best possible outcomes. Anesthesia providers play a critical role in the management and effective treatment of trauma patients. This chapter will address both the multidisciplinary and multitiered management of trauma patients with a focus on the intersection of trauma staff and anesthesia in three phases: the initial evaluation (i.e., in the bay), intraoperative care, and postoperative care. Included is a brief discussion on more recent methodologies and newly incorporated technologies in the resuscitation of trauma patients.

1. Introduction

Multisystem trauma patients are medically complex largely due to the presence of shock. Therefore, their physiology significantly differs from those undergoing elective surgical procedures. Data has shown that emergent operative procedures demonstrate both increases in overall morbidity and mortality [1]. As perioperative partners, a collaboration between surgeons and anesthesia providers from the time of initial trauma response activation to immediate postoperative care is critical for improved patient outcomes. It is important to note that unlike other fields of surgery, trauma utilizes a well-established systematic approach to the initial management and stabilization of trauma patients.

The initial approach to trauma involves a rapid, systematic evaluation of the patient known as the primary and secondary surveys. Advanced Trauma Life Support (ATLS) is the most referenced approach that allows one to identify the most immediate threats to life through the ABCDEs of the primary survey [2]. The primary survey simplifies priorities. Any problems identified are promptly treated as they arise. This reduces the risk of not recognizing life-threatening injuries.

The primary survey progresses in sequential order from A to E as follows [2]:

Airway maintenance with cervical spine protection.

Breathing and ventilation.

Circulation with hemorrhage control.

Disability: neurologic status.

Exposure/Environmental control.

A hard stop occurs at each section when an intervention needs to be performed. Utilizing a systematic approach is imperative in settings with limited resources. However, at major trauma centers, multiple injuries may be attended to simultaneously.

Adjuncts are utilized during or immediately following the primary survey. Examples of adjuncts include vital sign monitoring, insertion of a urinary catheter to monitor urine output, focused assessment with sonography for trauma (FAST), extended FAST (eFAST), X-rays, and bloodwork. The adjunctive data help guide resuscitative efforts and should be re-evaluated as needed to ensure appropriate resuscitation of the patient.

Once the primary survey is completed and the patient is demonstrating hemodynamic stability, the secondary survey may begin. The focus shifts to collecting a complete history and performing a thorough physical examination to ensure injuries have not been missed. Important questions to ask about the patient’s history can be remembered using the mnemonic AMPLE: Allergies, Medications, Past illnesses/Pregnancy, Last meal, and Events/Environment related to the injury [2]. The head-to-toe physical exam should include a detailed neurological exam, and if indicated, the genitals and rectum should also be examined. Information regarding the mechanism of injury provides valuable insight into the types of injuries to expect and can help determine appropriate adjuncts to the secondary survey, including CT scans, additional X-rays, and other diagnostic imaging.

Overall, the medical approaches, diagnostic algorithms, and speed by which decisions are made in Trauma Medicine vary significantly in comparison to other medical fields. Unlike the Level I trauma patient that is transported to the emergency department, in the previous chapters, the majority of the patient populations were relatively hemodynamically stable, the patient’s history and medical management were well documented, and the acuity of the medical care provided was performed in an elective manner.

In this chapter, we will provide a brief introduction to the epidemiology of unintentional injury in the United States and discuss clinical practice updates in the field of trauma medicine, with emphasis on certain medical management strategies provided by trauma anesthesiologists. After the introduction, we will discuss patient management in the trauma bay, along with appropriate intraoperative and postoperative care following major surgery (Figure 1). Finally, we will discuss future directions regarding the management of trauma patients from an anesthesiologist’s perspective in conjunction with how the current landscape of trauma anesthesiology continues to evolve.

Figure 1.

Stepwise approach to preoperative, perioperative, and postoperative phase of case. MTP = massive transfusion protocol, ABC score = Assessment of Blood Consumption score, RSI = rapid sequence intubation, AKI = acute kidney injury, TEG = thromboelastogram, ROTEM = rotational thromboelastometry. The figure above is an internal resource from the St Luke’s University Hospital Network Trauma department.

1.1 Epidemiology of Unintentional Injury

In the United States, the most common reasons for presentation to the emergency department are injury and poisoning [3]. Unintentional injury alone accounts for upward of 97.9 million ED visits [4]. The two age groups that tend to experience the worst outcomes from unintentional injury include those younger than 46 years of age and the geriatric population [5, 6]. Although young patients tend to experience significantly higher morbid levels of trauma, minor trauma experienced by the elderly portends significant morbidity and mortality due to their increased frailty [5]. In patients younger than 46 years of age, trauma is the leading cause of death [5].

In the United States, unintentional injuries were the fourth leading cause of death in the year 2020 following heart disease, cancer, and COVID-19 [7]. Unintentional injuries include unintentional poisoning/overdose, motor vehicle accidents (MVA), unintentional drowning, and unintentional falls [7]. From 1999 to 2006, the unintentional injury rate rose by 1.9%. From 2014 to 2017, the rate of unintentional injury rose even further, with an annual growth rate of 6.8% [8]. When comparing the rate of age-adjusted death due to unintentional injury in 2020 to 2019, there was a 16.8% increase, largely due to a rise in deaths due to unintentional poisoning/overdose [7, 9]. In 2020 alone, unintentional accidents accounted for 200,955 deaths in the United States [4].

Unintentional injury accounts not only for a substantial proportion of annual ED visits and deaths, but it is also considered a significant contributor to the cost burden placed on the United States healthcare system. In 2019, treatment of these unintentional injuries resulted in $4.2 trillion in costs, with $327 billion being directly related to medical care and the remaining difference being attributable to costs associated with days lost of work and quality of life [9].

Given that unintentional injury continues to grow at a steady rate and provided that this subgroup of patients accounts for a large proportion of ED visits, adequate and timely management of this patient population is essential, with the main goal being to provide scientifically sound and cost-efficient medical care. Trauma anesthesiologists provide a unique subset of skills in the multidisciplinary treatment of trauma patients, especially when considering that with many of these patients present in a hemodynamically unstable state, there is usually minimal time to prepare the patient for major operations, and the ability to act swiftly and efficiently within a truncated time period is essential to improved patient outcomes.

2. Methods

A literature search was performed using Google search keywords of “trauma anesthesia” and “anesthesia in trauma.” The Advanced Trauma and Life Support (ATLS) literature and Trauma Quality Improvement Program (TQIP) literature were also searched for trauma anesthesia information. There were no de facto inclusion criteria and no specific time limitation or time frame to the articles; rather, the articles were included based on relevance or relation to anesthesia methods used for trauma patients.

3. Management in the Trauma Bay

3.1 Resuscitation of the Critically Ill Patient

Guidelines on trauma resuscitation have been implemented by several surgical societies in North America. In the United States, some of the more commonly followed guidelines have been published by the American College of Surgeons (ACS), the American Trauma Society (ATS), the American Association for the Surgery of Trauma (AAST), the Eastern Association for the Surgery of Trauma (EAST), and the Western Trauma Association (WTA) [10]. Resuscitation of a critically injured patient is essential as hemorrhage is the main cause of death within the “golden hour” on arrival at the trauma center. As defined in the guidelines provided by the ACS Trauma Quality Improvement Program (TQIP), massive transfusion protocol (MTP) is the supplementation of >10 units of red blood cells (RBCs) within 24 h [11]. In their guidelines, the ACS provides a set of criteria for initiating a MTP, the correct ratio of blood products to administer, and typical endpoints used to assess the adequacy of resuscitation efforts [11].

A MTP should be initiated if a critically ill trauma patient present in a persistent state of hemodynamic instability has active bleeding requiring a procedure, requires blood transfusion in the trauma bay, or has an Assessment of Blood Consumption (ABC) score greater than 2 [11] (Figure 2). The ABC score was developed by Cotton et al. and is widely accepted due to its ease of use as no lab tests are required and accuracy, with a sensitivity ranging between 75% and 90% and a specificity range from 67% to 88% [12, 13]. This clinically validated scoring tool is endorsed by the ACS [11].

Figure 2.

Components of the Assessment of Blood Consumption (ABC) score. Abbreviations: SBP = systolic blood pressure; HR = heart rate; FAST = focused abdominal sonogram for trauma; MTP = massive transfusion protocol. The figure presented above was created using data from the article by Cotton et al. [12].

When initiating a MTP, resuscitation should begin with blood products over crystalloid or colloid solutions [11]. A rapid transfuser and blood warmer should be utilized to administer RBCs and plasma, and you should stay at least 1 blood cooler ahead of the current transfusion until the MTP has been terminated [11]. A blood warmer should not be used for products such as platelets and cryoprecipitate. The ideal ratio for blood product resuscitation is a 1:1 or 1:2 ratio of plasma to RBCs [11]. For every 6 units of blood given, supplement 1 unit of platelets [11]. The use of cryoprecipitate and/or fibrinogen during MTP varies widely by institution, and there are no specific guidelines for the administration of cryoprecipitate until laboratory studies and adjunctive testing such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM) have been initiated [11].

When deciding on whether to stop the MTP, it is the role of the anesthesiologist in conjunction with the surgeon to decide if the resuscitation endpoints have been met. The assessment should include the physiological hemodynamic status and the anatomic control of the hemorrhage [11]. Endpoints to assess include hemoglobin >10 g/dL, prothrombin time < 18 seconds, partial thromboplastin time (aPTT) < 35 seconds, platelet count >150 × 10⁹, and fibrinogen levels >180 g/L [11]. Based on the previously mentioned endpoints, MTP can be downgraded or completely stopped, and more targeted blood component supplementation can be performed. MTP should also be withdrawn when it is determined that continued resuscitation would be futile [11].

3.2 Benefits of Massive Transfusion Protocols (MTP)

The use of MTPs in trauma centers has several benefits not only pertaining to patient outcomes but also in improving healthcare resource utilization and reducing healthcare costs. One of the most well-known trauma-based randomized clinical trials (RCTs) of the decade, the PROPPR trial, demonstrated that there was no difference in 24-h or 30-day mortality regardless of whether patients received a 1:1:1 or 1:1:2 ratio of plasma, platelets, and RBCs [14]. In general, the implementation of a MTP at major trauma centers is associated with a reduction in time to transfusion, a reduction in the volume of transfused blood products, and a reduction in overall mortality [15, 16]. In the retrospective cohort study conducted by O’Keeffe et al., the implementation of a MTP at a major trauma center resulted in the reduction of shipment times and a savings of $2270 per patient; however, there was no statistically significant difference in mortality [17]. Although MTPs provide several advantages, the type of blood product used for resuscitation, the protocol established by the institution, and the allocation of healthcare resources continue to be debated.

3.3 Crystalloids and Colloids

Besides blood component therapy and whole blood, crystalloids (normal saline, lactated Ringer’s, and isolyte) and colloids (albumin, dextrans, and modified starches) can also be used for volume resuscitation. Crystalloid solutions differ from colloids in that they are composed of smaller molecules than that of colloids; crystalloids are less expensive, and they are easier to use [18]. Colloids are composed of either synthetic or natural molecules and are more likely to induce allergic reactions. The modified starches are no longer used as they can cause coagulopathy as well as acute kidney injury [19]. Benefits of colloids such as albumin are increased oxygen transportation, myocardial contractility, and cardiac output [19]. No survival benefit has been demonstrated for colloids as opposed to crystalloids, and given the cost, crystalloids are preferred. The current ATLS guidelines recommend the use of a 1-L bolus of crystalloid for the initial management of hypotension found during the primary survey [2]. Normal saline is the most used crystalloid solution partially due to its approval of use with blood transfusions; however, a noteworthy potential side effect of normal saline is hyperchloremic metabolic acidosis when large volumes are administered [20]. Lactated Ringer’s solution is relatively contraindicated for blood transfusion because it contains calcium. The concern would be a reaction of the calcium with the citrate used to preserve the RBCs, leading to coagulation and clotting of the RBCs. Research has shown that there is no actual adverse effect of using lactated Ringer’s solution during a blood transfusion [20]. Lacted Ringer’s solution is also thought to promote the inflammatory response seen in shock and trauma states, increase bowel and liver apoptosis, and decrease serum calcium levels by sequestering calcium in the mitochondria [21]. Isolyte is a crystalloid solution with added acetate and gluconate as well as a lower chloride level. Its use is limited due to concerns for potential worsening organ failure as it has been shown to negatively impact peripheral vascular resistance and heart rate [20]. Crystalloids reduce oncotic pressure that can lead to pulmonary and peripheral edema; decreased tissue oxygen exchange, which delays wound healing; as well as exacerbated cell injury and dysfunction via worsening the extracellular calcium shifts seen in shock [21]. Although blood component therapy is the preferred solution for MTPs, colloid and crystalloid solutions may provide adequate volume resuscitation in certain patient populations. For example, normal saline is the preferred solution in patients with traumatic brain injury (TBI) [22]. On the other hand, it is best to avoid the use of colloids, such as albumin, in patients with TBI due to the concern for worsening cerebral pressure and the concomitant increase in mortality [22, 23]. Normal saline or lactated Ringer’s are also the treatment of choice for post-traumatic acute kidney injury [20].

3.4 Thromboelastography (TEG) and Rotational Thromboelastometry (ROTEM)

There has been an increase in the number of United States trauma centers that have implemented TEG and ROTEM into their MTP protocols. They both assess clot formation, degradation, and strength but differ in the mechanics behind the rotational mechanism that generates various coagulation parameters. In TEG, the cylinder that contains the blood sample is what oscillates, and a pin that is suspended in the blood sample is stationary [24]. ROTEM utilizes mechanics opposite to TEG, with the blood sample cylinder being stationary and the pin oscillating [24]. The benefit of using TEG and ROTEM in the management of massive hemorrhage is that they rapidly and readily predict various coagulopathies within 15 min to help guide resuscitation efforts [25]. A sample TEG image is presented in Figure 3 along with a description of the various parameters investigated and the recommended treatment based on the results for each parameter. Provided the numerous advantages of incorporating TEG and ROTEM into standard trauma management, more targeted resuscitation efforts can potentially improve morbidity and mortality (Figure 4) [25] . More recent studies have begun to investigate the use of guided resuscitation compared to the standard fixed ratio of platelets, packed RBCs, and plasma. Of the currently available studies regarding the use of TEG or ROTEM for guided resuscitation, the only available RCT, conducted by Gonzales et al., found that guided resuscitation with TEG improves survival while decreasing the number of units of plasma and platelets transfused [29].

Figure 3.

Sample image of TEG with the associated parameters and recommended treatment. R-time = reaction time, MA = max amplitude, FFP = fresh frozen plasma, LY30 = percentage lysis after 30 min of MA, Cryo = cryoprecipitate. The image presented above was extracted from the article by Pietri et al. and was slightly modified for simplification [26]. The normal ranges in the bottom portion of the figure were obtained from the article written by Cameron et al. [27]. The treatment approaches for each of the abnormal parameters presented in the bottom half of the figure were discussed in the article written by Johansson et al. [28].

Figure 4.

Sample pathologic TEG waveforms. The image presented above was extracted from the article by Whiting and DiNardo [24].

3.5 Antifibrinolytics

In the process of hemostasis, a blood clot is formed when fibrinogen is converted to fibrin by thrombin-mediated proteolytic cleavage, with the end result being fibrils that mature to produce a clot that inhibits bleeding [30]. Typically, the clot is broken down by the protein plasminogen after it is converted into the active form, plasmin [31]. Antifibrinolytic agents, such as tranexamic acid (TXA) and amino caproic acid, are synthetic lysine derivatives that competitively inhibit the lysine binding sites on plasminogen, blocking the conversion of plasminogen to plasmin [32]. By doing so, these antifibrinolytic agents inhibit the proteolytic action of plasmin on the fibrin clot, thereby prolonging the life of the clot plug.

Aprotinin is an antifibrinolytic that is not currently available in the United States, and similar to TXA, it is a protease inhibitor. However, unlike TXA, aprotinin differs because it complexes with active serine residues on various proteases [33]. Aprotinin acts reversibly on trypsin, kallikrein, plasmin, and elastase [33]. Of all the available antifibrinolytics, aprotinin is the most potent pharmacological agent available. While this is the most potent agent available, it is seldom used secondary to its propensity to cause renal side effects [34].

Although the role of antifibrinolytics in trauma is not heavily established, more recent studies, such as the CRASH-2 study, have demonstrated that drugs like TXA may play a role in improving outcomes in bleeding trauma patients [35]. In their randomized control trial, more than 270 hospitals from over 40 countries were included, and the results of the study demonstrated that the application of TXA reduces all-cause mortality and the incidence of bleeding in patients experiencing traumatic injuries [35]. Current usage recommendations from TQIP indicate antifibrinolytic agents can be used empirically or in response to point of care testing showing increased fibrinolytic activity [11]. The TQIP guidelines for the dosing of TXA are more specific. Patients that are actively bleeding and present within 3 h of injury should be administered 1 g infused intravenously over a timeframe of 10 min, followed by another 1 g infusion over an 8 h period [11].

3.6 Vasopressors and Inotropes

Provided that the acidosis arm of the lethal triad is to some degree due to end-organ malperfusion, many consider the use of vasopressors in massive hemorrhage ill-advised [36]. The pathophysiology behind systemic vascular resistance is that in the presence of massive intravascular volume loss, compensatory mechanisms induce vasoconstriction, and adding a vasopressor agent on top of the neuroendocrine response will only exacerbate end-organ malperfusion [36]. Of the vasopressor agents commercially available, the most commonly used vasopressors include norepinephrine, vasopressin, and phenylephrine (Figure 5). A common side effect of vasopressors is arrhythmia. They also can cause varying degrees of tissue necrosis in the setting of extravasation. Reflex bradycardia, decreased cardiac output, and ischemia (peripheral, mesenteric, renal, or myocardial) are associated with phenylephrine. Vasopressin can cause mesenteric ischemia, chest pain, coronary artery constriction or myocardial infarction, bronchial constriction, and hyponatremia [38]. In addition, norepinephrine use can also result in bradycardia and dysrhythmia.

Figure 5.

Adjunct pharmacologic agents used in trauma resuscitation. sGC = soluble guanylyl cyclase, NO = nitric oxide, AT-R1 = angiotensin receptor 1, AT-R2 = angiotensin receptor 2, CO = cardiac output, MT = massive transfusion, N/A = not applicable. The mechanism of action and uses of the agents in the figure were discussed in the article written by Levy et al [37].

More recently, controversy regarding the use of vasopressors in trauma has led to a valid argument that based on normal pathophysiological mechanisms alone, permissive hypotension would seem detrimental to the patient given the prolonged period of end-organ malperfusion. On the other hand, volume overload has been correlated with worse clinical outcomes, thereby providing a potential reason for vasopressors when the ideal middle ground is the ultimate goal for adequate perfusion [36]. An appropriate balance of volume replenishment and vascular resistance is essential to establishing homeostasis, and in select patients, vasopressors may be beneficial. In general, blood component therapy is the first line treatment for massive hemorrhage; however, in the presence of persistent hypovolemia and vasoplegic shock, vasopressors and inotropes may provide the necessary increase in vascular tone [39]. Larger prospective RCTs are currently being performed, and although vasopressors are typically frowned upon, patients with concomitant medical comorbidities such as cardiac dysfunction may benefit from inotropic agents like dobutamine, dopamine, and epinephrine that stimulate cardiac contractility [39]. Inotropes exhibit many of the same adverse effects that vasopressors do, namely, hypotension, dysrhythmias, myocardial infarction, and tachycardia. Additionally, the use of these agents can cause angina. Dopamine exhibits the most severe form of tissue necrosis (necrosis without extravasation and gangrene with extravasation) [38]. Epinephrine can cause anxiety, pulmonary edema, and tachycardia [38]. Vasopressors, inotropes, and leusitropes should be administered through a central venous access as prolonged delivery using peripheral IVs can exacerbate side effects.

3.7 Other pharmacological agents used in trauma

Along with vasopressors and inotropes, other pharmaceutical agents used during the management of massive hemorrhage and vasoplegia include hydrocortisone, leusitropic agents such as milrinone, and electrolyte replenishment. Hydrocortisone is beneficial for the management of hypotensive patients that have an impaired hypothalamic-pituitary-adrenal (HPA) axis. In cases where the endocrine function of the adrenal gland is in question, supplementation with hydrocortisone has been shown to reduce vasopressor requirements, although the outcomes following hydrocortisone administration are less clear [20]. Replenishment and monitoring of electrolytes is another important aspect of resuscitation efforts. Massive transfusion can lead to derangements in calcium, magnesium, and potassium [40]. Citrate that is incorporated into blood products for storage purposes can lead to calcium and magnesium chelation, eventually inducing hypocalcemia and hypomagnesemia, which can manifest as prolonged hypotension as well as a prolonged QT interval [20, 40]. This occurs with transfusion rates of >1 unit of RBCs/5 min or in patients with hepatic dysfunction [20]. Both hyperkalemia and hypokalemia can occur, with hyperkalemia being more common. Over time, the levels of potassium in stored RBCs increase, leading to hyperkalemia with massive transfusions. The mechanism of hypokalemia is multifactorial. Increased aldosterone and antidiuretic hormone release, chelation from citrate in stored RBCs, catecholamines, and activity of the RBC membrane ATPase pump all contribute to decreased potassium levels following a massive transfusion of blood products [20].

There are also experimental uses of agents like methylene blue, angiotensin II, or selective b-blockers such as esmolol [37]. While primarily used as a contrast agent, methylene blue (MB) has shown utility as an adjunctive treatment for severe vasoplegia in cardiac surgery and septic shock [41]. The mechanism of action involves direct inhibition of nitric oxide as well as the inhibition of soluble guanylyl cyclase (sGC), which is a peptide (classify) that increases cyclic guanosine monophosphate (c-GMP) [41, 42]. cGMP then causes relaxation of blood vessels. When given early in vasoplegia, MB helps increase mean arterial pressure (MAP) and improve cardiac function [41, 42]. Angiotensin II is another medication used in conjunction with vasopressors to treat septic shock. As demonstrated in the ATHOS studies, the use of angiotensin II leads to improvement in hypotension and catecholamine sparing [43, 44]. The use of esmolol has been shown on meta-analysis to improve survival, prevent myocardial depression by improving myocardial oxygen utilization, and decrease heart rate and troponin [45]. However, a recent pilot trial by Levy et al. has demonstrated that the use of esmolol within 6–12 h following vasopressor use results in increased risk of hypotension and diminished cardiac index [46].

Lastly, factor VIIa had been proposed as an additional therapeutic agent to help alleviate massive hemorrhage. Factor VIIa acts by binding to tissue factor that is exposed after endothelial damage, and by increasing the formation of thrombin, a fibrin clot is created [20]. Unfortunately, the use of Factor VIIa has not been shown to improve mortality and is not recommended for routine use in massive transfusion situations; however, more prospective RCTs are needed to definitively establish the role Factor VIIa may play in the future management of hemorrhagic trauma [20].

3.8 Current thinking on Massive Hemorrhage Resuscitation

More recently, traumatologists have circled back to the principle of whole blood resuscitation. Although whole blood resuscitation is used heavily in the military setting, significant barriers to more widespread adoption in the civilian setting are due to the portrayed risks of higher infections and immunological complications. Other drawbacks include a lack of clotting factors in whole blood, as well as increased potassium, hydrogen ions, and ammonia within whole blood.

Historically, whole blood was the principal resuscitation product during World War I, World War II, and the Korean War [47]. Although blood component therapy is now the most used method for civilian trauma resuscitation, there was a paucity of evidence to support the shift from whole blood to component therapy [47]. More recent data has suggested that whole blood transfusion provides civilian trauma patients with improved resuscitation status when compared to component therapies [47]. Whole blood requires significantly less volume versus component resuscitation (450–600 mL vs. 650 mL) and comes with a physiologic amount of platelets. The platelets in whole blood have a longer half-life than isolated platelets alone (21–35 days vs. 5 days), allowing for the expansion or preservation of platelet supplies. Whole blood is not recommended for use in rapid transfusers as the transfuser causes platelet destruction, though the decrease in platelets does not result in diminished platelet function or clot strength [47].

Individual components such as red blood cells, fresh frozen plasma, and cryoprecipitate are not without risk. Fresh frozen plasma has one of the highest risk profiles and can cause allergic reactions, transfusion-related acute lung injury (TRALI), fluid overload, and increased risk of infection.

Although the ability to collect low titer group O whole blood is much more difficult given that in certain regions of the United States, only 3% of the blood donor population meets the specified criteria, a more intuitive approach has been to test previously unrefutable medical principles [48]. Recent literature has suggested that the use of RhD-positive blood products results in a low risk of hemolytic disease of the newborn in females of childbearing age, a risk that is estimated to be only from 0.3% to 6.5% [48]. ABO incompatibility has also been further analyzed, and retrospective analyses have demonstrated no difference in mortality between those administered ABO-identical versus ABO-incompatible blood products [48]. By increasing the blood pool donor options, healthcare resources can become more accessible, and the likelihood of blood product shortages can be decreased.

3.9 Bridging the gap in modern resuscitation practices

Despite widespread support for whole blood resuscitation, there is still room for improvement in the current standards of care, including prehospital blood component administration and uniformity in MTPs.

Prehospital administration of plasma has been demonstrated to improve 30-day mortality in the PAMPer clinical trial, and post hoc analysis of the PAMPer and COMBAT clinical trials demonstrated a survival benefit with prehospital plasma administration when transport times exceeded 20 minutes [49, 50]. Even in light of strong evidence suggesting a benefit to prehospital administration of blood products, an analysis of the National Emergency Medical Services Information System (NEMSIS) 2019 dataset found that the use of prehospital blood transfusion for trauma resuscitation was extremely low [51].

Although the use of MTPs in trauma centers is the standard of care, the method for initiating the MTP and the actual format of the MTP vary between different institutions across the country. The ACS TQIP makes a note in their MTP guidelines that the creation of a MTP should “be developed by a multi-disciplinary committee” consisting of the blood bank, emergency medicine, anesthesia, and trauma services [11]. MTPs vary depending on the committees that form them, so there are discrepancies in their activation and constructs, leading to differences in patient outcomes. Etchill et al. found in their online survey conducted through the AAST that 7% of participants used a validated scoring system for MTP initiation, 9% consistently used TEG or ROTEM in their MTP, and the number of blood units readily available for use varied significantly among different institutions [52]. Given the major inconsistencies present in our healthcare system, there is a dire need for more uniform MTPs. However, despite these inconsistencies, the implementation of MTPs over the past decade has resulted in a reduction in mortality by 45%, a drop in median RBC units transfused from 12 to 4, and an increase in surviving patients being discharged back to their homes [53].

3.10 Operative vs. nonoperative management

The decision-making process in terms of operative or interventional management as opposed to nonoperative management of traumatic injuries is multifactorial and depends on the mechanism of injury, the structures that are injured, and the stability of the patient. Indications for prompt operative management include active bleeding/hemodynamic instability, aerodigestive injury, injury to major- or moderate-sized blood vessels, pericardial tamponade, positive FAST, blunt or penetrating abdominal trauma with peritonitis, expanding hematomas, and significant solid organ or internal injury that will require repair (i.e., grade V solid organ injuries or bowel perforations) [54]. Vascular injury such as partial or complete transection of blood vessels can occur from blunt or penetrating trauma via shearing or blast forces [55, 56]. Partial transection of blood vessels is more severe than complete transection being that a completely transected vessel is able contract and thus bleed less [56]. Intimal flaps with secondary thrombosis, pseudoaneurysms, and contusions can also occur.

Penetrating trauma involves kinetic energy and cavitation force leading to tissue injury and lacerations of solid or hollow organs as well as blood vessels. Blunt trauma (MVA, automobile vs. pedestrian accident, and falls from height) involves shearing, reactive forces in deceleration, rotational, and compressive forces. This tends to cause fractures, diffuse tissue injuries, compression and/or laceration of solid organs, perforation of hollow viscus organs, pneumothorax, and bronchial injury [55]. One of the most pertinent differences between blunt and penetrating trauma involves resuscitative thoracotomy. This procedure is not indicated in patients suffering from blunt trauma given the survival rate of 1% and the high incidence of significant neurologic morbidity in these survivors [54]. Patients with penetrating trauma to the chest causing cardiac injuries have a 35% survival rate provided they showed signs of life upon arrival to the emergency department or trauma bay [54].

4. Intraoperative care

4.1 General principles

After the decision has been made to proceed with operative intervention, there are a few general principles to consider from the anesthesiologist’s perspective regarding the medical care of trauma patients. The patient must receive adequate resuscitation and maintenance fluids, the medical team must be able to accurately assess the patient for hemodynamic stability and physiological endpoints, and the anticipated supplies must be readily available as not to delay the troubleshooting of common complications.

Similar to the primary survey conducted at the beginning of the trauma patient’s arrival, it is important to consider mechanical and pharmacological interventions for the airway, the pulmonary system, and the cardiovascular system.

For maintenance of the airway and pulmonary system, consider having the following supplies readily available: a laryngeal mask airway (LMA), various sized endotracheal tubes, Macintosh and Miller intubation blades, a videoscope, a bag valve mask, fiberoptic scopes, and oral and nasal airway systems.

For proper management of the cardiovascular system, utilize a rapid infuser and fluid warmer for resuscitation, consider placement of an arterial line and/or central line, ensure adequate peripheral access with two large-bore IVs (14G or 16G), consider the use of vasopressors, and place all necessary monitors (e.g., bispectral index monitor (BIM), pulse oximetry, a blood pressure cuff, 5 lead electrocardiogram (EKG), and core temperature monitor). Also, consider the maintenance of the patient’s body temperature using a Bair hugger normothermia system and assess the operating room temperature in order to prevent hypothermia.

4.2 Current guidelines for intraoperative anesthesia care of trauma patients

Regarding intraoperative care, it is critical to be informed of the most recent literature pertaining to induction and maintenance goals, lung protective ventilation, and maintenance of normothermia.

The main goal of induction and maintenance is to maintain hemodynamic stability. If the patient is hemodynamically unstable, continue to resuscitate the patient preceding and during induction [57]. Adequate intravenous access is critical for timely resuscitation. If invasive access is needed, do not hesitate to proceed. It is best to ask the trauma team to maintain the patient’s arms in an abducted position so that invasive access can be easily obtained without further delaying the surgery [57]. Given the time constraints, if possible, preoxygenate the patient with four vital capacity breaths prior to intubation. In certain scenarios, the patient may be obtunded. If so, proceed with apneic oxygenation [57]. When inducing, consideration should be given to the dose of the induction agent as trauma patients may require a much lower dose. Of the typical induction agents utilized, the most commonly used include ketamine, etomidate, and propofol [57].

Ketamine provides the ability to maintain systemic vascular resistance and spontaneous respirations; however, it is a cardiac depressant and should only be given at a dose of 1 mg/kg [57]. This makes ketamine an ideal choice for patients who have difficult airways. Dissociative delirium and increased secretions are well-known side effects. Etomidate is also used to maintain hemodynamic stability but can cause myoclonus, adrenal suppression, and postoperative nausea and vomiting [57]. Typical dosing is from 0.2 to 0.3 mg/kg. Propofol, although preferred by many due to its fast onset, has a significantly higher risk of decreasing systemic vascular resistance. Therefore, many anesthesiologists administer a vasopressor concomitantly in order to counteract the decrease in systemic vascular resistance [57]. A multicenter retrospective trial published by Leede et al. in 2021 showed no significant difference in systolic blood pressure for rapid sequence induction between these three agents [58]. Baekgaard et al. conducted a systematic review of the literature and found that there were no differences in transfusion or 30-day mortality rates between the ketamine, etomidate, and propofol [59]. As such, no specific recommendation can be made regarding the use of one of these agents over the other.

Aspiration is a significant risk to consider when inducing trauma patients as we often have to assume that they do not fall within the nil per os guidelines. Patient may be obtunded, may have received opioids that delay gastric emptying, and may have eaten recently. When performing rapid sequence intubation, it is advised to administer succinylcholine 1 mg/kg or rocuronium 1.2 mg/kg [57]. The onset of both previously mentioned pharmaceuticals is comparable, although rocuronium has a longer duration of action. Potential side effects of succinylcholine include myalgias, increased intraocular pressure, increased intracranial pressure, and hyperkalemia [57]. Succinylcholine should be avoided in patients with spinal cord or burn-related injuries and prolonged immobilization and pediatric patients [57].

Special consideration must be given to patients who present in a C-collar [57]. Due to the potential for injury, first establish if the front portion of the collar can be removed. The trauma team should be positioned so that one team member stabilizes the shoulders, another holds the patient’s head, and the trauma anesthesiologist performs the intubation [57]. When deciding the intubation method with which to proceed, randomized control trials demonstrated no difference in C-spine manipulation when direct laryngoscopy or videoscope was performed [60].

When ventilating the patient, it is best to incorporate lung protective ventilation strategies to reduce iatrogenically induced pulmonary injury [61]. Tidal volumes should be set to 6–8 ml/kg, with positive end-expiratory pressure (PEEP) initially set to 5 and titrated accordingly based on individual patient characteristics [61, 62]. In general, patient characteristics that portend the greatest risk to postoperative pulmonary complications include age greater than 50 years old, body mass index greater than 40 kg/m², American Society of Anesthesiology (ASA) grade greater than 2, obstructive sleep apnea, preoperative anemia, preoperative hypoxemia, emergency or urgent surgery, ventilation duration exceeding 2 h, and intraoperative factors such as hemodynamic impairment and low oxyhemoglobin saturation [61].

Normothermia is an important physiologic parameter to maintain. If the patient becomes hypothermic, which is defined as a core body temperature of less than 35°C, the hypothermia cascades into a state of coagulopathy and metabolic acidosis. This lethal triad prolongs hemorrhage in surgically uncontrolled bleeding, preventing tissue regeneration and physiologic recovery [63]. Hypothermia can be classified even further into mild (32–35°C), moderate (28–32°C), and severe (<28°C) stages [63]. Hypothermia is a well-known predictor of worse outcomes in trauma and TBI patients and is associated with higher rates of mortality, greater blood transfusion requirements, and prolonged stays in both the hospital and ICU [64]. In order to proactively prevent hypothermia, strategies to maintain normothermia include keeping the operating room temperature elevated and utilizing an underbody, upper body, and lower body Bair hugger to heat the air immediately encompassing the body of the patient [65].

4.3 What is awareness, and how is it prevented?

In the realm of Anesthesia, awareness is the explicit recall of sensory events during the procedure. Patients undergoing obstetric procedures, cardiac surgery, or major trauma surgery are at an increased risk of intraoperative awareness. In cardiac surgery, the incidence varies between 1.1 and 1.5%, whereas in major trauma cases, the incidence may range from 11 to 43%. Three factors that contribute to the increased occurrence of intraoperative awareness are light use of anesthesia, resistance to anesthetics, and inadequate delivery of the anesthetic secondary to a machine malfunction or misuse of the anesthetic machinery. Light anesthesia is considered to be the most likely culprit of intraoperative awareness. Given the dose of the anesthetic is limited in trauma surgery due to the higher likelihood of hemodynamic instability with higher doses, the purposeful light anesthesia predisposes trauma patients to an increased likelihood of experiencing intraoperative awareness.

Fortunately, several preventative measures can be taken preoperatively and intraoperatively to reduce the likelihood of awareness. Consideration should be given regarding the use of a premedication drug such as benzodiazepines or scopolamine [66]. The use of amnestic drugs should be given stronger consideration if the patient will be given light anesthesia for a valid reason, such as a hemodynamically unstable trauma patient undergoing major surgery [66]. It is best to avoid muscle paralysis so that voluntary responses can still be observed [66]. Provide a volatile agent with a minimum alveolar concentration (MAC) of 0.6 or more, and utilize a combination of agents, such as opioids and nitric oxide, to aid induction of unconsciousness, noting that the use of opioids or nitrous oxide alone is not enough to produce unconsciousness. Knowing that machine misuse and malfunction is one of the three main causes of intraoperative awareness, continuously check the anesthesia machinery [66]. If there is ample time, it is ideal to talk to the patient about auditory options to block operative noises, such as the use of earphones [66]. Lastly, it is important to make the operative team aware of the phenomena, as a better understanding of the phenomena can allow the team to make the necessary changes to preoperative preparation and intraoperative management of the anesthetic settings [66]. Currently, bispectral index monitoring (BIS) is utilized to measure the patient’s anesthetic depth. The consciousness level of the patient is measured by interpreting electroencephalographic signals, with the data converted into a score and a value between 40 and 60 being the current standard to prevent awareness [67]. There remains much controversy in the reliability of the BIS monitor; however, at this time, this is the only technology available in the United States that can aid in monitoring awareness.

4.4 Damage Control Surgery

When a trauma patient undergoes operative intervention to control massive hemorrhage, it is essential to establish the nature of the procedure and whether the end goal of the index procedure is to definitively correct traumatic injuries or to stabilize the patient so that a definitive operation can take place at a later date. The latter is referred to as damage control surgery (DCS), which is the approach utilized to control hemorrhage, control or reduce contamination, and re-establish physiologic homeostasis [20].

During damage control surgery, specifically for intrabdominal trauma or bleeding, a laparotomy to stop bleeding and control peritoneal contamination is performed. A staged repair then follows the initial laparotomy once adequate ICU resuscitation has been achieved. As the patient undergoes operative intervention, blood component therapy and resuscitation are aggressively provided. Originally an approach only utilized by military medicine, DCS is now becoming more heavily utilized in the civilian population [20].

It is important to acknowledge that unlike typical resuscitation efforts, DCS focuses on preventing the exacerbation of the lethal triad: hypercoagulability, hypothermia, and acidosis [20]. The DCS approach implements blood component resuscitation earlier and more aggressively, utilizes hypotensive resuscitation, and corrects for coagulopathy during the initial resuscitation measures [68].

Hypotensive resuscitation, also referred to as permissive hypotension, is unlike standard large-volume resuscitation in that a lesser volume of fluid and blood product is used so that the patient is maintained at below-normal blood pressure during the operative intervention [68]. By maintaining a mean arterial pressure (MAP) of 50 mmHg, as done in permissive hypotension, rather than a MAP of 65 mmHg, permissive hypotension has been shown to decrease postoperative coagulopathy and death [69]. Interestingly, among the randomized control trials that have investigated hypotensive resuscitation, outcomes following hypotensive resuscitation were not worse than the standard resuscitation measures [68]. Although mortality did not significantly differ in 4 of the 5 more well-known randomized control trials, the RCT conducted by Bickell et al. found that patients given hypotensive resuscitation had improved survival rates (70% vs. 62%, p = 0.04) [68, 70]. The exception to permissive hypotension in DCS are patients with neurologic trauma such as traumatic brain injury or spinal cord injury. Recommendations are to maintain a MAP of 65 mmHg or a systolic blood pressure of 90–100 mmHg to maintain adequate cerebral perfusion pressure ranging from 60 to 70 mmHg [68, 71].

Although patients that undergo DCS are at an increased risk of morbidity, it is still commonly performed despite a paucity of evidence to support its widespread use. In the systematic review conducted by Roberts et al., a total of 39 studies were included in their review, and overall, only 10 of the 59 indications for DCS had strong evidence for validity [72]. Given that the indications for DCS are less well-established, it is critical to develop a more uniform indication system. Future directions include establishing a more definitive scoring system such as the DECIDE score that was developed by Urushibata et al. using the Japan Trauma Data Bank. However, the sensitivity and specificity of their scoring system were only 64.8% and 70.0%, respectively [73]. More granular, prospectively validated scoring systems for civilian trauma could provide the solution to improve mortality while predisposing fewer patients to severe morbidity.

4.5 Considerations for postoperative care

After completing the index trauma procedure, several considerations must be given as to where the patient will be transferred and whether the patient is at high risk for unplanned admission to the ICU if transferred from the postanesthesia care unit to the floor. Part of the decision will be established before the index procedure is completed, as in the case of damage control surgery where the patient will be transported to the ICU for further resuscitation, electrolyte management, acidosis correction, and assessment of coagulopathy. In other cases, the patient’s index procedure may be definitive, and ICU care is unnecessary. Transfer to the ICU still requires significant anesthesia involvement, particularly with intubated patients. There are no specific recommendations regarding propofol versus dexmedetomidine or benzodiazepines with narcotic titrations. Rather, sedation for these patients should be individualized based on their clinical pathology and condition [71]. Benzodiazepines, while possessing a stable hemodynamic profile, should be used with significant caution in the elderly and in patients with renal failure [74]. There is also a risk of ICU delirium with prolonged use of benzodiazepines. Propofol’s vasodilatory affects seen with larger doses can be poorly tolerated by unstable patients [74]. Dexmedetomidine is a versatile medication as it can be used for sedation in intubated patients as well as analgesia in non-intubated patients. However, dexmedetomidine can cause hypotension, bradycardia, and heart block (if overdosed).

Within the ICU, resuscitation efforts become more goal-directed. ROTEM or TEG is used to monitor and guide the hematologic resuscitation, while laboratory studies guide electrolyte repletion and treatment of acid-base derangements. Once hemorrhage has been definitively addressed via surgery or interventional procedure, permissive hypotension can be discontinued. There is no absolute MAP or SBP goal, but resuscitation goals are aimed at a return to a more normotensive state to facilitate organ perfusion. Crystalloid use in the postoperative phase is predominantly focused on decreasing the incidence of post-traumatic acute kidney injury (AKI). Fluids are titrated to produce a urine output of 1–2 mL/kg/h [20]. A tertiary examination of the patient should also be completed in the postoperative period to assess for any missed injuries.

A concrete understanding of the patient’s risk factors for unplanned ICU admission is essential to provide adequate care and anticipate potential barriers to timely medical management and discharge. In the systematic review conducted by Onwochei et al., independent risk factors for unplanned ICU admission included age, anemia, ASA physical status, body mass index (BMI), comorbidity burden, emergency surgery, high-risk surgery, male sex, obstructive sleep apnea, increased blood loss, and operative duration [75]. Out of the previously described risk factors, the most common in the United States included age, body mass index, comorbidity extent, and emergency surgery [75]. In conjunction with the previously mentioned risk factors, it is important to have a multidisciplinary discussion, and healthcare resource allocation should be taken into account when deciding on the most feasible medical ward for the patient’s postoperative medical care.

5. Discussion

The future of trauma resuscitation involves technologies and methods geared toward better addressing the supply of blood products and novel methods of controlling hemorrhage. Resuscitative endovascular balloon occlusion of the aorta (REBOA, seen in Figure 6) has highly specific indications as a temporizing measure to control bleeding from non-compressible torso injuries (disruption of the axial torso vessels, solid organ injuries, pulmonary parenchymal injuries, and so on) as well as hemorrhage below the diaphragm [77]. The thoracoabdominal aorta is accessed via femoral catheterization, and a balloon is inflated in aortic zone 1 (the origin of the left subclavian artery to the celiac artery) or aortic zone 3 (from the lowest renal artery to the aortic bifurcation) depending on the injuries present. Zone 2 is from the celiac trunk to the lowest renal artery. Occlusion at this zone has no current indications and is technically challenging to achieve in an emergent situation as it requires contrast to accurately delineate the anatomy. This technique can be used for a maximum of 30–90 min depending on the injury zone; however, REBOA can only be attempted if there is capability to provide definitive care at the facility that performs the REBOA [78, 79]. It is contraindicated in major thoracic hemorrhage and pericardial tamponade, both of which are better addressed via resuscitative thoracotomy. Adverse effects of REBOA include spinal cord injury, increased mortality with >30 min use in zone 1, aortoiliac injury, balloon rupture, and ischemia reperfusion injuries (acute kidney injury and multisystem organ failure). There are also complications that can occur at the level of access such as femoral artery dissection, pseudoaneurysm, or hematoma [78].

Figure 6.

REBOA catheter. The image presented above was extracted from the article by McGonigal [76].

Advances in lyophilization (freeze drying) techniques now allow for the destruction of pathogens such as hepatitis and HIV and have led to a resurgence in the development and use of lyophilized blood components [80]. Spray-dried plasma has been shown to be both safe and efficacious and is available in ABO universal forms [81]. Currently, these products are being used in South Africa and Europe with some prehospital use in Europe as well. Formulation and development are underway for the United States. The shelf-life ranges from 15 months to 2 years (as opposed to 12 months for FFP), and there is one formulation that can be stored at room temperature [81]. Reconstitution of the products occurs in minutes, making these products a viable solution for current blood product supply issues. Lyophilized platelets have a short duration of action and circulation (4–6 h) with only partial functionality in comparison to pooled platelets. Further progress is also necessary in terms of developing a working model of freeze-dried RBCs. Existing formulations sustain significant functional impairment of the cells in addition to substantial RBC death during reconstitution [81, 82]. Cryopreservation of RBCs requires −80°C freezers with a preparation and washing time of approximately 1.5 h, making this method impractical for use in trauma situations [82].

Another methodology under ongoing investigation is the use of induced hypothermia for body and neurologic preservation, also called emergency preservation and resuscitation (EPR) [80]. Hypothermia to 10°C is rapidly induced via resuscitative thoracotomy and maintained for 60 min. A nonrandomized clinical trial of EPR called the EPR-CAT trial is underway with a scheduled conclusion in December of 2023 [83]. There is also the possibility of prehospital induction of hypothermia with portable equipment [80].

6. Conclusion

As one of the leading causes of emergency department visits and death in the United States, trauma is a field that is high-acuity and requires multidisciplinary teamwork. Although guidelines are constantly changing, the general principles of the primary and secondary surveys remain widely accepted for initial evaluation of the patient’s injuries. It is during these initial assessments that decisions regarding adequate resuscitative interventions and need for operative intervention are made. Trauma patients needing emergent operative intervention tend to be in critical condition, so the anesthesia provider’s expertise in areas such as resuscitation, intubation, induction, and awareness is crucial in making immediate decisions. Anesthesia providers also have a role in formulating standardized trauma-related protocols that can result in a widespread improvement in patient outcomes. Ultimately, the focus of every trauma activation is the patient outcome, which hinges on the preparation and contribution from each specialty in the trauma team. Anesthesia providers have an integral role, particularly in operative trauma cases, and staying updated in current trauma activation guidelines is imperative to appropriately resuscitate trauma patients and maintain hemodynamic stability in the operating room.