Chapter 36

Trauma Anesthesia

The views expressed in this chapter are those of the author, and do not reflect the official policy or position of the Uniformed Services University of the Health Sciences, the Department of Defense, or the United States government.

Etiology of Traumatic Injury

Traumatic injury is a unique condition. Unlike other diseases that have a biologic basis, trauma is a result of an external force that ultimately disrupts normal structure and function of the body. In most situations, the initial cause of injury is not a result of genetics or environmental exposure, but circumstance and misfortune. Traumatic injury is a disease of human behavior. Although improvements to automobile safety and development of public policy have successfully reduced the annual number of traumatic injuries caused by motor vehicle collisions (MVCs), falls, and firearms by nearly a third, traumatic injury still remains the leading cause of death for Americans under the age of 40.¹ This translates to 180,000 deaths in the United States alone, or more simply put, one death every 3 minutes.² The mortality of injury is striking; however, it represents only a small fraction of those affected by trauma.

There is no absolute number that can precisely quantify the toll and cost of trauma. Although figures vary by author, it has been estimated that the cost for medical care and lost productivity in the United States was more than $400 billion in 2005—of that amount, nearly $100 billion resulted from MVC alone.1,3 These figures, while staggering, account only for expenses and do not account for the burden that injury places on utilization of scarce medical resources.² Mortality is only the tip of the iceberg. Trauma accounts for nearly 30 million emergency care treatments per year in the United States, a tenth of which will require hospital admission and possibly surgical intervention.^2,3,4

Some progress in improving these statistics has clearly been made in the United States, but prevention and treatment of trauma outside of the United States has lagged. Globally, injury is increasing in developing nations.⁵ The World Health Organization (WHO) demonstrated in the year 2000 that 1.6 million people died as a result of trauma.⁶ Although half of these deaths were a result of suicide, the remainder were due to homicide or combat-related violence.⁶ The WHO estimates that injury will be the leading cause of death worldwide by 2020.¹ If the prediction is true, the morbidity and mortality of injury—a manmade illness—will far surpass that of infectious diseases. This change will represent a true paradigm shift in global health.

Coordinated Management of Care

The acute management of a trauma patient presents unusual challenges. In many instances, trauma warrants immediate surgical intervention. Mechanism of action, multisystem injury, and preexisting medical conditions create complexities that are unusual when compared with routine perioperative management.

Time is a luxury and often a scarce resource when managing the critically unstable trauma patient. In many cases, surgical care cannot be postponed to acquire a battery of preoperative exams. Patient medical history may be unknown or incomplete at best. Patients are often unable to provide competent medical history. The patient’s inability to provide a history may be a result of the injury or of concurrent acute intoxication. Regardless of the cause, this gap in information leaves many preoperative questions unanswered. Although every attempt should be made to ascertain a thorough history, it should not be done at the expense of delays in care.

Management of trauma in the United States has historically occurred at the municipal level, between the emergency medical system (EMS) and community hospital. Coordination between these stakeholders has varied widely across the United States, resulting in a range of outcomes. The evolution of modern trauma systems has challenged the community level care model—integrating prehospital, tertiary care providers, and public policy in the effort to direct trauma care—a multivariate phenomenon.

The implementation of the modern trauma system has resulted in significant improvement in patient outcomes. Pioneering examples of this paradigm shift can be seen throughout many cities in the United States and around the world; the impact of this shift on patient morbidity and mortality was formally recognized in 1998. The Skamania Symposium (Skamania Lodge, Oregon; Academic Symposium to Evaluate Evidence Regarding the Efficacy of Trauma Systems) was the first academic group to evaluate the efficacy of a trauma system.⁷ This group systematically evaluated published data to determine the impact of trauma systems. Their findings were that care in a trauma center (versus a nontrauma center) was associated with fewer unnecessary deaths and less disability.^7,8 These findings have been supported by several other groups in the United States. Risk of death is considerably lower among patients who require early operative intervention if they are treated at a designated Level I trauma center. These outcomes are not a result of more rapid assessment and intervention alone, and emphasize the complex factors that contribute to the survival benefit of trauma center care. Studies in the United States show that mature, statewide trauma systems dramatically reduce unnecessary deaths from greater than 30% to less than 5%, compared with nontrauma system care.^9–12

Organization of trauma systems varies across the United States. Even though systems are not the same and may vary widely, the American College of Surgeons (ACS) Committee on Trauma has developed standards to which all trauma systems must adhere to become accredited.¹³ Through these standards, a level (Level I, Level II, etc.) can be assigned to a particular center that designates the resources the center can provide to care for an injured patient. Figure 36-1 describes the characteristics of the modern trauma system, its resources, and the levels of trauma care. What we can take away from the conclusions of the Skamania Symposium and guidance of the ACS Committee on Trauma is that positive outcomes in patient care are directly related to experience and development of a trauma system. Trauma can no longer be considered an offshoot skill where the paradigm involves massive fluid resuscitation, but a specific clinical expertise in which management and therapy directly impacts patient outcome. In short, experience and proficiency matter.

FIGURE 36-1 The levels of trauma care as described in Advanced Trauma Life Support. Lower echelons of care provide stabilizing measures, and care sophistication increases with increasing levels.

Early Evaluation of the Trauma Patient and Common Injury Patterns

Immediate Admission of the Trauma Patient

The Advanced Trauma Life Support (ATLS) course developed by the American College of Surgeons provides a framework for the initial management and evaluation of the trauma patient from the prehospital setting through the hospital phase.

Prehospital

The prehospital management of trauma patients has a deliberate pathway. The primary goals revolve around ensuring a patent airway and adequate ventilation, as well as controlling external bleeding. Patients may be intubated in the field or treated with some other method of airway manipulation before arrival at the trauma center. There remains some controversy over the efficacy of rapid sequence induction in the prehospital setting; however, ensuring adequate oxygenation is essential. All patients should arrive at the hospital with some degree of supplemental oxygen in place.

In most cases, urgent airway management is not required in the prehospital setting. Occult hemorrhage and its ensuing pathology, on the other hand, is the greatest cause of early death from trauma.¹⁴ Blood leaving the circulatory system can spill into cavities throughout the body (e.g., thorax, abdomen, retroperitoneum [the pelvis], or fascial planes of long bones) and/or bleed into the environment (i.e., the street). Classically, hemorrhage was met with intravenous (IV) access and volume resuscitation in the prehospital setting. This practice, however, is going through a renaissance of sorts in an effort to determine what is best practice and management.

As will be discussed later in the chapter, early fluid resuscitation in the absence of surgical hemostasis may not be beneficial because it will likely increase bleeding and may worsen patient outcome. Without hemostasis, mortality increases. The concept of “injury first” has been greatly developed in the wars in Iraq and Afghanistan. Tactical Combat Casualty Care has replaced the “ABC” acronym (airway-breathing-circulation) with “CABC” (catastrophic bleeding-airway-breathing-circulation), emphasizing the immediate application of direct pressure or tourniquets to control exsanguinating hemorrhage. The logic behind this change in priority is that if bleeding is not controlled, the patient will face certain death. Although civilian centers may not have to contend with the limited resources seen in austere environments, this change in approach exemplifies the important role hemorrhage control plays in hemorrhagic shock outcomes.

Primary Survey

Upon admission to the hospital or trauma center, ATLS guidelines provide a logical and sequential treatment strategy for rapidly assessing the patient. This process is commonly referred to as the ABCDE’s of trauma care ¹⁵:

Airway

Breathing

Circulation

Disability (neurologic status)

Environment/Exposure (undress the patient to fully assess)

The goal of the primary survey is to identify and rapidly manage life-threatening conditions or injuries. This sequence of events will be abbreviated and discussed individually from the anesthesia perspective shortly. Generally, however, the primary assessment involves a rapid assessment using physical examination techniques and American Society of Anesthesiologists (ASA) standard monitors. In addition, ultrasound and radiography are used to examine body cavities with the initial goal of determining the extent of injury. During this time, initial blood samples and IV access are obtained. All aspects of the primary survey are done simultaneously, thereby coordinating the efforts of surgical and anesthesia teams to prepare for potential surgical intervention. In the event the injuries are beyond the scope of the initial receiving facility, the primary survey provides the emergency team with enough information to stabilize and prepare the patient for transfer to a higher-level facility.

Secondary Survey

The secondary survey begins after the completion of the primary survey and resuscitative and stabilization efforts have been initiated. The secondary survey is a complete head-to-toe assessment that includes a neurologic examination.

Blunt Versus Penetrating Trauma

Blunt Trauma

Direct impact, deceleration, continuous pressure, shearing, and rotary forces may all contribute to the resulting blunt trauma a patient has incurred. These factors are associated with high levels of energy, and result from high-speed collisions and falls from substantial heights. Newton’s first law can explain how most traumatic injuries occur: an object tends to remain in motion until it is affected by an outside force. Abrupt deceleration creates negative gravitational forces. When the outside “shell” of the human body decelerates abruptly, the internal organs, which in a sense are separate from the exterior of the body, continue forward at the original velocity and are torn from their attachments by way of rotary and shearing forces. These forces often cause disruption of connective tissue, blood vessels, and nerves.

Motor Vehicle Collision Trauma

Blunt trauma is most closely associated with motor vehicle collisions and falls. Blunt trauma tends to produce effects bodywide. The five types of motor vehicle collisions are classified as head-on, rear impact, side impact, rotational impact, and rollover. Injuries can be categorized as those above and those below the waist. The upper portion of the body may collide with the dashboard, steering wheel, or windshield, resulting in injuries of the head, neck, chest, abdomen, and upper extremities. Below the waist, injuries to the knees and femurs occur because of direct contact with the vehicle and lower dashboard. Acetabular fractures are typically a result of tensing the leg when bracing for impact. Blunt trauma rarely occurs in isolated body systems. As such, all blunt trauma victims, including those ultimately without high-risk mechanisms of cervical spine injury, should be suspected of and treated as if they have an unstable cervical spine until proven otherwise.¹⁵

Thoracic Trauma

Blunt chest trauma is the third leading result of injury—closely following traumatic brain injury and extremity trauma. Patients with blunt thoracic trauma present a unique series of concerns. These patients represent some of the most severely injured—with multisystem involvement—accounting for nearly 25% to 50% of all trauma deaths.16,17 In developed nations, thoracic trauma is most often associated with motor vehicle collisions.

Blunt thoracic trauma often results when drivers who are not wearing safety belts impact the steering wheel during a motor vehicle collision. Penetrating and blunt trauma to the chest may injure several structures and thus compromise optimal resuscitation. Possibly injured structures include the chest wall, the lungs and airways, the heart and pericardium, and the great vessels of the thorax. Injuries to these structures also compromise anesthesia care by affecting gas exchange and cardiac output.

Pneumothoraces are present in as many as 40% of all blunt thoracic injuries.¹⁶ The size and location of the pneumothorax may vary throughout the lung field. Although the etiology and management of pneumothoraces is somewhat commonplace to providers, the presence, or in many cases the assumed absence, of a pneumothorax should not be minimized. It is estimated that as many as 50% of pneumothoraces are not detected on initial radiography.¹⁷ This occurrence presents several clinical intraoperative issues and may alter an anesthetic plan. Nitrous oxide should be avoided in patients with suspected thoracic trauma.

A number of life-threatening injuries, described below, require immediate interventions in patients with thoracic/chest trauma.

Damage Control Surgery

Surgical management for the severely traumatized patient is often a multistep process. In many cases, patients present to the trauma center with surgical emergencies. Early repair is often simply a life-saving measure and is not intended to be a definitive repair but rather a stabilizing measure, intended to reduce operating room (OR) time and morbidity.19,20 After stabilization, patients will be transported for further evaluation (secondary survey) or additional resuscitation measures in the intensive care unit (ICU). Often patients will be returned to the OR several times because the surgical course involves several phases. This staged approach to surgical management is commonly known as damage control surgery (DCS).

Damage control surgery is a concept that developed in the early twentieth century. Its use fell in and out of favor until the 1970s and 1980s. Its utility in modern trauma care was rediscovered as advances in surgical technique, critical care medicine, and technology converged. DCS correlates with current concepts in trauma care that include damage control resuscitation with rapid surgical correction of bleeding and the prevention of the lethal triad of acidosis, hypothermia, and coagulopathy. It also involves limitation of crystalloid administration and application of high ratios of plasma and platelets to packed red blood cells.21,22 DCS is used in various surgical disciplines, from packing the abdomen after abdominal trauma to using external fixators to set complex orthopedic injuries.²³

Abdominal Trauma

Blunt abdominal trauma is a leading cause of morbidity and mortality among all age groups. Although diagnosis and treatment of penetrating trauma is easily determined, occult bleeding in blunt abdominal injury is often misdiagnosed.24,25 Abdominal sonography, Focused Assessment with Sonography for Trauma (F.A.S.T.), computed tomography (CT) scan, magnetic resonance imaging (MRI), or angiography may help in the diagnosis of specific injuries and various treatment modalities. Extremely unstable patients, however, will require immediate surgery. It is essential that large-bore intravenous access be in place, above the diaphragm, prior to opening the abdomen in the event of massive hemorrhage as a result of liver or other organ injury.

The ABCD’s of Trauma Anesthesia

Although the ATLS curriculum provides an organized framework for the management of traumatic injury, it is not specific to any one discipline. The following sections discuss the implications of the ABCD’s of trauma anesthesia and provide an approach to clinical management. It cannot be overstated; anesthesia must facilitate rapid surgical management. Trauma anesthesia and surgery is not elective. It should be the goal of the anesthesia team to rapidly move the patient to the OR. Perfusion of tissue (or lack thereof) is directly related to time.

Airway

Endotracheal intubation is a routine procedure of anesthesia practice. Despite its regular use during general anesthetics, intubation poses significant risk and may be extremely challenging when caring for the acutely injured patient. Difficult tracheal intubation is the third most common respiratory-related event leading to death and brain damage as reported in the ASA Closed Claims analysis.²⁶ Although certainly not all trauma patients will have a difficult airway, the anesthetist likely will not have the opportunity or time for a full airway examination because of several variables such as facial injuries and/or hypoventilation and apnea. As such, the provider must anticipate the worst-case scenario.

Emergent intubation in the trauma patient follows the general pathway of the ASA difficult airway algorithm.²⁷ Three assumptions should be made when approaching this type of patient. First, there is no turning back. Intubation is not routinely elective for these patients. Therefore, once induction begins the patient must end up with a controlled airway. In addition to requiring a secured airway, trauma patients are assumed to have delayed gastric emptying and a full stomach. As such, they are at increased risk for aspiration. Finally, any patient with blunt trauma or with penetrating injuries to the neck and face must be considered for cervical spine instability.

Rapid sequence intubation (RSI) is the standard method for traumatic airway management. This practice involves several steps often not used during standard induction. One of the greatest differences between routine induction and RSI is the use of a muscle relaxant before knowing whether the patient can be mask ventilated. Although daunting, and a deviation from the norm, muscle relaxation is associated with the highest overall rate of successful airway management and provides the greatest possibility for rapidly securing the airway.²⁸

Steps to RSI

RSI begins with appropriate planning and team practice. Sufficient personnel must be on hand to (1) provide manual in-line stabilization of the cervical spine after removing the front of the cervical collar; (2) provide cricoid pressure (the Sellick maneuver); (3) oxygenate the patient with bag-valve-mask ventilation and then perform direct laryngoscopy; and (4) administer medications.

Direct laryngoscopy during manual in-line stabilization of the cervical spine is a safe and effective procedure in patients with potentially unstable necks.29,30 Cricoid pressure is applied and intended to prevent both gastric insufflation during bag-valve-mask ventilation and passive reflux of gastric contents. Although caution is appropriate, both cervical spine injury and aspiration during intubation are moderately low-risk events when compared with the possible risks and injury from hypoxia. Therefore, it must be remembered that airway management is the priority. In-line stabilization and cricoid pressure should be relaxed if they are interfering with successful intubation.

Whenever RSI is undertaken, the need for an emergent surgical airway is always a possibility; appropriate surgical resources should be immediately available in the event of the need for a surgical airway.

Common Indications for Airway Management

Patients with traumatic injury present in varying degrees of injury and may require emergent airway management. The most common indications for endotracheal intubation include: (1) inadequate oxygenation/ventilation; (2) loss of airway reflexes; (3) decreased level of consciousness (Glasgow Coma Scale [GCS] less than 8); and occasionally, (4) the need for pain management and the ability to safely provide deep sedation during painful procedures. Once it is deemed that the patient requires airway management, it should be done using RSI.

RSI is a procedure that is conducted to rapidly control a patient’s airway, while reducing the likelihood of gastric aspiration. RSI consists of five primary components: (1) preoxygenation, (2) cricoid pressure, (3) induction/muscle relaxation, (4) apneic ventilation, and (5) direct laryngoscopy. Each of these steps is discussed in detail below.

Preoxygenation

Adequate preoxygenation is likely the best asset for the anesthetist managing a trauma patient. Preoxygenation provides the greatest amount of time before occurrence of hypoxemia. Preoxygenation is accomplished using 100% high-flow (10-15 L) oxygenation via a nonrebreather facemask or bag-valve facemask. Although there is some debate in the literature, four to eight tidal volume breaths appear to provide superior preoxygenation when compared with 3 minutes of tidal breathing.³¹

Preoxygenation is challenging in regard to patients who are unable to deep breathe or follow commands when obtunded. In these circumstances, it is appropriate to provide controlled positive pressure bag-valve-mask ventilation throughout induction. An increased oxygen reservoir in the lung will benefit the patient more than the (theoretic) increased risk of aspiration caused by ventilating through cricoid pressure.

Cricoid Pressure

Cricoid pressure was first described by Sellick in 1961.³² The goal of this maneuver is to reduce the risk of pulmonary aspiration of gastric contents by compressing the esophagus with the continuous ring of the cricoid cartilage.³³ Cricoid pressure is maintained throughout the RSI and is not released until endotracheal tube (ETT) placement has been confirmed. Determining the appropriate pressure to apply to the cricoid ring has been the subject of debate. Vanner and Pryle³⁴ have determined that 30 Newtons (approximately 10 lbs of pressure) adequately occludes the esophagus.

Induction Agents

Anesthetic induction for RSI can be achieved by a variety of agents. At this time no literature is available to support the superiority of one agent over another. All induction agents will cause dose-dependent decreases in blood pressure in the hypovolemic, hemorrhaging patient. Dose-dependent hemodynamic instability can likely be attenuated by reductions in the induction dose. Although no formula can precisely predict the dose for a hemodynamically unstable patient, some authors suggest a dose that is one tenth to one half of the normal induction dose of propofol.³⁵ Ketamine can always be considered as an alternative trauma induction drug.^36,37 Etomidate use is discouraged due to the suppression of adrenal function. Recall during induction, an undesirable consequence, is a secondary concern when urgently managing an unstable trauma patient.

Succinylcholine (1.5 mg/kg) provides favorable and rapid muscle relaxation to facilitate intubation. It is generally the preferred agent for RSI for any patient who has no specific contraindication to its use. Succinylcholine administration may cause lethal hyperkalemia in patients with neurologic deficits from spinal cord injury, but not until 24 to 48 hours after injury.³⁸

Rocuronium (1.2 mg/kg) and vecuronium (0.2 mg/kg) also can be used for RSI. The onset time for high-dose rocuronium (1.2 mg/kg) is similar to that for succinylcholine with only a slight delay in achieving complete relaxation.³⁹ Although these nondepolarizing agents may produce adequate intubating conditions, their use may influence what care can be provided. Prolonged paralysis will require sedation and will make any subsequent neurologic assessment more difficult.

Apneic Ventilation

Apneic ventilation is the concept of pulmonary ventilation using high-flow oxygen. Its purpose is to reduce the potential risk of gastric distension and pulmonary aspiration from positive pressure ventilation. The principle of apneic ventilation is based on Boyle’s law in which gas leaves the facemask, fills the lungs, and exchanges in the lungs based upon the concentration gradient of gases in the alveoli. To work appropriately, apneic ventilation assumes that the airway is patent and that a high concentration of oxygen can be reliably administered.

Apneic ventilation remains controversial for practitioners. RSI for the trauma patient is intended to reduce the risk of aspiration in the case of a potentially full stomach, yet many trauma patients who present are unable to take a deep breath prior to induction, resulting in a reduced functional residual capacity and pulmonary reserve. Traditionally, with RSI, the practitioner is taught to refrain from positive pressure ventilation during induction. This practice, however, is commonly being modified by clinicians.

To avoid potential hypoxemia or in the event of an already hypoxemic patient, clinical modifications have been made to RSI that include bag-valve-mask ventilation through cricoid pressure—often termed “modified RSI.” This method is actually the technique described by Sellick in 1961.32,40 To date, there does not appear to be any increase in aspiration by bag-valve-mask ventilation through cricoid pressure.

Direct Laryngoscopy

No evidence indicates that a particular laryngoscope blade or size is optimal for RSI. The choice is likely provider dependent. The provider should use the equipment with which he or she is most comfortable.

Successful endotracheal tube placement is immediately confirmed by capnometry. If unsuccessful, a second direct laryngoscopy should be attempted, incorporating some change in technique (e.g., different laryngoscopist, blade, or patient position). There are a variety of adjunct tools available in the event of an unplanned difficult intubation. These include the basic and inexpensive, such as the intubating stylet or bougie, to the more advanced fiberoptic equipment.

If intubation is again unsuccessful (third attempt), the next step should be an airway adjunct to support oxygenation. These adjuncts range from the Combitube to the laryngeal mask airway (LMA). In the situation of “cannot intubate and inadequate facemask ventilation,” LMA insertion should be the immediate next step.⁴¹

Airway Management of Cervical Spine Injuries

Cervical spine injury remains a significant concern when facing airway management of the trauma patient. The incidence of cervical spine injury after trauma is relatively rare at 2% to 3% of all trauma and approximately 6% to 10% for patients with traumatic brain injury.⁴² Cervical spine injury should be assumed until proven otherwise. Immobilization of the neck is essential. To that end, in-line stabilization is essential because it allows for removal of the front of the cervical collar, allowing more area for jaw and mouth movement, while limiting the risk for further injury.

The management and intubation of patients with suspected cervical spine injuries remains clinically controversial. Despite common belief, there is no evidence to suggest that fiberoptic intubation provides safer patient outcomes when compared with direct laryngoscopy with in-line stabilization.43–45 As such, management of a cervical spine injury may be done so with the concepts of “emergent” which involves in line stabilization and RSI versus “controlled” which involves an awake fiberoptic technique. Figure 36-2 describes a logical management strategy for these two situations.

FIGURE 36-2 A logical management algorithm for controlled versus emergent airway management for a patient with a cervical spine injury. RSI, Rapid sequence induction; FOI, fiberoptic intubation.

Breathing (and Ventilation)

Regardless of the need to manage the airway, the adequacy of breathing and ultimately patient oxygenation is essential to survival. Pulse oximetry is a commonly used noninvasive method to continuously monitor oxygen saturation. Pulse oximetry is often used as a surrogate measure of status. Although pulse oximetry provides a wealth of clinical information, it should be realized that this measurement is not ideal and that the data may provide a false sense of security. For instance, an otherwise healthy patient breathing room air oxygen (21%) will have a Pao₂ level of approximately 100 mmHg and an Sao₂ of 100%. If the patient is placed on a high-flow, nonrebreather mask of 100% oxygen, then the Pao₂ could be expected to be approximately 500 mmHg and Sao₂ would remain at 100%. Patients who experience declining pulmonary function will have a Sao₂ of 100% over a wide range of Pao₂ readings. It must be recognized that supplemental oxygen, although necessary, can mask pulmonary injury and in some cases respiratory decompensation. It should not be concluded that a saturation of 100% equates to a stable patient or the health of the pulmonary (breathing/ventilation) system.

Pulmonary contusions represent the most common lung injury. It is reported that as many as 70% of patients with blunt thoracic trauma present with some degree of pulmonary contusion.¹⁷ Pulmonary contusions are injuries to the alveoli without gross disruption of pulmonary architecture. This injury is essentially a bruise to the lung tissue resulting in protein-rich fluid leaving ruptured pulmonary capillaries and settling into the alveolar membrane and interstitial space. Due to the widening of the pulmonary membrane, pulmonary contusions result in varying degrees of reduced gas diffusion that may be clinically relevant. Pulmonary contusions can develop or “blossom” over a range of time and ultimately may develop into acute respiratory distress syndrome (ARDS).

ARDS is a common problem in trauma care. It may be a result of injury or the resuscitation of the patient. It has been estimated that between 10% and 40% of patients with traumatic injury will develop ARDS over their hospital course. Pathologically, ARDS is a result of protein-rich fluid leaving the pulmonary capillaries. As the disease progresses, the pulmonary capillary leakage is compounded by embolic events, which further increase intracapillary pressure and intensify interstitial leakage. ARDS culminates in hypoxia and decreased pulmonary compliance. Ventilating these patients is a challenge. Clinicians are often faced with the inability to appropriately oxygenate the patient without using high pressures to ventilate.⁴⁶ High pressures and decreased compliance sets the patient up for barotrauma and worsening pulmonary disease.

A variety of pulmonary techniques have been described for managing these patients. They range from high-frequency oscillation ventilation to cardiopulmonary bypass. At this time no one technique appears to be superior. It is widely accepted, however, that these patients should be ventilated using low tidal volumes to reduce peak pressures, and the plateau pressures should be maintained at less than 32 cm H₂O.47,48 Although attempting to correct an Sao₂ that is less than normal (less than 95%) by increasing the Fio₂ may seem to be a desirable action, it would likely not be the best practice because of the toxic effects of oxygen over time, which can potentially worsen gas exchange.

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