Key points

Introduction

A presenting diagnosis of isolated severe traumatic brain injury (TBI) or acute spinal cord injury (SCI) triggers a specialized set of considerations specific to the neurocritical care management of the patient in question. When that presentation is complicated by injury to multiple body systems (or, polytrauma) a delicate dance ensues. While the ultimate goals of care remain the same—to optimize outcomes and reduce potential harms—the path forward may be encumbered by conflicting priorities and objectives. The initial triage and resuscitation effort should be focused and efficient, with an emphasis on ensuring the “ABCs” (airway, breathing, circulation) are satisfied—regardless of the combination of injuries present. For the patient with comorbid neurologic injury, this phase of care also must account for concerns relevant to the treatment of the primary central nervous system (CNS) process and mitigation of secondary insults. A series of questions will help frame this exploration of challenges to neurocritical care management in the setting of polytrauma.

How does the epidemiology of polytrauma define the role of neurocritical care in this setting?

Understanding the epidemiology of polytrauma is essential to anticipate likely combinations of injury, differentiate relative severity, and recognize potential impacts on patient course. The first challenge in this process stems from the fact that there exists no validated definition for polytrauma. The term “polytrauma” initially was applied simply to denote 2 or more comorbid injuries. Tscherne and colleagues built upon this description to include the idea that at least 1 or the sum total of all of the injuries should be considered life-threatening. More recently, the Berlin definition emerged from an international consensus effort. The Berlin definition stipulates at least 2 injuries with an abbreviated injury scale (AIS) score ≥3, coupled with the presence of 1 or more of the following: systolic blood pressure (SBP) ≤ 90 mm Hg, Glasgow Coma Scale (GCS) score ≤8, base excess ≤ −6.0 (acidosis), international normalized ratio (INR) ≥ 1.4 or partial thromboplastin time ≥ 40s, and age ≥70 y.

There are approximately 2.5 million emergency department visits for TBI annually, with approximately 282,000 TBI-related hospitalizations and 56,000 TBI-related deaths. The overall annual incidence of TBI is estimated as 5000 to 8000 cases per million. Acute spinal cord injury is relatively less common, with a projected incidence of 54 cases per million. The incidence of combined brain and spinal cord injuries has been estimated as 3 to 10 cases per million. If the brain injury is considered primary, up to 13% of patients will experience concomitant spine injury, ^, whereas the incidence of comorbid moderate or severe brain injury in a patient with primary cervical spinal cord injury has been estimated to range from 18% to 40%. ^,

Trauma-related mortality typically occurs in 3 waves: (1) “immediate,” in the field, due to lethal primary injury; (2) “early,” within minutes to hours, due to airway compromise, hemorrhagic shock, and/or catastrophic intracranial injury; and (3) “late,” days to weeks later, due to multisystem organ failure, overwhelming sepsis, malignant systemic inflammation, and/or refractory raised intracranial pressure (ICP). It is notable that neurologic injury is a factor at each of these outcome intervals. Indeed, greater than 50% of polytrauma patients have an associated TBI. ^, While exsanguination is the strongest contributor to early mortality among polytrauma patients, the primary overall determinant of mortality in this population is often the severity of the head injury. In fact, the presence of TBI may increase mortality up to threefold; delayed mortality is most often attributable to TBI. In a recently published prospective cohort of 578 severely injured patients, the overall mortality rate was 18% (106/578) and two-thirds (66%, 70/106) of the recorded deaths were attributable to TBI. Age, severity of the comorbid TBI, base deficit, hypoxia, and resuscitation with crystalloid were identified as contributing factors. Even moderate brain injury may double predicted mortality when associated with extracranial injuries. ^, Interestingly, in one large prospective study, the presence of polytrauma influenced mortality among patients with moderate but not severe brain injury.

The outsized influence that comorbid neurologic injury—particularly, TBI—seems to have on mortality in the setting of polytrauma underscores the importance of early and persistent attention to neurocritical care goals. Even when other priorities might take precedence during initial resuscitation (see question #2), the astute clinician will recognize potential neurologic vulnerabilities (hypoxia, hypotension, raised ICP, etc.) and advocate for modifications in management designed to optimize neurologic function and reduce the risk of secondary injury. A multidisciplinary approach that is inclusive of all organ systems, maintains awareness of the impact treatment decisions for one system may have on others, and embraces open communication among providers is essential to deliver care that addresses the physiologic whole.

What factors influence the order of interventions for the polytrauma patient with neurocritical illness?

Neurosurgeons are conditioned to believe that there is very little standing between them and an operating room when a patient presents with an indication for emergent operative cranial or spinal intervention. However, the order of operations in the setting of polytrauma is driven by a series of decision branch points, sometimes involving conflicting data, priorities, and goals. A methodical, organized team approach is essential. Hemodynamic stability is the overarching concern . The patient presenting with polytrauma should be managed in accordance with Advanced Trauma Life Support (ATLS) guidelines. Once the “ABCs” have been addressed, “D” (disability) may be assessed. This is the moment in the primary survey where the patient’s neurologic status comes into focus. Pupillary symmetry, size, and reactivity should be documented. Lateralizing motor or sensory findings should be noted. The GCS score is calculated. A GCS score ≤8 should trigger prompt intubation for airway protection (if not already secured). The differential diagnosis for a depressed level of consciousness at this point is both broad and consequential: decreased cerebral oxygenation (“A”), decreased cerebral perfusion (“C”), direct cerebral injury (“D”), intoxication with alcohol or drugs, metabolic derangement, or seizure.

Coincident with the initial resuscitation effort, the clinician must recognize that polytrauma patients with neurologic injury are particularly susceptible to secondary insults. While blood on a head computed tomography (CT) is certain to generate a request for neurosurgical consultation, secondary injury is not visible on that initial study and, therefore, may not be foremost in the minds of the front line trauma staff resuscitating the patient. Secondary injury unfolds over the minutes, hours, and days after the initial traumatic insult. Secondary injury is insidious and may be lethal. The Trauma Coma Databank Study demonstrated that a single episode of hypotension before arrival to care doubled mortality, increased morbidity, and was associated with poorer outcomes. ^, Hypoxia also has been associated with higher mortality and worse neurologic outcomes. Stocchetti and colleagues observed hypotension in nearly 1-quarter (24%) and hypoxia in greater than half (57%) of patients with TBI (mean GCS 7) in the field. While 80% of those with preserved blood pressure and saturation in the field went on to favorable outcomes, the prognosis for those with compromise of both was uniformly poor. Chi and colleagues reported that nearly 40% of isolated TBI patients sustain a secondary insult in the field and that the presence of hypoxia resulted in a significant increase in the odds of mortality (odds ratio [OR] 2.66).

While it is clear that care should be taken to avoid hypoxia and hypotension, additional factors may exert a negative influence on mortality (hypotension, hyperglycemia, and hypothermia) and length of intensive care unit (ICU) stay (hypocapnia, acidosis, and hypoxemia). These conditions should be recognizable as common findings during the acute phase of polytrauma care, highlighting the need to be proactive in identifying and treating physiologic and metabolic derangement. Furthermore, a recently published study from the (Transforming Research and Clinical Knowledge in Traumatic Brain Injury [TRACK-TBI]) group reported worse 2-w and 6-mo functional outcomes among patients with CT-positive TBI who were exposed to extracranial interventions and anesthesia during the index hospitalization. In recognition of these vulnerabilities, the World Society of Emergency Surgery (WSES), in 2019, published a series of 16 consensus recommendations to guide the early resuscitation of polytrauma patients with severe TBI. The recommendations are predicated upon first achieving control of life-threatening hemorrhage and emphasize that the practice of allowing permissive hypotension during so-called “damage control resuscitation” ^, may have dire consequences with respect to aggravating secondary neurologic injury. Once hemorrhage is controlled, the focus of care should shift to evaluation and management of potentially-life-threatening neurologic injury.

For a hemodynamically unstable patient with decreased consciousness and lateralizing findings, a space-occupying intracranial process is presumed. Neurologic resuscitation should proceed in parallel with trauma surgeon efforts. The primary resuscitation endpoint should be to maintain an adequate mean arterial pressure (MAP) to support cerebral perfusion pressure (CPP). The WSES consensus statement recommends a target MAP greater than 80 mm Hg or SBP greater than 100 mm Hg, as well as CPP greater than 60 mm Hg during this period. Secondarily, aim to avoid hypoxia (P o ₂ < 60 mm Hg) and discourage hypercarbia, maintaining P co ₂ in the 35 to 40 mm Hg range. The goal of coagulopathy correction likely harmonizes with trauma team efforts. The WSES consensus statement recommends the following hematologic endpoints: hemoglobin greater than 7, platelet count greater than 50K (100K minimum if invasive neurosurgical intervention is contemplated), and INR less than 1.5. If massive transfusion protocol is initiated, products should be provided in a 1:1:1 ratio (red blood cells: plasma: platelets). Empiric hyperosmolar therapy may be considered, with the choice of agent reflecting the patient’s volume status and blood pressure. Hypertonic saline may be better tolerated in a hypotensive patient than mannitol. CT imaging should be obtained as soon as feasible.

For the hemodynamically stable patient, CT head presumably will be obtained in conjunction with diagnostic trauma imaging studies. GCS and imaging findings should be weighed against pertinent positive extracerebral findings. If the patient presents with decreased level of consciousness, lateralizing findings, and evidence of a space-occupying lesion, the intracranial pathology should take precedence. Conversely, if there is no imaging-driven indication for neurosurgical intervention, but the patient will require surgery for another indication and/or a prolonged intubation is anticipated, placement of an invasive ICP monitor should be considered. If the patient presents with indications for emergent intervention involving both brain and an extracerebral site, consideration may be given to serial or simultaneous intervention. Issues particular to contemporaneous management of TBI and SCI will be addressed in the next section (question #3).

Once this critical phase of decision-making plays out, the timing of extracerebral, and non-neurologic interventions may be entertained. Orthopedic (non-spinal) pathology comprises the largest segment of such injuries. One large German registry study estimated that nearly 60% of patients with multisystem injury harbor at least 1 significant extremity injury. The presence of that injury, in turn, correlated with higher rates of transfusion, severe chest trauma, and operative procedures, as well as longer ICU and hospital length-of-stay. (Interestingly, those without such injuries tended to present with a lower GCS score in the field, worse brain injury, and higher mortality—both in-hospital and 30-d.) The classic arguments in favor of “early definitive care” (EDC) for orthopedic pathology—decreased inflammation at the fracture site, decreased pain and narcotic use, improved pulmonary mechanics, earlier mobilization, lower rates of venous thromboembolic (VTE) events— are compelling but must be weighed against the potential for perioperative morbidity related to other injuries and the possibility of perturbing a delicate balance in a patient who might be incompletely resuscitated or physiologically compromised. Poorly-timed orthopedic intervention has also been associated with an exuberant systemic inflammatory response syndrome and multiple organ dysfunction syndrome— both potentially detrimental to the patient. ^,

Orthopedic practice with respect to fracture fixation has evolved over time from the EDC model to that of “damage control orthopedics” (DCO) and more recently, the concept of “safe definitive surgery” (SDS). The DCO model prioritizes resuscitation and embraces the notion of early temporary and staged definitive fixation. This paradigm shifts the focus to abbreviated procedures for hemorrhage control, debridement to reduce contamination, and stabilization of bone and soft tissue—only what is necessary to preserve life and limb. The concept of SDS was introduced in an effort to strike a balance between the risks inherent in the aggressive EDC model and the potential negative consequences of delayed intervention. SDS offers a dynamic approach to care, with initial triage by clinical status, followed by serial assessment to determine when a reasonable window of opportunity exists for intervention.

A recently published meta-analysis synthesizes the literature supporting each of these approaches to arrive at a series of guiding principles for early fracture care in polytrauma, with the following order of priorities: (1) life, (2) neurologic disability, (3) limb, and (4) functionality. This model provides a reasonable framework with which to approach clinical decision-making in the subpopulation of polytrauma patients with neurologic injury. Decisions regarding definitive intervention should be individualized and reflect improving hematologic, metabolic, and hemodynamic indices. Early definitive fixation of fractures (the overall goal) is typically acceptable for patients with mild TBI (GCS ≥13). For the patient with severe TBI, delayed definitive fixation is favored pending demonstrated stability of imaging findings, hemodynamic stability, and maintenance of ICP (≤20 mm Hg) and CPP (>60 mm Hg) in goal range for at least 48 h. For the patient with comorbid SCI, this might include a stable to improving neurologic examination with maintenance of MAP at goal range (85 – 90 mm Hg) for at least 48 h, as well as no contraindication to positioning for the orthopedic procedure (based upon spine stability). However, early reduction, decompression, and fixation for the spine injury, as indicated, should take precedence over fixation of other fractures.

Craniofacial trauma, on the other hand, is rarely life-threatening and generally does not require emergent intervention. Mulligan and colleagues used a large National Trauma Data Bank dataset to correlate the incidence of TBI, facial fractures, and cervical spine injury. Facial fracture was diagnosed in 21.7% of patients presenting with head injury, 13.5% of patients presenting with cervical spine injury, and nearly 1-quarter (24%) of patients presenting with combined TBI and cervical spine injury. Head injury was present in 67.9% of patients with a facial fracture, 40.2% of patients with cervical spine injury, and in 71.5% of patients with combined facial fracture and cervical spine injury. While there are some evidence that early fracture repair may improve functional or aesthetic outcomes, ^, the presence of comorbid severe TBI or acute SCI may downgrade this priority. Early operation risks the uncertainty of fluid shifts due to blood loss and/or fluid replacement, vasodilatory anesthetic agents, and positioning that may impact ICP or spinal cord perfusion. The development of a cerebrospinal fluid (CSF) leak may introduce an additional confounding factor. Onset is often delayed in this setting and may not become evident until peak cerebral edema has abated or an indwelling external ventricular drain is weaned. Initial conservative management (in blunt trauma) may be a reasonable option. Elevation of the head of bed and rhinorrhea precautions may be effective. If leakage persists, consideration may be given to temporary CSF diversion, bearing in mind that significant intracranial pathology may preclude use of a lumbar cisternal catheter. Definitive repair of facial fractures and/or CSF leak typically occurs once neurologic clinical stability has been established.

How are management priorities established in a patient with both severe traumatic brain injury and acute spinal cord injury?

Once the basic steps of trauma triage and resuscitation have been executed and life-threatening hemorrhage controlled, priority is accorded to any intracranial process requiring emergent intervention for evacuation of a space-occupying lesion and relief of mass effect. Care should be taken intraoperatively to ensure adequate stabilization of injured spine segments, as well as to maintain adequate MAP to support spinal cord perfusion (for cervical and/or thoracic level pathology). This requires close coordination with the anesthesia team. Timing of interventions deemed necessary for the management of spinal pathology—whether to achieve reduction, decompression, and/or stabilization—is dictated by clinical stability thereafter. In select cases, the spinal intervention may follow directly in series. However, if evidence of massive herniation/raised ICP despite decompression, hemodynamic instability, and/or coagulopathy, it may be prudent to proceed to the ICU for resuscitation and plan to address the spinal pathology in a staged fashion. The clinician should also be attuned to the fact that performance of a unilateral or bilateral craniectomy may pose challenges to positioning for a subsequent prone position spinal procedure.

It follows that management of these patients in the ICU may pose challenges to conventional wisdom regarding best practices and endpoints. Seemingly conflicting clinical goals may stymie even the most experienced provider. For example, while it is desirable to maintain the head of bed at ≥30° for a patient with severe TBI (to encourage increased venous outflow and decrease ICP), spinal cord perfusion may be optimized if the patient is nursed with the head of bed closer to 0°. A compromise—weighing the relative risks and benefits for each organ system—may dictate maintaining in-line, neutral position of the bed, with application of slight reverse Trendelenburg (up to 20°) as tolerated by MAP goals for the cord injury.

This, of course, raises the question of what constitutes an appropriate blood pressure target for such a patient. The second edition of the Guidelines for the Management of Acute Cervical Spine and Spinal Cord Injuries provides a Level III recommendation to maintain MAP in the 85 to 90 mm Hg range for the first 7 d post-injury and cautions that pushing MAP beyond this range may have consequences for other organ systems (contributing to the development of adult respiratory distress syndrome [ARDS] or reperfusion injury). While the fourth edition of the Brain Trauma Foundation Guidelines for the Management of Severe Traumatic Injury suggests maintaining a minimum SBP ≥100 mm Hg for patients 50 to 69 y of age (and SBP≥110 mm Hg for those older or younger), an upper limit is not proposed. Targeting a significantly higher blood pressure value to meet the spinal cord perfusion goal may hypothetically risk hemorrhage or hyperemia with rebound cerebral edema and subsequent raised ICP in the patient with severe TBI. It may turn out that monitoring cerebral perfusion pressure in tandem with spinal cord perfusion pressure provides a “normalized” target transferable from brain to spinal injury. While the Brain Trauma Foundation guideline provides a level IIB recommendation to target a CPP range of 60 to 70 mm Hg, it comes with the caveat that the optimal range may depend on the autoregulatory status of the patient. The science around invasive monitoring of spinal cord perfusion is still evolving and a validated target has yet to be established, though a range of 60 to 65 mm Hg has been suggested in multiple studies.

Patients with dual diagnoses of severe TBI and acute SCI typically endure a protracted initial ICU and hospital course, with systemic complications ranging from near ubiquitous fever (whether infectious or centrally-mediated) to ventilator-associated pneumonia, VTE events, feeding syndromes, skin breakdown, and so forth. It follows that there are little data regarding outcomes that is relevant to this subset of patients. A methodical, systems-based approach to care is paramount. Close communication with critical care staff is essential to navigate uncertainty not only regarding issues relevant to the neurologic injury but also the impact of management decisions made by the intensivist to support the function of other organ systems.

ARDS provides a particularly salient example of the potential for conflicting physiologic objectives. ARDS severity is defined by the ratio (PF) of the partial pressure of oxygen (Pa o ₂ ) to the fraction of inspired oxygen (Fi o ₂ ), where a ratio of ≤100, 101 to 200, and 201 to 300 corresponds to severe, moderate, and mild disease, respectively. Brain tissue oxygen (PbtO ₂ ) measurement correlates with the PF ratio in patients with severe TBI. Leroux and colleagues demonstrated a progressive decrease in PbtO ₂ with worsening PF ratio in patients with acute lung injury. This suggests the potential for brain ischemia and exacerbation of secondary injury with progressive arterial hypoxemia.

Current management guidelines for ARDS advocate for a lung-protective ventilation strategy (tidal volume 4 to 6 mL/kg predicted body weight), coupled with maneuvers designed to optimize ventilation and oxygenation. However, common strategies employed to achieve these goals may exacerbate neurologic injury. Permissive hypercapnia (in the range of PCO ₂ 50 – 55 mm Hg) runs counter to the goal of maintaining P co ₂ in a reasonably neutral (35 – 40 mm Hg) range for a patient with raised ICP. Hypercapnia promotes cerebral vasodilatation with a consequent increase in cerebral blood volume, promoting a further rise in ICP for a patient with compromised brain compliance. Recruitment maneuvers, while potentially beneficial to oxygenation, may contribute to a rise in intrathoracic pressure, decreased venous return, and, ultimately, an increase in ICP.

Similarly, the use of escalating levels of positive end-expiratory pressure (PEEP) (sometimes up to 18 – 20 mm Hg) may have a deleterious effect on ICP. However, the correlation between application of PEEP and ICP level is not entirely linear; while it is generally agreed that PEEP-induced changes in pleural pressure may reduce cerebral venous drainage, the threshold at which ICP may be adversely impacted has been a matter of some controversy in the literature. The ICP response to PEEP seems to be governed by properties of lung and chest wall elastance (the inverse of compliance). When lung elastance is high, airway pressure transmission to the venous system is relatively muted, but when chest wall elastance is high, pleural pressure tends to increase, eventually impacting ICP. In one study of subarachnoid hemorrhage patients with acute lung injury, patients with a more pronounced ICP response to increasing PEEP also demonstrated a higher chest wall elastance and chest wall-to-respiratory system elastance ratio. There is some evidence to suggest that the use of nitric oxide may actually lower ICP, but the use of prone position ventilation is problematic—both mechanically in a patient with a craniectomy and/or invasive monitor and for the risk of exacerbating an ICP crisis. Ultimately, the neurocritical care management of such patients requires multidisciplinary prioritization, negotiation, and often, compromise to weather the crisis. Goal P co ₂ values and PEEP targets should be individualized on the basis of observed ICP response.

The complexity inherent in management of a patient with comorbid severe TBI and acute SCI extends even to the determination of death by neurologic criteria. The provider must appreciate that a patient with an upper cervical spinal cord injury may appear to have absent lower cranial nerve responses due to cephalad extension of intrinsic spinal cord edema or hemorrhage to the brainstem. Therefore, the standard clinical examination performed as part of this process may not be valid. A confirmatory diagnostic test is strongly advised. The Level A recommendation for the recognition of this confounding factor and appropriate application of an ancillary test in the 2023 Pediatric and Adult Brain Death/Death by Neurologic Criteria Consensus Guideline underscores the importance of this issue.

Does cohorting critically ill patients with neurologic injury in a specialized setting impact outcome?

Admission to a specialized care setting may confer some survival benefit to polytrauma patients with severe TBI. Roberts and colleagues analyzed outcomes for 548 patients with severe TBI (median injury severity score [ISS] 18, head AIS 3) admitted either to a closed trauma (207, 34%) or neuroscience (341, 62%) unit over a 1-y period. Those admitted to the trauma unit had statistically higher ISS scores and were more likely to have had a high-speed mechanism, as well as lower presenting systolic blood pressure and worse neurologic examination. These factors may place this cohort at increased risk for secondary injury and contribute to the observation of a higher unadjusted mortality risk (23% vs 12%). However, the adjusted 30-d mortality was ultimately lower for trauma unit patients. The authors conclude that admission of polytrauma patients with severe TBI to a specialized TICU may positively impact survival.

The authors also cite an earlier article by Lombardo and colleagues gauging the association between ICU type and survival, as well as the probability of death with increasing ISS for patients with a presentation GCS score ≤13 and with CT-positive TBI. Patients with isolated TBI were analyzed separately from those with concomitant injuries. Unit type, age, and ISS were independent predictors of death after adjustment. The effect of ISS on mortality also was affected by admission unit type. Polytrauma patients with TBI admitted to a specialized trauma unit demonstrated improved survival with increasing ISS (though any benefit of a trauma relative to a neuroscience unit seemed to diminish at very high ISS scores). Isolated TBI patients demonstrated similar rates of survival whether admitted to a neuroscience or trauma unit. The worst survival rates were associated with admission to a Med/Surg ICU setting. These studies, taken together, emphasize the importance of a specialized care setting to optimize outcomes for polytrauma patients with neurocritical illness.

Summary

Critical care management of the polytrauma patient with neurologic injury—whether TBI and/or SCI—requires a methodical, yet nimble approach to respond effectively when acute changes occur and to navigate sometimes conflicting clinical endpoints. Multidisciplinary engagement and clear lines of communication are essential to optimize outcomes and mitigate harms.

Clinics care points

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  ABCs first—but maintain an awareness of how management decisions may impact the CNS injury and neurocritical care management goals.

  
  
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  Hemodynamic stability drives the overall “order of operations;” brain is prioritized over spine when indications exist for emergent intervention at both sites.

  
  
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  Contradictory critical care objectives for the management of comorbid severe traumatic brain injury (sTBI) and SCI may require a delicate balancing act, with an emphasis on maximizing outcomes and minimizing harms.

  
  
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  Cohorting patients with neurocritical illness in specialized care settings may benefit survival.

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