1. Review military medical advances and determine their importance for civilian trauma care.

2. Compare challenges faced during civilian disasters with challenges seen on the battlefield (specifically, acute pain relief and multimodal analgesia).

3. Review the epidemiology and pathophysiology of traumatic brain injury.

4,. Describe the role of anesthesia care in resuscitation of the injured brain.

5. Discuss brain protection after closed head injury.

Transporting the Trauma Patient
Chester C. “Trip” Buckenmaier III, MD, Assistant Professor of Anesthesiology, Uniformed Services University of the Health Sciences; Chief, Army Regional Anesthesia and Pain Management Initiative; and Assistant Chief, Anesthesia and Operative Services, Walter Reed Army Medical Center, Washington, DC

Civil War: General “Stonewall” Jackson among first to benefit from use of field ambulance designed to carry casualties from battlefield to hospital (previously, wounded soldier lay on battlefield, sometimes for days, until he could be dragged to safety); those transported by field ambulance also received analgesia (eg, whiskey, morphine); Jackson also received ether for amputation of arm, but succumbed to pneumonia and died shortly thereafter; his response to analgesia on battlefield, “what an infinite blessing”

Modern military: morphine—used for 19th century pain control; still important for pain management today, but failing as monotherapy; morphine suboptimal for 21st century evacuation realities; current evacuation standards—C- 141 transport aircraft probably reason for <10% died-of-wounds rate; no military in history has achieved this success rate; penetrating wound of head, chest, or abdomen sustained during current conflict “really not an issue for military anesthesiologist, because [soldier] usually dead”; advances in body armor and “6000-mile-long [intensive care unit] ICU that we’ve built” has allowed survival stories from soldiers who otherwise would have been killed in action; environment still difficult—crowded, vibrating, dark, noisy, and lacks monitoring capability; usually one nurse and 2 flight technicians managing 30 to 60 individuals per flight; in previous conflicts, nurse remained by patient and able to administer morphine to soldier in pain; if too much morphine administered, nurse able to provide necessary airway or remedy situation; today, soldier seen by hundreds of health care providers in short time; speaker’s experience—after deployment to Iraq in 2003, speaker quickly recognized that many technologies and techniques learned from civilian counterparts and colleagues not being utilized in war environment; desperately needed because of new evacuation reality

Importance of military medical accomplishments in civilian practice: battlefield formerly foreign “now in your backyard”; natural disasters can strike without warning; transportation infrastructure in cities can be attacked relatively easily; Katrina disaster indicates that our ability to withstand assaults to infrastructure “relatively miniscule”; during manmade or natural disaster, anesthesia provider may be called on to “do the things that we do in the military”; anesthesia response, as it relates to pain, not only can influence better medical response to natural disaster, but can have far-reaching impact on trauma victims (ie, far into recovery)

Challenges during disasters: extremes of weather; terrain issues; facility and equipment considerations; logistics (eg, moving E cylinder of O2 ); speaker and fellow soldiers believe lives saved by avoiding general anesthesia and using 21% O2 ; these issues have real-world impact on response to disaster; number of victims in civilian trauma relatively manageable (eg, 3-10 victims at one time), and large resource base available (eg, electricity at wall outlet, hot and cold running water); “we wrap ourselves in a cocoon of technology, almost to the point where it’s difficult to hurt our patients”

Challenges on battlefield: in contrast, battlefield casualties may include 50 soldiers at one time; planning for casualties competes with generals concerned about “beans and bullets”; caring for wounded tends to be afterthought; good news from current conflict that United States military known for caring for wounded soldiers; have good chance for survival; enemy also knows United States military will care for them if injured on battlefield

Personal safety issues: if weapon of mass destruction (WMD) used, plan required to prevent contamination of all hospital personnel

Pain perspective: acute pain service, particularly at Walter Reed Army Medical Center, driving force behind accomplishments in military pain management; anesthesia provider best available person to manage acute pain in hospital, particularly after trauma; also, with expertise in regional anesthesia, anesthesia provider best able to manage trauma in austere environment; advances may affect recovery by, eg, reducing posttraumatic stress disorder, improving return to duty, and improving management of prosthetics; effective acute pain management likely prevents issues of phantom limb pain and complex regional pain syndrome (CRPS); effective acute pain management is prophylactic; changes that occur in central nervous system lead to chronic pain issues, contribute to depression and posttraumatic stress, and prevent soldier from recovering faster and resuming role as productive member of society

Multimodal analgesia: novel concept for military; morphine used for ≈200 yr; now being adopted, due to advances in technology and forward-thinking health care providers who have worked with Walter Reed’s Army Regional Anesthesia and Pain Management Initiative and Military Advanced Regional Anesthesia and Analgesia Group; regional anesthesia has elements necessary for battlefield, ie, leaves light logistics “footprint,” requires minimally invasive equipment to perform well, and provides days to weeks (not hours) of analgesia

Changes in battlefield pain relief: peripheral nerve stimulator used with every block, regardless of whether ultrasonography (US) available; in austere conditions, easier to obtain stimulator than US; if interested in regional anesthesia, do not forget everything learned, including paresthesia techniques; microprocessor-driven technology also useful; can serve as patient-controlled analgesia (PCA) device and pump for epidural techniques, and can be used for peripheral nerve blocks; catheters in place for weeks; ability to redose catheter and take soldier back to surgery important

Acute pain service: use regional anesthesia techniques as foundation upon which to build; use other narcotics, gabapentin, and nonsteroidal anti-inflammatory drugs; internet-based system being explored that will track acute pain patients from battlefield to hospital in Germany (recently through first approval phase); special forces in Afghanistan given fluoroquinolone, cyclooxygenase-2 (COX-2) inhibitor, and acetaminophen (eg, Tylenol) and instructed to take tablets if wounded; useful for disaster situation in which soldier injured and in pain; adequate pain management will augment medical response

New technologies: iontophoresis; fentanyl lollipops; infusion and monitoring technologies (eg, pulse oximetry)

Closed Head Injury: Anesthetic Considerations
C. Thomas Wass, MD, Associate Professor of Anesthesiology, Mayo College of Medicine, Rochester, MN

Case: previously healthy, 25-yr-old man, extricated from driver’s side of car after high-speed motor vehicle accident; report of steering wheel deformity and starred windshield; patient semiconscious, combative, has Glasgow Coma Scale (GCS) score of 9, exhibits midline facial fractures and bilateral black eyes, and hyperdynamic with labored tachypnea; concerns include integrity of mediastinal and thoracic cavity structures, traumatic brain injury (TBI), and spinal cord injury; trepidation about safely securing airway in combative patient with midline facial fractures

Epidemiology: 1.4 million Americans annually sustain TBI; 1.1 million treated and released from emergency department, 230,000 hospitalized, and ≈50,000 die as result of injuries; leading cause of mortality in individuals <45 yr of age; annual cost $60 billion in United States alone; TBI can be classified by mechanism of injury (penetrating vs blunt), GCS score (<9 considered coma), or cerebral pathology

Cerebral pathology and pathophysiology: primary—occurs at time of impact; biomechanical dissipation of energy onto skull and underlying brain, resulting in structural and functional changes; not modifiable; secondary—results from systemic or intracranial perturbations that occur minutes, hours, or days after initial trauma; anesthesia personnel can significantly intervene to improve patient outcome; systemic causes include anything that limits O2 delivery to brain, hyperglycemia, and fever; intracranial (IC) causes include increased IC pressure (ICP), brain edema, IC hematoma, seizure, vasospasm, or meningitis; ultimate goal to prevent or mitigate secondary neurologic injury

Role of anesthesia care

Airway: regardless of technique or route of tracheal intubation, head-injured patient should be treated as though concomitant cervical spine injury present; in-line stabilization (rather than in-line traction) currently proposed; change in practice stems from concerns about iatrogenic spinal cord injury associated with in-line traction (eg, stretch-related or compression-related injury to spinal cord); safety of routine use of nasal intubation in presence of maxillofacial injury another concern; severe midline facial fractures may be associated with anterior skull base (eg, cribriform plate of ethmoid bone) injury; presents clinically as bilateral periorbital ecchymosis and possibly cerebrospinal fluid (CSF) draining from nose (rhinorrhea); fractures in petrous portion of temporal bone present clinically as postauricular ecchymosis and possibly CSF draining from ear (otorrhea); nasogastric, nasopharyngeal, and nasotracheal tubes may traverse fracture site and enter cranial vault, resulting in hemorrhage, meningitis, cerebritis, or frank neurologic deficit (including neurogenic death); consequently, in presence of severe maxillofacial or known anterior skull base fracture, prudent to avoid routine nasotracheal intubation

Breathing: decreases in ICP correspond to decreases in cerebral blood volume; despite this response, aggressive hyperventilation has been cornerstone for managing severe TBI for >20 yr; however, positron emission tomography (PET) studies indicate aggressive hyperventilation may be associated with iatrogenic ischemia; in absence of trials to evaluate direct effect of hyperventilation on patient outcome, Brain Trauma Foundation recommends avoiding arterial CO2 tension (PaCO 2 ) <25 mm Hg; if using jugular bulb catheter, titrate PaCO 2 to keep jugular venous O2 saturation >60%; if not using jugular bulb catheter, hyperventilate to 30 to 35 mm Hg

Circulation: systemic mean arterial blood pressure (MAP) main determinant of cerebral blood flow (CBF); under normal conditions, autoregulation maintains CBF at near-constant level over wide range of cerebral perfusion pressures (CPPs; usually 50-150 mm Hg); however, in setting of TBI or ischemia, autoregulation likely impaired (in certain regions or in entire brain); if treatment overly aggressive, vasogenic edema may result; if not aggressive enough, brain ischemia may result; several clinical trials suggest CPP of 60 to 70 mm Hg may be critical threshold determining patient outcome; when CPP decreases below this level, mortality reportedly increases 20% for each 10-mm Hg decrease in CPP; Brain Trauma Foundation recommends maintaining MAP >80 mm Hg in attempt to preserve CPP >60 mm Hg

Brain protection

Neuroprotective anesthetics: numerous groups of investigators have evaluated neuroprotective efficacy of various anesthetics, including barbiturates, etomidate, ketamine, propofol, volatile anesthetics, lidocaine, and dexmedetomidine; of these, only barbiturates show potential clinical promise; historically touted as gold standard; shown to significantly improve histopathology and functional neurologic outcome in focal (eg, classic stroke) or incomplete global ischemia (eg, low cardiac output states), but not shown to be helpful in complete ischemia (eg, cardiac arrest); despite plethora of convincing laboratory data, only one study corroborating these findings; barbiturates effective for ICP control or in providing seizure management; considering lack of supportive human evidence, barbiturates should not be considered neuroprotective

Calcium channel blockers and N-methyl-D -aspartate (NMDA) receptor antagonists: calcium plays vital and sinister role in modulating neuronal injury, via voltage-gated and NMDA receptor channels; stimulation of these channels causes massive influx of calcium into cell, leading to free radical production, lipid peroxidation, and possibly setting into motion programmed cell death (apoptosis); calcium entry blockers and NMDA antagonists were in phase 3 clinical trials, but studies had to be discontinued due to adverse effects; these agents should not be considered neuroprotective

Temperature: since 1980s, numerous laboratory studies have reported that temperature decreases of 1°C to 6°C can significantly improve neurologic outcome in either focal or global ischemia; also shown beneficial in complete ischemia; however, clinical studies have produced conflicting reports; mild hypothermia may be beneficial if potential systemic pitfalls known; effective for treating intractable IC hypertension; future studies may focus on selective brain cooling (in which rest of body remains at or near normothermia); fever worsens neurologic outcome

Corticosteroids: “double-edged sword”; theoretically provide protective antioxidant properties; however, corticosteroids increase gluconeogenesis and glycogenolysis, decrease end-organ sensitivity to endogenous and exogenous insulin, and lead to hyperglycemia; 64% of trauma centers in United States surveyed use corticosteroids to treat TBI, despite lack of supportive laboratory or human-based data; lazaroids used clinically in 1990s, but stopped because of adverse effects; speaker’s laboratory found no benefit; according to Brain Trauma Foundation, majority of available evidence indicates steroids do not improve outcome or lower ICP in severe TBI; strong evidence that corticosteroids deleterious, thus use not recommended

Summary: resuscitation of brain begins with restoration of normal systemic physiology (eg, providing ABCs of advanced life support); in-line stabilization preferred over in-line traction during laryngoscopy; avoid routine nasal intubation in known or suspected anterior skull base fracture; moderate hyperventilation to PaCO 2 of 30 mm Hg; maintain CPP at 60 mm Hg; use of hypothermia unclear; avoid fever, hyperglycemia, and corticosteroids