Department of Health in New York and Hyperventilation in Severe Traumatic Brain Injury
Current Statewide Basic Life Support Adult and Pediatric Treatment Protocols stipulate that hyperventilation, at a rate of 20 breaths per minute in an adult and 25 breaths per minute in a child, should be employed in major trauma whenever a head injury is suspected, the patient is not alert, the arms and legs are abnormally flexed and/or extended, the patient is seizing, or has a Glasgow Coma Scale of less than 8. The State Emergency Medical Advisory Committee has reviewed these protocols, and concludes, on the basis of recent scientific evidence, that in the patient with severe traumatic brain injury (Glasgow Coma Scale score < or = to 8) following open or closed head injury, aggressive hyperventilation should be avoided in the prehospital setting, unless there are active seizures or signs of transtentorial herniation. Although hyperventilation was used throughout the 1970s and 1980s in the acute management of severe traumatic brain injury, its use has undergone critical reappraisal in recent years. This has occurred following the publication of several reports linking excessive hyperventilation (PaCO2 < 25 mm Hg) to cerebral ischemia, as well as a large prospective randomized study which failed to demonstrate any benefit, but instead demonstrated a slight detriment, to head injured adult patients ventilated to achieve a PaCO2 of 25 mm Hg versus head injured adult patients ventilated to achieve a PaCO2 of 35 mm Hg. In 1995, the Brain Trauma Foundation, in collaboration with the American Association of Neurological Surgeons and the Joint Section on Neurotrauma and Critical Care, published evidence-based Guidelines for the Management of Severe Head Injury, which call for moderation in the use of hyperventilation in the acute management of severe traumatic brain injury. The State Emergency Medical Advisory Committee has reviewed these guidelines, and the scientific evidence on which they are based, and endorses the guidelines pertaining to initial resuscitation as an appropriate standard of prehospital care for patients with severe traumatic brain injury.
With respect to integration of brain-specific treatments into the initial resuscitation of the severe head injury patient, the Guidelines state: "The first priority for the head-injured patient is compete and rapid physiologic resuscitation. No specific treatment should be directed at intracranial hypertension in the absence of signs of transtentorial herniation or progressive neurological deterioration not attributable to extracranial explanations. When either signs of transtentorial herniation or progressive neurological deterioration not attributable to extracranial explanations are present, however, the physician should assume that intracranial hypertension is present and treat it aggressively. Hyperventilation should be rapidly established. The administration of mannitol is desirable, but only under conditions of adequate volume resuscitation." With respect to resuscitation of blood pressure and oxygenation, the Guidelines state: "Hypotension (systolic blood pressure < 90 mm Hg) or hypoxia (apnea or cyanosis in the field or a Pa02 < 60 mm Hg) must be scrupulously avoided, if possible, or corrected immediately." With respect to use of hyperventilation in the acute management of severe traumatic brain injury, the Guidelines state: "The use of prophylactic hyperventilation (PaCO2 < 35 mm Hg) therapy during the first 24 hours after severe TBI should be avoided because it can compromise cerebral perfusion during a time when cerebral blood flow (CBF) is reduced." With respect to acute neurologic deterioration or refractory intracranial hypertension, the Guidelines state: "Hyperventilation therapy may be necessary for brief periods when there is acute neurological deterioration, or for longer periods if there is intracranial hypertension refractory to sedation, paralysis, cerebrospinal fluid (CSF) drainage, and osmotic diuretics."
Thus, normal ventilation is now recognized as the appropriate standard of care for initial management of severe traumatic brain injury. Yet, it is difficult for prehospital personnel to know whether they are achieving normal ventilation, particularly when using a bag and mask. To avoid this problem, prehospital personnel are advised to utilize strategies that maximize oxygen delivery and minimize inadequate ventilation. The State Emergency Medical Advisory Committee believes that these goals can best accomplished by utilizing ventilatory rates that are likely to avoid both hyperventilation and hypoventilation. It is assumed that the recommended rates for assisted ventilation contained in the 1992 Edition of the Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care of the American Heart Association, 12 breaths per minute (1 breath every 5 seconds) for an adult and 20 breaths per minute (1 breath every 3 seconds) for a child 8 years of age or less, are sufficient to support adequate ventilation. Thus for adults with severe traumatic brain injury (Glasgow Coma Scale score < or = to 8), the assisted ventilatory rate should be 12 breaths per minute (1 breath every 5 seconds), while for children 8 years of age or less with severe traumatic brain injury (Glasgow Coma Scale score < or = to 8), the assisted ventilatory rate should be up to 20 breaths per minute (1 breath every 3 seconds). Only if active seizures, or signs of transtentorial herniation such as fixed or asymmetric pupils, neurologic posturing (decerebrate or decorticate), Cushing's reflex (hypertension and bradycardia), periodic breathing (Cheyne-Stokes, central neurogenic, ataxic breathing), or neurologic deterioration (further decrease in Glasgow Coma Scale score of 2 or more points), are present may hyperventilation be considered, and ventilatory rates increased to 20 breaths per minute in adults and to 25 breaths per minute in children. The Statewide Basic Life Support Adult and Pediatric Treatment Protocols have been modified to reflect this change, and Regional Emergency Medical Advisory Committees, and regional, system, and service medical directors are advised to modify local protocols, policies, and procedures accordingly.