|
Emergency
Introduction
A small number of neurosurgical diseases at some point in their history may require treatment within a few minutes or hours to avoid permanent neurologic deficit or death.
Pathophysiologic (disease) process whose natural history without intervention leads to irreversible nervous system injury or death.
Mechanisms of brain/spine/nerve injury that can lead to irreversible injury or death include: mechanical forces (pressure, shearing, cutting, etc.), perfusion insufficiency, oxygenation, and metabolism (secondary injuries result from abnormalities and loss of control of molecular biologic pathways -- metabolism, transmitter production and release, ...).
Mechanical - Perfusion - Oxygen - Metabolism
Mechanical (pressure, herniation)
Mechanical
distortion by pressure or pulling on tissue.
Brainstem compression by the uncus (deepest part of temporal lobe, closest to the brainstem) is a frequent result of brain swelling. In the pathophysiology of many neurosurgical diseases herniation accompanies increased intracranial pressure (ICP). However it is important to note that herniation and increased ICP are not identical. Impending cerebral herniation is an Emergency. Once herniation progresses to the point that the temporal uncus pushes against and distorts the midbrain the injury to the brain is usually irreversible. If the time that impending herniation is recognized to the time of intervention is more than a few minutes herniation may progress to the point of irreversible neurologic deficit or death. Hence: Emergency. Patients with impending herniation have a treatable condition. Decreasing the volume of cerebral tissue can in some cases reverse the direction of uncus movement from towards to away from the brainstem. Patients who otherwise would die from brainstem compression may be “salvageable” (saving life but not neurological function).
Mechanical - Perfusion - Oxygen - Metabolism
Cerebral perfusion pressure (CPP) is the pressure the blood is under as it enters the cerebral arteries. This pressure is necessary to keep oxygenated blood reaching the brain cells.
Cerebral perfusion pressure CPP = MAP – ICP
When blood flow to the brain decreases so does delivery of oxygen and glucose to neurons that depend on these to make energy, generate electrical signals, and metabolize.
Mechanical - Perfusion - Oxygen - Metabolism
Anoxia for more than a few (3-4) minutes results in death (irreversible) of neurons. When large numbers of neurons located and working together as in a brain nucleus (hypothalamus, thalamus, basal ganglia, cranial nerve, etc.) are anoxic and die the function they performed is irreversibly lost. Red blood cells contain hemoglobin that carries oxygen to nervous (and all other) tissues. In order for sufficient oxygen to reach brain, spinal cord, and nerve tissue there must be hemoglobin to carry it, and flow (resulting from contraction of the heart propelling blood forward under pressure) into the intracranial compartment.
Mechanical - Perfusion - Oxygen - Metabolism
Shifts in metabolic pathways in stressed (most frequently hypoxic) brain cells generate toxins (substances that kill cells and tissue).. Metabolism Enzyme activation – calcium. Channels. Second messenger. Acidosis Accumulation of hydrogen ions interferes with metabolism and energy transmission and. Extreme acidosis is toxic to all cells of the central nervous system.
2. Time Window Time course of disease evolution so rapid that without intervention within minutes to hours (arbitrarily for this discussion: 1 hour) irreversible neurologic injury and/or death will result.
When function- or life-saving intervention must be within a narrow time window on the order of minutes up to an hour, there is an emergency.
When function- or life-saving intervention must be within a wider time window on the of several up to 24 hours, there is an urgency.
3. Intervention Availability of disease-specific treatment (intervention) that can arrest pathophysiologic destruction and prevent death.
Surgical Drain fluid Remove brain tissue Remove solid or liquid blood clot Remove brain tissue mixed with clot
Medical Diuresis (Mannitol/Lasix) Hyperventilation (alkalosis) Steroids
Other Head elevation
Non-Emergencies
A gunshot wound to the head (even with brain coming to the surface) is not an emergency in the absence of an extra-axial hematoma or other mass-occupying lesion. |
|
|
||||||||||||||||||||||||
|
|
||||||||||||||||||||||||||
