Page 787 - Clinical Small Animal Internal Medicine

69 Central Nervous System Trauma 755

into the epidural, intraaxial, or intraventricular space. caution as without concurrent administration of crys-
VetBooks.ir ICP monitoring is frequently pursued in human head talloid solutions, hypertonic and colloid solutions can
lead to dehydration. Other benefits of hypertonic fluids
trauma patients, but may have its limitations in veterinary
patients. ICP monitoring is not without risks and may
lead to development of edema, hemorrhage, parenchymal include the ability to improve cardiac output, restore
normovolemia, and reduce inflammation after trauma.
damage, and infection. Hypertonic saline may be preferred in hypovolemic,
hypotensive patients with increased ICP.
Hypertonic saline improves cerebral perfusion pressure
Treatment of Head Trauma Patients
and blood flow by rapidly restoring intravascular blood
Treatment strategies should be directed toward both volume. Additionally, the high sodium content of
systemic and neurologic stabilization in an effort to min- hypertonic saline draws fluid from the interstitial and
imize secondary damage. Several aspects of treatment intracellular spaces, subsequently reducing intracranial
exist. Systemic stabilization involves correction of sys- pressure. Contraindications to administration of hyper-
temic shock and respiratory abnormalities with fluid tonic saline include systemic dehydration and hyperna-
therapy and oxygen therapy/management of ventilation tremia. Hypertonic saline only remains within the
respectively. The second aspect of treatment involves vasculature for about one hour so it should be followed
measures to reduce elevations in intracranial pressure by colloids to maximize its effects. A dose of 5–6 mL/kg
and cerebral metabolic rate. Finally, some animals (dogs) and 2–4 mL/kg (cats) of 7.5% NaCl should be
require surgical intervention because of lack of improve- given over 5–10 minutes.
ment or a declining neurologic status. Colloids (i.e., Hetastarch, Dextran‐70) allow for low‐
Although once used as a treatment following head volume fluid resuscitation, especially if total protein con-
trauma, corticosteroids are no longer recommended in centrations are below 50 g/L or 5 g/dL. These fluids
head trauma patients. Their use has been extensively also draw fluid from the interstitial and intracellular
evaluated in people and has shown no beneficial effect spaces, but have the added benefit of staying within the
and may even result in worse morbidity and mortality intravascular space longer than crystalloids. Hetastarch
rates. Detrimental effects of corticosteroids include is typically given at 5–6 mL/kg boluses in dogs and
immunosuppression, hyperglycemia, and gastrointesti- 2–4 mL/kg in cats over 5–10 minutes, with frequent
nal disturbances. patient reevaluation. A total dose of 20 mL/kg/day may
be given. In addition to volume resuscitation, oxygen‐
Fluid Therapy carrying capacity should be considered, especially if the
The goal of fluid therapy of the head trauma patient is to packed cell volume <30%. The use of oxyglobin and other
restore a normovolemic state. It is deleterious to dehy- hemoglobin‐based oxygen carriers has not been well
drate an animal in an attempt to reduce cerebral edema. evaluated in head trauma but initial studies suggest that
Aggressive fluid therapy and systemic monitoring are they could play a valuable role.
required to ensure normovolemia to maintain adequate Systemic blood pressure may require additional treat-
cerebral perfusion pressure. ment to maintain adequate cerebral perfusion pressure.
Crystalloid, hypertonic, and colloid fluids should be A mean arterial pressure of 80–100 mmHg should be
given concurrently to help restore and maintain blood the target. Hypotension should initially be treated with
volume following trauma. Crystalloids are usually given fluid resuscitation but persistent hypotension may
initially for the treatment of systemic shock. These bal- require treatment with vasoactive agents (i.e., dopamine
anced electrolyte solutions may be given at shock doses 2–10 μg/kg/min). Additionally, systemic hypertension
(90 mL/kg for dogs, 60 mL/kg for cats). Typically, it is may occur as a sequela to intracranial hypertension as a
recommended that the shock dose be given in fractions result of the Cushing reflex. Systemic hypertension sec-
starting with one‐third to one‐fourth of the calculated ondary to ICP elevation should be treated by aggres-
volume, frequently reassessing the patient for normaliza- sively treating elevated ICP; the use of additional drugs
tion of mean arterial blood pressure, mentation and central to modulate the blood pressure should be avoided unless
venous pressure, if monitored, and giving additional all attempts to lower ICP have been exhausted.
fractions if needed. Unfortunately, crystalloid solutions Head trauma patients should be positioned to maxi-
will extravasate into the interstitium within one hour of mize arterial circulation to the brain and improve venous
administration, requiring additional fluid resuscitation. drainage. This goal is best achieved by elevating the
Hypertonic and colloid fluid therapy can rapidly restore animal’s head at a 30° angle. It is important to ensure the
blood volume using low‐volume fluid resuscitation; jugular veins are not occluded and that no restrictive
additionally, colloids remain in the vasculature longer collars are placed around the neck, which would elevate
than crystalloid fluids. These fluids should be used with ICP.