Page 789 - Clinical Small Animal Internal Medicine

69 Central Nervous System Trauma 757

Diazepam (0.5–2.0 mg/kg) can be given intravenously trauma patients and recently in a veterinary patient.
VetBooks.ir to treat seizures. Additionally, phenobarbital (2–3 mg/ Hypothermia can be achieved by cooling a patient to a
kg) may also be given intravenously or intramuscularly and
rectal temperature of 32–35 °C, which reduces cerebral
continued parenterally following a loading dose (18–24
decreased CBF and ICP. However, reduction of core
mg/kg over a 24–48‐hour period) if necessary. Recently, the metabolic rate and oxygen consumption, leading to
use of intravenous levetiracetam (20–60 mg/kg) has been body temperature carries risks and may lead to the
described for emergency seizure treatment as it may be development of cardiac arrhythmias, coagulopathies,
effective for up to eight hours without causing much electrolyte disturbances, hypovolemia, and insulin resist-
sedation and without needing hepatic metabolism. ance. Coma may also be induced using barbiturates, but
Refractory seizures at the time of head trauma may this prevents neurologic evaluation and requires
require additional therapy such as a continuous infu- induction of mechanical ventilation.
sion of diazepam (0.5–1.0 mg/kg/h) or propofol (4–8
mg/kg bolus to effect followed by 1–5 mg/kg/h CRI). Surgery
Some patients may require long‐term management of Surgical intervention is reserved for patients that do
seizure activity with antiepileptic medications. However, not improve or deteriorate despite aggressive medical
if maintenance therapy is continued beyond seven days therapy. Advanced imaging (CT or MRI) is necessary
and seizure activity is not noted over a 3–6‐month for surgical planning and is also reserved for similar
period, antiepileptic treatment may be slowly withdrawn. patients. Surgery may be indicated to remove hematomas,
Therapy should be reinstituted if seizures return with an relieve intracranial pressure, or address skull fractures.
unacceptable frequency. Ventricular obliteration and mass effect identified on
advanced imaging should be considered strong indica-
tors for surgical treatment in any animal which does not
Refractory Head Trauma
improve with medical therapy.
Failure of fluid therapy, oxygenation and ventilation strat- Extraaxial hematomas can be removed through a
egies, and osmotic diuretics to stabilize the patient and/ generous craniectomy. Surgery in these patients may
or improve the neurologic status significantly warrants lead to significant hemorrhage requiring blood transfu-
radical therapy and such cases should be considered for sions. Removal of hematomas may exacerbate bleeding
advanced imaging such as MRI. The treatments discussed as compression of bleeding vessels is removed, leading
here have not been evaluated in veterinary medicine in to reaccumulation of blood even after surgery. Intraaxial
terms of their efficacy and remain controversial or hematomas are typically managed conservatively. Surgery
unproven in human head trauma. may be indicated in a deteriorating patient with subacute
enlargement of a previously small hematoma.
Hyperventilation Hemorrhagic parenchymal contusions can cause
Hyperventilation has been suggested as a method of severe neurologic signs, depending on their location.
quickly lowering ICP. Hypercapnia causes vasodilation They are typically managed conservatively. Cerebellar
and subsequent increases in ICP so hypoventilation contusions causing fourth ventricle and brainstem com-
should be avoided. Mechanical or manual ventilation pression are an indication for surgery in humans in an
may be used to lower partial pressure of carbon dioxide effort to reduce continued compression and the risk of
in the arterial blood (PaCO 2 <35 mmHg) to reduce ICP herniation. Surgery for cerebellar contusions may be
in deteriorating patients responsive to no other treat- indicated prior to neurologic deterioration because these
ment and with no surgical lesions. The prolonged use of signs are less reversible with conservative management.
hyperventilation should be avoided as reduction in cer- Intracranial hypertension should be treated initially
ebral PaCO 2 less than 30–35 mmHg causes vasocon- with the therapies discussed previously. However, in
striction which ultimately leads to decreased cerebral about 20% of human head trauma patients, additional
blood flow and ischemia. decompressive surgery is also required. Surgery is bene-
ficial in deteriorating patients before irreversible brain
Hypothermia damage occurs indicated by bilateral pupillary dilation.
At this time, hypothermia is an experimental treatment Surgical intervention for intracranial hypertension
which has not been validated in veterinary medicine and involves creation of a large craniectomy over the most
remains controversial in human medicine. Following affected site followed by a durectomy or duraplasty to
trauma, the cerebral metabolic rate may be increased, allow the brain to swell.
leading to exacerbating secondary effects. Controlled Typically, skull fractures do not require surgical interven-
hypothermia and induction of coma reduce cerebral tion. However, significantly contaminated, comminuted
metabolic rate and have been reported in human head fractures may require surgical debridement, especially if