craniotomy
*Osmotic diuretics and hypertonic saline* have also been used to reduce increased ICP.
•In the presence of an intact blood-brain barrier, hyperosmolar therapy is used to draw water
from brain tissue into the intravascular compartment.
○The direction of flow is from the hypoconcentrated tissue to the hyperconcentrated cerebral
vasculature.
•Most widely used diuretic:*Mannitol and hypertonic saline (3-23.4%)* are most often used
○Careful attention must be paid to body weight and fluid and electrolyte stability.
Keep serum osmollity: 300-320
Hypernatremia& hypokalemia with too much osmotic agents
Montior CVP to prevent hypovolemia - ANS-Intercranial HTN
Hyperosmolar therapy
•Hourly monitoring of fluid intake and output facilitates early identification of fluid imbalance.
○ Urine specific gravity must be measured if DI is suspected.
○ Fluid restriction may be ordered as a routine measure to lessen the severity of cerebral
edema or as treatment for the fluid and electrolyte imbalances associated with SIADH. -
ANS-Fluid management
postcraniotomy
○ Fluid imbalance in the postcraniotomy patient usually results from a disturbance in production
or secretion of antidiuretic hormone (ADH)- vasopressin and fluid retain.
○ Unabated renal water loss even when blood volume is low and serum osmolality is high. This
condition is known as diabetes insipidus (DI).
○ The syndrome of inappropriate antidiuretic hormone (SIADH) manifests as inappropriate water
retention with hyponatremia in the presence of normal renal function. - ANS-Fluid Imbalance
post-craniotomy
A craniotomy is performed to gain access to portions of the central nervous system (CNS) inside
the cranium, usually to allow removal of a space-occupying lesion such as a brain tumor.
The neurosurgeon must select a route that also produces the *least amount of disruption to the
intracranial contents.* - ANS-Craniotomy
Agents used to reduce metabolic demands include the use of:
○Benzodiazepines such as midazolam and lorazepam: sedate
○ Intravenous sedative-hypnotics such as propofol
○ Opioid narcotics such as fentanyl and morphine:pain
○Neuromuscular blocking agents such as vecuronium and atracurium: must have ICP
monitoring in place and use with sedation.
if these all fail barbiturate therapy is considered:pentobarbitol/thiopental - ANS-Intercranial HTN
, Control of Metabolic demands
As the ICP rises, the relationship between volume and pressure changes,
Small increases in volume may cause major elevations in ICP
• Intracranial hypertension occurs when ICP is greater than 20 mm Hg. - ANS-Intercranial HTN
Volume pressure curve
Cerebral blood flow (CBF) corresponds to the metabolic demands of the brain and is normally
50 mL/100 g of brain tissue/min.
•The normal brain has a complex capacity to maintain constant CBF, despite wide ranges in
systemic arterial pressure—an effect known as
autoregulation
•A MAP of 50 to 150 mm Hg does not alter CBF when autoregulation is functioning
•Factors other than arterial blood pressure that affect CBF are conditions that result in acidosis,
alkalosis, and changes in metabolic rate.
○Conditions that cause acidosis (e.g., hypoxia, hypercapnia,
ischemia) result in cerebrovascular dilation.
○ Conditions causing alkalosis (e.g., hypocapnia) result in cerebrovascular constriction.
•Carbon dioxide, which affects the pH of the blood, is a potent vasoactive
substance.
○Hypercapnia leads to cerebral vasodilation, with increased cerebral
blood volume,
○ Hypocapnia leads to cerebral vasoconstriction and a reduction i - ANS-Intercranial HTN
Cerebral blood flow and autoregulation
Common procedures include tumor resection or removal, cerebral decompression, evacuation
of hematoma or abscess, and clipping or removal of an aneurysm or AVM. - ANS-Craniotomy
Types
Complications associated with a craniotomy include *intracranial hypertension, surgical
hemorrhage, fluid imbalance, cerebrospinal fluid leak, and DVT.* - ANS-Craniotomy
Complications
Controlled hyperventilation has been an important adjunct of therapy for
the patient with increased ICP.
• The rationale employed in hyperventilation is that if the Paco2 can be reduced from its normal
level of 35 to 40 mm Hg to a range of 25 to 30 mm Hg in the patient with intracranial
hypertension, vasoconstriction of cerebral arteries, reduction of CBF, and increased venous
return will result. - ANS-Intercranial HTN
Hyperventilation
CSF drainage for intracranial hypertension may be used with other treatment modalities:
intermittent/continuous drainage systems
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