ICP Flashcards
ICP Normal Range
7-15 mmHg
What is ICP?
-Refers to the pressure of the CSF within the CNS.
-Is closely related to brain perfusion, therefore cerebral blood flow is dependent upon ICP.
-Tx for increasing ICP occurs when ICP > 20mmHg
-Maintenance of CPP may be considered more important
Cerebral Perfusion Pressure (CPP)
is the difference between the systemic mean arterial pressure (MAP) minus the ICP.
CPP=MAP-ICP (normal CPP range 70-90 mmHg)
Intracranial Compensation Goal:
to keep ICP w/in normal range (0-15 mmHg/cm H2O)
Whenever there are small increases in intracranial volume and/or pressure the brain will attempt to:
-shunt CSF to the subarachnoid space
-increase CSF absorption in the venous sinus
-decrease CSF production
-decrease blood volume to the brain by altering cerebral blood flow
Flow Chart for IICP (Increased ICP)
- Monroe-Kellie Hypothesis
- CPP=MAP-ICP
- Autoregulation
- Herniation Syndrome
Monroe-Kellie Hypothesis
Because the skull is a rigid compartment, once compensatory mechanisms are exhausted, an increase in the volume of one of the intracranial components (BRAIN, BLOOD, CSF) must be accompanied by a reciprocal decrease in another component, or pressure will rise.
Increased systemic blood flow=
cerebral arteries constrict
Decreased systemic blood flow=
cerebral arteries dilate
CBF regulation is also affected by:
INCREASED PaCO2 levels = cerebral arteries dilate
DECREASED PaCO2 levels = cerebral arteries constrict
2 types of pressure regulation
one above the neck
one below the neck
Autoregulation
Adequate cerebral blood flow (CBF) is maintained by constriction or dilation of the cerebral arteries in response to increased or decreased systemic blood flow
Pressure Volume Connection
-An increase in blood volume can develop when there is vasodilation of cerebral vessels or obstruction of venous outflow
-Excess production, decreased absorption, or obstructed circulation of CSF creates the potential for an increase in CSF pressure
-Compliance refers to the ability of the brain to accommodate changes in intracranial volume w/out significant changes in ICP
Causes of Increased ICP
-Increased ICP is defined as a sustained elevation in pressure above 20 mm Hg
-Factors to consider w/ increased ICP are causes for the increase in ICP and the rate at which the ICP increases
-COMPLIANCE refers to the ability of the brain to accommodate changes in intracranial volume w/out significant changes in ICP
CLINICAL MANIFESTATIONS OF IICP
-early to late presentation
-projectile vomiting
-Cushing’s response: rising systolic pressure, widened pulse pressure > 50 mm Hg, slowing heart rate [impacts medulla oblongata]
(bradypnea, bradycardia, hypertension)
-Cushing’s triad: as above but now incl. slowed respirations
-absent thermoregulation
-positive Babinkski’s reflex: on an adult - take a pen or key along foot to big toe and toe would fan out
Clinical Manifestations of ALOC
-decreased wakefulness
-decreased attention to environment
-confusion
-disorientation
-agitation
-poor memory
-decreased ability to carry out ADLs
-decreased mobility
-incontinence
-hallucinations
-delusions
-illusions
Decortication (abnormal flexion)
rigidly flexed arms and wrists; fisted hands; occurs in upper brainstem
-pt can come out of it
-implies severe damage to the brain w/ immediate need for medical attention
-indicates damage to the corticospinal tract (pathway btwn brain and spinal cord)
Decerebration (abnormal extension)
rigidly, rotated inward extended arms w/ flexed wrists and fisted hands; occurs in lower brain stem
-harder for the pt to come out of it
Medical Tx for ICP
only for adults:
-hyperventilation (create resp alkalosis – arterial vasoconstriction)
-hypothermia (cooling down metabolic processes from head to toe)
-fluid restriction
-use IV 0.9% NS or LR (do not give D5W bc it can increase ICP)
-elevate HOB 25-30 degrees (decrease blood return to the brain. do not lie flat or it will increase ICP)
-diuretics (osmotic v loop- gets rid of excess water)
-corticosteroids (decrease inflammation if that’s causing ICP)
-barbiturate coma
Surgical Interventions
brain surgery (ventriculostomy) - drill hole in brain and suck out fluids
ICP Monitoring Placements
Intraventricular
Subarachnoid
Subdural
Parenchymal
Epidural
Intraventricular Catheter System aka External Ventricular Drain [EVD]
Intracranial pressures are measured at the:
-Lateral Ventricles
-The ventriculostomy is leveled at the Foramen of Monro, tragus or external auditory canal. Always check hospital policy or make sure the surgeon writes an order for a different leveling site. Important to stick to one site otherwise pressure values change according to the level of the transcducer.
