ICP

Question 1

ICP Normal Range

Answer 1

7-15 mmHg

Question 2

What is ICP?

Answer 2

-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

Question 3

Cerebral Perfusion Pressure (CPP)

Answer 3

is the difference between the systemic mean arterial pressure (MAP) minus the ICP.
CPP=MAP-ICP (normal CPP range 70-90 mmHg)

Question 4

Intracranial Compensation Goal:

Answer 4

to keep ICP w/in normal range (0-15 mmHg/cm H2O)

Question 5

Whenever there are small increases in intracranial volume and/or pressure the brain will attempt to:

Answer 5

-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

Question 6

Flow Chart for IICP (Increased ICP)

Answer 6

1. Monroe-Kellie Hypothesis
2. CPP=MAP-ICP
3. Autoregulation
4. Herniation Syndrome

Question 7

Monroe-Kellie Hypothesis

Answer 7

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.

Question 8

Increased systemic blood flow=

Answer 8

cerebral arteries constrict

Question 9

Decreased systemic blood flow=

Answer 9

cerebral arteries dilate

Question 10

CBF regulation is also affected by:

Answer 10

INCREASED PaCO2 levels = cerebral arteries dilate

DECREASED PaCO2 levels = cerebral arteries constrict

Question 11

2 types of pressure regulation

Answer 11

one above the neck
one below the neck

Question 12

Autoregulation

Answer 12

Adequate cerebral blood flow (CBF) is maintained by constriction or dilation of the cerebral arteries in response to increased or decreased systemic blood flow

Question 13

Pressure Volume Connection

Answer 13

-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

Question 14

Causes of Increased ICP

Answer 14

-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

Question 15

CLINICAL MANIFESTATIONS OF IICP

Answer 15

-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

Question 16

Clinical Manifestations of ALOC

Answer 16

-decreased wakefulness
-decreased attention to environment
-confusion
-disorientation
-agitation
-poor memory
-decreased ability to carry out ADLs
-decreased mobility
-incontinence
-hallucinations
-delusions
-illusions

Question 17

Decortication (abnormal flexion)

Answer 17

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)

Question 18

Decerebration (abnormal extension)

Answer 18

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

Question 19

Medical Tx for ICP

Answer 19

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

Question 20

Surgical Interventions

Answer 20

brain surgery (ventriculostomy) - drill hole in brain and suck out fluids

Question 21

ICP Monitoring Placements

Answer 21

Intraventricular
Subarachnoid
Subdural
Parenchymal
Epidural

Question 22

Intraventricular Catheter System aka External Ventricular Drain [EVD]

Question 23

Intracranial pressures are measured at the:

Answer 23

-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.