Intracranial Regulation

intracranial regulation

the processes that impact the balance of intracranial contents, including the brain, blood, and cerebrospinal fluid (CSF)

brain regulation components

1. cerebrum

2. cerebellum

3. brainstem

cerebrum

responsible for higher brain functions like thought and voluntary movement

cerebellum

coordinates voluntary movements and balance

brainstem

controls vital functions like heart rate, breathing, and blood pressure

cerebral perfusion pressure (CPP)

a critical measure that ensures adequate blood flow to the brain; normal = 60-100mmHg; net pressure gradient that drives oxygen delivery to cerebral tissues; the difference between MAP and ICP; eq: CPP = MAP - ICP; determines CBF by autoregulation

autoregulation

the brain’s ability to maintain a consistent cerebral blood flow despite changes in systemic blood pressure; ensures that the brainstem receives a steady supply of oxygen and nutrients, which is critical for normal brain function

abnormal CPP levels

1. <50mmHg - cerebral ischemia

2. <30mmHg - incompatible with life

Monroe-Kellie doctrine

describes the relationship between the contents of the cranium and intracranial pressure; fluid, blood, and tissue exist in equilibrium to maintain normal ICP

vasodilation

occurs when blood pressure drops and cerebral vessels dilate to allow more blood to flow to the brain

vasoconstriction

when blood pressure increases, cerebral vessels constrict to prevent too much blood from entering the brain

pressure range

autoregulation typically functions effectively within a mean arterial pressure (MAP) range of 60-160mmHg; outside of this range, the brain’s ability to autoregulate can fail, leading to either ischemia (if pressure is too low) or IICP (if too high)

cerebral blood flow (CBF)

amount of blood needed to perfuse the brain

intracranial pressure (ICP)

normal = 5-15mmHg; abnormal = sustained pressure >20mmHg

IICP common causes

1. traumatic brain injury (TBI)

2. stroke (ischemic or hemorrhagic)

3. brain tumors

4. hydrocephalus (accumulation of CSF)

5. infections (e.g. meningitis, encephalitis)

6. cerebral edema (swelling of brain tissue)

IICP chronic causes

1. tumors

2. chronic subdural hematomas

3. abscess

4. hyrdrocephalus

Cushing’s triad

late signs of IICP;

1. bradycardia

2. HTN with widening pulse pressure

3. irregular respirations (Cheyne-Stokes)

types of cerebral edema

1. vasogenic

2. cytotoxic

3. interstitial

vasogenic cerebral edema

alteration in vascular permeability; can cause disruption of blood-brain barrier

cytotoxic cerebral edema

swelling of the cells, failure of cellular pumps to pump water out of the space

interstitial cerebral edema

rupture of the cerebrospinal fluid-brain barrier; usually a result of excess CSF fluid, CSF flow obstruction, or inability to absorb CSF

types of traumatic brain injuries (TBIs)

manage with ICP monitoring, evacuation of hematoma, and supportive care

1. concussion

2. contusion

3. diffuse axonal injury (DAI)

4. hematomas

concussion

temporary disruption of brain function; a minor head injury; sudden, brief loss of neuro function; usually resolve quickly without much intervention, but could be a sign of a more progressive, serious problem

contusion

bruising of brain tissue; major head trauma; bruising of the brain secondary to blunt trauma resulting in hemorrhage often in the frontal and temporal lobes

diffuse axonal injury (DAI)

widespread damage to brain tissue; widespread disruption of the axons in the white matter caused by high-speed acceleration-deceleration and rotational forces; immediate loss of consciousness; S/S = LOC changes, coma, extremity stiffness, increased RR, tachypnea, “neuro-storming”

hemorrhage / hematoma

most serious complication of blunt trauma; hemorrhages become space-occupying hematomas → IICP; hematomas classified according to their location

types of strokes

manage with thrombolytics for ischemic stroke, surgical intervention for hemorrhagic stroke, and management of ICP

1. ischemic

2. hemorrhagic

ischemic stroke

stroke caused by a blood clot blocking an artery to the brain

hemorrhagic stroke

stroke caused by bleeding in or around the brain

hydrocephalus

excess CSF in the brain; treated with ventriculoperitoneal (VP) shunt or external ventricular drain (EVD) to drain excess fluid

skull fractures

common, but do not act alone to cause neuro deficits; can be classified as open or as fractures of the vault or the base; significant because they indicate a high risk for developing an intracerebral hematoma

laceration

major head trauma; involves actual tearing of the brain tissue; cause bleeding or hemorrhage

types of hematomas

1. epidural

2. subdural

3. intracerebral

subdural hematoma

blood accumulates between the dura and underlying arachnoid membrane; acute or chronic; caused by closed head injury, cerebral atrophy in elderly, acceleration-deceleration injury, and chronic ETOH; S/S = headache, drowsiness, agitation, confusion

epidural hematoma

found between the dura and the skull and usually caused by skull fracture or contusion; S/S = brief LOC followed by lucidity, then rapid deterioration; drowsy → confusion → coma; hallmark sign = fixed and dilated pupil on same side as impact area

intracerebral hematoma

located directly in the brain tissue; caused by GSW, depressed skull fracture, stabbing, long history of HTN, contusions; S/S = HA, deteriorating LOC to deep coma, hemiplegia on opposite side, dilated pupil on the same side as the clot

DAI oculomotor changes

1. oculocephalic - doll’s eyes movements

2. no movement of the eyes with impaired brain

DAI oculovestibular test

cold caloric test; no eye movement (nystagmus) toward cold stimulus in ear; indicates loss of brainstem function

brain injury manifestations

1. decorticate posturing

2. decerebrate posturing

herniation

complication of IICP; displacement of brain tissue into other compartments of the brain; displaces adjacent structures; can occur in several areas / to varying degrees

MIND CRUSHED

S/S of IICP;

M - Mental status changes

I - Irregular breathing

N - Nerve changes (optic and oculomotor)

D - Decerebrate / decorticate

C - Cushing’s triad

R - Reflexes

U - Unconscious

S - Seizures

H - Headache

E - Emesis

D - Deterioration of motor function

PRESSURE

IICP nursing interventions;

P - Position HOB 30-35 degrees

R - Respiratory (oxygen and perfusion)

E - Elevated temperature

S - Systems to monitor

S - Sustaining activities avoided

U - Unconscious patient care

R - Rx (barbiturates)

E - Edema management

glasgow coma scale (GCS)

standardized system for assessing degree of consciousness impairment

GCS components

1. eye opening (1-4)

2. verbal response (1-5)

3. motor response (1-6)

GCS scoring

1. mild - 13-15

2. moderate - 9-12

3. severe - 3-8

epilepsy

a group of abnormal neurons that seem to fire without a clear cause

idiopathic generalized epilepsy (IGE)

epilepsy of unknown cause; suspected to have a genetic component

types of epilepsy

1. generalized - involves both hemispheres of the brain

2. focal - involves one hemisphere of the brain

3. unknown

types of seizures

1. focal (partial)

2. generalized

types of focal (partial) seizures

1. focal aware seizures

2. focal impaired awareness seizures

focal aware seizures

the person remains conscious and can recall the event

focal impaired awareness seizures

consciousness is impaired, and the person may not remember the seizure

types of generalized seizures

1. tonic-clonic

2. absence

3. myoclonic

4. atonic

tonic-clonic seizures

aka grand mal; characterized by a loss of consciousness, muscle stiffening (tonic phase) and rhythmic jerking movements (clonic phase)

absence seizures

aka petit mal; brief loss of consciousness or staring spells; common in children

myoclonic seizures

sudden, brief jerks or twitches of the arms or legs

atonic seizures

sudden loss of muscle tone, causing the person to fall

seizure triggers

1. sleep deprivation

2. stress

3. bight / flashing lights (photosensitivity)

4. alcohol / drug use

5. fever / illness

6. non-compliance with medications

epilepsy management

1. antiepileptic drugs

2. lifestyle modifications

3. surgical treatment

4. vagus nerve stimulation

status epilepticus

medical emergency; state of continuous seizure activity lasting more than 5 min or rapidly recurring seizures before the person has fully regained consciousness from the preceding seizure

meningitis

occurs when infectious organisms invade the meninges, leading to inflammation and IICP; the infection typically spreads through the bloodstream after entering the body via the respiratory tract or direct entry through trauma or surgical procedures; inflammatory response → increased CSF → IICP

types of meningitis

1. bacterial

2. viral

3. fungal / parasitic

meningitis patho

inflammation → IICP → cerebral edema → disrupted autoregulation

Kernig’s sign

patient supine with hip flexed 90 degrees; knee cannot be fully extended

Brudzinski’s sign

neck rigidity (passive flexion of neck causes flexion of both legs and thighs)

meningeal signs

1. positive Kernig’s

2. positive Brudzinski’s

encephalitis

acute inflammation of the brain, usually caused by a virus

primary encephalitis

1. common viruses - HSV, epstein-barr virus

2. non-infectious causes - autoimmune encephalitis

3. arboviruses (spread by mosquitos, ticks, and other insects) - west nile

secondary encephalitis

1. could be caused by a complication of viral infection

encephalitis interventions

1. antiviral or immunotherapy

2. reduce cerebral edema

3. temperature control

Monroe-Kellie doctrine components

1. cerebrospinal fluid - 10%

2. intravascular blood - 12%

3. brain tissue - 78%

intracranial compliance

ability of the brain to tolerate increases in volume of 1 or more of the brain’s 3 components without an increase in ICP

increased intracranial pressure (IICP)

a life-threatening situation that results from an increase in any or all of the 3 components of the skull; small increase in volume causes dramatic increase in ICP

IICP acute primary injuries

1. TBI

2. hematomas

3. stroke or ischemic injury

4. subarachnoid hemorrhage

5. CNS infection

IICP chronic primary injuries

1. tumors

2. chronic subdural hematomas

3. abscess

4. hydrocephalus

IICP secondary injuries

1. biochemical and cellular response to initial trauma

2. delayed responses - hemorrhage, hematoma, seizures, herniation, cerebral edema

TBI mechanisms of injury

1. penetrating

2. blunt

penetrating TBI injury

foreign object causing direct damage to cerebral tissue

blunt TBI injury

objective, windshield, floor etc.; causes concussions, contusions, skull fractures, hemorrhage, lacerations, and hematomas

types of breathing

1. Cheyne-Stokes

2. central neurogenic hyperventilation

3. apneustic breathing

4. cluster breathing

5. ataxic breathing

Cheyne-Stokes breathing

caused by bilateral hemispheric disease or metabolic brain dysfunction; cycles of hyperventilation and apnea

types of posturing

1. decorticate response (flexor)

2. decerebrate response (extensor)

3. decorticate response on right and decerebrate response on left

4. opisthotonic posturing

opisthotonic posturing

aka opisthotonus; severe abnormal posturing where the body is held in an arched position (head and heels bent backward, trunk arched forward)

bacterial meningitis

medical emergency; common bacterial “culprits” are Hib, neisseria meningitides, streptococcus pneumoniae

viral meningitis

manage symptoms (self-limiting); most common causes are enterovirus, arbovirus, HIV, and HSV; most often spread through direct contact with respiratory secretions; test CSF; treat with antibiotics initially and discontinue if found to be viral