intracranial pressure

normal ICP

5-15mmHg

factors that inc ICP

• arterial BP and venous BP

• intraabdominal pressure (coughing)

• intraathoracic pressure (ventilator)

• posture (bending over)

• temperature

• blood PaCO2 in systemic circuit

• masses

• cerebral edema

• structural abnormalities

INC pAco2

relaxes smooth mx, dilates cerebral vessels and inc CBF

dec PaCO2

constricts smooth mx and cerebral vessels and dec CBF

3 compensatory mechanisms

1. CSF vol can change to accommodate brain tussue/BF

2. intracranial BV can be manipulated when CSF and braun tissue expand

3. brain tissue can distend and compress to accommodate BF and CSF changes

normal CBF

50mL/min/100g

cushings triad

very late sign of ICP

1. elevated systolic BP with widened pulse pressure (diastolic is WNL)

2. bradycardia: inc swelling pressure on vagus nerve (controls HR/RR)

3. altered respirations (cheyne stokes)

   1. cycles of hyperventilation and apnea

      1. indicates problem w/pons and medulla oblongata

mannitol and hypertonic saline 3%

• fluid out of cell -> blood

• Na monitored every 8, hold if >155

• monitor for dehydration -> draw K labs esp

• stabilize cell memnranes/inhibit prostaglandins - corticosteroids

• prevent seizures (inc ICP = inc seizure risk)

• lower metabolic demand of brain tx with antipyretics, barbituarates/CNS depressant

CPP

MAP-ICP=CPP

normal CPP = 60-100mmHg

• CPP less than 50 is associated with ischemia and neuronal death = dec perf

• CPP less than 30 is incompatible with life

• elevated ICP dec CPP

elevated ICP CM

• changes in LOC (earliest sign)

• headache

• changes in VS (cushings)

• ocular signs of ICP (compression of optic N)

  • blown pupil

  • sluggish pupils

  • bilateral ominous sign

• dec motor fxning/posturing

  • decorticate: c-core of body (flexor)

  • decerebrate: e-extension = problems within midbrain/pons = breathing

• projectile vomiting with no nausea

  • no indication -> worse

• peds: setting sun sign in eyes (eyes cant look up higher)

external ventricular drain/ventriculostomy

drain to monitor ICP

ICP monitoring/measuring

indicated in patients w/ GSC less than 8 w abnormal CT/MRI

• directly measures pressure

• facilitates removal/sampling of CSF

• allows for intraventricular drug administration (provider only)

• *transducer positioning must be level w/ tragus of ear (zero it to gravity)

• high risk of infection such as meningitis -> SEPSIS

craniectomy

take off skull, may stay open

craniotomy

lump/mass, take skull off but put back on

nutritional needs

brain needs a constant supply of glucose

• tube feeds

• PERRLA and LOC!!