Intracranial Pressure Concepts Michelle Hill RN BSN CNRN

Intracranial Pressure Concepts Michelle Hill RN, BSN, CNRN, CCRN, SCRN Clinical Nurse Educator Neurocritical Care

�Review (ICP) �Discuss intracranial pressure concepts cerebral hemodynamics herniation syndromes management of increased ICP types of ICP monitoring devices Objectives

� Intracranial pressure is the pressure exerted by the intracranial contents of brain tissue, blood, and cerebrospinal fluid (CSF) within the skull. � Fluctuates within a normal range. � Normal ICP = 0 – 15 mm. Hg � Moderate elevation ICP = 15 – 40 mm. Hg � Severe elevation ICP > 40 mm. Hg � Intracranial hypertension: ◦ ICP >20 mm. Hg for >5 minutes Intracranial Pressure (ICP)

Monroe-Kellie Doctrine Used to explain why ICP exists Skull is a rigid, non-distendable box containing 3 volume components: ◦ 80 % brain tissue ◦ 10% blood ◦ 10% CSF As long as these volumes remain the same, the pressure within the box is unchanged

Signs and Symptoms of Increased ICP Headache (Worse in morning) Vomiting without nausea Change in LOC Change or loss of motor/sensory function Pupillary changes Respiratory changes Papilloedema Cushing’s Response ◦ Increased systolic blood pressure ◦ Widened pulse pressure ◦ Bradycardia

Cheyne-Strokes Apneustic Hyperventilation Respiratory Signs and Symptoms 6

�Progressive deterioration in LOC ◦ Caudal displacement of the diencephalon and midbrain �Pupillary dilitation, B/L ptosis, impaired upward gaze �Extension to pain �Respiratory irregularity Herniation or ICP? 7

�Space-occupying masses ◦ Abscesses ◦ Tumors ◦ Aneurysms ◦ Trauma-hematoma �Cerebral Edema ◦ Vasogenic (extracellular) ◦ Cytotoxic (intracellular) What Causes Increased ICP-Brain

�Stroke �Trauma �Conditions that increase blood ◦ HTN ◦ Pa. CO 2 ◦ Anesthetic agents �Decreased venous return ◦ HOB flat ◦ Trach ties ◦ Neck flexion flow More causes of Increased ICP-Blood

�Increases in CSF volume ◦ Obstruction of CSF pathways �Non-Communicating hydrocephalus ◦ Decreased CSF absorption �Communicating hydrocephalus �Subarachnoid hemorrhage ◦ Overproduction of CSF �Choroid plexus papillomas More Causes of Increased ICP-CSF

�Required to provide oxygenation to the brain tissue �Approximate CBF is 55 m. L/100 g of brain tissue per minute � 450 -1000 m. L/min to the whole brain �Brain receives 20% of total cardiac output and uses 20% of oxygen consumed in the basal state. Cerebral Blood Flow (CBF)

�Autoregulation ◦ Ability of an organ to maintain a constant blood flow ◦ Major homeostatic and protective mechanism ◦ Provides a constant CBF by adjusting the diameter of blood vessels. Cerebral Blood Flow Regulation

� Arterial carbon dioxide pressure affects the CBF by affecting the arterioles of the brain. � Pa. CO 2 > 45 mm. Hg causes inappropriate vasodilation of the arterioles which ↑ CBF. � Pa. CO 2 < 35 mm. Hg causes constriction of the arterioles which ↓ CBF. � Pa. O 2 <50 mm. Hg also causes cerebral vasodilation. Cerebral Blood Flow

�CPP is the blood pressure gradient across the brain �CPP is the difference between the mean arterial pressure (MAP) and the intracranial pressure (ICP) �Any blood coming into the brain must overcome the ICP to enter the intracranial contents and perfuse brain cells. Cerebral Perfusion Pressure (CPP)

Cerebral Perfusion Pressure �CPP = MAP – ICP �More important than ICP value �Normal CPP range is ◦ CPP < 60 = ischemia ◦ CPP < 40 = infarct ◦ CPP – 0 = brain death 70 – 100 mm. Hg

� These are protective mechanisms to assure that the brain is receiving adequate perfusion � If one of the intracranial volumes increases another must decrease to avoid increase in ICP ◦ CSF ◦ Blood ◦ Tissue Compensatory Mechanisms

• Cerebrospinal Fluid Component – Displacement of CSF into the spinal subarachnoid space – Decreased production of CSF Compensatory Mechanisms-CSF

�Blood component ◦ Vasoconstriction of the blood vessels of cerebral structures (carbon dioxide) �Decrease in the intracranial blood volume ◦ Increased venous outflow �Corrected with positioning Compensatory Mechanisms-Blood

Compensatory Mechanisms-Brain Tissue Component ◦ Supratentorial Subfalcine (1) Uncal (2) ◦ Loss of consciousness ◦ Ipsilateral pupil dilation ◦ Contralateral hemiparesis ◦ Infratentorial (3)

�Success of compensatory mechanisms is dependent upon several factors: ◦ Rate of expansion of the volume causing increased ICP ◦ Compliance of the brain ◦ Location of the expanding volume Compensatory Mechanisms

� Elevated BP ◦ Ischemia in Medullary vasomotor center-increase in systemic arterial pressure ◦ Intraluminal blood pressure must be higher than the ICP for continued blood flow � Widened pulse pressure ◦ Elevated BP increases CO � Bradycardia ◦ Pressure on the Vagal control in the Medulla ◦ Becomes decreased but bounding to pump blood upward Cushing’s Response

�Basic measures �ICP monitor �Mannitol �Hyperventilate Management of ICP 22

Management of ICP Craniectomy: excision of a portion of the skull without replacement ◦ Skull bone can be stored in the patient’s abdomen ◦ Considered a life-saving measure for maximal cerebral swelling

�It is the complete and irreversible cessation of all brain function �Absence of brain function and all brain stem reflexes �Cerebral blood flow is 0 in brain death �Brain death is the legal definition of death �Spinal reflexes may still be present �Brain Death Protocol Brain Death

References � � � Dunn, L. (2002). Raised Intracranial Pressure. Journal of Neurology, Neurosurgery and Psychiatry. 73 (suppl 1). i 23 -i 27. Germon, K. (1988). Interpretation of ICP pulse waves to determine intracerebral compliance. Journal of Neuroscience Nursing, 20, 344– 351. Hickey, J. V. (2009). The Clinical Practice of Neurological and Neurosurgical Nursing (6 th ed. ). Philadelphia: Lippincott. March, K. (2004). Intracranial Pressure Concepts and Cerebral Blood Flow. In M. K. Bader & L. R. Littlejohns, AANN Core Curriculum for Neuroscience Nursing (4 th ed. , pp. 87– 114). Philadelphia: Saunders. Slazinski, T. , Anderson, T. , Cattell, E. , Eigsti, J. , Heimsoth, S. , Holleman, J. & et. al. (2011). Care of the patient undergoing intracranial pressure monitoring/external ventricular drainage or lumbar drainage. American Association of Neuroscience Nurses Clinical Practice Guideline Series. Stevens, R. , Huff, J. , Duckworth, J. , Papangelou, A. , Weingert, S. & Smith, W. , (2012). Emergency Neurological Life Support: Intracranial Hypertension and Herniation. Neurocritical Care. DOI: 10. 1007/s 12028012 -9754 -5