week 2 Management of Intracranial Problems Flashcards
What is brain death?
Irreversible loss of all brain functions, including those of the brainstem. Brain death is a clinical diagnosis, and it can be made in patients whose hearts continue to beat and who are maintained on mechanical ventilation in the ICU. Brain death occurs when the cerebral cortex stops functioning or is irreversibly destroyed.
Differentiate between primary and secondary injury.
Primary injury occurs at the initial time of the injury. Example is impact of car accident, or blunt force trauma , that results in displacement, bruising, or damage of the three components. Secondary injury is the resulting hypoxia, ischemia, hypotension, edema, or increased ICP that follows the primary injury. Can occur several hours to days following initial injury, and is primary concern in managing brain injury.
What are the 3 components of the brain and their percentages?
Cerebral spinal fluid (10%), Intravascular blood (12%), and brain tissue(78%).
What is intracranial pressure (ICP)?
ICP is the hydrostatic force measured in the brain CSF compartment.
What are the 6 factors that influence ICP under normal circumstances?
- arterial pressure 2. venous pressure 3. intraabdominal and intrathoracic pressure 4. posture
- temperature 6 blood gasses, particularly CO2 levels.
Where is ICP measured and what is the device used to measure it?
ICP is measured in the ventricles, subarachnoid space, subdural space, epidural space, or brain tissue using a pressure transducer.
What is normal ICP ?
Normal ICP ranges from 5-15 mm Hg. A pressure of greater than 20 mm Hg is considered abnormal and must be treated.
What is the Monro-Kelli doctrine ?
The Monroe-Kelli doctrine states that the three components of the brain must remain at a relatively constant volume within the closed skull structure. If the volume of one increases within the cranial vault and the volume of another component is displaced the intracranial volume will not change.
In applying the Monro-Kelli doctrine in what 3 ways can the body adapt to volume changes within the skull to maintain normal ICP?
- compensatory mechanisms make changes in the CSF volume by altering CSF absorption or production or displacing it into the spinal subarachnoid space.
- changes in intracranial blood volume can occur through collapse of cerebral veins and dural sinuses, regional cerebral vasoconstriction or dilation or changes in venous blood flow.
3 brain tissue volume changes through distension or compression of brain tissue
What is cerebral blood flow (CBF)? l
CBF is the amount of blood in milliliers passing through 100 g of brain tissue in 1 minute.
What percentages of body’s oxygen and glucose does the brain use?
20% of body’s oxygen ; 25% of its glucose
What is Autoregulation of cerebral blood flow?
Autoregulation is the automatic adjustment of the diameter of the cerebral blood vessels by the brain to maintain a constant blood flow during changes in arterial blood pressure.
What is the limits of systemic arterial pressure at which autoregulation is effective?
70mm Hg and 150mm Hg. Below a Mean arterial pressure( MAP) of 70mm hg the CBF decreases and symptoms of cerebral ischemia occur, such as syncope, blurred vision. Above 150 mmHg the vessels are maximally constricted and further vasoconstriction cannot take place.
What is cerebral perfusion pressure (CPP)?
CPP is the pressure needed to ensure blood flow to the brain.
How is CPP ( cerebral perfusion pressure) calculated using MAP and ICP?
CPP=MAP-ICP
