CSF and 
                                Ventricular 
                                    System
       •   CSF is a colorless, clear fluid produced by choroid plexus in lateral and 
           third ventricle
            – Functions as a cushion for brain and spinal cord
       •   500-600 ml CSF produced daily
       •   3 cycles of CSF, made then absorbed, made then absorbed, etc in a 24hr 
           period
       •   Brain has four CSF filled and 
           interconnected ventricles
                               Intracranial 
                                   Pressure
      •   Intracranial Pressure (ICP) is the pressure exerted by the brain content:
           – Brain Tissue (85%)
           – Cerebral Spinal Fluid (CSF) (10%)
           – Intravascular blood (2-11%)
      •   Cerebral Autoregulation: The ability of the cerebral vessels to constrict 
          and dilate as needed to maintain adequate cerebral perfusion
           – Impaired with brain injury and the cerebral blood flow becomes 
              passively dependent on blood pressure
      •   Monro-Kellie Hypothesis: an increase in one component must be offset 
          by an equal decrease in one or more components otherwise an increase in 
          ICP will result
                                   ICP 
                            Pressures
                         We want ICP to be less than 20!
      •  Increased ICP occurs when the intracranial volume exceeds 
         the brain’s ability to compensate for increased volume
      •  Sustained ICP above 25 mmHg is considered a neurologic 
         emergency
                             Cerebral Perfusion 
                                        Pressure
                   •  Cerebral Perfusion Pressure (CPP):  Pressure at 
                      which the brain is perfused
                       – About 15-20% of cardiac output
                         CPP = Mean Arterial Pressure (MAP) – ICP. 
                   •  Normal CPP 40-60 (Kids, depends on age)
                   •  Normal CPP 80-90 mmHG (Adults)
                   •  CPP below set parameter will result in cerebral 
                      ischemia and tissue death
                                 Causes of 
                                 Increased 
                                          ICP
       •   Contusions
                                                      •   Coughing
       •   Hematomas
                                                      •   Endotrachial suctioning
       •   Tumors
                                                      •   Hypercarbia
       •   Infarcts
       •   Fluid overload                             •   Hypoxia
       •   Mechanical ventilation (PEEP)              •   Increased CSF Production
       •   Valsalva maneuver                          •   Metabolic disturbances