1. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 1 Intracranial Pressure

2. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 2 Intracranial Pressure Definition –Pressure exerted by brain tissue, intracranial blood, and cerebral spinal fluid (CSF) in a non-distended (closed) cavity

3. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 3 Normal Contents of the Skull Brain - 80% Blood - 10% CSF - 10% Monroe-Kellie Doctrine

4. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 4 Changes in Skull Contents Increased intracranial volume –Hyperemia –Bleeding, clots, bruises –Cerebral edema –Hydrocephalus –Foreign object –Tumor

5. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 5 Intracranial Pressure Cerebral edema (localized or generalized) can develop from any injury to the brain Swelling peaks in 3-5 days

6. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 6 Post-traumatic Hydrocephalia Communicating –CSF circulates but is not reabsorbed –Arachnoid villa are clogged Non-communicating –CSF circulation is obstructed –CSF can not reach the arachnoid villa to be reabsorbed

7. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 7 Pressure - Volume Relationship Compliance = change in volume change in pressure Defines the relationship between pressure and volume within the skull

8. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 8 Pressure - Volume Relationship Three portions of the waveform curve –Flat –Curved –Vertical (inflection) point

9. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 9 ICP Waveforms Normal waveform resembles a set of stairs With increasing ICP, waveform loses shape

10. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 10 Brain Herniation Definition –Distortion and displacement of the brain from one compartment to another caused by increased volume and pressure and decreased compliance

11. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 11 Brain Herniation Three types –Central or transtentorial –Uncal or lateral transtentorial –Cingulate

12. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 12 Mean Arterial Pressure (MAP) Calculate MAP –Subtracting diastolic pressure from systolic pressure –Divide by 3 –And add diastolic pressure 140 - 100 = 40 3 = 13 + 100 = 113 MAP = 113

13. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 13 Cerebral Perfusion Pressure (CPP) Pressure gradient driving blood flow and delivery of nutrients to the brain

14. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 14 Cerebral Perfusion Pressure (CPP) Calculate CPP –Subtract ICP from MAP Patient has an ICP of 80 and a MAP of 113 113 MAP - 80 ICP 33 CPP

15. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 15 Cerebral Perfusion Pressure (CPP) CPP = MAP - ICP Best if > 70 mmHg < 60 mmHg = impaired blood flow to brain

16. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 16 Cerebral Perfusion Pressure (CPP) < 50 mmHg Mild cerebral ischemia < 40 mmHg Cerebral blood flow down 25% < 30 mmHg Irreversible cerebral ischemia If MAP = ICP –There is no blood flow to the brain and brain death in imminent

17. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 17 Increased ICP Neurological exam Motor function Respiratory Body temperature LOC Pupil Vision Herniation

18. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 18 Signs & Symptoms of ICP Vital signs changes - Cushing’s triad Widening pulse pressure Bradycardia Abnormal respiratory patterns

19. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 19 Signs & Symptoms of ICP Respiratory changes –Cheyne-stokes –Central neurogenic hyperventilation –Biot’s –Kussmal

20. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 20 ICP Monitoring

21. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 21 ICP Monitoring Indications –Glasgow coma score <8 and positive CT –Paralytic and/or sedative medications are being used

22. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 22 Devices Interventricular cannula (IVC) Epidural catheter Subdural / subarachnoid monitoring devices Fiber optic transducer tipped probe

23. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 23 Interventricular Cannula (IVC) Most commonly used monitor Placed within the ventricle Location of placement for some Caminos

24. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 24 Interventricular Cannula (IVC) Advantages –Drain CSF to lower ICP –Obtain CSF cultures –Increased accuracy in ICP monitoring –Accurate and reliable Disadvantages –Infection –Injury to brain –Clot formation –Hemorrhage risk –Collapsed ventricle –Placement may be impossible

25. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 25 Interventricular Cannula (IVC) Transport considerations –System set-up –Charting ICP –Drainage orders –Movement –Pressure changes with air transport

26. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 26 Epidural Catheter Lies beneath skull - above dura mater Advantages –Lesser rate of infection than IVC –Placement causes less injury to brain Disadvantages –Less accurate than IVC –Cannot be used to drain CSF

27. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 27 Subdural / Subarachnoid Monitor Newer systems connect to fiber optics Called a “screw” or “bolt” Subdural - beneath dura and above pia Subarachnoid - placed beneath arachnoid and above pia

28. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 28 Subdural / Subarachnoid Monitor Advantages –Not as invasive as IVC or epidural –Less rate of infection –Less injury to brain –Easier to place Disadvantages –Less accurate monitoring –Cannot drain CSF –Risk of bleeding and brain injury –Higher rate of infection than epidural catheter –Requires closed, intact skull

29. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 29 Fiber Optic Transducer Tipped Probe Catheter with pressure sensing device placed into subdural space, brain parenchyma or ventricle Non fluid filled continuous intact system

30. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 30 Fiber Optic Transducer Tipped Probe Advantages –Good waveform –Reliable and accurate pressure reading –No air bubble formation within catheter Disadvantages –Inability to access ICP unless IVC setup is used –Unit cannot be zeroed once placed

31. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 31 Transport Considerations Avoid tension or kinking of cable Less problem with zeroing Maintain clean / intact dressing

32. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 32 ICP Data Normal values 0-15 mmHg Normal waveforms first 3 waves – P1 - percussion – P2 - tidal wave – P3 - dicrotic wave Abnormal waveforms –C waves - think PACs –B waves - think PVCs –A waves - think V-fib

33. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 33 Management of ICP Gas exchange –Optimize gas exchange to maintain ICP or decrease ICP levels –Good pulmonary toilet –Ph changes –Hyperoxygenation –Hyperventilation –Positive end expiratory pressure (PEEP)

34. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 34 Management of ICP Hyperventilation –Vasodilation occurs in brain tissue to increase circulation and then increases ICP Goals of hyperventilation –Remove CO 2 and cause vasoconstriction –Cause - respiratory alkalosis –Effect - pace drops reducing cerebral blood flow

35. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 35 Hyperventilation Controversy What is optimal paco 2 level? –Old method - keep paco 2 at 25 mmhg –New method - paco 2 range 28-32 mmhg

36. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 36 Factors which Increase ICP Hip flexion (decreases venous return) Head and neck position Changing level of height of bed (especially flat) External noxious stimuli Agitation Pain Coughing and valsalva maneuver Seizures

37. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 37 Methods of Decreasing ICP Decrease external stimulation Ensure a quiet environment Pull slouching patients to the top of the bed Use cervical collar with decreased neck muscle tone Shut off bright lights Align head and neck Surgical intervention

38. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 38 Methods of Decreasing ICP If IVC in place, open and drain If too much CSF is lost, the ventricle can collapse

39. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 39 Methods of Decreasing ICP Medications –Sedation –Paralytics –Diuretics –Steroids –Barbituate coma

40. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 40 Medications Sedatives –Ventilator patients –Pentathol or fentanyl Paralytics –Decrease metabolism –Generally utilized with sedatives –ICP monitoring necessary for most medically paralyzed patients

41. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 41 Medications Diuretics –Mannitol and Lasix Steroids –Dexamethasone / methylprednisone –Controversial Some studies show no benefit, others show limited benefit if given within 8 hours of the injury

42. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 42 Medications Barbiturate coma –Induced pharmacologically using barbiturates Barbiturate coma results –Neuro status - unresponsive with a GCS of 3 –Respiratory - ventilator dependent –Cardiovascular - bradycardia and hypotensive

43. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 43 Intracranial Pressure Monitoring Operative intervention –Surgical removal of blood clot or affected portion of the brain

44. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 44 Intracranial Pressure Conclusion

45. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 45 Neuromonitoring for Traumatic Brain Injury

46. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 46 Intracranial Pressure Monitoring

47. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 47 Jugular Venous Bulb Oximetry

48. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 48 Transcranial Doppler Ultrasound

49. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 49 Cerebral Function Monitoring

50. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 50 Emerging Monitoring Technologies

51. © 2001 UMBCNeurological Management CCEMT-P SM 12/98 51 References