Icp 25

icp

1. INTRACRANIAL PRESSURE MONITORING DR RAVI GOYAL SENIOR RESIDENT DEPARTMENT OF NEURO LOGY GMC KOTA

2. Intracranial Pressure Definition: The pressure that is exerted by the brain tissu e, cerebr o spinal fluid (CSF) and blood. Normal ICP : adults: 10-15 mm Hg children: 3-7 mm Hg infants: 1.5-6 mm Hg

3. Historical Review Understanding of the CSF circulation — MAGENDIE who described a small foramen in the floor of the fourth ventricle 175 years ago.

4. ALEXANDER MONRO &GEORGE KELLIE((1823- 24,Scotland) ) defined closed box concept

5. Monroe-Kelly doctrine: the summarized volume of the intracranial components (brain tissue, blood, CSF) is constant. Increase of any of them is possible only at the expense of the other two, and increases the intracranial pressure. V intracranial vault = V brain + V blood + V csf

6. 1891 QUINKE introduced LP allowing CSF sampling & measurement 190 3, CUSHING describes the classic Triad seen with severely elevated ICP 196 5 LUNDBERG introduced long term continuous ICP monitoring via an indwelling intraventricular catheter .

7. PATHOPHYSIOLOGY Purpose of icp monitoring –maintenance of optimal CPP CPP -Pressure needed to ensure blood flow to the brain CPP = MAP – ICP CBF = CPP/CVR CVR-cerebrovascular resistance CPP should be > 60mmhg for optimal perfusion to brain The critical parameter for brain function and survival is not actually ICP , rather it is adequate cerebral blood flow (CBF) .

8. Skull has three essential components Brain tissue 8 % (1400ml) Blood 1 % (75-100ml) C S F 10 % (75-100ml) Principle buffers in the brain: CSF & to a lesser extent, venous blood as they are connected to low pressure outlets .

9. Autoregulation of cerebral blood flow Automatic alteration in diameter of cerebral blood vessels to maintain constant blood flow to brain . Cerebral autoregulation is a mechanism whereby over wide range, large changes in systemic BP produce only small changes in CBF . Due to autoregulation. CPP would have to drop below 40 in a normal brain before CBF would be impaired

10. Intracranial compensation The brain is essentially non-compressible . Any increase in intracranial volume decreases C SF or CB V ( cerebral blod volume). CSF - primarily displaced into the spinal subarachnoid space . Blood - venoconstriction of CNS capacitance vessels displaces blood in jugular venous system .

11. Exhaustion of compensation Once these limited homeostatic mechanisms are exhausted additional small increases in intracranial volume produce marked elevations in ICP . Raised ICP may decrease CPP & CBF eventually cerebral herniation & death .

12. Why look at ICP waveform analysis Provides information about intracranial dynamics to identify individuals who are at risk for increases in ICP and decreases in CPP which causes secondary brain injury and have a negative impact on neurologic outcome.

13. ICP WAVEFORM Normal I CP trace is pulsatile and reflects cardiac and respiratory cycles. The respiratory wave reflects changes in intra thoracic pressure with respiration . Its amplitude varies between 2 and 10 mm Hg. This respiratory variation diminishes and eventually disappears with rising ICP.

14. The pulse component of normal ICP waveform generally consists of three peaks, which correlate with the arterial pressure waveform occurring with each cardiac cycle. Amplitude- 1-4 mmhg The P1 wave, or the percussion wave, correlates with the arterial pulse transmitted through the choroid plexus in to the CSF.

15. The P2 wave, or the tidal wave, represents cerebral compliance and can be thought of as a ‘reflection’ of the arterial pulse wave bouncing off the springy brain parenchyma. The P3 wave, or the dicrotic wave, correlates with the closure of the aortic valve, which makes the trough prior to P3 the equivalent of the dicrotic notch .

16. Pathological Waves

17. Lundberg A wave Plateu waves Amplitude = 50-100mmHg Duration - 5-10min Shows loss of intra cranial compliance and imminent decompensation of autoregulatory mechanism . Suggest urgent intervention to control ICP.

18. LUND BERG B WAVES Sharp and rythmic Duration < 2 min with amplitude to 20-30 mmHg Precede A wave may be d/t respiratory changes &variations in CBF ( vasomotor changes ) Reflects ↑ ICP in a qualitative manner

19. Lundberg C waves More rapid sinusoidal fluctuation (0.1 Hz) Corresponds to Traube- Hering Meyer fluctuations in arterial pressure produced by oscillations in baroreceptor and chemorecepto r reflex control systems . Sometimes seen in normal ICP waveform No clinical significance

20. Indications for intracranial pressure monitoring Mc indication – traumatic brain injury(TBI) RECOMMENDATIONS Level I - none Level II - all salvageable pts with GCS of 3–8 and abnormal CT Level III - in pts with severe TBI with normal CT if 2 or more of age > 40 years unilateral or bilateral motor posturing SBP < 90 mm Hg J Neurotrauma. 2007;24 Suppl 1:S37-44. Guidelines for the management of severe traumatic brain injury .

21. Other indications are :- Condition require aggressive medical care- Hydrocephalus ICH , SAH, intracranial tumur Cerebral odema Contraindications : Awake patient Coagulopathy

22. ICP Monitoring Technique Non Invasive: Magnetic Resonance Imaging (MRI) & Computer Tomography Transcranial Doppler Ultrasonography (TCD) Tympanic Membrane Displacement (TMD) OpticNerve Sheath Diameter (ONSD) – via Transocular USG Pupillometry

23. ICP Monitoring Techniques Invasive : Based on Technological differences : 1. External Ventricular Drainage (EVD) – Gold Standard 2. Microtransducer ICP Monitoring Devices :- Fiberoptic – camino icp monitor, innerspace monitor Strain Gauge – codman microsensor , pressio , Neurovent -p Pneumatic - spelberg monitor

24. Based on location : 1 . Intraventricular 2. Intraparenchymal 3. Epidural / subdural 4. Subarachnoid

25. Various monitors

26. American National Standard for Intracranial Pressure Monitoring Devices, specifies that ICP monitoring device should have :- A pressure range between and 100 mm Hg . Accuracy of +/- 2 mm Hg within the range of to 20 mm Hg . Maximal error of 10% in the range of 20 to 100 mm Hg .

27. NCCT HEAD F astest and the most cost‑effective method. Findings suggestive of a high ICP includes: cerebral oedema, midline shift e ffacement of basal cistern loss of grey‑white differentiation loss of normal gyri and sulci patten

28. MRI BRAIN This modality is costly and time consuming, and hence not the first line investigation in the acute care setting. While invasive monitoring provides continuous ICP measurements, the MRI study provides a single time point measurement and therefore it serves only as a diagnostic test.

29. Transcranial Doppler USG M c intra cranial artery used –Middle cerebral artery. The mean velocity P ulsatility index ( difference between peak systolic and end diastolic velocity/mean flow velocity), and Slopes of the TCD waveforms have been correlated with ICP. Margin of error of ± 10–15 mm Hg. Require training , and inter‑ and intra‑observer variations also seen Difficult to do in 10–15% patients who not have an adequate bone window.

30. Tympanic Membrane Displacement TMD gives an idea of Cochlear fluid pressure acts as a surrogate for I CP . Prerequisite intact stapedial reflex and patency of cochlear aqueduct. High cochlear fluid pressure causes an inward- directed movement of the tympanic membrane, low cochlear fluid pressure causes an outward movement. This movement is measured as the mean volume displacement (Vmean [nL]) L ess accurate .

31. Optic nerve sheath diameter T he space between the optic nerve and its sheath is a continuation of the subarachnoid space, filled with CSF , whose pressure is equal to the ICP. The diameter of the nerve sheath can be measured using transocular ultrasound. O ptic nerve sheath diameter (ONSD ) > 5 mm corresponds to an ICP of 20 mm Hg or higher. This is cheap and efficient and takes around 5 min for measurement.

32. C onditions such as tumours, inflammation , Grave’s disease and sarcoidosis , may alter the ONSD . L esions of the orbit or optic nerve in patients with head injury may preclude nerve sheath diameter measurement . ONSD is a promising technique for screening patients with raised ICP in settings where invasive ICP monitoring techniques are either not feasible (patients with severe coagulopathy ) or not available .

33. The Anatomy of the Optic Nerve Sheath

34. ONSD Measurement Common cut-off is 5 mm

35. Pupillometer Hand-held infrared system which automatically tracks and analyzes pupil dynamics over a 3-second time period. Neurologic Pupil Index ( Npi ) – A value derived f rom size, percent constriction, latency, constriction velocity and dilation velocity . N ormal Npi – 5 Npi < 3 predictor of increased I CP . Npi abnormalities started 16 hrs prior to peak ICP .

36. External Ventricular Drain An external ventricular drain ( EVD) or ventriculostomy drain connected to an external strain gauge is currently the “gold standard” for measuring I CP . ADVANTAGES : Serves also as a therapeutic device low cost most accurate

37. Disadvantages are:- Most invasive of all avalaible technique. Risk of infection (8-9%) Placement difficulty in compressed or slit like ventricle as in cerebral odema . Over shunting of CSF . Misplacement of catheter (4-20%) O cclusion of catheter (8%) Hemorrhage ( 0.91-1.2 %)

38. F I B ER O PT I C I NTRACRANIAL PRESSURE MONITOR ING Most widely used- fibre optic camino system Intraparenchymal T he catheter tip measures the change of light intensity that is reflected off a pressure-sensitive diaphragm and that is interpreted as pressure. .

39. Adavntages :- Ease of insertion- right frontal Can be inserted in severely compressed ventricles or with midline shift Accuracy low complication rate (infection and hemorrhage ) Disadvantages :- Can not be recalibrated once inserted. Costly fragile

40. The subarachnoid screw (bolt ) A sub arachnoid screw or bolt is a hollow screw that is inserted through a hole drilled in the skull. It is placed through dura mater . This allows the sensor to record from inside the subdural space.

41. d ri v e r Drill bit B O L T

42. Advantages Does not penetrate the brain . Lower risk of infection than the intraventricular catheter It is easier to place. Disdvantages It is unable to drain CSF The accuracy is questionable

43. Spiegelberg Brain pressure monitor using an Air-Pouch mounted in the tip region of a dual lumen probe. One lumen transmits the pressure to the Brain-Pressure Monitor. The second lumen is used for drainage of CSF Used for epidural and subdural pressure measurement mainly. Low cost with automatic zero drift correction.

44. MINIATURE STRAIN GAUGE TRANSDUCER CODMAN MicroSensor ICP Transduce r, the prototype . It has a microchip pressure sensor at the tip of a flexible nylon cable that produces different electricity based on pressure .

45. Advantages : can be placed in various compartments, includin g ventricular, parenchyma, and subdural space . Accurate and stable Can be used for therapeutic purpose . Small size makes useful for paediatric patient also . Best in all of them But cost is the issue .

46. ADVANCED NEUROMONITORING Used to supplement intracranial pressure (ICP) monitoring , for the treatment of severe TBI . Allows the measurement of cerebral physiologic and metabolic parameters related to oxygen delivery, cerebral blood flow (CBF), and metabolism. G oal of improving the detection and management of secondary brain injury.

47. Jugular venous oximetry It measures oxygen saturation in the blood exiting the brain. Normal jugular venous oxygen saturation ( SjVO2 ) is approximately 60 percent . SjVO2 <50 percent for 10 minutes is considered a "cerebral desaturation" and implies a mismatch between oxygen delivery and demand in the brain that’s shows unfavourable outcome .

48. Brain tissue oxygen tension ( PbtO2 ) monitoring Intraparenchymal similar to a fiberoptic ICP probe that measures PbtO2 in the white matter. Normal PbtO2 is >20 mmHg; Value below 15 mmHg are associated with worsened outcome.

49. Cerebral microdialysis Intraparenchymal probe placed that allows measurement of extracellular glucose, lactate, pyruvate, and glutamate. lactate:pyruvate ratio >40 is suggestive of anaerobic metabolis m that exacerbate secondary brain injury .

50. Pressure reactivity index ( PRx ) It is a correlation coefficient between mean ICP and mean arterial pressure (MAP), used as a measure of cerebral a utoregulation . PRx thresholds of 0.25 and 0.05, suggesting the presence of robust cerebral autoregulation . A direct correlation of ICP with MAP, with a PRx close to +1.0, suggests the absence of cerebral autoregulation that may be seen with refractory intracranial hypertension.

51. Goals of therapy Maintain ICP at less than 20 to 25 mm Hg . Maintain CPP at greater than 60 mm Hg (60-70 mm Hg ) by maintaining adequate MAP. Avoid factors that aggravate or precipitate elevated ICP .

52. Summary ICP monitoring & ICP-directed treatment remains the corner stone of neurocritical care . EVD connected to external strain gauge remains the most reliable, cost-effective and accurate method for monitoring ICP Allows CSF drainage Infection and hemorrhage are the main problems Intraparenchymal monitors are gaining popularity Easy to insert, low complication rates Zero drift, mechanical failure are the problems New technologies including the non-invasive ones are emerging .

53. Refrences : Indications for intracranial pressure monitoring: Brain Trauma Foundation . J Neurotrauma 2007;24:S37‑45. Abraham M, Singhal V. Intracranial pressure monitoring . J Neuroanaesthesiol Crit Care 2015;2:193-203. www.uptodate.com

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