intracranial pressure monitoring

ICP MONITORING

1. INTRACRANIAL PRESSURE MONITORING DR SHAMEEJ MUHAMED KV SENIOR RESIDENT DEPARTMENT OF NEUROSURGERY , GMC CALICUT

2. HISTORICAL REVIEW

3. 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. 1846 - BURROW - The concept of reciprocal volume changes between blood and CSF to account for the changes in ICP. early 20th century - WEED - An understanding of raised ICP encompasses an analysis of both intracranial volume and craniospinal compliance 1866 Lyden measures ICP via trephine 1866 Knoll produces graphic CSF pressure trace 1870 Duret observes deleterious effects of injecting fluid in to dogs skulls

6. 1891 QUINKE introduced LP allowing CSF sampling & measurement 1900 CUSHING describes the classic Triad seen with severely elevated ICP 1960 LUNDBERG introduced long term continuous ICP monitoring via an indwelling intraventricular catheter.

7. Intracranial Pressure Definition: The pressure that is exerted on to the brain tissue by external forces, such as cerebrospinal fluid (CSF) and blood. Normal ICP: adults: 10-15 mm Hg / 135-200 mm of water . children : 3-7 mm Hg infants: 1.5-6 mm Hg neonates: <-2 mm Hg

8. Skull has three essential components Brain tissue 78% ( 1400ml) Blood 12% (75-100ml) CSF 10% (75-100ml ) Principle buffers in the brain: CSF & to a lesser extent, venous blood volume as they are connected to low pressure outlets .

9. 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

10. Intracranial compensation The brain is essentially non-compressible Any increase in intracranial volume decreases CSF or CBV 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. 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

13. Cerebral Blood Flow CPP -Pressure needed to ensure blood flow to the brain CPP = MAP – ICP Normal is 70 to 100 mm Hg <50 mm Hg is associated with ischemia and neuronal death The critical parameter for brain function and survival is not actually ICP, rather it is adequate cerebral blood flow (CBF) to meet CMR 02 demands

14. Why look at ICP waveform analysis? provides information about intracranial dynamics that can help identify individuals who have decreased adaptive capacity and are at risk for increases in ICP and decreases in CPP, which may contribute to secondary brain injury and have a negative impact on neurologic outcome.”

15. Indications for intracranial pressure monitoring 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. VI. Indications for intracranial pressure monitoring. Brain Trauma Foundation; American Association of Neurological Surgeons; Congress of Neurological Surgeons; Joint Section on Neurotrauma and Critical Care, AANS/CNS,

16. Contraindications: Awake patient Coagulopathy

17. Ideal ICP monitor Nils Lundberg outlined the basic requirements for an ICP monitor • Minimal trauma during placement • Negligible risk for infection • No CSF leakage, easy to handle, reliable • Able to continue to function during various diagnostic and therapeutic procedures

18. ICP Monitoring Techniques Invasive : Based on Technological differences: External Ventricular Drainage (EVD) – Gold Standard Microtransducer ICP Monitoring Devices Fiberoptic Strain Gauge Pneumatic Based on location: 1. Intraventricular 2. Intraparenchymal 3. Epidural 4. Subdural 5. Subarachnoid

19. Non Invasive: 1. Transcranial Doppler Ultrasonography (TCD) – Based on PI 2. Tympanic Membrane Displacement (TMD) 3. OpticNerve Sheath Diameter (ONSD) – via Transocular USG 4. Magnetic Resonance Imaging (MRI) & Computer Tomography (CT) 5. Pupillometry

20. Various monitors

21. American National Standard for Intracranial Pressure Monitoring Devices, specifies that ICP monitoring device should have A pressure range between 0 and 100 mm Hg, Accuracy of 2 mm Hg in the range of 0 to 20 mm Hg Maximal error of 10% in the range of 20 to 100 mm Hg

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

23. Disadvantages Accurate placement of an EVD may be difficult. In some patients, it is simply not possible to place an EVD ,ventricles are compressed Complications include mal position (4-20 %) occlusion (8 %) Hemorrhage (1.1 %) And infection (8.8%)

24. Factors affecting the complications with EVD VENUE OF PLACEMENT EXTENDED TUNNELING( stolke et al > 5cm-83% vs 17% PROPHYLACTIC CATHETER EXCHANGE( no benefit) PROPHYLACTIC ANTIBIOTIC USE ANTIBIOTIC-IMPREGNATED CATHETER ( Rifampin + Minocycline (Zabramski) – 9.4 to 1.3% but cost) Currently infection prophylaxis j. neurotrauma 2007 donot reccomemd antibiotic prophylaxis for evd

25. ICP waveforms Flow of 3 upstrokes in one wave. P1 = (Percussion wave) represents arterial pulsation& reflects cerebral flow P2 = (Tidal wave) d/t retrograde venous pulse of the jugular against cortical veins represents intracranial compliance P3 = ( Dicrotic wave) represents venous pulsation In normal ICP waveform P1 should have highest upstroke , P2 in between and P3 should show lowest upstroke . On eyeballing the monitor, if P2 is higher than P1 – it indicates intracranial hypertension.

26. • ICP waveform – pulsatile • Baseline is referred to as ICP • Magnitude of baseline, amplitude & periodicity of pulsatile components • Earliest sign of ↑ ICP – Changes in pulsatile components

27. ↑⁄↓ amplitude Increasing CSF volume (or decreased) If a large volume of CSF is drained off, the waveform will decrease in amplitude. Missing bone flap

28. Prominent P1 wave Prominent P1 wave Diminished P1 wave The systolic BP is too high • If the systolic BP is too low , P1 decreases and eventually disappears,leaving only P2. • P2 and P3 are not changed by this.

29. Prominent P2 wave The mass lesion is increasing in volume The intracranial compliance has decreased An inspiratory breath hold (as ICP will also rise) I f P2 is higher than P1 – it indicates intracranial hypertension

30. Diminished P2 and P3 waves Hyperventilation Rounded ICP waveform--I CP critically high

31. Lundberg's classification of ICP waves. Lundberg N: Continuous recording and control of ventricular fluid pressure in neurosurgical practice.

32. Lundberg A wave A waves are pathological

33. 20% severe TBI Mean wave >50 mm Hg Result of an increase in cerebro vascular blood volume due to vasodilation . Plateau waves are a normal compensatory response to decreases in CPP Triggered by a precipitating factor( eg -hypotension, desaturation , high pco2) decrease CPP ,leading to an intracerebral vasodilatory cascade increased CBV increased ICP in non compliant intracranial system Occurs when ICP exceeds the limit of cerebral compliance .

34. 4 phases: 1. Drift phase : ↓ CPP → vasodilatation 2. Plateau phase : Vasodilatation → ↑ ICP 3. Ischemic response phase : ↓ CPP → Cerebral ischemia → Brainstem vasomotor centres → Cushing response 4. Resolution phase : Cushing response →Restores CPP

35. LUNDBERG B WAVES Mean wave >20-50mmHg Possibly not d/t increased ICP, may be d/t respiratory changes &variations in CBF Relate to vasodilatation secondary to respiratory fluctuations in PaCO2 Reflects ↑ ICP in a qualitative manner Suggests that lundberg A waves may form

36. Lundberg C waves • More rapid sinusoidal fluctuation (0.1 Hz) • Corresponds to Traube-Hering Meyer fluctuations in arterial pressure brought about by oscillations in baroreceptor and chemoreceptor reflex control systems • Sometimes seen in normal ICP waveform • High amplitude – pre-terminal, seen on top of A waves

37. When to pull the EVD out? CT evidence of resolution of cerebral oedema, and Improvement of ICP (consistently under 20-25) Or if the EVD is infected.

38. FIBEROPTIC INTRACRANIAL PRESSURE MONITOR Fiberoptic devices for ICP monitoring in which the catheter tip measures the amount of light reflected off a pressure-sensitive diaphragm . The most widely studied fiberoptic device is the Camino fiberoptic ICP monitoring device ( Integra Neuroscience , Plainsboro, NJ).

39. Adavntages E ase of insertion- right frontal Can be inserted in severely compressed ventricles or those with midline shift Accuracy low complication rate Disadvantages Zero drift .(Recalibration cannot be performed 2 mm Hg (first 24 hrs); 1 mm Hg (first 5 days) – Manufacturer 0.5 – 3.2 mm Hg drift – Actual) Mechanical problems (breakage or dislocation of fibrooptic cables )

40. The subarachnoid screw (bolt ) A subdural 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. driver Drill bit BOLT

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

44. Advantages can be placed in various compartments , including the ventricle , parenchyma, and subdural space Disadvanteges Less accurate.

45. Spiegelberg Parenchymal Transducer 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 .

46. Emerging Technology Spielberg Compliance monitor Compliance is defined as change in volume per unit change in pressure A low compliance state means that a small change in volume lead to a large change in pressure Inverse relationship between compliance and ICP To measure compliance, the monitor injects a small amount of air into the air balloon pouch and measures the pressure response to this change in volume

47. Noninvasive Intracranial Pressure Monitoring optic nerve sheath diameter (ONSD), which can be measured by ultrasound, correlates with ICP . demonstrated a strong linear relationship betweenn ONSD and ICP. But the critical value of ONSD for detecting elevated ICP (ICP >20 mm Hg) is different in the various studies , thus limiting its potential use at this time

48. The Technique of Optic Nerve Sheath Ultrasound Select the high frequency linear array probe. Apply ultrasound gel liberally to the closed eyelid. If desired, a clear thin dressing ( e.g. IV cannula dressing) can be used as a barrier between the closed eyelid and the gel medium although this is not strictly necessary. Resting the probe hand on a bony structure such as the forehead or brow ridge S tabilises the image and lowers the risk of inadvertent pressure on the globe. Place the ultrasound probe lightly over the gel in a transverse orientation initially. There should neither be any direct contact of the probe with the eyelid nor pressure exerted on the globe. The probe marker should be orientated laterally •.

49. With small, subtle movements scan from side to side (i.e. temporal to nasal), slowly angling the probe superiorly or inferiorly to bring the optic nerve into view. The nerve will appear as a ‘black stripe’ running posteriorly from the rear of the globe. The goal is to centre this on the monitor. If the lens or iris is not seen in your image, the imaging plane is likely off-axis and may result in an underestimation of ONSD. The globe should also be scanned in the parasagittal plane, with the probe marker superiorly, towards the patient’s forehead. • Both eyes should be scanned, in case of unilateral papilloedema .

50. The time spent in active scanning should be minimised. Once the optimum view has been obtained, store the image either as a frame or a video loop and remove the probe from the eye. Use the caliper function on the ultrasound to enable precise measurement. First locate a point 3 mm posterior to the optic disk. At this point place the calipers at 90 degrees to the axis of the optic nerve to measure the diameter of optic nerve and optic nerve sheath Take the average of two or three measurements for each side.

51. The Anatomy of the Optic Nerve Sheath

52. ONSD Measurement Common cut-off is 5 mm

53. Advantages • reproducibility of measurements • the non-invasive nature of the technique • ready availability of equipment • portability of equipment • rapid performance • relatively low costs • avoidance of ionising radiation • avoidance of patient transport for imaging Disadvantages • lack of a uniform cut-off value • operator dependent • potential risk of pressure injury to the globe

54. Venous Ophthalmodynamometry venous ophthalmodynamometry , which measures venous opening pressure (VOP), to calculate ICP. Drawback -requires dilation of the pupil to perform the measurement. Both ONSD and VOP measurement can be performed only intermittently and therefore can be used just as a screening tool for ICP elevation rather than as a continuous monitor.

55. Tympanic Membrane Displacement TMD gives an idea of Cochlear fluid pressure acts as a surrogate for ICP . 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 ]) But less accurate.

56. Transcranial Doppler Measuring ICP based also on changes in patterns of blood flow velocity in the intracranial arteries, which can be assessed by TCD The Middle Cerebral Artery is considered a biologic pressure transducer whose vessel wall deflects in response to mural pressure , modulating according to the pulsatile waveform of CBF ICP can b e derived with various mathematical models by using various blood flow velocity data & variations in TCD waveform morphologies

57. VEP Delay in visual evoked potentials is observed patient with raised icp

58. 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 from size, percent constriction, latency, constriction velocity, and dilation velocity. • Npi 0 – 5. • Npi < 3 predictor of increased ICP. • Npi abnormalities started 16 hrs prior to peak ICP

59. Guidelines for the management of severe traumatic brain injury. Intracranial pressure threshold. RECOMMENDATIONS •Level I – none •Level II - Initiate Rx at ICP > 20 mm Hg •Level III - combination of ICP values, clinical & CT findings, should determine Rx •ICP of 20–25 mm Hg is upper treatment threshold J Neurotrauma . 2007;24 Suppl 1:S55-8 Brain Trauma Foundation; American Association of Neurological Surgeons ; Congress of Neurological Surgeons; Joint Section on Neurotrauma and Critical Care, AANS/CNS,

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

61. Summary • ICP monitoring & ICP-directed treatment remains the cornerstone 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

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