Neurocritical Care Monitoring. Academic Half Day Critical Care Fellows

Transcription

1 Neurocritical Care Monitoring Academic Half Day Critical Care Fellows

2 Clinical Scenarios for CNS monitoring No Universally accepted Guidelines Traumatic Brain Injury Intracerebral Hemorrhage Subarachnoid Hemorrhage Hydrocephalus Malignant Infarction Cerebral Edema CNS Infections Hepatic Encephalopathy

3 Introduction Goal: To prevent secondary Injury to brain How: Ensure the brain is well perfused and minimize ischemic and pressure induced problems especially parts that are most susceptible

4 Assessment Clinically Monitors Standard Specific ICP CT SVO 2 Cortical PO 2 PRx TCD Cerebral Microdialysis EEG

5 Cerebral Physiology Significant Energy Requirements 3-5 ml O 2 /min/100g tissue (94 % gray matter) Anesthesia, Hypothermia (27 C) (2 ml/min/ 100 gm tissue) Normal Cerebral Blood Flow 50 ml/min/100g tissue Delivers 750 ml/min of blood (15 % CO) O 2 extraction: %

6 Autoregulation

7 CBF in relation to PaCO 2, PaO 2 and ICP

8 Cerebral autoregulation. Dunn L T J Neurol Neurosurg Psychiatry 2002;73:i23-i by BMJ Publishing Group Ltd

9 Etiology of Cerebral Injury Lack of Nutrients/O 2 Isolated deficiency (hypoxia) Decreased perfusion Focal Insult Infarction Ischemic penumbra Avoid Hypoxia Hypotension Hypo or hypercarbia Hyperthermia Hypo or hyperglycemia

10 ICP Monitoring

11 Historical Monro-Kellie Doctrine (1783) 1) Brain encased rigid structure 2) Brain is incompressible 3) Volume of blood in cranial vault is constant 4) Constant drainage of venous blood to make room for arterial blood 1840 s idea of CSF was accepted

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13 Spatial Reserve ml in young individuals ml elderly due to cerebral atrophy

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15 Cranial Contents Brain Blood CSF ICP Management Selective resection Craniectomy Osmolar therapy (Mannitol, HTS) Decrease metabolic rate -hypothermia -sedation / paralysis Head of the bed 30 degrees Mannitol Hyperventilate Drainage Mass Resection

16 Monitoring ICP Useful in Head Injury High Grade SAH ICH Mass lesions Meningitis Stroke Transducer Value of ICP Waveform Analysis Calculation of CPP Information on Intracerebral Compliance

17 ICP Monitoring Reasons for raised ICP Mass lesion Hypercapnea Hypoxemia hyperemia GCS 3-8 and: Abnormal CT: hematoma, contusion, swelling, herniation and compressed cisterns Normal CT: with 2 of the following Age> 40 Uni or bilateral posturing SBP < 90 mmhg

18 Methods to Measure ICP Invasive External Ventricular Drain (EVD) Microtransducer ICP Monitoring Devices Non Invasive Transcranial Doppler (TCD) Tympanic membrane Displacement (TMD) Optic Nerve Sheath Diameter MRI and CT Scans Fundoscopy/papilledema

19 Global versus Local Pressure Smaller pressure gradients within CNS exist across specific compartments No significant gradients under physiological conditions ICP probably best monitored as close to expanding lesion as possible No conclusive data as to circumstances of pressure gradients in CNS nor where routine bilateral ICP monitoring should be done

20 Anatomical Locations for Invasive Monitoring

21 EVD Gold Standard Monitoring, drainage of csf, administration of medication Insertion: traditional coronal burr hole at kocher s point with tip of evd in 3 rd ventricle

22 Bleeding: 5.7 % ( ) 0.61% clinically important (neurological deficits/surgical intervention) Infection Various sites, incorrect placement (reoperation), catheter defect 0-27% (3-12%) OR, prophylactic abx, tunnel catheter, minimal handling,? Silver impregnated catheters

23 Normal ICP: varies with age and position (supine) adult: 5-15 mmhg Children: 3-7 mmhg Infants: mmhg CPP: MAP- ICP Normal autoregulation between mmhg

24 ICP Signal Normal ICP waveform has flow of 3 upstrokes P1: (percussion wave) arterial pulsation P2: (tidal wave) intracranial compliance P3: (dicrotic notch) (? Venous pulsation / aortic valve closure) P1 P2 P3

25 The volume pressure curve. Dunn L T J Neurol Neurosurg Psychiatry 2002;73:i23-i by BMJ Publishing Group Ltd

26 ICP treatment Elevated ICP can lead to herniation and irreversible brain damage and death Elevated ICP may lead to increased brain damage and increase cerebral edema Any cerebral lesion may cause set of vasomotoric paralysis and disrupt autoregulation

27 Intracranial herniations. Dunn L T J Neurol Neurosurg Psychiatry 2002;73:i23-i by BMJ Publishing Group Ltd

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29 Waveform Analysis

30 Cerebral autoregulation. Dunn L T J Neurol Neurosurg Psychiatry 2002;73:i23-i by BMJ Publishing Group Ltd

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32 Lundberg A, B and C Waves Lundberg A: *** Plateau Waves*** Pathological, severe loss of autoregulation, irregularly and without warning Rapid increase and decrease in pressure of mmhg lasting 5-20 min indicative of impending herniation Lundberg B: oscillations of waves/min crescendo manner to 5-30 mmhg higher than baseline associated with unstable ICP and vasospasm and velocity in MCA Lundberg C: 4-8 waves/min, smaller amplitude physiological interaction of cardiac and respiratory system

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36 With one line change make the equation true IV = III + III VI = III + III III + III = III III = III = III Cognitively impaired, sleep deprived

37 Using ICP Calculating CPP CPP=MAP-ICP Looking at tissue perfusion pressure Goal mmhg (? 75 mmhg) Probably closer to MAP of May look at affects on ICP Perhaps another technology Relationship between ICP and Outcome Sustained elevation (>20 mmhg) associated with poor outcome My have lower mortality when ICP monitored and acted upon

38 ICP Despite newer technologies Remains robust Valuable information gained Therapeutic device Informs patient management decisions Has been the Cornerstone of management in the ICU of Acute Brain Injury How good is the foundation??

39 GCS 8 + abnormal CT: 53 63% had increased ICP GCS 8 + normal CT: 13 % had increased ICP Patients >40 years, SBP < 90 mmhg or posturing had similar rates of increased ICP as group with abnormal CT head

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46 Outcome GCS >= OR a 3.07 se b 1.49, 95% CI c p- value <0.01 Hospital 28- day Mortality Mortality Overall , GCS < , GCS >= , < 0.01 a OR= odds ratio adjusted for age, apache, increased ICP on CT, mannitol, year of admission, craniotomy, subdural hematoma, diffuse axonal injury, systolic blood pressure < 90 mmhg and arterial oxygen tension < 70 mmhg b standard error c 95% confidence intervals p= 0.01, p=0.03 for interaction

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50 Criticisms of study: External validity Ecuador & Bolivia E.g. 19% used barbiturates Access to rehabilitation Intraparenchymal monitors vs. EVD Is ICP the correct intervention? Is a trial of ICP monitoring the right question?

51 SjVO 2 Monitoring Cerebral Oxygen Use 1980 s-1990 s: Fiberoptic technologies Bedside oximetry SjVO 2 Monitoring Determination for ischemia Monitor effects of therapy for raised ICP

52 SjVO2 Monitoring Insertion Retrograde IJ line insertion usually Right Catheter Cannula: intermittent aspiration/sampling Fiberoptic: continuous

53 SjVO 2 Monitoring Problems Line Placement Contamination Slow blood aspiration Impede venous drainage

54 SjVO 2 Monitoring Normal % Global measure Doesn t detect local ischemia Specific not sensitive measurement tool May be useful in determining ICP treatment interventions Ex. hyperventilation

55 SjVO 2 Monitoring SjVO 2 < 50 % Increased demand High ICP Pain Seizure Decreased Supply Hypoxemia Hypotension Low cardiac output Anemia hyperventilation SjVO 2 > 80 % Brain hyperemia Seizures/shunt Sepsis Brain death (necrosis) Reduced Demand Sedation/ paralysis hypothermia

56 SjVO 2 Monitoring Cerebral Oxygen Extraction CEO 2 = SAO 2 -SjVO 2 SAH with Vasospasm CEO 2 may increase prior to neurological deficits May be able to track vasospasm with CEO 2

57 SjVO 2 Monitoring Limitations Invasive Sampling errors Low values trend toward poor outcomes Never shown as sole treatment to affect outcome Uses Assessing risk of ischemia Adjuvant to ICP monitoring

58 Cortical PBO 2 Monitor (LICOX) Newer Direct placement of PBO 2 sensing electrode on cerebral cortex at time of craniotomy Monitors PbO2, PbCO2, ph and temperature PbO2: mmhg

59 Critical range: < 10 mmhg is high risk for ischemia Probably target values > mmhg Where do you insert? Contusion Penumbra Normal

60 Does PbO2 add anything to current regimen?: May target areas that are vulnerable that are currently assessed by our available modalities Weaknesses: Focal hypoxemia, not global Does not actually measure intracellular hypoxia Role of Microdialysis!

61 Neurosurgery 2011;69:1037

62 J Neurosurg 2010;113:571

63 J Neurosurg Nov;103(5):

64 In TBI, cerebral autoregulation is lost especially in peri-injury neuronal tissue and CBF becomes linearly dependent on CPP (therefore, directly proportional to MAP and inversely proportional to ICP) Resuscitation. 2001;22:

65 Normal physiology Autoregulation maintains constant CBF Increased MAP = cerebral vasoconstriction Decreased MAP = cerebral vasodilation Pressure reactivity index (PRx) Correlation coefficient of MAP & ICP Ranges between - 1 and +1

66 PRx Positive values cerebral autoregulation lost A raised MAP results in increased ICP Negative values cerebral autoregulation intact Reflects a finding of the MAP and ICP varying in opposite directions Aim Find a CPP at which the brain is autoregulating

67 What do you need? Continuous ICP and MAP monitoring ICM+ software Integrates fluctuations of MAP & ICP Generates a continuous correlation coefficient (PRx)

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75 Transcranial Ultrasound (TCD)

76 Transcranial Ultrasound Non invasive method to measure CBF velocity Continuous or intermittent Most described for vasospasm post SAH Vasospasm: Increased flow velocity (Poiseulle) Ratio of ICA :MCA allows monitoring independent of ICP rise Surg Neurol 2006; 65: BJA 2005; 94:

77 EEG Diagnosis of Seizure Intermittent versus Continuous Subclinical Seizure Limited versus Multichannel

78 Seizure and underlying pathology Condition Seizures % Status % Nonneurologic ICU Ischemic stroke SAH ICH HIE TBI Crit Care Med. 2013;41:1

79 Crit Care Med. 2013;41:1

80 Clinical utility in TBI Seizures result in increased CMRO 2 CMRO 2 = CBF = ICP Without ceeg, the cause of increased ICP is missed Consequence Ineffective therapeutic strategies utilized for ICP control Osmotherapy, temperature control, decompression etc

81 Cerebral Microdialysis So far Global view only Not exactly sure about areas at greatest risk Concept of local monitoring Described in 1960 s available since the 1990 s Hollow fibers miniaturization

82 Cerebral Microdialysis Semipermeable membrane Perfuse with RL Molecular transfer relative to concentrations Regular sampling or continuous online analysis

83 Cerebral Microdialysis Allows local molecular concentration analysis In theory any dialysate molecule Neuro: Lactate Glutamate Lactate/Pyruvate ratio Neurotransmitters Glucose Glycerol Problems Equilibrium incomplete Calibration of assay needed Placement? Clinical

84 Camino Transmit light via fiber optic cable towards displaceable mirror Change in ICP move mirror and difference in intensity reflected in ICP value Most commonly placed intraparenchymal Epidural poor accuracy (overestimate mean of 9 mmhg up to 30 mmhg) Subdural Superior to Epidural Drift up to 2 mmhg a day Cannot be recalibrated

85 Summary Cerebral Monitoring Essential as Clinical Information may be limited ICP Monitoring probably useful may not be as helpful in isolation Diagnosis Treatment Monitoring of Response Others are adjuvant but maybe of significant value