Lisa T. Hannegan, MS, CNS, ACNP. Department of Neurological Surgery University of California, San Francisco

Transcription

1 Lisa T. Hannegan, MS, CNS, ACNP Department of Neurological Surgery University of California, San Francisco

2 Era of Clinical Neuro Monitoring Clinical Examination Heart rate Blood Pressure Body temperature Respiratory Rate Oxygen saturation Central venous Pressure Occasional use of intracranial pressure (ICP) monitoring

3 Era of Physiologic Monitoring Intracranial Pressure Monitoring Occasional use of jugular bulb venous oxygen saturation (SjvO 2 ) monitoring

4 Era of Multimodality Monitoring and Neurophysiologic Decision Support Goal-directed therapy Wartenburg et al., Critical Care Clinics, 23 (2007)

5 Primary Brain Injury Due to an illness or condition Secondary Brain Injury Follows the initial neurologic insult

6 Primary Brain Injury Due to an illness or condition Secondary Brain Injury Follows the initial neurologic insult The primary focus of Neurocritical Care for CNS problems is the prevention, identification, and treatment of secondary brain injury. Claude Hemphill

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9 WHY MONITOR? Detect neurological worsening before irreversible damage occurs Individualize patient care Guide management Monitor response to interventions Understand pathophysiology Design protocols Improve outcome

10 WHAT PROCESSES TO MONITOR? Substrate delivery Blood flow Perfusion Energy failure and cellular stress Intracranial pressure Metabolic byproducts of ischemia

11 WHICH MONITORS? Cardiac and respiratory physiology Heart rate and rhythm, EF etc. FiO 2, TV, PEEP, etc. Intracranial pressure Cerebral perfusion pressure Cerebral Blood Flow Transcranial Doppler, thermal diffusion, laser Doppler flowmetry

12 WHICH MONITORS? Brain oximetry Jugular bulb venous oxygen saturation (SjO2) Brain tissue oxygen tension (PbtO2, NIRS) Oxidative metabolism Cerebral microdialysis (lactate, LPR) Cellular stress Cerebral microdialysis (glutamate, glycerol) Continuous EEG (ceeg)

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14 Monro-Kellie 80% brain 10% circulating blood 10% CSF

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16 P1 Percussive peak P2 Tidal peak P3 Dichrotic notch

17 P1 Percussive peak P2 Tidal peak P3 Dichrotic notch C waves B waves A (plateau) waves

18 Normal pressure 0-10 Threshold to treat >20-25

19 CPP = MAP - ICP

20 CPP = MAP - ICP CPP = MAP JVP (if JVP > ICP)

21 CPP = MAP - ICP CPP = MAP JVP (if JVP > ICP) Must be maintained within normal limits Optimal pressure is mm HG Too low ischemia Too high increased ICP

22 Flow remains constant over a range of CPP Flow is constant from MAP of about This relationship does not hold true with very low CPP, very high CPP and in injured brain. Therefore, DIRECT MEASUREMENT is valuable in injured brain.

23 Kety-Schmidt technique Xenon or krypton nuclear medicine studies SPECT, Xenon CT O 15 PET Perfusion CT or MRI Transcranial Doppler (TCD) These are all static techniques

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26 Commonly used as a non-invasive test of cerebral blood flow in vasospasm related to subarachnoid hemorrhage Uses flow velocity to infer vessel diameter Use of Lindegaard Index to predict vasospasm eliminates elevated velocities related to hyperemia and loss of autoregulation Results are operator-dependent

27 Continuous measurement techniques Laser Doppler Flowmetry Assesses the volume or concentration and flow velocity of red blood cells in a small volume (mm 3 ) and generates a flow signal Thermal Diffusion Quantitative estimation of flow in ml/100g per minute based on the tissue s ability to dissipate heat

28 Real-time measurement of microvascular RBC perfusion in tissue Measured in BPUs

29 Advantages Directly measures flow velocity in a region of interest Many of the probes are MRI compatible Does not need regular calibration

30 Advantages Directly measures flow velocity in a region of interest Many of the probes are MRI compatible Does not need regular calibration Disadvantages Probes are susceptible to artifact Area of flow studied is tiny at 1mm 3 BPUs not directly translatable to physiological data Results vary depending on various blood parameters such as hematocrit

31 Two thermistors at the tip of a flexible catheter embedded in the white matter. The proximal thermistor measures the brain temperature in degrees Celsius

32 Two thermistors at the tip of a flexible catheter embedded in the white matter. The proximal thermistor measures the brain temperature in degrees Celsius The distal thermistor is programmed to a temperature two degrees above the temperature at the proximal thermistor

33 The energy used by the distal thermistor to maintain the temperature 2 degrees higher reflects the tissue blood flow.

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35 Advantages Reflects cerebral blood flow to a region of interest Direct correlation between flow intra-operatively during and after temporary arterial occlusion for aneurysm clipping. (Thome et al., J Neurosurg, 2001) Correlation between thermal diffusion CBF results with PbrO2 in patients with SAH and TBI Jaeger et al, Achta Neurochir, 2005 Larger sampling area than laser Doppler flowmetry

36 Disadvantages Small sample area reflects regional flow Temperature cutoff reduces sampling time in febrile patients Must use another invasive procedure to replace non-functioning catheter

37 Range of values for CBF Normal CBF 50mL/100g/min Loss of normal neuronal function and threshold for tissue ischemia <20mL/100g/min

38 Indications Detection of non-convulsive seizures Characterization of spells such as posturing, eye movements, and unexplained changes in heart rate and blood pressure

39 Indications Detection of non-convulsive seizures Characterization of spells such as posturing, eye movements, and unexplained changes in heart rate and blood pressure Assessment of LOC during sedation and paralysis Detection of ischemia after SAH and during procedures Prognostication

40 Up to 35% of Neuro Intensive Care patients have subclinical seizures Claassen J, et al (2004) Detection of electrographic seizures with continuous EEG Monitoring in critically ill patients. Neurology 62:

41 EEG showing focal right frontal ictal discharges in a patient with localization-related nonconvulsive status epilepticus

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43 Elevated ICP Disturbed cerebral metabolism Glutamate elevations Increased lesional mass effect and midline shift Misdirected treatment and diagnostic evaluations Increased mortality

44 Near Infrared spectroscopy Jugular bulb venous oxygenation Direct brain tissue oxygen tension

45 Tissue oxygen pressure versus oxygen saturation SO 2 is a measure of the oxygen carried bound to hemoglobin with 4 oxygen molecules per hemoglobin molecule. PO 2 is related to the amount of oxygen dissolved in the plasma or tissue

46 Near infrared spectroscopy (NIRS) Measures regional oxygen saturation (rso 2 ) noninvasively

47 Near infrared spectroscopy (NIRS) Measures regional oxygen saturation (rso 2 ) noninvasively Works by by analyzing the differences between absorption spectra of oxygenated and deoxygenated hemoglobin

48 Near infrared spectroscopy (NIRS) Measures regional oxygen saturation (rso 2 ) noninvasively Works by by analyzing the differences between absorption spectra of oxygenated and deoxygenated hemoglobin Normal value for rso 2 is 60-80%

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50 Advantages Non-invasive Simple to apply and change May be useful in operative monitoring for procedures such as carotid endarterectomy

51 Advantages Non-invasive Simple to apply and change May be useful in operative monitoring for procedures such as carotid endarterectomy Disadvantages Limited and variable penetration of infrared light through the skull Inconsistent reliability

52 SjvO 2 is a result of the difference between the cerebral oxygen delivery (supply) and the cerebral metabolic rate of O 2 (CMRO 2 )(demand). SjvO 2 reflects global oxygenation (hemispheric)

53 Dominant internal jugular Position verified by X-Ray Calibration on insertion and every 8 hours

54 Advantages Best use in TBI with global injury associated with hypoperfusion, hypercapnia and elevated ICP Beneficial in SAH and intraoperative use

55 Advantages Best use in TBI with global injury associated with hypoperfusion, hypercapnia and elevated ICP Beneficial in SAH and intraoperative monitoring Disadvantages Limited by changes in PaO 2 and hemodilution Frequent calibration No information about smaller regions of interest Complications Infection jugular thrombosis Pneumothorax increased ICP

56 Range of SjvO 2 Values 50-75% Normal SjvO 2 <50% indicates increased oxygen extraction fraction (OEF) SjvO 2 >75% indicates reduced OEF and hyperemia In comatose patients, even a single desaturation to SjvO 2 less than 50% was correlated with increased mortality Feldman and Robertson, Critical Care Clinics, 1997, 13:51-77

57 Measures regional tissue oxygen pressure in a small area of the brain (P b O 2, P br O 2, P ti O 2, P bt O 2 ) Uses a microcatheter inserted into the brain parenchyma in a region of interest in the white matter Depending on the device, one can also monitor temperature, PCO 2 and ph. Can be tunneled after craniotomy or placed through a multi-lumen bolt Measured tissue volume is ~17mm 3

58 Range of P bt O 2 values Normal P bt O 2 is 20 in white matter and in gray matter Levels consistently >35mmHg correlate with good recovery Levels <20 indicate cerebral hypoxia Levels < 8 mmhg predict poor outcome

59 Normal values for additional modalities P bt CO 2 is 43-55mm Hg Brain tissue ph is 7.2 Brain temperature correlates with core body temperature with a normal of 37 C

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61 Advantages Real-time information about autoregulation Proven impact on patient management and outcome

62 Advantages Real-time information regarding autoregulation Proven impact on patient management and outcome Disadvantages Creates artifact on MRI Invasive therapy Difficult to replace non-functioning probes Regional, not global information

63 A technique used to monitor the chemistry of the extracellular space A thin dialysis probe, infused with saline or artificial CSF mimics a cerebral capillary

64 Measures Glucose (substrate) Lactate (reflects anaerobic metabolism) Pyruvate (reflects carbohydrate metabolism) Lactate to pyruvate ratio (LPR) Glutamate (reflects cell injury) Glycerol (reflects cell membrane breakdown)

65 Reduced glucose and increased lactate correlate with cerebral hypoxia and with death Temporary arterial occlusion results in lowered glucose and pyruvate and also in elevated lactate and glutamate

66 Advantages Probes are MRI safe Microdialysis can be done at the bedside at a regular interval Changes in values are early indications of ischemia

67 Advantages Probes are MRI safe Microdialysis can be done at the bedside at a regular interval Changes in values are early indications of ischemia Disadvantages Focal information Current technology is limited to observation of trends

68 DIALYSIS CONCENTRATION REINSTRUP et al SCHULZ et al CLINICAL USE Glucose (mmol/l 1.7 (+/- 0.9) 2.1 (+/- 0.2) < 2.0 LPR 23 (+/- 4) 19 (+/- 2) > 25 Glycerol (µmol/l) 82 (+/- 44) 82 (+/- 12) > 100 Glutamate (µmol/l) 16 (+/- 16) 14 (+/- 3.3) >15 Reinstrup et al,, Neurosurgery 2000; 47: Schulz et al, J Neurosurg 2000; 93: Table adapted from a presentation by Peter LeRoux, MD, FACS

69 Provide an optimal cellular environment in order to preserve neurologic function and allow the best chance for recovery to occur DeGeorgia and Deogaonkar, The Neurologist, 2005

70 Multimodality monitoring for neurophysiologic decision support Goal-directed therapy Proactive patient care management