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  • 1. Neuromonitoring Techniques in the Neuro ICU: Brain Tissue Oxygenation Shelly D. Timmons, MD, PhD, FACS, FAANS Director of Neurotrauma Geisinger Health System July 17, 2011
  • 2. Learning Objectives
    • The attendee will:
      • Be familiar with indications for use of brain tissue oxygenation in traumatic brain injury patients
      • Understand potential pitfalls and complications of brain tissue oxygenation monitoring
      • Understand commonly employed treatments for low brain tissue oxygenation
  • 3. Balanced Approach
    • Following Guidelines
    • Tailored Therapy
  • 4. TBI Treatment Goals
    • Actions
    • Reduction of intracranial pressure
    • Maintenance of cerebral perfusion
    • Avoidance of Tissue Hypoxia
    • Goals
    • Prevention of Secondary Injury
    • Reduced Mortality
    • Improvements in Functional Outcome
  • 5. ICP MAP CBF P bt O 2 Brain Temp Na Osm Plt PT PTT Hgb Hct ABG Gluc Microdialysis CPP SjvO 2 EEG ECOG Neurological Exam Imaging Operative Findings
  • 6.
    • Indicator of oxygen extraction by brain
    • Measures O 2 saturation in returning blood
      • Compare with arterial O 2 saturation  Arteriovenous Oxygenation Difference (AVDO 2 )
      • Used to assess CMRO 2
    • Variations are common from a variety of causes
    • Not commonly used—typically in clinical research centers
    Jugular Venous O 2 Saturation
  • 7. Jugular Venous O 2 Saturation
    • High S jv O 2 correlates with
      • Hyperemia / High CBF
      • BUT also correlates with low oxygen extraction in the brain indicating ischemia
      • p bt O 2 is a more direct evaluation of relative cerebral ischemia
    From: Anesth Analg. 2000 Mar;90(3):559-66 Schell RM, Cole DJ. Techniques may be complimentary
  • 8.
    • Xenon CT
    • PET
    • MRI
    • CBF Monitor
    • Future
      • Near Infrared
      • Non-Invasive
    Cerebral Blood Flow
  • 9. Cerebral Blood Flow Monitor
    • Absolute, real-time continuous perfusion
    • Measured from 0 - 200 ml/100g/min.
    • Thermal diffusion probe -- a minimally invasive (<1 mm diameter), flexible, interstitial catheter
  • 10.
    • Current technology allows for focal measurements, not global
    • Not a stand-alone monitor but good adjunct
    • pB t O 2 v alues can be manipulated through a variety of interventions
      • Choosing appropriate interventions based upon underlying pathophysiology requires thorough knowledge and understanding of multiple parameters
    Brain Tissue Oxygenation (pB t O 2 )
  • 11. Brain Tissue Oxygenation P bt O 2
    • Measures interstitial brain tissue oxygenation (P bt O 2 ) in mm Hg and brain temperature (°C)
    • Probe inserted approximately 35mm below the dura into the white matter of the brain
    • P bt O 2 used in conjunction with current ICP/CPP monitoring methods
  • 12. A closed polarographic probe with reversible electrochemical reactions Brain Tissue Oxygenation P bt O 2
  • 13.
    • Oxygen Accuracy:
      • P bt O 2 0-20 mmHg accuracy is ± 2 mmHg
      • P bt O 2 21-50 mmHg accuracy is ± 10%
      • P bt O 2 51-150 mmHg accuracy is ± 13%
    • Temperature Accuracy: ± 0.2 °C
    Brain Tissue Oxygenation P bt O 2
  • 14. Insertion Technique
    • Small Stab Incision
    • Small Drill Hole
    • Placement of Bolt
    • Zeroing of Catheters
    • Insertion of Catheters
      • ICP
      • Brain Temperature / P bt O 2
  • 15. Techniques
    • ICP Parenchymal Monitor
      • With Ventricular Drainage
        • Advantages
          • Allow for continuous CSF drainage and continuous ICP measurement
          • Allow for intermittent CSF drainage and continuous ICP measurement
          • Allow for fluid-coupled mechanism of ICP confirmation
      • Without Ventricular Drainage
        • Advantages
          • Lower Complication Rate
  • 16. Brain Oxygen Monitoring Guidelines 2008
    • Level I
      • Insufficient Data
    • Level II
      • Insufficient Data
    • Level III
      • Jugular venous saturation (<50%) or brain tissue oxygen tension (<15 mm Hg) are treatment thresholds
      • Jugular venous saturation or brain tissue oxygen monitoring measure cerebral oxygenation
  • 17. Indications
    • Severe TBI (GCS 3-8)
    • Blunt Vascular Injury
  • 18. P bt O 2
    • Normal: 25-35 mmHg
    • Low P bt O 2 occurs frequently in the first 24 hours after injury
    Bardt TF, Unterberg AW, Hartl R, et al. Acta Neurochir 1998; 71:153–156 Dings J, Ja¨ger A, Meixensberger J, et al. Neurol Res 1998; 20(Suppl 1):S71–S75
  • 19.
    • “ Since the first (mostly European) reports of continuous monitoring of P bt O 2 in humans, investigators have consistently shown correlations of P bt O 2 values with clinical course and outcomes, and of effects on P bt O 2 by various treatment interventions…”
    Timmons, SD Crit Care Med . 2010 Sep;38(9 Suppl):S431-44. These effects may be independent of effects on ICP or CPP
  • 20. P bt O 2 and Mortality
    • Risk of death increases
      • < 15 mmHg for 30 minutes
      • < 10 mmHg for 10 minutes
    • P bt O 2 < 5 mmHg
      • high mortality
    • P bt O 2 < 2mmHg
      • neuronal death
    Bardt TF, Unterberg AW, Hartl R, et al. Acta Neurochir 1998; 71:153–156 N.B. Good outcomes are possible even with hypoxic episodes
  • 21. P bt O 2 and Mortality
    • Time with
    • P bt O 2 < 10 mm Hg
    • < 30 minutes
    • vs.
    • > 30 minutes
    Bardt et al. 1998 6-Month GOS 35 Severe TBI Pts.
  • 22. Low P bt O 2 and Mortality
    • Association with increased mortality
      • Increasing duration of time < 15
      • Any value < 6 also
    Valadka AB, Gopinath SP, Contant CF, et al. Crit Care Med 1998; 26:1576–1581 Dings J, Ja¨ger A, Meixensberger J, et al. Neurol Res 1998; 20 (Suppl 1):S71–S75
  • 23. Low P bt O 2 and Mortality
    • Increased mortality with shorter time periods as P bt O 2 decreases
    • 50% Mortality
    • <5 30 minutes
    • <10 105 minutes
    • <15 240 minutes
    6-Month GOS 101 Severe TBI Patients Van den Brink et al. 2000 Effects of obliterated cisterns
  • 24. Low P bt O 2 and Mortality
    • Desaturations can occur even with acceptable ICP and CPP levels
    • These associated with higher mortality
    • Targeted therapies can improve outcome, even in the face of normal ICP/CPP
    • Additional benefit in the diffuse injury group
    Stiefel MF, Spiotta A, Gracia VH, et al. J Neurosurg 2005; 103:805–811 Stiefel MF, Udoetuk JD, Spiotta AM, et al. J Neurosurg 2006; 105:568–575 Narotam PK, Morrison JF, Nathoo N J Neurosurg 2009; 111:672–682
  • 25. Low P bt O 2 Causes
    • Several correctable causes of cerebral oxygen desaturations
      • Insufficient CPP
      • Vasospasm
      • Pulmonary atelectasis resulting in hypoxemia
      • Anemia
      • Premature interruption of ICP-controlling medications
    Artru F, Jourdan C, Perret-Liaudet A, et al. Neurol Res 1998; 20:S48–S51
  • 26. Techniques to Improve P bt O 2
    • Elevation of CPP
      • Increases in Blood Volume, MAP
      • Decreases in ICP
    • Hypertonic saline
    • Pressors
    • Sedatives
    • Barbiturates
      • Independent of fx on ICP 
      • cerebral metabolism
    Artru F, Jourdan C, Perret-Liaudet A, et al. Neurol Res 1998; 20:S48–S51 Cormio M, Gopinath SP, Valadka AB, et al. J Neurotrauma 1999; 16:927–936 Johnston AJ, Steiner LA, Coles JP, et al. Crit Care Med 2005; 33:189–195 Oddo M, Levine JM, Frangos S, et al. J Neurol Neurosurg Psych 2009; 80:916–920 Narotam PK, Morrison JF, Nathoo N J Neurosurg 2009; 111:672–682 Kiening KL, Ha¨rtl R, Unterberg AW, et al. Neurol Res 1997;19:233–240 Imberti R, Fuardo M, Bellinzona G, et al. J Neurosurg 2005; 102:455–459 Thorat JD, Wang EC, Lee KK, et al. J Clin Neurosci 2008;15: 143–148 Chen HI, Malhotra NR, Oddo M, et al. Neurosurgery 2008;63:880–997
  • 27. Techniques to Improve P bt O 2
    • Transfusion of Packed Red Blood Cells (PRBCs)
      • Increases P bt O 2
      • Improved oxygen-carrying capacity of the blood
      • Effect more prominent in the presence of higher lactate/pyruvate ratios (mitochondrial dysfunction)
    Smith MJ, Stiefel MF, Magge S, et al. Crit Care Med 2005; 33:1104–1108 Leal-Noval SR, Rincon-Ferrari MD, Marin-Niebla A, et al. Intensive Care Med 2006; 32: 1733–1740 Zygun DA, Nortje J, Hutchinson PJ, et al. Crit Care Med 2009; 37:1074–1078
  • 28. Techniques to Improve P bt O 2
    • Transfusion of Packed Red Blood Cells (PRBCs)
      • Increases in P bt O 2 independent of
        • CPP changes
        • Cardiac index
        • Peripheral oxygen saturation
        • FiO 2
    Artru F, Jourdan C, Perret-Liaudet A, et al. Neurol Res 1998; 20:S48–S51 Leal-Noval SR, Rincon-Ferrari MD, Marin-Niebla A, et al. Intensive Care Med 2006; 32: 1733–1740 Smith MJ, Stiefel MF, Magge S, et al. Crit Care Med 2005; 33:1104–1108
  • 29. Techniques to Improve P bt O 2
      • Conflicting data exist on baseline P bt O 2 effects on improved P bt O 2
    • Age of the transfused blood products may affect efficacy (storage > 19 days)
    Leal-Noval SR, Rincon-Ferrari MD, Marin-Niebla A, et al. Intensive Care Med 2006; 32: 1733–1740 Zygun DA, Nortje J, Hutchinson PJ, et al. Crit Care Med 2009; 37:1074–1078 Weigh well-documented risks vs. the potential benefit of protection from secondary injury
  • 30. Techniques to Improve P bt O 2
    • Increasing Ventilatory FiO 2 to supranormal levels (normobaric hyperoxia) can increase P bt O 2
    • BUT
    • May not lead to better CBF or cerebral metabolic rate of oxygen consumption
    Tolias CM, Reinert M, Seiler R, et al. J Neurosurg 2004; 101: 435–444 Nortje J, Coles JP, Timofeev I, et al. Crit Care Med 2008; 36:273–280 Diringer MN, Aiyagari V, Zazulia AR, et al. J Neurosurg 2007; 106: 526–529
  • 31. Techniques to Improve P bt O 2
    • Primary lung function can affect the cerebral oxygenation response to administration of hyperoxic challenges.
    • P a O 2 /FiO 2 ratios of 200–250 are associated with decreased cerebral oxygenation responsiveness
    • Important to determine the pulmonary status
      • Monitoring of P a O 2 /FiO 2 ratios
      • Early diagnosis of ventilator-acquired pneumonia
    Rockswold GL, Solid CA, Paredes-Andrade E, et al. Neurosurg 2009; 65:1035–1042 Rosenthal G, Hemphill JC, Sorani M, et al. Crit Care Med 2008 Jun; 36:1917–1924
  • 32. Techniques to Improve P bt O 2
    • Decompressive Hemicraniectomy
    Stiefel MF, Heuer GG, Smith MJ, et al. J Neurosurg 2004; 101:241–247 Ho CL, Wang CM, Lee KK, et al. J Neurosurg 2008; 108:943–949 Used w/ permission: William Coplin, M.D. Contralateral to Surgical Site
  • 33. Relationship to CBF
    • Correlation shown with Xenon CT, CT perfusion studies, and non-invasive monitoring
    • Limitations in measurement ability
    • Non-correlated variations also occur
      • Changing oxygen demands and delivery
      • CO 2 reactivity
      • Coupling/uncoupling of cerebral metabolism to CBF in patients with brain pathology
  • 34. Oxygen Diffusion
    • Impaired after brain injury
      • Perivascular edema
      • Endothelial edema
      • Microvascular collapse
    • Resulting in
      • Impaired oxygen extraction
        • Even with hypoperfusion (Extraction should be higher)
    Low P bt O 2 may be more closely related to impaired oxygen diffusion rather than oxygen delivery or metabolism. Diringer MN, Aiyagari V, Zazulia AR, et al. J Neurosurg 2007; 106: 526–529 Menon D, Coles JP, Gupta AK, et al. Crit Care Med 2004 Jun; 32: 1384–1390 Rockswold SB, Rockswold GL, Zaun DA, et al. J Neurosurg 2010; 112:1080–1094 Mannitol
  • 35. Potential Problems
    • Pitfalls
    • Catheters are stable
    • Factors affecting readings:
      • Calibration over first two hours
      • Dislodgement of catheter
      • Catheter breakage
    • Complications
    • Complication rates are low
      • Hematoma
      • Infection
    Van Santbrink H, Maas AIR, Avezaat CJJ Neurosurgery 1996; 38: 21–31 Dings J, Meixensberger J, Roosen K J Neurological Res 1997; 19:1–5 Van den Brink WA, Van Santbrink H, Steyerberg EW, et al. Neurosurgery 2000; 46: 868–878 Anderson, RCE, Kan P, Klimo P, et al. J Neurosurg (Pediatrics 2) 101:53–58, 2004
  • 36. Assessing Physiology of Secondary Injury
    • “ Global”
      • ICP
      • CPP
      • CBF
      • S jv O 2
    • “ Regional”
      • P bt O 2
      • Microdialysis
      • PET
      • ECOG
  • 37. ICP MAP CBF P bt O 2 Brain Temp Na Osm Plt PT PTT Hgb Hct ABG Gluc Microdialysis CPP SjvO 2 EEG ECOG Neurological Exam Imaging Operative Findings
  • 38. Future of Neuromonitoring
    • Storage & Interpretation of Ever More Continuous Physiological Data
    • Multimodality Monitoring
    • Linkage to Events
      • Movements/Transport
      • Imaging
      • Surgeries and Other Procedures
      • Family Visits
      • Nursing Care
        • Bathing/Turning/Suctioning
      • Drug Administration
      • O 2 Desaturations
      • Lab Derangements
      • Seizures
    • Linkage to Examination
      • GCS
      • Pupils
    • Ultimately
    • Linkage to Outcomes Will Aid in Research and More Evidence-Driven Approaches to TBI
    Not Just ICP Control But Also Metabolism-Driven Therapy
  • 39. TBI Advisor Evidence-Based Treatments  Interventions
  • 40. Thank You [email_address]

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