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2009.12.14 林楠

The Effects of Arterial Carbon Dioxide Partial Pressure and Sevoflurane on Capillary Venous Cerebral Blood Flow and Oxygen Saturation During Craniotomy. Klaus Ulrich Klein, Martin Glaser, Robert Reisch, Achim Tresch, Christian Werner, Kristin Engelhard Vol. 109, No. 1, July 2009

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2009.12.14 林楠

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  1. The Effects of Arterial Carbon Dioxide Partial Pressure and Sevoflurane on Capillary Venous Cerebral Blood Flowand Oxygen Saturation During Craniotomy Klaus Ulrich Klein, Martin Glaser, Robert Reisch, Achim Tresch, Christian Werner, Kristin Engelhard Vol. 109, No. 1, July 2009 ANESTHESIA & ANALGESIA 2009.12.14 林楠

  2. BACKGROUND • Intraoperative routine monitoring of cerebral blood flow and oxygenation remains a technological challenge. • oxygen-to-see, O2C™ device patients subjected to craniotomy regional cerebral blood flow (rvCBF) blood flow velocity (rvVelo) oxygen saturation (srvO2) hemoglobin amount (rvHb) at the capillary venous level physiological principle of carbondioxide reactivity of cerebral vasculature

  3. laser-Doppler flowmetry photo-spectrometry

  4. METHODS 26 ASA II–III patients, elective intracranial surgery Induction Remifentanil 0.3-0.4 ug/kg/min Propofol 2 mg/kg Atracurium 0.5 mg/kg Radial arterial line Intubation FiO2 = 0.5 PEEP = 5 mbar maintenance Remifentanil 0.1-0.4 ug/kg/min Sevoflurane 1.4%(n=13) & 2.0%(n=13)

  5. METHODS ----O2C Device 2 mm depth 8 mm depth cerebral cortex next to the site of surgery 2 channel Probe head： Width 12mm Height 5.5mm Length 44.5mm Probe length 300cm enclosed with epoxy casting resin（环氧树脂）and is nontoxic to human tissue. Conducted from the cortex directly

  6. Lasting 1 min 3 repetitive Resulting in a total 50-70 Measurements Apply probe Switch off microscope light swab Place the probe on the same area of the tissue Alter PaCO2 by changes in respiratory frequency . After 30 min of steady-state anesthesia METHODS----Intraoperative Measurements Before measurement measurement 2 g 头孢呋新 IV 校准 酒精消毒 消过毒的聚亚胺酯覆盖探头 热生理盐水封表面 First at low PaCO2 (35) Or higher PaCO2 (45)

  7. Physiological Variables • mean arterial blood pressure • heart rate • bladder temperature • Inspired oxygen fraction • hemoglobin concentration • Hematocritelevel • peripheral oxygen saturation(SaO2) combined IV cafedrine-Hcl 50 mg and theodrenaline-Hcl 2.5 mg (0.25 mL Akrinor) Controlled and maintained at stable level over time Oxygen content of blood (CaO2) =1.39 * Hb * SaO2 +Pao2 *0.003

  8. Statistical Analysis---- SPSS 13.0 (SPSS, Chicago, IL) rvCBF, rvVelo, srvO2, rvHb Sevoflurane End-tidal concentration 1.4% 2.0% Target PaCO2 35mmHg 45mmHg Cerebral depth 2 mm 8 mm

  9. RESULTS

  10. RESULTS Changes within range of 10%

  11. RESULTS • Higher levels of Paco2 increased rvCBF, rvVelo, and srvO2 independent of 1.4% and 2.0% sevoflurane end-tidal concentration • RvVelo and srvO2 were higher in 8 mm compared with 2 mm cerebral depth. • Levels of rvHb were positively correlated to end-tidal sevoflurane concentration but not dependent on Paco2 or cerebral depth(P<0.005)

  12. Higher PaCO2 8mm compared 2mm Sevoflurane 1.4%, e.t.

  13. Sevoflurane 2.0%, e.t.

  14. Sevolurane 1.4% vs. 2.0% on rvHb <

  15. RESULTS

  16. Increased Cerebral perfusion srvO2 Oxygen availability During meaurements rvHb No blood loss DISCUSSION---srvO2, rvHb

  17. 20 80 DISCUSSION----cerebral vessels

  18. DISCUSSION----cerebral vessels Extracelluar fluid pH affecting vessel resistance Altered PCO2 affect all cerebral vessels

  19. Resistance arterioles dilated Microvascular pressure gradient rvVelo rvCBF 50% PCO2 9mmHg rvVelo 45% DISCUSSION----rvVelo Hypercapnia dilates smaller arterioles more than larger ones

  20. DISCUSSION----Absence of CO2 response • (1) Structural damage to cerebral tissue through surgery or local edema • (2) capillary perfusion: shunting, recruitment, increase in capillary diameter • (3) invalid measurements: no”gold standard” • Sev concentration had no effect on rvCBF,rvVelo and srvO2 suggesting that CO2 reactivity was preserved even with a higher sevoflurane concentration.

  21. DISCUSSION----2mm&8mm depth • O2C srvO2 higher in 8mm VS 2mm • Polarographic oxygen electrodes （极谱氧电极） ptiO2（脑组织氧分压）higher for cortical area VS subcortical area VS Application pressure of probe, temperature, surgery, diffusion of CO2, failure of the device.

  22. DISCUSSION----以上各值综合分析

  23. DISCUSSION----以上各值综合分析 • CBF=CPP/CVR （1）CPP不一定与CBF成正比 （2）即使CPP够，CBF也不一定够 Metabolic control (or 'metabolic autoregulation') Pressure autoregulation Chemical control (by arterial pCO2 and pO2) Neural control 血流不够代谢所需 • SjvO2 = CaO2 - CMR/CBF 血流超过代谢所需

  24. limitations ①If >20 repetitive measurments using laser-Doppler； but 3 repetitive measurements in this study(clinical) ②the size and location of craniotomy. >3cm allow for placement of the probe ③Ambient light may bias the spectrophotometric, cover the probe

  25. Comparison with other techniques • The jugular bulb oxygen catheter Adavantage ·Global venous oxygen saturation Disadavantage ·Can not measure regionally

  26. Comparison with other techniques • PtiO2 (Licox, Neurovent-PTO) Adavantages ·Accurate ·Stable ·Can not affect by motion artifacts Disadavantages ·Tissue damage ·Bleeding ·Infections ·Near A vessel elevate

  27. Comparison with other techniques • Transcranial near-infrared spectroscopy (INVOS, NIRO-200) Adavantages ·noninvasive ·bedside measure of cerebral oxygenation ·real-time data ·several regions of the brain Disadavantages ·only two wavelengths

  28. Conclusion • The O2C device provides real-time intraoperative measurements of cerebral microcirculation during craniotomies; • Levels of rvCBF, rvVelo and srvO2 in 2 and 8 mm cerebral depth increased with higher PaCO2.These changes were independent of Sevoflurane(1.4% vs 2.0%); • Data suggest that the device allows detection of regional changes in blood flow, oxygen saturation, and hemoglobin amount in response to different PaCO2 levels in predominant venous microvessels. Further studies---- cerebral ischemia and hypoxia…

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