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A55
October 14, 2006
9:00 AM - 11:00 AM
Room Hall E, Area B
Is Outcome in Neurosurgery Related to Brain Hypoxia?
Verna L. Baughman, M.D., Onn Paisansathan, M.D., William E. Hoffman, Ph.D., Rodolfo Gatto, M.D., Fady Charbel, M.D.
Anesthesiology and Neurosurgery, University of Illinois at Chicago, Chicago, Illinois
Introduction Neurosurgical patients may have post-operative cognitive dysfunction following surgical procedures, but the reasons are generally unknown (Tuffiash, Tamargo et al. 2003). One possibility is that patients with compromised brain hemodynamics may be unable to regulate brain oxygenation during anesthesia. The purpose of this study was to identify patients in which brain oxyhemoglobin (OHb) concentrations decreased during desflurane anesthesia and compare them to patients who maintained brain oxygenation.

Methods Frontal cortex OHb, deoxyhemoglobin (HHb), brain oxygen saturation (SO2) and total hemoglobin concentration were determined bilaterally every 2 seconds in 16 neurosurgery patients using an Oxiplex TS (ISS, Champaign, IL), starting with the patients awake. Anesthesia was induced with propofol and fentanyl and maintained with desflurane inhalation. Patients were separated by post-hoc analysis to group 1 (n = 8) who maintained OHb above 30% of awake baseline during anesthesia or group 2 (n = 8), that showed a >30% decrease in OHb. Entropy EEG, non-invasive blood pressure and heart rate were measured with the patient awake, at intubation and at 10 minute intervals for 1 hour of desflurane anesthesia. Data were analyzed by repeated measures analysis of variance.

Results Patient demographics were similar between the groups. In group 2, awake baseline OHb and SO2 were lower than the control group and both measures decreased in group 2 during 60 minutes of anesthesia (P < 0.01, figure 1). Blood pressure decreased 20% in both groups (P<0.01). HHb increased during anesthesia in group 2 (P<0.01) but not group 1. Total hemoglobin was 50% lower in group 2 (P<0.01) and did not change in either group during anesthesia. EEG Response Entropy and desflurane requirements were statistically similar between the groups.

Conclusion These results indicate that patients with low baseline brain OHb may be at greater risk for a further decrease in brain oxygenation during anesthesia compared to controls. Although blood pressure decreased in a similar way in both groups, patients with low OHb were unable to regulate brain oxygenation and HHb increased. The data suggest that brain hemodynamic reserve is compromised in some neurosurgery patients and this may lead to tissue oxygen desaturation under anesthetic conditions.

References

1. Tuffiash, E., R. J. Tamargo, et al. (2003). "Craniotomy for treatment of unruptured aneurysms is not associated with long-term cognitive dysfunction." Stroke 34(9): 2195-9.

Figure 1. Brain oxyhemoglobin and blood pressure during desflurane anesthesia. Solid = control (n = 8), gray = brain hypoxia (n = 8). Mean +/- SD. 1 = awake, 2-8 = desflurane anesthesia from 0 to 60 min in 10 min intervals. Awake baseline OHb was different between the groups and decreased during anesthesia in the group with low OHb (P<0.01).[figure1]

Anesthesiology 2006; 105: A55
Figure 1