Effect of pentobarbital on cerebral regional venous O2 saturation heterogeneity.
Observed venous O2 saturation inhomogeneity in the brain implies a microregional imbalance in O2 supply/consumption. We hypothesized that this heterogeneity should be decreased by pentobarbital anesthesia through a reduction in regional metabolic heterogeneity. Male, Long-Evans, approximately 350 g rats were either anesthetized with 50 mg/kg pentobarbital (n = 10) or used as a conscious control group (n = 10, catheters inserted two hours earlier under ether anesthesia). In each rat, regional cerebral blood flow was determined by [14C]iodoantipyrine and regional arterial and venous O2 saturation were determined by microspectrophotometry. In the PB group, the mean blood pressure (107 +/- 7 Torr), heart rate (362 +/- 29/min), average cerebral blood flow (63 +/- 19 ml/min/100 g), and average cerebral O2 consumption (3.7 +/- 1.2 ml O2/min/100 g) were lower than those values in the conscious group (128 +/- 15, 474 +/- 44, 112 +/- 40, and 7 +/- 3), respectively. O2 extraction did not change after pentobarbital anesthesia. However, the dispersion of venous O2 saturation narrowed. The distribution of O2 saturations in 373 cerebral veins of anesthetized rats had a significantly reduced coefficient of variation [C.V. = 100 x (S.D./mean) = 13] as compared to a C.V. of 18 in 320 veins in conscious rats. Thus, pentobarbital anesthesia reduced the microregional venous O2 saturation inhomogeneity in the brain, creating a more uniform balance of oxygen supply and consumption.
Sinha
A K
AK
Department of Physiology/Biophysics, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854-5635.
Chi
O Z
OZ
Weiss
H R
HR
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000187:drug effects; D010313:Partial Pressure; D010424:Pentobarbital / Q000494:pharmacology*; D051381:Rats
D002245:Carbon Dioxide; D010424:Pentobarbital; D010100:Oxygen