Cerebral, renal, adrenal, intestinal, and pancreatic circulation in conscious ponies and during 1.0, 1.5, and 2.0 minimal alveolar concentrations of halothane-O2 anesthesia.
Abstract: Blood flow to the brain, kidneys, adrenal glands, pancreas, and small intestine was studied in 8 healthy ponies while awake (control) and during 1.0, 1.5, and 2.0 minimal alveolar concentrations (MAC) of anesthesia produced, using halothane vaporized in oxygen. During the anesthesia steps, intermittent positive-pressure ventilation was used to ensure isocapnia. Organ blood flow was determined with 15-micron (diameter) radionuclide-labeled microspheres, after allowing 30 minutes of equilibration at each of the 3 preestablished end-tidal halothane concentrations. The sequence of 1.0, 1.5, and 2.0 MAC levels of anesthesia (0.90, 1.35, and 1.80% end-tidal halothane) was randomized for every animal. In the awake ponies, cerebral blood flow in the cortical (106 +/- 15 ml/min/100 g) and deep gray (103 +/- 12 ml/min/100 g) matter was approximately 5-fold of that in the white matter (22 +/- 3 ml/min/100 g). In the brain stem, there was a decreasing gradient of blood flow from the cranial (thalamohypothalamus: 65 +/- 8 ml/min/100 g) to caudal regions (medulla: 34 +/- 5 ml/min/100 g). Vasodilatation occurred in all regions of the brain with halothane-O2 anesthesia; the decrease in vascular resistance reached its nadir at 1.5 MAC. In the medulla and pons, blood flow increased above control values, with each of the 3 concentrations of halothane, but in the midbrain and thalamohypothalamus, it remained similar to the control value. In the cerebral white matter and cerebellum, blood flow increased with 1.0 and 1.5 MAC of halothane anesthesia, whereas mean aortic pressure decreased to 91% and 74% of the control value. Blood flow in the cerebral cortex was not different from the control value, even at 2.0 MAC of halothane, despite a 49% reduction in perfusion pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1985-12-01 PubMed ID: 4083581
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study examines how blood flow to the brain and other organs in conscious horses is affected during varying levels of anesthesia. It demonstrates that there is an increase in blood flow to all areas of the brain, and other organs under anesthesia, despite a decrease in blood pressure.
Research Methodology
- The research involved studying blood flow to the brain, kidneys, adrenal glands, pancreas, and small intestine in 8 healthy horses.
- These were analyzed while awake and during three different levels of anesthesia (1.0, 1.5, and 2.0 minimal alveolar concentrations, or MAC).
- The anesthesia used was halothane, vaporized in oxygen.
- Each of the three anesthesia levels was randomly assigned to the animals to avoid any sequence effect.
- Blood flow in the organs was determined using radionuclide-labeled microspheres, which allowed for precise measurements.
Results and Analysis
- The findings showed a significant increase in blood flow in all areas of the brain under anesthesia, despite lower blood pressure.
- In the cerebral cortices, blood flow was about five times greater than in the white matter when the horses were conscious.
- There was also a decrease in vascular resistance in all brain regions under anesthesia, reaching its lowest at 1.5 MAC.
- The findings revealed that despite experiencing a 49% drop in perfusion pressure, the blood flow in the cerebral cortex maintained a consistent rate even at 2.0 MAC of halothane.
- These findings raise questions about how anesthesia affects the body’s mechanisms to control blood flow and response to blood pressure drops.
Conclusion
- The study concludes that there is an increase in blood flow to the brain and other organs despite lower blood pressure under anesthesia.
- The impact of anesthesia on regulation of blood flow and blood pressure response continues to be an area of interest.
- Further research is needed to fully understand the mechanisms at work and the implications for patient care during anesthesia.
Cite This Article
APA
Manohar M, Goetz TE.
(1985).
Cerebral, renal, adrenal, intestinal, and pancreatic circulation in conscious ponies and during 1.0, 1.5, and 2.0 minimal alveolar concentrations of halothane-O2 anesthesia.
Am J Vet Res, 46(12), 2492-2497.
Publication
Researcher Affiliations
MeSH Terms
- Adrenal Glands / blood supply
- Anesthesia / adverse effects
- Anesthesia / veterinary
- Animals
- Cerebrovascular Circulation / drug effects
- Female
- Halothane / adverse effects
- Hemodynamics / drug effects
- Horses / physiology
- Intestines / blood supply
- Male
- Pancreas / blood supply
- Regional Blood Flow / drug effects
- Renal Circulation / drug effects
- Vasoconstriction / drug effects
- Vasodilation / drug effects
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