PubMed · 8909678
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W Lim, M J Hellings. 1996. Induction stand.. https://pubmed.ncbi.nlm.nih.gov/8909678/
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A 1-year-old Standardbred gelding had received xylazine hydrochloride (0.75 to 1.00 mg/kg [0.34 to 0.45 mg/lb] of body weight, IV) during 2 surgeries for debridement of a wound. The horse was given chloramphenicol (55 mg/kg [25 mg/lb], PO, q 6 h) for 5 days, and was anesthetized a third time with xylazine (0.75 mg/kg, IM). Five hours after administration of xylazine, the horse remained markedly sedated and had clinical signs of gaseous distention of the large bowel (bloat) requiring trocharization. Administration of yohimbine (0.03 mg/kg [0.01 mg/lb], i.v.) eliminated signs of sedation within 5 minutes. Moderate flatulence developed, and gastrointestinal sounds could be heard within all 4 abdominal quadrants within 15 minutes of yohimbine administration. The remainder of recovery was unremarkable. Xylazine induces bradycardia and decreases gastrointestinal motility in addition to causing sedation, muscle relaxation, and analgesia. Chloramphenicol can inhibit oxidase activity of cytochrome P-450 and inhibit metabolism and elimination of drugs such as xylazine.
The cardiovascular and pulmonary effects of tiletamine/zolazepam, propofol and tiletamine/zolazepam plus propofol were studied in five mongrel dogs. A cannula inserted into a raised carotid artery was used to measure mean arterial pressure (MAP) and heart rate continuously and to collect arterial blood for the determination of pH, PO2, PCO2, bicarbonate and base balance. Respiratory frequency and rectal temperature were also recorded. In the two propofol groups premedication had no significant effect on the time to rejection of an endotracheal tube and the return to sternal recumbency. The MAP and heart rate increased after tiletamine/zolazepam alone and after tiletamine/zolazepam plus propofol, although propofol alone reduced MAP and transiently increased heart rate. Respiratory frequency decreased transiently in both propofol groups in association with a significant increase in PaCO2 and decrease in PaO2. The most notable change was the hypoxaemia in the tiletamine/zolazepam plus propofol group in which the PaO2 was reduced. In all the dogs given tiletamine/zolazepam alone undesirable side effects were observed, effects which also occurred during the recovery of the dogs given tiletamine/zolazepam plus propofol.
Although single or multiple bursts of ischemic preconditioning have been shown to protect against myocardial necrosis, the frequency-dependency of the protection afforded by multiple stimuli has not yet been systematically studied in the anesthetized animal. The aim of the present study was to characterize the effect of increasing numbers of preconditioning stimuli (5 min ischemia plus 10 min reperfusion) in a collateral-deficient species in vivo. Rabbits were anesthetized and divided into groups (n = 5-7/group) which were subjected to 0, 1, 2, 4, 6 or 8 cycles of preconditioning (each comprising 5 min of regional ischemia plus 10 min reperfusion) followed by 45 min of regional ischemia and 2 h reperfusion. An additional group, serving as a control, was subjected to eight cycles of preconditioning without a subsequent 45 min of regional ischemia. Infarct size (I) and risk zones (R) were delineated with the aid of tetrazolium staining and fluorescent particles and the I/R ratio was expressed as a percentage. Mean infarct size in the control group which had no preconditioning was 59.8 +/- 4.0%. This was reduced to 22.2 +/- 2.9%, 19.5 +/- 4.1% and 23.3 +/- 3.4% by one, two and four cycles of preconditioning. However, when the number of preconditioning cycles was increased to six or eight protection declined with infarct sizes of 41.8 +/- 6.9% (P < 0.05 v zero preconditioning control group) and 47.1 +/- 7.6% (N.S. v zero preconditioning control group). In the group subjected to eight cycles of preconditioning without subsequent ischemia, infarction was not detected. In conclusion, in the anesthetized rabbit, beyond 4 cycles, protection against infarction diminishes with increasing numbers of preconditioning cycles.