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Biomedical subjects

B A Hitt

Publications and source records attributed to B A Hitt.

24 records · Page 2Linked to original sources
PubMedDate not supplied

A comparison of renal effects and metabolism of sevoflurane and methoxyflurane in enzyme-induced rats.

Twenty-five 5-month-old male Fischer-344 rats were randomly divided into 5 groups: Group I, no anesthesia; Group II, 1.4 precent sevoflurane for 2 hours; Group III, 0.1 percent phenobarbital, ad lib, in drinking water for 7 days; followed by 1.4 percent sevoflurane for 2 hours; Group IV, 0.25 percent methoxyflurane, 1 hour; Group V, phenobarbital in water as in Group III, followed by methoxyflurane as in group IV. Pre- and postanesthetic serum and urinary osmolality, Na+, K+, urea nitrogen (BUN), inorganic fluoride (F-) levels, and 24-hour urine volume were measured. Kidney tissue was obtained for examination by light and electron microscopy. Sevoflurane was metabolized to F- to a lesser extent than was methoxyflurane; treatment with phenobarbital-sevoflurane doubled urinary F- excretion, resulting in a value similar to that seen after methoxyflurane alone. There was no functional or morphologic evidence of renal abnormalities in either group of rats anesthetized with sevoflurane. Methoxyflurane dosage was sufficiently low that renal abnormalities did not occur except in rats treated also with phenobarbital; these animals developed polyuria and the morphologic lesion typically associated with F--induced nephrotoxicity.

Anesthetics↗
PubMedDate not supplied

Thermoregulatory defect in rats during anesthesia.

Male rats of the Fischer 344, Sprague-Dawley, Brattleboro, and Wistar strains, balb/C mice, and Hartley guinea pigs were divided into 2 treatment groups. One group drank tap water while the other group drank water containing 1 mg/ml of phenobarbital. Animals were exposed to sevoflurane, enflurane, methoxyflurane, isoflurane, or halothane in a closed chamber. In some of the experiments, soda lime was included and in other the chamber was heated to 39 degrees C with a water blanket. Eighty-six percent (43/50) of Fischer 344 rats treated with phenobarbital and esposed to either sevoflurane or enflurane, in the presence of either soda lime or exogenous heat, died within a few hours after exposure. Fischer 344 rats and rats of other strains drinking phenobarbital water and exposed to methoxyflurane were affected, but to a lesser degree. Rats drinking ordinary tap water and phenobarbital-treated rats not exposed to either soda lime or exogenous heat were unaffected. Guinea pigs and mice also were unaffected. We postulate that the toxic response represents a species-specific thermoregulatory defect, precipitated by heat and occurring in rats treated with phenobarbital in combination with sevoflurane, endlurane, or methoxyflurane.

Anesthesia, General↗
PubMedDate not supplied

Enflurane and methoxyflurane metabolism at anesthetic and at subanesthetic concentrations.

In an attempt to determine the importance of concentration of an anesthetic agent as a determinant of the extent of its biotransformation, we measured fluoride excretion in groups of Fischer 344 rats treated with one of several subanesthetic or an anesthetic concentration (1 MAC) of either enflurane or methoxyflurane. Anesthetic administrations (2.0% enflurane or 0.26% methoxyflurane) ranged from 0.15 hours (9 minutes) to 4.8 hours. Subanesthetic exposures, all of 48 hours duration, ranged in concentration from 0.2% enflurane to 0.0016% methoxyflurane. Greatest metabolism occurred at the lowest concentration time (MAC-hours) of subanesthetic administrations and at the shortest duration of anesthetic exposure. Increasing time in the case of anesthetizing exposures, or concentration in subanesthetic exposures, increased the amount of metabolite produced. However, the increased production of metabolite was not proportional to the increase of concentration or duration of exposure. Enzyme induction was ruled out as an important factor in the larger amount of metabolism seen during the subanesthetic exposures. Therefore, the exposure of a patient to the metabolites of an anesthetic is actually low although the anesthetic is administered at a high concentration.

Anesthesia, Inhalation↗