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Biomedical subjects

F W Gamache

Publications and source records attributed to F W Gamache.

23 records · Page 2Linked to original sources
PubMed1976

Changes in local cerebral blood flow following profound systemic hypotension.

The authors studied local cerebral blood flow in monkeys rendered hypotensive by infusion of a ganglionic blocking agent. Application of the 14C-antipyrine method demonstrated that the blood flow: 1) normally varies reproducibly from one structure to another within the brain; 2) appears at its lowest level in all structures during the early minutes of a rapid-onset hypotension; 3) maintains the same general rank order of blood flow rate during hypotension as was present during normotension; and 4) returns to supranormal levels immediately following the rapid restoration of blood pressure. The values for local cerebral blood flow remain close-to-normal in some animals and diminish significantly in others during late recovery from hypotension. The close-to-normal values accompany uncomplicated recoveries while the diminished values appear in those animals which became neurologically depressed. Areas of the brain considered predisposed to hypotensive injury did not exhibit depressions in blood flow rate during hypotension more markedly than did other brain areas. The present results are interpreted as strong evidence against the "border zone" hypothesis.

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PubMed1975

Effects of hypotension on rhesus monkeys.

Twenty-one late-juvenile rhesus monkeys were rendered profoundly hypotensive for 0-, 15-, or 30-minute periods by means of infusion of trimethaphan camsylate. Blood pressure was then restored to prehypotensive levels with phenylephrine infusions. Respiratory gas tensions and pH of arterial blood were maintained within their normal limits throughout experimental and recovery periods. Animals either recovered and showed no sequelae or diet 12 to 48 hours later of cardiorespiratory difficulties, often accompanied by brain swelling. Brain injury and death occurred in 64% of cases when arterial blood pressure was maintained at 25 mm Hg for up to 30 minutes. Multifocal myoclonus, depressed electroencephalographic activity, rises in cisternal cerebrospinal (CSF) pressure, respiratory depression, and characteristic changes in serum and cisternal CSF glucose followed episodes of controlled hypotension. Hypoxia and acidosis occurring during insult or recovery periods rather than hypotension itself probably account for neuropathological sequelae described by others.

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PubMed1975

Alterations in cerebral blood flow produced by hypotension: a comparison of methods.

Alterations in cerebral blood flow produced by controlled episodes of hypotension were studied in 12 juvenile monkeys using a thermocouple techique. The qualitative changes observed agreed closely with those obtained from an earlier study employing [14C]antipyrine autoradiographic methods. The present study extends the validity of the earlier antipyrine investigations by means of the continuous recording. The advantages and disadvantages of the thermocouple technique are examined.

Animals↗
PubMed1975

Changes in cortical impedance and EEG activity induced by profound hypotension.

Fourteen late juvenile monkeys were subjected to a single 30-min episodes of markedhypotension using an infusion of trimethaphan. Afterward, blood pressure was rapidly restored to and maintained at preinsult levels with an intravenous drip of phenylephrine (.02 mg/ml). The respiratory gas tensions and pH of the arterial blood weremaintained within normal limits at all times. During the 30-min episodes, the cortical electrical impedence increased by a mean of 27% while the EEG frequencies and amplitudes decreased by 47 and 30%, respectively. The impedance and EEG activity generally altered at the same time but inversely to one another, although, on restoration of blood pressure, the impedance recovered within minutes while the EEG activity returned to normal only after 1 h. The impedance values and EEG activity of those animals that eventually died began to diverge significantly from the values of theanimals that were to survive at about 2.5 h after restoration of blood pressure.

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