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Biomedical subjects

R L Knill

Publications and source records attributed to R L Knill.

46 records · Page 3Linked to original sources
PubMed1980

Surgical stimulation does not enhance ventilatory chemoreflexes during enflurane anaesthesia in man.

To assess the impact of surgical stimulation on regulation of ventilation in anaesthetized man, we measured ventilation and the ventilatory responses to either hyperoxic hypercapnia or to isocapnic hypoxaemia in fifteen subjects anaesthetized with enflurane 1.1 MAC, just prior to and then during a surgical procedure. Anaesthesia alone reduced ventilation, increased PaCO2, decreased the response to carbon dioxide and virtually abolished the response to hypoxaemia. The addition of operation at the same level of anaesthesia augmented ventilation and reduced PaCO2, but did not improve the anaesthesia-induced impairment of the responses to hypercarbia and hypoxaemia. Over the range of PCO2 and PO2 values studied, the effects of surgery were constant and independent of chemical drive.

Adult↗
PubMed1980

An evaluation of gas density dependence of anaesthetic vaporizers.

Four commonly used vaporizers were studied for the effect of carrier gas density on vaporizer output. Vapour concentrations from a halothane Cyprane (Fluotec) Mark 2 increased in relation to the density of carrier gas, whereas the concentrations delivered by an enflurane Ohio vaporizer decreased. The halothane Cyprane (Fluotec) Mark 3 and enflurane Cyprane vaporizers were largely independent of density. Of clinical importance, nitrous oxide/oxygen (75/25), compared with oxygen alone, increased the vapour concentration outputs of the halothane Mark 2 up to 30% and decreased the outputs of the enflurane Ohio unit up to 20%.

Anesthesia, Inhalation↗
PubMed1979

Cardiovascular signs of acute hypoxaemia and hypercarbia during enflurane and halothane anaesthesia in man.

We investigated the impact of enflurane and halothane (1.1 MAC) on heart rate and blood pressure responses to experimental hypoxaemia (PETo2 6.0 kPa [45 torr]) and small increments in PCO2 (1.3--1.6 KPa [10--12 torr]). The results reaffirm that circulatory signs of mild hypercarbia are vitually abolished by these anaesthetics. The important new observation is that signs of acute moderate hypoxaemia are also markedly depressed. Although potential modifying factors such as surgical stimulation were not evaluated, this study indicates that human subjects anaesthetized with enflurane or halothane lack reliable cardiovascular signs of acute hypoxaemia.

Adult↗
PubMed1979

Ventilation and chemoreflexes during enflurane sedation and anaesthesia in man.

Enflurane sedation and anaesthesia in healthy fit subjects reduced ventilation and the response to carbon dioxide, hypoxaemia and a low dose of doxapram, all in a dose-related fashion. Comparing the three chemoreflexes tested, the response to hypoxaemia and doxapram were the more profoundly impaired; they were nearly totally abolished by anaesthesia. These effects of enflurane on chemoreflex activities are qualitatively similar to those previously observed with halothane.

Adolescent↗
PubMed1978

Hypoxic ventilatory responses during thiopentone sedation and anaesthesia in man.

We have assessed the impact of thiopentone on the hypoxic ventilatory reflex, and on the responses to carbon dioxide and doxapram. Thiopentone sedation did not detectably alter any of these aspects of ventilatory control. Thiopentone anaesthesia reduced ventilation and the ventilatory responses to hypoxia, carbon dioxide and doxapram, all approximately in paralle. We conclude that, in contrast to halothane, thiopentone does not selectively reduce the ventilatory response to hypoxia. During light thiopentone anaesthesia, a reasonably brisk hypoxic response is present.

Adolescent↗
PubMed1978

Subanaesthetic halothane: its effect on regulation of ventilation and relevance to the recovery room.

Ventilation and the ventilatory response to a steady-state of isocapnic hypoxaemia were measured in six healthy volunteers, both awake and while sedated with low doses of halothane (0.05 and 0.1 MAC). Halothane sedation markedly reduced ventilatory responses to sustained hypoxaemia, in a dose-related fashion. We estimated the length of time after anaesthesia that halothane 0.1 MAC would be present in patients in the recovery room. In five healthy patients who had halothane anaesthesia with a mean duration of one hour, halothane 0.1 MAC or more persisted for approximately one hour. We conclude that, during emergence from halothane anaesthesia, patients may have a significant impairment of the ventilatory response to hypoxaemia, which persists for some time even after regaining consciousness.

Adult↗
PubMed1978

Ventilatory responses to hypoxia and hypercapnia during halothane sedation and anesthesia in man.

To elucidate the effects of halothane on chemical regulation of ventilation in man, the authors studied the ventilatory responses to isocapnic hypoxia and hyperoxic hypercapnia in 33 human subjects while fully conscious and during sedation or anesthesia with halothane, .1, 1.1, or 2 MAC. In each group, the ventilatory effect of intravenous administration of doxapram, .4 mg/kg, was also measured. Halothane, 1.1 and 2 MAC, totally abolished the hypoxic response and nearly abolished the response to doxapram, while leaving the response to CO2 relatively brisk. Halothane, .1 MAC, decreased the responses to hypoxia and doxapram to less than a third of control, but did not alter the response to CO2. It is concluded that halothane selectivity impairs two ventilatory responses mediated by peripheral chemoreceptors in man.

Adult↗
PubMed1975

Pathogenesis of gangrene following intra-arterial injection of drugs: a new hypothesis.

We have demonstrated the toxicity of diazepam and the safety of ketamine hydrochloride following intra-arterial injection in an anaesthetized animal model. The pathogenesis of gangrene following intra-arterial injection of drugs is unclear. Clinical reports and this experiment suggest that it only follows injection of highly membrane-soluble drugs. Early swelling and disruption of capillary endothelial cells were demonstrated after intra-arterial injection of diazepam and thiopentone. We believe that a theory of pathogenesis based on this finding is consistent not only with our experimental findings, but with known in vitro effects of membrane soluble drugs on cell membranes and the clinical features following intra-arterial injections in both human subjects and in animals.

Animals↗