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Biomedical subjects

M C Clapham

Publications and source records attributed to M C Clapham.

11 recordsLinked to original sources
PubMed1991

Flumazenil in intensive care. The duration of arousal after an assessment dose.

The effect of an assessment dose of the benzodiazepine antagonist flumazenil was studied in 20 patients in an intensive care unit. The patients had been sedated with alfentanil and midazolam, and were ready to be weaned from mechanical ventilation. In 10 patients flumazenil was titrated just to produce full arousal whilst the midazolam infusion was continued; flumazenil administration was repeated one hour later after the infusion of midazolam had been stopped. In another 10 patients, flumazenil was administered only once, coinciding with the cessation of sedation. The duration of full arousal in both groups was less than 15 minutes in 75% of patients given a single dose of flumazenil (median dose 0.4 mg) although some effect persisted for up to 60 minutes. The cardiovascular effects of arousal were transient and probably not clinically significant. A brief duration of action is advantageous if the patient is found still to require sedation.

Adult↗
PubMed1991

Assessment of oxygenation in the critically ill.

This paper reviews the physiology and pathology of oxygen transport from the atmosphere to the cells in critically ill patients. A thorough understanding of this allows a rational approach to monitoring and managing an hypoxic patient in the intensive care setting.

Biological Transport↗
PubMed1989

Therapeutic progress in intensive care--rational use of vasoactive and inotropic drugs in the intensive care unit.

Vasoactive (vasodilating and vasoconstricting) and inotropic drugs are widely used in intensive therapy. Major progress in their use in recent years has been due to a greater understanding of the physiological derangements of the critically ill. This progress is the consequence of improved standards of haemodynamic monitoring in the intensive therapy unit (ITU). In addition the introduction of accurate and reliable syringe pumps, to administer small volumes of fluid accurately, has enabled the easy use of drugs to manipulate physiological parameters. An understanding of the basic anatomy and physiology of the cardiovascular system (CVS) is essential to an understanding of the methods used for monitoring and measurement (1). Logical therapeutic interventions follow from consideration of these measured and derived parameters.

Cardiotonic Agents↗
PubMed1987

Minimum volume of discard for valid blood sampling from indwelling arterial cannulae.

The volume of discard for valid blood sampling from indwelling femoral (leader cath) and radial (Venflon) arterial cannulae (with internal volume of cannula plus connecting tubing of approximately 2 ml) was investigated by analysing sequential 2-ml aliquots of 10-ml samples. The aliquots were analysed for pH, carbon dioxide tension, oxygen tension, standard bicarbonate, haemoglobin concentration, haemoglobin oxygen saturation and potassium concentration. Analysis of variance showed that, for these variables and these catheters, a valid blood sample was obtained after discarding 4 ml, but not after only 2 ml. The haemoglobin concentration, as measured by a Corning oximeter, provided good warning of inadequate discard.

Analysis of Variance↗
PubMed1987

Additional blood-gas variables for the rational control of oxygen therapy. With allowance for shifts of the oxygen dissociation curve.

When a sample of arterial blood is analysed for oxygen tension and, using a modern oximeter, for haemoglobin concentration and saturation, it is possible to calculate the position of the oxygen dissociation curve and two new variables: "P95" and "C(a-x)O2". P95 is the tension at which the haemoglobin would be 95% saturated and can, therefore, constitute a target tension for near-maximum arterial content of oxygen. C(a-x)O2 (the "conditional extraction" of oxygen) is the amount of oxygen, in ml/dl blood, which can be extracted from the arterial blood for a hypothetical mixed-venous oxygen tension PxO2. It is explained how it is possible to estimate the adequacy of tissue oxygenation by comparing any available estimate of the required extraction (normally about 5 ml dl-1) with conditional extractions calculated for three hypothetical values of PxO2 covering the clinical range. Methods of calculation are given. For accurate results at high arterial saturations, a peripheral venous sample may be required in addition to the arterial sample.

Cardiac Output↗
PubMed1986

Pulse oximetry. An assessment in anaesthetised dental patients.

The applications of a pulse oximeter were studied in dental day case surgery using nasal mask anaesthesia. Changes in arterial oxygen saturation were sensitively and rapidly detected, in the absence of cyanosis. Impaired oxygenation can be detected before cyanosis develops.

Adolescent↗
PubMed1983

Cricothyroidotomy.

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Airway Obstruction↗