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Biomedical subjects

A Coetzee

Publications and source records attributed to A Coetzee.

47 records · Page 3Linked to original sources
PubMed1985

Coronary blood flow during variation in coronary perfusion pressure.

It is demonstrated that severe dysfunction occurs in the myocardial segment supplied by a critically stenosed coronary artery during hypotension, while in contrast an increase in coronary perfusion pressure (to the extent used in this experimental model) is not detrimental to regional myocardial function. If the results of these experiments are applied to clinical practice, it appears to be of primary importance to maintain normal blood pressure in patients with ischaemic heart disease, and it may even be preferable to increase the blood pressure slightly during the peri-operative period.

Animals↗
PubMed1985

Filling pressures of the heart during anaesthesia.

The validity of extrapolating central venous pressure (CVP) to left ventricular (LV) filling pressure as gauged from the pulmonary artery wedge pressure (PAWP) was investigated in 9 subjects undergoing lung resection. Correlations existed between CVP and PAWP before, during and after surgery, and between changes in CVP and PAWP during surgery. There was, however, a wide scattering of the data around the regression lines, and an inability of the CVP and changes therein to predict the actual and directional change in PAWP in specific individuals. Caution is therefore advised in assessing the LV filling pressure from the CVP in patients undergoing lung resection during any phase of the peri-operative period.

Anesthesia↗
PubMed1985

Myocardial ischaemia during tachycardia--not due to an increase in myocardial oxygen demand.

It is generally believed that an increase in heart rate will be accompanied by an increase in myocardial oxygen demand (MVO2), but in a recent publication this concept has been challenged; we present data supporting the view that an increase in heart rate is not necessarily accompanied by an increase in MVO2. Our data are based on studies on dogs in five phases: (a) normal coronary arteries; (i) with normal heart rate; (ii) with tachycardia induced by a pacemaker; and (iii) with normal heart rate; and (b) with a constricted left anterior descending coronary artery: (i) with normal heart rate; and (ii) with induced tachycardia. MVO2 remained unchanged both per beat and per unit of time. Neither global nor regional myocardial function in the area supplied by the constricted artery changed during tachycardia. The reason for myocardial ischaemia should therefore not be attributed to an increase in MVO2 if the diameter of the heart is not increased, and attention should rather be focused on inadequate diastolic perfusion time and possible redistribution of blood from the potentially ischaemic zone.

Animals↗
PubMed1984

[Ischaemic heart disease as a risk factor for general anaesthesia and surgery].

The risk of myocardial reinfarction in the patient who has suffered a pre-operative infarction is well documented. In a literature search, the cardiovascular risk implied by either asymptomatic or symptomatic ischaemic heart disease (without infarction) to the patient scheduled for anaesthesia and surgery appears to be minimal provided that hypotension, hypoxia, tachyarrythmias and hypertension are avoided. However, a myocardial ischaemic incident prior to surgery seems to warrant the postponement of elective surgical procedures.

Anesthesia, General↗
PubMed1984

Effect of hypoxia on the normal and ischemic myocardium.

This study investigated the effect of hypoxia on global and regional myocardial function in the normal heart and in the heart with a critically constricted coronary artery. Eight dogs under halothane anesthesia were subjected to progressive degrees of hypoxia while global and segmental heart function as well as general hemodynamics were evaluated. In the control phase of the experiment, the coronary circulation was undisturbed. A decrease in the inspired oxygen fraction from 0.3 to 0.1 was associated with significant increases in the heart rate, cardiac output, left ventricular minute work and coronary blood flow, and significant decreases in systemic vascular resistance. regional myocardial function (measured by endocardial fiber shortening) did not change. In dogs with a critical constriction applied to the left anterior descending coronary artery (LAD), hypoxia significantly increased heart rate and decreased stroke volume. Indices of global myocardial function did not change, but regional function in the area supplied by constricted LAD was depressed during severe hypoxia. This study implies that measured indices of global heart function bear little relation to regional function when a compromised segment of the myocardium is subjected to hypoxia.

Animals↗
PubMed1984

The effect of hypocapnia on coronary blood flow and myocardial function in the dog.

The effect of hypocapnia on global and regional myocardial function and coronary blood flow (CBF) was studied in dogs anesthetized with halothane before and after critical constriction of the left anterior descending (LAD) coronary artery. Coronary blood flow decreased 29% (P less than 0.05) when hypocapnia was induced in dogs with a normal LAD artery. Critical constriction reduced CBF by 42% (P less than 0.05). In the critically constricted LAD artery, hypocapnia did not reduce CBF. During hypocapnia and with a normal LAD artery, oxygen extraction by the myocardium increased 16% (P less than 0.01) and oxygen tension in the coronary sinus was reduced by 19% (P less than 0.001). After critical constriction of the LAD, hypocapnia was associated with an increase in oxygen extraction of 14% (P less than 0.01) and the coronary sinus oxygen tension was reduced by 21% (P less than 0.001). CBF of the left circumflex coronary artery (LC) increased 36% (P less than 0.05) after critical constriction to the LAD when compared with control values of the preconstriction phase. However, LC flow did not change during hypocapnia when critical stenosis had been applied to the LAD artery. Although oxygen supply (product of CBF and arterial oxygen content) to the myocardium was reduced during hypocapnia, regional myocardial function did not change from control values. Regional function was similarly maintained during hypocapnia and critical constriction of the LAD.

Anesthesia, General↗