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Biomedical subjects

A Coetzee

Publications and source records attributed to A Coetzee.

At least 19 recordsLinked to original sources
PubMed1997

Nitric oxide has little effect on acute pulmonary hypertension and right ventricular function during acute respiratory distress syndrome.

OBJECTIVE: To evaluate the effect of nitric oxide (NO) on acute pulmonary hypertension and right ventricular function in patients with acute respiratory distress syndrome. DESIGN: A prospective clinical study. PATIENTS: Ten patients in the respiratory and surgical intensive care units were used. They met the criteria for acute respiratory distress syndrome and were significantly hypoxic. They were all ventilator-dependent at the time of the study. INTERVENTION: NO was delivered to the patients in 5, 10, 20 and 30 ppm doses for 30 minutes at each concentration. The dosing was not randomised. MEASUREMENTS AND RESULTS: The general and central haemodynamics were measured. Right ventricular function and interaction with the pulmonary artery impedance (Ea) were quantified with the ratio of right ventricular stroke work index/Ea. NO did not decrease the raised pulmonary artery pressure found in all of the patients. Right ventricular coupling to the circulation did not improve during the administration of NO. CONCLUSION: NO did not relieve the acute pulmonary artery hypertension associated with acute respiratory distress syndrome. As a consequence of this, right ventricular function failed to improve during the administration of NO.

Acute Disease↗
PubMed1996

Failure of allopurinol to improve left ventricular stroke work after cardiopulmonary bypass surgery.

OBJECTIVE: This study examined the effects of allopurinol on global left ventricular function after coronary artery bypass surgery. DESIGN: A randomized prospective partially blinded study in 52 patients undergoing elective coronary artery bypass surgery. SETTING: Conducted in a university-affiliated tertiary care facility. INTERVENTIONS: Participants received 400 mg of allopurinol 18 hours and 400 mg of allopurinol orally 3 hours before surgery or no allopurinol. Patients then received a standard anesthetic technique consisting of target-controlled opiate infusion and inhalation anesthesia. Coronary artery bypass was performed using moderate hypothermia and oxygenated crystalloid cardioplegia. MEASUREMENTS AND MAIN RESULTS: Global left ventricular function was assessed by means of left ventricular stroke work index (LVSWI) calculated before and after induction of anesthesia and after cardiopulmonary bypass at 15 minutes, 6, 12 and 24 hours. There was no difference in the LVSWI before or after surgery when the two groups were compared. CONCLUSIONS: In this population sample, the use of preoperative allopurinol did not result in improved left ventricular stroke work after coronary artery bypass surgery.

Adult↗
PubMed1996

Comparison of the effects of propofol and halothane on acute myocardial ischaemia and myocardial reperfusion injury.

The effects of two blood concentrations of propofol on acute severe regional myocardial ischaemia (15-minute occlusion of the LAD coronary artery) and 2-hour reperfusion were studied in 10 pigs. Results were contrasted with the effect of 0.8% halothane (N = 5). Results indicate that during acute ischaemia, regional myocardial function of the segment supplied by the LAD artery was not protected against the effects of ischaemia in the propofol or halothane groups. During reperfusion, animals subjected to halothane demonstrated significantly fewer reperfusion arrhythmias and segmental function was less stunned than in either propofol group. There was no difference in heart performance between the propofol groups. Results indicate that the proposed anti-oxidant effect of propofol is not sufficient to protect the animal heart from reperfusion injury.

Anesthetics, Inhalation↗
PubMed1996

Acute pulmonary hypertension and right ventricular failure in adult respiratory distress syndrome.

The severity of acute pulmonary hypertension (APHT) in acute respiratory distress syndrome was examined in 20 patients. All patients had significant APHT (mean pressure 40.6 +/- 6.3 mmHg) on admission to the intensive care unit. There was evidence of right ventricular (RV) failure, with a right ventricular stroke work index (RVSWI) of 9.20 +/- 3.3 g.m/m2 and a central venous pressure of 18.0 +/- 4.0 mmHg. The RV afterload, i.e. pulmonary artery elastance (Ea = stroke volume/peak pulmonary artery pressure), was raised. Stroke volume could not be predicted from Ea or RVSWI alone, but regression analysis indicated that the ratio of RVSWI/Ea (i.e. ventriculo-arterial coupling) could account for 88% of the stroke volume.

Adolescent↗
PubMed1995

Comparison of sodium nitroprusside- and esmolol-induced controlled hypotension for functional endoscopic sinus surgery.

The purpose of this study was to compare surgical conditions for functional endoscopic sinus surgery (FESS) under general anaesthesia during controlled induced hypotension, using either sodium nitroprusside (SNP) or esmolol. Twenty patients, assigned to receive either of the drugs as the primary hypotensive agent, were studied. The same surgeon, blinded to the hypotensive agent used and the haemodynamic variables, performed all the operations. The surgeon used a category scale (0-5) to assess surgical conditions--a value of 2-3 being ideal. Patients were positioned in 5 degrees reverse Trendelenburg position and the mean arterial blood pressure (MABP) was reduced in steps of 5 mmHg. The anaesthetist prompted category scale estimations by the surgeon following a change in any of the haemodynamic variables. Average category scale (ACS) values were compared between the two groups for four data groups, i.e., MABP > 65 mmHg (mild), 60-64 mmHg, 55-59 mmHg and 50-54 mmHg. Pre-treatment MABP was 79.8 +/- 10.4 mmHg in the SNP group and 76.1 +/- 6.8 mmHg in the esmolol group. At mild SNP-induced hypotension, surgical conditions were poor (ACS = 3.63 +/- 0.22; mean +/- SEM), while in the esmolol group, ideal surgical conditions (ACS = 2.94 +/- 0.34) were recorded at MABP > 65 mmHg. The combined effects of increased venous drainage due to the reverse Trendelenburg position, hypotension as well as capillary vasoconstriction due to unopposed alpha-adrenergic effect on the mucous membrane vasculature in the esmolol group (as opposed to vasodilatation in the SNP group) probably caused the superior surgical conditions.

Adrenergic beta-Antagonists↗
PubMed1995

Gas exchange indices--how valid are they?

OBJECTIVE: This study examined the arterial-alveolar oxygen tension difference (AaDO2), arterial oxygen tension to inspired oxygen fraction ratio (PaO2/FiO2) and alveolar to arterial oxygen tension ratio (PAO2/PaO2) with regard to: (i) their correlation with the calculated pulmonary shunt in critically ill patients; and (ii) the influence of the inspired oxygen fraction on these indices before, during and after general anaesthesia. DESIGN: This study comprised two sections: (i) retrospective analyses of blood gas data retrieved from the intensive care computerised database; and (ii) analyses of arterial blood gases before, during and after abdominal and orthopaedic surgery in patients subjected to various inspired fractions of oxygen. SETTING: The study was conducted at an academic hospital. PATIENTS: The first section of the study was a retrospective analysis of blood gases retrieved from a computerised database from the surgical and respiratory intensive care units. Blood gases which indicated hypoxaemia (arterial haemoglobin saturation less than 90%) were collected from patients who suffered from adult respiratory distress syndrome. The calculated pulmonary shunt was correlated with the AaDO2, PaO2/FiO2 and PAO2/PaO2. In the second section of this study, 15 patients of American Society of Anesthesiologists status 1, scheduled to undergo peripheral orthopaedic and intra-abdominal surgery, were exposed to various concentrations of inspired oxygen before, during and after general anaesthesia. At the end of a 15-minute period of exposure to a particular level of inspired oxygen (which was varied at random), arterial blood gases were analysed. A correlation was attempted between the inspired oxygen fraction and the various indices of pulmonary gas exchange. INTERVENTION: Patients were subjected to the various inspired fractions of oxygen before, during and after general anaesthesia. A radial artery cannula, inserted under local anaesthesia, allowed the researchers to collect arterial blood gas analysis. RESULTS: The correlation between the calculated pulmonary shunt and indices of gas exchange showed r = 0.35 for the AaDO2, r = 0.08 for the PaO2/FiO2 and r = 0.40 for the PAO2/PaO2. Stepwise variable selection demonstrated that the FiO2, PaCO2, PAO2 and shunt were the main components of the final models. The inspired oxygen fraction had an effect on the indices of gas exchange inasmuch as they all varied directly with the change in inspired oxygen concentration. Furthermore, the slope of this relationship was less steep during anaesthesia than in the case of values obtained before and after anaesthesia. CONCLUSIONS: The so-called non-invasive indices of pulmonary gas exchange do not correlate well with the calculated pulmonary shunt, which is regarded as the gold standard that reflects the various components of gas exchange. We speculate that the poor performance of these indices can be explained by the fact that they do not take into account the mixed venous saturation and, except for the alveolar to arterial oxygen tension ratio, ignore the effects of alveolar ventilation. The effect of the inspired oxygen fraction on these ratios makes them difficult to interpret if similar inspired oxygen fractions are not used. The effect of the FiO2 on these indices could possibly be explained by the denitrogenation and collapse of alveoli with low ventilation perfusion ratios. The change in the slope of the FiO2 and the indices that was demonstrated during anaesthesia could possibly be explained by the expected change in the mixed venous saturation that occurs during anaesthesia.

Adult↗
PubMed1993

Effects of beta-blockers and Ca(2+)-antagonists on the response of the isolated working rat heart to adrenergic stimulants after cardioplegic arrest.

During coronary artery bypass graft (CABG) surgery, patients pretreated with the combination of beta-blocking drugs and Ca2+ antagonists for control of myocardial ischemia often respond inadequately to adrenergic stimulants administered after cardioplegic arrest. In this study, the effects of the combination of a beta-blocker (propranolol) and a Ca2+ antagonist (nifedipine) on the spontaneous recovery, as well as the adrenergic response of the isolated, perfused, working rat heart after a period of cardioplegic arrest were evaluated. After pretreatment of the animals with propranolol and/or nifedipine, hearts were removed, perfused in the presence of pretreatment drugs, subjected to 45 minutes of normothermic cardioplegic arrest, reperfused, and finally stimulated with exponentially increasing concentrations of a sympathomimetic drug. Propranolol, and to a lesser extent nifedipine, protected the hearts during cardioplegic arrest, as indicated by the improved recovery and maximum response to adrenergic stimulation after cardioplegia. Isoprenaline, a beta-stimulant, (at a 100 x higher than conventional concentration), elicited an adequate inotropic and chronotropic response. Stimulation by the alpha, beta-stimulant adrenaline or dobutamine improved only the inotropic response of propranolol and combination treated hearts. Cautious extrapolation of the results to human may suggest continuation of drug therapy of patients before CABG surgery.

Adenine Nucleotides↗
PubMed1993

Enflurane and isoflurane reduce reperfusion dysfunction in the isolated rat heart.

We evaluated the possible cardioprotective effects of enflurane (E) and isoflurane (I) in isolated rat hearts subjected to 40 min normothermic arrest. After reperfusion, hearts were stimulated with adrenaline to evaluate their systolic reserves. In hearts not receiving I or E, adenosine triphosphate (ATP) was reduced from 23.0 +/- 0.8 to 9.3 +/- 1.1 mumol/g dry weight (means +/- SEM; P < 0.001) after arrest. This was associated with a significant reduction in ventricular work (Wt) from 13.6 +/- 0.7 to 1.6 +/- 0.7 mW (P < 0.001). Adrenaline partially restored Wt but not the ATP. E and I given only during normothermic arrest (in the cardioplegic solution) resulted in reductions in ATP similar to the hearts not receiving the drugs. However, on reperfusion and subsequent administration of adrenaline, hearts subjected to the anesthetic drugs performed as well as hearts before arrest. For example, in hearts not exposed to I or E, the Wt after the elective arrest was 1.55 +/- 0.05% (mean +/- SEM) of the pre-arrest value. This was significantly less than hearts exposed to either one of the inhalational agents (40.02 +/- 3.49% of the pre-arrest value; P < 0.0001). Adrenaline improved function in hearts which did not receive I or E to 55.02 +/- 12.80% of the pre-arrest value, but this was significantly less than the Wt performed by the hearts exposed to the anesthetic agents (122.67 +/- 7.78% of pre-arrest value; P < 0.001). This beneficial effect of I and E during reperfusion probably is mediated by the effect of the anesthetic agents on Ca2+ slow channels. The effect could not be ascribed to depression of global myocardial contractile function associated with I and E.

Adenosine Triphosphate↗
PubMed1993

Halothane and the reperfusion injury in the intact animal model.

We studied the effect of halothane on regional myocardial function during acute ischemia and reperfusion in an open-chest pig model. Anesthesia was induced with thiopental and fentanyl and maintained with an intravenous (IV) infusion of pentobarbital and fentanyl. Regional myocardial function was studied with microsonometers placed in the subendocardium supplied by the left anterior descending coronary (LAD) and circumflex coronary artery (LX). Systolic function was evaluated with reference to the end-systolic pressure-length relationship (ESPLR) and regional systolic shortening. Diastolic dysfunction was studied with postsystolic shortening (PSS). Ischemia was induced with 15 min of total occlusion of the LAD artery, and thereafter reperfusion was allowed for 120 min. Five groups were studied: one group received only pentobarbital and fentanyl (n = 10); the other groups received halothane 0.2% (n = 5), 0.4% (n = 7), 0.6% (n = 5), and 0.8% (n = 5). The pentobarbital and fentanyl infusion was adjusted in the halothane groups in an effort to maintain arterial blood pressure and heart rate within specified limits (when possible). Results indicate that regional dysfunction during acute ischemia was equal among all the groups. However, on reperfusion, halothane significantly reduced the incidence of ventricular arrhythmias. Halothane (0.6% and 0.8%) was associated with less regional postischemic systolic dysfunction during reperfusion when compared to the other groups. Hearts subjected to 0.6% and 0.8% halothane also were less stiff at the end of systole (i.e., the extrapolated ventricular volume at zero ventricular pressure was less) after 120 min reperfusion compared to animals receiving less halothane. However, diastolic dysfunction was equal among the groups during reperfusion. We conclude that, in this model, administration of halothane is associated with improved recovery of regional systolic function and potentially beneficial pressure-length relations at the end of systole after acute severe myocardial ischemia and reperfusion. Furthermore, administration of halothane was associated with fewer reperfusion arrhythmias compared to animals not receiving halothane.

Animals↗
PubMed1992

The effects of sevoflurane, halothane, enflurane, and isoflurane on hepatic blood flow and oxygenation in chronically instrumented greyhound dogs.

Inhalational anesthetics produce differential effects on hepatic blood flow and oxygenation that may impact hepatocellular function and drug clearance. In this investigation, the effects of sevoflurane on hepatic blood flow and oxygenation were compared with those of enflurane, halothane, and isoflurane in ten chronically instrumented greyhound dogs. Each dog randomly received enflurane, halothane, isoflurane, and sevoflurane, each at 1.0, 1.5, and 2.0 MAC concentrations. Mean arterial blood pressure and cardiac output decreased in a dose-dependent fashion during all four anesthetics studied. Heart rate increased compared to control during enflurane, isoflurane, and sevoflurane anesthesia and did not change during halothane anesthesia. Hepatic arterial blood flow and portal venous blood flow were measured by chronically implanted electromagnetic flow probes. Hepatic O2 delivery and consumption were calculated after hepatic arterial, portal venous, and hepatic venous blood gas analysis. Hepatic arterial blood flow was maintained with sevoflurane and isoflurane. Halothane and enflurane reduced hepatic arterial blood flow during all anesthetic levels compared to control (P less than 0.05), with marked reductions occurring with 1.5 and 2.0 MAC halothane concomitant with an increase in hepatic arterial vascular resistance. Portal venous blood flow was reduced with isoflurane and sevoflurane at 1.5 and 2.0 MAC. A somewhat greater reduction in portal venous blood flow occurred during 2.0 MAC sevoflurane (P less than 0.05 compared to control and 1.0 MAC values for sevoflurane). Enflurane reduced portal venous blood flow at 1.0, 1.5, and 2.0 MAC compared to control. Halothane produced the greatest reduction in portal venous blood flow (P less than 0.05 compared to sevoflurane).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetics↗
PubMed1992

Acute colloid administration increases ischemia in the myocardium supplied by a stenotic coronary artery.

The effect of acute colloid administration was evaluated in the pig heart in which an external coronary artery stenosis was applied. Seven pigs received thiopentone and halothane anesthesia. Ultrasonic crystals were inserted in the myocardium supplied by the left anterior descending (LAD) and circumflex coronary arteries. Left ventricular pressure was measured and regional myocardial function was quantified with the pressure-length loop and the end-systolic pressure-length ratio. A significant stenosis was applied to the LAD artery, after which the animal received fixed colloids to increase the left ventricular end-diastolic pressure. Regional myocardial ischemia was defined with reference to postsystolic shortening and lactate production from the region supplied by the LAD artery. The application of the stenosis caused an increase in postsystolic shortening from 9.62% +/- 4.24% to 26.12% +/- 5.81% (mean +/- SEM; P less than 0.05), and lactate extraction changed from 15.88% +/- 2.38% to -9.56% +/- 5.32% (P less than 0.05). Acute colloid administration increased the left ventricular end-diastolic pressure from 9.71 +/- 1.77 to 15.93 +/- 2.07 mm Hg (P less than 0.05), and lactate extraction further decreased to -76.63% +/- 19.19% (P less than 0.05). Postsystolic shortening increased to 36.22% +/- 5.10% (P less than 0.05). The oxygen tension in the venous blood draining the LAD region decreased from 36.74 +/- 9.37 to 17.34 +/- 1.23 mm Hg (P less than 0.05). We conclude that in the acute pig model, augmentation of the preload worsens regional myocardial ischemia in an area supplied by a stenotic coronary artery.

Animals↗
PubMed1992

Peri-operative mortality in the anaesthetic service at Tygerberg Hospital.

This study reports on the process of peer review of peri-operative mortality at Tygerberg Hospital. The peri-operative mortality rate for the past 3.5 years was 11.9/10,000. The departmental evaluation committee thought that 3.4/10,000 of these deaths were anaesthetic-related. In 2.3/10,000, the anaesthetic contributed to the death of the patient and in 10 cases (total case load = 94,945; i.e. 1.1/10,000) anaesthesia was responsible for the death of the patient. The majority of the peri-operative deaths (8.5/10,000) were caused by a combination of trauma and haemorrhagic shock.

Anesthesia↗
PubMed1991

Oxygenation of cardioplegic solutions: a note of caution.

The merits of oxygenated crystalloid cardioplegic solutions have been well established in experimental animals. The positive effects of oxygenation of Plasmalyte B (Sabax Ltd) and St. Thomas Hospital solution (Plegisol) were achieved by gassing with 95% O2/5% CO2 and 100% O2, respectively. In view of the marked pH differences induced by these gas mixtures, we evaluated the effect of mode of oxygenation on myocardial recovery during reperfusion after hypothermic cardioplegic arrest. Oxygenation with 100% O2 of Plasmalyte B containing high K+ levels caused marked deterioration in myocardial recovery, whereas the mode of oxygenation did not affect recovery after arrest with St. Thomas Hospital solution. Because the major differences between these solutions reside in their respective K+, Mg2+, and HCO3- contents, the effects of variations in the levels of these ions were investigated. The results showed that oxygenation with 100% O2 was deleterious only in the presence of high K+ (29 mmol/L), low Mg2+ (3 mmol/L), and high NaHCO3 (28 mmol/L) levels. The marked decline in mechanical recovery during reperfusion was associated with significant changes in myocardial adenosine triphosphate and intracellular Ca2+ levels. Although an explanation for these findings is not readily available, it is suggested that complex ionic interactions and possibly oxygen free radical generation may lead to intracellular Ca2+ overload, depression in mitochondrial adenosine triphosphate generation, and, hence, deterioration in mechanical recovery.

Acid-Base Equilibrium↗
PubMed1991

Postsystolic shortening as an index of regional myocardial ischemia in an experimental model.

This study explored the relationship between regional myocardial postsystolic shortening (PSS) and myocardial tissue oxygenation in an open-chested animal model subjected to halothane anesthesia. Regional function was examined with reference to the ventricular pressure-length loop and tissue oxygenation gauged from regional arterial-venous lactate dynamics. Coronary blood flow was decreased in steps by application of an external constriction to the left anterior descending coronary artery. Results indicate that a significant change in PSS (from 7.46% +/- 2.14%, mean +/- SEM to 17.74% +/- 3.31%; P less than 0.00001) was associated with a reduction in coronary blood flow from 81.48 +/- 8.85 to 56.94 +/- 7.12 mL/min/100 g tissue (P less than 0.0012), but lactate extraction across the myocardium did not change (10.54% +/- 3.20% to 12.17% +/- 2.43%). A further reduction in coronary blood flow to 39.84 +/- 5.63 mL/min/100 g resulted in severe PSS (50.62% +/- 6.14%) and lactate production (183.81% +/- 28.80%). The correlation between PSS and lactate production was significant (r = 0.873; SEE = 50.49; P = 0.000001).

Animals↗