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Biomedical subjects

J E Wynands

Publications and source records attributed to J E Wynands.

At least 19 recordsLinked to original sources
PubMed1995

The management of temperature during cardiopulmonary bypass: effect on neuropsychological outcome.

Laboratory studies demonstrate that mild degrees of brain cooling (2 degrees C to 5 degrees C) confer substantial protection from ischemic brain injury, and that mild elevation of brain temperature can be markedly deleterious. During hypothermic cardiopulmonary bypass (CPB) patients are made hypothermic and then rewarmed at a time when they are exposed to neurological insults. Our studies show that during rewarming, peak brain temperatures near 39 degrees C often are achieved inadvertently. We hypothesize that maintaining brain temperature < or = 34 degrees C during and after CPB will reduce the incidence of postoperative neuropsychological deficits. We present safety data from a study of 30 patients assigned either to conventional hypothermic CPB with rewarming or a protocol where brain temperature is raised only to 34 degrees C at the time of separation from CPB. There was no difference in bleeding, cardiac morbidity, or time to extubation between groups. We designed a neuropsychological test battery to detect postoperative neuropsychological deficits and tested its usefulness in a preliminary sample of 15 patients undergoing hypothermic CPB. We found patient acceptability and compliance were good. Sensitivity also seemed adequate in that 30% of patients were identified as having deteriorated at 1 week postoperatively compared to preoperatively, a result similar to that reported by others. Clinical trials of the efficacy of mild hypothermia in modulating brain injury in humans are needed before techniques of CPB can be designed to optimize neuroprotection.

Aged↗
PubMed1995

Effects of routine premedication for cardiac catheterization on sedation, level of anxiety and arterial oxygen saturation.

OBJECTIVE: To assess the efficacy and side effects of routine premedication in patients undergoing cardiac catheterization procedures in a tertiary cardiac care institute. The criteria used included: arterial hemoglobin oxygen saturation (%SaO2), level of sedation and level of anxiety before and after the procedure. Overall patient satisfaction was also quantified. DESIGN: Sixty-two adult patients scheduled for cardiac catheterization procedures were recruited for the study. They were premedicated with one of several premedication regimens: oral diazepam 5 to 10 mg; oral lorazepam 1 mg; oral diazepam 10 mg+oral promethazine 25 mg; or oral diazepam 10 mg+oral diphenhydramine 25 mg. No attempt was made to control the premedication the patients received; it was ordered by each patient's cardiologist according to personal preference. Patients underwent pulse oximetry and evaluation of sedation, anxiety and level of satisfaction before and after cardiac catheterization. RESULTS: All patients tested had values for mean precatheterization %SaO2 above 92%. No patient had postcatheterization %SaO2 readings below that defined as indicating clinically significant hypoxemia (%SaO2 less than 90%). Patients were awake or lightly sedated before and after cardiac catheterization. Thirteen per cent of patients suffered from high levels of anxiety before, and 16% during, cardiac catheterization. Twenty-three per cent of patients reported being dissatisfied with the premedication before, and 10% of patients reported being dissatisfied during, cardiac catheterization. CONCLUSIONS: Clinically significant hypoxemia and oversedation are not problems for most patients given the types and doses of precatheterization medication used in the study population. The premedication schedules followed in the study failed to provide satisfaction and anxiolysis in a significant number of those studied.

Aged↗
PubMed1994

Pancuronium or vecuronium for treatment of shivering after cardiac surgery.

This randomized double-blind study compared the hemodynamic and metabolic effects of pancuronium and vecuronium during treatment of shivering after cardiac surgery with hypothermic cardiopulmonary bypass. Thirty sedated and pain-free patients who shivered after cardiac surgery were treated with pancuronium (n = 15) or vecuronium (n = 15) 0.08 mg/kg. Baseline values of heart rate (HR), mean arterial pressure, arterial and venous blood gases, total body oxygen consumption indexed to body surface area (VO2-I), and pressure work index (PWI, an estimate of myocardial oxygen consumption) were measured on arrival in the intensive care unit, at onset of shivering, and repeatedly for 2 h after treatment. Continuous ST segment analysis of leads II and V5 were used for detection of myocardial ischemia. Treatment of shivering with pancuronium decreased VO2-I by 32% (P = 0.0001). This was accompanied by a 14% increase in HR (P = 0.001) and a 10% increase in PWI (P = 0.03). Vecuronium decreased VO2-I by 36% (P = 0.003) with a 4% decrease in HR (P = 0.04) and a 6% decrease in PWI (P = 0.06). Myocardial ischemia (n = 3) and ventricular arrhythmias (n = 3) occurred in five patients treated with pancuronium. Only one patient treated with vecuronium had ventricular arrhythmia (P = 0.08). Seven patients treated with pancuronium and eight treated with vecuronium were taking beta-adrenergic blockers preoperatively which was associated with lower HR (96 +/- 16 vs 109 +/- 15 bpm; P = 0.025) and lower PWI (8.8 +/- 1.2 vs 10.7 +/- 1.92 mL.min-1 x 100 g-1; P = 0.003) at onset of shivering. However, beta-adrenergic blockers did not attenuate the relative HR increase induced by pancuronium. No relationship was found between hypercapnia and tachycardia or hypertension. These results suggest that, when compared to pancuronium for treatment of postoperative shivering, vecuronium may be advantageous because it does not increase myocardial work. The disproportionate relationship between VO2-I and PWI after treatment with muscle relaxants indicates that increased VO2-I does not contribute significantly to the hemodynamic disturbances associated with shivering. These disturbances are more likely the results of increased adrenergic activity related to pain and recovery from anesthesia. Shivering and its associated hemodynamic disturbances appear to be concomitant but independent signs of awakening.

Acid-Base Equilibrium↗
PubMed1992

Amrinone before termination of cardiopulmonary bypass: haemodynamic variables and oxygen utilization in the postbypass period.

One hundred patients were randomly allocated to receive saline or amrinone, 0.75 mg.kg-1, ten minutes before separation from cardiopulmonary bypass (CPB) after elective coronary artery bypass grafting, in order to determine the effects of this agent on haemodynamic variables and O2 utilization. Anaesthesia and CPB were managed in a standard fashion. Before induction of anaesthesia, at pericardiotomy, then at 1, 10, 20 and 30 min after CPB, haemodynamic profiles, haematocrit, and O2 saturation of arterial and mixed venous blood were measured. Incremental doses of ephedrine or phenylephrine, or an infusion of norepinephrine with phentolamine were administered when required. The groups were demographically similar and surgical variables were also similar. Haemodynamic measurements were similar between groups at all times; however, a higher dose of phenylephrine was given immediately before weaning from CPB in the amrinone group, and more patients in this group received phenylephrine in the first 30 min after CPB. Mixed venous saturation (SvO2) was higher in the amrinone patients at all times after CPB, leading to lower calculated oxygen consumption (VO2) (P less than 0.05). Insufficient dosage may explain the lack of haemodynamic effect, while possible reasons for the higher SvO2 and lower VO2 are either reduced whole body VO2 or peripheral shunting.

Amrinone↗
PubMed1992

Amrinone and dobutamine as primary treatment of low cardiac output syndrome following coronary artery surgery: a comparison of their effects on hemodynamics and outcome.

This study was undertaken in order to compare the effectiveness of amrinone and dobutamine as primary treatment of a low cardiac output (CO) after coronary artery bypass graft (CABG) surgery. Thirty patients with preoperative left ventricular dysfunction participated in this open-label randomized study. Patients were included if they failed to separate from cardiopulmonary bypass (CPB) without inotropic support or if they had a cardiac index (CI) less than 2.4 L/min/m2 after CPB regardless of the blood pressure, in the presence of adequate filling pressures. The treatment objectives were to separate from CPB and achieve a CI > or = 2.4 L/min/m2 and a mean arterial pressure > or = 70 mmHg. Patients treated with amrinone received 0.75 mg/kg followed by 10 micrograms/kg/min; when the objectives were not achieved within five minutes, another 0.75 mg/kg was given. Patients treated with dobutamine received an initial infusion of 5 micrograms/kg/min increased stepwise to 15 micrograms/kg/min if necessary. Eleven of 15 amrinone versus 6 of 15 dobutamine patients achieved the predefined treatment objectives with the test drug alone (P = NS). Comparisons of hemodynamics in patients treated solely with amrinone (n = 7) or dobutamine (n = 6) after CPB showed no significant differences between the treatment groups. The incidence of myocardial ischemia as detected by Holter monitor was 36% with amrinone and 33% with dobutamine. Two patients suffered ventricular fibrillation and two had significant supraventricular tachyarrhythmias (heart rate > 130/min) during treatment with dobutamine alone, whereas no significant arrhythmias occurred in the amrinone group (P = NS). Six dobutamine patients (40%) had postoperative myocardial infarction (MI) as opposed to none among the amrinone patients (P = 0.017). These results indicate that amrinone compares favorably with dobutamine as a primary treatment of low CO after CABG. Further study in a larger number of patients will be required in order to determine if the lower incidence of MI in the amrinone group was due to the treatment drug.

Amrinone↗
PubMed1991

Clinical application of cardiac risk indices: how to avoid misleading numbers.

Perioperative cardiac complications are associated with a high mortality rate. During the preoperative assessment the anaesthetist must determine if the patient is at risk so that appropriate interventions can be made to ensure the best possible outcome. Over the past three decades several indices have been proposed to identify the surgical patient at risk of cardiac morbidity or mortality. These indices can be thought of as diagnostic tests which determine the likelihood of perioperative cardiac complication. In this article the authors review the epidemiological basis of diagnostic tests and apply this theory to three currently available indices of perioperative risk: the American Society of Anesthesiologists physical status classification, the Goldman multifactorial cardiac risk index and a modified version devised by Detsky. A case history describing a surgical patient with unstable angina is first presented to show how different indices can lead to different predictions. These indices are then analysed as if they were diagnostic tests to predict cardiac complications after surgery. The characteristics of diagnostic tests such as sensitivity, specificity, positive and negative predictive values, and receiver operating characteristic curves are described and applied to the indices. Basic principles such as odds ratio, likelihood ratio and their relation to prevalence and post-test probability are also presented. This overview will help the anaesthetist to understand the limitations of risk indices as predictors of adverse cardiac outcome and to apply these scales more effectively to individual patients at different institutions.

Anesthesia↗
PubMed1991

Bolus administration of esmolol for controlling the haemodynamic response to tracheal intubation: the Canadian Multicentre Trial.

A multicentre trial was designed to determine the dose-response and side-effects of esmolol when administered as a single iv bolus prior to induction of anaesthesia for controlling the haemodynamic response to tracheal intubation. Five hundred and forty-eight patients from 12 university-affiliated centres across Canada were randomized prospectively to receive either placebo (PLAC) or esmolol (E) in a dose of 100 mg (E100) or 200 mg (E200). Study medication was given immediately before induction of anaesthesia with thiopentone 3-5 mg.kg-1 and succinylcholine 1.5 mg.kg-1. Low-dose narcotic (fentanyl 2-3 micrograms.kg-1 or sufentanil 0.3 micrograms.kg-1) or moderate dose narcotic (fentanyl 4-7 micrograms.kg-1) was also given at five of the participating centres, whereas patients in the remaining seven centres received no narcotic. Patients who received PLAC and no narcotic had greater HR and SBP values after tracheal intubation than patients who received either E100 or E200 (P less than 0.005). The proportion of patients whose maximum HR exceeded 110 min-1 was also greater in the PLAC group (22/180) than in either the E100 (10/187) or E200 (9/181) groups (P less than 0.05), but was not different when comparing E100 with E200. Esmolol was less effective in controlling blood pressure, but, in combination with low-dose narcotic, esmolol suppressed the SBP response to tracheal intubation. In the presence of moderate-dose narcotic, however, a decrease in SBP occurred in all three groups following induction of anaesthesia (P less than 0.003), with the largest decrease (17 +/- 4%) occurring in patients who had received E200. The overall incidence of hypotension (SBP less than 90 mmHg) was greater in the E200 group (33%) than either the E100 (25%) or PLAC (16%) groups (P less than 0.05). Other side-effects, such as bradycardia, bronchospasm or pain on injection, occurred no more frequently in either esmolol group than with placebo. It is concluded that a 100 mg bolus of esmolol is safe and effective for controlling the haemodynamic response to tracheal intubation. This dose of esmolol combined with a low dose of narcotic (fentanyl 2-3 micrograms.kg-1 or equivalent) results in effective control of both heart rate and blood pressure, while avoiding important side-effects.

Adrenergic beta-Antagonists↗
PubMed1990

Pharmacokinetics of alfentanil and clinical responses during cardiac surgery.

This study assessed the pharmacokinetic and pharmacodynamic behaviour of alfentanil during and after coronary artery bypass grafting (CABG). Twenty-eight patients with good ventricular function having CABG were divided into three groups and premedicated with morphine 0.1 mg.kg-1 IM, scopolamine 0.005 mg.kg-1 IM and diazepam 0.1 mg.kg-1 PO. Group I patients received an infusion of 250 micrograms.kg-1 of alfentanil over one hour coincidental with a second infusion at 2.5 micrograms.kg-1.min-1 which was continued to the end of surgery. Patients in group II received 300 micrograms.kg-1 and 3.0 micrograms.kg-1.min-1 and patients in group III 350 micrograms.kg-1 and 3.5 micrograms.kg-1.min-1. The tracheas of all patients were intubated after receiving alfentanil 96 micrograms.kg-1 and pancuronium 0.15 micrograms.kg-1. Haemodynamic responses to intubation and surgical stimuli (greater than or equal to 20 per cent increase in heart rate and/or systolic blood pressure from control) were treated with isoflurane, one to two per cent inspired, until abolished. Blood samples were taken during and after surgery for plasma alfentanil concentrations which were determined by radioimmunoassay. After surgery the times to awakening and extubation, and alfentanil elimination half-life (t1/2B = 0.693/-k) were determined for each patient. Haemodynamic responses occurred in 20 patients. There were no significant differences in any variable among the groups. The times to awakening and extubation for all patients were 3.2 +/- 0.6 and 8.8 +/- 1.2 hr (mean +/- SEM) respectively. The elimination half-life for all patients was 5.1 +/- 1.0 hr (mean +/- SEM).(ABSTRACT TRUNCATED AT 250 WORDS)

Alfentanil↗
PubMed1989

Amrinone: is it the inotrope of choice?

In the treatment of acute heart failure, conventional therapy with epinephrine, norepinephrine, dopamine, and dobutamine may be used effectively to treat inotropic abnormalities. However, the addition of a vasodilator to catecholamine therapy may be needed to help improve lusitropic function. Because it seems to exert positive inotropic and lusitropic effects, the phosphodiesterase inhibitor amrinone may be a valuable addition to the anesthesiologist's armamentarium for the treatment of acute heart failure. When used as adjunctive therapy with catecholamines, amrinone has been shown to exert a significant additive and synergistic effect. Amrinone may also be the inotrope of choice in patients who are refractory to therapy with conventional inotropes, due to its positive inotropic and lusitropic effects, combined with its vasodilating effects. Because of its broad pharmacodynamic spectrum, amrinone may effectively control all of the major elements involved in myocardial performance--preload, afterload, contractility, and heart rate.

Amrinone↗
PubMed1989

The incidence of myocardial ischemia during anesthesia for coronary artery bypass surgery in patients receiving pancuronium or vecuronium.

This study was performed to compare the incidence of prebypass myocardial ischemia in patients receiving fentanyl and enflurane for anesthesia along with either pancuronium or vecuronium. Ninety-eight patients with normal left ventricular function were randomly allocated to receive either pancuronium 0.15 mg.kg-1 or vecuronium 0.15 mg.kg-1 in a double-blind manner after fentanyl 40 micrograms.kg-1 for induction of anesthesia for elective coronary artery bypass grafting (CABG). Premedication included diazepam 0.15 mg.kg-1 po, morphine 0.10 mg.kg-1, and scopolamine 0.005 mg.kg-1 im. Two lead Holter monitor recordings (leads V6 and V9) from the time of arrival in the operating suite to institution of cardiopulmonary bypass were analyzed for ischemia by a cardiologist blinded to the choice of muscle relaxant. Intraoperatively, heart rates greater than 90 beats.min-1 and systolic blood pressure +/- 20% of ward values were treated with propranolol, enflurane, or phenylephrine. Nitroglycerin was infused for ECG signs of ischemia or pulmonary hypertension. After induction of anesthesia the heart rate and cardiac index were consistently decreased in patients receiving vecuronium and also lower in these patients compared with those receiving pancuronium. Thirty-two per cent of patients receiving pancuronium received propranolol for heart rates greater than 90 beats.min-1 versus 7% of those who received vecuronium (P approximately 0.01). Eight patients developed 13 episodes of ischemia after administration of the muscle relaxant: four who received pancuronium (n = 44; 9%) and four receiving vecuronium (n = 54; 7%). Four episodes occurred at induction or tracheal intubation, two in each group. There were four perioperative myocardial infarctions as determined by ECG and CPK-MB levels, two in each group.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1988

The effects of shivering on oxygen consumption and carbon dioxide production in patients rewarming from hypothermic cardiopulmonary bypass.

Oxygen consumption (VO2), carbon dioxide production (VCO2), end-tidal carbon dioxide partial pressure (PETCO2), mixed venous oxygen saturation (SvO2) and haemodynamic variables were recorded every 30 min for four hours in 15 patients recovering from hypothermic cardiopulmonary bypass (CPB). All patients had been anaesthetised with fentanyl 40 micrograms.kg-1, supplemented with isoflurane, and pancuronium 0.15 mg.kg-1 for muscle relaxation. Three of the 15 patients (20 per cent) shivered, defined as intermittent or continuous, vigorous movements of chest or limb muscles. Patients who shivered had a VO2 of 159 +/- 16.4 ml.min-1.m-2 on arrival in the ICU which rose to a maximum value of 254 +/- 28.3 ml.min-1.m-2 by 150 min post-CPB. In contrast, patients who did not shiver had a significantly lower VO2 of 93.1 +/- 6.9 ml.min-1.m-2 on arrival in the ICU which rose to a maximal value of only 168 +/- 11.5 ml.min-1.m-2 by 180 min post-CPB. Maximal VO2 in both groups was reached when the nasopharyngeal temperature (NPT) was approaching normal. VCO2 paralleled the increase in VO2 in both groups. By four hours there was no significant difference between the two groups; however, the VO2 in both groups (160.5 +/- 21.3 ml.min-1.m-2 and 173.9 +/- 12.3 ml.min-1.m-2 respectively) was approximately twice values commonly measured in anaesthetized patients. Patients who shivered had a significantly higher heart rate and cardiac index and significantly lower SvO2. We conclude that the high VO2 and VCO2 associated with shivering causing increased myocardial work may be detrimental to patients who have impaired cardiac function post-coronary artery surgery (CAS).

Aged↗
PubMed1987

The relationship between central venous pressure and pulmonary capillary wedge pressure during aortic surgery.

Twenty-three ASA physical status II-III patients scheduled for elective abdominal aortic surgery were studied preoperatively with multiple unit gated acquisition angiography (MUGA) scan to determine the resting left ventricular and right ventricular ejection fractions (LVEF and RVEF respectively). Intraoperatively pulmonary capillary wedge pressure (PCWP) and central venous pressure (CVP) were measured in each patient at five different time periods in the horizontal, 24 degrees head up, and 24 degrees head down table tilt positions. The correlation between absolute values and changes in PCWP and CVP, and the degree to which preoperative knowledge of LVEF and RVEF predicted these correlations were examined. Resting LVEF ranged from 0.1 to 0.84. Thirteen of the 23 patients failed to show significant correlation (p less than 0.05) between the absolute values of PCWP and CVP either before and/or after aortic crossclamp. When the correlation coefficients from this analysis were ranked against LVEF, there was a weak but significant correlation before aortic crossclamp (r = 0.41), but not after. The correlation between a change in PCWP and a change in CVP was significant for the 23 patients at all time intervals, before and after aortic crossclamp. However, the prediction of a change of PCWP value from a known change of CVP value ranged in accuracy from +/- 3 mmHg to +/- 12.5 mmHg. The study suggests that if the filling pressures of both ventricles need to be assessed during aortic surgery, then the PCWP and CVP must be independently measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

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Anesthesiology↗
PubMed1987

Hemodynamic variables and the incidence of prebypass ischemia during sufentanil/O2/pancuronium anesthesia in patients undergoing coronary artery surgery.

It has been suggested that sufentanil is a superior anesthetic to fentanyl for patients undergoing myocardial revascularization. This study was performed to determine the incidence of prebypass myocardial ischemia using sufentanil, 20 micrograms/kg for patients undergoing coronary artery bypass grafting (CABG). Twenty-seven patients with normal left ventricular function, scheduled for elective CABG, were studied. Anesthesia was induced with sufentanil, 10 micrograms/kg; and pancuronium, 0.1 mg/kg, was given for muscle relaxation. Further increments of sufentanil, 5 micrograms/kg, were given before skin incision and sternotomy. All patients had ECG leads V6 and V9 recorded continuously with a Holter monitor from arrival in the operating room until the start of bypass. Hemodynamic profiles were recorded at specific intervals in the prebypass period. Seven patients (25.9%) developed prebypass myocardial ischemia, three at intubation, and three at aortic dissection. Fourteen patients developed hypertension and 14 had hypotension, defined as increases or decreases greater than 20% from baseline values, respectively. Only five patients had neither hypotension nor hypertension. Three patients (11.1%) had perioperative myocardial infarctions, two of whom had prebypass myocardial ischemia. It is concluded that the incidence of prebypass ischemia with sufentanil anesthesia approximates 26%, which is similar to other studies using sensitive ECG monitoring techniques for the detection of ST segment changes. Hemodynamic instability, in the form of bradycardia, hypertension and hypotension, but not tachycardia, may have contributed to the incidence of prebypass ischemia.

Aged↗