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Biomedical subjects

J E Wynands

Publications and source records attributed to J E Wynands.

At least 55 records · Page 3Linked to original sources
PubMed1984

Role of renin-angiotensin system in cardiopulmonary bypass hypertension.

The role of the renin-angiotensin system in the aetiology of perioperative hypertension was studied in 15 previously normotensive patients undergoing coronary artery surgery and anaesthetized with fentanyl. Measurements of plasma renin activity were made at intervals before and during cardiopulmonary bypass (CPB). In addition, angiotensin II blockade with saralasin was used in an attempt to treat hypertension during CPB. Nine of the patients became hypertensive (increase in systemic pressure of more than 20 per cent) before CPB and although the mean plasma renin activity was higher in this group than in the normotensive patients it was within normal limits for each group. Hypertension during CPB (mean blood pressure greater than 100 mmHg at 1.8 l X m-2 flow), occurred in seven patients but was not associated with increased renin activity and did not respond to saralasin in doses up to 20 micrograms X kg-1 X min-1. It is concluded that cardiopulmonary bypass associated hypertension is not mediated by activation of the renin-angiotensin system.

Angiotensin II↗
PubMed1984

Effect of heated humidified gases on temperature drop after cardiopulmonary bypass.

In an attempt to prevent the decrease in nasopharyngeal temperature (NPT) ("afterdrop") after cardiac surgery, 30 patients undergoing hypothermic cardiopulmonary bypass (CPB) were randomly assigned to receive humidified heated inspired gases at 45 degrees C at the proximal end of the endotracheal tube (group I) or dry gases at room temperature (group II), from the time of termination of CPB. All patients received high flow rates on CPB during the rewarming period with the use of vasodilator drugs when necessary. Both groups were comparable with respect to total bypass time, rewarming time, and temperature at termination of CPB. In addition, the NPT was compared with the tympanic membrane temperature (TMT) in group I to assess the validity of the NPT under these conditions. The results indicate that heating and humidifying inspired gases do not prevent afterdrop and do not falsely increase the nasopharyngeal temperature. The reasons for the ineffectiveness of heated humidified gases may include a large heat deficit at termination of CPB despite a normal NPT, and the very small heat content of heated gases. Monitoring the temperature of a site that reflects the heat deficit, and a more complete rewarming during CPB are suggested as a better approach to the prevention of afterdrop.

Adult↗
PubMed1984

Narcotic requirements for intravenous anesthesia.

MAC BAR, the minimum end-tidal alveolar anesthetic concentration that inhibits adrenergic response to a noxious stimulus in 50% of subjects, is a quantifiable physiological parameter that can be used to determine potency and therapeutic indices of volatile anesthetics. We wished to determine whether there is a minimal intraarterial plasma concentration (MIC BAR) of an opiate such as fentanyl that will prevent a hypertensive response to noxious stimuli in 50% of patients undergoing aortocoronary bypass surgery (ACBP). Forty-three patients with good left ventricular function were studied. All patients were premedicated with diazepam, morphine, and scopolamine. Five groups of patients were anesthetized with different fentanyl anesthesia protocols, each designed to produce different plasma fentanyl concentrations (PFC). A 20% increase in systolic blood pressure compared to control was considered an adrenergic response that related to the plasma fentanyl concentration inferred from each patient's PFC time-concentration curve. Only four patients became hypertensive with a PFC greater than 20 ng/ml. One patient became hypertensive at intubation with a PFC of 12.3 ng/ml. There was no statistically significant difference in the mean PFC in patients who became hypertensive at each event. During aortic dissection, when significantly more patients became hypertensive, there was no difference in the incidence of hypertension in patients with a PFC above or below 20 ng/ml. Two patients became hypertensive at skin incision with a PFC over 30 ng/ml. A MIC BAR could not be identified because of the great variability in the PFC of patients who became hypertensive.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Intravenous↗
PubMed1983

A profile of intravenous nitroglycerin use in cardiopulmonary bypass surgery.

We studied the indications for use, time to onset of effect, approximate effective concentration and therapeutic success of commercially prepared intravenous nitroglycerin (NTG) in 50 patients undergoing cardiopulmonary bypass (CPB) surgery. Nitroglycerin was used to treat systemic or pulmonary hypertension, myocardial ischaemia and ventricular failure. Twenty-one patients had more than one indication for NTG use. Nineteen of 22 patients with pulmonary hypertension, 12 of 13 patients with ischaemic changes, and 13 of 15 patients with ventricular failure improved during intravenous NTG administration. Hypertension during CPB was ameliorated in only six of ten instances. The time to onset of effect ranged from 4.1 +/- 0.8 to 7.8 +/- 2.8 minutes and the mean approximate effective NTG concentration varied from 1.7 +/- 0.3 to 2.9 +/- 0.7 micrograms . kg-1.min-1 (doses only approximate due to our use of an infusion system which absorbs NTG). Complications from intravenous NTG administration were not seen. We conclude that this NTG preparation facilitates treatment of prebypass hypertension, pulmonary hypertension, myocardial ischaemia and ventricular failure but is less effective for the treatment of hypertension during CPB.

Cardiac Surgical Procedures↗
PubMed1983

Electrical behavior of the heart following high-potassium cardioplegia.

The electrical activity of the heart was studied in 25 patients undergoing elective coronary artery bypass grafting. Simultaneous surface electrocardiograms and bipolar atrial electrograms were monitored continuously from the onset of cardioplegic arrest until normal sinus rhythm was reestablished. Several observations were made. (1) Administration of cardioplegia promptly induced and maintained ventricular arrest in all patients. (2) Atrial activity was seen in 23 patients during global ischemia. (3) Following unclamping, the first sustained rhythm was atrial in 22 patients and was associated initially with high-grade atrioventricular block progressing to 1:1 conduction after a mean reperfusion time of 23 minutes. (4) The time required for complete electrical recovery varied directly with the cross-clamp time and the amount of cardioplegic solution used. (5) Only 3 patients required ventricular defibrillation. (6) In the postoperative period, supraventricular tachyarrhythmias developed in 6 patients. Their occurrence appeared to be related to prolonged atrial activity during the cross-clamp period. Although cardioplegia administration maintained ventricular arrest, sustained atrial activity often was present, perhaps implying inadequate atrial protection and predisposing to atrial arrhythmias. Normal sinus rhythm was reestablished spontaneously in all patients. The atrial electrogram proved essential in the precise intraoperative recognition of cardiac rhythm.

Adult↗
PubMed1983

Persistent atrial activity during cardioplegic arrest: a possible factor in the etiology of postoperative supraventricular tachyarrhythmias.

We assessed the relationship between the duration of atrial activity during the cross-clamp period and the postoperative occurrence of supraventricular tachyarrhythmias in 50 patients undergoing elective coronary bypass operation. The atrial electrical activity was monitored continuously by means of a bipolar atrial electrogram from the onset of cardioplegic administration until removal of the aortic cross-clamp. While ventricular arrest was induced promptly and maintained in all patients, sustained atrial activity was observed in 44 out of 50 patients during the cross-clamp period. In the postoperative period, supraventricular tachyarrhythmias developed in 15 patients (Group 1). Thirty-five patients (Group 2) were free from such tachyarrhythmias. There was no significant difference between the two groups with respect to cross-clamp time, bypass time, amount of cardioplegic solution used, or number of grafts per patient. The mean duration of atrial activity during cardioplegic arrest, however, was significantly longer in Group 1 than in Group 2 (46 +/- 4.7 minutes versus 22.6 +/- 4.0 minutes, respectively, p less than 0.001). None of the 6 patients in whom atrial activity was completely abolished experienced supraventricular tachyarrhythmias. The strong correlation observed between the duration of atrial activity during cardioplegic arrest and the incidence of postoperative supraventricular tachyarrhythmias suggests the possibility that these arrhythmias may be a manifestation of inadequate atrial protection during global myocardial ischemia.

Arrhythmias, Cardiac↗
PubMed1983

Pancuronium requirements during hypothermic cardiopulmonary bypass in man.

Eight patients were studied to determine the changes in pancuronium requirements during hypothermic cardiopulmonary bypass. They were anaesthetised with fentanyl as the principal agent, ventilated with oxygen and the neuromuscular junction was monitored using train-of-four stimulation. After a bolus dose of pancuronium an infusion was used to maintain the first twitch of the train-of-four at 5-15 per cent of control. Before bypass the mean pancuronium infusion rate was 0.52 (SD 0.16) micrograms/kg/min. There was a small, brief increase in requirement with the initiation of bypass to 0.62 (SD 0.38) micrograms/kg/min, which was followed by a decrease of more than 80 per cent during hypothermia to 0.08 (SD 0.03) micrograms/kg/min. Rewarming was associated with a rapid increase in requirement to 0.64 (SD 0.17) micrograms/kg/min, which decreased to 0.33 (SD 0.23) micrograms/kg/min when normothermia was re-established.

Aged↗
PubMed1983

Blood pressure response and plasma fentanyl concentrations during high- and very high-dose fentanyl anesthesia for coronary artery surgery.

We examined whether different plasma fentanyl concentrations could maintain hemodynamic stability during coronary artery surgery. Two randomly selected groups of 10 patients were studied. Patients in group 1 received a single 75-micrograms/kg intravenous dose of fentanyl; patients in group 2 received the same dose but it was followed by an infusion of fentanyl at a rate of 0.75 micrograms/kg/min. The total dose of fentanyl in group 2 was 162 +/- 6.5 micrograms/kg (mean +/- SEM). At some point during surgery, all 10 patients in group 1 and 7 of 10 patients in group 2 had a hypertensive response. Plasma fentanyl concentrations in the two groups were not significantly different in the period 10-45 min after induction of anesthesia. At 60 min, corresponding to the time of aortic root dissection, mean plasma fentanyl concentration was statistically significantly lower in group 1 than in group 2 (13.5 +/- 1.4 ng/ml and 24 +/- 2.3 ng/ml, respectively, P less than 0.01). However, no significant difference was observed in the frequency of hypertensive response between the two groups in the period before cardiopulmonary bypass. During cardiopulmonary bypass, plasma fentanyl concentrations in group 1 were 2-3 times lower than those in group 2, and hypertension was observed in all 10 patients in group 1 but in only 2 patients in group 2 (P less than 0.05). Patients in group 1 were ventilated for 16.6 +/- 1.5 h, and those in group 2 for 19.1 +/- 1.8 h, postoperatively (P greater than 0.05). Six patients in group 1 required vasodilating drugs, whereas eight patients in group 2 required alpha-adrenergic agonists. Although the plasma fentanyl concentrations achieved were not successful in totally suppressing a hypertensive response, this study suggests that a plasma fentanyl concentration might be attainable to effect this.

Anesthesia, Intravenous↗
PubMed1982

Anaesthesia for cardiac patients having non-cardiac operations.

It is difficult to pick out a sensitive marker for the effectiveness with which patients with heart disease have been managed for non-cardiac operations. Reinfarction rates have frequently been cited for this purpose over the past 20 years and it is interesting and perplexing that, until very recently, we have been unable to show significant decreases in reinfarction rates in patients who have had a myocardial infarction within six months of surgery. It has been our opinion for a number of years that, in general, patients with heart disease are well managed in the intraoperative phase of their hospital stay. The successful management of patients during this period is based on the fact that the majority of anaesthetists now appear to have a good understanding of the pathophysiology of heart disease and are becoming more aggressive in the monitoring and treatment of abnormal haemodynamics when they occur. The ultimate extent to which morbidity and mortality can be reduced in patients with heart disease for non-cardiac surgery will not be known until patients at high risk receive the same intensive postoperative care that patients who undergo heart surgery enjoy. It is the fact that patients are haemodynamically stable and do not have myocardial ischaemia throughout the peri-operative period that is important, rather than the way in which it is achieved.

Anesthesia, General↗
PubMed1982

Fentanyl infusion anesthesia for aortocoronary bypass surgery: plasma levels and hemodynamic response.

Plasma fentanyl concentrations were measured by radioimmunoassay in patients during aortocoronary bypass surgery and correlated with hemodynamic responses to surgical stimulation. Thirty patients scheduled for aortocoronary bypass surgery were divided into three groups of 10. Patients in group 1 received fentanyl, 30 micrograms/kg, as a loading dose followed by an infusion of 0.3 microgram/kg/min; those in group 2 received 40 micrograms/kg as a loading dose followed by an infusion of 0.4 microgram/kg/min; and those in group 3 received 50 micrograms/kg as the loading dose followed by an infusion of 0.5 microgram/kg/min. The total dose of fentanyl administered to each group up to the time of rewarming on cardiopulmonary bypass was 60 micrograms/kg, 90 micrograms/kg, respectively. Each of the dose regimens produced stable plasma concentrations starting approximately 20 minutes after induction and continuing until the infusion was discontinued. Patients in group 1 had a mean plasma concentration of 10 to 12 ng/ml in the stable period compared with 12 to 14 ng/ml in group 2 and 15 to 18 ng/ml in group 3. Fewer patients in group 3 responded to intubation and surgical stimulation than in the other groups, although the differences between groups were not statistically significant. Response to stimulation was treated by the administration of droperidol or volatile anesthetic agents. At a plasma concentration of 15 ng/ml, 50% of patients had an increase in systolic blood pressure which required treatment. This minimal intra-arterial concentration, analogous to MAC, can be achieved by the administration of fentanyl as a loading dose of 50 micrograms/kg followed by an infusion of 0.5 microgram/kg/min.

Anesthesia, Intravenous↗
PubMed1982

Temporary cardiac pacing following open-heart surgery.

The type, frequency and duration of use of temporary pacemaker wires were recorded in 100 patients who underwent in 100 patients who underwent open-heart surgery. Sixty-five patients had wires implanted: 29 were atrioventricular 35 ventricular and 1 atrial. Pacing was required in 24 instances for nodal rhythm, sinus bradycardia, sinus arrest, atrioventricular block or ventricular tachycardia. Patients who required a pacemaker temporarily had a significantly (P less than 0.001) longer cross-clamping time and required a significantly (P less than 0.025) larger volume of cardioplegic agent during the operation. Two patients who did not have wires placed could have benefited from pacing. Temporary pacemaker wires should always be implanted in patients after they have undergone open-heart surgery, especially when abnormal rhythms are present, or the cross-clamping time is prolonged and when larger volumes of cardioplegic agent have been used.

Arrhythmias, Cardiac↗
PubMed1981

The effects of vascular catheterization upon heart rate and blood pressure before aorto-coronary bypass surgery.

Ten patients presenting for aorto-coronary bypass surgery were premedicated with their regular dose of propranolol and nitrates and diazepam 0.15 mg x kg-1 by mouth, morphine 0.15 mg x kg-1 and scopolamine 0.4 mg intramuscularly, 60 to 90 minutes before arrival in the operating room. Venous, arterial and pulmonary artery catheterizations were done under local anaesthesia. No significant changes were noted in systolic blood pressure and rate pressure product. Heart rate was decreased after internal jugular puncture and for the remainder of the study. PaCO2 increased and PaO2 decreased from values obtained the day before operation. Cardiovascular stability during vascular catheterization was achieved by emphasizing a detailed preoperative explanation, maintenance of beta-blockade up to the time of operation, substantial sedative premedication, and the liberal use of local anaesthesia.

Blood Pressure↗
PubMed1981

Swan-Ganz catheter contamination: a protective sleeve for repositioning.

Valuable haemodynamic data can be derived from a properly positioned Swan-Ganz catheter. Unfortunately, a significant number of these catheters will, for one reason or another, become malpositioned. Withdrawing a catheter from a permanently wedged position presents little difficulty. Repositioning may, however, necessitate its advancement, with the attendant risk of bacterial contamination. We have solved this problem by making a protective sleeve from readily available latex drain and tubing, which fits securely over the haemostatic valve of a No. 8F Cordis introducer. Iodine solution is injected into the sleeve to provide a sterile environment for the Swan-Ganz catheter, which can then be repositioned as required without the risk of bacterial contamination, as verified by bacteriological studies.

Cardiac Catheterization↗
PubMed1981

Oxygen-high dose fentanyl-droperidol anesthesia for aortocoronary bypass surgery.

Ten patients undergoing aortocoronary bupass surgery were studied during induction of anesthesia and during initial surgical stimulation. Each patient was anesthetized with fentanyl, 100 micrograms/kg, droperidol, 0.15 mg/kg, and pancuronium, 0.1 mg/kg, and ventilated with 100% oxygen. Preoperative medication consisted of propranolol, nitrate preparations, diazepam, 0.15 mg/kg orally, morphine, 0.15 mg/kg IM, and scopolamine, 0.4 mg IM. Intravenous, arterial, and Swan-Ganz catheters were inserted under local anesthesia after which control measurements of hemodynamic parameters and arterial blood gas tensions were taken. Observations were repeated after fentanyl, 50 micrograms/kg, after endotracheal intubation, after another dose of fentanyl, 50 micrograms/kg, after skin incision, and after sternotomy. The total dose of droperidol was given incrementally throughtout the fentanyl infusion. Normal saline was infused to maintain constant pulmonary capillary wedge pressure. Heart rate, left ventricular stroke work index, triple index, pulmonary capillary wedge pressure, and PaCO2 remained constant throughout the study. Systolic blood pressure decreased significantly after fentanyl, 50 micrograms/kg, and initial administration of droperidol, but thereafter remained unchanged. Stroke index increased significantly after fentanyl, 50 micrograms/kg, and remained elevated at all subsequent intervals. Cardiac index increased after fentanyl, 50 micrograms/kg and 100 micrograms/kg. Rate-pressure product was stable until the time of sternotomy after which it decreased significantly. In patients undergoing aortocoronary bypass surgery, 100% oxygen, fentanyl, 100 micrograms/kg, and droperidol, 0.15 mg/kg, produced stable hemodynamics during induction, intubation, and sternotomy. Maintenance of pulmonary capillary wedge pressure by volume infusion may have been contributed to this stability.

Anesthesia, Intravenous↗