Biomedical subjects

R O Feneck

Publications and source records attributed to R O Feneck.

At least 37 records · Page 2Linked to original sources

PubMed1993

Time-course of free radical activity during coronary artery operations with cardiopulmonary bypass.

Myocardial and pulmonary impairment after cardiopulmonary bypass may be caused by oxygen free radicals produced by reperfusion and by activated neutrophils. Free radical activity was assessed by assays for lipid peroxidation (thiobarbituric acid-reactive material) and phospholipid-esterified diene conjugation (18:2[9,11]/18:2[9,12] molar ratio) in 25 patients during coronary artery operations. Arterial blood samples were obtained before, during the ischemic period, and for 24 hours thereafter. There were no significant changes in free radical indices during the ischemic periods, but after cessation of bypass they increased significantly. Ten minutes after bypass thiobarbituric acid-reactive material rose from 96 (median; range 65 to 145) nmol/gm albumin to 138 (85 to 200) nmol/gm albumin (p < 0.001), and molar ratio rose from 2.23% (0.45% to 7.70%) to 2.51% (0.39% to 7.93%) (p < 0.02). Values of thiobarbituric acid-reactive material subsequently decreased, but molar ratio reached a peak at 4 hours after bypass, 2.64% (0.55% to 10.08%) (p < 0.001), thereafter returning to baseline. The postoperative increases in thiobarbituric acid-reactive material and in molar ratio were correlated (r = +0.53; p = 0.006). These increases in thiobarbituric acid-reactive material and in molar ratio were not related to age, preoperative left ventricular function, or the number of grafts performed. Increase in thiobarbituric acid-reactive material correlated with the duration of cardiopulmonary bypass (r = +0.43; p = 0.03). In 10 patients in whom cardiopulmonary bypass was performed using a bubble oxygenator, the increases in thiobarbituric acid-reactive material were significantly greater than in the 15 in whom a membrane oxygenator was used (p < 0.02). These data show that after apparently uncomplicated coronary operations with bypass there is an increase in lipid peroxidation and diene conjugation, indicating increased free radical activity. This increase varies between patients and does not relate to patient or surgical factors but may depend on the type of oxygenator employed during bypass.

Adult↗

PubMed1992

Intravenous milrinone following cardiac surgery: I. Effects of bolus infusion followed by variable dose maintenance infusion. The European Milrinone Multicentre Trial Group.

The hemodynamic and adverse effects of intravenous milrinone were studied in 99 adult patients (66 men) following elective myocardial revascularization, mitral and/or aortic valve surgery. All patients had a low cardiac output (cardiac index [CI] mean 1.93, range, 1.11 to 2.5 L/min/m2) despite adequate cardiac filling pressure (mean pulmonary capillary wedge pressure [PCWP] 11.5 mmHg, range, 8 to 20 mmHg). Following a period of baseline stability (mean 17.8 minutes, range, 10 to 50 minutes), patients received a bolus infusion of 50 micrograms/kg over 10 minutes. A continuous maintenance infusion of 0.375 (low), 0.5 (mid) or 0.75 (high) micrograms/kg/min was administered for a minimum of 12 hours. Patients were allocated to each dosage group sequentially, not randomly. Hemodynamic measurements were made before the start of milrinone and 15 minutes after the bolus infusion. Further measurements were made at 30, 45, and 60 minutes, and at 3, 6, and 12 hours after the start of treatment. Measurements were also made at 2 and 4 hours after treatment was stopped. The bolus infusion caused significant increases in CI, heart rate (HR), and stroke index (SI), (P < 0.001), and significant falls in PCWP, right atrial pressure (RAP), mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR), mean arterial pressure (MAP), and systemic vascular resistance (SVR) (P < 0.001). These effects were maintained to a significant degree by each of the three maintenance infusion regimens, although the pulmonary vasodilator effects appeared less predictable and more dose dependent. Eighteen patients (19%) had arrhythmias; 16 of these were judged not to be serious events. Two were deemed serious; these were both episodes of fast atrial fibrillation (AF).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Intravenous milrinone following cardiac surgery: II. Influence of baseline hemodynamics and patient factors on therapeutic response. The European Milrinone Multicentre Trial Group.

Further analysis of the data from 99 adult patients who received an intravenous infusion of milrinone following elective cardiac surgery was done. All patients received a bolus infusion of 50 micrograms/kg over 10 minutes, followed by a maintenance infusion of either 0.375, 0.5 or 0.75 microgram/kg/min for a period of 12 hours. Hemodynamic measurements were made after the bolus infusion (15 minutes), and then after 30, 45, and 60 minutes at 3, 6, and 12 hours, and 4 hours after treatment was stopped. The following was found: (1) pretreatment cardiac index (CI) affected the response to treatment. Patients with a low CI (1.59 L/min/m2) had a 54% increase after the bolus infusion compared to a 27% increase in patients with a higher pretreatment value (2.2 L/min/m2) (P < 0.05); (2) patients with a high resting level of pulmonary vascular resistance (PVR > 200 dynes.sec.cm-5) had a greater response to treatment (26% fall in PVR) than the remainder (9% fall in PVR) after 60 minutes; (3) patients with a low pretreatment mean arterial pressure (MAP) (n = 17, MAP 64 mmMg, range, 52 to 70) showed no fall in MAP following treatment, but showed a significant increase in CI (+55%). A good therapeutic response was found that was similar in patients undergoing valve replacement surgery or coronary artery bypass graft surgery, and in patients in sinus rhythm or atrial fibrillation before treatment. It is concluded that the therapeutic response to intravenous milrinone following cardiac surgery is partially determined by pretreatment hemodynamics.

Adult↗

PubMed1992

Anaesthesia for myocardial revascularisation. A comparison of fentanyl/propofol with fentanyl/enflurane.

We studied the effects on myocardial performance and metabolism of fentanyl/propofol and fentanyl/enflurane anaesthesia in 20 patients before coronary artery bypass grafting. Anaesthesia was induced with fentanyl 20 micrograms.kg-1 and pancuronium 0.15 mg.kg-1. Patients received, by random allocation, either propofol by infusion, 6 mg.kg-1.h-1 reduced by half after 10 min then adjusted as necessary (mean rate 2.8 mg.kg-1.h-1), or enflurane 0.8% inspired concentration for 10 min reduced to 0.6% and adjusted as required (mean 0.7%). Measurements were made before induction, after tracheal intubation, after skin incision and after sternotomy. There were no significant differences between the groups in any haemodynamic variables during the study. Following intubation both groups showed a rise in heart rate (p < 0.01) and cardiac index (p < 0.05). Systemic vascular resistance decreased after intubation (p < 0.05) then returned to baseline during surgery; stroke index was unchanged after intubation but was reduced during surgery (p < 0.01) as systemic vascular resistance increased. Regional and global coronary blood flow were maintained in both groups, as were myocardial oxygen consumption and lactate extraction ratio. However, lactate production did occur in one patient receiving enflurane and Holter monitoring confirmed ischaemia. One patient receiving propofol showed lactate production not accompanied by any ECG changes. This study suggests that propofol may be a suitable alternative to enflurane as an adjunct to opioids in anaesthesia for coronary artery bypass grafting.

Anesthesia, Inhalation↗

PubMed1992

Preoperative laser therapy in a patient with resectable bronchogenic carcinoma and severe coronary artery disease.

A 67 year old man with severe coronary artery disease was found to have a resectable bronchogenic carcinoma. Myocardial revascularisation and lung resection were considered to be unduly hazardous as either separate or combined operations. Preoperative laser therapy, however, enabled the two procedures to be performed in greater safety in the most appropriate sequence.

Aged↗

PubMed1992

Overview of the effects of intravenous milrinone in acute heart failure following surgery.

We have reviewed the current data evaluating the effects of intravenous milrinone in patients following cardiac surgery. Milrinone has been shown to be effective in the treatment of acute low output syndrome, and a loading bolus infusion of 50 micrograms kg-1 over 10 min causes an increase in cardiac index and a fall in pulmonary capillary wedge pressure. These effects are easily maintained by a continuous infusion regimen. Other haemodynamic effects are seen, including systemic and pulmonary vasodilatation and an increase in heart rate. These effects are not confined to one patient group, but the increase in cardiac index does appear to be more pronounced in those patients with poor haemodynamics prior to treatment. There is a low incidence of adverse events including arrhythmias and hypotension. Thus milrinone appears to be well tolerated in a broad group of adult patients recovering from cardiac surgery.

Cardiac Output↗

PubMed1991

Effects of variable dose milrinone in patients with low cardiac output after cardiac surgery. European Multicenter Trial Group.

We studied 99 adult patients after elective cardiac surgery who had low cardiac output (cardiac index less than 2.5 L/min/m2) in spite of adequate cardiac filling pressure (pulmonary capillary wedge pressure less than 8 mm Hg). Patients received milrinone by loading dose (50 micrograms/kg over a 10-minute period), followed by a continuous infusion of either 0.375, 0.5, or 0.75 micrograms/kg/min (low-, middle-, and high-dose groups, respectively) given for a minimum of 12 hours. Patients were allocated to each dosage group sequentially, not randomly. Hemodynamic measurements were made before the loading dose and at 15, 30, 45, and 60 minutes, 3, 6, and 12 hours after the start of milrinone therapy. Further measurements were made at 2 and 4 hours after treatment was stopped. Milrinone therapy was associated with a rapid, well-sustained, and highly significant increase in cardiac index in all three dose groups (p less than 0.001), and a similar fall occurred in pulmonary capillary wedge pressure in all groups (p less than 0.001). Significant increases occurred in heart rate in all three groups (p less than 0.001). Systemic and pulmonary vascular resistance also fell significantly, although changes in this latter parameter were less predictable and more dose dependent. Few serious treatment-related adverse effects were seen. We conclude that intravenous milrinone is an effective and safe therapy for the treatment of low output states after cardiac surgery.

Cardiac Output↗

PubMed1991

Comparison of isradipine with nitroprusside for control of blood pressure following myocardial revascularization: effects on hemodynamics, cardiac metabolism, and coronary blood flow.

The effects of isradipine (ISR) on cardiac performance, myocardial metabolism, and coronary blood flow were compared with those of sodium nitroprusside (SNP) when used to control blood pressure following myocardial revascularization. Twenty patients were randomized to receive either intravenous ISR or SNP if arterial blood pressure increased above 130 mm Hg systolic. Hemodynamic and metabolic parameters were studied using radial, pulmonary arterial, and coronary sinus catheters. Cardiac output and coronary blood flows were measured by thermodilution and blood was taken for calculation of myocardial oxygen consumption and lactate extraction. Electrocardiographic changes were recorded by Holter monitoring throughout the study. ISR and SNP both produced a satisfactory reduction in blood pressure accompanied by a decreased systemic vascular resistance (P less than 0.001). ISR infusion was associated with increases in cardiac output and stroke index (P less than 0.01), which were not apparent in the SNP group. Tachycardia occurred with SNP (P less than 0.01) but not with ISR therapy. Right and left ventricular stroke work indices and myocardial oxygen consumption were reduced with SNP. The ISR group showed unchanged myocardial oxygen consumption with increased right ventricular stroke work index. Coronary vascular resistance decreased (P less than 0.01) during ISR infusion but decreased only slightly in the SNP group. Great cardiac vein blood flow was significantly increased with ISR but not with SNP, resulting in a significant difference between the groups (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

The haemodynamic effects of bronchoscopy. Comparison of propofol and thiopentone with and without alfentanil pretreatment.

The haemodynamic response to bronchoscopy under general anaesthesia was investigated. Forty patients were allocated at random to receive either thiopentone or propofol; half the patients in each group received in addition 18 micrograms/kg of alfentanil one minute before induction of anaesthesia. The heart rate, noninvasive blood pressure and Holter ECG was monitored in all patients. Significant increases in heart rate (p less than 0.05), systolic and diastolic arterial pressures (p less than 0.01) occurred in the thiopentone only group, following bronchoscopy. Systolic and diastolic arterial pressure decreased in patients receiving thiopentone plus alfentanil, following induction of anaesthesia and laryngoscopy (p less than 0.05). No significant haemodynamic changes were seen in either of the groups which received propofol. ST segment changes on subsequent Holter analysis were seen in four patients, but there were no significant differences between the groups. Anaesthesia with propofol alone provides adequate haemodynamic stability for bronchoscopy and the addition is superfluous.

Aged↗

PubMed1990

Effects of the inotrope DPI 201-106 on cardiac performance following cardiac surgery.

The haemodynamic, cardiac metabolic and electrocardiographic effects of the intravenous inotropic agent DPI 201-106, in 20 and 40 milligram doses, were studied in patients after coronary arterial bypass grafting. The patients were randomly allocated to receive placebo or DPI 201-106. Those receiving the active drug received either the 20 or the 40 milligram dosages of DPI 201-106. Both the placebo and the active drug were infused over 20 minute periods. Two baseline readings confirmed haemodynamic stability, and readings were taken immediately following the infusions and then at 20 minutes and at 40 minutes afterwards. Comparison of all the haemodynamic and metabolic data did not reveal any significant intra or inter group differences. Comparison of the electrocardiographic data revealed some differences. Patients receiving DPI 201-106 showed prolongation of the QTc interval immediately following the infusions. Changes in ST segments and T waves were observed. Independent analysis of the affected electrocardiographs reported that the changes were suggestive of, but not pathognomonic of, myocardial ischaemia. The metabolic data showed that the electrocardiographic changes were not associated with any evidence of anaerobic metabolism. The indication for DPI 201-106 as a positive inotropic agent in patients following coronary revascularization surgery was not established.

Adult↗

PubMed1990

Carboxyhaemoglobin concentrations, pulse oximetry and arterial blood-gas tensions during jet ventilation for Nd-YAG laser bronchoscopy.

Oxygen saturation measured with pulse oximetry (SpO2) is overestimated in the presence of carboxyhaemoglobin (COHb). Smoke produced during laser resection of tracheobronchial malignancies may increase concentrations of COHb. We have measured COHb concentrations in 14 patients undergoing laser resection and compared SpO2 with functional oxygen saturation (SaO2) to ascertain if pulse oximetry is an accurate monitor of oxygen saturation. During the procedure frequent changes occur in ventilatory mechanics. Arterial blood-gas tensions were measured to see if gas exchange was satisfactory. Mean preoperative COHb was 1.4%. There was no significant change in COHb in any patient at any stage during treatment. The highest value was 2.05%. The mean difference between SaO2 and SpO2 was 1.13% (95% confidence interval 0.70-1.56%). Oxygen saturation may therefore safely be monitored by pulse oximetry in patients managed by our technique. Empirical setting of a jet ventilator provided acceptable blood-gas tensions, although sometimes it was necessary to increase the FlO2 to greater than 0.3 to maintain oxygenation.

Adult↗

PubMed1990

Systemic pattern of free radical generation during coronary bypass surgery.

Diffuse impairment of ventricular function after cardiac surgery may be related to the generation during reperfusion of the myocardium of free radicals derived from oxygen. Fifteen patients undergoing elective coronary bypass surgery were studied by previously described assays for peroxidised lipids and for isomerised lipids which were used as indices of free radical activity. Serial blood samples were obtained from systemic arterial, mixed venous, and coronary sinus catheters before, during, and after the ischaemic period. The patients underwent coronary artery surgery on cardiopulmonary bypass with a membrane oxygenator, relative hypothermia 30-34 degrees C, and intermittent cross-clamping of the aorta. During the ischaemic periods there were no significant changes in the indices of free radical activity. During the reperfusion phase there was a significant increase in free radical indices in arterial and mixed venous blood. A small rise in free radical indices in coronary venous blood was not statistically significant. These data indicate that free radical activity is increased in patients shortly after the cessation of cardiopulmonary bypass. The pattern of distribution between the different sampling sites suggests that much of the observed increase in isomerised and peroxidised lipids originates from tissues other than the myocardium.

Adult↗

PubMed1989

Use of isradipine in hypertension following coronary artery bypass surgery.

A dose-finding pilot study including six patients concluded that isradipine at an initial rate of 0.6 microgram/kg/minute, decreasing to 0.3 microgram/kg/minute with further adjustments as necessary, was safe for the treatment of post-aortocoronary bypass graft hypertension. A comparative study followed, comprising 20 patients randomly assigned to receive isradipine (starting at 0.6 microgram/kg/minute) or nitroprusside (initially 1 microgram/kg/minute) for the treatment of post-aortocoronary bypass graft hypertension. Both drugs produced a satisfactory reduction in arterial blood pressure accompanied by a decrease in systemic vascular resistance. Central venous pressure and mean pulmonary artery pressure decreased with nitroprusside, but both increased with isradipine. Pulmonary capillary wedge pressure was reduced, heart rate increased, and cardiac output was minimally changed with nitroprusside. However, wedge pressure was maintained with isradipine and there was no tachycardia. An increase in cardiac output was seen, associated with an increase in stroke index. Isradipine is a more specific treatment for post-aortocoronary bypass graft hypertension than nitroprusside because its systemic arterial dilating effect is associated with a minimum of other circulatory changes.

Adolescent↗

PubMed1989

The effects of intravenous nitroglycerin and isosorbide dinitrate on hemodynamics and myocardial metabolism.

Myocardial ischemia before and during coronary artery surgery is significant, because patients who develop perioperative myocardial ischemia have an increased incidence of postoperative myocardial infarctions. Thus, the prevention of ischemic episodes is of great importance. This study was undertaken to (1) compare the effects of intravenous nitroglycerin (NTG) with isosorbide dinitrate (ISDN); (2) investigate if the continuous infusion of nitrates had beneficial effects on cardiac performance and metabolism; and (3) compare the control of blood pressure with the nitrates versus halothane during a standardized anesthetic. Twenty-one patients participated in the study, and all had the following: a radial arterial catheter, peripheral venous catheter, 7F pulmonary artery catheter, and Baim coronary sinus flow catheter. The study was carried out in the prebypass period beginning with awake measurements of baseline parameters, and ending after median sternotomy. The patients were divided into three groups: group 1 received an infusion of NTG; group 2 received an infusion of ISDN; and group 3, the control, received neither nitrate, but halothane was added to control hemodynamics. Measurements were made at the following time intervals: (1) baseline; (2) after 5 minutes of the nitrate infusions while awake (groups 1 and 2); (3) after induction of anesthesia, laryngoscopy, and intubation; and (4) after median sternotomy. In groups 1 and 2, the nitrates were infused at 0.1 mg/kg/h for 5 minutes. Thereafter, blood pressure control and treatment of episodic hypertension were achieved by alteration of the rate of nitrate infusions, or, in group 3, by 0.5% to 2% of inspired halothane.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Intravenous nifedipine for control of hypertension in patients after coronary artery bypass graft surgery.

A study was undertaken to assess the use of intravenous nifedipine in controlling hypertension in patients following coronary artery surgery. A combined hemodynamic and metabolic assessment was carried out in 15 patients on data recorded at six sequential time intervals: (1) baseline, (2) control of blood pressure, (3) 30 minutes after control of blood pressure, (4) 1.5 hours after control of blood pressure, (5) 3.5 hours after control of blood pressure, and (6) 30 minutes after discontinuing nifedipine. Coronary sinus and great cardiac vein blood flows were measured by the continuous thermodilution technique using the Baim coronary sinus flow catheter. Intravenous nifedipine was run initially at an average rate of 1.82 microg/kg/min. It took an average time of 12 minutes to lower the blood pressure to less than 130 mmHg systolic. There were highly significant decreases in systolic, mean, and diastolic blood pressures (P < .001), associated with significant decreases in systemic vascular resistance (P < .001) and left ventricular stroke work index (P < .05). There was an increase in cardiac output at 30 and 90 minutes of infusion (P < .05), and the stroke volume was increased 90 minutes after starting nifedipine (P < .05). The increase in heart rate was not significant. There was no significant effect on conduction times as measured by PR and QRS intervals on the ECG. However, the QTc interval was decreased after 3.5 hours (P < .05). There was an increase in right atrial pressure at 90 minutes and again 30 minutes after stopping nifedipine. (P < .05). The pulmonary artery pressure also was increased after stopping the infusion (P < .05). The pulmonary capillary wedge pressure, pulmonary vascular resistance, and right ventricular stroke work index remained unchanged. Coronary sinus and great cardiac vein flows were maintained despite a decrease in perfusion pressure, suggesting that nifedipine is a potent coronary vasodilator. Indeed, coronary vascular resistance was significantly decreased (P < .05). Myocardial oxygen consumption remained unchanged. The lactate extraction indicated that myocardial metabolism remained aerobic regionally and globally. Thus, the results suggest that blood pressure was easy to control and that there were no adverse effects on atrioventricular conduction, cardiac performance, regional and global myocardial oxygen utilization, or lactate extraction.

Adult↗

PubMed1988

Thermodilution cardiac output measurements during conventional and high-frequency ventilation.

The thermodilution method for cardiac output determinations correlates well with Fick and dye dilution methods. Experimental work with thermodilution techniques has shown that individual measurements of right heart cardiac output during conventional ventilation vary throughout the respiratory cycle. The aims of this study were to compare thermodilution cardiac output determinations made at a fixed point (zero end-expiratory pressure [ZEEP]) with those made randomly throughout the respiratory cycle during conventional controlled positive pressure ventilation (CPPV) and high-frequency jet ventilation (HFJV) with up to 10 cm H2O positive endexpiratory pressure (PEEP). There were no statistically significant differences between the cardiac output determinations made at ZEEP and randomly in the ventilation cycle in any group and all correlations were significant. The clinical implications of these results are discussed, and it is concluded that it is not necessary to time the measurements of thermodilution cardiac output determinations during CPPV or HFJV with up to 10 cm H2O of PEEP.

Adult↗

PubMed1988

Sufentanil and nitrous oxide anaesthesia for cardiac surgery.

We have investigated the use of sufentanil 3.75-15 micrograms kg-1 by supplementing anaesthesia with nitrous oxide and midazolam. Thirty patients with ejection fractions exceeding 30% were studied while undergoing scheduled coronary artery vein graft surgery. Even in the lowest dose group (3.75 micrograms kg-1), haemodynamic responses to surgical and anaesthetic stimuli were sufficiently obtunded that no patient exhibited an increase in heart rate or systolic arterial pressure greater than 20% of the control value. Marked hypotension occurred in some patients during unstimulated periods. Such periods of hypotension were associated with equally marked decreases in systemic vascular resistance. The mean recovery times to spontaneous ventilation after the end of surgery ranged from 6 to 12 h. This is longer than would be expected from other studies using a similar dose of sufentanil. This may be related to the use of benzodiazepines during anaesthesia and to their use after surgery in those patients who became restless.

Anesthesia Recovery Period↗

PubMed1988

Bladder temperature as an estimate of body temperature during cardiopulmonary bypass.

Bladder temperature measured by a thermistor-tipped urinary catheter, was compared to oesophageal, nasopharyngeal, rectal and cutaneous temperatures in 33 patients during cardiopulmonary bypass. The bladder site was warmer than all other monitored sites in the pre-bypass period and showed least variation in temperature. The rate of change of bladder temperature during cooling and rewarming on bypass was significantly (p less than 0.01) lower than for oesophageal and nasopharyngeal temperatures, but was greater than or similar to the rate of change of rectal and cutaneous temperatures. This method of temperature measurement was found to be satisfactory during major surgery and also during the postoperative period in the intensive care unit.

Body Temperature↗