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Biomedical subjects

J G Ramsay

Publications and source records attributed to J G Ramsay.

At least 19 recordsLinked to original sources
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↗
PubMed1991

Esmolol.

Explore the source record for details and available documents.

Adrenergic beta-Antagonists↗
PubMed1991

Methods of reducing blood loss and non-blood substitutes.

A variety of techniques can aid the anaesthetist in reducing requirements for perioperative blood products. These include careful preoperative assessment of the patient, and employing techniques during surgery which reduce the blood pressure and help preserve the normal haemostatic mechanism. If the level to which haematocrit will be permitted to decrease is decided, then physiological crystalloid and/or colloid solutions may be used to maintain circulating volume. Where large volumes of fluids are required cardiac filling pressures should be monitored because of the complex nature of the fluid shifts which occur. There is no evidence that any one fluid (physiological crystalloids, colloids) is better than any other in terms of the incidence of perioperative morbidity.

Blood Loss, Surgical↗
PubMed1991

Weaning from ventilation after cardiopulmonary bypass: evaluation of a non-invasive technique.

Weaning of patients from IPPV after cardiopulmonary bypass (CPB) is usually monitored by frequent arterial blood gas analysis. Non-invasive monitoring has the advantage of providing continuous and instantaneous information and could reduce the frequency of arterial blood gas sampling. Twenty patients were studied to determine the reliability of capnometry and pulse oximetry in this situation. The effects of hypothermia and moderate haemodynamic instability were examined. A further 40 patients were then weaned using non-invasive monitoring. Correlation between PaCO2 and PETCO2 was 0.64-0.79 for the mass spectrometer and 0.67-0.81 for the infra-red analyser. No clinical problems arose. The detection rate for mild hypercarbia was 78.6 per cent and 50 per cent for hypoxia. Possible reasons for this are discussed. Once CO2 and O2 gradients are established, pulse oximetry and capnometry provide sufficiently reliable monitoring to enable weaning from IPPV, with the advantage of continuous display, and allow a reduction in the use of arterial blood gas analyses.

Adult↗
PubMed1991

Dose-related effects of isoflurane associated with low plasma concentrations of verapamil on global and regional function in normal and compromised canine myocardium.

Global and regional myocardial functions were studied in seven open-chest dogs with constant low plasma concentrations of verapamil as increasing concentrations of isoflurane (0.75, 1, 1.5 MAC) were administered in the presence of normal myocardial perfusion and after application of critical constriction of the left anterior descending coronary artery. In the presence of verapamil, increases in isoflurane concentrations caused dose-dependent myocardial depression both before and after critical coronary constriction. The systemic and coronary vasodilatation associated with high concentrations of isoflurane did not occur in the presence of verapamil. The association of verapamil with isoflurane caused regional myocardial dysfunction that worsened at high isoflurane concentrations. This regional dysfunction could not be antagonized in two dogs. The effects of isoflurane on regional function were not modified by application of a critical coronary constriction.

Animals↗
PubMed1991

Verapamil and nitrous oxide exert only minor effects on the normal myocardium in the presence of fentanyl.

While the association of inhalational anaesthetics and verapamil has been shown to cause myocardial dysfunction, the interactions between fentanyl, verapamil and nitrous oxide on regional function in normal hearts have not been investigated. Seven mongrel dogs were instrumented to measure aortic and left-ventricular pressure, aortic blood flow and apical and basal regional left-ventricular function (sonomicrometry). Haemodynamic values were recorded during anaesthesia with 1% halothane, fentanyl 100 micrograms kg-1 (followed by 1.5 micrograms kg-1 min-1) and then after the addition of verapamil 250 micrograms kg-1 over 30 min (followed by 60 micrograms kg-1 min-1). At each stage 67% nitrous oxide was added and recordings obtained before and during its administration. The addition of verapamil during fentanyl anaesthesia caused a moderate depression of global haemodynamics. Only little dysfunction of the apical region (9.5 +/- 2.4% post-systolic shortening) was noted. The addition of nitrous oxide caused a small amount of additional depression without significant regional dysfunction.

Anesthesia, Inhalation↗
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

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↗
PubMed1988

Effects of lignocaine and bupivacaine on regional myocardial function and coronary blood flow in anaesthetized dogs.

Empirical i.v. doses of lignocaine or bupivacaine of equal local anaesthetic potency were administered to halothane-anaesthetized dogs. Both local anaesthetics caused the expected depression of global haemodynamic function. Regional myocardial systolic shortening was depressed similarly by both agents. Regional myocardial dysfunction, seen as post-systolic shortening, occurred to a similar extent with both lignocaine and bupivacaine. Coronary blood flow and coronary perfusion pressure were significantly correlated during the administration of lignocaine; bupivacaine had erratic effects on coronary blood flow and no correlation between coronary blood flow and coronary perfusion pressure was seen. These results suggest that regional myocardial dysfunction occurs with both local anaesthetics and does not account for the apparent increased cardiotoxicity of bupivacaine. Bupivacaine did, however, cause wider individual variations compared with lignocaine with respect to coronary blood flow.

Anesthesia, General↗
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

The association isoflurane-verapamil causes regional left-ventricular dyssynchrony in the dog.

In ten dogs anesthetized with 1% inspired isoflurane, the effect of low-dose verapamil on global and regional myocardial function was studied. The administration of verapamil resulted in no change in heart rate or blood pressure, but left ventricular stroke work, peak power, LV dP/dt max, and aortic blood acceleration were significantly reduced, while coronary blood flow remained unchanged. End-diastolic length increased in territory supplied by both left anterior descending (LAD) and left circumflex (LC) artery, but a significant decrease in systolic shortening occurred in the LAD segment only. Dyssynchrony of wall motion, characterized by post-systolic shortening, accompanied in three animals by a small amount of systolic lengthening, appeared with the administration of verapamil and was more pronounced in the LAD segment. Such patterns of wall motion have usually been attributed to myocardial ischemia. In the absence of significant reduction in coronary blood flow, and in the presence of a delay in onset of shortening and lengthening, these patterns of wall motion are more likely to reflect dyssynchrony of regional function than ischemia.

Anesthesia, Inhalation↗
PubMed1986

A ventilator for use in nuclear magnetic resonance studies.

The problem of ventilating small animals during nuclear magnetic resonance studies has been solved by using a T-piece system with a remotely controlled non-magnetic expiratory valve. This system does not affect the NMR signal, has minimal internal compliance and expiratory resistance, permits accurate control of peak airway pressure, and may be of use when animals have to be ventilated in hazardous surroundings.

Animals↗
PubMed1986

Halothane-verapamil causes regional myocardial dysfunction in the dog.

Regional myocardial function was studied using sonomicrometry in six mongrel dogs, anaesthetized with halothane (1% inspired), as increasing doses of verapamil were given i.v. In addition to a gradual increase in end-diastolic length and a reduction in systolic shortening, an abnormal (paradoxical) contraction pattern appeared in the apical region. This occurred in the absence of coronary artery damage and at coronary perfusion pressures unlikely to result in ischaemia. Administration of verapamil in the presence of halothane results in regional dysfunction similar to that caused by the intracoronary administration of nifedipine.

Animals↗