The effect of an infusion of esmolol on the incidence of myocardial ischaemia during tracheal extubation following coronary artery surgery.

The aim of this randomised controlled study was to determine whether an esmolol infusion affected the incidence of ST segment changes during weaning from intermittent positive pressure ventilation and tracheal extubation after coronary artery surgery. Thirty-one patients received an infusion of esmolol 0-300 microg x kg(-1) x min(-1) and 37 patients comprised the control group. ST segment changes were monitored using a continuous ambulatory surveillance system. The electrocardiogram, direct arterial pressure and pulse oximetry were monitored continuously. The period of analysis was from 120 min before until 180 min after tracheal extubation. Three patients in the esmolol group developed myocardial ischaemia during the study period compared with 12 in the control group (p = 0.05). Heart rate increased with time during the study period (p = 0.002) in the control group but was unchanged in the esmolol group. Mean heart rate was significantly higher in the control group than in the esmolol group from 40 min before until 180 min after tracheal extubation. Seven patients in the esmolol group suffered adverse events related to the esmolol infusion. Although the use of esmolol reduced the incidence of myocardial ischaemia, the incidence of adverse effects makes it unsuitable prophylaxis for patients after coronary artery surgery.

Comparison of the hemodynamic effects of milrinone with dobutamine in patients after cardiac surgery.

OBJECTIVE: To compare the hemodynamic effects, efficacy, and safety of intravenous milrinone (M), 50 microg/kg during 10 minutes followed by 0.5 microg/kg/min, with intravenous dobutamine (D), 10 to 20 microg/kg/min, in patients with low cardiac output after cardiac surgery. DESIGN: Randomized, open-label, multicenter study. SETTING: Cardiothoracic surgery departments, operating rooms, and intensive care units in 6 university hospitals. PARTICIPANTS: Patients (n = 120; 60 per group) after elective cardiac surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Analysis compared the hemodynamics at baseline and the percentage change from baseline during 4 hours of the drug infusion. The incidence of adverse events was recorded. Both groups had low mean (+/- SEM) cardiac indices (M, 1.6 ([0.03] L/min/m(2); D, 1.7 [0.03] L/min/m(2)) in association with adequate mean pulmonary capillary wedge pressures (M, 13.7 [1.3] mmHg; D, 12.7 [1.9] mmHg) at baseline. Group M had significantly higher systemic arterial pressures and systemic vascular resistances compared with group D; otherwise, the hemodynamics in both groups were comparable. During the study, hemodynamic responses included the following: group D had greater increases in cardiac index (at 1 hour, D = 55%, M = 36%; p < 0.01), heart rate (at 1 hour, D = 35%, M = 10%; p < 0.001), arterial pressures (mean arterial pressure at 1 hour, D = 31%, M = 7%; p < 0.001), and left ventricular stroke work index (at 1 hour, D = 75%, M = 45%; p < 0.05). Group M had greater decreases in mean pulmonary capillary wedge pressure (at 1 hour, D = -3%, M = -14%; p < 0.05). Comparisons of adverse events showed that dobutamine was associated with a higher incidence of hypertension (D = 40%, M = 13%; p < 0.02) and change of rhythm from sinus to atrial fibrillation (D = 18%, M = 5%; p < 0.04). Milrinone was associated with a higher incidence of sinus bradycardia (D = 2%, M = 13%; p < 0.03). CONCLUSIONS: Milrinone and dobutamine are appropriate and comparable for the pharmacologic treatment of the low- output syndrome after cardiopulmonary bypass.

Effect of anaesthesia on the cardiac response to intravenous adenosine.

The cardiac response to intravenous adenosine 112 micrograms kg-1 was studied in 16 patients scheduled for coronary artery bypass surgery before and during anaesthesia with 1% end-tidal isoflurane and fentanyl 10 micrograms kg-1. Mean time from injection to onset of adenosine-induced PR prolongation was significantly greater during anaesthesia (12.8 (SD 5) vs 9.9 (3) s, P = 0.032). Atrioventricular block (assessed by the total number of non-conducted P waves) was significantly less during anaesthesia (12 vs 27, P = 0.016). We conclude that anaesthesia including 1% isoflurane and fentanyl 10 micrograms kg-1 delays the onset and reduces the magnitude of adenosine-induced atrioventricular block.

Perioperative myocardial ischaemia, heart rate and arrhythmia in patients undergoing thoracotomy: an observational study.

We have studied myocardial ischaemia, heart rate and arrhythmia in 82 patients undergoing elective thoracotomy. Myocardial ischaemia was detected using a microprocessor-based surveillance system programmed to record leads V2 and V5. Patients were monitored on the day before and for up to 72 h after surgery. The total monitoring time was 5158 h. The incidence of silent myocardial ischaemia before operation was 11% (nine of 82). This increased to 24% (20 of 82) after operation. Postoperative myocardial ischaemia was associated with preoperative myocardial ischaemia in six patients. Before operation, the mean duration of myocardial ischaemia was 0.31 min per hour of monitoring. After operation, this increased to 1.36 min per hour of monitoring (P < 0.05). For the whole population, mean heart rate before operation was 74 beat min-1 and increased to 84 beat min-1 after operation (P < 0.01). Patients with ischaemia had a mean heart rate of 92.8 beat min-1 after operation compared with those with no ischaemia whose mean heart rate was unchanged at 81.8 beat min-1 (P < 0.05). The incidence of atrial tachyarrhythmia increased from one patient before operation to 12 patients after operation (P < 0.01). Atrial tachyarrhythmia was not associated with postoperative myocardial ischaemia. Nine patients had an adverse operative outcome; two had non-fatal myocardial infarction and seven died. Postoperative myocardial ischaemia was associated with adverse outcomes (P < 0.05).

Antiemetic prophylaxis in cardiac surgery: comparison of metoclopramide and ondansetron.

We have compared the effectiveness of ondansetron (115 patients) and metoclopramide (101 patients) for prevention of postoperative nausea and vomiting in patients undergoing cardiac surgery involving cardiopulmonary bypass. In a prospective, randomized, controlled, double-blind study, patients received oral ondansetron 16 mg or oral metoclopramide 10 mg, 1-2 h before surgery. Anaesthesia was not standardized. Assessments of the severity of nausea and occurrence of vomiting were made at intervals after extubation and until discharge from the intensive care, or for a total of 24 h. Compared with the metoclopramide group, the ondansetron group had a higher incidence of nausea (49.6% vs 33.7%; P < 0.05) and vomiting (42.6% vs 24.8%; P < 0.01). There was no difference between groups in the number of patients who accepted postoperative antiemetics (ondansetron 43.4% vs metoclopramide 32.6%) and there was no difference in the incidence of symptoms of moderate or severe nausea.

Myocardial ischaemia during tracheal extubation in patients after cardiac surgery: an observational study.

This study examines whether there is a temporal relationship between tracheal extubation and myocardial ischaemia in haemodynamically stable patients extubated within 6 h of cardiac surgery. Fifty-two patients were studied during three time periods: 1, from 2 h until 30 min before extubation (90 min); 2, from 30 min before until 30 min after extubation (60 min); 3, from 30 min until 2 h after extubation (90 min). Significant ST segment changes were defined as a reversible ST segment depression of 2 mm or greater or an elevation of 3 mm or greater from baseline, lasting for 1 min or more. Fourteen patients (26.9%) had ST segment changes. The ischaemic burden in periods 2 and 3 was increased compared with that in period 1; the mean (SD) was: period 1, 19.2 (18.8) min; period 2, 35.4 (24.9) min; period 3, 39.6 (24.5) min; however, the mean ST deviation (mm) did not change. ST segment changes were associated with an increased heart rate; they were not related to arterial pressure. We conclude that there is a temporal relationship between ST segment changes and tracheal extubation after cardiac surgery.

An evaluation of the Spuncrit infra-red analyser for measurement of haematocrit.

An open, single centre study was carried out to evaluate the accuracy of the Spuncrit (Micro Diagnostics, Bethlehem, PA, USA) infra-red analyser which can be used for near-patient testing to measure haematocrit and estimate haemoglobin concentration. The primary comparison was with the Sysmex NE1500 (Tao Medical) analyser situated in the main hospital laboratory. Secondary comparison was with the Ciba Corning 288 (Ciba Corning Diagnostics Ltd, Halstead, UK) blood gas analyser currently used for near-patient testing in the Northern General Hospital. A total of 217 samples from 50 patients was analysed. The Pearson's correlation coefficients for haematocrit and haemoglobin concentration between the Spuncrit and Sysmex NE1500 and between the Spuncrit and Ciba Corning 288 were all close, between 0.85 and 0.92. The method of Bland and Altman was used to assess agreement between the results of the Spuncrit and the Sysmex NE1500. The agreement for haematocrit was good with 2 SD of the Spuncrit results being between -5.66 and +4.42% of the measurement from the Sysmex NE1500. In conclusion, the Spuncrit haematocrit measurement agreed well with results from the central laboratory, but the estimated haemoglobin concentrations agreed less well and three reasons are discussed.

An economic evaluation of propofol/fentanyl compared with midazolam/fentanyl on recovery in the ICU following cardiac surgery.

A comparison was made of the drug costs and nursing dependency of patients undergoing elective cardiac surgery and routine postoperative recovery for two anaesthetic techniques using either propofol with low dose fentanyl or midazolam with high dose fentanyl. Estimates of resource use were based on a randomised clinical trial undertaken at the Northern General Hospital, Sheffield. Times from entry to the intensive care unit until extubation and discharge were recorded for 70 patients and were transformed to nursing shifts. Nursing dependency was calculated on the basis of one nurse per ventilated patient and 0.5 nurse from the start of the shift after extubation. Nursing costs were allocated on the basis of the patient's status at the beginning of each shift in line with the hospital's staffing policy. All drugs used from the morning of the operation until discharge were recorded. Costs of nursing and drugs were calculated. The total cost of patients in the propofol group was 13.3% less than midazolam patients (p = 0.043, for geometric means Cl 0.4% to 27.8%). The clinical study was not designed for economic endpoints; however, it demonstrated achievable savings in propofol-treated patients.

Comparison of the use of a propofol infusion in cardiac surgical patients with normal and low cardiac output states.

OBJECTIVES: This study compared the hemodynamic effects of a propofol infusion with fentanyl analgesia in patients undergoing cardiac surgery with normal and low cardiac output states. Low cardiac output was defined as a cardiac index less than 2.5 L/min/m2 with a minimum pulmonary capillary wedge pressure of 7 mmHg. DESIGN: A prospective and open study. SETTING: A single center cardiothoracic unit within a teaching hospital. PARTICIPANTS: Patients were assigned to group P, poor cardiac output or group N, normal cardiac output, after thermodilution pulmonary artery catheter assessments. INTERVENTIONS: Both groups received a propofol infusion, 8 mg/kg/hr, until induction of anesthesia, followed by 4 mg/kg/hr until the intensive care unit. Fentanyl, 15 micrograms/kg, and pancuronium, 0.15 mg/kg, were administered after induction. The lungs were ventilated with oxygen. MEASUREMENTS AND MAIN RESULTS: Hemodynamic assessments were repeated at intervals until cardiopulmonary bypass. Changes within and between groups were compared using t tests on percentage change from baseline. Group N had significantly greater decreases in cardiac index, stroke volume, and left ventricular stroke work index than group P. There were comparable decreases in mean arterial pressure on induction of anesthesia, 14% and 8% in group N and group P, respectively. In both groups, right ventricular ejection fraction was unchanged. CONCLUSIONS: The use of a propofol infusion for induction and maintenance of anesthesia in patients with low cardiac output states undergoing cardiac surgery is not contraindicated.

Comparison of propofol and fentanyl anaesthesia in coronary artery versus valve surgery.

Total intravenous anaesthesia with propofol and fentanyl was used in 23 patients undergoing coronary artery and 16 patients undergoing valve surgery and the haemodynamic effects in the two groups were compared. Baseline values showed that the valve surgery group had a higher mean heart rate, pulmonary artery wedge pressure and pulmonary artery pressure and smaller mean stroke volume than the coronary artery surgery group. In both groups, heart rate, arterial pressure, pulmonary artery wedge pressure, pulmonary artery pressure and cardiac index decreased during surgery. In the valve surgery group there were greater percentage decreases in heart rate, mean arterial pressure and diastolic arterial pressure. Overall, propofol and moderate-dose fentanyl anaesthesia was no more detrimental to the haemodynamics in patients undergoing valve surgery when compared to those undergoing coronary artery surgery.

Arterial and jugular venous bulb blood propofol concentrations during induction of anesthesia.

The aim of this study was to show that blood propofol concentrations at loss of consciousness vary with the rate of administration. Eighteen patients were allocated to receive a propofol infusion at 6 or 12 mg.kg-1.h-1 (approximately 8 and 15 mg/min) for induction of anesthesia. Propofol concentrations were analyzed from simultaneous arterial and jugular bulb venous blood samples. There were no significant differences in the dose of propofol administered to induce anesthesia (0.52 mg/kg both groups). However there were significant differences between the groups in the mean induction times (309 and 156 s), and in median arterial and venous concentrations at induction. Arterial concentrations were 1.93 and 2.70 and venous 1.11 and 1.51 micrograms/mL. There were no significant differences between the groups in the area between the arterial and venous time concentration curves from start of infusion to loss of consciousness (3.14 and 3.05 micrograms.mL-1.min-1). This study confirms that a target blood concentration of propofol cannot be identified with loss of consciousness under nonsteady state conditions. Both arterial and venous blood propofol concentrations at loss of consciousness depend on the rate of administration.

Changes in gastric tissue oxygenation during mobilisation for oesophageal replacement.

We have measured changes in gastric tissue oxygen tension (PtO2, mmHg), with a modified Clark oxygen electrode, in eight patients (median age 59 years, range 52 to 74) undergoing oesophagectomy for carcinoma. Operations were performed with a cervical anastomosis and the stomach mobilised on the right gastric and gastroepiploic arteries. Tissue oxygen tension was measured in the gastric fundus at 4 points: (1) before mobilisation, (2) after mobilisation with the stomach in the abdomen, (3) with the fundus lifted to the neck and (4) after anastomosis. From a mean of 77 mmHg before mobilisation, PtO2 was halved to 36 mmHg after mobilisation with no further fall after transposition to the neck or anastomosis. Arterial oxygen concentration (PaO2), mean arterial pressure (MAP) and oxygen delivery (DO2) were similar at each point. Tissue oxygen tension was correlated with PAO2 at points 1 and 4 but MAP only at point 1 and DO2 not at all. These findings document the relationship of gastric PtO2 to mobilisation of the stomach and demonstrate the important influence of PaO2 on PtO2.

Propofol and fentanyl anaesthesia for patients with low cardiac output state undergoing cardiac surgery: comparison with high-dose fentanyl anaesthesia.

We have compared the haemodynamic effects of an infusion of propofol 8 mg kg-1 h-1 followed by 4 mg kg-1 h-1 and fentanyl 15 micrograms kg-1 (group 1) with midazolam 3-6 mg and fentanyl 60 micrograms kg-1 (group 2) in patients with a low cardiac output state undergoing cardiac surgery. Heart rate was lower in group 1 throughout the period before cardiopulmonary bypass. There were no significant differences between the groups in other measured variables. Arterial pressure decreased in both groups after induction, by 21% in group 1 and 18% in group 2. Thermodilution assessment of right ventricular ejection fraction was unchanged. Myocardial contractility was not affected adversely. Patients in group 1 who received an infusion of propofol and a smaller dose of fentanyl awakened sooner and the trachea was extubated earlier.

Disposition of milrinone in patients after cardiac surgery.

We have evaluated the disposition of milrinone in seven patients with low cardiac output after elective cardiac surgery involving cardiopulmonary bypass. Patients received a loading dose of milrinone 50 micrograms kg-1 given over 10 min followed immediately by an infusion of 0.5 microgram kg-1 min-1, continued for a minimum of 5 h. Plasma concentrations of milrinone were measured at designated intervals during the infusion and for 6 h after its termination, by high pressure liquid chromatography. Concentrations greater than 100 ng ml-1 were produced in all patients within 2 min of starting the loading dose and were maintained for the duration of the infusion. Volume of distribution, clearance and terminal half-life were similar to those found in patients with chronic cardiac failure.

Comparison of the haemodynamic effects of enoximone and piroximone in patients after cardiac surgery.

We have compared the haemodynamic effects of the imidazole derivative phosphodiesterase inhibitors enoximone and piroximone in patients with low cardiac output after cardiac surgery. Ten patients (group E) received enoximone and 10 patients (group P) received piroximone, both at a loading dose of 0.5 mg kg-1 followed by an infusion of 5 micrograms kg-1 min-1. In both groups the main changes with time were increases in cardiac index (maximum 24.5% in group E, 25.8% in group P) and decreases in systemic vascular resistance (maximum 26.8% in group E and 24.8% in group P). There were moderate increases in heart rate (maximum 11.3% in group E and 13% in group P) but a greater percentage decrease in mean arterial pressure in group E (maximum 11.9% vs 7.9%) with time. One patient in group E developed hypertension during the loading dose. Two patients in group E and two in group P developed hypotension during the loading dose. One patient in group E developed ventricular extrasystoles which may have been related to the drug being studied.

A combined chest drain and intrapleural catheter for post-thoracotomy pain relief.

This study examined the effectiveness of a new type of chest drain, which incorporates an additional lumen within its wall to facilitate the administration of intrapleural bupivacaine. Nine patients who received a bolus dose of 1.5 mg.kg-1 bupivacaine with 1:200,000 adrenaline through this chest drain used less morphine, and had lower visual analogue pain scores in the first 6 h after thoracotomy than patients in whom a standard chest drain had been used. Bupivacaine levels were found to be within safe limits in all patients.

Use of milrinone in cardiac surgical patients.

Milrinone is shown in 10 patients to be a valuable pharmacological bridge to heart transplantation; it can stabilize and improve decompensated chronic heart failure (CHF) in cases where the response to beta-agonists is inadequate. One patient who had suffered an acute myocardial infarction with heart failure resistant to vasodilators, beta-agonists, and balloon counterpulsation was stabilized with milrinone for 21 days. He was then maintained on ACE inhibitors until heart transplantation 3 months later. The other nine patients with severe decompensated CHF were stabilized on milrinone for between 11 and 51 days. Seven of them received a donor heart. Two patients died of bacteremic shock and terminal heart failure before a suitable organ could be found (31 and 51 days). All patients were clinically improved within 48 hours of the addition of IV milrinone to their therapy. In 55 patients following cardiac surgery, the efficacy and safety of milrinone in the treatment of low cardiac output states is demonstrated. Milrinone has a useful role in the management of patients with circulatory failure both before and after cardiac surgery, and this paper reviews the relevant current literature.