Comparative hemodynamic effects of propofol and thiamylal sodium during anesthetic induction for myocardial revascularization

The safety and efficacy of propofol, a new intravenous anesthetic agent, have been demonstrated in healthy patients. Twenty-one patients, ASA III-IV, undergoing elective myocardial revascularization, were randomly chosen to receive either propofol, 2.5 mg/kg, or thiamylal, 4 mg/kg. for the induction of anesthesia. Hemodynamics were recorded at one and three minutes after drug administration during spontaneous respiration. After the addition of halothane and pancuronium with controlled ventilation, measurements were made immediately prior to and one minute after intubation. Five patients were dropped from the study, four due to airway problems and one due to severe hypotension following an induction dose of propofol. Statistics were done using data from the remaining 16 patients, eight in each group. Administration of propofol resulted in significant decreases in mean arterial pressure (MAP), systemic vascular resistance (SVR), and left ventricular stroke work index (LVSWI); as well as an increase in heart rate (HR). These changes were further accentuated by the addition of halothane and pancuronium prior to intubation. Patients in the thiamylal group experienced no significant hemodynamic changes until halothane and pancuronium were added and controlled ventilation was instituted. With these additions, the thiamylal group showed significant decreases in MAP and LVSWI immediately prior to intubation. Both groups experienced significant increases in HR following intubation, but no evidence of myocardial ischemia was seen in either group. All other parameters returned toward control values. Propofol appeared to be safe and effective for the induction of anesthesia in this group of patients, although its hemodynamic effects were greater than those of thiamylal.

Haemodynamic effects of diltiazem during fentanyl-nitrous oxide anaesthesia. An in vivo study in the dog

The haemodynamic effects of diltiazem were studied in six dogs during fentanyl-nitrous oxide (in oxygen) anaesthesia. A bolus of diltiazem 300 micrograms kg-1 was given, followed by infusions at 30, 60 and 90 micrograms kg-1 min-1 which produced plasma diltiazem concentrations of 392 +/- 30, 908 +/- 54 and 1483 +/- 134 ng ml-1, respectively. Diltiazem significantly reduced systemic vascular resistance index, mean arterial pressure, heart rate and PR interval. The decrease in afterload increased cardiac index, since there was little change in myocardial contractility (LV dP/dt). Five dogs developed second degree atrioventricular (AV) block in association with the highest dose. Administration of calcium chloride 20 mg kg-1 did not reverse the haemodynamic or electrophysiological effects of diltiazem. Isoprenaline increased heart rate and restored sinus rhythm in four dogs with AV block.

Oxygenation and hemodynamic changes during one-lung ventilation: effects of CPAP10, PEEP10, and CPAP10/PEEP10

The effects of 10 cm H2O positive end-expiratory pressure (PEEP10), 10 cm H2O continuous positive airway pressure (CPAP10), and their combination (CPAP10/PEEP10) on oxygenation and hemodynamics were studied in 20 patients undergoing one-lung ventilation (OLV) with 50% nitrous oxide, isoflurane, and oxygen. Compared to OLV alone, CPAP10 and CPAP10/PEEP10 significantly increased PaO2 (from 80 +/- 6 to 125 +/- 11 and 137 +/- 17 mmHg, respectively); increased SaO2 (from 93.9 +/- 0.8 to 97.1 +/- 0.5 and 97.0 +/- 0.6%, respectively); and decreased Qs/Qt% (from 36.4 +/- 1.6 to 26.2 +/- 2.0 and 23.2 +/- 2.0%, respectively). Although not statistically significant, PEEP10 caused an increase in PaO2 (to 105 +/- 12 mmHg) and a decrease in Qs/Qt% (to 27.6 +/- 2.1%), which are of clinical significance. However, CPAP10/PEEP10 caused a significant decrease in cardiac output (from 4.50 +/- 0.26 to 3.83 +/- 0.22 L/min), stroke volume (58.6 +/- 3.0 to 52.8 +/- 2.9 mL/beat), and oxygen delivery (653 +/- 39 to 590 +/- 38 mL/min). Application of CPAP10, PEEP10 or their combination had no significant effect on heart rate, arterial, pulmonary arterial, mean pulmonary capillary wedge or central venous pressures, systemic or pulmonary vascular resistances, or mixed venous oxygen saturation. Overall, CPAP10 had the most beneficial effect on oxygenation and hemodynamics during OLV with 50% N2O, isoflurane and oxygen.

A comparison of hemodynamic indices derived by invasive monitoring and two-dimensional echocardiography

Intraoperative two-dimensional echocardiography (2D-echo) is useful for monitoring global and regional left ventricular function. The 2D-echo view most frequently utilized during intraoperative monitoring is the short-axis view at the level of the papillary muscles. To determine whether hemodynamic data can be derived from this single 2D-echo short-axis view, 12 patients undergoing coronary artery bypass grafting (CABG) were studied. All patients had normal left-ventricular function preoperatively (ejection fraction = 64% +/- 12%). Echo-data were obtained before and after cardiopulmonary bypass (CPB) by epicardial placement of a 5 MHz echo-transducer. The correlation between thermodilution and echo-derived cardiac indices was good (r = 0.8), and not significantly different from the correlation between stroke indices (r = 0.68). A strong positive correlation was established between end-diastolic volume index and echo cardiac index (CIE) (r = 0.93 before CPB; r = 0.91 after CPB) and end-diastolic area index and CIE (r = 0.94 before CPB; r = 0.91 after CPB). The pulmonary capillary wedge pressure was not a determinant of cardiac index before or after cardiopulmonary bypass. No correlation was observed between systemic vascular resistance and echo-derived wall stress. These findings demonstrate that, in patients with good left-ventricular function undergoing CABG surgery, 2D-echo provides a better index of left-ventricular preload than conventional invasive hemodynamic monitoring.

Control of catecholamine-induced tachycardia with alinidine in the anesthetized dog

Sinus tachycardia is a common complication of beta-adrenergic agonist therapy. A new selective bradycardic agent, N-allyl-clonidine, or alinidine, has been found effective against sinus tachycardia caused by a variety of stimuli. To determine whether it would also control catecholamine-induced sinus tachycardia, the effects of alinidine in two groups of anesthetized dogs treated with either dobutamine, 10 microg/ kg/min, or isoproterenol, 0.1 microg/kg/min, were studied. In both groups, alinidine significantly reduced the heart rate (P < .0001 in the dobutamine group, and P < .005 in the isoproterenol-infused dogs). The other hemodynamic effects of dobutamine were not adversely affected by alinidine, while the isoproterenol-infused dogs had a further afterload reduction when treated with alinidine. It is concluded that alinidine is effective against catecholamine-induced sinus tachycardia, possibly through mechanisms not related to beta-adrenergic receptors.

Myocardial ischaemia during non-cardiac surgery. A comparison of different lead systems using computerised ST segment analysis

Computerised ST segment analysis was used to compare the frequency of ischaemia occurring in electrocardiographic leads II, V5, CS5 and CB5. Three out of 15 patients with ischaemic heart disease developed ischaemic changes, which were evident in all four leads in each patient. A single bipolar lead may be substituted for a true V5 lead when monitoring patients at increased risk of developing myocardial ischaemia. ST segment analysis facilitates the early diagnosis of peri-operative myocardial ischaemia, which may otherwise be missed on the standard electrocardiogram.

Shivering following cardiac surgery: hemodynamic changes and reversal

The effects of shivering on hemodynamics and systemic oxygenation, as well as the effectiveness of therapeutic interventions in decreasing shivering and increasing mixed venous oxygen saturation, were studied. Thirty adult patients undergoing cardiopulmonary bypass with systemic hypothermia were observed for 1 1/2 to 5 hours postoperatively for signs of shivering associated with a simultaneous decrease in oxygen transport. Systemic and pulmonary hemodynamic measurements were made, blood temperature and mixed venous oxygen saturation were monitored via the pulmonary arterial catheter, and oxygen consumption and delivery were calculated. Shivering was graded by a single investigator on scale of 0 to 4, with 0 = no shivering and 4 = continuous violent muscle activity. Therapy was instituted when shivering reached grade 4 or when SvO2 decreased to less than two thirds of its value on arrival in the intensive care unit (ICU). Patients were randomly assigned to receive either morphine sulfate, 5 to 10 mg, or meperidine, 25 to 50 mg intravenously (IV), followed by the other narcotic if the initial drug failed to improve SvO2 or decrease shivering within ten minutes. The end-point for successful treatment was a return of SvO2 to within 5% to 10% of its value upon arrival in the ICU or a cessation of shivering that did not recur within 45 minutes. Twenty of the thirty patients shivered sufficiently to decrease SvO2 by more than one third of its initial value, thus requiring pharmacologic therapy. As shivering increased from a score of 0.8 +/- 1.1 to 3.4 +/- 0.9, SvO2 decreased from 74 +/- 6% to 57 +/- 12%.(ABSTRACT TRUNCATED AT 250 WORDS)

The pulse oximeter: a non-invasive monitor of oxygenation during thoracic surgery

The pulse oximeter continuously and non-invasively measures arterial saturation. The objective of the current study was to assess the value of this monitor during thoracic surgery with one-lung ventilation. A total of 108 pulse oximeter saturation readings (SaO2[O]) were compared with PaO2 and calculated saturation (SaO2[C]) values. Hypoxia (PaO2 less than 70 mmHg) always resulted in a SaO2 (O) value below 95%. For the detection of hypoxia, the pulse oximeter had a sensitivity of 100%, a specificity of 91% and a predictability of 70%. The correlation between SaO2(C) and SaO2(O) was good (r = 0.895). In the samples with a PaO2 below 100 mmHg the correlation between SaO2(C) and SaO2(O) was significantly better when the temperature was at least 36 degrees C (r = 0.956 vs. r = 0.706; p less than 0.005) or when the cardiac index was greater than 2.5 l/min/m2 (r = 0.896 vs r = 0.417; p less than 0.01).

Validation of quantitative intraoperative transesophageal echocardiography

Transesophageal echocardiography (TEE) is a new monitoring technique that images the heart and provides information on regional wall motion and left ventricular filling. However, despite its potential for inaccuracy due to its retrocardiac position and angulation, TEE has not been validated by another imaging technique. Using direct on-heart echocardiography (OHE) as a standard, the authors evaluated the ability of TEE to measure accurately left ventricular end-diastolic area (EDa), end-systolic area (ESa), and ejection fraction area (EFa). Ten patients with coronary artery disease without evidence of valvular dysfunction undergoing myocardial revascularization were studied. A Diasonics 3.5 MHz two-dimensional TEE probe was introduced into each patient's esophagus and positioned to obtain a view equivalent to the parasternal short-axis projection. A similar view was obtained by OHE using a sterilely prepared 3 MHz ATL probe placed on either the pericardium or epicardium. In each patient, immediately prior to and after pericardiotomy, both transesophageal and on-heart short-axis views at the level of the papillary muscles were obtained. Using a dedicated Diasonics computer echoanalyzer, EDa and ESa from four consecutive cardiac cycles were outlined with a light pen and averaged. EFa was calculated by the formula EFa = (EDa - ESa)/EDa. Seventeen comparable transesophageal and on-heart echocardiograms were obtained. ESa by TEE correlated well with ESa by OHE (15.13 +/- 9.62 cm2 vs. 14.92 +/- 10.53 cm2; r = 0.94). Similar results were obtained for EDa (27.75 +/- 9.88 cm2 vs. 30.40 +/- 13.99 cm2; r = 0.88) and EFa (0.49 +/- 0.17 vs. 0.54 +/- 0.13; r = 0.92). filling and ejection.

The effect of temperature, mean arterial pressure, and cardiopulmonary bypass flows on somatosensory evoked potential latency in man

Median nerve somatosensory evoked potentials were recorded in 21 patients undergoing cardiac surgical procedures utilizing cardiopulmonary bypass, in order to establish the effects of hypothermia, reductions in mean arterial pressure, and alterations in cardiopulmonary bypass flows on evoked potential latency. Induction and maintenance of anesthesia with fentanyl caused a significant prolongation of latency of the first cortical peak. Temperature changes were linearly correlated with changes in latency for peaks recorded from Erb's point (r = -0.843, p less than 0.01) and the contralateral cortex (r = 0.843, p less than 0.01). There was no significant effect of mean arterial pressure or cardiopulmonary bypass flow reductions on latencies under the conditions of this study. Our results emphasize the importance of monitoring peripheral and first cortical peak latencies in evaluating somatosensory evoked potentials. It is suggested that peak latency prolongations beyond those predicted by temperature alterations may be indicative of hypoperfusion.

The safety and efficacy of esmolol during myocardial revascularization

The safety and efficacy of esmolol during high-dose fentanyl anesthesia were studied in 37 patients undergoing coronary artery bypass grafting (CABG). The anesthetic management consisted of fentanyl 75 micrograms/kg, pancuronium 0.15 mg/kg, and O2. To assess the safety of esmolol, it was administered in a double-blind manner to 17 anesthetized patients prior to surgical incision. Infusion of the drug was increased in stepwise fashion to obtain administration rates between 100 and 300 micrograms X kg-1 X min-1. Esmolol produced small but significant increases in pulmonary capillary wedge pressure (PCWP) (8.3 +/- 1.7 to 13.2 +/- 2.0 mmHg) when compared with placebo (10.9 +/- 1.0 to 12.1 +/- 0.6 mmHg) (P less than 0.05). For the other studied parameters (heart rate, mean arterial pressure, central venous pressure, cardiac index, stroke index, left ventricular stroke work index, systemic vascular resistance, and peripheral vascular resistance), no significant differences were observed between esmolol and placebo. To evaluate the efficacy of esmolol, 20 patients were randomly assigned to an esmolol group (n = 11) or a placebo group (n = 9). The study medication was infused from 5 min before induction through initiation of cardiopulmonary bypass. Infusion of esmolol at 200 micrograms X kg-1 X min-1 prevented tachycardia in response to intubation. In the esmolol group the heart rate increased from 63.4 +/- 2.7 to 67.6 +/- 2.9 beats/min after intubation, while in the placebo group it increased from 61.4 +/- 4.3 to 72.4 +/- 3.4 beats/min (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Verapamil and myocardial preservation in patients undergoing coronary artery bypass surgery

The value of verapamil hydrochloride as a myocardial preservative when administered prior to or during periods of myocardial ischemia was studied in patients with normal preoperative cardiac function during elective coronary artery bypass grafting. Myocardial protection included systemic hypothermia (28 degrees C) and hypothermic hyperkalemic cardioplegia. Patients were randomly divided into four groups. Group 1 received intravenous administration of verapamil prior to aortic cross-clamping. Group 2 received intravenous verapamil plus verapamil in the cardioplegic solution. Group 3 received verapamil in the cardioplegic solution only. Group 4 was given no verapamil. Oxygen extraction during the reperfusion period was greatest in Group 4. However, the incidence of pacing was 50 to 78% in Groups 2 and 3, who were given verapamil in the cardioplegic solution. These groups also had a greater need for inotropic agents for discontinuation of cardiopulmonary bypass (CPB). This study indicates that verapamil may be a useful pretreatment prior to CPB and ischemia, but is not effective and may even be detrimental when administered during ischemic periods to patients with good myocardial function.

The role of isosorbide dinitrate in the treatment of perioperative hypertension

Intravenous nitroglycerin (NTG) has recently been found to be useful for the control of blood pressure during the perioperative period, especially during coronary artery bypass procedures. The objective of this study was to determine whether intravenous isosorbide dinitrate (ISDN) could play a similar role. Sixty-seven patients undergoing coronary artery bypass grafting at three centers were randomly assigned to an ISDN or NTG treatment group. The hemodynamic performance of all patients was assessed by the methods commonly used for cardiac patients (ECG, arterial line, thermodilution pulmonary artery catheter). One of the two nitrates was infused whenever the systolic blood pressure or the pulmonary capillary wedge pressure exceeded predetermined values. Treatment by either agent was considered successful if the elevated values returned to normal. NTG reduced the blood pressure in a higher percentage of hypertensive events. The rates of success were 84% for NTG vs 72% for ISDN in the prebypass phase, 93% vs 64% in the postbypass phase, and 71% vs 54% in the postoperative phase. Increased ISDN effectiveness may be attained with the use of a bolus administration before continuous infusion or with the use of a rapid rate of infusion.

High-dose hydromorphone (Dilaudid) for coronary artery bypass surgery

The hemodynamic effects of high-dose hydromorphone hydrochloride (H), 1.25 mg/kg, were investigated in 10 patients with normal ventricular function undergoing coronary artery bypass graft (CABG) surgery. One patient with unstable angina was excluded from the study because of hypotension and facial flushing after a 6-mg test dose of H. Nine patients showed no significant change in heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), left ventricular stroke work index (LVSWI), systemic vascular resistance (SVR), pulmonary capillary wedge pressure (PCWP), or coronary perfusion pressure (CPP) after H; central venous pressure (CVP) increased significantly (P less than 0.05). Loss of consciousness did not occur reliably after H. The addition of 50% N2O to H produced significant decreases in CI and LVSWI (P less than 0.05). Hemodynamic responses to tracheal intubation, skin incision, and sternotomy included depression of CI, elevation of SVR, and increased MAP (P less than 0.05). Vasodilators were required in eight patients before aortic cannulation and after extracorporeal circulation. Mean time to awakening was 7.6 hr after the full dose of H, and extubation was performed the morning after surgery (21 hr after H) according to our usual practice. We conclude that very large doses of H (equivalent in analgesic terms to 10 mg/kg of morphine sulfate) are well tolerated by most patients undergoing CABG surgery, but unconsciousness and complete suppression of sympathetic responses require supplementation of H with additional anesthetic agents or vasodilators.

Non-cardiac surgery in patients with prior myocardial revascularization

Patients who had undergone aorto-coronary bypass grafts (ACBG) were assessed for the incidence of cardiac complications in the postoperative period following subsequent non-cardiac surgery. One hundred and twenty-one patients had 13 complications (11 per cent). A significantly higher risk of cardiac complications (27 per cent) was found in patients undergoing non-cardiac procedures in the first month after ACBG. This remained higher (17 per cent) until the sixth month following ACBG. Significant factors which increased the risk of cardiac complications in the postoperative period included preoperative congestive heart failure (33 per cent), cardiac risk index score classification of III or IV (37 per cent), surgery on major vessels, and surgery necessitated because of a complication of the ACBG itself (17 per cent). No correlation was found between cardiac complication rates and recurrent angina, hypertension, the use of beta-blockers or digoxin, or anaesthetic technique. It is suggested that all but emergency surgery should be postponed in the first month following ACBG, and elective surgery be delayed for up to six months.

Nitroglycerin as an adjunct to hypothermic hyperkalemic cardioplegia

The efficacy of nitroglycerin as an adjunct to hyperkalemic hypothermic cardioplegia was assessed by measurement of changes in coronary vascular resistance. Thirty patients undergoing coronary artery bypass grafting were studied. During a 1000 ml infusion of cardioplegia, a bolus of 1 mg of nitroglycerin or control solution was injected while the infusion rate was kept constant. Measurement of aortic root pressure allowed calculation of coronary vascular resistance. There was a mean decrease of 21.2% in coronary vascular resistance after a bolus of 1 mg of nitroglycerin was injected in the study group (p less than .001, n = 15); there was no significant change in resistance in the control group. There was also no significant change in systemic vascular resistance in either group. A retrospective blind analysis of the anatomic angiographic features of the heart with a quantitative assessment of both coronary stenoses and coronary collaterals was made. There was no correlation between coronary scores and preinjection coronary vascular resistance. There was also no correlation between collateral scores and the change in coronary vascular resistance with nitroglycerin. These results suggest that nitroglycerin is an effective coronary vasodilator when used as an adjunct in hypothermic hyperkalemic cardioplegia and that baseline coronary vascular resistance or change in coronary vascular resistance with nitroglycerin cannot be predicted on the basis of current assessments of coronary angiograms.

Cardiovascular responses to verapamil during coronary artery bypass graft surgery

The cardiovascular effects of verapamil administration during coronary artery bypass graft surgery were studied in patients with normal left ventricular function. Anesthesia consisted of morphine, diazepam, and nitrous oxide. Before atrial cannulation for cardiopulmonary bypass, 16 patients received either verapamil (N = 8) 0.075 mg X kg-1 or an equal volume of its solvent (N = 8) administered intravenous over 1 min. Hemodynamic functions and serum verapamil levels were measured over the succeeding 10 min. Verapamil produced rapid reductions in systemic vascular resistance, systemic arterial blood pressure, and left ventricular stroke work index. The PR interval increased slightly and two of the patients who had a baseline PR interval of 200 msec developed a mild first degree heart block. Heart rate, cardiac index, pulmonary capillary wedge pressure, central venous pressure, and right ventricular stroke work index did not significantly change. No measured cardiovascular functions changed in the control group. Serum verapamil levels peaked at 346.4 +/- 143.5 ng X ml-1 0.5 min after drug administration and then rapidly declined. Both groups of patients tolerated surgery and the immediate postoperative recovery period without hemodynamic compromise. Verapamil can be safely administered before cardiopulmonary bypass in patient with good left ventricular function during narcotic-based anesthesia.

Hemodynamic interactions of verapamil and isoflurane

The hemodynamic interactions of verapamil and isoflurane were studied in eight dogs. Left ventricular function was analyzed using a right heart bypass preparation to permit rigid hemodynamic control. Hemodynamic studies were performed at 0.7, 1.05, and 1.40% isoflurane before and during the maintenance of two stable levels of verapamil, administered intravenously by combining a bolus dose (0.2 mg X kg-1) with an infusion (3.0 and 6.0 micrograms X kg-1 X min-1). Isoflurane produced a concentration-dependent depression of left ventricular function as indicated by dP/dt max, per cent systolic shortening, and left ventricular function curves. This depression was enhanced in a dose-plasma concentration-dependent manner by verapamil and was reversed by calcium chloride. Isoflurane alone and the combination of verapamil and isoflurane decreased systemic vascular resistance in a dose-dependent fashion that was antagonized partially by calcium chloride. Therefore, verapamil can enhance the hemodynamic effects of isoflurane in a dose-related manner that needs to be considered when both drugs are administered together.

Pretreatment with lidoflazine, a calcium-channel blocker. Useful adjunct to heterogeneous cold potassium cardioplegia

Ten mongrel dogs were studied to determine if pretreatment with lidoflazine would protect the canine myocardium during aortic cross-clamping when circumflex coronary artery occlusion limits the distribution of cold potassium cardioplegia. A canine right heart bypass preparation was used. Regional function was determined with a sonomicrometer. Twenty minutes before aortic cross-clamping, lidoflazine or solvent was administered in a random, blind fashion. A circumflex artery snare prevented the cardioplegic solution from entering the circumflex artery. A 100 minute arrest period with cardioplegic infusion every 20 minutes was followed by 45 minutes of reperfusion before global and regional function were reevaluated. In the group receiving solvent, postarrest function in the circumflex region recovered to only 30% of prearrest values (p less than 0.05), a marked functional deterioration. In the group protected by lidoflazine, function in the circumflex region returned to 90% of prearrest values (NS). Function in the left anterior descending (LAD) regions of both groups demonstrated full recovery after arrest. Global left ventricular function was well preserved in both groups and failed to reflect the damaged, malfunctioning region in the group receiving solvent. These findings suggest that pretreatment with lidoflazine can improve myocardial protection when delivery of cardioplegia is not homogeneous.

Myxoedema and open heart surgery: anaesthesia and intensive care unit experience

Myxoedema has been considered a major anaesthetic risk which could be increased by concurrent heart disease. Thyroid ablation with the production of myxoedema has, in the past, been used to control intractable angina. Eight ablated patients (Group I) and five patients with heart disease and incidental hypothyroidism (Group II) presented for open heart surgery. Management included diazepam-narcotic anaesthesia in generally reduced doses, careful monitoring and the use of digoxin, steroids and I-thyroxin given during or after operation. All patients survived. A number of the anaesthetic considerations and potential problems with myxoedema are discussed.

Esophageal lead for intraoperative electrocardiographic monitoring

The use and safety of the esophageal electrocardiogram for detection and diagnosis of dysrhythmias or ischemia during anesthesia was compared with the conventional electrocardiogram using leads II and V5 in 20 patients undergoing coronary artery bypass graft surgery. Using an intra-atrial electrocardiogram as the standard to provide detection and definitive diagnosis of dysrhythmias, the correct diagnosis from leads II and V5 was made in 53.8% and 42.3% of cases, respectively, whereas 100% of the dysrhythmias were properly diagnosed from the esophageal electrocardiogram (p less than 0.05). In two patients, the presence of a significant dysrhythmia was not detected using standard leads II and V5 alone. Large, distinct P waves, resulting from the proximity of the esophageal lead to the left atrium, clearly established the temporal relationship between atrial and ventricular depolarization. Posterior myocardial ischemia was diagnosed in one patient by ST-segment elevation in the esophageal electrocardiogram, whereas leads II and V5 did not demonstrate ischemic changes. No complications were encountered during the study. The esophageal lead is safe, simple to use, and provides valuable information for detection or diagnosis of dysrhythmias and myocardial ischemia during anesthesia.

Clinical evaluation of a new fiberoptic catheter oximeter during cardiac surgery

A new pulmonary arterial catheter (Opticath), containing the standard pulmonary artery catheter features plus two fiberoptic filaments to permit continuous measurement of oxygen saturation (SVO2) by a companion oximeter, was studied in 13 patients undergoing elective coronary bypass surgery. The study was designed to evaluate the accuracy of Opticath SVO2 measurements, to determine the incidence of catheter-related problems, and to correlate changes in SVO2 with hemodynamic changes. A good correlation was found between the SVO2 determined by the Opticath and that measured by American Optical and Radiometer Oximeters (r = 0.92 and 0.89 respectively; p less than 0.0001). There was a significant correlation between increases or decreases in values of SVO2 greater than or equal to 5% and corresponding changes in cardiac index, stroke index, and left ventricular stroke work index (p less than 0.001), and an 86% probability that SVO2 decrease greater than or equal to 5% reflected a significant decline in cardiac index.

Early diagnosis of myocardial ischemia using the pulmonary arterial catheter

Standard precordial electrocardiogram (ECG) leads detect transmural myocardial ischemia but are of limited use in detecting subendocardial ischemia. An early increase in the pulmonary capillary wedge pressure associated with abnormal wave forms has been noted in patients with coronary artery disease. This study sought to evaluate the usefulness of the pulmonary arterial catheter during coronary artery bypass graft surgery in detecting early myocardial ischemia. Forty patients with progressive angina pectoris undergoing elective myocardial revascularization were studied whenever one of the following signs of myocardial ischemia occurred: (a) ST-segment depression greater than 1 mm or, (b) wedge pressure tracing developed an abnormal AC wave greater than 15 torr, or V wave greater than 20 torr. Forty-five percent of the patients developed signs of myocardial ischemia. Three patients developed only ST-segment depression, five patients had ST-segment depression and an abnormal wedge pressure tracing, and 10 patients demonstrated only abnormal wedge pressure tracings. The abnormal wedge pressure tracings were associated with significant elevations of wedge pressures, central venous pressures, and triple indices. This study demonstrates that changes similar to those described in awake patients during cardiac catheterization occur under anesthesia. Abnormalities in the wedge pressure tracing may occur before the onset of ECG changes, indicating the development of myocardial ischemia. The changes in left ventricular compliance and subendocardial ischemia could not be predicted in advance by either the extent of coronary artery disease of degree of left ventricular dysfunction.

Cardiopulmonary resuscitation: physical stress on the rescuer

The physical stress on the rescuer performing cardiopulmonary resuscitation (CPR) was assessed utilizing the ECG, rate pressure product (RPP), and total body oxygen consumption (VO2). Six healthy physicians served as rescuers. Only a submaximal physical effort was required to perform good CPR, as demonstrated by the heart rate and VO2 changes. However, the effect was enough to generate a mean rescuer RPP approaching 20,000 with 2 of the rescuers well over 20,000. These data suggest that CPR might elicit ischemic symptoms in a rescuer with coronary artery disease.

Vasodilator therapy after cardiac surgery: a review of the efficacy and toxicity of nitroglycerin and nitroprusside

Eight-five patients who required vasodilator therapy in the postoperative period after cardiac surgery were studied to compare the haemodynamic effects of nitroglycerin and nitroprusside, to evaluate local and systemic toxicity, and to develop long-range dosage recommendations. Ninety-one per cent of the patients received the vasodilators for postoperative hypertension, while nine per cent had low output syndromes. Both drugs significantly decreased blood pressure and central venous pressure, and increased heart rate. Nitroglycerin decreased both right and left ventricular filling pressures more than nitroprusside. No local toxicity or methaemoglobinaemia was found with either drug. Elevated thiocyanate levels were detected in 44 per cent of the nitroprusside group; however, none of the patients developed progressive metabolic acidosis. For prolonged infusions we found that nitroprusside at 1 microgram.kg-1.min-1 and nitroglycerin at 0.5 microgram.kg-1.min-1 were without significant toxicity.

The spectrum of left main coronary artery disease: variables affecting patient selection, management, and death

A total of 178 patients having a diagnosis of left main coronary artery stenosis were divided into three groups as follows: surgical, Group I (n = 135 patients); operable medically treated, Group II (n = 21 patients); and inoperable, Group III (n = 22 patients). Groups 1 and 2 were comparable with regard to clinical profile, extent of anatomic coronary disease, and left ventricular function. Inoperable patients had a much higher incidence of prior myocardial infarction (especially anterior), more severe distal coronary disease, and markedly depressed left ventricular function. The hospital mortality rate for surgical patients was 4% (6/135). The late mortality rate, (median follow-up = 23.4 months) was 7% (9/135). For operable patients, the late mortality rate was 43% (9/21) at 28 months. In the inoperable group, the late death rate at 20 months was 59% (13/22). Actuarial survival at 24 months for the three groups was: 88%, 66%, and 42%, respectively. Of the nine patients who died in the operable group, two had less than 75% obstruction of the left main coronary artery and two had normal left ventricular wall motion. Although patients with higher grades of left main coronary artery stenosis and reduced left ventricular function are at greater risk, patients with less obstruction and good left ventricular function are also at risk and should have myocardial revascularization with some sense of urgency. The population of left main coronary artery stenosis is a heterogeneous one, and comparison of surgical versus medical therapy should exclude inoperable patients. The operative mortality rate has been greatly reduced in recent years (2% in the last 100 cases); this is attributed to careful monitoring in the critical prebypass period, aggressive pharmacologic treatment of increased preload, tachycardia, and hypertension, and improved aurgical technique, with emphasis on careful myocardial preservation. Adherence to these principles makes frequent use of the intra-aortic balloon either before or after revascularization unnecessary.