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.