Does transesophageal echocardiography improve postoperative outcome in patients undergoing coronary artery bypass surgery?

The incidence and characteristics of ischemic episodes as detected by transesophageal echocardiography (TEE) and their relationship to postoperative myocardial infarction (MI) and adverse clinical outcome were studied in patients undergoing coronary artery bypass grafting (CABG). Seventeen of 50 patients had 21 TEE-defined ischemic episodes: 4 patients (8%) had 4 ischemic episodes in the pre-cardiopulmonary bypass (CPB) period, and 15 patients (30%) had 17 ischemic episodes in the post-CPB period, whereas 19 patients had 20 ECG ischemic episodes: 3 patients (6%) had 3 ischemic episodes in the pre-CPB period and 17 (34%) had 17 ischemic episodes in the post-CPB period. In 14 patients, ischemic episodes were detected by both TEE and ECG. Clinicians were made aware of the TEE data and appropriate treatments were undertaken during ischemic episodes: of the 15 patients with TEE-defined post-CPB ischemia, 4 had an additional saphenous vein graft placed, 8 had an intra-aortic balloon pump (IABP) inserted, 3 were given sublingual nifedipine, and 13 received nitroglycerin. These treatments resulted in improvement in regional wall motion abnormalities (RWMA) by the end of surgery in 11 of the 15 patients (73%), including the 4 with postoperative MI and 2 who died with cardiogenic shock. The authors conclude that: (1) significantly more patients had TEE-defined ischemic episodes in the post-CPB period (30%) than in the pre-CPB period (8%); (2) a poor graft and/or inadequate myocardial protection were strongly suggestive of post-CPB ischemia, which was significantly related to adverse outcome; and (3) TEE was a useful tool enabling detection of problem areas at an early stage and timely and appropriate treatment to support and sustain patients.

Presynaptic interaction between vagal and sympathetic innervation in the heart: modulation of acetylcholine and noradrenaline release.

It is generally accepted that there is a functional antagonism between the sympathetic and parasympathetic (vagal) effects on the heart. In this study guinea-pig right atria loaded either with [3H]noradrenaline or [3H]choline were used and the release of [3H]noradrenaline or [3H]acetylcholine in response to field stimulation was measured under conditions when the negative feedback modulation was excluded. Strong evidence was obtained for a one-sided interaction between the sympathetic and vagal nerves at the level of the prejunctional axon terminals that send the final chemical message to the heart muscle affecting heart rate and force. Acetylcholine released from the vagal nerve inhibited its own release and also decreased the release of noradrenaline from the sympathetic axon terminals through muscarinic receptor stimulation. But muscarinic receptors located on cholinergic axon terminals are different from those present on the noradrenergic axon terminals. There is a significant difference in the dissociation constants (Kd) of different antimuscarinic drugs: The Kd values of pancuronium on vagal and sympathetic axon terminals were 5.68 +/- 0.41 and 7.20 +/- 0.25, respectively. By contrast, noradrenaline released from the sympathetic nerves or exogenous noradrenaline were not able to modulate the release of acetylcholine from the cholinergic axon terminals even under condition when the negative feedback modulation of acetylcholine release was excluded. These findings indicate that vagal axon terminals are not equipped with alpha 2- or alpha 1-adrenoceptors. However, noradrenaline released from the sympathetic axon terminals was able to inhibit its own release via alpha 2-adrenoceptor stimulation.

New applications of two-dimensional transesophageal echocardiography in cardiac surgery.

This article describes new applications of two-dimensional transesophageal echocardiography (2D-TEE), including (1) detection of pleural fluid (PF) and atelectasis (AT), and (2) evaluation of various cannulation techniques. The left and right pleural spaces were visualized by rotating the probe counterclockwise and clockwise, respectively, from the four-chamber view. PF was depicted as a crescent-shaped echo-free space, enclosed by the lung and posterior chest wall on both sides. AT was often accompanied by PF and was depicted as a less echogenic area in the lung parenchyma. During removal of PF, the echo-free space gradually decreased in size to the point of disappearing completely, while the lung parenchyma expanded and became more echogenic. TEE was advantageous in detecting PF and AT located in the most dorsal parts of the pleural space and lung parenchyma. The aorta acted as an acoustic window on the left side. TEE was found useful in evaluating the cannulae position of the intraaortic balloon pump (IABP) and ventricular assist device (VAD), and femoral cannulae for cardiopulmonary bypass (CPB). During use of the IABP, the chamber and shaft were visualized clearly and both malposition of the catheter tip and malfunction of the balloon were easily detected. For VAD, TEE readily showed the collapse of the ventricular cavity due to excessive drainage of blood from the left ventricle, as well as the favorable result of immediate reduction of flow rate. For femorofemoral extracorporeal bypass, TEE detected improper position of the venous cannula. These new applications of TEE can be performed with minimal manipulation of the probe, enabling early detection of the problems and initiating timely and appropriate therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

The pre- and postjunctional components of the neuromuscular effect of antibiotics.

The relative contributions of the pre- and postsynaptic components of the myoneural blocking effect of different antibiotics were studied using: (a) a radio-active method that measures selectively the Ca(2+)-dependent, stimulation evoked, quantally released, (3)H-acetylcholine ((3)H-ACh) from the mouse in vitro phrenic nerve-hemidiaphragm preparation without cholinesterase inhibition; (b) measurement of the force of contraction of the indirectly or directly stimulated muscle. The antibiotics studied (neomycin, polymyxin B and lincomycin), reduced the release of (3)H-ACh evoked by stimulation (18 trains of 40 shocks at 50 Hz) in a concentration dependent manner. While the inhibitory effect of neomycin was inversely related to [Ca(2+)](o), that of lincomycin was moderately and that of polymyxin B was not affected by increasing [Ca(2+)](o) from 0.75 to 5.0 mM. Similarly, the d-tubocurarine (d-Tc)-induced inhibition of the release of (3)H-ACh was independent of [Ca(2+)](o). The K-channel blocking agent, 4-aminopyridine (4-AP), enhanced the release of ACh in a concentration dependent manner and prevented the neuromuscular effect of neomycin. However, the neuromuscular effect of polymyxin B and of lincomycin was not affected by 4-AP. Atropine, enhanced the release of (3)H-ACh. Antibiotics, however, were still able to reduce the release of ACh when the negative muscarinic feedback mechanism of ACh release was eliminated by atropine. Our findings indicate that the antibiotics studied possess both pre- and postsynaptic effects. Presynaptically they reduce the evoked release of ACh; postsynaptically they inhibit muscle contractility. The rank order of presynaptic action is neomycin >polymyxin B >lincomycin.

The anatomical location of the transesophageal echocardiographic transducer during a short-axis view of the left ventricle.

This study was performed to clarify the location of a transesophageal echocardiographic (TEE) transducer when obtaining the short-axis view of the left ventricle (S-LV). The depth of the probe tip from the incisors when obtaining a S-LV, the relationship to the diaphragm, and the location of the cardia of the stomach using a gastroscope attached to the TEE probe were measured in 24 patients undergoing coronary artery bypass grafting. The location of the transducer relative to the cardia and diaphragm was determined. The study demonstrated that when obtaining a S-LV, the transducer was in the stomach in 72.7%, at the cardia in 13.6%, and in the esophagus in 13.6% of the patients. The predominantly intragastric position of the transducer suggests that gastric diseases should be included as contraindications to TEE. When the probe was advanced about 40 cm from the incisors, some resistance was often encountered by the TEE operator at about the level of the diaphragm. Careful manipulation is mandatory to avoid tissue damage by the probe. Visualization of the S-LV can be disturbed by gas in the stomach. This is a specific problem in anesthetized patients because gas is often pushed into the stomach at the time of induction.

Hemodynamic effects of high-frequency jet ventilation in dogs with acute right coronary arterial ligation and pulmonary arterial banding.

The hemodynamic effects of high-frequency jet ventilation (HFJV), synchronized with diastole, and intermittent positive-pressure ventilation (IPPV) were studied in 10 dogs with acute right-sided myocardial ischemia and elevated right ventricular pressure. Myocardial ischemia was produced by ligation of the proximal right coronary artery (RCA), then the right ventricular pressure was elevated to facilitate the ischemia by banding the main pulmonary artery. Before and 1, 2, 3, and 5 hr after the RCA ligation, cardiorespiratory variables for each ventilatory mode and creatine phosphokinase MB isoenzyme (CPK-MB) were measured. During HFJV compared with IPPV: there were significant increases in stroke index and left ventricular stroke work index at all ischemic periods, and decreases in peak and mean airway pressures and pulmonary vascular resistance at all ischemic periods, and in the product of systolic right ventricular pressure and heart rate at 2 hr, 3 hr, and 5 hr. The difference in mean airway pressure between IPPV and HFJV correlated significantly with those in cardiac index and stroke index (r = 0.575 and 0.779, respectively). CPK-MB was significantly greater at 3 hr and 5 hr than that before RCA ligation. These findings suggest that HFJV synchronized with diastole offers hemodynamic advantages over IPPV to ischemic right ventricle with constricted pulmonary artery, mainly due to lowering the mean airway pressure.

Neuromuscular and cardiovascular effects of pipecuronium.

Pipecuronium bromide (Arduan) is a bisquaternary, steroid-type neuromuscular blocking agent in clinical use in Eastern Europe. Before its introduction into clinical practice in the USA, in the first phase of this study the neuromuscular potency of pipecuronium was determined under "balanced" and enflurance anaesthesia by the cumulative log dose-response method in 30 patients each. In the second phase the intubation and onset times, clinical duration of the first and repeated doses, spontaneous recovery index, reversibility of its residual neuromuscular effect by an anticholinesterase and its effect on heart rate and blood pressure was compared with the same variables observed in patients, anaesthetized with identical techniques but who had received vecuronium or pancuronium. The neuromuscular potency of pipecuronium was greater under enflurane (ED95 = 23.6 +/- 1.1 micrograms.kg-1 (mean +/- SEM)] than under balanced (ED95 = 35.1 +/- 17 micrograms.kg-1) anaesthesia. Pipecuronium was more potent than vecuronium under both balanced (ED95 = 45.8 micrograms.kg-1) and enflurane anaesthesia (ED95 = 27.4 micrograms.kg-1). Following the administration of 2 x ED95 doses there were no clinically significant differences in the intubation or onset times of pipecuronium, vecuronium and pancuronium. Under balanced anaesthesia the clinical duration of 2 x ED95 dose of pipecuronium (110.5 +/- 0.3 min) or pancuronium (115.8 +/- 8.1 min) were similar and about three times longer than that of vecuronium (36.3 +/- 2.1 min). The recovery indices of pipecuronium (44.5 +/- 8.2 min) and pancuronium (41.3 +/- 4.2 min) were also similar and about three times longer than that of vecuronium (14.3 +/- 1.4 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative assessment of pulmonary vein flow.

This study was undertaken to assess the suitability for intraoperative pulmonary vein flow measurements in 15 patients undergoing coronary artery bypass grafting. Using two-dimensional color Doppler transesophageal echocardiography, all four pulmonary veins--right upper and lower and left upper and lower pulmonary veins were easily visualized. Pulmonary vein flow was pulsatile. J wave occurred in the ventricular systole with relaxation of the left atrium and K wave in the ventricular diastole with relaxation of the left ventricle. There were differences in suitability for flow measurements among four pulmonary veins: (1) consistent visualization; (2) stable visualization throughout measurement; (3) minimal angle between ultrasonic beam and pulmonary vein course; and (4) minimal shift of sampling volume during measurement. The left pulmonary veins were suitable for flow velocity measurement by transesophageal echocardiography. The left lower pulmonary vein was stable for visualization once it was visualized although the angle was occasionally large. The left upper pulmonary vein was consistently visualized although the angle was occasionally large. On the other hand, the right pulmonary veins were unsuitable for flow measurement. Since sampling volume shifted in the direction of the long axis by the average of 5 to 6 mm during cardiac cycle, it should be positioned inside of the pulmonary vein at about 5 mm from the orifice of the left atrium.

Diagnosis of myocardial ischemia by the pressure-rate quotient and diastolic time interval during coronary artery bypass surgery.

Diagnosis of intraoperative myocardial ischemia by the rate-pressure product (RPP), pressure-rate quotient (PRQ), and diastolic time interval (DTI) was studied in 13 patients undergoing coronary artery bypass grafting (CABG) with fentanyl, vecuronium/pancuronium, and enflurane anesthesia. Criteria for ischemia were 1 mm of ST segment elevation or depression or T wave inversion on the ECG. RPP was calculated by multiplying the systolic arterial pressure (SAP) times the heart rate (HR); PRQ was determined by dividing the mean arterial pressure (MAP) by the HR; and DTI was defined as the interval from the closure of the aortic valve on M-mode transesophageal echocardiography to the onset of the QRS complex on the ECG. Six of 13 patients experienced episodes of ischemia (a total of 32 episodes out of 134 measurements). RPP of 12,000 was not found to correlate with myocardial ischemia (P greater than 0.05), whereas PRQ of less than 1.0 or DTI of less than 400 ms was associated with myocardial ischemia (P less than 0.005). In this preliminary study, it is concluded that both the PRQ and DTI are indicators of myocardial ischemia; it is also suggested that ischemia may be prevented by maintaining (1) DTI over 400 ms (HR less than 75 beats per minute), and (2) PRQ greater than 1.0 (MAP greater than HR).

Hemodynamic effects of high-frequency jet ventilation in dogs with a chronically banded pulmonary artery.

Two to seven weeks after banding the main pulmonary artery, the hemodynamic effects of high-frequency jet ventilation (HFJV) and conventional mechanical ventilation (CMV) were studied in dogs with and without PEEP. In comparison with CMV, HFJV significantly increased cardiac index, stroke index (SI), left ventricular stroke work index, and oxygen delivery index, and decreased pulmonary vascular resistance index both with and without PEEP; however, there were significant decreases in PaO2 and increases in intrapulmonary physiologic shunt ratio in HFJV without PEEP. SI without PEEP was significantly greater with HFJV when the peak airway pressure was synchronized with the diastole in pulmonary arterial pressure (PAP) than with CMV and with HFJV synchronized with the systole in PAP. These findings suggest that HFJV has hemodynamic advantages over CMV in dogs with chronically banded pulmonary artery and dilated right ventricle.

In vitro comparison of the neuromuscular antinicotinic and intestinal antimuscarinic effects of different nondepolarizing muscle relaxants.

The postsynaptic antimuscarinic properties of different nondepolarizing muscle relaxants were compared with their postsynaptic antinicotinic effect. d-Tubocurarine, pipecuronium and vecuronium were the most selective antagonists on postsynaptic nicotinic receptors. Gallamine, diadonium and Duador (RGH-4201) had relatively greater effect on postsynaptic muscarinic receptors. Therefore, much less side effect is expected to occur when pipecuronium, d-tubocurarine or vecuronium are used.

Epidural analgesia for labor and delivery in a patient with von Willebrand's disease.

Patients with histories of bleeding disorders may still benefit from regional anesthetic techniques. The decision to perform the block should be individualized, based on coagulation tests. The authors describe a patient with von Willebrand's disease in whom pregnancy itself improved factor VIII activity, enabling performance of an epidural block for labor and delivery.

Presynaptic effect of muscle relaxants on the release of 3H-norepinephrine controlled by endogenous acetylcholine in guinea pig atrium.

The influence of nondepolarizing muscle relaxants (MR) on the resting and electrically evoked release of tritiated norepinephrine (3H-NE) was investigated, in the absence and presence of 10(-4) mol/l cocaine, in the in vitro right atrium preparation of guinea pigs (g.p.) preloaded with 3H-NE. In the absence of MR both resting and stimulated 3H and 3H-NE release remained relatively constant throughout the experiment and the ratios of the evoked release of 3H during consecutive stimulation periods (i.e. S2/S1, S3/S2) were close to unity. None of the MR had any effect on resting 3H release. Atropine (3 x 10(-7) mol/l), gallamine (7 x 10(-5) mol/l), and pancuronium (2 x 10(-6) mol/l), but not d-tubocurarine (5 x 10(-6) mol/l) significantly increased stimulated release of 3H-NE. The effect of MR on resting or evoked release of 3H-NE was not influenced by 10(-4) mol/l cocaine. In the presence of atropine gallamine and pancuronium did not affect the release of 3H-NE. This finding indicates that the effect of MR was mediated via presynaptic muscarinic receptors. Muscle relaxants and atropine inhibited these receptors and removed the tonic inhibitory effect of acetylcholine (ACh) released from the parasympathetic nerve endings on the release of NE from the sympathetic nerve. This was substantiated by the finding that in the present of cholinesterase inhibition, when the effect of endogenous ACh was amplified and thereby the cholinergic tone was dominant, the total release of 3H-NE evoked by stimulation was much lower and muscle relaxants and atropine were much more effective to enhance 3H-NE release. Gallamine and pancuronium also increased the force of contraction of the electrically stimulated atria. These findings indicate that the acceleration of the heart rate observed with gallamine and pancuronium in anesthetized man is due to increased release from, and not the inhibition of reuptake of NE by the sympathetic nerve endings of the right atrium.

Heterogeneity of presynaptic muscarinic receptors involved in modulation of transmitter release.

In order to extend the characterization of muscarinic receptors at presynaptic sites their inhibitory effect on the stimulation-evoked release of [3H]noradrenaline and [3H]acetylcholine from different axon terminals was studied and the dissociation constants and potencies of different antagonists were estimated, in guinea-pig and rat. While oxotremorine reduced the release of [3H]acetylcholine and [3H]-noradrenaline in a concentration-dependent manner from different release sites (Auerbach plexus, noradrenergic neurons in the right atrium, cerebral cortex), McN-A 343, an M1 receptor agonist, enhanced their release evoked by field stimulation. When the inhibitory effect of oxotremorine on transmitter release was studied, pancuronium, pirenzepine and atropine were competitive antagonists of presynaptic muscarinic receptors located on the noradrenergic axon terminals of the atrium. While atropine and pirenzepine inhibited the muscarinic receptors of cholinergic axon terminals in the Auerbach plexus, pancuronium and gallamine had a very low affinity. Significant differences were found in the affinity constants of antagonists for muscarinic receptors located in the cholinergic axon terminals of Auerbach plexus and cerebral cortex, and noradrenergic axon terminals of the atrium. While atropine and pirenzepine exerted similar effects on these presynaptic sites, pancuronium, gallamine and (11-(2-[diethylamino)-methyl)-1-piperidinyl)acetyl)-5, 11-dihydro-6(1-pyrido(2,3-b)(1,4)-benzodiazepin-6-on) were much more effective on muscarinic receptors controlling acetylcholine release from the cerebral cortex and noradrenaline release from the heart. There was more than 100-fold (2.0 pA2 units) difference in affinities of these antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)