Milrinone is superior to epinephrine as treatment of myocardial depression due to ropivacaine in pigs.

PURPOSE: To determine whether milrinone is more effective than epinephrine in the resuscitation of ropivacaine induced cardiotoxicity in pigs. METHODS: Arterial, pulmonary, and LVdP/dt catheters were placed in 12 anesthetized, intubated and mechanically ventilated pigs. They received ropivacaine iv to cardiovascular toxicity: 50% decrease in LVdP/dt, cardiac output and mean arterial pressure (MAP). Group I (n=6) was treated with 100 microg x kg(-1) milrinone iv, and Group II (n=6) received 0.5 mg epinephrine iv. Resuscitation was successful if cardiac output returned to baseline, and MAP reached 80% of baseline. RESULTS: After ropivacaine, MAP decreased from 88 +/- 7 to 49 +/- 8 mmHg (P < 0.05), CO decreased from 2.8 +/- 0.4 to 1.2 +/- 0.2 L x min(-1) (P < .05), HR decreased from 103 +/- 8 to 74 +/- 7 beats x min (P < 0.05) and LVdp/dt decreased from 1,950 +/- 130 to 755 +/- 125 mmHg (P < 0.05). The LV EDP increased from 5 +/- 1 to 8 +/- 1 mmHg (P < 0.05) and SVR from 2,317 to 3,000 +/- 120 dynes x sec(-1) x cm(-5). Electrocardiogram changes included increases in the QTU interval and QRS duration. In all animals, milrinone restored MAP, CO, SV, HR, and dP/dt to baseline and no animal developed arrhythmias. In contrast, epinephrine produced severe hypertension and tachycardia. There was no improvement in CO or SV, and SVR increased. Epinephrine caused A-V dissociation and ventricular arrhythmias in three animals. CONCLUSION: Milrinone, was more successful than epinephrine in resuscitating anesthetized pigs from ropivacaine-induced cardiovascular toxicity.

Incidence of arrhythmias after thoracic surgery: thoracotomy versus video-assisted thoracoscopy.

PURPOSE: Atrial arrhythmias, especially supraventricular tachycardia (SVT) and atrial fibrillation, are common after thoracotomy and lung surgery. There are few existing data on the incidence of postoperative arrhythmias after video-assisted thoracoscopy (VAT). The purpose of the present investigation was to retrospectively determine the incidence of postoperative arrhythmias in patients who underwent VAT compared with those who underwent thoracotomy, and which factors are associated with an increased risk for arrhythmias in both groups. DESIGN: A retrospective investigation. SETTING: A metropolitan university hospital. PARTICIPANTS: The medical records of 124 patients who underwent thoracotomy and 81 patients who underwent VAT over a 2-year period were reviewed. MEASUREMENTS AND MAIN RESULTS: There was a 17% incidence of atrial arrhythmias after thoracotomy and 10% after VAT, but the difference was not statistically significant. In both groups, atrial fibrillation was the most common atrial arrhythmia. CONCLUSION: Patients receiving digoxin were at higher risk for postoperative arrhythmias. Patients older than 65 years were at risk for arrhythmias after thoracotomy and patients older than 80 years were at risk for arrhythmias after VAT. Patients who had postoperative arrhythmias had prolonged hospital stays compared with patients who did not have arrhythmias.

Intraoperative transesophageal echocardiography during noncardiac surgery.

OBJECTIVE: To investigate the use and impact of transesophageal echocardiography (TEE) during noncardiac surgery. DESIGN: Retrospective study. SETTING: A university teaching hospital. PARTICIPANTS AND INTERVENTIONS: The medical records and the videotapes of 123 intraoperative TEE examinations were reviewed. MEASUREMENTS AND MAIN RESULTS: TEE was used for non-consultative indications in 68 patients and in consultation in 55 patients. Information that would not have been detected intraoperatively by other means included intracardiac defects, valvular and aortic pathology, the presence or absence of ventricular dysfunction or intracardiac thrombi, and embolization during surgery. Findings during the initial TEE examination and the TEE evaluation of intraoperative events resulted in a major impact on patient management in 15% of patients. The majority of patients in whom TEE had any impact (the sum of major, minor, and limited impact groups) were classified as American Society of Anesthesiologists (ASA) class 3 or 4. Patients in whom TEE had any impact were significantly older than patients in whom TEE had no impact (66.5 +/- 13.4 years v 58.1 +/- 16.2 years; p < 0.05). No patient experienced a complication related to intraoperative TEE. CONCLUSION: It appears that TEE in patients undergoing noncardiac surgery is efficacious in rapidly disclosing new findings and information during periods of hemodynamic instability. It may have a significant impact on intraoperative patient management and may be beneficial in patients older than 66 years of age.

Cardiovascular consequences of the concomitant administration of nifedipine and magnesium sulfate in pigs.

There is concern regarding the interaction of magnesium sulfate and nifedipine used concomitantly in obstetrical patients, because both are calcium channel antagonists and may induce myocardial depression as well as peripheral vasodilatation. The objective of this study was to determine the hemodynamic consequences of concomitant administration of nifedipine and magnesium sulfate in anesthetized pigs. Twelve pigs were anesthetized with sodium pentobarbital, intubated mechanically ventilated. Following placement of invasive monitors, baseline hemodynamic measurements were made. Animals were randomized to one of two groups. Group I received nifedipine first, and then magnesium sulfate. Group II received magnesium sulfate first, and then nifedipine. Hemodynamic measurements were recorded. Hypotension was treated with calcium chloride, ephedrine and phenylephrine. Nifedipine alone (Group I) decreased peripheral vascular resistance and mean arterial pressure (MAP) (P<0.05). Magnesium sulfate alone in group II decreased the first derivative of left ventricular pressure (LVdP/dt) and increased left ventricular end-diastolic pressure (LVEDP) (P<0.05). Magnesium sulfate also decreased peripheral vascular resistance and MAP The concomitant administration of nifedipine and magnesium sulfate in both groups I and 11 led to a further decrease in myocardial contractility, as evidenced by a decrease in LVdP/dt and increase in LVEDP (P<0.05). Treatment with calcium chloride or ephedrine was only partially successful in improving myocardial contractility. Phenylephrine increased peripheral vascular resistance and MAP, but did not improve myocardial function. In conclusion, the depressive effects of nifedipine and magnesium sulfate on the cardiovascular system are potentiated when administered concomitantly.

Role of zatebradine and propranolol in attenuation of tachycardia produced by dobutamine in pigs.

BACKGROUND: Zatebradine is a new specific bradycardiac agent that selectively slows the depolarization in the pacemaker cells of the sinoatrial node. The purpose of our investigation was to determine whether the tachycardia induced by dobutamine can be attenuated by the administration of zatebradine. The results were compared with those produced by propranolol, which is used in the treatment of sinus tachycardia. METHODS: Twelve pigs were anesthetized with sodium pentobarbital, intubated, and ventilated. After baseline hemodynamic measurements were obtained, dobutamine was administered until the heart rate reached 25% above baseline. Animals were randomized to one of two groups. Group I received zatebradine, 0.5 mg/kg i.v., and Group II received propranolol, 0.5 mg/kg i.v. RESULTS: Dobutamine 10 micrograms.kg-1.min-1 increased the heart rate (FIR) by 25%, and increased mean arterial blood pressure (MAP) left ventricular (LV) dp/dt, and cardiac output (CO) (P < 0.05). Zatebradine decreased the HR to baseline (P < 0.05) without affecting left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LV dP/dt, or CO. Stroke volume (SV) increased significantly (P < 0.05). Propranolol also reduced HR to baseline, but decreased LV dP/dt, LVSP, CO, and SV (P < 0.05). CONCLUSION: Zatebradine effectively attenuates the tachycardia caused by dobutamine in anesthetized pigs, without reducing cardiac performance.

Incidence of malposition of polyvinylchloride and red rubber left-sided double-lumen tubes and clinical sequelae.

Currently, fiberoptic bronchoscopy (FB) is recommended for correct positioning of double-lumen endobronchial tubes (DLTs) because of the high incidence of malpositions not appreciated by clinical signs. The aims of this study were to assess whether clinical signs allow accurate confirmation of adequate positioning with left red rubber (RR) or polyvinyl-chloride (PVC) double-lumen tubes and to compare the incidence of malpositions between the two tubes. Another goal was to assess whether these malpositions, not appreciated by clinical assessment, adversely affected outcome. Twenty-one adult patients scheduled for elective thoracic surgery were randomly assigned to the RR (11 patients) or PVC group (10 patients). After endobronchial intubation, the position of the tubes was adjusted until clinically satisfactory lung separation had been achieved. A single investigator performed all the FB assessments were performed in the supine (SUP) and lateral positions. The anesthesiologists responsible for the clinical evaluation were "blinded" to the bronchoscopic findings. While in the SUP position, the tube was "too deep" to permit visualization of the carina during tracheal bronchoscopy in 5 patients (2 RR, 3 PVC). In 17 of 21 (10 RR, 7 PVC), the bronchial cuff could not be visualized, although in 1 patient (RR group), the cuff was overinflated and bulged out to partially obstruct the right main bronchus orifice. Bronchial bronchoscopy showed 4 of 11 patients in the RR group in whom the left upper lobe orifice was occluded compared with 1 only in the PVC group.(ABSTRACT TRUNCATED AT 250 WORDS)

Esmolol and intraoperative myocardial ischemia: a double-blind study.

Forty patients scheduled to undergo elective myocardial revascularization were included in a randomized, double-blind, placebo-controlled study to evaluate any influence of esmolol on the incidence of myocardial ischemia. Calibrated recordings of ECG leads II and V5 were continuously monitored with the QMED Monitor One TC (Qmed Inc, Clark, NJ) from the time of arrival in the operating room holding area through the induction of anesthesia, using a high-dose opioid technique, and until the initiation of cardiopulmonary bypass. One group received a bolus of esmolol, 1.0 mg/kg, followed by a continuous infusion of 100 micrograms/kg/min. The other group received a bolus and infusion of saline placebo of equal volume. The incidence of myocardial ischemia was not significantly different between the groups on arrival in the holding area, or at any study point. Heart rate, mean arterial pressure, and the number of patients developing myocardial ischemia during the course of the study also did not differ significantly between the groups. There were significant decreases in heart rate and mean arterial pressure compared with the awake baseline values in both groups during multiple study points. It is concluded that esmolol was ineffective at treating preexisting or new-onset myocardial ischemia at this dosage in this clinical setting.

Arrhythmogenic potential of dopexamine hydrochloride during halothane anaesthesia in dogs.

Dopexamine hydrochloride (Dopacard) is the novel synthetic catecholamine designed for use in the acute management of a low cardiac output status. In addition to dopaminergic receptor stimulation, dopexamine hydrochloride is a potent beta 2 adrenoceptor agonist with negligible direct beta 1 and no alpha adrenergic effect. The objective of this study was to compare the arrhythmogenic effects of dopexamine hydrochloride and dopamine in dogs anaesthetized with halothane (1.2 MAC). The starting dose for dopexamine hydrochloride was 3.5 micrograms.kg-1.min-1 and for dopamine was 5 micrograms.kg-1.min-1. Concentrations of the drugs were increased until four or more premature ventricular contractions within 15 seconds were produced. All dogs developed ventricular tachycardia when dopamine was administered in concentrations ranging between 18-20 micrograms.kg-1.min-1. Unlike dopamine, dopexamine hydrochloride even at concentrations as high as 50 micrograms.kg-1.min-1 did not induce any atrial or ventricular ectopic beats. Lack of beta 1 and alpha adrenergic agonist effects is a likely explanation for low arrhythmogenicity of dopexamine hydrochloride. Both drugs increase cardiac output; dopexamine hydrochloride primarily by a dose-related increase in heart rate and increased afterload. At the maximal concentration dopexamine hydrochloride increased heart rate from 114 to 150 beat.min-1, mean arterial pressure decreased from 81 mmHg to 45 mmHg and SVR decreased from 2418 to 962 dyne.sec-1cm-5. Myocardial contractility increased only moderately, as evaluated by dP/dt, which increased from 1290 to 1696 mmHg.sec-1. Dopamine had a more marked inotropic effect: the dP/dt increased, at the maximal concentration, from 1480 to 2570 mmHg.sec-1.(ABSTRACT TRUNCATED AT 250 WORDS)