Prolongation of the QT-interval during induction of anesthesia in patients with coronary artery disease

During induction of anesthesia in 60 patients undergoing coronary artery bypass grafting (CABG), we measured the QT-interval (QTI) in the ECG, heart rate (HR) and mean arterial pressure (MAP). Based on the HR, we corrected the QT-interval (QTcI). Prior to induction, six patients (10%) already had abnormal prolongation of QTcI (> or = 440 ms). After injection of fentanyl and vecuronium, the QTcI increased significantly (P < 0.01); to a far lesser extent after injection of hypnotics (i.e. etomidate, midazolam or propofol). Orotracheal intubation caused significant shortening of QTcI (P < 0.01). HR decreased markedly after injection of fentanyl. MAP decreased, however, only after injection of hypnotics. In the immediate post intubation period, HR and MAP increased significantly. The various hypnotics produced no significant difference in HR and QTcI at any measurement point. MAP changed only after injection of hypnotics. The decrease of HR and MAP during induction of anesthesia is thought to result from a corresponding reduction of adrenosympathetic stimulation. We believe that QTcI is similarly influenced.

[ST segment changes in the ECG. Anesthesia induction with propofol, etomidate or midazolam in patients with coronary heart disease]

Induction of anaesthesia with propofol and fentanyl can lead to marked reductions in mean arterial pressure (MAP) and heart rate (HR). Thus, the application of propofol in patients with severely reduced coronary artery perfusion is controversial. METHODS. The study group consisted of 60 patients undergoing coronary artery bypass grafting (CABG). Anaesthesia was induced over 30 s with propofol (P 1.5 mg/kg), etomidate (E 0.3 mg/kg), or midazolam (M 0.15 mg/kg) following a bolus dose of fentanyl (5 micrograms/kg). Vecuronium was used as a muscle relaxant. During induction we continuously measured MAP and HR and recorded the occurrence of myocardial ischaemia using an automatic ST-segment analyser (Marquette 7010). ST-segment deviations of more than 1 mm in leads II and V5 were interpreted as significant signs of myocardial ischaemia. RESULTS. All groups showed reductions in MAP and HR on induction that were marked in the P group. Intubation caused elevation of MAP and HR to pre-induction levels (HR: all groups) or slightly above (MAP: E, M). Four patients in the P group and 3 in each other group showed significant ST-segment deviation prior to induction. In the P group these deviations disappeared in 2 patients after injection while they remained unchanged in the M group. In the E group injection had no effect on the ischaemic ECG changes but produced another case of significant ST-segment deviation. Laryngoscopy and intubation produced no further significant ST-segment deviation in either group. DISCUSSION. Induction is a critical phase of anaesthesia, especially in patients with limited coronary reserve. Induction agents should alleviate the stress response while causing minimal haemodynamic changes. Despite marked reductions in MAP in the P group, the number of patients with ischaemic ECG changes was cut by half. Their number was unchanged or even raised in the other groups. After application of P, with an alleged reduction of coronary perfusion, a compensational reduction in myocardial oxygen consumption may occur.

[Automated, continuous ST segment analysis in the ECG as a monitor of myocardial ischemia during aortocoronary bypass surgery]

Patients with coronary artery disease (CAD) who are subjected to cardiac and major noncardiac surgical procedures have a high incidence of perioperative myocardial ischemia. Earlier studies in patients undergoing coronary artery bypass graft surgery (CABG) indicated the frequency of postoperative myocardial infarction to be directly proportional to the incidence and severity of pre-bypass myocardial ischemia.

METHODS

We investigated the incidence of pre-bypass ischemia in 50 patients undergoing elective CABG using an automated ST segment monitoring system (Marquette 7010). Analyzing leads I, II, and V5, this device measures ST segment deviations 60 ms after the J-point. Occurrence of myocardial ischemia was defined as follows: new ST segment deviations larger than 1 mm = 0.1 mV that lasted for more than at least 10 consecutive heartbeats.

RESULTS

In 19 out of 50 patients (38%) we found 96 episodes of myocardial ischemia in the pre-bypass period; 47% of all ischemic episodes were associated with significant hemodynamic changes, e.g., tachycardia, hypertension, or hypotension. The incidence of ischemia was different between population sub-groups: patients with a previous infarction had a lower incidence of ischemia (35%) than patients without infarction (44%). Patients with preoperative left ventricular end diastolic pressure (LVEDP) less than 15 mm Hg had a lower incidence of ischemia (29%) than patients with LVEDP greater than 15 mm Hg (50%). Patients treated preoperatively with beta-blockers showed a significantly lower incidence of ischemia (9%) when compared to untreated patients (46%, p less than 0.05). No difference was found between patients with or without unstable angina pectoris or between patients of NYHA classes II, III, or IV. Postoperative myocardial infarction occurred in 2 patients, both with evidence of pre-bypass myocardial ischemia.

CONCLUSION

Our study confirms that automated ST segment analysis is able to detect myocardial ischemia similarly to that documented in previous studies using conventional ECG lead analysis.

[Cardiac adverse effects following an intravenous injection of pirenzepine are an expression of deficient receptor sensitivity]

Under the aspect of life-threatening pneumonias in long-term ventilated patients receiving ant-acids or H2-antagonists the prophylaxis of stress ulcer with pirenzepine gains new importance. This study was aimed at detecting cardiac side effects of pirenzepine due to low receptor specificity. Pirenzepine (10 mg) was given via the peripheral or central venous route at an injection velocity of 5 or 30 seconds as well as a control of 2 ml normal saline solution via the central venous route for 5 seconds, 20 times each. Heart rate and blood pressure were determined before and after the injection. Independent of the injection site or velocity, an increase in the heart rate was found after the injection of pirenzepine. The increase was more marked if the central venous route was used. The percentage rise in heart rate was up to the thirteenth minute highly significant when comparing pirenzepine to normal saline solution. There were no changes in blood pressure. If M1-cholinoceptors are blocked, a reduction of the heart rate is seen. Blocking M2-cholinoceptors causes a rise in the heart rate. Injecting 10 mg of the M1-antagonist pirenzepine results in a significant increase in the heart rate, independent of site or velocity of injection which can be explained by blocking M2-cholinoceptors at the same time. To prevent this probably dose-dependent effect, pirenzepine should be given slowly over a couple of minutes.

[Life-threatening lactic acidosis during total parenteral nutrition. Successful therapy with thiamine]

Two patients, 37 and 44 years old, respectively, developed severe metabolic acidosis after abdominal surgery which was followed by three weeks of total parenteral nutrition. Septicaemia, peritonitis or hypoxia were excluded as possible causes. Both patients had very high serum lactate concentrations (24.3 and 22.8 mmol/l, respectively). Conventional treatment with buffer agents was unsuccessful. Because vitamin B1 deficiency was suspected, two doses of 400 mg thiamine were administered. In both patients the extreme lactic acidosis disappeared immediately after the injections. Both patients were later discharged without any symptoms.

Clinical evaluation of hypothermic ventricular fibrillation, multi-dose blood cardioplegia, and single-dose Bretschneider cardioplegia in coronary surgery

37 patients undergoing coronary revascularization were randomly assigned to three protocols for intraoperative myocardial protection: hypothermic ventricular fibrillation (HF) (n = 13), multi-dose blood cardioplegia (BCP) (n = 12) and single-dose Bretschneider's crystalloid cardioplegia (CCP) (n = 12). As intraoperative markers of ischemic damage myocardial ultrastructure, ATP, and CP contents were determined in left ventricular biopsy specimens taken before and after cardiac arrest. Release of serum enzymes (CK, CK-MB, LDH, SGOT) was determined pre- and postoperatively. Hemodynamic data were assessed before, during, and after operation. The incidence of low cardiac output, positive inotropic support, intraaortic balloon counterpulsation, peri-operative myocardial infarction, rhythm disturbances, and the rate of spontaneous defibrillation was compared between groups. The results show a better preservation of high energy phosphates in the BCP group as compared to the HF and CCP groups. Myocardial ultrastructure showed moderate ischemic damage in the hypothermic fibrillation group; in contrast, only slightly deteriorated cells were seen after cardiac arrest, when cardioplegia was used. The incidence of rhythm disturbances was 25% for HF and 42% for CCP. In contrast, only 17% of new rhythm disturbances were seen in the BCP group. Functional recovery (i.e. CI and SWI) of hearts protected with BCP was generally greater as compared to HF and CCP. Release of MB-creatine-kinase isoenzyme was higher in the HF group as compared to cardioplegia. Clinical outcome in terms of incidence of peri-operative infarction, positive inotropic support and low cardiac output was superior in the BCP group but not significantly different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal by nalbuphine of respiratory depression caused by fentanyl

In 60 ASA class I or II patients given intravenous fentanyl for elective operations in doses large enough to produce postoperative respiratory depression, the intravenous administration of 20 mg nalbuphine resulted in prompt reversal of respiratory depression without loss of analgesia.

[Oral glucose tolerance tests--with or without estimation of serum insulin? (author's transl)]

Blood glucose and serum insulin values were determined after oral glucose tolerance tests in 528 persons with suspected pathological or disturbed glucose tolerance. Results were evaluated depending on sex, age, overweight, and familial diabetes. There were no differences of serum insulin secretion and behaviour of blood sugar between males and females. With increasing age there was a marked decrease of insulin secretion. In contrast there was increased hyperinsulinaemia with increasing overweight. This was particularly evident in persons with comparably reduced glucose tolerance but with different body weight. "Classical" changes of insulin secretion, as described for prediabetes and manifest diabetes in contrast to persons with normal metabolism, were only seen in selected groups of probands with normal weight. Serum insulin shows greater variability than blood glucose. Estimations of insulin are not necessary when assessing disturbances of glucose tolerance.