Sebastian Reiz

Postoperative confusion after anesthesia in elderly patients with femoral neck fractures.

Fifty-seven patients, all over the age of 64, with femoral neck fracture were randomized to receive epidural or halothane anesthesia to see if the anesthetic technique influenced the incidence of postoperative confusion. All patients were lucid on admission. Using the American Psychiatric Associations Diagnostic and Statistical Manual of Mental Disorders (DSM-III) as criteria for confusion, we found that 44% of the patients developed confusion that correlated closely to a history of mental depression (P < 0.01) and to the use of drugs with anticholinergic effect (P < 0.005). There was no difference in the incidence of confusion between the two anesthetic groups. In patients given halothane, however, early postoperative hypoxemia was associated with confusion (P < 0.05). Patients with confusion had significantly more postoperative complications and almost four times longer hospitalization times. It is concluded that anticholinergic medication and a history of mental depression are predominant risk factors for development of postoperative confusion and in this respect are more important than the anesthetic technique.

A Geriatric-Anesthesiologic Program To Reduce Acute Confusional States in Elderly Patients Treated for Femoral Neck Fractures

The aim of this study was to evaluate the effect of a geriatrk‐anesthesiologic intervention program for the prevention and treatment of acute confusional states (ACS) in elderly patients treated for femoral neck fractures. The intervention program was based on the results of previous prospective studies in similar patient populations. The outcome of the intervention, comprising 103 patients, was compared with that of an earlier study comprising 111 patients. The intervention program consisted of pre‐ and post‐operative geriatric assessments, oxygen therapy, early surgery, prevention and treatment of peri‐operative blood pressure falls and treatment of post‐operative complications. The incidence of ACS was lower, 47.6%, in the intervention study compared with 61.3% (P < 0.05) in the control study. Furthermore, the ACS that occurred in the intervention study was less severe and of shorter duration than that in the control study. The incidence of post‐operative decubital ulcers, severe falls, and urinary retention was also lower. The mean duration of orthopedic ward stay was 17.4 days in the control study and 11.6 days in the intervention study (P < 0.001). It can be concluded that the intervention program reduced the incidence, severity, and duration of ACS which resulted in a shortened orthopedic ward stay.

Isoflurane—A Powerful Coronary Vasodilator in Patients with Coronary Artery Disease

The coronary hemodynamic effects of 1% end-tidal isoflurane administered in oxygen-nitrogen by intermittent positive-pressure ventilation (IPPV) were investigated in 21 patients with stable coronary artery disease. Besides standard central hemodynamic measurements, coronary sinus blood flow was meas

Cardiotoxicity of ropivacaine – a new amide local anaesthetic agent

Anaesthetically equipotent doses of lidocaine, bupivacaine and a new bupivacaine–like local anaesthetic agent, ropivacaine, were injected into the left anterior descending coronary artery of pentobarbital–anaesthetized pigs. The aim was to study the cardiotoxicity of ropivacaine in relation to the two other drugs. A random, crossover, dose response study design was used. The following doses of the drugs were administered: lidocaine (L): 1,2,4,8 and 16 mg, bupivacaine (B): 0.25, 0.5, 1,2 and 4 mg and ropivacaine (R): 0.33, 0.66 1.33, 2.66 and 5.33 mg. Systemic haemodynamics, left ventricular dP/dT and a 12–lead electrocardiogram were recorded continuously during the study period. The drugs depressed cardiac contractility in relation to their local anaesthetic potency on the isolated nerve–4:3:l(B:R:L). The prolongation of the ECG QRS–interval was regarded as a measure of electrophysiologic toxicity. Comparable prolongation of the QRS–interval was recorded after 2 mg of bupivacaine, 4.5 mg of ropivacaine and 30 mg of lidocaine. Thus, the electrophysiological toxicity ratio was 15:6.7:1 (B:R:L). Provided local anaesthetic potency data can be extrapolated from the isolated nerve preparation to regional anaesthesia in humans, ropivacaine appears to provide a greater margin of safety than bupivacaine, if inadvertently injected into the venous circulation.

A comparison of the electrocardiographic cardiotoxic effects of racemic bupivacaine, levobupivacaine, and ropivacaine in anesthetized swine.

We sought, in this observer-blinded study, to determine the lethal dose for each of the local anesthetics levobupivacaine (L), racemic bupivacaine (B), and ropivacaine (R), and to compare their respective effects on the QRS interval of the precordial electrocardiograph after intracoronary injection. Anesthetized swine were instrumented with a left anterior descending artery coronary angiography catheter and injected with increasing doses of L, B, or R according to a randomized protocol. The doses administered were 0.375, 0.75, 1.5, 3.0, and 4.0 mg, with further doses increasing in 1-mg increments until death occurred. Plotting the mean maximum QRS interval as a function of the log10 mmol dose allowed the following cardiotoxicity potency ratios to be determined for a doubling of QRS duration—B:L:R = 2.1:1.4:1. The lethal doses in millimoles (median/range) for L and R were (0.028/0.024–0.031) and (0.032/0.013–0.032), respectively, and were significantly higher than for B (0.015/0.012–0.019) − (P < 0.05, n = 7 for all groups). The lethal dose did not differ between R and L. Thus, the cardiotoxicity potency ratios for the three anesthetics based on lethal dose were: 2.1:1.2:1. If the anesthetic potencies for B and L are similar, the latter should have less potential for cardiotoxicity in the clinical situation. Implications Animal experiments have shown levobupivacaine and ropivacaine to be less cardiotoxic than racemic bupivacaine. This in vivo study, using a validated swine model, compared the relative direct cardiotoxicities of these three local anesthetics. The lethal dose did not differ between levobupivacaine and ropivacaine, but was lowest for racemic bupivacaine.

EMLA ‐ a Eutectic Mixture of Local Anaesthetics for Topical Anaesthesia

A new topical anaesthetic formulation, EMLA, consisting of a eutectic mixture of the two local anaesthetics, prilocaine and lidocaine, was used in an attempt to reduce the pain associated with venous cannulation in children. The formulation of the local anaesthetic cream yields a high concentration (approximately 80%) of active substance compared with previous formulations (approximately 20%). A highly statistically significant difference in the experience of pain due to venous cannulation in favour of EMLA compared with placebo was found in this study (p<0.001) in 60 children from 6 to 15 years of age. Stimulus of C fibre endings in the subcutaneous tissue and/or the vascular wall seems to be the mechanism behind the slight to moderate discomfort experienced by about one third of the children treated with EMLA. Local side effects of EMLA were negligible.

Comparison of Hemodynamic, Electrocardiographic, Mechanical, and Metabolic Indicators of Intraoperative Myocardial Ischemia in Vascular Surgical Patients with Coronary Artery Disease

To compare mechanical, electrocardiographic, and metabolic indices of myocardial ischemia, the cardiokymogram (CKG), the V5 ECG, left anterior descending coronary artery territory lactate extraction, and pulmonary capillary wedge pressure (PCWP) were measured in 53 vascular surgical patients with coronary artery disease. Measurements were performed preoperatively and at four specific intraanesthetic intervals: after tracheal intubation, before surgery, and 10 and 30 min after incision. Measurements and sampling sequence took 5-7 min, and therapy for the probable cause of ischemia was instituted following completion of this sequence. Myocardial ischemia was defined as type II or III CKG, 0.1 mV or greater horizontal or downsloping depression of V5 ECG ST segment, 0.2 mV or greater elevation of V5 ECG ST segment, or myocardial lactate production. Thirty-nine patients (74%) had a total of 89 episodes of myocardial ischemia. Seventy-four episodes (83%) were detected by the CKG, 31 (44%) were evident on the ECG, and 13 (15%) by evidence of lactate production. The concordance among the indices of myocardial ischemia was poor. Patients with an abnormal preoperative ECG experienced a greater number of ischemic episodes (P less than 0.001). Elevation of PCWP or the presence of A-C or V-waves greater than 5 mmHg above the mean did not individually reflect ischemia reliably. Intraoperative myocardial ischemia is common in vascular surgical patients and is most sensitively detected by ventricular wall motion abnormality.

Superoxide dismutase and catalase reduce infarct size in a porcine myocardial occlusion-reperfusion model

We investigated if superoxide dismutase and catalase could reduce myocardial infarct size in an open chest occlusion-reperfusion model. Thirty pigs were used for the experiment. The left anterior descending artery was ligated for 60 min followed by a 5 h reperfusion period. After randomisation and blinding the two enzymes or placebo were injected into the left atrium as a bolus immediately before and at the end of the occlusion and as a continuous infusion over the first hour of the reperfusion period. The total dose for each enzyme was 8 mg/kg bw. Tetrazolium staining was used to determine infarct size. The study code was not broken until all calculations and exclusions had been made. Nine animals died from intractable ventricular fibrillation, most commonly during the occlusion. Another three were excluded for technical reasons. We found that superoxide dismutase and catalase reduced infarct size in relation to myocardium at risk from a mean of 89% to 63% (P less than 0.01). Initial plasma half life for the two enzymes after the bolus infusions were calculated to be 30 min.

Epidural Morphine for Postoperative Pain Relief

Thirty‐three patients were randomly assigned to two groups to study the analgesic potency, duration of action and side effects of epidural and intramuscular morphine after hip surgery. Two milligrams of preservative‐free morphine chloride in 10 ml of normal saline in the epidural space was compared to 10 mg of intramuscularly administered morphine. There was a more rapid onset of action after intramuscular morphine. However, the quality of pain relief was substantially higher and the duration of action markedly longer after epidural morphine. The total dose required in the epidural group was 3.6 mg and in the intramuscular group 41 mg during the 15‐h observation period. The side effects of epidural morphine were few and mild, the most embarrassing being urinary retention (20 %). Nausea and/or vomiting was less common after epidural morphine (20% versus 55%). Pruritus or respiratory depression which have been reported previously were not encountered. However, it is recommended that preservative‐free solutions are used to avoid itching and that the patients are monitored, as respiratory depression may occur long after administration of epidural opiate.

Differential depressant and electrophysiologic cardiotoxicity of local anesthetics: an experimental study with special reference to lidocaine and bupivacaine.

In 15 pigs lidocaine and bupivacaine were injected into the left anterior descending (LAD) coronary artery to investigate the cardiotoxic effects of these drugs. Anesthesia was maintained by a continuous intravenous pentobarbital infusion and ventilation was controlled. Aortic, pulmonary arterial, right atrial, and left ventricular pressures, a standard 12 lead ECG, cardiac output, and great cardiac venous blood flow were recorded. The local anesthetics were administered at body temperature over approximately 10 sec in a random, crossover fashion at the following equipotent anesthetic doses: bupivacaine, 0.25, 0.5, 1, 2, and 4 mg; lidocaine, 1, 2, 4, 8, and 16 mg. The hemodynamic effects were short-lived, peaking about 5 sec after drug infusion. At the highest dose, both drugs decreased left ventricular dP/dT by 28% (P less than 0.001) and aortic blood pressure by 12% (lidocaine) and 8% (bupivacaine) (P less than 0.001 and P less than 0.01). Heart rate, cardiac output, and coronary venous blood flow did not change. Thus, the cardiodepressant ratio between the two drugs was comparable with their local anesthetic the two drugs was comparable with their local anesthetic potency ratio (bupivacaine/lidocaine, 4:1). Seven animals died in ventricular fibrillation within 1 min after 4 mg bupivacaine dose. All animals given 16 mg lidocaine survived. Ventricular fibrillation was preceded by progressive widening of the QRS complexes recorded over the area perfused by the LAD. The ECG changes after 16 mg lidocaine were of the same magnitude as those recorded after 1 mg bupivacaine. In five of the surviving animals 32 and 64 mg lidocaine were injected intracoronarily after termination of the crossover study.(ABSTRACT TRUNCATED AT 250 WORDS)