Anti-arrhythmic drugs.
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Biomedical subjects
Publications and source records attributed to S M Lyons.
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Diazepam and flunitrazepam were compared in equipotent doses as induction agents for premedicated patients having cardiac surgery. Both drugs caused a significant fall in arterial blood pressure, a rise in Paco2 and a fall in Pao2. There was no significant difference between the two drugs in onset time of anaesthesia, cardiovascular or respiratory depression, or quality of induction. There was also no significant difference from induction with thiopentone in these respects. Diazepam, over a 0.2 to 0.6 mg/kg range of doses showed no difference in toxicity, although induction was clinically smoother with the higher dose.
The non-depolarizing muscle relaxant AH8165 has been compared at two doses (0.5 and 1.0 mg/kg) with pancuronium (0.1 mg/kg) during induction of anaesthesia for patients having major cardiac surgery. After barbiturate-opiate premedication and thiopentone induction, administration of pancuronium was followed by no significant alteration in heart rate or arterial pressure. Both doses of AH8165 werr followed by significant tachycardia, and the higher dose by arterial hypotension. The lower dose of AH8165 was unsatisfactory for tracheal intubation, but the AH8165 1 mg/kg gave intubating conditions similar to those with pancuronium 0.1 mg/kg.
One of four groups of patients was not premedicated; the others received diazepam 10 mg by mouth, diazepam 20 mg by mouth or a combination of pentobarbitone orally and morphine and hyoscine intramuscularly. The cardiovascular and respiratory parameters were studied before and after the premedication and any changes in sedation, apprehension and reaction to pain were noted. The ease of induction of anaesthesia in the four groups was compared. Most of the patients who received the pentobarbitone, morphine and hyoscine combination came to theatre calm, sedated and often asleep. They showed no significant cardiovascular or respiratory depression and the induction of anaesthesia was more satisfactory than in the other groups. Two of the patients who were not premedicated became very agitated in the ward and the remainder of the patients in this group were apprehensive in the anaesthetic room and during induction. The effects of diazepam in the two doses studied were intermediate between those who received the pentobarbitone, morphine and hyoscine and those who were not premedicated.
Plasma myocardial, and skeletal muscle digoxin concentrations were measured in 32 patients undergoing cardiopulmonary bypass who were on long-term treatment with digoxin. The patients were divided into 4 groups according to the daily digoxin dose and the interval between discontinuation of the drug and operation. Before bypass, the mean digoxin concentrations were 1.58 nmol/l (1.24 ng/ml) in plasma 65.2 nmol/kg (50.9 ng/g) in the atria, 121.4 nmol/kg (94.98 ng/g) in 11 papillary muscles, and 16.6 nmol/kg (13.0 ng/g) in skeletal muscle. Mean atrial digoxin concentrations were significantly lower tham mean papillary muscle concentrations in 11 patients. Ratios of plasma of myocardial or skeletal muscle digoxin concentrations were very variable. Generally digoxin concentrations were higher in patients on the larger digoxin dose and with the shorter discontinuation time before surgery. These differences attained significance only with plasma digoxin concentrations. There was a slight fall in plasma digoxin concentration during cardiopulmonary bypass but no significant differences were observed between plasma, atrial, or skeletal muscle digoxin concentrations before and at the end of bypass. No clear relation was seen between plasma or atrial digoxin concentrations and postoperative cardiotoxicity. Stopping digoxin 48 hours before operation appeared to account for pre- or post-bypass plasma digoxin concentrations of less than 1.0 nmol/l (0.8 ng/ml) in most of the instances encountered, whereas the 3 patients who developed pulsus bigeminus postoperatively had received 0.5 mg digoxin only 24 hours before operation.
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