Der Anaesthesist
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Randomized Controlled Trial Comparative Study Clinical Trial
[Aortofemoral bifurcation bypass--effect of anesthesia procedure (NLA, thoracic continuous catheter peridural anesthesia) on circulation, respiration and metabolism. Hemodynamic changes caused by peridural anesthesia and anesthesia induction].
In 50 patients scheduled for infrarenal aortic bypass surgery the cardiovascular effects of two anaesthetic regimes were investigated prior to surgery. A Swan-Ganz-catheter was used for haemodynamic measurements. These patients, having been randomized into two groups, were optimally volume loaded (PCWP 10 mmHg) before anaesthesia. In 24 patients a thoracic epidural was induced with 12-15 ml 0.25% plain bupivacaine. When segmental anaesthesia had extended from T4/5 to L1/2 general anaesthesia was additionally applied (flunitrazepam 1.5-2 mg, pancuronium bromide 0.1 mg/kg). In 26 patients neuroleptanaesthesia was induced (droperidol 0.1-0.2 mg/kg, fentanyl 0.01 mg/kg, pancuronium bromide 0.1 mg/kg, and thiopentone 100-150 mg. Haemodynamic measurements were made before injection into the epidural catheter, after complete spread of anaesthesia, before commencing general anaesthesia and 10-15 min thereafter. ⋯ Neither of the two procedures were associated with severe haemodynamic alterations. In the epidural group HR fell slightly during latency of complete spread and increased to the same extend following general anaesthesia. The epidural caused MAP (104 to 88 mmHg), mean PAP (20 to 14 mmHg), PCWP (10 to 7.5 mmHg), and RAP (4.5 to 2.5 mmHg) to decrease moderately but no further changes were effected by the subsequent general anaesthesia. SVR and PVR were not influenced by either epidural or by general anaesthesia. CI (3.6 to 3.41 . min-1 . m-2), LVSWI (67 to 52 p . m-1), and cardiac minute work index (55 to 40 J . min-1 . m-2) decreased during latency of complete spread but were no further influenced by general anaesthesia. The haemodynamic changes of neuroleptanaesthesia were almost identical to those of the combined epidural-general anaesthesia. For the operation which followed, a continuous infusion of 0.125 per cent plain bupivacaine (0.25 ml/kg X h) via epidural catheter (in combination with N2O/O2-anaesthesia) was sufficient for complete analgesia in the epidural group. These findings lead to the conclusion that a small bolus volume and a low concentration of bupivacaine result in good anaesthesia while avoiding serious haemodynamic alterations.
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Implantable devices (implanted pump/implanted catheter and port) are recommended for continuous epidural application of opiates or local anaesthetics in order to reduce hygienic problems during long term epidural medication. No signs of contamination could be found during bacteriologic culture of residual volumes of 30 patients treated with epidural drug delivery systems and of samples collected during an in vitro investigation (incubation of filled external pump systems at body temperature/storage of syringes with a premixed solution of opiate and local anaesthetic for repeated epidural bolus application). As demonstrated in a case report prophylactic antibiotic coverage prior to implantation may be necessary in patients with a preexisting susceptibility to infection. The concentrations of morphine (radioimmuno-assay) and of bupivacaine (gas-solid chromatography) within the reservoir were stable during clinical therapy as well as during the in vitro experiments.