Canadian Anaesthetists' Society journal
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Randomized Controlled Trial Clinical Trial
Effect of lateral position and volume on the spread of epidural anaesthesia in the parturient.
The effect of lateral positioning and the volume of drug injected on the spread of epidural anaesthesia was assessed in 131 healthy parturients. Epidural injection for anaesthesia was done at the L3-4 interspace and a catheter was inserted into the epidural space after injection of the drug. The patients were randomly assigned to four groups. ⋯ Maintenance of the lateral position after induction of epidural anaesthesia is compatible with satisfactory analgesia for labour. Twelve ml bupivacaine 0.25 per cent provides better analgesia than 6 ml bupivacaine 0.5 per cent although the same mass is injected. The quality of analgesia is improved by turning the patients to the contralateral side after injection of 12 ml bupivacaine 0.25 per cent.
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The feasibility of applying positive end expiratory pressure within the Bain circuit using an Emerson PEEP valve was studied. It was determined that varying degrees of PEEP may be applied within the Bain circuit using an Emerson PEEP valve during either mechanically or manually controlled ventilation but not during spontaneous breathing. There was some loss of measured tidal volume with increasing PEEP, due primarily to compression gas losses but also from leakage throughout the system. ⋯ PEEP may be applied between the Bain tubing and the manifold. However, one should then never allow the patient to breathe spontaneously as the PEEP valve presents an obstruction to inspiratory flow. With the PEEP valve relocated between the Bain manifold and the ventilator hose it was found that application of PEEP was possible without this disadvantage, but only during mechanical ventilation.
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Succinylcholine-induced potassium efflux was studied in two groups of healthy adult patients presenting for elective surgery. One group (Group 1) of 12 patients received alfathesin induction followed by succinylcholine. ⋯ Serial blood samples were taken pre-induction, post-induction and after succinylcholine for estimation of plasma potassium. The results show that pre-treatment with fazadinium 0.075 mg . kg-1 was effective in preventing succinylcholine-induced potassium efflux.
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Continuous infusion epidural anaesthesia may reduce the risks of hypotension, high spinal block and intravenous injection associated with repeated bolus injections. However, controlling the rate of a simple infusion is difficult and infusion pumps are expensive and bulky. We describe a method for continuous infusion epidural anesthesia using a 6 ml/hr capillary infusion device (Intraflo CFS-06F Sorenson Research Co., Salt Lake City, Utah) and bupivicaine 0.25 per cent. ⋯ A further 11 patients (22 per cent) required only one top-up for the second stage of labour after a mean pain-free time of 5.4 hours (range 1.5 to 9.7 hours). There were no maternal or foetal complications related to the technique of continuous infusion used. No block went higher than the ninth thoracic dermatome at any time.
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Lung areas with a low V/Q ratio cause hypoxaemia. The low alveolar oxygen concentration may cause local hypoxic pulmonary vasoconstriction (HPV) which reduces perfusion, raises the V/Q ratio, and hence reduces the tendency to a low PaO2. By changing PCO2, the HPV response can be altered. ⋯ We conclude that in this model a low PETCO2 (3.3 kPa) in hypoxic lung will reduce HPV, and will result in more severe hypoxaemia. This may have relevance in both anaesthetized and intensive care unit patients when a higher PaO2 may be obtained by increasing hypoxic lung PETCO2. The effect of PETCO2 on PaO2 will be influenced by other variables, but when hypoventilated or hypoxic exist, increasing PETCO2 may reinforce hypoxic pulmonary vasoconstriction and thus may increase PaO2.