Anaesthesia
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Comparative Study
Cardiac output measurement by pulse dye densitometry in cardiac surgery.
Summary The aim of this study was to compare the accuracy of pulse dye densitometry with that of bolus thermodilution cardiac output measurement in patients before and after elective coronary artery bypass grafting. Twenty-eight patients were studied. Agreement between mean thermodilution and pulse dye densitometry cardiac output values was assessed by Bland-Altman analysis. ⋯ Mean bias was + 0.566 l.min(-1), the limits of agreement were +/- 2.51 l.min(-1) and mean error was 60.9%. Postoperative cardiac output data were not analysed because pulse dye densitometry signals were low or absent in > 50% of the patients. We conclude that pulse dye densitometry using indocyanine green 5 mg or 20 mg is inaccurate in anaesthetised patients before coronary artery bypass surgery and cannot be used after surgery because of a high incidence of low pulse dye densitometry signal amplitudes.
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Continuous central pressure monitoring and simultaneous continuous infusion via the same central venous catheter are sometimes necessary. Based on theoretical calculations and experimental measurements, we have determined that pressure monitoring is essentially unaffected if the continuous infusion rate is 50 ml.h(-1) or less for an adult and a paediatric central catheter. At rates > 200 ml.h(-1), the central venous pressure is exaggerated by up to 4 mmHg and 8 mmHg for the adult and paediatric catheters, respectively.
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Lower limb peripheral nerve blocks are used to provide surgical anaesthesia or postoperative analgesia. Anatomical texts imply that femoral and saphenous nerve blocks be evaluated by sensory testing of the skin overlying the anterior aspect of the thigh, and the medial aspect of the foot, respectively. We have mapped the distribution of anaesthesia in 25 adults following femoral nerve blockade, performed using the inguinal paravascular technique of Winnie. ⋯ We conclude that demonstration of complete quadriceps paralysis confirms femoral nerve blockade. Failing that, sensory evaluation of a femoral nerve block should involve testing the skin of the middle third of the medial aspect of the thigh. The skin overlying the anteromedial aspect of the middle third of the leg should be evaluated for saphenous nerve block.
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Brain stem death may be a difficult concept for relatives to understand. Our ITU practice follows published recommendations that the use of explanatory leaflets showing CT scans and observing brain stem death testing in some cases may help relatives to understand that death has occurred. Using this strategy, we interviewed 27 relatives 12 months after bereavement following certification by brain stem testing, investigating their understanding of brain stem death, subsequent attitudes to organ donation, grief reactions and attitudes of those who had observed the tests. ⋯ Only five relatives observed the tests, all were pleased that they had done so as this had confirmed their understanding that death had occurred; however, these relatives had more evidence of psychological distress. No relatives who agreed to organ donation regretted this but three who did not allow donation subsequently expressed regret. Several relatives thought that observing the tests would have helped them to understand that death had occurred, making easier the decision to allow organ donation.
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Case Reports
Use of remifentanil for tracheal intubation for caesarean section in a patient with suxamethonium apnoea.
A parturient presented for elective caesarean section with a history of multiple spinal operations and scoliosis and a biochemical diagnosis of suxamethonium apnoea. She declined any attempt at regional anaesthesia. ⋯ The parturient awoke following an uneventful caesarean section with excellent pain relief and no recall. The baby had normal Apgar scores and umbilical blood gas measurements.