Breathe without pain : Clinical and experimental studies in patients and volunteers with special reference to ventilatory regilation
Abstract: The major aims were, first, to study the advantages and disadvantages of intrathecal analgesia with bupivacaine and morphine with special reference to ventilation and pain relief and, second, to develop a method for studies of the ventilatory response to carbon dioxide and hypoxaemia in volunteers and in patients with varying degrees of ventilation-perfusion ratios.341 elderly patients undergoing major hip surgery perfonned under intrathecal analgesia or general anaesthesia and 31 young and healthy volunteers participated in this work. There were fewer complications and a shorter postoperative hospital stay in patients undergoing surgery under intrathecal analgesia with 0.3 mg morphine added to 20-22.5 mg bupivacaine without glucose compared to the general anaesthesia group as evaluated with the aid of case records. Postoperative pain after intrathecal morphine was evaluated by systemic morphine consumption and a visual analogue scale and was found to be of good quality for at least 40 h in the majority of the patients. Postoperative naloxone infusion rate was lowered stepwise between patient groups receiving intrathecal morphine. The dose 1 pg/kglh IV for 12 h and 0.25 pg/kg/h IV for the next 12 h had no influence on pain relief obtained by the intrathecal morphine.A non-rebreathing cireuit was designed and evaluated in volunteers and patients. The apparatus had no influence on ventilation of air over time, the results could be reproduced and the method was found to be suitable and safe for patients with varying ventilation-perfusion ratios. The ventilatory response to C02 was measured after 1.5 times the time taken to reach a new steady-state in FIITC02 after stimulation with 6% C02. The ventilatory response to hypoxaemia was measured when S02 had declined from normal values to 85%. The responses were evaluated before operation and 8 and 24 h after intrathecal injection in three patient groups: intrathecal analgesia with bupivacaine, with bupivacaine-morphine and with bupivacaine-morphine plus an IV infusion of naloxone. Intrathecal morphine had, on the whole, no effect on the ventilatorytesponses. However, additional systemic morphine or sedatives attenuated the responses. Naloxone infusion was judged to counteract ventilatory depression. The response to hypoxaemia was poor or absent in 1/3 of the elderly before operation,In conclusion, intrathecal analgesia with a mixture of bupivacaine and morphine offers excellent operative conditions in major hip surgery and a favourable postoperative course without pain for the elderly patient. Postoperative care of these elderly patients for at least 24 h is recommended and experienced personnel should continuously evaluate patients' status for detection of signs of ventilatory depression. The staff should have the knowledge and the facilities to treat ventilatory depression. Naloxone infusion can well be used as prophylaxis against ventilatory depression. Oxygen therapy is also recommended in these elderly patients both during and after operation until normal or near normal oxygenation, without oxygen therapy, is proven present.
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