SummaryThe

Flow (V), volume (V), and tracheal pressure (Ptr) were measured throughout a series of brief (100 ms) interruptions of expiratory V in six patients during anesthesia (halothane-N2O) and anesthesia-paralysis (succinylcholine). For the latter part of spontaneous expiration and throughout passive deflation during muscle paralysis, a plateau in postinterruption Ptr was observed, indicating respiratory muscle relaxation. Under these conditions, passive elastance of the total respiratory system (Ers) was determined as the plateau in postinterruption Ptr divided by the corresponding V. The pressure-flow relationship of the total system was determined by plotting the plateau in Ptr during interruption against the immediately preceding V. Ers averaged 23.5 +/- 1.9 (SD) cmH2O X l-1 during anesthesia and 25.5 +/- 5.4 cmH2O X l-1 during anesthesia-paralysis. Corresponding values of total respiratory system resistance were 2.0 +/- 0.8 and 1.9 +/- 0.6 cmH2O X l-1 X s, respectively. Respiratory mechanics determined during anesthesia paralysis using the single-breath method (W.A. Zin, L. D. Pengelly, and J. Milic-Emili, J. Appl. Physiol. 52: 1266-1271, 1982) were also similar. Early in spontaneous expiration, however, Ptr increased progressively during the period of interruption, reflecting the presence of gradually decreasing antagonistic (postinspiratory) pressure of the inspiratory muscles. In conclusion, the interrupter technique allows for simultaneous determination of the passive elastic as well as flow-resistive properties of the total respiratory system. The presence of a plateau in postinterruption Ptr may be employed as a useful and simple criterion to confirm the presence of respiratory muscle relaxation.

Thirty-eight patients undergoing elective hip or knee surgery were randomly allocated to two groups. Neuromuscular blockade in group A was antagonized with neostigmine 2.5 mg and atropine 1.2 mg, while group B received no drugs to facilitate antagonism of blockade. The incidence and severity of postoperative nausea and vomiting were assessed 24 h after operation. Nausea and vomiting were significantly reduced in group B. The incidence of nausea in group A was 68%, compared with 32% in group B (P less than 0.01). The incidence of vomiting was 47% in group A, compared with 11% in group B (P less than 0.02). A significant relationship was shown between postoperative emetic symptoms and the antagonism of neuromuscular blockade by neostigmine and atropine.

Oxygen consumption (r carbon dioxide production ('(/C02). end-t~dat carbon dioxide partial pressure (PETC02), mixed venous oxygen saturation (S;'02) and haemodynamic variables were recorded every 30 rain for four hours in 1_5 patients recovering from hypothermic cardiopulmonary bypass (CPBFollowing hypothermic cardiopulmonary bypass (CPB), patients usually arrive in the Intensive Care Unit (ICU) with a nasopharyngeal temperature (NPT) of 34-36 ' C. t Sladen et al. showed that over the subsequent 8 hr patients rewarm to normothermia, with the maximal rate of rewarrning occurring 2-4 hr after admission to the ICU.2 During this period of very rapid rewarming, marked changes have been suggested in both metabolic rate and myocardial work) '4 Increases in 02 consumption (VO2) and carbon dioxide production ('i/CO2) are undesirable in post-CPB patients because they lead to increases in heart rate (HR), mean arterial pressure (MAP) and rate pressure product (RPP) s causing an increase in myocardial oxygen consumption.6 Moreover, if the extent of these metabolic changes is not recognized then both respiratory and metabolic acidosis may occur. The present study was designed to determine the extent of these metabolic changes and their haemodynamic consequences during the first four hours after CPB. We also wished to determine the effects of shivering on these variables, if these effects are significant and how best to follow their trend. MethodsFifteen patients scheduled for elective cardiac surgery were studied. Patients with symptomatic peripheral vas- CAN J ANAESTH 1988 ; 35:4 / pp332-7

To determine if general anaesthesia alone or in conjunction with surgery alters body protein turnover, we studied six healthy, unpremedicated females undergoing elective total abdominal hysterectomy. Changes in protein metabolism, synthesis and breakdown were estimated by an isotope dilution technique using a continuous infusion of the stable isotope tracer, L-[1-13C]leucine, before anaesthesia (4 h), during anaesthesia alone (1 h), during anaesthesia and surgery (1 h) and in the recovery period (2 h). General anaesthesia comprised thiopentone, pancuronium, enflurane (1 MAC) and oxygen-enriched air. An isotopic steady state in plasma 13C-alpha-ketoisocaproate (13C alpha-KIC) and expired 13C-carbon dioxide were obtained during the four periods. Collections of plasma and expired air were made during the steady state periods and plasma alpha-KIC enrichment measured to indicate precursor pool labelling from which leucine flux (equal to protein breakdown in the post-absorptive state) and oxidation were calculated, and whole body protein synthesis was derived. Whole body protein breakdown did not change with anaesthesia, but decreased with both surgery and during the acute recovery period (P less than 0.05). Protein synthesis did not change with anaesthesia and surgery, but decreased significantly after surgery (P less than 0.05).