Comparative value of peripheral and central venous pCO2 in predicting normal paCO2 during anaesthesia.

The ability of venous pCO2 to predict arterial pCO2 within the normal range was tested by measuring pCO2 in blood sampled simultaneously from a large forearm vein (PER), from the superior vena cava (SVC), and from an artery in 35 anaesthetized patients. The relationship between arterial and both venous pCO2's were studied in a first series of 15 patients (ASA physical status class I-II) anaesthetized with methohexitone, fentanyl, pancuronium and nitrous oxide/oxygen, and in a second series of 20 patients scheduled for cardiac surgery anaesthetized with flunitrazepam, fentanyl, pancuronium and nitrous oxide. A marked correlation was found between arterial and both venous pCO2's samples in the normal patients (a/PER: r = 0.922; a/SVC: r = 0.940); in the patients with abnormal cardiovascular status the correlation observed was less pronounced (a/PER: r = 0.501; a/SVC: r = 0.507). In view of the similar correlation coefficients observed from the PER or SVC blood sampling sites, we conclude that the degree of accuracy of the prediction of paCO2 from the venous pCO2's is not modified by the origin of the venous blood. The differences between the coefficients of correlation found in the normal patients and in those with abnormal cardiovascular function indicate that venous pCO2 as estimate of paCO2 appears useful only in subjects with normal haemodynamic status.

Stable muscle relaxation during abdominal surgery using combined intravenous bolus and demand infusion: clinical appraisal with ORG NC45.

In order to obtain stable muscle relaxation for intra-abdominal operation, a continuous demand perfusion of ORG NC45 was administered following a loading dose of 0.07 mg . kg-1. The patients had previously been anaesthetized with methohexitone, fentanyl and nitrous oxide. The perfusion rate of ORG NC45 was regulated so that the mechanical muscular response of the adductor pollicis following a supra-maximal stimulation of the ulnar nerve was maintained at 10 per cent of its initial value. The level of relaxation thus obtained was always adequate for the surgeons. During the course of the operation the requirement for more relaxant decreased progressively, becoming stable after one half hour. Nevertheless, during stable administration, individual variations were quite marked, being 44 to 483 micrograms/M2 BSA/10 min (average 225 micrograms/M2 BSA/10 min). The duration of the infusion varied from 60 to 107 minutes (average 103 minutes). After its termination the time taken from recovery varied between 3 and 82 minutes (average 27 minutes). Having regained a single twitch height of 75 per cent patients awoke rapidly after the administration of nitrous oxide was terminated. No signs of recurarization were noticed in any of the patients. In conclusion, this method of administration of ORG NC45 assures a stable level of curarization without side-effects. However, because of the different individual levels of sensitivity which were noted, this mode of administration requires careful monitoring to avoid inappropriate dosage.