Canadian Journal of Anesthesia, Vol 31, 439-443, Copyright © 1984 by Canadian Anesthesiologists' Society

Clinical Reports: Comparative Value of Peripheral and Central Venous pCO₂ in Predicting Normal paCO₂ during Anaesthesia

¹ University of Brussels, Department of Anaesthesia of Brugmann Hospital, Brussels, Belgium

Address correspondence to: Dr. A. d'Hollander, Dept. of Anaesthesia, place Van Gehuchten, 4, Brugmann Hospital, B-1020, Brussels, Belgium.

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.

Key Words: ANAESTHESIA • general • CARBON DIOXIDE TENSION • venous, arterial