Effect of lateral position on arterial and venous blood gases in postoperative cardiac surgery patients

Abstract

BACKGROUND: Investigators have suggested that lateral position may have clinically significant effects on oxygenation in cardiac surgery patients. Presence of lung disease and type of cardiac surgery may be important considerations. OBJECTIVES: To determine the effect of position (left, right, supine) on blood gases in patients who have had coronary artery bypass or cardiac valvular surgery and to compare the effect of position on blood gases in cardiac surgery patients having preoperatively diagnosed lung disease with those having no lung disease. METHODS: A repeated measures design was used to study 120 mechanically ventilated, postoperative cardiac surgery patients. Subjects were randomly assigned a sequence of three positions (supine, and 45; right and left lateral) after cardiac surgery. Heart rate, respiratory rate, and arterial blood gas values were collected in each position. Venous blood gas values were collected from a subset of 40 subjects. RESULTS: A statistically significant effect of position on PaO2 was found in the group as a whole. The mean PaO2 in the left lateral position was lower than the value in the right or supine positions. No significant effects for position and pH, PaCO2, or bicarbonate were detected. No significant effects were found for type of surgery or the presence of absence of preoperative lung disease. A significant effect of position on venous pH was detected. No significant position effects were found for PvO2, PvCO2, bicarbonate, or venous saturation. No significant position effects were found for the calculated arterial-venous oxygen difference. CONCLUSIONS: The results of this study support those of previous research, which reported lower PaO2 in postoperative coronary artery bypass graft patients in the left lateral position. Mean differences in PaO2 were small, suggesting that the known benefits of lateral positioning in the early postoperative period outweigh the potential risks.

S2e guideline: positioning and early mobilisation in prophylaxis or therapy of pulmonary disorders

“…In postoperatively ventilated patients with healthy lungs and without acute respiratory insufficiency, without atelectasis and with a high tidal volume, the lateral position (45 ° –90 ° ) did not improve the pulmonary gas exchange compared to the supine position [ 212 , 285 , 286 ] (evidence level 2b). The moderate lateral position (45°) did not affect any clinical changes of the gas exchange, haemodynamics and tissue perfusion compared to the supine position [ 21 , 285 , 286 ] (evidence level 4). The mixed venous oxygen saturation decreased minimally [ 108 ] (evidence level 4).…”

Early postoperative 30° lateral positioning after coronary artery surgery: influence on cardiac output

“…Studies in postoperative cardiac surgery patients (Tidwell et al 1990, Banasik & Emerson 1996 and other ICUpatients (Lewis et al 1997, Gawlinski & Dracup 1998, Banasik & Emerson 2001 show a small but significant decrease in mixed venous oxygen saturation (SvO 2 ) (Tidwell et al 1990, Banasik & Emerson 1996, Lewis et al 1997, Gawlinski & Dracup 1998 and in partial pressure of oxygen in arterial blood (PaO 2 ) (Banasik & Emerson 1996) in left and right 45°lateral position. This decrease in the SvO 2 occurred directly after turning, was transient within five minutes and was judged clinically irrelevant.…”

“…Studies in postoperative cardiac surgery patients (Tidwell et al. 1990, Banasik & Emerson 1996) and other ICU‐patients (Lewis et al. 1997, Gawlinski & Dracup 1998, Banasik & Emerson 2001) show a small but significant decrease in mixed venous oxygen saturation (SvO 2 ) (Tidwell et al.…”

“…1997, Gawlinski & Dracup 1998, Banasik & Emerson 2001) show a small but significant decrease in mixed venous oxygen saturation (SvO 2 ) (Tidwell et al. 1990, Banasik & Emerson 1996, Lewis et al. 1997, Gawlinski & Dracup 1998) and in partial pressure of oxygen in arterial blood (PaO 2 ) (Banasik & Emerson 1996) in left and right 45° lateral position.…”

“…1990, Banasik & Emerson 1996, Lewis et al. 1997, Gawlinski & Dracup 1998) and in partial pressure of oxygen in arterial blood (PaO 2 ) (Banasik & Emerson 1996) in left and right 45° lateral position. This decrease in the SvO 2 occurred directly after turning, was transient within five minutes and was judged clinically irrelevant.…”