Effect of positioning on SvO2 in the critically ill patient with a low ejection fraction.
BACKGROUND
Critically ill patients with a low ejection fraction may be vulnerable to decreased mixed venous oxygen saturation (SvO2) resulting from position change.


OBJECTIVE
The objectives of this study were to describe the effects of changes in positioning on SvO2 in critically ill patients with a low ejection fraction (< or = 30%) and to describe the contribution of variables of oxygen delivery (DO2) and oxygen consumption (VO2) to the variance in SvO2.


METHODS
An experimental two-group repeated-measures design was used to study 42 critically ill patients with an ejection fraction of less than or equal to 30% (M= 19.5%). Patients were assigned randomly to one of two position sequences: supine, right lateral, left lateral; or supine, left lateral, right lateral. Data on SvO2 were collected at baseline, each minute after position change for 5 minutes, and at 15 and 25 minutes.


RESULTS
Repeated-measures multivariate analysis of variance showed a difference in SvO2 among the three positions across time (p< .0001), with the greatest differences occurring within the first 4 minutes and in the left lateral position. Stepwise multiple regression showed that VO2 accounted for a greater proportion of the variance in SvO2 with position change than did DO2 (54% [p = .001] vs. 31% [p= .001]).


CONCLUSIONS
Changes in SVO2 occur with positioning in critically ill patients with a low ejection fraction. These changes are transient and are the result of changes in VO2 rather than changes in DO2.
University of California, Los Angeles, Medical Center, USA.
A
A
Gawlinski
K
K
Dracup
D000368:Aged; D016638:Critical Illness / Q000451:nursing*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010100:Oxygen / Q000097:blood*; D013318:Stroke Volume; D016683:Supine Position
D010100:Oxygen