Reproducibility of central venous pressures in supine and lateral positions: a pilot evaluation of the phlebostatic axis in critically ill patients.
OBJECTIVE
To determine if the phlebostatic axis (PA) can be used to obtain reproducible central venous pressures (CVP) in laterally positioned critically ill patients.


METHODS
A quasi-experimental study design was used. The outcome variable was central venous pressure. The explanatory variables were position (supine, 30 degrees right lateral, 30 degrees left lateral) and transducer leveling procedure (supine PA, upper PA, dependent PA). Each subject was used as his or her own control.


METHODS
General intensive care unit of a 929 bed metropolitan teaching hospital in New South Wales, Australia.


METHODS
A convenience sample of 25 critically ill patients (15 men and 10 women) with an average age of 59.6 years +/- 15.2.


METHODS
Each subject's baseline CVP range was collected over a 25-minute period in a supine position. CVP measurements were then obtained in the left and right lateral positions (initial lateral position alternated for each subsequent subject). When the subject was lateral, three CVP readings corresponding to the three transducer leveling procedures were taken.


METHODS
One-way repeated measures analysis of variance (one for each leveling procedure) were performed. Clinical significance was deemed evident when the lateral CVP measurement exceeded the baseline range.


RESULTS
Statistically significant changes were associated with the upper PA (p < 0.001) and the dependent PA (p < 0.001). Only the supine PA yielded statistically nonsignificant changes in CVP (p = 0.073). However, power analysis indicated that the results were not conclusive (power = 0.520). Clinical significance was determined in 100% and 92% of subjects in the left lateral and right lateral positions, respectively, when using the upper PA whereas the dependent PA yielded clinical significance in all (100%) subjects. Clinical significance was seen in 46% and 42% of subjects for the left lateral and right lateral positions, respectively, when the supine PA was used.


CONCLUSIONS
Of the three leveling procedures, the supine PA yielded the most reproducible CVP measures. However, further studies are required before the supine PA can be recommended as a valid and reliable transducer position for CVP measurement in laterally positioned patients.
Westmead Hospital, NSW, Australia.
K C
KC
Potger
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D
Elliott
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001508:Bed Conversion; D002496:Central Venous Pressure; D016638:Critical Illness; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation; D010865:Pilot Projects; D012016:Reference Values; D015203:Reproducibility of Results; D016683:Supine Position / Q000502:physiology*