• S E McNulty, J Weiss, S S Azad, D M Schaefer, J L Osterholm, and J L Seltzer.
• Department of Anesthesiology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107.
• J Clin Anesth. 1992 May 1; 4 (3): 220-5.

Study ObjectiveTo determine the effects of three different prone support systems (Andrews spinal surgery frame, Cloward surgical saddle, and longitudinal bolsters) on inferior vena cava (IVC) and superior vena cava (SVC) pressures; the validity of measuring central venous pressure (CVP) for the determination of ideal positioning of the patient; and the relationship among frame type, blood loss, and hemodynamic measurements.DesignProspective, randomized study of the hemodynamic effects of the prone position.SettingInpatient surgery at a university hospital (regional spinal cord injury treatment center).PatientsEighteen patients free of significant coexisting disease (ASA physical status I and II) undergoing elective lumbar laminectomy.InterventionsPatients were assigned to one of three support frames and measurement of SVC pressure, IVC pressure, and mean arterial pressures (MAP) were obtained supine, prone, and after repositioning. These pressures and measured blood loss were obtained every 15 minutes during the surgical laminectomy portion of the procedure.Measurements And Main ResultsPatients positioned on the Andrews frame had decreased mean SVC and IVC pressures from 8.7 mmHg and 8.4 mmHg in the supine position to 3.3 mmHg and 1.8 mmHg in the prone position, respectively (p less than 0.001). Prone position CVP also was significantly lower in the Andrews group compared with that in the other two groups (p less than 0.001). Repositioning efforts did not significantly decrease CVP. Blood loss was higher in the Cloward group (1,150 +/- 989 ml) than in the Andrews (245 +/- 283 ml) and bolsters (262 +/- 188 ml) groups (p less than 0.02).ConclusionsIncreased blood loss was not associated with increased SVC or IVC pressure, nor was there any significant correlation between any demographic or hemodynamic variable and blood loss. There was no evidence that CVP is useful in determining the ideal prone position in patients undergoing lumbar laminectomy.

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