Tuesday, March 30, 2010

Trendelenburg Position under review

(from Canadian journal of emergency medicine)
Prospective studies

In a 1967 prospective study, Taylor and Weil tested the effectiveness of the Trendelenburg position in 6 hypotensive patients in clinical shock and 5 normotensive controls.3 In 9 of the 11 of patients, Trendelenburg positioning was ineffective, causing reductions in systolic, diastolic and mean arterial pressures. These authors noted that, in the head-down position, the viscera weigh down the diaphragm and compromise lung volumes. They also suggested that patients were at higher risk of cerebral edema, retinal detachment and brachial nerve paralysis.3

In 1994, Sing and colleagues4 assessed the impact of the Trendelenburg position on oxygen transport in 8 hypovolemic postoperative patients and found that it was associated with higher mean arterial blood pressure but not with improved cardiac output. Therefore, despite increases in blood pressure and left ventricle filling, there do not appear to be changes in tissue oxygenation during body tilting.4,5

In 1985, Bivins and coworkers6 studied the effect of the Trendelenburg position on blood distribution, finding that only 1.8% (99% confidence interval, -1.3% to 4.7%) of the total blood volume was displaced centrally when normovolemic patients were placed in the head-down position. They concluded that the autotransfusion effect produced by Trendelenburg positioning was small and unlikely to have an important clinical effect.6

Sibbald and cohorts investigated the effect of the Trendelenburg position on systemic and pulmonary hemodynamics in 76 critically ill patients (61 normotensive and 15 hypotensive) with acute cardiac illness or sepsis.7 In the normotensive group there was no change in pre-load or mean arterial pressure, but cardiac output increased slightly. In hypotensive patients there was no increase in preload or mean arterial pressure, but cardiac output decreased, suggesting that Trendelenburg positioning may be detrimental. These authors, like others, concluded that there were no demonstrable beneficial hemodynamic effects in hypotensive patients.1,3,7

1. Martin JT. The Trendelenburg position: a review of current slants about head down tilt. AANA J 1995;63:29-36.
2. Ostrow CL. Use of the Trendelenburg position by critical care nurses: Trendelenburg survey. Am J Crit Care 1997;6:172-6.
3. Taylor J, Weil MH. Failure of the Trendelenburg position to improve circulation during clinical shock. Surg Gynecol Obstet 1967;124:1005-10.
4. Sing RF, O'Hara D, Sawyer MA, Marino PL. Trendelenburg position and oxygen transport in hypovolemic adults. Ann Emerg Med 1994;23:564-7.
5. Terai C, Anada H, Matsushima S, Shimizu S, Okada Y. Effects of mild Trendelenburg on central hemodynamics and internal jugular vein velocity, cross-sectional area, and flow. Am J Emerg Med 1995;13:255-8.
6. Bivins HG, Knopp R, dos Santos PA. Blood volume distribution in the Trendelenburg position. Ann Emerg Med 1985;14:641-3.
7. Sibbald WJ, Paterson NA, Holliday RL, Baskerville J. The Trendelenburg position: hemodynamic effects in hypotensive and normotensive patients. Crit Care Med 1979;7:218-24.

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