Evaluation of the tilt test in an adult emergency medicine population.

STUDY OBJECTIVE

To evaluate the usefulness of the tilt test in identifying significantly dehydrated or occultly bleeding adult patients in an emergency department.

DESIGN

Prospective.

SETTING

Urban ED.

TYPES OF PARTICIPANTS

Two hundred two ill adult patients with complaints suggestive of dehydration and/or occult blood loss and a control sample of 21 healthy individuals.

INTERVENTION

Orthostatic measurements were taken from blood samples from the ill and healthy patients. The estimates of the degree of dehydration measured or calculated were total body water deficit percentage (based on measured serum osmolality), ratio of blood urea nitrogen to creatinine, creatinine, and hematocrit. Multiple historical and physical examination variables related to dehydration or occult bleeding were recorded.

MEASUREMENTS AND MAIN RESULTS

Multiple analysis of variance testing of the historical and examination variables in the 166 dehydrated patients revealed the absence of syncope (P = .037) and the lack of axillary sweat (P = .026) to be significantly associated with an increased level of dehydration. Regression analysis of the orthostatic measurements and age with the estimates of dehydration found that orthostatic change in heart rate (P = .0165) and age (P = .0047) demonstrated a very small (r2 = .098) association with the level of dehydration. Orthostatic changes in systolic blood pressure and diastolic blood pressure demonstrated no statistically significant association with level of dehydration. There was wide variation in the tilt test measurements in samples from both the healthy and the ill patients: heart rate, 6.8 +/- 7.8 versus 13.2 +/- 10.5; systolic blood pressure, -2.5 +/- 8.0 versus -8.3 +/- 12.8 mm Hg; and diastolic blood pressure, 5.3 +/- 9.9 versus 0.6 +/- 8.6 mm Hg, respectively. The only parameter that attained statistical significance between the 36 blood-loss patients and the healthy patients was change in systolic blood pressure (P = .001); however, this was not clinically significant (-10.7 +/- 13.7 versus -2.5 +/- 8.0 mm Hg, respectively).

CONCLUSION

It appears impossible to define a "positive" tilt test that would adequately identify patients with clinically significant dehydration or blood loss; this is due to the large variance in patients' orthostatic measurements both in a healthy and in an ill state and the lack of a significant correlation of orthostatic measurements to a level of dehydration. Lack of axillary sweat, no complaint of syncope, and younger age all indicate greater degrees of dehydration.