Comparison of 24 hour whole body versus patch tests for estimating body surface electrolyte losses.

PURPOSE

To compare dermal electrolyte loss between whole body and regional patch methods in women during 24-h.

METHODS

Dermal loss was collected in 6 healthy women mean age 27 +/- 4 years, while consuming 936 mg/d sodium, 1764 mg/d potassium, 696 mg/d calcium, and 152 mg/d magnesium. Twenty-four hour whole body dermal loss was collected using cotton suits by a washdown procedure. Twenty-four hour patch loss was collected from 8 patches placed on the legs, arms, and back.

RESULTS

Dermal loss from whole body was 108 +/- 110 mg/d sodium, 133 +/- 87 mg/d potassium, 103 +/- 22 mg/d calcium, and 35 +/- 13 mg/d magnesium. Electrolyte content from the 8 patches was similar among sites and ranged from 1.01-1.41 mg/d sodium, 0.35-0.83 mg/d potassium, 1.0-1.45 mg/d calcium, and 0.43-0.49 mg/d magnesium. Projections from patches to whole body by the ratio of body surface area appear to overestimate actual whole body losses by 3.2X for sodium and calcium, 3.6X for magnesium, and 1.3X for potassium.

CONCLUSIONS

Regional patch methods are more appropriate for relative comparisons than for accurately determining total daily dermal electrolyte losses.