The capillary fragility test indicates the ability of capillaries to resist rupturing under pressure. Excessive capillary fragility may be caused by either abnormalities of capillary walls or thrombocytopenia. The causes of positive test results are listed in Table 2-6.

The test is performed by applying a blood pressure cuff inflated to 100 mm Hg to the client's arm for 5 minutes. The resulting petechiae in a circumscribed area are then counted.

This test is unnecessary in the presence of obvious petechiae or large ecchymoses. It also should not be performed on clients known to have or suspected of having DIC.

• Fewer than 10 petechiae (excluding those that may have been present before the test) in a 2-inch circle is considered normal. Results may also be reported according to the following scale, with grade 1 indicating a normal or negative result. Causes of positive results are listed in Table 2-6.

• Repetition of the test on the same extremity within 1 week will yield inaccurate results.

• History of "easy bruising" or production of petechiae by the application of a tourniquet for venipuncture
• Verification of increased capillary fragility, although the test itself is not specific for any particular bleeding disorder (see Table 2-6)

Nursing Care Before the Procedure

Explain to the client:

• The procedure, including the degree of discomfort to be expected from the inflated blood pressure cuff

Inspect the client's forearms and select a site that is as free as possible of petechiae. Measure an area 2 inches in diameter; the site may be circled lightly with a felt-tipped marker if necessary for reference. If petechiae are present in the site to be measured, note and record the number.

A blood pressure cuff is applied to the arm and inflated to 100 mm Hg. The pressure is maintained for 5 minutes. The blood pressure cuff is then removed and the petechiae counted and the number recorded.

Nursing Care After the Procedure

• There is no specific aftercare. If the arm feels "tense" or "full," it may be elevated for a few minutes to hasten venous drainage.
• Complications and precautions: Note and report tendency for easy bruising or presence of petechiae. Take measures to prevent trauma to the skin and mucous membranes if results are above the normal values.