Pharmacological and Parenteral Therapies Q 23
A male client was on warfarin (Coumadin) before admission and has been receiving heparin I.V. for 2 days. The partial thromboplastin time (PTT) is 68 seconds. What should Nurse Carla do?
A. Stop the I.V. infusion of heparin and notify the physician.
B. Continue treatment as ordered.
C. Expect the warfarin to increase the PTT.
D. Increase the dosage, because the level is lower than normal.
Correct Answer: B. Continue treatment as ordered.
The effects of heparin are monitored by the PTT is normally 30 to 45 seconds; the therapeutic level is 1.5 to 2 times the normal level.
Option A: There is no need to stop the infusion since the PTT is at a therapeutic level. In patients receiving concomitant heparin and warfarin therapy, PTT reflects the combined effects of both drugs. Because of the marked effect of warfarin on the PTT, decreasing heparin dose in response to a high PTT frequently results in subtherapeutic heparin levels.
Option C: The PTT is not used to monitor warfarin therapy, but PTT may be prolonged by warfarin at high doses.
Option D: The level is correct; increasing the dosage is unnecessary. Warfarin markedly affects PTT, for each increase of 1.0 in the international normalized ratio, the PTT increases 16 seconds.