Management of Significantly Elevated PTT (155) on Heparin Infusion
For a PTT of 155 seconds on heparin infusion, hold the heparin for 1-2 hours and recheck the PTT before resuming at a reduced rate. 1
Immediate Actions
Stop the heparin infusion immediately when the PTT is this significantly elevated (155 seconds, which is well above the therapeutic target of 1.5-2.5 times control or approximately 60-80 seconds). 1
Do not administer protamine sulfate for supratherapeutic PTT values in the absence of active bleeding, as the heparin will clear naturally and protamine carries its own risks. 1
Assess the patient for bleeding complications, as PTT values >70 seconds are associated with higher likelihood of bleeding, though bleeding during heparin therapy is generally infrequent unless invasive procedures are performed or local lesions exist. 1
Duration of Hold and Monitoring
Hold heparin for 1-2 hours for a PTT of 155 seconds, as this allows sufficient time for the anticoagulant effect to diminish given heparin's short half-life of approximately 60-90 minutes. 1, 2
Recheck PTT after 1-2 hours to confirm the value has decreased toward the therapeutic range before restarting the infusion. 1
Resume heparin at a reduced infusion rate (typically decrease by 2-3 units/kg/hour or 200-300 units/hour depending on your institution's protocol) once the PTT falls below 100 seconds. 1
Recheck PTT 4-6 hours after restarting the infusion to ensure therapeutic levels are achieved without overshooting again. 1
Key Monitoring Principles
The therapeutic target aPTT ratio should be 1.5-2.5 times the control value, corresponding to anti-Xa activity of 0.3-0.6 IU/mL. 1
PTT values should not exceed 100 seconds to minimize bleeding risk while maintaining therapeutic anticoagulation. 1
The relationship between excessive PTT prolongation and bleeding complications is well-established, making prompt dose adjustment critical. 1
Common Pitfalls to Avoid
Do not simply reduce the infusion rate without holding the heparin first when the PTT is this elevated, as the anticoagulant effect needs time to diminish. 1
Do not restart at the same infusion rate that caused the excessive prolongation—always reduce the rate by at least 2-3 units/kg/hour. 1
Avoid holding heparin for excessive periods (>4 hours) in patients with acute thromboembolism, as this increases the risk of recurrent thrombotic events. 3
Check for heparin resistance factors if PTT remains difficult to control, including increased binding to plasma proteins, which may require anti-Xa level monitoring instead. 1
Monitor platelet counts every 2 days during heparin therapy to detect heparin-induced thrombocytopenia, particularly between days 4-14 of treatment. 4, 5