The instructions for Cathflo are to instill 2 mg/2.2 mL solution into the port-a-cath. Wait 30 minutes, then check for blood return. If there is no blood return, the dose can be repeated in 120 minutes. However, given the reservoir volume and catheter length, 2.2 mL does not seem to be enough volume to reach the tip, thus the sheath/clot. Many facilities still use heparin locks with volumes of 3-5 mL. Would it not be logical to instill that same volume to ensure the medication reaches the clot? The drug does not activate until it touches the clot and is active for only 5 minutes. Are there any reports of using larger volumes? If so, what were the outcomes? —Theresa DeBlasio, BSN

The two COOL studies that validated the efficacy of Cathflo demonstrated at least 88% efficacy after two doses of Cathflo instillation into central venous catheters. The prescribing guidelines do not recommend dosing beyond 2 mg/2 mL per dose of Cathflo, for a maximum of two doses. The outcomes of the studies demonstrated that the volume instilled were more than adequate to return a blood withdrawal of at least 3 mL, and allow for instillation of saline at 5 mL.

The efficacy of Cathflo was not associated with the volume of drug instilled, but the mechanism of action of the medication, which is fibrinolysis. There are no reports of using larger volumes to date given the prescribing guidelines and FDA approval at that dosing. —Jiajoyce R. Conway, DNP, CRNP, AOCNP

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