Leech therapy: when once is not enough.

Venous congestion is a constant threat in the survival of free flaps, pedicled flaps, tissue replantations and traumatized tissue. Leech therapy has proved effective in salvaging much of these compromised tissues. To be effective, leeches must be both readily available and hungry, requirements not always easily met. Our investigation seeks to establish a means to return sated leeches to their previous unfed, hungry state for reuse. Sated leeches were purged of their blood meals by placement in 3% hypertonic saline or by gentle finger pressure, then exposed to serotonin 0 microM (control), 10 microM, 30 microM or 90 microM for 20 min. Subsequent rebiting/refeeding was observed and analysed. Leeches bathed in serotonin rebit or reattached at nearly four times the rate of unexposed leeches; 30% vs 8% respectively. Biting, however, is not refeeding. Overall, 41 leeches were treated with serotonin with four (10%) refeeding. Those that refed consumed a significantly smaller blood meal than the initial feeding; 50% +/- 47% SD vs 348% +/- 143% SD of original body weight. None of the control group refed. As a method for routinely reusing leeches, serotonin bathing cannot be recommended. In the immediate postoperative period with the sudden emergence of venous congestion requiring leech therapy, but with an inadequate number available, this 20% [corrected] refeed rate after 10 microM serotonin exposure could potentially determine the success or failure of the flap/replantation until fresh leeches are made available.