Veterinary medicinal leech therapy: Application, monitoring, complications

Figure 1. Venous congestion is the best indication for medicinal leech therapy. Photos courtesy of Dr. Nicole J. Buote.An important aspect of medicinal leech therapy is correctly discerning which patients would benefit from veterinary medicinal leeching and which would not. Edema or cellulitis is not an indication for leech therapy nor is arterial insufficiency, which is indicated by pale, turgid, cold tissue with a prolonged capillary refill time. Venous congestion is the best indication for leech therapy. The tissue will appear purple in color (Figure 1) and will be engorged and warm. Scarce dark blood will come from pricks to the tissue, and the capillary refill time will be brisk.

In human medicine, medicinal leech therapy is contraindicated in immunocompromised patients, patients with bleeding disorders and patients who refuse blood transfusions.

Placing the leeches

Figure 2. The head of the leech is the smaller end and usually attaches first.Before attaching the leeches, prepare the site properly by washing it with gentle soap-at our hospital, we use a chlorhexidine scrub-and rinsing it with saline solution. If there is any soap residue, the leeches will not feed. Leeches are most likely to feed at skin temperatures between 91.4 F and 104 F (33 C and 40 C), so the patient should be in a warm room and the affected area wrapped lightly in gauze or a blanket.

FIgure 3. Generally, a leech's caudal end will attach nearby the head, creating a U shape.Grasp the leech with smooth or nontraumatic forceps and place it on the proposed attachment site. To keep the leech at the site and encourage feeding, you can place the leech inside a syringe casing, with the open end inverted onto the skin and held in place until attachment occurs. The head of the leech is the smaller end and usually attaches first (Figure 2). Generally, the leech's caudal end will attach nearby, creating a U shape (Figure 3). You can also encourage feeding by placing a drop of dextrose or glucose at the proposed site or pricking the skin with a sterile needle so a drop of blood is present. Place enough leeches to allow for full coverage of the congested area. A study using laser Doppler has shown that one leech can decongest and increase perfusion in an approximately 2-cm-square area, which corresponded with the return to normal skin color.1

Monitoring during leeching

Leech migration can occur during or after feeding, especially because it is a leech's instinct to hide after a meal. Careful monitoring should be performed during therapy to ensure that leeches do not travel into open wounds, incisions or healthy tissue. When the leeches are full, they will detach. Never forcibly detach a leech, as teeth may be left behind, becoming a source of infection.

If a leech must be removed before it is done feeding, place a small amount of isopropyl alcohol, saline solution or vinegar on a cotton swab and stroke the leech's head. That will usually cause spontaneous detachment. Applying too much of these liquids may cause regurgitation of the blood into the bite site, increasing the risk of infection, so apply sparingly. Leeching can take from 20 to 120 minutes. The decongestion is usually appreciated quickly after application, with improvement in tissue color and texture and capillary refill time. In human medicine, visual confirmation of decongestion is considered easy, reliable and effective.

After leeching

When the leeches are satiated, they will detach spontaneously. A single leech may extract 5 to 15 ml of blood during the active phase, but the passive oozing after detachment may yield a similar volume. In my experience, applying a soft-padded bandage to the limbs allows for adequate passive bleeding without creating a mess. New leeches are applied when the passive bleeding stops, and the cycle continues until revascularization is confirmed visually (improvement in color).

In human studies, this means leech application may occur every one to eight hours for days to weeks. Because of the identified time frame for inosculation and peripheral neovascularization of a flap, which can begin as early as three days and would ultimately contribute to appropriate venous outflow for flap survival, the recommended length for medicinal leech therapy is seven to 10 days after surgery. As long as there is evidence of venous congestion between leech applications, therapy should continue.

After use, the leeches should be destroyed by being placed in a 70 percent alcohol solution. Placing the leech in a cup with a screw-on lid will decrease the risk of contamination, as the leech will often regurgitate the blood meal during death. After death, the leech should be treated as biohazardous waste. Leeches are not reused on the same patient because usually after a feeding a leech will not want to feed again for weeks. You should never reuse a leech on a different patient for obvious disease contamination prevention reasons.

In human medicine, laboratory testing (complete blood count, prothrombin time, activated partial thromboplastin time) and vital parameter monitoring (heart rate, respiratory rate, capillary refill time) are performed before, during and after leech therapy because of the high incidence of required transfusions. In veterinary medicine, assessing a patient's packed cell volume and total protein concentration before and after treatment would be a minimal database, but more aggressive monitoring should be considered depending on the number of leeches used and the proposed time frame. Objective criteria such as the leech's weight before and after feeding should be considered if concerns about blood loss exist or the client has any financial concerns.

Prophylactic antibiotics are recommended in human and veterinary medicine. Appropriate antibiotic prophylaxis (fluoroquinolones are most commonly recommended) has demonstrated a significant decrease in the chance of infection from the leech, length of hospital stay and potential loss of flap or injured tissue. In some reviews, double coverage (fluoroquinolones and third-generation cephalosporins or aminoglycosides) during therapy and single coverage (fluoroquinolones only) for two weeks after the leeching is reported for better control.2-4

The most commonly mentioned antibiotic class is fluoroquinolones because of the sensitivity of Aeromonas hydrophila to the class, but recent reports have shown resistant strains of bacteria, leading to complications after leeching.3-5 Multiple other bacteria including Serratia marcescens, Proteus vulgaris, Morganella morganii, Aeromonas sobria and Vibrio fluvialis have been reported.2,5,6 Whenever an infection is diagnosed after a leeching, appropriate cultures should be obtained and a second antibiotic added. Recommended choices for the add-on would be third-generation cephalosporins, aminoglycosides, tetracyclines or trimethoprim.

Complications

The major complication cited for leech therapy is infection with leech gut bacteria or surface bacterial flora. The reported incidence of infection ranges from 2 to 36 percent in human medicine. Infection has been negatively associated with flap survival in many reports and leads to longer hospital stays and greater costs. Other complications include local hypersensitivity reactions to the saliva, anaphylaxis, blood loss, migration of the leech to healthy tissue, scarring from the bite, pain, psychosis and prerenal azotemia.2,6-9

The need for blood transfusion during or after leeching therapy depends on the number of leeches used and the length of time the leeching is performed. For small replantations or venous congestion that clears rapidly, blood loss may be minimal, but in some reported human cases, up to 13 blood transfusions have been necessary for certain patients.6,10,11 Other reports illustrate that an average of two to six blood transfusions are needed in 50 to 57 percent of patients.6,10,11 In my experience, blood transfusions are rarely needed in veterinary patients. That is due to the stark difference in the number of leeches used (far fewer) and the number of leeching sessions (also fewer) commonly needed in veterinary patients.

References

1. Conforti MI, Connor NP, Heisey DM, et al. Evaluation of performance characteristics of medicinal leech (Hirudo medicinalis) for the treatment of venous congestion. Plast Reconstr Surg 2002;109(1):228-235.

2. Yantis MA, O'Toole KN, Ring P. Leech therapy. Am J Nursing 2009;109(4):36-42.

3. Giltner CL, Bobenchik AM, Uslan DZ, et al. Ciprofloxacin-resistant Aeromonas hydrophilia cellulitis following leech therapy. J Clin Microbiol 2013;51(4):1324-1326.

4. Patel KM, Svetska M, Sinkin J, et al. Ciprofloxacin-resistant Aeromonas hydrophilia infection following leech therapy: a case report and review of the literature. J Plast Reconstr Aesthet Surg 2013;66(1):e20–e22.

5. Bibbo C, Fritsche T, Stemper M, et al. Flap infection associated with medicinal leeches in reconstructive surgery: two new drug-resistant organisms. J Reconstr Microsurg 2013;29(7):457-460.

6. Whitaker IS, Oboumarzouk O, Rozen WM, et al. The efficacy of medicinal leeches in plastic and reconstructive surgery: a systematic review of 227 reported clinical cases. Microsurgery 2012;32(3):240-250.

7. Green PA, Shafritz AB. Medicinal leech use in microsurgery. J Hand Surg Am 2010;35(6):1019-1021.

8. Mommsen J, Rodriguez-Fernandez J, Mateos-Micas M, et al. Avulsion of the auricle in an anticoagulated patient: is leeching contraindicated? A review and a case. Craniomaxillofac Trauma Reconstr 2011;4(2):61-68.

9. Abdualkader AM, Ghawi AM, Alaama M, et al. Leech therapeutic applications. Indian J Pharm Sci 2013;75(2):127–137.

10. Nguyen MQ, Crosby MA, Skoracki RJ, et al. Outcomes of flap salvage with medicinal leech therapy. Microsurgery 2012;32(5):351-357.

11. de Chalain T, Jones G. Replantation of the avulsed pinna: 100 percent survival with a single arterial anastomosis and substitution of leeches for a venous anastomosis. Plast Reconstr Surg 1995;95(7):1275-1279.