Examqo › Examqo library › Plastic surgery › Principles: grafts, flaps and microsurgery
Free flaps and microsurgery — monitoring and salvage
A free flap usually fails because of thrombosis at the anastomosis, which occurs mostly in the first 48 to 72 hours — mainly venous thrombosis — so frequent monitoring and a rapid return to theatre are what save the flap.
Why it matters in the exam
Free flap failure in experienced centres is about 1 to 5%. Clinical monitoring checks colour, capillary refill (about 2 to 3 seconds), turgor, temperature and pinprick bleeding; handheld Doppler, implantable Doppler or near-infrared spectroscopy (NIRS) are added. Venous congestion — a purple, swollen flap, brisk capillary refill and dark pinprick bleeding; arterial insufficiency — a pale, cold flap, slow refill and no bleeding. Any such change requires immediate return to theatre: salvage rates are high when intervention comes within hours. When venous drainage cannot be restored, medicinal leeches (Hirudo medicinalis) remove blood and secrete hirudin; they carry Aeromonas hydrophila, so prophylaxis such as ciprofloxacin or TMP-SMX is given.
Intraoperative vasospasm is treated with warming, irrigation and topical drugs such as lidocaine, papaverine or verapamil. The "no-reflow phenomenon" appears after prolonged ischaemia — flow does not return despite a patent anastomosis. Muscle is the tissue least tolerant of ischaemia, while skin and fat are more tolerant. Supercharging is an extra anastomosis joining a flap vessel to a recipient vessel beyond the flap, and turbocharging is connecting a second pedicle of the flap to its own pedicle — both improve flow in large flaps. Common free flaps: ALT (from the lateral circumflex femoral artery's descending branch), radial forearm (thin, long pedicle, requires an Allen test), fibula (peroneal artery, for jaw reconstruction), DIEP (breast), latissimus and gracilis. Smoking, obesity, previous radiation and vascular disease raise risk.
Key points
- Most thromboses in the first 48 to 72 hours.
- Venous commoner than arterial.
- Congestion — purple, brisk, dark blood; arterial — pale, slow, no blood.
- Leeches — Aeromonas; prophylaxis.
- Supercharging — an additional anastomosis to a recipient vessel.
Summary table
| Situation | Colour and turgor | Capillary refill and bleeding | Action |
|---|---|---|---|
| Healthy flap | Pink, normal turgor | 2 to 3 seconds, red blood | Monitoring |
| Venous congestion | Purple, swollen | Brisk, dark blood | Theatre; leeches when repair is impossible |
| Arterial insufficiency | Pale, flaccid, cold | Slow or absent, no bleeding | Immediate theatre |
| Intraoperative vasospasm | — | Reduced flow | Warming, lidocaine, papaverine, verapamil |
| No-reflow | — | No flow despite a patent anastomosis | Prevention: shorten ischaemia time |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Plastic surgery, General surgery, ENT and head and neck surgery, Orthopedic surgery.
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- Plastic Surgery (Neligan), 5th edition (2023) — Principles of microsurgery and flap monitoring
- Wei and Mardini, Flaps and Reconstructive Surgery, 2nd edition (2017) — Free flap monitoring and salvage
- American Society of Reconstructive Microsurgery guidance on medicinal leech therapy, current — Indications and antibiotic prophylaxis
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.