A simple and effective method of monitoring free muscle transfers: a preliminary report

Techniques of postoperative blood flow monitoring after free tissue transfer: an overview

Ever since free tissue transfer has been established in microsurgery, success rates have greatly improved over the years, partly due to improved technical performance of microvascular anastomoses with better optical and instrumental aids. However, flap failure still occurs in 5-10%, mainly due to blood vessel thrombosis within the first 24 postoperative hours. Salvation rates of failing free tissue transfers can be optimized by in-time diagnosis of irreversibly compromised tissue blood flow and immediate operative reexploration. Therefore, there is a special demand for adequate and reliable postoperative monitoring techniques. This article gives an overview of all monitoring techniques, which have been performed both in the experimental and clinical setting thus far.

Tissue oxygen tension measurement for monitoring musculocutaneous and cutaneous flaps

In pigs, latissimus dorsi musculocutaneous island flaps and buttock skin island flaps were raised. Subcutaneous (PscO2) and intramuscular oxygen tension (PimO2) were measured using a non-heated needle electrode before, during and after repeated occlusion of the supplying artery or the draining vein. During arterial and venous occlusion, the tissue oxygen tension in the musculocutaneous flap dropped rapidly. A plateau was reached after 15 min. After arterial occlusion the mean value was 20 mmHg (SEM = +/- 5 mmHg, N = 6) in the subcutis and 16 mmHg in the muscle (SEM = +/- 4 mmHg, N = 10). After venous occlusion the mean value was 11 mmHg (SEM = +/- 3 mmHg, N = 6) in the subcutis. In the skin flap the drop of PscO2 was slower, and after 30 min of arterial occlusion the mean value was 29 mmHg (SEM = +/- 9 mmHg, N = 6). This study has shown that tissue oxygen tension measurement can be used as a sensitive indicator of acute impairment of the supplying vessels in island flaps. The method seems to have potential for monitoring free tissue transfers. A comparable decrease in PscO2 was found for arterial and venous impairment.

An electrophysiological method for monitoring blood flow in skeletal muscle. An experimental study in the rat

An experimental animal model was used to study the effects of occlusion of skeletal muscle blood flow on spontaneous denervation activity (fibrillation potentials). The aim was to investigate whether recording of fibrillation potentials could provide a valuable electrophysiological technique for monitoring muscle tissue circulation during free flap surgery. In both the fast-twitch anterior tibial muscle and the slow-twitch soleus, the number of fibrillation potentials decreased rapidly (within 30 sec) after occlusion of the blood flow and after 5 min only few fibrillation potentials were present. In the fast-twitch muscle, the fibrillation potentials disappeared within 10 min in most animals, but sporadic potentials were seen for up to 18 min in one animal after the blood vessels were clamped. In the slow-twitch muscle, sporadic single fibrillation potentials were seen for a longer time than in the anterior tibial muscle and fibrillation potentials were often observed for more than 20 min after clamping of the blood vessels. However, the initial decrease in the number of fibrillation potentials was rapid in both muscles. This means, if the same is true in human muscle, that the method is sufficiently rapid to permit restoration of the circulation so that the muscle flap can be saved if the blood flow is occluded after a muscle transfer operation. Thus, recording of fibrillation potentials may provide a powerful and simple technique for monitoring free flap circulation.

Postoperative monitoring of microsurgical free tissue transfers for head and neck reconstruction

Approximately 10% of free tissue transfers fail because of thrombosis of the arterial or venous anastomoses. Postoperative monitoring to allow early detection of impaired flap perfusion is crucial, especially in head and neck reconstruction, in which failure of a free flap may be associated with significant morbidity. Furthermore, the increasing use of "buried" free tissue transfers in the head and neck precludes direct clinical observation. The various techniques that have been advocated for clinical monitoring of free tissue transfers are reviewed, and their potential applications in head and neck reconstruction are discussed with specific emphasis on the use of low-frequency continuous-wave Doppler surface monitoring and implantable high-frequency pulsed ultrasonic Doppler monitoring.

The muscle twitch monitor: a rapid unequivocal method of monitoring free muscle transfers

A free latissimus dorsi muscle transfer, which required anastomotic revision on two occasions within twenty-four hours of operation, illustrates how the change in response of electrically induced muscle contraction to ischaemia can be used as a rapid and sensitive method of monitoring free muscle transfers. It is a response that has the great merit of being easily recognised by untrained observers because it relies on an absolute rather than a relative change in the measured modality. Furthermore it is not influenced by the clinical condition of the patient or by changes in the flap's environment. Its potential is discussed.

Continuous subcutaneous tissue pH measurement as a monitor of blood flow in skin flaps: an experimental study

A miniaturised glass pH probe that makes possible the continuous measurement of subcutaneous tissue pH is described. This instrument has been evaluated as a monitor of blood flow in experimental skin flaps. A rapid fall in tissue pH in response to either arterial or venous occlusion was observed. The results suggest that this technique may be a useful method of monitoring microvascular free flaps.