Blood Glucose Measurement
Pinprick tests were performed with a 25G needle. After skin punctures were made, the blood glucose level in the flaps was measured using the Medisafe-Mini (Terumo).1 This instrument measures the blood glucose level by a colorimetric determination method that requires only 10 μL of blood.
Blood glucose measurements were performed immediately after the operation, 1 hour after returning to the patient’s room, on the first postoperative day, and on the postoperative day 2 in all flaps. When flap congestion was suspected from gross appearance by an experienced doctor, frequent blood glucose measurement was begun and it was measured every hour. At the same time, countermeasures, such as removing the sutures nearby the pedicle, were performed complying with an algorithm (Fig. 1). If the gross appearance or blood glucose level of flaps improved after the countermeasures, hourly blood glucose measurement resumed until the flaps improved. If the gross appearance or blood glucose level of flaps worsened despite such countermeasures, venous thrombus was suspected, and reexploration was performed. And hourly blood glucose measurement resumed until the flaps improved after the reexploration. At the reexploration, we identified the pedicle of the flap and looked for venous thrombosis. If venous thrombosis was detected, thrombectomy, reanastomosis, and in some cases vein graft transfer were performed. When the bleeding after the pinprick test was insufficient for measuring blood glucose, no congestion was suspected.
RBGC was measured in each flap. RBGC (mg/dl h) was obtained by dividing the change of blood glucose level (mg/dl) by time (h). We defined “congestion point in time” as a moment when flap congestion was suspected in each flap.
For each flap, RBGC was measured beginning from immediately after the operation until postoperative day 2. If reexploration was performed after flap congestion was suspected, RBGC from the congestion point in time to the point in time when the reexploration was performed was measured. If congestion improved as time passed with or without any countermeasures, RBGC from the congestion point to the moment when congestion was improved was measured (Fig. 2).
The RBGCs at the points in time when the venous thrombosis was detected were compared with those at the points in time when the flap demonstrated no venous thrombosis. The former RBGCs were calculated between the point in time when the flaps demonstrated signs of congestion and the point in time just before the reexploration. The latter RBGCs were calculated between the point in time when the flaps demonstrated signs of congestion and the point in time when congestion was improved. RBGCs were divided into 2 groups; Group 1 is the set of the congestion point when a venous thrombus developed or the flap eventually is the set of the time point when no venous thrombus was detected became necrotic. Group 2.
Statistical difference was determined using the χ2 test. A P value less than 0.05 was considered significant. Data were queried using Microsoft Excel (Microsoft Corp., Redmond, Wash.). A cutoff score was determined so that the test would have the highest specificity for the prediction of venous thrombosis.
Of the 36 flaps, 27 flaps showed no signs of congestion postoperatively and completely survived (pattern A), 3 flaps demonstrated signs of congestion but improved without reexploration (pattern B), 4 flaps demonstrated signs of congestion but improved after the reexploration (pattern C), and 2 flaps demonstrated signs of congestion and eventually became necrotic despite the reexploration (pattern D) (Fig. 2). The patients’ demographic information is listed in Table 3.
The flaps with Pattern A demonstrated no signs of congestion, so we obtained blood sample 4 times; immediately after the operation, 1 hour after returning to the patient’s room, in the morning of the first postoperative day, and in the morning of the postoperative day 2. The flaps with Pattern B, C, and D had “congestion point in time,” and we obtained blood sample 3–8 times for each congestion point in time. The number of times we obtained blood sample depends on the case and time to the reexploration.
The flaps with pattern A and B demonstrated no venous thrombosis, whereas those with pattern C and D demonstrated venous thrombosis. The mean RBGCs at the points in time when the venous thrombosis was detected was −7.61 and those at times when the flap demonstrated no venous thrombosis was 0.10, the former being significantly lower than the latter.
Two flaps in pattern D were vascularized lymph node transfers for lower limb lymphedema with using TAP flap. In these flaps, venous thrombus was removed in the reexploration, but the skin paddle remained congested and eventually required debridement.
Seven time points were included in group 1, and 30 time points were included in group 2. The mean RBGC in group 1 was −7.61 and that in group 2 was 0.10. significantly lower than that in group 2 (Fig. 3).
Case 1 (Pattern B)
A 41-year-old male presented with a left lateral nasal wall defect after the adenoid cystic carcinoma resection. Then the secondary reconstructive surgery was performed and the lateral nasal wall defect was reconstructed using a SCIP flap from his left groin.
Although the flap was not congestive and the blood glucose level was 92 immediately after the operation (23:00), the flap became purple and the blood glucose level was 73 in the morning of the first postoperative day (7:00). Because the flap congestion was suspected from the gross appearance and pinprick test, frequent blood glucose measurements were performed every hour, and we took off the suture threads nearby the pedicle to release the pressure on the pedicle. After the countermeasure, the blood glucose level increased hourly, and the color of the flap improved without the reoperation (11:00). At this congestion point in time, RBGC was +2.75 (Fig. 4). The flap survived completely, and the patient was satisfied with the result.
Case 2 (Pattern C)
A 63-year-old female presented with squamous cell carcinoma on the right nasal ala. Following excision of the tumor, a total defect of the right nasal ala remained. Then the secondary reconstructive surgery was performed, and the right nasal ala defect was reconstructed using a free auricular flap from her left ear.
Although the flap was not congestive and the blood glucose level was 112 immediately after the operation (1:00), the flap became purple with the blood glucose level 80 and congestion was suspected in the morning of the first postoperative day (7:00). After we took off the suture threads nearby the pedicle, the color of the flap became darker, and the blood glucose level was 71 (8:00) (Fig. 5). At this congestion point in time, RBGC was −9. The flap congestion due to the venous thrombosis was suspected, and the first reexploration was performed. In the operation, venous thrombus was detected and vein reanastomosis was performed. After the reexploration, the bleeding after the pinprick test was insufficient for measuring blood glucose and the color of the flap improved.
On the postoperative day 5, however, the flap became purple with the blood glucose level 37 and congestion was suspected (Fig. 6). The countermeasure was not taken because there were no threads near the pedicle. The flap became darker with time, and the blood glucose level went down to 23 two hours after the congestion point in time. The RBGC was −4.6 at this congestion point in time. The flap congestion due to the venous thrombosis was suspected, and the second reoperation was performed. In the operation, venous thrombus was detected, and venous reanastomosis and 2 more venous anastomosis were added. After the second reexploration, the color of the flap improved with the blood glucose level increasing and the flap survived completely.
Early detection and rapid reexploration is the key success factors in salvage of a congestive flap. However, defining clinical indications for reexploration is challenging. The result of our study showed that the blood glucose level in the congested flap decreased with time; it kept on decreasing despite any countermeasures in congested flaps with venous thrombus. Therefore, the RBGC measurement is useful for monitoring flaps and helpful to determine reexploration. To the best of our knowledge, this article represents the first use of RBGC measurement for detecting venous thrombosis in clinical practice.
Several studies have reported that congestive flaps showed a decrease in the blood glucose level. In 2010, Sakakibara et al.21 reported the first use of a blood glucose meter for flap monitoring in diabetic patients and a lower blood glucose level in congestive flaps in clinical case.20 In 2011, Hara et al.1 described blood glucose measurement for flap monitoring and reported that the blood glucose level of 62 mg/dl is the best cutoff value for detecting venous thrombosis.21 However, the sensitivity and specificity are not enough for surgeons to determine whether reexploration should be done or not. Actually, we experienced completely survived flaps in which blood glucose level was less than 62 mg/dl. Some flaps showed a blood glucose level higher than 62 mg/dl at 1 time, but later it decreased rapidly, and the flap became congestive because of venous thrombosis.
What’s important is distinguishing temporary congestion due to extrinsic factors such as compression of the pedicle from permanent congestion due to venous thrombus formation. This is because this differentiation directly impinges on surgeons’ decision whether reexploration should be performed or not. For the salvage of temporary congestion due to extrinsic factors such as compression of the pedicle, all we need to do is address the extrinsic factor and reexploration is not necessary. For the salvage of flaps with permanent congestion due to venous thrombosis, on the other hand, the reexploration should be performed. Differentiating these 2 congestive flap statuses based on blood glucose measurement at a point in time is unreasonable. Instead, sequential blood glucose measurement and RBGC calculation with the intervention such as the release of the extrinsic factors are effective. And we found that RBGC smaller than or equal to −4.5 mg/dl per hour was 100% sensitive for venous thrombosis and 100% specific. Thereupon, we propose an algorithm for deciding whether reexploration is necessary in congestive flaps (Fig. 1). Using this algorithm, the salvage rate of congestive flaps due to the venous thrombus would be increased and unnecessary reexploration of flaps could be avoided.
The RBGC method described here has several advantages. First, this method is simple and highly reproducible, which can be performed by residents, nurses, and medical students. Second, it is accurate and reliable. In our study, setting the RBGC cutoff value as −4.5 mg/dl per hour, 100% sensitivity and specificity could be obtained. Third, this method is inexpensive.
On the other hand, this study has several limitations. First, the patients who suffered from diabetics or received insulin were not included. It is uncertain if RBGC method can be used in diabetic patients, since the blood glucose level often fluctuates more than that of nondiabetic patients. Therefore, it may be essential to modify the blood glucose level obtained from the flap of diabetic patients, and further investigations on this study will be needed. Second, various types of flaps were included in this study. It is sure that the patterns of drainage and the tolerance to congestion varies depending on the types of flaps. For example, it is well known that free jejunal flaps are more susceptible to congestion when compared with adipocutaneous flaps. However, with regard to the change of blood glucose level, which is affected by hemodynamics, the diversity of flaps is thought to be acceptable. The paucity of cases is also a limitation of this study, but we believe the statistical significance demonstrates that the RBGC method is useful for detecting venous thrombosis. Further investigations are needed for more precise analysis.
In our study, the rate of flap failure was 5.5% (2 flaps), which was higher than that of previous study.2 The 2 flaps were vascularized lymph node transfers for lower limb lymphedema using TAP flaps. The 2 flaps became necrotic despite the thrombectomy because the diameter of the recipient vein was extremely small. The technique of the vascularized lymph node transfer with TAP flap has not yet been established, and this may be the reason for higher rate of flap failure. However, using this RBGC method, venous thrombosis of these necrotic flaps could be predicted before reexploration. To put it differently, RBGC method can be helpful in detecting congestion in flaps that are still at an early stage in a learning curve.
The RBGC measurement of free tissue transfers provides detection of venous thrombosis with outstanding sensitivity and specificity in clinical cases. RBGC smaller than or equal to −4.5 mg/dl per hour was 100% specific for venous thrombosis. RBGC method is simple, highly reproducible, accurate, reliable, and inexpensive.
1. Hara H, Mihara M, Iida T, et al. Blood glucose measurement for flap monitoring to salvage flaps from venous thrombosis. J Plast Reconstr Aesthet Surg. 2012;65:616–619.
2. Smit JM, Zeebregts CJ, Acosta R, et al. Advancements in free flap monitoring in the last decade: a critical review. Plast Reconstr Surg. 2010;125:117–185.
3. Kroll SS, Schusterman MA, Reece GP, et al. Timing of pedicle thrombosis and flap loss after free-tissue transfer. Plast Reconstr Surg. 1996;98:1230–1233.
4. Yuen JC, Feng Z. Monitoring free flaps using the laser Doppler flowmeter: five-year experience. Plast Reconstr Surg. 2000;105:55–61.
5. Heller L, Levin LS, Klitzman B. Laser Doppler flowmeter monitoring of free-tissue transfers: blood flow in normal and complicated cases. Plast Reconstr Surg. 1999;104:97.
6. Liss AG, Liss P. Use of a modified oxygen microelectrode and laser-Doppler flowmetry to monitor changes in oxygen tension and microcirculation in a flap. Plast Reconstr Surg. 2000;105:2072.
7. Yano K, Hosokawa K, Nakai K, et al. Monitoring by means of color Doppler sonography after buried free DIEP flap transfer. Plast Reconstr Surg. 2003;112:1177.
8. Few JW, Corral CJ, Fine NA, et al. Monitoring buried head and neck free flaps with high-resolution color-duplex ultrasound. Plast Reconstr Surg. 2001;108:709–712.
9. Karkowski J, Buncke HJ. A simplified technique for free transfer of groin flaps, by use of a Doppler probe. Plast Reconstr Surg. 1975;55:682–686.
10. Swartz WM, Izquierdo R, Miller MJ. Implantable venous Doppler microvascular monitoring: laboratory investigation and clinical results. Plast Reconstr Surg. 1994;93:152–163.
11. Jöbsis FF. Noninvasive, infrared monitoring of cerebral and myocardial oxygen sufficiency and circulatory parameters. Science. 1977;198:1264–1267.
12. Irwin MS, Thorniley MS, Doré CJ, et al. Near infra-red spectroscopy: a non-invasive monitor of perfusion and oxygenation within the microcirculation of limbs and flaps. Br J Plast Surg. 1995;48:14–22.
13. Delgado JM, DeFeudis FV, Roth RH, et al. Dialytrode for long term intracerebral perfusion in awake monkeys. Arch Int Pharmacodyn Ther. 1972;198:9–21.
14. Edsander-Nord A, Röjdmark J, Wickman M. Metabolism in pedicled and free TRAM flaps: a comparison using the microdialysis technique. Plast Reconstr Surg. 2002;109:664–673.
15. Machens HG, Mailaender P, Reimer R, et al. Postoperative blood flow monitoring after free-tissue transfer by means of the hydrogen clearance technique. Plast Reconstr Surg. 1997;99:493–505.
16. Dunn RM, Kaplan IB, Mancoll J, et al. Experimental and clinical use of pH monitoring of free tissue transfers. Ann Plast Surg. 1993;31:539–545.
17. Wolff KD, Kolberg A, Mansmann U. Cutaneous hemoglobin oxygenation of different free flap donor sites. Plast Reconstr Surg. 1998;102:1537–1543.
18. Stack BC Jr, Futran ND, Zang B, et al. Initial experience with personal digital assistant-based reflectance photoplethysmograph for free tissue transfer monitoring. Ann Plast Surg. 2003;51:136–140.
19. Hauge EM, Balling E, Hartmund T, et al. Secondary ischemia caused by venous or arterial occlusion shows differential effects on myocutaneous island flap survival and muscle ATP levels. Plast Reconstr Surg. 1997;99:825–833.
20. Kerrigan CL, Wizman P, Hjortdal VE, et al. Global flap ischemia: a comparison of arterial versus venous etiology. Plast Reconstr Surg. 1994;93:1485–1495; discussion 1496.
Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Society of Plastic Surgeons. All rights reserved.
21. Sakakibara S, Hashikawa K, Omori M, et al. A simplest method of flap monitoring. J Reconstr Microsurg. 2010;26:433–434.