Flap Blood Glucose as a Sensitive and Specific Indicator for Flap Venous Congestion: A Rodent Model Study

Flap blood glucose measurement for flap monitoring and early detection of circulatory problems

Postoperative monitoring of skin flaps is subjective and cannot detect early circulatory problems in the flap. Early detection and rapid remedial re-exploration are important for flap salvage. We evaluated flap glucose measurement to monitor the flaps for early detection of circulatory problems. In total, 30 patients underwent cutaneous flap reconstruction. This is an easy, economic, objective, and reliable method for flap monitoring and can detect early venous congestion requiring remedial measures.

Flap Monitoring Using Interstitial Fluid Glucose Measurements

Background: Various flap monitoring techniques have been used in the early detection of anastomotic thrombus; however, the use of automatic and continuous monitoring methods is presently uncommon. The purpose of this study was to investigate trends in interstitial fluid glucose concentration (IFG) in flap monitoring by measuring IFG automatically and continuously. Methods: Nine patients underwent unilateral breast reconstruction using a transverse rectus abdominis myocutaneous flap with vascular anastomosis. Two IFG measuring devices were attached to each patient. One device was attached to the flap (flap IFG) and the other to the healthy breast (control IFG). In each case, flap IFG, control IFG, and IFG ratio (flap IFG/control IFG) were recorded in the initial 72 h post-surgery (first half) and also in the subsequent 72 h (second half). In all of the cases, the mean values recorded in the first half and those in the second half were compared. Results: All flaps survived. The flap IFG didn't fall below 40 mg/dL in the first half. The minimum flap IFG and IFG ratio were 42 mg/dL and 0.55 in the first half. The flap IFG was significantly higher in the first half than in the second half in all cases, and the IFG ratio was similar in 8 cases. Furthermore, mean flap IFG and mean IFG ratio in all cases in the first half were significantly higher than in the second half. Conclusions: IFG measurements may complement conventional flap monitoring, particularly in the early postoperative period.

Predictors, management and prognosis of initial hyperemia of free flap

In free flap operation, temporary hyperemia of the transferred flaps can often be encountered in the early postoperative period, appearing reddish and rapid capillary refilling time, which mimics venous congestion. This study aimed to investigate the factors associated with the development of hyperemia and evaluate clinical course. Consecutive patients who underwent free flap-based reconstruction between December 2019 and October 2021 were reviewed. Independent risk factors associated with its development were assessed. Flap showing initial hyperemic features were assessed using flap blood glucose measurement (BGM). If it showed over 60 mg/dL, they were closely observed without management. Their clinical outcomes were evaluated. In total, 204 cases were analyzed, of which 35 (17.2%) showed initial hyperemia. Multivariable analyses showed that using thoracodorsal artery perforator flaps and muscle containing flaps (musculocutaneous/muscle-chimeric flaps) and conducting end-to-end arterial anastomosis (vs. end-to-side) were independent predictors. All cases with initial hyperemia showed over 60 mg/dL in BGM. The phenomenon resolved spontaneously within 6.9 h averagely. Overall perfusion-related complications developed in 10 (4.9%) cases, which rate did not differ between the two groups. Several factors might be associated with the development of initial hyperemia after free flap surgery. With proper assessment, this condition can be successfully managed without unnecessary intervention.

Selective Application of Blood Glucose Monitoring After Free Flap Surgery: Potential Indications in Real-World Practice

BACKGROUND

For free-flap monitoring, physical examination still serves as the criterion standard. Blood glucose measurement (BGM) has been suggested to be useful in identifying flap perfusion status. Nonetheless, its routine use may not be cost-effective in real-world settings. This study aimed to share the experiences of using BGM for flap monitoring and suggest its potential indications.

METHODS

Of cases of free flap reconstruction conducted between March 2017 and May 2021, those using BGM for flap monitoring were reviewed. Blood glucose measurement was selectively conducted for the following specific situations, which included encountering a flap showing a reddish discoloration and/or rapid capillary refilling time in the immediate postoperative period, monitoring discolored flaps after conducting a salvage operation, and conducting bloodletting therapy for salvaging congestive flaps. The clinical course and outcomes were evaluated.

RESULTS

Of a total of 203 cases, 35 used BGM for flap monitoring in addition to clinical examination. In 29 cases, BGM was performed to distinguish early hyperemia from true venous insufficiency. All flaps showed BGM greater than 60 mg/dL with a mean value of 115.42, suggesting early hyperemia, and had uneventful postoperative courses. In 3 cases with already discolored flaps after a salvage operation, BGM was conducted 4 times serially every 3 hours and showed a mean value of 81.6 mg/dL with increasing trends. The flaps recovered completely. In the other 3 cases requiring bloodletting therapy, BGM was conducted an average of 11 times at a median interval of 7 hours. The bloodletting therapy was terminated with reference to the value of BGM when it showed greater than 60 mg/dL while the therapy was on hold. All flaps were successfully salvaged except one showing partial necrosis.

CONCLUSIONS

Blood glucose measurement may be helpful in assessing flap perfusion and decision making in certain clinical situations and may be useful as an ancillary tool for flap monitoring. Selective application of BGM may contribute to achieving optimal outcomes.

The correlation of flap blood glucose with fat necrosis of free abdominal flap for unilateral breast reconstruction

BACKGROUND

Flap blood glucose (FBG) measurement is proposed as a monitoring technique. A cause of long-lasting fever could be derived from fat necrosis. If the findings of low FBG correlated with fat necrosis, it could predict the poor cosmetic result and a source of fever. However, this correlation remained unsolved. The purpose of this study was to clarify this correlation in breast reconstruction.

METHODS

In the 180 unilateral breast cancer patients (mean age = 49.8 years) performed free abdominal flap, we retrospectively compared the group where fat necrosis occurred with the group where it did not occur (45 patients with fat necrosis vs. 135 patients without). We compared the average of FBG in each postoperative day.

RESULTS

The average FBG was significantly lower in patients with fat necrosis in the second postoperative day (115.3 ± 27.3 vs. 126.3 ± 13.7 mg/dl, p = .026) and the third postoperative day (111.1 ± 22.1 vs. 118.8 ± 13.8 mg/dl, p = .036). Mean BMI and inserted total flap weight were significantly higher in patients with the fat necrosis group (24.8 vs. 22.9 kg/m² , p = .005) (617 vs. 478 g, p = .006). The multivariate analysis revealed early FBG (OR = 0.96, p = .0002) and laterality (right side) (OR = 0.46, p = .043) were independently significant predictors. There were no significant between-group differences regarding other factors (age, systemic blood glucose, comorbidities and operative details).

CONCLUSIONS

The possibility of fat necrosis was high for patients with low FBG in the early postoperative day.

Continuous Interstitial Glucose Measurement for Flap Venous Occlusion Monitoring in a Diabetic Model

ABSTRACT

Glucose has been used in the monitoring of transplanted flaps. However, few studies have focused on the effect of diabetes on the decrease in flap glucose levels. The purpose of this study was to evaluate the application of continuous interstitial glucose monitoring to detect flap venous occlusion in a diabetic rat model. The flap interstitial glucose level was measured by transcutaneous sensors in the bilateral vertical rectus abdominis myocutaneous flaps of each rat. interstitial glucose values in the bilateral flaps were recorded every 5 minutes after the venous occlusion of 1 flap. Forty-one rats were divided into the control group (n = 13), diabetic group (n = 15, established by the intraperitoneal injection of streptozotocin), and insulin-treated diabetic group (n = 13, systemic glucose well controlled by insulin before surgery). Results indicated that flap interstitial glucose decreased to the lowest level in all flaps with venous occlusion. The time from venous occlusionto the lowest interstitial glucose level was significantlylongerinthe diabetic group than the control group (120.8 ± 5.7 minutes versus 56.5 ± 6.7 min-minutes, P < 0.001), but was similar in the insulin-treated diabetic and control groups (56.5 ± 6.7 minutes versus 56.0 ± 6.6 minutes, P = 0.876). The change in interstitial glucose in both the diabetic and insulin-treated diabetic groups began with a plateau period or a slow decline before decreasing for 49.0 ± 6.4 minutes and 24.4 ± 4.3 min-minutes, respectively. in a diabetic rat model, impaired glucose metabolism prolongs the required monitoring time and dulls the reaction of flap interstitial glucose to venous congestion. Insulin restores the prolonged monitoring time, but not the reaction of flap interstitial glucose. Therefore, care is needed during application of the technique in diabetic patients.

Using blood glucose and lactate levels for early detection of venous congestion following a free flap procedure for lower extremity open fractures

PURPOSE

Gustilo-Anderson type IIIB and IIIC open fractures of the lower extremities require reconstruction of extensively injured soft tissues using a free flap; however, impaired blood flow through the flap is an early postoperative complication. To detect flap congestion due to venous thrombosis, blood glucose and lactate level measurements within the flap are taken to determine variations in these levels. We aimed to detect early-stage venous congestion and to perform salvage operations.

METHODS

We included 22 limbs with lower leg and foot open fractures, with fracture sites covered using a free flap. A pinprick test was used to measure blood glucose and lactate levels.

RESULTS

Of 7 and 15 congested and non-congested limbs, respectively, the 7 congested limbs had a mean flap blood glucose level immediately before salvage surgery of 3.8 ± 2.0 (7.4-1.8) mmol/L. The ratio to blood glucose levels in healthy fingertips was 0.6 ± 0.2 (0.8-0.3). Lactate levels increased to 13.3 ± 5.1 (9.4-22.8) mmol/L. The ratio of blood glucose levels in congested flaps and in healthy fingertips was significantly lower than that in non-congested flaps and in healthy fingertips (p = 0.0016). Lactate levels were significantly higher in patients with congestion (p = 0.0013). Salvage surgery was performed, thrombi were removed, and six limb flaps were viable.

CONCLUSION

Flap blood glucose and lactate levels provide a quantitative method of evaluating blood flow and detecting flow abnormalities postoperatively, and are useful in detecting early congestion due to venous thrombosis.

Protective effects of dexmedetomidine on the survival of random flaps

BACKGROUND

Random flaps can be used to repair wounds and improve shape and functional reconstruction, but inflammation and necrosis limit their application. Modified McFarlane flap models were constructed on the backs of rats. We hypothesized that dexmedetomidine (DEX) could improve the survival rate of ischemic random flaps.

METHODS

Sixty rats were randomly divided into three groups: a low-dose DEX group (DEX-L group, 10 μg/kg/D), a high-dose DEX group (DEX-H group, 20 μg/kg/D) and a control group (0.9 % saline equivalent). On day 7 after flap construction, the survival percentage of the flap model was calculated. Hematoxylin and eosin staining (H&E) was used to evaluate the histopathological status of the flaps and microvessel density (MVD). Lead oxide/gelatin angiography was used to detect angiogenesis, and laser Doppler flow imaging (LDF) was used to detect blood perfusion. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in the middle areas of the flaps were measured to show the level of oxidative stress. The expressions of Toll-like receptor (TLR4), nuclear factor-kappa B (NF-κB), interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and vascular endothelial growth factor (VEGF) were detected by immunohistochemistry.

RESULTS

DEX significantly increased the average survival percentage of the flaps and reduced ischemia and necrosis of the distal end of the flaps. SOD activity significantly increased, while MDA significantly decreased, indicating that DEX reduces oxidative damage. The expression of inflammatory immunoregulatory proteins (TLR4, NF-κB) was downregulated, and the levels of inflammatory factors (IL-1β, IL-6 and TNF-α) were lower. In addition, DEX upregulated VEGF expression, promoted angiogenesis, and increased blood perfusion.

CONCLUSION

In random flap transplantation, a high dose of DEX is beneficial to flap survival.