Current techniques in the post-operative monitoring of microvascular free-tissue transfers

An Algorithm for Selecting Buoy Skin Paddle Design for Flap Monitoring in Total Autologous Breast Reconstruction After Nipple-Sparing Mastectomy

Introduction Monitoring buried flaps in reconstructive breast surgery is challenging, and the ideal technique is controversial. Established options include leaving an exterior ("buoy" or "sentinel") skin paddle versus invasive implantable devices to avoid removing the paddle later. Technical modifications and an algorithm for strategic skin paddle positioning to circumvent this while avoiding complex monitoring equipment are proposed. Patients and methods Patients in whom buoy skin paddles were utilized for breast flap monitoring by a single surgeon were reviewed. Indications, demographic details, precise monitoring paddle location, and flap outcomes were evaluated. An algorithm and classification system were then formulated. Results Thirteen buoy skin paddles were utilized in seven patients (mean age: 43.5 years; range: 31-65) to monitor reconstructive flaps performed for risk-reducing mastectomies (four patients and seven breasts), therapeutic mastectomy (one breast), and revision surgery (three patients and five breasts). The flaps comprised seven deep inferior epigastric artery perforators (DIEPs), four superficial inferior epigastric arteries (SIEAs), and two pedicled latissimus dorsi (LDs) (mean free flap weight: 809 g; average mastectomy weight (n = 10 breasts): 467 g; range: 248-864). The skin paddles were located horizontally along the inframammary crease or vertically inferior to the nipple-areola or both. All flap transfers were successful with no re-explorations. All patients declined the monitoring paddle excision, and none have requested breast mound revision for poor cosmesis or contour deformities. Conclusion Vertical and horizontal skin paddles proved reliable for buried flap monitoring without recourse to invasive and expensive equipment. When designed appropriately, they do not require revision surgery. An algorithmic classification of skin paddle location to enable this is proposed.

Quantifying the Limitations of Clinical and Technology-based Flap Monitoring Strategies using a Systematic Thematic Analysis

Background

Multiple techniques exist to monitor free flap viability postoperatively, varying with practical and personal preference, yet the limitations of each technique remain unquantified. This systematic review aims to identify the most commonly reported limitations of these techniques in clinical practice.

Methods

A systematic review was conducted according to PRISMA guidelines using MEDLINE, EMBASE, and Web of Science with search criteria for postoperative free flap monitoring techniques. Search results were independently screened using defined criteria by two authors and a senior clinician. Limitations of the techniques found in the discussion section of eligible articles were recorded and categorized using thematic analysis.

Results

A total of 4699 records were identified. In total, 2210 articles met the eligibility criteria and were subsequently reviewed, with 195 papers included in the final analysis. The most frequently reported limitations of clinical monitoring were interpretation requiring expertise (25% of related papers), unsuitability for buried flaps (21%), and lack of quantitative/objective values (19%). For noninvasive technologies, the limitations were lack of quantitative/objective values (21%), cost (16%), and interpretation requiring expertise (13%). For invasive technologies, the limitations were application requiring expertise (25%), equipment design and malfunction (13%), and cost (13%).

Conclusions

This is the first systematic review to quantify the limitations of different flap monitoring techniques, as reported in the literature. This information may enhance the choice in monitoring strategy for a reconstructive service, and inform the development and refinement of new flap monitoring technologies.

A method for flap monitoring based on bioelectrical-resistance analysis

Axial pattern flaps are characterized by a single vascular pedicle that supplies the whole flap and carry the danger of flap loss. For this reason, monitoring and early identification of vascular perfusion is important for flap prognosis. The most commonly used method for flap monitoring is clinical assessment, but it has certain limitations. The bioelectrical properties of tissues can be affected by ischemic conditions, and a preliminary study showed that the bioelectrical resistance of blood was decreased under thrombotic conditions. In this controlled study, the resistance values of the axial flaps were calculated during thrombosis. A total of 28 rats were randomly divided into a control group (n = 14) and an experimental group (n = 14). Axial flaps were elevated based on the inferior epigastric pedicle. For the ischemic group, microvascular clamps were placed in the ischemic group to produce artificial thrombosis from day 1 of the experiment. Bioelectrical resistance was measured every 30 minutes for the first 6 hours and then daily after that. The resistance values from the ischemic group decreased progressively, and 150 minutes after the clamping, the difference became statistically significant (P < 0.05). The results showed that the assessment of flap resistance is a valuable tool and may allow early recognition of a compromise in the vascular system before clinical signs become obvious.

Postoperative quantitative assessment of reconstructive tissue status in a cutaneous flap model using spatial frequency domain imaging

BACKGROUND

The purpose of this study was to investigate the capabilities of a novel optical wide-field imaging technology known as spatial frequency domain imaging to quantitatively assess reconstructive tissue status.

METHODS

Twenty-two cutaneous pedicle flaps were created on 11 rats based on the inferior epigastric vessels. After baseline measurement, all flaps underwent vascular ischemia, induced by clamping the supporting vessels for 2 hours (either arteriovenous or selective venous occlusions); normal saline was injected into the control flap and hypertonic-hyperoncotic saline solution was injected into the experimental flap. Flaps were monitored for 2 hours after reperfusion. The spatial frequency domain imaging system was used for quantitative assessment of flap status over the duration of the experiment.

RESULTS

All flaps demonstrated a significant decline in oxyhemoglobin and tissue oxygen saturation in response to occlusion. Total hemoglobin and deoxyhemoglobin were increased markedly in the selective venous occlusion group. After reperfusion and the administration of solutions, oxyhemoglobin and tissue oxygen saturation in those flaps that survived gradually returned to baseline levels. However, flaps for which oxyhemoglobin and tissue oxygen saturation did not show any signs of recovery appeared to be compromised and eventually became necrotic within 24 to 48 hours in both occlusion groups.

CONCLUSIONS

Spatial frequency domain imaging technology provides a quantitative, objective method of assessing tissue status. This study demonstrates the potential of this optical technology to assess tissue perfusion in a very precise and quantitative way, enabling wide-field visualization of physiologic parameters. The results of this study suggest that spatial frequency domain imaging may provide a means for prospectively identifying dysfunctional flaps well in advance of failure.

Endoscopic measurements of free-flap perfusion in the head and neck region using red-excited Indocyanine Green: preliminary results

BACKGROUND

Free-tissue transfer has become a standard procedure for reconstructive surgery in the head and neck area. Flap failures are relatively rare (<or=5%), and a high percentage can be salvaged if detected early. Indocyanine Green (ICG) angiography might be able to improve the detection of flap malperfusion at an early stage.

METHODS

So far, 11 patients with free-flap reconstructions of the upper aerodigestive tract (UADT) have participated in this study. Each participant underwent three endoscopic ICG angiographies (24h intra-operatively and 72h postoperatively). The data obtained were evaluated online as well as offline on a personal computer (PC), and the results compared to the clinical outcome.

RESULTS

There were no partial or complete flap losses. One flap was successfully salvaged following initial arterial kinking with impeded perfusion. The ICG fluorescence angiography was tolerated well in all patients. The free flaps showed a delayed yet equal ICG fluorescence as compared to the surrounding tissue. The timing and slope of fluorescence build-up were dependent on circulatory factors. The relative fluorescence maxima of flap versus surrounding were 33% in the initially failing flap and >or=64% for all other examinations.

CONCLUSIONS

It was possible to prove the feasibility of endoscopic ICG fluorescence angiography in patients undergoing free-flap transfer to the UADT. The method provides instant information about the perfusion state of the tissue and is easily performed without greater patient discomfort or risk of side effects. Due to the endoscopic approach, the method seems highly promising for this indication and merits further evaluation.