Evaluation of tests for predicting the viability of axial pattern skin flaps in the pig

Routine Laser-assisted Indocyanine Green Angiography in Immediate Breast Reconstruction: Is It Worth the Cost?

Background:

Laser-assisted indocyanine green angiography (LAIGA) has been proven to accurately detect mastectomy skin flap necrosis (MSFN) intraoperatively and prevent postoperative complications in breast reconstruction. The purpose of this study was to examine the cost-effectiveness of the routine use of LAIGA in immediate breast reconstruction and to perform a break-even point analysis.

Methods:

This is a retrospective review of prospectively gathered data from all patients who underwent immediate breast reconstruction from January 2014 to January 2015. LAIGA was routinely used in all cases. Patients were followed for at least 90 days to capture postoperative complications. Costs were calculated by reviewing itemized bills and Medicare Reimbursement Current Procedural Terminology codes to assess surgeon fees. Outcomes and costs were compared with a historical cohort of patients who underwent breast reconstruction before the implementation of LAIGA.

Results:

Two-hundred-and-six immediate breast reconstructions (126 patients) were performed using LAIGA for a total cost of $210,700. The average cost of MSFN in our LAIGA cohort was $30,496. The routine use of LAIGA decreased the MSFN rate from 12.4% to 6.3% and prevented MSFN on 13 breasts resulting in a gross cost savings of $396,453, and net savings of $185,753. Break-even point analysis demonstrated that number of cases needed to break even decreases as the average MSFN cost and MSFN reduction rate increase.

Conclusion:

The routine use of LAIGA in immediate breast reconstruction is cost-effective in reducing the incidence of MSFN, implant loss, and overall unexpected reoperation rate.

Sedimentation of formed elements in distally ischaemic flaps

Our aim was to find out whether thrombosis has a key role in distally ischaemic flaps and whether heparin improves flap survival in distally ischaemic myocutaneous and pure skin flaps in pigs. In experiment 1 we measured the concentration of coagulation factors in the venous effluent from both viable flaps and distally ischaemic flaps. In experiment 2 radioactively labelled blood components (red cells, platelets and fibrinogen) were injected intravenously and the distribution of each tracer was measured. In experiment 3 either heparin or saline was given as a local, continuous direct intra-arterial infusion. Fluorescein was used in all experiments to estimate the eventual flap survival. Our results indicate that thrombosis is not an important factor in distal ischaemia, and that heparin did not improve survival. Instead, there seems to be selective pooling of formed elements in the ischaemic portion of the flap.

Increased skin flap survival and arterial dilation by calcitonin gene-related peptide. A study in the pig

Calcitonin gene-related peptide (CGRP), a recently discovered neuropeptide, is a potent vasodilator and increases blood flow in many vascular beds. The effect of CGRP treatment was investigated in critical pig pedicle and island flaps. Prior to pharmacological treatment the peroperative circulation border was estimated with fluorescein. Intradermal or intraarterial flap treatment with CGRP was given. Control flaps were untreated or injected with saline. Increased or decreased survival was calculated as the difference between the peroperative fluorescein penetration border and the survival border one week after surgery. CGRP treatment significantly increased the survival of both random pedicle and island flaps. CGRP doses as low as 3 ml x 10(-14) M (equal to 0.03 fmoles) increased the survival of random pedicle flaps. In 4 untreated pigs the deep circumflex iliac arteries were excised and artery ring preparations were studied in vitro. A dose-dependent relaxation of artery rings was noted between 10(-9) M and 10(-7) M CGRP.

Assessment of the viability of skin grafts

A number of tests are available to monitor the blood flow in free and distant pedicle skin grafts. The information from these tests aids in the development of measures to enhance vascularization and is occasionally needed to make clinical decisions in patients with distant pedicle grafts. Measurements of the disappearance of an intradermally injected small amount of 133Xe allows determination of a clearance rate and blood flow before and after clamping the original blood supply through the base. With 99mTc, which is generally more readily available, a flow index and block index can be determined. Clinically both procedures give equally good results in determining a safe time for pedicle base separation. The fluorescein test allows assessment of regional blood flow distribution within the pedicle.

Assessment of the fluorescein dye test for prediction of skin flap viability in pigs

The visual fluorescein dye test for prediction of actual skin flap viability was evaluated in pigs. Two delayed random (4 X 10 cm) and arterial (4 X 20 cm) skin flaps were constructed on one flank of a pig, and four mirror-image skin flaps were raised acutely on the other flank of the same pig. Sodium fluorescein dye (15 mg/kg) was injected intravenously 1 and 18 hr after raising of flaps. The maximum length and area of dye stain in these flaps (N = 24) were assessed under Wood's lamp illumination, 15 min after dye injection. The actual maximum lengths and areas of skin survival of these flaps in the same pig were measured 7 days postoperatively. It was observed that visual fluorescein dye test performed 1 hr after surgery significantly (P less than 0.05) underestimated the maximum length and area of actual skin survival. On the other hand, when the fluorescein dye test was performed 18 hr postoperatively, the maximum length of dye stain and the maximum length of actual skin viability were highly correlated (r = 0.97, N = 24, P less than 0.01). Their mean values were similar (10.6 +/- 0.8 vs 10.8 +/- 0.7 cm, mean +/- SEM), and their mean coefficient of variation was 5.6 +/- 1.6%. Similarly, there was a high degree of correlation (r = 0.89, N = 24, P less than 0.01) between the maximum area of dye stain and actual skin flap viability. Their mean values were similar (68.3 +/- 4.5 vs 71.8 +/- 3.9%), and their mean coefficient of variation was 8.7 +/- 2.4%.(ABSTRACT TRUNCATED AT 250 WORDS)

Venous outflow obstruction in myocutaneous flaps: changes in microcirculation detected by the perfusion fluorometer and laser Doppler

The effects of venous occlusion on the perfusion of porcine myocutaneous groin flaps were studied by means of the laser Doppler and the dermofluorometer. A consistent decrease in fluorometer readings following venous clamping with rebound to original or greater levels after unclamping was noted. A similar pattern was noted in laser Doppler studies. However, flow as measured by the Doppler remained significant (greater than 100 mV) even with venous outflow occlusion. It is hypothesized that the Doppler is more prone than the dermofluorometer to reflect non-nutritive flow in the flap during the early period following flap construction and, therefore, may be less accurate in the evaluation of actual flap microperfusion. The fluorometer was determined to be the more desirable instrument in monitoring the microcirculatory status of myocutaneous flaps during the immediate period after flap elevation and transposition.

A pig model for investigation of muscle and myocutaneous flaps

An experimental model in the pig is described which readily enables studies to be made on musculocutaneous and muscle flaps. The model allows easy, reliable control over the pedicle blood supply at any time in the postoperative period.

Fluorometric assessment of skin flap viability in the rat: effect of radiation therapy

The fluorescein test is widely used to assess perfusion in skin flaps but tends to underestimate skin viability when visual inspection under ultraviolet light is employed. Fiberoptic dermofluorometry, which has recently been introduced, more accurately assesses fluorescein distribution in skin flaps than does visual inspection. Viability of the back flap in rats receiving ionizing radiation was evaluated by dermofluorometry. This technique was highly accurate in predicting viability and has great applicability for studying blood flow in irradiated tissues.

Transcutaneous PO2 monitoring for assessing viability and predicting survival of skin flaps: experimental and clinical correlations

Rectangular skin flaps based on the right superficial epigastric vessels were designed on the groins of 36 rats. Preoperative control, intraoperative, and postoperative readings of oxygen tension (PO2) were made at proximal, central, and distal sites on the flaps with a transcutaneous PO2 (tcPO2) monitor under various conditions of oxygen inspiration. The results of this experimental work indicated that the tcPO2 monitor was useful in continuously and rapidly measuring changes in oxygen concentration in skin flaps in a noninvasive fashion. The monitoring demonstrated that the response time of the flaps to changes in the concentration of inspired oxygen was rapid (less than 15 seconds). The monitoring also was valuable in assessing viability of the flaps, in predicting flap survival, and in detecting any systemic factors influencing oxygen transport, such as pneumonia. As a result of the experimental series, tcPO2 monitoring was used clinically to evaluate 18 flaps in 16 patients. As in the experimental series, the clinical measurements were significant and reproducible. They demonstrated that the tcPO2 monitor provides safe, reliable monitoring of peripheral oxygenation in the microcirculation that is rapid, continuous, and totally noninvasive. It is concluded that simultaneous tcPO2 measurements at control and flap sites provides a continuous record of the status of a flap that can improve the postoperative management of the surgical patient.

The assessment and enhancement of skin flap viability

One of the most difficult tasks facing the reconstructive surgeon is the successful transfer of skin flaps. Despite recent dramatic advances in the application of skin flaps and despite the skill and experience of the surgeon, flaps still fail. This review discusses the methods regarded as most accurate in assessing skin flap viability, and the techniques used to augment flap survival.