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

Expert Consensus Statement on the Perioperative Management of Adult Patients Undergoing Head and Neck Surgery and Free Tissue Reconstruction From the Society for Head and Neck Anesthesia

The perioperative care of adult patients undergoing free tissue transfer during head and neck surgical (microvascular) reconstruction is inconsistent across practitioners and institutions. The executive board of the Society for Head and Neck Anesthesia (SHANA) nominated specialized anesthesiologists and head and neck surgeons to an expert group, to develop expert consensus statements. The group conducted an extensive review of the literature to identify evidence and gaps and to prioritize quality improvement opportunities. This report of expert consensus statements aims to improve and standardize perioperative care in this setting. The Modified Delphi method was used to evaluate the degree of agreement with draft consensus statements. Additional discussion and collaboration was performed via video conference and electronic communication to refine expert opinions and to achieve consensus on key statements. Thirty-one statements were initially formulated, 14 statements met criteria for consensus, 9 were near consensus, and 8 did not reach criteria for consensus. The expert statements reaching consensus described considerations for preoperative assessment and optimization, airway management, perioperative monitoring, fluid management, blood management, tracheal extubation, and postoperative care. This group also examined the role for vasopressors, communication, and other quality improvement efforts. This report provides the priorities and perspectives of a group of clinical experts to help guide perioperative care and provides actionable guidance for and opportunities for improvement in the care of patients undergoing free tissue transfer for head and neck reconstruction. The lack of consensus for some areas likely reflects differing clinical experiences and a limited available evidence base.

Intraluminal Monitoring of Micro Vessels. A Surgical Feasibility Study

Objective: Monitoring of vessel perfusion is of high clinical importance in vascular anastomosis of free flaps. Current sensor systems are based on different principles and show limitations in validity and accuracy. Fiber optic pressure sensors exhibit high accuracy and are small in size. The aim of the present study was to evaluate the surgical feasibility of intraluminal pressure (ILP) measurements with a fiber optic pressure sensor in an animal model. Methods: In a microsurgical setting we sedated 10 Wistar rats with weight adapted phenobarbital, xylazine, and fentanyl. We performed a surgical approach to A. carotis communis and V. jugularis and introduced a 600 μm fiber optic pressure sensor into the vessels followed by measuring the ILP. The sensor was stabilized by the surrounding tissue, and the vessels were closed. Results: In all cases, surgical placement was uneventful. Measurement of intra-venous and intra-arterial pressure was possible and stable over the whole measurement period of an hour. Conclusion: Fiber optic pressure measurement in microvessels is possible and surgically feasible. An application to monitor the perfusion of free flaps seems possible.

Current Techniques for Postoperative Monitoring of Microvascular Free Flaps

Free tissue transfer (FTT) is used in patients with complicated reconstructive needs; it can provide stable wound coverage, improved aesthetic appearance, and restore functional deficits. Despite the high success rates of free flaps, vascular occlusion is a significant risk leading to flap failure. Many studies have demonstrated that the salvage rate for flaps is inversely related to the time between onset of a vascular problem and its surgical correction. As a result, ongoing postoperative monitoring of free flaps for adequate perfusion is imperative to allow timely and accurate diagnosis of vascular compromise. Close monitoring and prompt notification of the physician if vascular compromise occurs are typically undertaken by first-line nurses. We conducted an integrative literature to identify and evaluate commonly used techniques for monitoring vascular free flaps during the postoperative period. We searched PubMed and Science Direct electronic databases, using the key words: "free-flap" and "monitoring." This article discusses commonly monitoring modalities, along with their advantages and limitations. Whereas large academic institutions may have an experienced nursing staff specifically trained in effective methods for monitoring free flap patients, this situation may not exist in all hospitals where free flap surgeries are performed. We describe techniques that allow easy and timely detection of flap compromise by nursing staff while reducing interuser variability.

Implantable Doppler monitoring of buried free flaps during vascularized lymph node transfer

BACKGROUND AND OBJECTIVES

Reliable flap monitoring is crucial to the success of free tissue transfer, including vascularized lymph node transfer (VLNT). However, no large-scale study has examined implantable Doppler monitoring in VLNT. We aimed to determine whether an implantable Doppler system can reliably monitor flap perfusion during VLNT and also to calculate the sensitivity and specificity of this system for detecting compromise in the monitored vessel.

METHODS

An analysis of prospectively collected data of patients who underwent buried VLNT with implantable Doppler monitoring between 2014 and 2015 was performed.

RESULTS

A consecutive series of 100 patients underwent VLNT with implantable Doppler monitoring. Five cases required return to the operating room for flap exploration due to a change in Doppler signal quality. All compromised flaps were salvaged. The sensitivity of the implantable Doppler system for flap monitoring was 100%, the specificity was 97.9%, the positive predictive value was 60%, and the negative predictive value was 100%. The false-positive rate was 2%.

CONCLUSIONS

This is the largest reported series of implantable Doppler monitoring of free flap perfusion during VLNT. Our experience suggests that this is a safe and effective technique for postoperative monitoring of VLNT.

Do adjunctive flap-monitoring technologies impact clinical decision making? An analysis of microsurgeon preferences and behavior by body region

BACKGROUND

Multiple perfusion assessment technologies exist to identify compromised microvascular free flaps. The effectiveness, operability, and cost of each technology vary. The authors investigated surgeon preference and clinical behavior with several perfusion assessment technologies.

METHODS

A questionnaire was sent to members of the American Society for Reconstructive Microsurgery concerning perceptions and frequency of use of several technologies in varied clinical situations. Demographic information was also collected. Adjusted odds ratios were calculated using multinomial logistic regression accounting for clustering of similar practices within institutions/regions.

RESULTS

The questionnaire was completed by 157 of 389 participants (40.4 percent response rate). Handheld Doppler was the most commonly preferred free flap-monitoring technology (56.1 percent), followed by implantable Doppler (22.9 percent) and cutaneous tissue oximetry (16.6 percent). Surgeons were significantly more likely to opt for immediate take-back to the operating room when presented with a concerning tissue oximetry readout compared with a concerning handheld Doppler signal (OR, 2.82; p < 0.01), whereas other technologies did not significantly alter postoperative management more than simple handheld Doppler. Clinical decision making did not significantly differ by demographics, training, or practice setup.

CONCLUSIONS

Although most surgeons still prefer to use standard handheld Doppler for free flap assessment, respondents were significantly more likely to opt for immediate return to the operating room for a concerning tissue oximetry reading than an abnormal Doppler signal. This suggests that tissue oximetry may have the greatest impact on clinical decision making in the postoperative period.

Sympathetic innervation does not contribute to glycerol release in ischemic flaps

BACKGROUND

Extracellular glycerol as detected by microdialysis has been used as a surrogate marker for (ischemic) tissue damage and cellular membrane breakdown in the monitoring of free microvascular musculocutaneous flaps. One confounding factor for glycerol as a marker of ischemic cell damage is the effect of lipolysis and associated glycerol release as induced by sympathetic signalling alone. We hypothesized that extracellular glycerol concentrations in a microvascular flap with sympathetic innervation would be confounded by intact innervation per se as compared to denervated flap. Clinical relevance is related to the use of both free and pedicled flaps in reconstructive surgery. We tested the hypothesis in an experimental model of microvascular musculocutaneal flaps.

METHODS

Twelve pigs were anesthetized and mechanically ventilated. Two identical rectus abdominis musculocutaneal flaps were raised for the investigation. In the A-flaps the adventitia of the artery and accompanying innervation was carefully stripped, while in the B-flaps it was left untouched. Flap ischemia was induced by clamping both vessels for 60 minutes. The ischemia was confirmed by measuring tissue oxygen pressure, while extracellular lactate to pyruvate ratio indicated the accompanying anaerobic metabolism locally.

RESULTS

Intramuscular and subcutaneal extracellular glycerol concentrations were measured by microdialysate analyzer. Contrary to our hypothesis, glycerol concentrations were comparable between the two ischemia groups at 60 minutes (p = 0.089, T-test).

CONCLUSIONS

In this experimental model of vascular flap ischemia, intact innervation of the flap did not confound ischemia detection by glycerol. Extrapolation of the results to clinical setting warrants further studies.

Eight-year experience of the Cook-Swartz Doppler in free-flap operations: microsurgical and reexploration results with regard to a wide spectrum of surgeries

BACKGROUND

Microvascular free flap has become an increasingly popular useful method of reconstruction over the past few decades. Minimizing failure rates in these operations is a primary goal in every microsurgical unit that can be accomplished by early recognition.

METHODS

In this retrospective study, we tracked the admission of the implantable Doppler in the microsurgical unit (2000-2007) and evaluated parameters measured from 473 consecutive patients who underwent a total of 548 microsurgical procedures (489 primary surgeries and 59 reexplorations). The effectiveness of the Cook-Swartz Doppler (Cook Medical®) was examined in juxtapose general and subspecialty's aspects: in each microsurgical subspecialty, we compared the overall success and failure rates of the group with the implantable Doppler (n = 259) with the control group monitored by clinical means (n = 289). We also examined the duration, outcomes, and the effectiveness of this device in reexploration operations.

RESULTS

Overall, success rates were improved by using the implantable Doppler contrary to clinical assessment (96.14% vs. 89.27%) with a statistical significant (P < 0.005). The device was most effective in ENT (94.6% vs. 84%), breast reconstructive surgeries (97.3% vs. 82.36%), and orthopedic oncology (97.37% vs. 83.72%), whereas with reanimation operations and trauma/orthopedics subspecialties, it showed no necessity. In neurosurgery and in other/esthetic surgeries, the study was too small to draw definite deductions.

CONCLUSIONS

We recommend the usage of the implantable Doppler probe as an effective monitoring system for free-flap surgeries, with emphasis on subspecialties where the device demonstrated better results than traditional monitoring methods.

In vivo monitoring of microvessels in skin flaps: introduction of a novel technique

Orthogonal polarization spectral (OPS) imaging was validated against intravital fluorescence microscopy (IFM) for microvascular measurements in skin flaps of hairless mice. Examinations were performed 1, 6, and 24 hours after elevation (n = 8) with both OPS imaging and IFM. A fluorescent dye was a prerequisite for IFM measurements but not for OPS imaging. Our findings show that OPS imaging can visualize the skin flap microcirculation independent from the application of fluorescent tracers. From these images, quantitative analysis of functional capillary density (FCD) was feasible. As expected, FCD was significantly lower in the distal part of the flap compared with its base (171.8 +/- 34.7 versus 62.0 +/- 25.6, mean +/- SD; 1 hour data). Comparison of OPS imaging and IFM revealed a significant correlation of FCD values (P < 0.001) at all time points. Given the success of this validation study on mouse skin flaps, clinical investigations will have to prove that OPS imaging can also successfully be used to monitor flaps in humans.

Power Doppler imaging in preoperative planning and postoperative monitoring of muscle flaps

PURPOSE

We assessed the utility of power Doppler imaging (PDI) in preoperative planning and postoperative evaluation of microvascular tissue transfers.

METHODS

Twenty-five PDI studies were performed on 23 patients using a 5-10-MHz linear-array transducer. Thirteen patients were assessed preoperatively for patency of the desired donor vessel; 8 of them had surgical scars overlying the desired vascular territory. Twelve patients (including 2 from the first group) were evaluated postoperatively for patency of the vascular anastomoses and adequacy of the blood supply to the transferred tissue.

RESULTS

Twelve of the 13 patients assessed preoperatively had successful flap transfers. Four of the 8 patients with scars over the desired vascular territories had absent or aberrant arteries, necessitating a change in the operative plan. None of these patients had operative complications. Eight of the 12 patients scanned postoperatively had patent anastomoses. In 2 of these patients, impending surgery was averted when the adequacy of the tissue blood supply was established with PDI. In 4 patients, PDI showed arterial or venous compromise, which was confirmed at surgery.

CONCLUSIONS

PDI is a useful technique in microsurgical tissue transfer for assessing the patency of desired donor vessels preoperatively and for postoperative evaluation of blood supply.

Colour flow duplex scanning: an accurate, non-invasive technique for preoperative evaluation of the vascular supply of the rectus abdominis myocutaneous flap

Forty patients were examined with colour Doppler to study the vascularization of rectus abdominis myocutaneous flaps before operations. The accuracy of this non-invasive ultrasound technique allowed us to describe the characteristics of the blood flow, including volume and velocity, diameter of vessels and their transverse section area within the epigastric arteries which supply the superior and inferior vascular pedicles of the flap. Vessels are drawn on the skin surface so that the flap can be more precisely and rapidly dissected. We are now using colour Doppler to assess variations in the diameter of vessels and in other variables of blood flow within the vascular pedicle of the transferred flap. These evaluations before and after operation are a great help to the reconstructive surgeon in the choice of operation and will lead to an appreciable reduction in postoperative morbidity.