We would like to congratulate Holzle et al. on their long-term study involving the use of simultaneous laser-Doppler flowmetry and tissue spectrophotometry in the postoperative monitoring of 166 consecutive flaps . Such studies of postoperative monitoring devices are difficult to compile, requiring a standardized approach to patient selection and monitoring protocols. While many features of this study will prove highly useful in both clinical practise and research, there are a number of points in the study which we feel warrant discussion.

While a major benefit of the study is the thorough analysis of the subjective benefits of this monitoring technique, to truly test the efficacy of a monitoring technique an objective assessment of outcome measures must be undertaken. The authors state in the abstract and in the text of the article that 12 of 24 compromised free-flaps were taken back to theatre for revision on the basis of monitoring, and that nine of these were successfully salvaged. However on closer reading of the results, the raw data is less clear and we would like to explore the data for clarification. Careful analysis of the text actually suggests that 17 flaps were returned to theatre, with only six successful revisions. Our reading of the text is as follows:

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  Sixteen flaps with diagnosed venous compromise on clinical monitoring, of which nine were taken back to theatre. All seven non-operative cases survived, and five of the nine re-explored cases were salvaged.

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  Three flaps were diagnosed with arterial compromise, of which one flap was salvaged.

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  Five flaps were in a ‘mixed’ arterial and venous compromise group, none of which were salvaged.

Further clarification of the exact sequence of events by the authors would be greatly appreciated.

We also think that any prospective monitoring technique needs to be analysed in terms of its ability to change clinical outcomes and optimize clinical decision making. The ideal measures with which to identify flap monitoring success are the flap salvage rate, defined as the proportion of flaps salvaged out of the total number of compromised flaps regardless of whether they were revised or not (but not including flaps that survived with no intervention, such as the seven congested flaps that were left alone in this study), and the false positive rate, which is defined as the proportion of non-compromised flaps that the monitoring technique identifies as compromised but where no anastomotic problem has occurred. While neither of these measures were addressed in the article by Holzle et al., it is possible to calculate them from their results, with an overall salvage rate calculated at 35% (6/17 flaps) and a false positive rate of 0%, as it appears from the text that a positive monitoring result was always associated with a definite cause.

The salvage rate of 35% with the use of simultaneous laser-Doppler flowmetry and tissue spectrophotometry does not compare favourably with literature values , and does not advocate the use of this technique. However, these low results may be related to a number of factors, which may make it difficult to comment upon the success or otherwise on this monitoring technique. It is necessary to compare the salvage rate of this technique with the salvage rate for a similar group of flaps (preferably performed by the same surgeons) where clinical monitoring only was used. Unfortunately such results are not forthcoming. It is interesting to note that this technique did reduce the overall take-back rate, with seven clinically compromised flaps that would otherwise have been re-explored, identified as healthy by the technique. The cost savings associated with this reduction should not be underestimated.