Post operative monitoring of microvascular breast reconstructions using the implantable Cook-Swartz doppler system: a study of 145 probes & technical discussion.

INTRODUCTION: Accurate post operative assessment of free tissue transfers is challenging despite all the subjective and objective techniques available today. In our continual search to optimise patient outcomes, we introduced the Cook-Swartz probe into our clinical practice in May 2006. METHODS: We present our single centre experience in 103 patients undergoing 121 microvascular breast reconstructions and monitored using implantable Cook-Swartz venous dopplers between May 2006 and January 2008. RESULTS: In total, we used 145 probes on 121 microvascular breast reconstructions (DIEP=102, SIEP=15, SGAP=4) in 103 female patients. The mean operative time was 4h and 55 min (mu=295; range 117-630; ó+/-101 min) and we suffered 2 complete flap losses. A problem with the audible signal was noted in 15 patients (4 intra-operatively). We revised 14 of the 15. All fourteen had compromised anastomoses. In the remaining case, the patient was not returned to theatre as the primary surgeon was confident there were no other signs of vascular compromise. Overall, when using the venous doppler probe we found a false positive rate of 6.7% and 0% false negatives. DISCUSSION: We advocate the use of a Cook-Swartz probe which has been well received by both surgeons, nursing staff and patients, as an adjunct to traditional clinical monitoring techniques. We also include a comprehensive experience based technical discussion concerning its application, attachment, use and post-operative removal.

Use of a modified oxygen microelectrode and laser-Doppler flowmetry to monitor changes in oxygen tension and microcirculation in a flap.

Flap failure is a clinical problem in free tissue transfer, and there is no reliable device for monitoring the tissue. Differentiating between an arterial occlusion and venous congestion is also a problem. A study was undertaken to monitor viability in a pedicled groin flap and to compare two different monitoring methods. The oxygen tension in the flap, measured with a modified Clark-type microelectrode (tip diameter = 3 to 8 microm; 90 percent response within 2.6 +/- 0.5 seconds), was compared with changes in blood flow in the flap, measured with a laser-Doppler probe. In 11 Sprague-Dawley rats, the changes in oxygen tension and blood flow in the pedicled groin flap were studied after clamping and subsequent reperfusion of the artery or vein. After occlusion of the artery to the flap, oxygen tension decreased to a stable value (i.e., the recording level remained unchanged for 30 seconds), from 19.7 +/- 1.8 to 0.3 +/- 0.1 mmHg, after 193 +/-25 seconds; blood flow decreased to a stable value, from 117 +/- 21 to 54 +/- 18 perfusion units, after 26 +/- 6 seconds. Clamping of the vein resulted in a decrease in oxygen tension, from 17.1 +/- 1.8 to 1.4 +/- 0.7 mmHg, after 416 +/- 67 seconds, and blood flow decreased to a stable value, from 90 +/- 14 to 35 +/- 6 perfusion units, after 107 +/- 27 seconds. The results of this study show that there is a difference in oxygen tension and blood flow responses between arterial and venous occlusion and that it may be possible with both methods to distinguish arterial from venous occlusion. However, although oxygen tension measurements are slightly slower in response than laser-Doppler measurements, the values are more reliable as a diagnostic tool for interpretation of a vessel occlusion.

Electric stimulation of a transsected nerve does not seem to prevent loss of sensory neurons: an experimental study in cats.

Injury to a sensory nerve often results in a clinically poor long term outcome, possibly as a result of the extensive loss of neurons within the dorsal root ganglia (DRG), which has been shown in several experimental studies. This loss is possibly caused by interruption of the sensory input and axonal transport in the damaged afferent nerve. To investigate the importance of sensory afferent input into a nerve a pulsed electric stimulation was applied on the proximal part of the superficial radial nerve after transsection and microsurgical repair. The purpose was to simulate nerve impulses and thereby mask the severity of the injury. To test this hypothesis a pilot study was undertaken in eight cats. The neuronal tracer showed that the median neuronal loss was 38% of the neurons of the dorsal root ganglia that received afferents from the nerve investigated, which corresponds to the figure in a previous study in which electric stimulation was not used. Artificial sensory stimulation during regeneration in a transsected and repaired peripheral nerve therefore does not seem to reduce neuronal loss.

Loss of primary afferent nerve terminals in the brainstem after peripheral nerve transection: an anatomical study in monkeys.

In order to investigate the changes in the somatosensory organization that occur after a peripheral nerve injury, a purely sensory nerve (radial nerve - superficial branch) was divided in adult monkeys (Macaca fascicularis). The nerve ends were immediately rejoined by an epineural suturing technique. After 6-21 months the nerve investigated was exposed to an intra-axonal nerve tracer (horseradish peroxidase conjugate) in order to label the primary afferent terminals within the cuneate nucleus of the brainstem. The non-transected nerve on the contralateral side was similarly exposed and served as a control. Terminal labelling was seen throughout the cuneate nucleus, mainly in the middle of its rostro-caudal extension, and in this part it showed a patchy appearance superimposed on cell clusters within the pars rotunda. This pattern of distribution was seen both on the experimental and control sides. On the experimental side there was an obvious loss of terminal labelling within the terminal field as estimated using an image-analysing system: Compared with the contralateral side the median loss (peroxidase activity) was 83% and between 6 and 21 months only minor restoration of the terminal intensity was observed. These results in the primate confirm earlier results in the cat that transection and microsurgical repair of a sensory nerve causes a considerable loss of neurons capable of intraaxonal transport.

Loss of nerve endings in the spinal dorsal horn after a peripheral nerve injury. An anatomical study in Macaca fascicularis monkeys.

In patients, the long-term outcome of injuries to sensory nerves is poor. This is only partly due to mismatching of regenerating axons at the transection site. We found in the macaque monkey that 70% of the transganglionic labelling in the spinal dorsal horn was still significantly reduced 21 months after transection and suturing of the sensory radial nerve. The reduction was evenly distributed throughout the terminal field of nerve endings, which were labelled with a mixture of the intra-axonal nerve tracer wheat germ agglutinin-horseradish peroxidase conjugate and pure horseradish peroxidase.

Loss of neurons in the dorsal root ganglia after transection of a peripheral sensory nerve. An anatomical study in monkeys.

Injury to a sensory nerve often results in a poor long term outcome, partly because of sensory motor mismatch of regenerating axons at the transection site. We studied nine macaque monkeys and found that 27% of nerve cells in the projecting dorsal root ganglia had been lost 21 months after transection and suturing of the radial sensory nerve. No specific cell sizes were lost and the reduction was evenly distributed in the affected ganglia in which neurons had been labelled with a mixture of wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) and HRP alone.

Reorganisation of primary afferent nerve terminals in the brainstem after peripheral nerve injury. An anatomical study in cats.

A pure sensory nerve (the superficial branch of the radial nerve) in adult cats was cut to investigate the changes in the nerve endings (terminals) on the neurons of the nucleus cuneatus of the brainstem. In one group of cats (n = 22) the ends of the cut nerve were approximated immediately by epineural suturing to promote optimum regeneration. In another group (n = 11) the proximals tump of the nerve was enclosed in a capsule to prevent regeneration. Four to 17 months later the same nerve was re-exposed. The sutured nerves were cut and nerve-tracer was exhibited to the proximal end of the cut nerves and to the proximal stump of the nerves which had been encapsulated. The purpose was to investigate the labelling of nerve terminals in the cuneate nucleus, because it receives an input of primary afferents from the front leg. The nerve and the cuneate nucleus of the opposite side served as controls. Labelled terminals were distributed throughout the dorsal part of the entire rostrocaudal extent of the cuneate nucleus. The distribution was patchy and was superimposed on clusters of nerve cells. The quantity of labelled nerve terminals on the experimental and control sides was compared: 60% of the labelling observed on the control side was in the sutured nerves while the encapsulated nerves exhibited only 32%. This difference was apparent 4 months after transection of the nerve. Up to 17 months after the nerve was cut, however, there was some increase in the quantity of labelled nerve terminals and this was most apparent in cats in which the nerves had been sutured.

Changes in the spinal terminal pattern of the superficial radial nerve after a peripheral nerve injury. An anatomical study in cats.

The occurrence of changes within the spinal cord over a long period after a peripheral nerve injury was investigated in adult cats. The lateral superficial branch of the radial nerve was exposed and transsected unilaterally. In one group the nerve endings were re-approximated with epineural sutures and in the other group the proximal nerve stump was enclosed to prevent regeneration. After a survival period of 4-17 months the same nerve on both sides was exposed to an intra-axonal nerve tracer, lectin-conjugated horseradish peroxidase, to label the nerve terminals within the spinal gray matter by transganglionic transport. The general distribution of the terminal field was almost the same after suturing as after encapsulation of the transsected nerve, except for a slightly more cranial location of the terminal area after suturing compared with the control side. The terminal area comprised laminae I-IV of the fifth cervical to the first thoracic spinal segment, concentrated towards the sixth to eighth cervical segments. This distribution was the same as on the control side, but the experimental and control sides differed in intensity of terminals. There was a loss of terminals throughout the terminal field in both operated groups, but after nerve suture there was some recovery of terminal intensity between 4 and 17 months after the injury.

Cell loss in sensory ganglia after peripheral nerve injury. An anatomical tracer study using lectin-coupled horseradish peroxidase in cats.

In 33 adult cats the lateral superficial branch of the radial nerve was exposed and transsected on one side. In one group of animals (n = 22) the nerve-stumps were re-approximated with epineural sutures and in the other group (n = 11) the proximal nerve stump was enclosed to prevent regeneration. After survival periods ranging from 4-17 months the same nerve on both sides was exposed to an intra-axonal nerve tracer to label the dorsal root ganglion neurones projecting into the nerve being investigated. In each animal the opposite side was used as control. When the transsection was followed by a nerve suture the mean proportion of labelled sensory neurones in the dorsal root ganglion, compared with the control side, was 61% at eight months after operation, but by 17 months it had increased to 70%. When regeneration was prevented by the proximal nerve stump being enclosed in a plastic envelope, the reduction in labelled cells was 45% after a survival period of 17 months.

Mechanisms of injury and prognosis in finger pulling--a retrospective study.

Eighteen patients were treated for finger pulling injuries between 1977 and 1986. There were two main types of injury, subcutaneous rupture of the flexor profundus tendon (n = 15) and fracture of the proximal phalanx of the finger (n = 3). Their mechanisms of injury were different. The prognosis in tendon ruptures is comparable to that in other open flexor tendon injuries. Age and distal localization were associated with a poorer prognosis in younger patients. Fractures healed well.