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Ann Thorac Surg 2003;75:1171-1174
© 2003 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, Royal Brompton and Harefield NHS Trust, London, United Kingdom
b Cardiac Medicine, National Heart and Lung Institute, Faculty of Medicine, Imperial College, London, United Kingdom
Accepted for publication November 11, 2002.
* Address reprint requests to Professor Collins, Cardiac Medicine, National Heart and Lung Institute, Faculty of Medicine, Imperial College, Dovehouse St, London SW3 6LY, UK
e-mail: peter.collins{at}ic.ac.uk
| Abstract |
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METHODS: Twenty-three patients with negative Allens test of the nondominant forearm were recruited preoperatively and underwent assessment of bilateral forearm function (soft touch and pin-prick neural sensation, circumference, handgrip power, cyclical exercise fatigue) and blood flow measurements (forearm plethysmography). All vasoactive drugs were stopped 24 hours before assessments. Identical follow-up assessments were conducted (mean ± SEM) 3.4 ± 0.4 months postoperatively.
RESULTS: At the time of postoperative assessment all harvested forearm wounds were healed. There was no reduction of postoperative soft touch sensation but in 3 patients objective pinprick sensation was reduced in the distribution of the lateral antebrachial cutaneous nerve of the harvested forearms. Postoperative forearm circumference (p < 0.05) and grip power (p < 0.05) were significantly reduced in both forearms, however cyclical exercise fatigue was improved in both forearms. Preoperative and postoperative forearm blood flow at rest and in exercise-induced ischemic reperfusion were not significantly different in both forearms.
CONCLUSIONS: In patients with a negative Allens test, harvesting of the radial artery does not adversely affect subsequent forearm function or blood flow to a clinically significant degree.
| Introduction |
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| Patients and methods |
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Patients underwent preoperative bilateral forearm function and FBF assessment on the day of admission. All patients completed the study, with a postoperative assessment at 3.4 ± 0.4 months. All vasoactive medications were stopped 24 hours before surgery.
Neural sensation
Objective neural sensation assessment was made with soft touch and pinprick sensations using cotton wool and pin, respectively [4].
Forearm circumference, handgrip power, and exercise fatigue
Forearm circumference was measured at the proximal third of the forearm between the antecubital crease and styloid process. Handgrip power was measured as the maximal voluntary contraction (MVC), assessed by patients gripping hard on a strain gauge, that provides a percentage of each grip. Sensitivity of the strain gauge was set and recorded for each patient as a reference for the postoperative assessment. Mean MVC was calculated after three measurements. Exercise fatigue was assessed with the patients cyclically gripping the strain gauge to a targeted visual force level (50% of MVC) for 6 seconds and then rested for 4 seconds [5]. Each patient repeated this 10-second cycle until they could no longer attain the targeted force level. The time in seconds was recorded as the duration of cyclical exercise fatigue.
Forearm blood flow
Forearm blood flow was measured by venous occlusion plethysmography, as previously described [6]. Briefly, patients rested supine in a quiet room at constant ambient temperature of 22oC for 15 to 30 minutes before FBF measurements were started. A blood pressure cuff was placed on the upper arm and inflated to 40 mm Hg with a rapid cuff inflator (D.E. Hokanson Model E-10; Bellevue, WA) to occlude venous outflow from the extremity. The resultant increase in forearm volume was measured with a mercury-filled silastic strain gauge placed around the proximal third of the forearm. The strain gauge was connected to a plethysmograph (D.E. Hokansen Model EC-4; Bellevue, WA) that was connected to a paper chart recorder (Multitrace 2; Lectromed, Jersey, Channel Islands) and the measurements were analyzed. Three resting base line FBF were measured. Patients then underwent forearm cyclical exercise until fatigue as described above, with a 2-minute period of ischemia immediately upon fatigue. Ischemia was induced by inflating the upper arm blood pressure cuff to a minimum of 40 mm Hg above systolic pressure. Blood flow (mL/100 mL/min) was measured immediately after cuff deflation and again at 1 and 5 minutes of reperfusion. Three measurements were obtained at each time period and the mean FBF was then calculated. Heart rate and systemic blood pressure were monitored for the study duration (Dinamap; Critikon, Tampa, FL).
Data analysis
All data were analyzed as within patient comparisons of preoperative with postoperative forearm function and FBF. Differences are presented as mean ± SEM and analyzed using paired Students t test. Data from the contralateral arm of each patient were used as individual controls. A p value less than 0.05 was considered significant.
| Results |
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Forearm circumference, handgrip power, and exercise fatigue
Forearm function measurements are shown in Table 1.
Contralateral forearms were significantly larger than the harvested forearms at both assessment periods (preoperative, p = 0.0004, and postoperative, p = 0.002). There was a significant reduction in postoperative forearm circumference in both forearms. (p < 0.05). Although no patients complained of any significant change in handgrip power the measured MVC in both the harvested and contralateral forearms was significantly reduced (p < 0.05). Postoperatively, exercise fatigue was improved in the contralateral forearm by 44% (p = 0.01) and by 20% in the harvested forearm (p = 0.25). There was no difference in mean MVC (preoperative, p = 0.10; postoperative, p = 0.11) and cyclical exercise fatigue (preoperative, p = 0.38; postoperative, p = 0.86) between the harvested and contralateral forearms.
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| Comment |
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The few available published data describing hand power and circulation changes are conflicting and do not correlate well with clinical observations [9, 10]. We observed a significant reduction in objective handgrip power of the harvested forearm. As similar degrees of reduction were also seen in the contralateral forearms, we concluded that this may be related to decreased use after surgery rather than to removal of the RA artery alone.
Further evidence supporting this was the small but significant reduction in forearm circumference observed in both forearms at the postoperative assessment. Significant reduction in thenar flexor power postoperatively has also been reported [9]. The clinical significance of these early findings is uncertain as none of the patients in our study complained of any subjective weakness in handgrip power. Cyclical exercise fatigue was not affected by the removal of RA and tended to improve at postoperative assessments. This may be due to the overall reduction in the mean MVC observed allowing the patients to perform longer cyclical handgrip exercise.
Our data indicate that removal of the RA does not reduce early postoperative FBF. This is not surprising as the blood flow to an organ, in this case the forearm, is not determined by the number of conduits present but by the cardiac output. We have also shown that the postoperative FBF tended to increase in the harvested forearm compared with the contralateral forearm, although this was not significant. The trend increased at 5 minutes of reperfusion compared with preoperative flow, indicating a prolonged duration of vasodilatation. This increase in flow has been shown to be the result of dilatation in the remaining vasculature [2, 11, 12]. The prolonged vasodilatation may be due to the delay in clearing of ischemic metabolites through collateral vessels in the harvested forearm.
Although the overall FBF or inflow to the hand does not appear to be reduced, other studies report a small but statistically significant decrease in digital blood flow after RA harvesting, particularly in the thumb and index finger [2, 1315]. Others have shown a reduction in tissue perfusion of the hand and forearm but no change in hand function [16]. The clinical significance of this is uncertain as patients studied did not complain of any subjective disabilities. Ischemic claudication is also unlikely to occur, however the data are conflicting.
In conclusion, RA harvesting in patients with a negative modified Allens test does not adversely affect early forearm function or FBF responses.
| Acknowledgments |
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| References |
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