Asian Cardiovasc Thorac Ann 2000;8:224-226
© 2000 Asia Publishing EXchange Pte Ltd
Radial Artery Flows: Comparative Study
Manickam Palaniappan, MD,
Rajani Sundar, MD,
Balakrishnan Soundaravalli, MD,
Anil C Mathew, PhD,1,
Elayappan Krishnan, MS, MCh,
Padmanabhan Chandrasekar, MS,
Srinivasan Muralidharan, MCh
Department of Anaesthesiology and Cardiothoracic Surgery
G Kuppuswamy Naidu Memorial Hospital
Coimbatore, India
1 Department of Community Medicine
P.S.G. Institute of Medical Science and Research
Coimbatore, India
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For reprint information contact: Manickam Palaniappan, MD Tel: 91 422 56 5433 Fax: 91 422 21 3509 email: drpal{at}eth.net 19 10th Cross Street, Thirumagal Nagar, Peelamedu Pudur, Coimbatore 641004, India.
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Abstract
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Between December 1997 and February 1999, 150 patients who had the left radial artery as one of the conduits for coronary artery bypass graft surgery were randomly divided into 3 groups of 50 each. Group A received a left supraclavicular block with 20 mL of 1.5% lidocaine with adrenaline (1 in 200,000), and 10 mL of 0.25% bupivacaine. Group B received intravenous diltiazem at 0.5 to 1 µg•kg–1•min–1 after induction and during radial artery harvest. Group C received neither the block nor diltiazem. Radial artery blood flow was measured for 20 seconds and compared between the 3 groups. All patients received diltiazem by infusion in the postoperative period for 24 hours. Radial artery take-down was abandoned in one patient in group B. There was one in-hospital death. No ischemic complication of the hand was noted. There was a statistically significant difference in mean blood flow between group B (39.20 mL/20 sec) and group C (28.84 mL/20 sec). Group A flow (34.08 mL/20 sec) was also higher than group C, but this was not statistically significant. The results advocate the use of either supraclavicular block or intravenous diltiazem during radial artery harvest.
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Introduction
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With the advent of measures to prevent vasospasm, the radial artery has reemerged as a conduit for coronary artery bypass grafting (CABG), probably as the next best to pedicled internal mammary artery. Radial artery was used as a conduit for CABG by Carpentier and colleagues1 in 1971, but soon abandoned because of poor immediate results revealed by postoperative coronary angiography. It was later reinvestigated because of unexpectedly good long-term results.2 Radial artery being a muscular limb artery of functional classification type III, is prone to spasm and this was thought to contribute to the poor immediate results.3 The availability of a supraclavicular block with resultant sympathetic blockade, as well as parenteral antispastic drugs, prompted us to compare the effects of each on radial artery flow. This prospective randomized clinical study was designed to assess and compare the effects of a left supraclavicular block and intravenous diltiazem on left radial artery flow.
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Patients and Methods
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Between December 1997 and February 1999, 150 patients who had the left radial artery as one of their conduits for CABG were randomly assigned to one of the three study groups. Approval was obtained from the hospital's ethics committee and informed consent was obtained from each patient. Preoperative demographics are given in Table 1
. All patients had a preoperative Allen's test and when in doubt, a pocket Doppler device was used. Standard general anesthesia with an endotracheal tube, using midazolam, fentanyl, vecuronium, N2O:O2 (60:40) and isoflurane tailored to individual need was used. In addition, group-A patients received a left supraclavicular subclavian perivascular block after eliciting paresthesia prior to induction of general anesthesia with 20 mL of 1.5% lidocaine with adrenaline (1 in 200,000) and 10 mL of 0.25% bupivacaine. Group-B patients received diltiazem by infusion at 0.5 to 1 µg•kg–1•min–1 soon after induction of general anesthesia. Group C (control group) received neither the block nor diltiazem.
Atraumatic harvesting of the left radial artery was carried out at the same time as left internal mammary artery take-down. When dissection of the radial artery was complete, it was trial clamped to ascertain whether collateral circulation was adequate. The radial artery was divided at the level of the wrist and pre-heparinized antegrade blood flow was measured for 20 seconds. The radial artery was then divided proximally and the free graft was placed in a bowl containing 25 mL of the patient's blood, 10 mg of diltiazem, 2.5 mg of nitroglycerin, 500 units of heparin, 0.2 mL of 7.5% sodium bicarbonate, and 300 mL of Ringer's lactate solution. At no time was probing or hydrostatic dilatation resorted to. Surgery was performed under cardiopulmonary bypass and anastomosis was carried out using intermittent crossclamping. After cardio-pulmonary bypass, all patients received diltiazem by infusion at 0.5 to 1 µg•kg–1•min–1 for 24 hours.
Statistical analysis was performed using SPSS software (SPSS, Inc., Chicago, IL, USA). A proportion test (Z test) was used to compare proportions, and analysis of variance was used to compare mean values between the 3 groups. Comparison of means was undertaken by the least significant difference method. A p value of less than 0.05 was considered statistically significant.
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Results
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From the preoperative demographics (Table 1
), it can be seen that the risk factors were comparable between groups A, B, and C, and the differences were not statistically significant. The mean radial artery flow in each group is shown in Table 2. The least significant difference, obtained by analysis of variance was found to be 7.5 mL/20 sec. Any value above this was considered to be statistically significant. It can be seen that the mean blood flow was significantly higher in group B than group C. Although the mean flow was higher in group B than in group A, this difference was not statistically significant. Similarly, the mean blood flow in group A was higher than in the control group but the difference was not statistically significant. As far as possible, hemodynamic parameters were optimized close to mean values just prior to measurement, with resort to inotropic agents if necessary; dobutamine was used at 2 to 10 µg•kg–1•min–1. Heart rate, mean arterial pressure, and number of patients on preoperative calcium channel blockers are listed in Table 3. Except for a higher mean heart rate in the control group, all other parameters were comparable. Autologous blood was collected from 10 patients in group A, from 1 in group B and from 2 in group C. It is interesting to note that fewer patients in group A (that had more significant left ventricular dysfunction) needed inotropic support compared to group B.
Radial take-down was abandoned in one patient from group B because the collateral circulation was found to be inadequate intraoperatively. This patient was excluded from the study and group B had only 49 patients for flow measurements. There were no ischemic complications of the left hand in the study groups. There was one in-hospital death in group A; the patient could not be weaned from cardiopulmonary bypass, in spite of all supportive measures.
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Discussion
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The pedicled left internal mammary artery continues to be the graft of choice for CABG and it is currently recommended that all CABG patients should receive an internal mammary artery graft unless there is a contra-indication. On the basis of superior long-term results with internal mammary artery, other arteries have been used in CABG; radial artery is one such conduit currently used.4 Essentially, there is no age limit for the use of the radial artery, although it is generally used in patients younger than 70 years.5 Size is usually not a concern as far as radial artery is concerned, as it is larger than other arterial conduits.
The number of patients with significant left ventricular dysfunction was higher in group A than group B. Surprisingly, there was almost double the number of patients who needed inotropic support with dobutamine before going on cardiopulmonary bypass in group B compared to group A. The adrenaline present in the lidocaine solution was not considered to contribute to this effect. On the contrary, it was speculated whether diltiazem might have a depressant action.
The incidence of spasm during harvesting may also be related to technique. Although atraumatic harvesting with gentle manipulation may reduce the incidence of spasm, there is no evidence that spasm can be totally avoided by gentle harvesting without pharmacological intervention. 6 Parenteral antispastic agents have been a key factor in the revival of the radial artery as a conduit for CABG. A well-prepared graft should function more efficiently than a spastic feeble one. Our study has clearly shown that mean radial artery flows were superior in both groups A and B compared to the controls. Supraclavicular block would be a suitable alternative during radial artery take-down in a hemodynamically unstable patient or when diltiazem is contraindicated. We strongly advocate the use of either a supraclavicular block or intravenous diltiazem during radial artery take-down, followed by diltiazem infusion in the postoperative period.
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References
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Acar C, Jebara VA, Portoghese M, Beyssen B, Pagny JY, Grare P, et al. Revival of the radial artery for coronary artery bypass grafting. Ann Thorac Surg 1992;54:652–60.[Abstract]
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He GW, Yang CQ. Comparison among arterial grafts and coronary artery. An attempt at functional classification. J Thorac Cardiovasc Surg 1995;109:707–15.[Abstract/Free Full Text]
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Acar C, Ramsheyi A, Pagny JY, Jebara V, Barrier P, Fabiani JN, et al. The radial artery for coronary artery bypass grafting: clinical and angiographic results at five years. J Thorac Cardiovasc Surg 1998;116:981–9.[Abstract/Free Full Text]
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Barner HB, Johnson SH. The radial artery as a T-graft for coronary revascularization. Oper Tech Card Thorac Surg 1996;1:117–36.
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He GW. Arterial grafts for coronary artery bypass grafting. Biological characteristics, functional classification and clinical choice. Ann Thorac Surg 1999;67:277–84.[Abstract/Free Full Text]
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Abstract
Introduction
