Observational study of the efficacy of supraclavicular brachial plexus block for arteriovenous fistula creation.

BACKGROUND AND AIMS: Arteriovenous (AV) fistula surgery is commonly performed for AV access for hemodialysis. However the ideal anaesthetic technique of choice remains debated. We aimed to assess operative conditions, vascular patency, and complication rate following AV fistula surgery with isolated brachial plexus block among end-stage renal disease (ESRD) patients.
METHODS: This prospective, observational study included 214 patients undergoing AV fistula surgery under isolated supraclavicular brachial plexus block between January and December 2017. The diameters of the vessels both before and after the block, and the patency of the AV fistula in the immediate postoperative period and after 3 months were assessed using ultrasound Doppler. The change in the vessel diameter both before and after block was compared using independent sample t-test.
RESULTS: The mean brachial artery diameter increased by 0.09 mm (P = 0.002), and cephalic vein diameter at elbow, radial artery, and cephalic vein at wrist diameters increased by 0.5 mm (P < 0.001), 0.08 mm (P = 0.031), and 0.48 mm (P < 0.001), respectively. Overall, 93.45% had immediate patency, 85.51% had primary, and 47.19% had functional patency at 3 months. In the brachiocephalic group, 96.24% had immediate patency, 87.21% had primary, and 27.06% had functional patency at 3 months. Among the radiocephalic group, 91.35% had immediate patency, 82.71% had primary patency, and 71.60% had functional patency at 3 months.
CONCLUSION: Ultrasound-guided isolated brachial plexus block results in good vasodilation and achieves good immediate and long-term patency in AV fistula surgery.

INTRODUCTION

Following the “fistula fist” recommendation by the national vascular access improvement initiative,[1] arteriovenous (AV) fistula surgery has become the most common surgical procedure performed to achieve AV access for hemodialysis. Among the different modalities of anaesthesia, ultrasound-guided brachial plexus block has been reported to achieve better vasodilation[23] and improve operating conditions[4] and postoperative fistula functioning.[5] Standard recommendations have not evolved to guide the choice of anaesthesia in these patients due to a scarcity of studies. Hence, the current study was conducted to assess the operative conditions, vascular patency, and complication rate following brachial plexus block in end-stage renal disease (ESRD) patients undergoing AV fistula surgery.

METHODS

This was a prospective observational study conducted in the department of anaesthesia and vascular surgery of a tertiary care teaching hospital. The data collection for the study was conducted between January and December 2017. The study was approved by the institutional human ethics committee, and written informed consent was obtained from all the participants.

The study population included all adult patients aged above 18 years, of both genders, ASA physical status III, ESRD stage II to IV, and on dialysis who underwent AV fistula surgery under supraclavicular brachial plexus block. All ESRD patients with comorbidities such as diabetes, hypertension, and ischemic heart disease (IHD) were included in the study. Patients who had a history of coagulation disorders, patients who did not have ideal vessels to perform AV fistula surgeries, and patients with a history of failed fistula were excluded from the study.

The diameters of brachial artery, radial artery, and cephalic vein were measured before the block, with the help of ultrasound Doppler. Supraclavicular approach was used for brachial plexus block. GE LOGIQ e (12 Linear probe) (GE medical systems (China) Co. Ltd, Jiangsu, P. R. China) was used for ultrasound guidance. The anaesthetic medication used for the block was Inj. lignocaine 2% with adrenaline (15 ml), combined with 15 ml of bupivacaine (0.5%). Subsequently, sensory, and motor blockade of the hand, forearm, and distal arm was monitored. Onset of anaesthesia was assessed using the pin prick method. Onset of motor block was clinically assessed by assessing the motor power. Vasodilatation was noted immediately in the arm and forearm by visual inspection. Heart rate, blood pressure, respiratory rate, and oxygen saturation were monitored with GE multiparameter monitor (GE medical systems (China) Co. Ltd, Jiangsu, P. R. China). After successful block, which was defined as absence of pain on pin prick as well as absence of voluntary movement, the vessel diameters were measured again using the ultrasound Doppler. After positioning the patient, with strict aseptic precaution, through a transverse incision at the elbow region, brachial artery and cephalic vein were identified looped and controlled. Inj. Heparin 2500 U IV Stat given. Through an arteriotomy wound, end to end anastomosis was done with 7'0 prolene. After attaining of perfect haemostasis wound was closed in layers and dressing done.

Fistula was then palpated for thrill, compressibility, pulsatile/no pulsatile. Graft was then auscultated for the presence of bruit. A continuous low-pitched bruit was considered normal, whereas a high-pitched bruit or whistling sound was considered as an indication of stenosis. The patency of the AV fistula in the immediate postoperative period was also assessed by ultrasound Doppler. A vascular surgeon inspected the graft to check for the presence of any infection, bruising, or hematoma along the incision line, as well as for the presence of dilated veins over the fistula before discharge. During the postoperative follow-up, graft was assessed for maturation and presence of any complications. Complications such as thrombosis, bleeding, infection, stenosis, aneurysm, and failure of maturation were immediately addressed. Patients were advised to perform isometric exercises to improve blood flow and thus to make the vein more prominent. All patients were followed for 3 months to assess the patency of the fistula using ultrasound Doppler.

All quantitative variables were checked for normal distribution using visual inspection of histograms and normality Q–Q plots. The Shapiro–Wilk test P values were also analysed. Descriptive analysis of normally distributed quantitative variables was done by mean and standard deviation. The categorical variables were summarised by frequency and proportion. The mean change in the vessel diameter before and after the block was assessed by independent-sample t-test. P value <0.05 was considered statistically significant.

The sample size was calculated assuming the expected proportion of 3 months patency of the fistula as 84%, according to the study by Aitken et al.,[6] with 5% absolute precision and 95% confidence level. As per the above mentioned sample size, the required number of study subjects was 207. To account for a loss to follow-up of approximately 10%, it was decided to add another 21 subjects to the study, making the total required sample size 228. The final study included 230 subjects, out of which 16 were lost to follow-up due to various reasons and the final analysis included 214 subjects. All the study subjects were recruited into the study by convenient sampling till the required sample size was reached.

RESULTS

A total of 214 patients undergoing AV fistula surgery were included in the final analysis. The demographic profile, distribution of patients, and comorbidities are described in Table 1.

Table 1

Baseline characteristics and type of fistula in study population (n=214)

All the vessels showed significant increase in diameter following the block. Blood flow in the brachial artery also showed significant enhancement following the block. The mean brachial artery diameter increased by 0.09 mm from the baseline (P- value 0.002). The mean cephalic vein diameter at the elbow increased by 0.50 mm (P value < 0.001). The mean radial artery diameter and mean cephalic vein diameter at wrist showed increases of 0.08 mm and 0.48 mm, respectively, following the block. The flow of brachial artery increased by 13.53 ml/Min (P value <0.001) [Table 2].

Table 2

Preoperative baseline vessel diameters and rate of blood flow before and after administration of the block

The key primary outcomes are summarised in Table 3. Immediate patency in the overall group and in both the brachiocephalic and radiocephalic groups was more than 90%. Primary patency levels at 3 months were also very high in both the brachiocephalic and radiochepahlic groups. Functional patency at 3 months was relatively much higher in the radiochephalic group (71.60%), but was very low in the brachiochephalic group (27.06%).

Table 3

Immediate and follow-up patency of the fistula

DISCUSSION

The current study has reported the immediate change in the vessel diameter, blood flow, and postoperative fistula patency at 3-month follow-up in a group of Indian ESRD patients undergoing fistula surgery under brachial plexus block.[7] The regional block, most commonly performed as ultrasound-guided brachial plexus block, has been reported to achieve better vasodilation,[23] improved operation conditions,[4] and better postoperative fistula functioning[5] compared to local anaesthesia.[8] Hence, regional anaesthesia, along with intraoperative ultrasound, while performing AV access surgery may result in improved site selection and increased opportunity for AV fistula creation. In the current study, effective blockade was achieved with required sensory and motor blockade in cases where the vascular parameters were assessed as per the protocol.[4]

In the current study, we have observed statistically significant increase in vessel diameter both at the elbow and at the wrist immediately following the block. The blood flow also increased significantly in the brachial artery. Hence, better operating conditions were created by the brachial plexus block.

In a similar study, comparing brachial plexus block through axillary approach using 5 ml ropivacaine 1% and 10 ml of saline (0.9% NaCl) and local anaesthesia using lidocaine 2%, the authors have reported considerable venous dilatation and 48.7% decline in pulsatility index (PI) with brachial plexus block when minimal alteration was noted in local anaesthesia group.[9]

Immediate fistula patency was more than 90% in the current study. Even the primary patency at 3 months was maintained by more than 80% of the subjects at both the elbow and wrist. Even though the functional patency was very high in the radiocephalic fistulas, but less than one-third of the brachiocephalic functional patency at 3 months. In a study that compared brachial plexus block through supraclavicular approach group [using 1:1 mixture of 0.5% L-bupivacaine and 1.5% lidocaine with epinephrine (1 in 200,000)] with local anaesthesia, 84% of the subjects in the brachial plexus block group showed graft patency at 3 months, but this proportion was only 62% in the local anaesthesia group.[6] The primary and functional patency rates reported in this study were comparable to the current study, along with the higher functional patency levels of radiocephalic fistulae were in line with current study findings. Another study comparing regional anaesthesia and general anaesthesia could not find any significant differences between both groups regarding early failure of AV fistula (14% in regional anaesthesia vs 11% in general anaesthesia, P = 0.80), and have specified regional anaesthesia have no major advantages over general anaesthesia in terms of fistula functioning. The early graft failure rates of the current study were comparatively higher than those reported by this study.[10] Primary patency levels reported by following regional block by few other studies were approximately 80% and were comparable with the current study findings.[11] Regional anaesthesia by supraclavicular or axillary approaches has been proved to have better vein diameter and postoperative graft patency compared to local anaesthesia or general anaesthesia by few other published studies on the subject.[312]

The key limitation of the current study was an absence of a comparison group which would have helped in documenting the relative superiority of the regional block compared to other alternative methods as well as to minimise and adjust for confounding. Even though the role of chance has been explicitly mentioned by P values, the role of potential bias in the estimation of outcomes cannot be completely ruled out due to an absence of blinding; the outcomes were measured as part of the hospital protocol.

There is a need to conduct large-scale, scientifically designed, randomised controlled trials to enhance the quality of available evidence on the subject. Till date, evidence-based guidelines are evolved based on systematic reviews and meta analyses on the subject, clinical decisions have to be made considering the efficacy, safety, and cost of different anaesthetic methods of choice, with due consideration to the expertise of the manpower and available facilities.

CONCLUSION

The current study findings prove that ultrasound-guided brachial plexus block results in good vasodilatation in the distal arm, and thereby create optimal operable conditions for AV fistula surgery. In about half of the subjects, the functional patency is maintained after 3 months. The functional patency is considerably better with brachiocephalic fistulas compared to radiocephalic fistulas.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.