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Interscalene versus supraclavicular approaches to brachial plexus block and effect of local anesthetic volumes on the incidence of phrenic nerve dysfunction during shoulder surgery
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Interscalene versus supraclavicular approaches to brachial plexus block and effect of local anesthetic volume on the incidence of phrenic nerve dysfunction during shoulder surgery


Hesham M. Ezz, Anna F. Dikstein, Mary T. West, Thomas M. Halaszynski, Kirk H. Shelley, Aymen A. Alian

Department of Anesthesia, Yale University School of Medicine, New Haven, CT  06520

INTRODUCTION:

Interscalene (ISB) and Supraclavicular (SCB) approaches to brachial plexus block were proven reliable means to provide perioperative anesthesia and analgesia for shoulder surgery [1,2].

Despite being relatively safe, a few complications must be taken into consideration including: phrenic nerve involvement leading to hemidiaphragmatic dysfunction.

Hemidiaphragmatic dysfunction can be well tolerated in healthy patients [3], but in patients with limited respiratory reserve may result in dyspnea, anxiety and decreased oxygen saturation perioperatively [4].

The study examined the effect of local anesthetic (LA) volume on the incidence of phrenic nerve involvement during different approaches to the brachial plexus (ISB and SCB).

 

METHODOLOGY:

With IRB approval, observational prospective study of 110 patients who had shoulder surgery, 63 received SCB and 47 received ISB.

An incentive spirometry (IS) device (Figure 1) was used to evaluate the influence of phrenic nerve dysfunction on inspiratory flow rate of the patient, movement of (1 ball = 600 cc/sec, 2 balls = 900 cc/sec and 3 balls = 1200 cc/sec). Two IS sets, 12 breaths each were conducted prior to (baseline) and after 20 minutes following the peripheral nerve blockade (either SCB or ISB).

After block placement, phrenic nerve dysfunction was defined as ≥ 30% reduction in the number of balls elevated (Figure 2), labored breathing and/or pain experienced at mid-axillary lower chest on the block side during deep breath. Phrenic nerve dysfunction was confirmed clinically by reduction of air entry on the block side.

Data collected : type of block, volume of Ropivacaine 0.5%, and duration of blockade.

Numerical data (LA volume and duration) was presented as mean (SD). Analysis of categorical data (incidence of phrenic nerve dysfunction with the type of the block or volume of LA) performed utilizing Chi-square test (X2). p-value < 0.01 considered as statistically significant.

 

RESULTS:

Among the 110 patients, demographic data from both groups was comparable (Table 1).

17 of 63 patients received SCB (27%) and 32 of 47 patients received ISB (68.1%) had phrenic nerve involvement (p < 0.01, X2 statistic = 18.4).

During SCB, 10 of 20 patients received > 20 cc of LA (50%) (Figure 3) and 7 of 43 patients received ≤ 20cc of LA (16.3%) experienced phrenic nerve dysfunction, absolute risk reduction (ARR) = 33.7%, (p < 0.01, X2 statistic = 7.88).

During ISB, 25 of 33 patients received > 20 cc of LA (75.8%) and 7 of 14 patients received ≤ 20 cc of LA (50%) experienced phrenic nerve dysfunction (p = 0.08, X2 statistic = 3) (Figure 4).

The LA volume for SCB and ISB was [(23.8 (9.7) and 26 (10) cc] respectively and the block duration for SCB and ISB was [(14.7 (5.7) and 13.8 (4.6) hours] respectively. There was no significant correlation between volume of LA and duration of blockade for SCB (r = 0.16, p = 0.35) and for ISB (r = -0.12, p = 0.58) as shown in (Figure 5). Adequate postoperative pain control was achieved in both groups following shoulder surgery. 

 

Among the 110 patients, demographic data from both groups was comparable (Table 1).

17 of 63 patients received SCB (27%) and 32 of 47 patients received ISB (68.1%) had phrenic nerve involvement (p < 0.01, X2 statistic = 18.4).

During SCB, 10 of 20 patients received > 20 cc of LA (50%) (Figure 3) and 7 of 43 patients received ≤ 20cc of LA (16.3%) experienced phrenic nerve dysfunction, absolute risk reduction (ARR) = 33.7%, (p < 0.01, X2 statistic = 7.88).

During ISB, 25 of 33 patients received > 20 cc of LA (75.8%) and 7 of 14 patients received ≤ 20 cc of LA (50%) experienced phrenic nerve dysfunction (p = 0.08, X2 statistic = 3) (Figure 4).

The LA volume for SCB and ISB was [(23.8 (9.7) and 26 (10) cc] respectively and the block duration for SCB and ISB was [(14.7 (5.7) and 13.8 (4.6) hours] respectively. There was no significant correlation between volume of LA and duration of blockade for SCB (r = 0.16, p = 0.35) and for ISB (r = -0.12, p = 0.58) as shown in (Figure 5). Adequate postoperative pain control was achieved in both groups following shoulder surgery. 

 

CONCLUSION:

Patients experienced a significantly increased incidence of phrenic nerve involvement during ISB versus SCB.

There was also an increase in the incidence of phrenic nerve involvement when using more than 20cc of LA during SCB.

There was no significant correlation between volume of LA used and duration of postoperative blockade.

Overall results revealed that patients scheduled for shoulder surgery received adequate postoperative pain control with SCB when using 20 cc or less of LA and resulted in significantly less incidence of phrenic nerve dysfunction (ARR = 33.7%). 

 

REFERENCES:

 

1. Klein SM  et al. Anesth Analg, 2005.

2. Tran QH  et al. Can J Anaesth, 2007.

3. Fujimura N et al. Anesth Analg, 1995.

4. Hood J and Knoblanche G. Anaesth Intensive Care, 1979. 

 

 

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