# Incidence of hemi-diaphragmatic paresis with different volumes of local anaesthetics in interscalene brachial plexus block

## TL;DR

This study found that using a lower volume of local anesthetic during a brachial plexus block reduces the risk of diaphragm paresis without affecting surgical success or pain duration.

## Contribution

The study introduces evidence that low-volume interscalene blocks reduce hemidiaphragmatic paresis while maintaining analgesic efficacy.

## Key findings

- Low-volume (10 ml) blocks had less diaphragm paresis compared to higher volumes.
- Higher drug volumes resulted in faster sensory block onset.
- Hoarseness occurred in 5 patients with the highest drug volume.

## Abstract

The incidence of diaphragmatic-palsy following interscalene brachial plexus block (IBPB) is almost 100% where the drug volume plays a significant role. We compared the incidence of hemidiaphragmatic paresis and the success rate following IBPB using three different volumes of local anaesthetics.

Ninety patients undergoing shoulder and arm surgeries under ultrasound-guided IBPB were randomly allocated into three groups: Group A (10 ml), Group B (15 ml), and Group C (20 ml). The drug administered was 0.75% ropivacaine with 50 mcg dexmedetomidine. The diaphragm excursion was measured before and 30 min after the block on the side of surgery. The incidence of diaphragmatic palsy and its severity were noted. The success rate following block, the onset of sensory blockade, duration of postoperative analgesia, and adverse effects were observed in all three groups. The statistical analysis was done using SPSS software.

The demographic data, duration of surgery, and success rate following block were statistically insignificant. The hemidiaphragmatic paresis (< 25%, 25–75%, > 75%) in Group A (29,1,0), Group B (17,13,0), and Group C (15,8,7) was statistically significant (P value < 0.001). The onset of sensory blockade was Group A (7.06 ± 0.73 min), Group B (6.23 ± 0.72 min), and Group C (4.61 ± 0.63 min) with a P value < 0.001. The duration of postoperative analgesia in Group A (440 ± 48.42 min), Group B (429 ± 44.48 min), and Group C (411 ± 51.37 min) was statistically insignificant (P value-0.072). Five patients in Group C developed hoarseness of voice postoperatively, which was managed conservatively.

Low volume ultrasound guided interscalene block (10 ml) is associated with a lower incidence of hemidiaphragmatic paresis with a similar success rate and duration of postoperative analgesia. Higher volume of the drug yields a faster onset of the sensory blockade.

The online version contains supplementary material available at 10.1186/s44158-026-00351-5.