Regional anaesthesia is widely used for upper-limb surgery because it can provide surgical anaesthesia together with prolonged postoperative analgesia while avoiding airway manipulation and reducing exposure to systemic anaesthetic and opioid drugs. Among the different approaches to the brachial plexus, the supraclavicular approach is particularly suitable for procedures involving the arm below the shoulder because the trunks and divisions of the brachial plexus are arranged compactly at this level.[1,2]

The proximity of the brachial plexus to the subclavian artery, first rib, and pleura makes accurate needle placement essential. Traditional landmark-based approaches were associated with incomplete block, vascular puncture, nerve injury, and pneumothorax. The introduction of peripheral nerve stimulation improved nerve localisation by producing a distal motor response when the needle approached the brachial plexus. However, the method remains dependent on indirect electrical responses and does not display the needle, nerves, vessels, pleura, or distribution of the injected solution.[1,2]

The introduction of ultrasound guidance represented an important development in regional anaesthesia. Kapral et al. described an ultrasound-guided supraclavicular approach that allowed direct imaging of the brachial plexus and surrounding anatomical structures.[3] Real-time imaging permits continuous observation of needle advancement and local anaesthetic spread, potentially improving the precision of injection and allowing early correction of inappropriate needle placement.

Williams et al. reported that ultrasound guidance shortened the time required to perform a supraclavicular block and improved block quality compared with a technique based primarily on anatomical landmarks and nerve stimulation.[4] Subsequent systematic reviews and meta-analyses found that ultrasound-guided peripheral nerve blocks generally have faster onset, lower failure or supplementation rates, longer block duration, and fewer vascular punctures than blocks performed using electrical nerve stimulation alone.[5-7]

Ultrasound guidance may also improve safety by allowing visualisation of vascular structures, the first rib, and the pleura and by permitting observation of the distribution of local anaesthetic. Registry evidence has associated ultrasound guidance with a lower incidence of local anaesthetic systemic toxicity, although ultrasound cannot eliminate neurological, vascular, or pleural complications.[8,9] The benefits of ultrasound are also influenced by image quality, anatomical variation, equipment availability, operator experience, and maintenance of continuous needle-tip visualisation.[9,10]

Despite the increasing availability of ultrasound, peripheral nerve stimulation remains commonly used, particularly in institutions where ultrasound equipment, training, or expertise is limited. Direct comparisons of the two techniques therefore remain clinically relevant. The uploaded study similarly evaluated execution time, sensory and motor block characteristics, success, complications, and postoperative analgesia in patients undergoing upper-limb surgery.[11]

The present study was undertaken to compare ultrasound-guided and peripheral nerve stimulator-guided supraclavicular brachial plexus block with respect to procedural efficiency, block characteristics, perioperative stability, success rate, postoperative analgesia, and complications.

AIM AND OBJECTIVES

Aim

To compare ultrasound-guided and peripheral nerve stimulator-guided supraclavicular brachial plexus block in patients undergoing upper-limb surgery.

Objectives

1. To compare the block execution time and onset of sensory and motor blockade between ultrasound-guided and peripheral nerve stimulator-guided supraclavicular brachial plexus block.
2. To compare block success, duration of sensory and motor blockade, time to first analgesic request, perioperative stability, and complications between the two techniques.

Study design and setting This prospective randomized controlled study was conducted at Department of Anesthesia, Government Medical College, Siddipet during May 2025 to April 2026. Written informed consent was obtained from all patients before their inclusion in the study. Study population The study included 50 adult patients undergoing elective upper-limb surgery. Patients were randomly divided into two groups of 25 each: • Group I: Ultrasound-guided supraclavicular brachial plexus block. • Group II: Peripheral nerve stimulator-guided supraclavicular brachial plexus block. Inclusion criteria Patients aged 18–60 years, weighing 40–70 kg, belonging to ASA physical status I or II, having normal sensory and motor function, and undergoing elective upper-limb surgery below the shoulder were included. These eligibility criteria correspond to those reported in the uploaded study. Exclusion criteria Patients with allergy to the local anaesthetic drugs, pregnancy, significant comorbid conditions, abnormal sensory or motor function, or any contraindication to supraclavicular brachial plexus block were excluded. Preanaesthetic preparation All patients underwent a detailed preanaesthetic assessment. The procedure was explained to each patient, and informed consent was obtained. The operating theatre, resuscitation equipment, drugs, ultrasound machine, peripheral nerve stimulator, and monitoring equipment were prepared before performing the block. Standard monitoring included heart rate, non-invasive systolic and diastolic blood pressure, respiratory rate, and peripheral oxygen saturation. Baseline values were recorded before administration of the block. Group I: Ultrasound-guided technique In Group I, a linear ultrasound probe was positioned over the supraclavicular region to identify the brachial plexus and surrounding anatomical structures. The block needle was advanced under real-time ultrasound guidance. After confirming appropriate needle placement and negative aspiration, the local anaesthetic solution was administered while observing its spread around the brachial plexus. Group II: Peripheral nerve stimulator-guided technique In Group II, the block needle was connected to a peripheral nerve stimulator and advanced through the supraclavicular approach. Proximity to the brachial plexus was confirmed by observing an appropriate motor response in the upper limb. After confirmation of needle position and negative aspiration, the local anaesthetic solution was administered. The source article describes the ultrasound group as using a linear probe for real-time visualisation and the nerve stimulator group as confirming nerve proximity through motor responses. Assessment of Block Block characteristics were assessed by recording the block execution time, onset of sensory and motor blockade, time required to achieve complete sensory and motor blockade, duration of sensory and motor blockade, block success rate, time to first analgesic request, perioperative haemodynamic and respiratory parameters, and incidence of complications. Block execution time was measured from the beginning of block preparation until completion of the procedure. The onset of sensory and motor blockade was recorded from the completion of local anaesthetic administration until the first evidence of sensory loss and reduction in motor power, respectively. The time required to achieve complete block was recorded from completion of the injection until adequate sensory and motor blockade was obtained for surgery. The duration of sensory and motor blockade was measured from the onset of the respective block until complete recovery of sensory and motor function. A successful block was defined as adequate sensory and motor blockade that permitted completion of surgery without conversion to general anaesthesia. An inadequate block requiring general anaesthesia was considered a block failure. Postoperative Analgesia Postoperative pain was assessed using a visual analogue scale ranging from 0 to 10, where 0 indicated no pain and 10 indicated the worst imaginable pain. The interval from administration of the block to the first request for postoperative analgesia was recorded as the time to first analgesic request. Perioperative Monitoring Heart rate, systolic blood pressure, diastolic blood pressure, respiratory rate, and peripheral oxygen saturation were recorded preoperatively, immediately after administration of the block, at 5, 10, 15, and 30 minutes, and subsequently at 30-minute intervals up to 300 minutes. Assessment of Complications Patients were monitored throughout the perioperative period for local and systemic complications, including vessel puncture or haematoma, pneumothorax, cardiotoxicity, breathlessness or tachypnoea, Horner syndrome, and neurological sequelae. Statistical Analysis Continuous variables were expressed as mean ± standard deviation, while categorical variables were presented as frequencies, percentages, or ratios, as appropriate. Age, weight, and other continuous variables were compared using the unpaired Student’s t-test. Sex, ASA grade, block success rate, and complications were analysed using the chi-square test or Fisher’s exact test, as appropriate. A p value of less than 0.05 was considered statistically significant.

A total of 50 patients undergoing upper-limb surgery under supraclavicular brachial plexus block were included. They were divided into two groups of 25 patients each. Group I received an ultrasound-guided supraclavicular brachial plexus block, whereas Group II received a peripheral nerve stimulator-guided supraclavicular brachial plexus block.

The demographic variables, block characteristics, block success rate, perioperative haemodynamic and respiratory parameters, duration of surgery, duration of sensory and motor blockade, time to first analgesic request, and complications were compared between the two groups.

Table 1. Comparison of demographic characteristics

The mean age was 34.6 ± 9.4 years in Group I and 35.2 ± 9.7 years in Group II. The male-to-female ratio was 17:8 in Group I and 15:10 in Group II. The mean body weight was 58.1 ± 5.6 kg and 60.2 ± 6.1 kg in Groups I and II, respectively. Both groups were comparable with respect to age, sex, body weight, and ASA physical status, with no statistically significant differences between them.

Table 2. Comparison of block characteristics

The mean block execution time was significantly shorter in Group I than in Group II. The onset of sensory blockade was 2.74 ± 0.96 minutes in Group I compared with 5.98 ± 0.82 minutes in Group II. Similarly, the onset of motor blockade was significantly faster in Group I than in Group II. All three block-related parameters showed statistically significant differences between the groups.

Figure 1 – Block Execution Time

Figure 2 – Onset of Sensory and Motor Block

Figure 3 – Time to Achieve Complete Block

Table 3. Comparison of time required to achieve complete block

Only patients with successful blocks were included in this analysis.

The mean time required to achieve complete sensory and motor blockade was 12.25 ± 1.14 minutes in Group I and 16.95 ± 0.98 minutes in Group II. The complete block was therefore achieved significantly earlier with ultrasound guidance than with peripheral nerve stimulator guidance.

Figure 4 – Block Success and Failure Rates

Table 4. Comparison of block success rates

A successful block was achieved in 24 of 25 patients in Group I and 23 of 25 patients in Group II. Block failure occurred in one patient in Group I and two patients in Group II. These patients required supplementation with general anaesthesia.

Although the success rate was numerically higher in Group I, the difference between the two groups was not statistically significant.

Table 5. Perioperative changes in heart rate and blood pressure

Table 5A. Perioperative changes in heart rate

Table 5B. Perioperative changes in systolic blood pressure

Table 5C. Perioperative changes in diastolic blood pressure

Heart rate increased slightly immediately after administration of the block and subsequently returned towards baseline in both groups. Systolic and diastolic blood pressure also remained stable throughout the observation period. No statistically significant differences were identified between the two groups at any measured time point.

Table 6. Perioperative changes in respiratory rate and SpO₂

Table 6A. Perioperative changes in respiratory rate

Table 6B. Perioperative changes in peripheral oxygen saturation

The respiratory rate and peripheral oxygen saturation remained within clinically acceptable ranges throughout the perioperative period. There were no statistically significant differences between the two groups at any recorded time point.

Table 7. Comparison of duration of surgery

The mean duration of surgery was 97.4 ± 24.8 minutes in Group I and 91.2 ± 17.6 minutes in Group II. The difference was not statistically significant.

Table 8. Comparison of duration of anaesthesia and analgesia

Only patients with successful blocks were included in this analysis.

The mean duration of motor blockade was significantly longer in Group I than in Group II. The duration of sensory blockade was also significantly prolonged with ultrasound guidance. Similarly, the time to the first postoperative analgesic request was significantly longer in Group I, indicating a longer duration of postoperative analgesia.

Figure 5 – Duration of Block and Postoperative Analgesia

Table 9. Comparison of complications

No complications were observed in Group I. Vessel puncture occurred in two patients in Group II. No patient in either group developed Horner syndrome, pneumothorax, or neurological sequelae. The difference in the overall occurrence of complications was not statistically significant.

The present study compared ultrasound-guided and peripheral nerve stimulator-guided supraclavicular brachial plexus block in 50 patients undergoing upper-limb surgery. The principal findings were that ultrasound guidance was associated with shorter execution time, faster onset of sensory and motor blockade, earlier achievement of complete block, longer duration of sensory and motor block, and a longer interval before the first postoperative analgesic request. Block success was numerically higher and complications were less frequent with ultrasound guidance, although these differences were not statistically significant.

Demographic characteristics

The groups were comparable with respect to age, sex, weight, and ASA physical status. This comparability reduces the likelihood that the observed differences in block characteristics were primarily caused by baseline demographic imbalance. Similar demographic comparability has been reported in previous randomized and comparative investigations of ultrasound and peripheral nerve stimulator guidance.[12-16]

Block execution time

The mean block execution time was 4.18 ± 1.02 minutes in the ultrasound-guided group and 7.58 ± 1.10 minutes in the nerve stimulator group. The difference was highly significant.

A shorter execution time with ultrasound guidance is clinically plausible because the operator can directly identify the brachial plexus, subclavian artery, first rib, and pleura and can follow the needle tip during advancement. In contrast, peripheral nerve stimulation may require repeated needle redirection before an acceptable motor response is obtained.

Alfred et al. reported a significantly shorter procedure time with ultrasound guidance than with peripheral nerve stimulation.[12] Singh et al. also found that ultrasound-guided supraclavicular block had favourable execution and block-quality characteristics.[13] Rupera et al. and Ratnawat et al. similarly observed shorter performance times in ultrasound-guided groups.[14,16] These findings are also consistent with systematic evidence showing that ultrasound-guided peripheral nerve blocks are generally performed more rapidly than blocks guided by electrical stimulation alone.

Onset of sensory and motor block

Sensory block began significantly earlier in Group I than in Group II, with mean onset times of 2.74 ± 0.96 and 5.98 ± 0.82 minutes, respectively. Motor block also developed earlier with ultrasound guidance, at 5.96 ± 1.35 minutes compared with 11.18 ± 0.84 minutes.

Direct observation of local anaesthetic distribution may allow the solution to be deposited more uniformly around the trunks and divisions of the plexus. By comparison, an appropriate motor response during nerve stimulation confirms proximity to a stimulated neural component but does not demonstrate the distribution of the injected solution around the entire plexus.

Alfred et al. reported faster sensory and motor onset with ultrasound guidance.[12] Singh et al. found a faster onset and better-quality block with ultrasound guidance, although statistical significance varied across individual nerve territories.[13] Rupera et al., Surendran et al., and Ratnawat et al. also documented favourable onset characteristics with ultrasound-guided supraclavicular block.[14-16]

The present findings are consistent with the meta-analysis by Abrahams et al., which found that ultrasound-guided peripheral nerve blocks had faster onset and longer duration than blocks performed with electrical nerve stimulation.[5]

Time to achieve complete block

Among patients with successful blocks, the time required to achieve complete block was 12.25 ± 1.14 minutes in Group I and 16.95 ± 0.98 minutes in Group II. This difference was statistically significant.

Ratnawat et al. reported earlier achievement of complete block with ultrasound guidance, with complete block attained at approximately 13.7 minutes in the ultrasound group compared with 16.1 minutes in the peripheral nerve stimulator group.[16] Rupera et al. also documented a shorter time to complete blockade with ultrasound guidance.[14]

The more rapid development of complete block may reduce the interval between block administration and surgical readiness. However, actual operating-room efficiency is also affected by equipment preparation, patient positioning, operator experience, and availability of trained assistance.

Block success rate

The success rate was 96.0% in Group I and 92.0% in Group II. Although the ultrasound-guided group had a numerically higher success rate, the difference was not statistically significant.

The lack of statistical significance is unsurprising because the absolute difference represented only one patient and the study was not powered to detect a small difference in success rate. The absence of statistical significance should therefore not be interpreted as proof that the techniques are identical.

Singh et al. reported successful block in approximately 90% of ultrasound-guided cases compared with 73.1% of nerve stimulator-guided cases.[13] Ratnawat et al. reported success rates of 97.5% and 90%, respectively.[16] Surendran et al. also observed a higher numerical success rate with ultrasound guidance.[15]

Cochrane and other systematic reviews have found that ultrasound guidance increases the proportion of blocks adequate for surgery and decreases the need for supplementation or conversion to general anaesthesia, although the magnitude of benefit varies by block site, operator expertise, and study methodology.[5-7]

Duration of sensory and motor block

The mean duration of sensory block was significantly longer in Group I than in Group II: 227.8 ± 18.1 versus 199.4 ± 21.2 minutes. Motor block was also significantly prolonged with ultrasound guidance: 194.3 ± 18.0 versus 172.8 ± 14.5 minutes.

Longer block duration may be related to more accurate deposition and circumferential spread of the local anaesthetic solution around the neural structures. However, the duration of blockade is also strongly affected by the local anaesthetic used, its concentration and volume, the presence of adrenaline or other adjuvants, and individual patient variability.

Singh et al. reported a substantially longer duration of block with ultrasound guidance.[13] Alfred et al. similarly observed longer sensory blockade in their ultrasound group.[12] Rupera et al. and Ratnawat et al. also reported longer sensory and motor block duration with ultrasound-guided techniques.[14,16]

Time to first analgesic request

The mean time to first analgesic request was 267.9 ± 19.0 minutes in Group I and 243.8 ± 23.2 minutes in Group II. The difference was statistically significant.

This finding suggests that the greater duration of sensory blockade in the ultrasound-guided group translated into a modest prolongation of early postoperative analgesia. Raghove et al. reported longer analgesia with ultrasound-guided supraclavicular block than with a conventional landmark technique.[17] Other comparative studies have also reported longer block duration or delayed rescue analgesia with ultrasound guidance.[12-14]

Nevertheless, postoperative analgesia is influenced by the operative procedure, local anaesthetic formulation, adjuvants, baseline pain sensitivity, intraoperative analgesic administration, and rescue-analgesia threshold. These variables should therefore be standardised and reported clearly.

Haemodynamic and respiratory parameters

Heart rate, systolic and diastolic blood pressure, respiratory rate, and SpO₂ remained comparable between the two groups at all recorded time points. Both techniques therefore provided satisfactory perioperative physiological stability in the studied population.

The absence of significant changes is expected because the primary difference between the groups was the technique used for locating the brachial plexus rather than the systemic anaesthetic regimen. Similar haemodynamic stability has been reported in comparative studies of ultrasound and nerve stimulator-guided brachial plexus blockade.[12,15]

However, serial assessment at numerous time points increases the number of statistical comparisons. Analysis using a repeated-measures model would provide a more rigorous assessment of overall group-by-time differences when patient-level data are available.

Complications

No procedural complication occurred in Group I, while vessel puncture occurred in two patients in Group II. There were no cases of Horner syndrome, pneumothorax, or neurological sequelae in either group.

The difference in vessel puncture was not statistically significant, largely because the total number of events was small. Nevertheless, the direction of the finding is consistent with the ability of ultrasound to identify vascular structures and guide the needle under direct vision.

Singh et al. reported fewer accidental vascular punctures in the ultrasound group than in the nerve stimulator group.[13] Ratnawat et al. and Surendran et al. also reported lower frequencies of vascular puncture with ultrasound guidance.[15,16] Large registry data found higher odds of vascular puncture and multiple skin punctures with nerve stimulation alone than with ultrasound alone.[23] Meta-analyses have similarly shown a lower pooled incidence of vascular puncture with ultrasound guidance.[5-7,21]

The absence of pneumothorax in this study should not be interpreted as elimination of risk. Pneumothorax has been reported even after ultrasound-guided supraclavicular block, particularly when continuous visualisation of the needle tip is lost.[24] Ultrasound is therefore a guidance tool and not a substitute for anatomical knowledge, appropriate training, incremental injection, repeated aspiration, and continuous clinical monitoring. (

Strengths of the study

The study compared several clinically relevant outcomes, including:

• Procedural time.
• Sensory and motor onset.
• Time to complete block.
• Block success.
• Duration of anaesthesia.
• Postoperative analgesia.
• Serial haemodynamic and respiratory measurements.
• Procedure-related complications.

The use of the same clinical population and equal group sizes supported direct comparison between the techniques.

Limitations

The study had several limitations.

First, the sample size was relatively small and was inadequate to establish differences in uncommon complications such as pneumothorax, persistent neurological injury, or local anaesthetic systemic toxicity.

Second, the operator performing the block could not be blinded to the technique. This could have influenced execution time and technical performance.

Third, operator experience can have a major effect on the relative performance of ultrasound and peripheral nerve stimulation. The findings may therefore not be generalisable to clinicians at different stages of training.

Fourth, multiple comparisons were made for serial physiological variables. A repeated-measures or mixed-effects analysis would be preferable when patient-level observations are available.

Fifth, postoperative pain and analgesia may have been influenced by variations in the type and duration of surgery.

Sixth, patient satisfaction, number of needle passes, block-related discomfort, local anaesthetic volume, and cost-effectiveness were not evaluated.

Ultrasound-guided supraclavicular brachial plexus block was associated with shorter block execution time, faster onset of sensory and motor blockade, and earlier achievement of complete block than peripheral nerve stimulator-guided block. Ultrasound guidance was also associated with longer sensory and motor block duration and a longer interval before the first postoperative analgesic request. Both techniques maintained stable perioperative haemodynamic and respiratory parameters. The ultrasound-guided group had a numerically higher block success rate and fewer vessel punctures, but these differences were not statistically significant. Larger adequately powered studies are required to compare uncommon complications and determine the cost-effectiveness of routine ultrasound use. Conflict of Interest: None Funding Support: Nil

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