Ultrasound Assessment of Diaphragmatic Movement Post Selective Superior Trunk Block versus Conventional Interscalene Block in Shoulder Arthroscopy

doi:10.21203/rs.3.rs-4718594/v1

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Ultrasound Assessment of Diaphragmatic Movement Post Selective Superior Trunk Block versus Conventional Interscalene Block in Shoulder Arthroscopy

https://doi.org/10.21203/rs.3.rs-4718594/v1

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Background

Post shoulder arthroscopic pain is significant. Interscalene block is the standard technique for controlling pain, but the high incidence of complications limits this technique. Our aim was to evaluate the incidence of hemidiaphragmatic paralysis after selective superior trunk block compared to conventional interscalene block as regards.

Methods

A randomized controlled trial was conducted in which 68 patients who were scheduled for shoulder arthroscopy were divided into two equal groups. The interscalene group received ultrasound (US) guided interscalene block and the superior trunk group received US guided selective superior trunk block. Performance time, block quality, hemidiaphragmatic movement, and incidence of complications were assessed and recorded.

Results

The incidence of hemidiaphragmatic movement in interscalene group was significantly greater than that in the selective superior trunk block (76.5% vs 38.2%), and it was completely affected in 44.1% of the interscalene group compared to 11.8% of the selective superior trunk block group. The performance duration (min) was significantly greater in the selective superior trunk group than in the interscalene group (6.97 ± 0.67) vs (6.48 ± 0.69) respectively.

Conclusions

Although US-guided interscalene and selective superior trunk blocks provided an equipotent postoperative analgesic effect, selective superior trunk block was associated with a significantly lower incidence of hemidiaphragmatic paralysis.

Trial registration:

This prospective double-blinded randomized control trial was performed at Menoufia University Hospital after obtaining approval from its ethics committee (IRB approval number 4/2022 ANET1-1) and was registered under www.pactr.org (PACTR 202203695753410) with registration number (PACTR 202203695753410), and the registration date was at 11/02/2022. This trial was conducted in accordance with the Reporting Trials (CONSORT) guideline Consolidated Standards.

shoulder arthroscopy

interscalene block

selective superior trunk block

Shoulder arthroscopy is associated with significant postoperative pain, which represents a great challenge for anesthesiologists to control. [1]

Interscalene brachial plexus block (ISB) is considered the standard and effective analgesic modality after shoulder arthroscopy; however, it has been shown to be associated with undesirable adverse effects as hemidiaphragmatic paralysis (HDP) especially with high volume local anesthetics due to the involvement of the phrenic nerve. This represents a major issue among patients with pre-existing pulmonary diseases. [2, 3]

Laurent et al. defined the superior trunk block (STB) which is a new modification of the interscalene block. The local anesthetic was injected selectively around the superior trunk. They reported that this technique limits the local anesthetic extension to the phrenic nerve and hence, decreases the incidence of hemidiaphragmatic paralysis. [4]

This randomized trial investigated whether selective STB would reduce hemidiaphragmatic paresis in participants undergoing arthroscopic shoulder surgery.

The primary outcome of the trial was the occurrence of diaphragmatic movement affection after ultrasound (US) guided selective STB and interscalene block (ISB) in shoulder arthroscopy. The secondary outcomes were block characteristics (performance duration, duration of motor block and onset of sensory block) time to the first call of analgesia, intraoperative hemodynamic parameters, intraoperative fentanyl consumption and complications of either block.

We hypothesized that selective STB would be associated with lower incidence of diaphragmatic movement affection and induce analgesia comparable to that of interscalene block.

This prospective double-blinded randomized control trial was performed at Menoufia University Hospital after obtaining approval from its ethics committee (IRB approval number 4/2022 ANET1-1) and was registered at www.pactr.org (PACTR 202203695753410). This trial was conducted in accordance with the Reporting Trials (CONSORT) guideline Consolidated Standards.

The trial included sixty-eight patients of both sexes, aged 18- to 80-year-old, who were scheduled for arthroscopic shoulder surgery and had an I or II physical status according to the American Society of Anesthesiologists (ASA). Patients who had pre-existing neuropathy in the operated limb, ASA ≥ III, coagulation disorders, local infection at the puncture site, known allergy to local anesthetics, respiratory failure or chronic obstructive pulmonary disease, breastfeeding, pregnancy, a BMI ≥ 35 kg/m2, failure to cooperate, and patient refusal were excluded. All eligible patients provided written informed consent.

Eligible patients who satisfied all inclusion criteria and did not satisfy any exclusion criteria were randomized 1:1 using a computerized software program (GraphPad software QuickCalcs, Inc., California, USA) (website: http://www.graphpad.com/quickcalcs/index.cfm). The allocation was concealed from the clinical staff, trial investigators, trial statisticians, and participants. The patients were randomly assigned to receive either US-guided ISB or selective STB. An anesthesiologist who was not involved in the data collection of the trial conducted the entire drug preparation and block administration.

All patients were administered bromazepam (1.5 mg) night prior to surgery and two hours prior to the call to the operative theatre. Upon entering the operating room, standard monitoring was implemented, an 18-gauge cannula was inserted into a lactated ringer infusion, and a peripheral vein was initiated at a rate of 10 ml/kg at room temperature for the first 30 minutes, followed by 7 ml/kg/hr. Before performing the block, the baseline diaphragmatic movement assessment was done using a curvilinear probe and the sensory and motor power of the same operative shoulder were assessed. If there were abnormalities in this examination not related to the pathology of the shoulder, the patient was excluded.

To achieve a Ramsey Sedation Scale score of 2 to 3, all patients were administered intravenous midazolam 2 to 5 mg and fentanyl up to 100 mcg, which were titrated.

Interscalene block:

The same anesthesiologist administered both blocks in accordance with the antisepsis regulations. The patient was positioned in a semi-recumbent position. A linear US transducer (Sonosite, M-Turbo, Washington) was employed to conduct an ISB at a high frequency (13 − 6 MHz). The probe was positioned transversely over the interscalene groove at the level of the C6 transverse process to identify the interscalene muscles and the cervical nerve roots C5 and C6, which are referred to as the spotlight sign. The interscalene groove was reached by introducing a 22-gauge echogenic needle from the lateral to the medial side using the in-plain technique. Subsequently, 15 ml of 0.25% bupivacaine was deposited between C5 and C6.

Selective superior trunk block:

Using the same technique to identify the spotlight sign of the cervical roots and the scalenus muscles, the probe was moved distally to observe the convergence of C5 and C6, which form the superior trunk. A 22-gauge echogenic needle was advanced from the lateral to medial region using the in-plain technique until it reached the lateral border of the superior trunk. Half of the anesthetic solution was administered anteriorly, above the trunk, and the other half was administered posteriorly, below the trunk (a total volume of 15 ml of 0.25% bupivacaine) just prior to the branching of suprascapular nerve.

The performance time (the time from transducer introduction to local anesthetic injection) and the onset of motor and sensory blocks were recorded.

The sensory block was assessed using an 11-point scale (10 representing normal sensation, 0 representing no sensation to cold) 15 to 20 minutes after the nerve block. A score of 0 was considered to indicate a complete sensory block. Additionally, the motor block was assessed utilizing shoulder external rotation (suprascapular nerve) and shoulder abduction (axillary nerve) on a three-point scale. A total score of 2 indicates no block, a score of 1 indicates paresis, which is a reduction in force compared to the contralateral arm, and a score of 0 indicates paralysis, which is the inability to overcome gravity. A score of 0 indicated as a complete motor block. These patients were excluded from the study in the event of a failed or insufficient blockage.

Hemidiaphragmatic movement affection grade was assessed after 30 min of the block by a low-frequency (5 − 2 MHz) curvilinear transducer (Sonosite, M-Turbo, Washington) in the mid-axillary line using the M-mode to calculate diaphragmatic excursion as follows:

Complete (HDP) = was defined as a reduction in diaphragmatic excursion that exceeded 75% of the baseline or exhibited paradoxical movement.
Partial = 25 to 75% decrease from baseline.
Normal (no paralysis) = changes between 0 and 25% from baseline.

Complications (e.g., pneumothorax, hematoma formation, epidural or spinal anesthesia, hoarseness, Horner’s syndrome, respiratory distress, neurological complications, PONV, and hand grip weakness) were assessed.

Propofol (2 mg/kg), fentanyl (2 µg/kg), and atracurium (0.5 mg/kg) were administered to induce anesthesia. Following oral tracheal intubation, anesthesia was sustained using isoflurane (1–2%) on an O2/air mixture (FiO2 = 0.5) and atracurium (0.25 mg/kg). Targeting an ETCO2 of 35–40 mmHg, the lung was mechanically ventilated. To maintain a bispectral index of 40–50, an isoflurane MAC was modified. When the patient´s hemodynamic parameters exceeded the baseline by 20%, 1 µg/kg fentanyl was administered. Glycopyrrolate 0.01 mg intravenously with 0.05 mg/kg neostigmine was administered to alleviate residual neuromuscular blockade following surgery. The postoperative ward was the destination for all patients after they were extubated. Acetaminophen (1 gram) was administered every 8 hours on the first postoperative day.

Intraoperative hemodynamic parameters, time to the first call of analgesia, and intraoperative fentanyl consumption were recorded.

A Consolidated Standards of Reporting Trials (CONSORT) flow chart for patient enrollment, allocation, and analysis was presented in (Fig. 1). The trial involved seventy-five patients who provided written informed consent, and sixty-eight patients successfully completed the trial. Seven patients were excluded from the trial due to incomplete block. They were separated equally into two groups: (ISB) group and (STB) group. The demographic characteristics showed similarity among groups. (Table 1). The surgery time was less than one and half hours which reduced the chance of irrigating fluid extravasation into the chest and hence, aggravated the pain score.

There was a significant difference among the two groups regarding occurrence of hemidiaphragmatic paralysis, which was greater in the ISB group than in the STB group (76.5% vs 38.2%) (P value 0.001). Moreover, the degree of movement was completely affected in 44.1% of the ISB group compared to 11.8% of the STB group (P value 0.002) (Table 2). The performance duration (min) was significantly higher in the STB group than in the ISB group (6.97 ± 0.67) vs (6.48 ± 0.69) respectively (P value = 0.008). There was no significant difference among the study groups regarding block onset or motor block duration (P value > 0.05) (Table 3). There was no significant difference among the study groups regarding the mean blood pressure and mean heart rate (Fig. 2, 3), time to the first call of analgesia and intraoperative fentanyl consumption (P value > 0.05) (Table 4). No significant complications were observed. Two patients in the ISB group developed hand grip weakness which resolved completely 12 hours after the block.

Our investigation revealed that the administration of local anesthetics to the superior trunk selectively results in a reduced incidence of diaphragmatic paralysis when contrasted with conventional interscalene blocks. However, both blocks provide equivalent analgesic efficacy without obvious side effects.

The traditional interscalene approach of brachial plexus block represents a good choice for postoperative pain control in shoulder arthroscopy. However, its association with a high incidence of diaphragmatic paralysis makes it of limited value. Morbidity is more pronounced in patients with pre-existing respiratory disease. [5]

The mechanism of phrenic nerve palsy after ISB remains unclear. Numerous theories account for the direct dissemination of local anesthetics to the roots of the phrenic nerve, in addition to the direct spread. Nerve compression by local anesthetic volume, paracervical hematoma, local ischemic changes, and/or direct nerve injury might be possible causes. [6–9]

Great efforts have been made to decrease the incidence of HDP, such as low-volume ISBs but still the occurrence of hemidiaphragmatic affection is still high, ranging from 34% − 62.5%. [10] Therefore, phrenic-sparing techniques should be available to provide adequate analgesia and reduce the incidence of hemidiaphragmatic paralysis. [11]

Burckett-St. Laurent et al. (2014) introduced selective STB as an alternative to ISB in shoulder surgery. They targeted the superior trunk inferolaterally. Injection was performed more distally after the union of the C6 and C5 nerve roots and before the suprascapular nerve branches off. Therefore, avoiding phrenic nerve block which consequently reduces the risk of respiratory depression particularly in patients with underlying respiratory diseases can improve the safety profile of these patients. [4, 12]

In this trial, we reported that STB was associated with lower incidence of HDP than interscalene nerve block. This can be explained by the occurrence of diaphragmatic paralysis which is indirectly proportional to the distance from the nerve roots. Additionally, the analgesic efficacy of both blocks was comparable represented by the intraoperative analgesic consumption and the first analgesia call. However, the performance time of the STB was slightly longer but statistically comparable to that of the interscalene block, and there was no difference between the two blocks regarding the duration of the motor block or the onset of sensory block. Patients in both blocks were hemodynamically stable, and no other complications were detected in either group.

Kim et al, carried out their trial with 126 patients, and compared STB with ISB as a sole anesthetic agent with sedo-analgesia. They used 15 ml of 0.5% bupivacaine. The superior trunk group exhibited a significantly lower incidence of HDP than did the interscalene group (4.8% vs 71.4%), as evidenced by a non-inferior worst pain score during the recovery period. This finding is consistent with our own findings. [10]

In our study, the incidence of HDP in the STB and ISB was 38.2% and 76.5%, respectively. There was a greater incidence of HDP in the STB group than in the STB group in the Kim trial (38.2% vs 4.8%). This is explained by different block techniques. In this study, we deposited local anesthetics immediately after C5 and C6 roots united together. However, Kim and his colleagues performed the block more distally in the supraclavicular fossa.

In agreement with our results, Kang et al, reported similar findings. The incidence of HDP in the STB and ISB groups was 76.3% and 97.5%, respectively, with similar pain scores and analgesic requirements in both groups. The same block technique was used in our study. [13]

We noticed that the STB was associated with less diaphragmatic movement affection. This is because the distance among C5 and the phrenic nerve root is 1.8 to 2.0 mm in adults at the cricoid cartilage level, and it increases by 3 mm for each distance of 1 cm. [4, 14]

This decreases the incidence of local anesthetic spread to the phrenic nerve with superior trunk block. [5]

The incidence of hemi-diaphragmatic paresis is reduced when the volume of local anesthetics is reduced. However, the low volume may be associated with a high incidence of block failure and poor perioperative analgesic quality among less experienced anesthetists. Therefore, we used 15 ml of 0.25% bupivacaine for both blocks, which is in accordance with the reported practices of other centers. [15–18]

The performance of the STB was longer than that of the ISB in our trial. However, the STB is clearly visible and easily defined because it is surrounded by a well-defined connective sheath without any anatomical variation, unlike the hypoechoic C5 and C6 roots which are enveloped by a thin facial layer and have anatomical variation in their course. [4, 19, 20]

The interscalene block's opioid-sparing effect was maintained in the superior trunk group due to the absence of any difference in opioid consumption or pain scores during the observation period. The STB is a more proximal block approach to the brachial plexus, which is likely the reason for this discovery. It offers extensive coverage [21]

The main strengths of this trial were the limited number of papers in this field and our primary outcome, diaphragmatic movement affection, which reflects the true impact of both blocks. However, our trial is limited by the block performance done by a single experienced anesthesiologist in a single center which can decrease the performance bias and increase the validity of the trial but limits the generalizability of the findings. Finally, we assessed the perioperative analgesia only and not the surgical anesthesia which is more important in patients with pre-existing pulmonary diseases.

In conclusion, we found that compared with conventional ISB, selective STB was associated with a lower incidence of HDP and provided equipotent effective postoperative analgesia. Further studies are required to assess STB performance difficulty and determine the appropriate local anesthetic dose that decreases the diaphragmatic paralysis and provides better analgesia.

ASA

American Society of Anesthesiologists

BMI

Body Mass Index

hour

HDP

Hemidiaphragmatic paralysis

ISB

Interscalene block

min

minute

PONV

Postoperative nausea and vomiting

STB

Superior trunk block

Ultrasound

Ethics approval and consent to participate

This prospective double-blinded randomized control trial was performed at Menoufia University Hospital after approval from the medical ethics committee (IRB approval number 4/2022 ANET1-1) of Menoufia University hospitals and registered under www.pactr.org with registration number (PACTR 202203695753410), and the registration date was at 11/02/2022. Written informed consent was obtained from all participants after explanation the concept from our side and agreement from their side. This trial was prepared in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guideline. The study was carried out in accordance with the Declaration of Helsinki 2013– Ethical Principles for Medical Research Involving Human Subjects.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Author contributions

Wesameldin A. Sultan designed the study and performed the practical part of the study. Ahmed Soliman and Wafiya Ramadan collected and analysed the data. Noha Afify completed the primary writing. Ahmed A Metwally revised the manuscript for proofreading. All the authors have read and approved the final manuscript.

Funding

This work was not supported by any funds.

Availability of data and materials

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

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Table (1): Socio-demographic and surgical data of the studied groups:

Studied variables

ISB group

(N=34)

STB group

(N=34)

Test of sig

P value

Age / years

Mean ± SD

Median (IQR)

41.1±14.2

43.0(27.7 – 56.2)

41.2±13.9

39.5 (28.0 – 57.2)

0.147

0.883

Sex N (%)

Male

Female

21 (61.8)

13 (38.2)

22 (64.7)

12 (35.3)

χ²

0.063

0.801

BMI

Mean ± SD

Median (IQR)

25.8±0.95

25.9 (25.0 – 26.6)

25.7±0.96

25.7 (24.8 – 26.4)

t-test

0.621

0.537

ASA N (%)

16 (47.1)

18 (52.9)

17 (50.0)

χ²

0.059

0.808

Duration of surgery

Mean ± SD

Median (IQR)

72.9±10.1

75.0 (65.0 – 80.0)

73.9±11.3

72.5 (65.0 – 85.0)

0.298

0.766

ISB: inter scalene group STB: selective superior trunk group U: Mann-Whitney test χ^2:chi square test IQR: Interquartile range

Table (2): Diaphragmatic movement affection among the studied groups:

Studied variables

ISB group

(N=34)

STB group

(N=34)

χ²

P value

No.

Diaphragmatic paralysis

Present

Absent

76.5

23.5

38.2

61.8

10.1

0.001*

Diaphragmatic movement affection

Absent (0-25%)

Partial (>25%-75%)

Complete (>75%)

23.5

32.4

44.1

61.8

26.4

11.8

12.3

0.002*

SB: interscalene group, STB: selective superior trunk group, χ²: chi square test, * significant

Table (3): Block characteristics among the studied groups:

Studied variables

ISB group

(N=34)

STB group

(N=34)

Test of sig.

P value

Performance duration (min)

Mean ± SD

Median (IQR)

6.48±0.69

6.50 (6.00 – 7.00)

6.97±0.67

7.00 (6.50 – 7.50)

2.46

0.008*

Onset (min)

Mean ±SD

Median (IQR)

24.7±3.54

25.0 (21.5 – 27.0)

23.7±3.31

23.0 (20.0 – 27.0)

1.16

0.244

Motor block duration (hr)

Mean ± SD

Median (IQR)

12.5±1.92

12.5 (11.0 – 14.0)

11.9±1.62

12.0 (10.0 – 13.2)

1.48

0.138

ISB: interscalene group, STB: selective superior trunk group, U: Mann-Whitney test, IQR: Inter quartile range, * significant

Table (4): Total intra-operative amount of fentanyl among the studied groups:

Studied variables

ISB group

(N=34)

STB group

(N=34)

Test of sig.

P value

First call of analgesia (hr)

Mean ±SD

Median(IQR)

9.47±2.13

9.50(8.00 – 11.2)

8.97±1.29

9.00(8.00 - 10.0)

0.661

0.509

Dose (μg/kg)

Mean ±SD

Median(IQR)

0.41±0.74

0.00(0.00 – 1.00)

0.58±0.82

0.00(0.00 – 1.00)

0.995

0.320

Rescue analgesics (N& %)

Yes

9(26.5)

25(73.5)

13(38.2)

21(61.8)

χ²

1.07

0.300

ISB: interscalene group, STB: selective superior trunk group, χ²: chi square test U: Mann-Whitney test, IQR: Inter quartile range, * significant

No competing interests reported.

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Ultrasound Assessment of Diaphragmatic Movement Post Selective Superior Trunk Block versus Conventional Interscalene Block in Shoulder Arthroscopy

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