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ORIGINAL ARTICLE
Year : 2023 | Volume
: 22
| Issue : 3 | Page : 259-264
Block performance indices of perivascular and perineural techniques of ultrasound-guided axillary block in upper limb surgeries: A comparative study
Oluwaseun Kehinde Adebayo, Olayinka R Eyelade
Department of Anaesthesia, University College Hospital, Ibadan, Nigeria
Correspondence Address:
Oluwaseun Kehinde Adebayo
Department of Anaesthesia, University College Hospital, Ibadan
Nigeria
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/aam.aam_224_21
Abstract
Background: Nerve block anesthesia is a common regional anesthesia used for upper limb surgeries because of its ability to target the operative site and provision of impressive postanesthetic pain relief. This randomized, single-blinded study compared the quality of block of the perineural (PN) and perivascular (PV) techniques of axillary brachial plexus block under ultrasound guidance. Methods: Sixty-six participants were recruited into either PV or PN groups. The local anesthetic (LA) comprised 14 ml of 0.5% bupivacaine, 14 ml of 1% lidocaine, and 2 ml of dexmedetomidine (50 μg/ml). Under ultrasound guidance, 6 ml of LA was deposited around the musculocutaneous nerve for both groups. For the PV group, 24 ml was deposited dorsal to the axillary artery while 8 ml each was deposited around median, radial, and ulnar nerves for the PN group. Results: The mean total procedure time in PN group was significantly longer than in the PV group (7.82 ± 0.95 min vs. 4.79 ± 1.11 min; P = 0.001). Participants in the PN group required more needle passes (66.7% required 4 passes while 81.8% required only 2 passes in the PV group). The success rate was 100% in PN group and 93.9% in PV group (P = 0.49). Conclusion: The PV and PN techniques were comparable in terms of their success rates and total anesthesia-related times. The PN technique had higher success rate and faster block onset, but the PV provided a quicker performance time and fewer needle passes. Hence, PV technique may be preferable to PN for high-volume surgical units.
Abstract in French Résumé
Contexte: L'anesthésie par bloc nerveux est une anesthésie régionale courante utilisée pour les chirurgies des membres supérieurs en raison de sa capacité à cibler le site opératoire et à fournir un soulagement impressionnant de la douleur postanesthésique. Cette étude randomisée à un seul insu a comparé la qualité des techniques de blocage périneural (NP) et périvasculaire (PV) du plexus brachial axillaire sous guidage échographique. Méthodes: Soixante-six participants ont été recrutés dans les groupes PV ou PN. L'anesthésie locale (AL) comprenait 14 ml de bupivacaïne à 0,5 %, 14 ml de lidocaïne à 1 % et 2 ml de dexmedetomidine (50 μg/ml). Sous la direction des ultrasons, 6 ml de LA ont été déposés autour du nerf musculo-cutané pour les deux groupes. Pour le groupe PV, 24 ml ont été déposés en position dorsale par rapport à l'artère axillaire, tandis que 8 ml ont été déposés autour des nerfs médian, radial et ulnaire pour le groupe PN. Résultats: La durée totale moyenne de la procédure dans le groupe PN était significativement plus longue que dans le groupe PV (7,82 ± 0,95 min contre 4,79 ± 1,11 min ; P = 0,001). Les participants du groupe PN ont exigé plus de passes d'aiguille (66,7 % ont exigé 4 passes, tandis que 81,8 % n'ont exigé que 2 passes dans le groupe PV). Le taux de réussite était de 100 % dans le groupe PN et de 93,9 % dans le groupe PV (P = 0,49). Conclusion: Les techniques PV et PN étaient comparables en termes de taux de réussite et de temps total liés à l'anesthésie. La technique PN a eu un taux de succès plus élevé et un début de bloc plus rapide, mais la PV a fourni un temps de performance plus rapide et moins de passes d'aiguille. Par conséquent, la technique PV peut être préférable à la PN pour les unités chirurgicales à volume élevé.
Mots-clés: Bloc nerveux, périneural, périvasculaire
Keywords: Nerve block, perineural, perivascular
Introduction 
The choice of anesthesia for upper limb surgeries continues to shift toward regional anesthesia because of superior perioperative pain control profile.[1],[2],[3],[4]
The axillary brachial plexus block (AXB) has been acclaimed to be the safest of all.[5],[6] There are two techniques for AXB – perineural (PN) or perivascular (PV).[7],[8] The addition of adjuncts such as clonidine,[9] buprenorphine,[10] and dexmedetomidine[11] has been noted to enhance the quality of nerve block.
The choice of technique for AXB remains controversial, hence this study.
Methods This prospective randomized single-blinded study with 66 participants included patients aged 18–65 years with elbow, forearm and hand injuries and subsequently had upper extremity surgeries.
The exclusion criteria were as follows: Lack of consent or inability to provide informed consent for the study, preexisting comorbid conditions such as coagulopathy, neuropathy, poorly controlled diabetes mellitus, renal or hepatic failure, allergy to local anesthetic (LA) agents/study drugs, pregnancy, past history of surgery in the axilla, infection in the axilla, failed block and conversion to general anesthesia, and weight <60 kg or >90 kg.
Each of the 66 participants was recruited and randomly assigned into either of the two groups, each for the two techniques of AXB-PV (or the PV group) and PN technique (or the PN group). Prior the commencement of surgery, a detailed preanesthetic assessment, relevant biochemical, hematological, and radiological investigations were done for each participant. All the patients received 4 mg dexamethasone as antiemetic and a total of 30 ml LA mixture comprising 14 ml of 1% lidocaine, 14 ml of 0.5% bupivacaine and 2 ml of dexmedetomidine (50 μg/ml).
All patients were placed in the supine position and the appropriate arm rotated externally and the shoulder placed in a position of 90° abduction and 90° flexion. The axillary artery and adjacent nerves were identified by placing a 5–10 MHz ultrasound probe across the axillary crease to visualize the axillary vessels and nerves. Oxygen was supplied through facemask and the patient sedated with titrated doses of intravenous midazolam (starting with 2 mg given over 10–15 s) to achieve a Ramsay sedation score of 2–3.
The musculocutaneous nerve was first identified, and 6 ml of the drug regimen (0.5% Bupivacaine, 1% lidocaine, and dexmedetomidine) was injected [Figure 1]. With the ultrasound probe still in place, in the PV group, the tip of the needle is pushed until it was positioned dorsal to the axillary artery at a 6 o'clock position. At this position, 24 ml of the mixture was deposited [Figure 2]. In the PN group, on the other hand, each of the remaining three nerves – median, radial, and ulnar nerves – was identified and anesthetized separately with 8 ml of the anesthetic mixture each [Figure 3].
Figure 2: Ultrasound identification of LA deposition point in the PV group. LA = Local anesthetic, PV = Perivascular
Figure 3: Ultrasound identification of Median, Radial and Ulnar nerves blocked separately to provide perineural block in the PN group. PN = PerineuralThe degrees of sensory and motor blocks were evaluated on the basis of the dermatome and movement produced, respectively, by the stimulation of each nerve. Motor block was graded using the modified 3-point Bromage Scale for the upper limbs, and the point of surgical anesthesia was defined as the achievement of sensory block grade of 2 with pin-prick test and a Bromage score of 2 for motor block in all four nerves. If within the first 15 min of the procedure, a sensory block grade of 2 was not achieved on the dermatomes corresponding to the median, ulnar, radial, and musculocutaneous nerves, an assessment of block failure was made, and general anesthesia immediately commenced. In addition, if the patients felt pain at any time during the surgery with a Visual Analog Scale score greater 2, the surgical procedure was paused and general anesthesia initiated. A block was successful when a surgical procedure was carried out without any need for general anesthesia.
Ethical approval for the proposal of this study was obtained from the UI/UCH Ethics committee and was in accordance with the Declaration of Helsinki. All participants gave written informed consent. The study was undertaken within a period of 4 months. All statistical analyses were carried out with SPSS version 20.0 (SPSS Inc., Chicago, IL, USA, and P < 0.05 was considered statistically significant.
Results The age and weight of the participants in the PN and PV groups were statistically comparable (42.33 ± 10.11 years and 38.33 ± 9.94 years; 73.33 ± 7.80 kg and 72.48 ± 6.96 kg respectively). The American Society of Anesthesiologists (ASA) physical status of the participants in both groups was also similar, the majority being ASA I. The pattern of upper limb surgeries done during the investigation is illustrated in [Table 1].
There were significant differences in the performance times and number of needle passes required to complete the procedure in each of the two groups [Figure 4]. As presented in [Table 2], the mean imaging time in the PV group was significantly shorter (1.79 ± 0.70 min) than that in the PN group (2.70 ± 0.81 min; P = 0.001). Similarly, the mean needling time in the PV group was significantly lower (3.00 ± 0.79 min compared to 5.12 ± 0.65 min). The mean total procedure time in the PN group was significantly longer than that in the PV group (7.82 ± 0.95 min vs. 4.79 ± 1.11 min; P = 0.001).
Figure 4: Number of needle passes required to achieve axillary block in the PV and PN group. PV = Perivascular, PN = Perineural
Table 2: Block characteristics of the perivascular versus perineural techniquesThe axillary block was considered to have failed among two patients in the PV group because of inadequate block as evidenced by incisional pain and/or spared dermatomes necessitating intervention. There was, however, no significant difference in the success rates between the two groups [Table 3]. As regards the quality of the axillary block in both groups, the mean duration of sensory block in the PV group (7.88 ± 2.03 min) was longer than the PN group (7.33 ± 1.43 min), however, not statistically significant. The performance of the axillary block in the participants was found to be associated with changes in the vital signs as illustrated in [Figure 5], [Figure 6], [Figure 7].
Table 3: Block performance indices in the perivascular and perivascular group
Figure 5: Pulse rate (mean) changes following axillary block in the PV and PN groups. PV = Perivascular, PN = Perineural
Figure 6: Systolic blood pressure (mean) changes following axillary block in the PV and PN groups. PV = Perivascular, PN = Perineural
Figure 7: Diastolic blood pressure changes (mean) following axillary block in the PV and PN groups. PV = Perivascular, PN = Perineural Discussion This index study found the anesthetic effects to be similar between the PN and PV techniques of AXB using ultrasound guidance in patients undergoing elbow, forearm and hand surgery. The use of ultrasound guidance had been noted to improve success rate of AXB regardless of the technique especially when compared with other approaches such as nerve stimulation.[12],[13],[14]
A successful block, although defined differently by various authors, is usually centered around complete sensory loss in the median, radial and ulnar nerve distribution devoid of the need for local and general anesthesia supplementation.[13] The block success rate for this study, defined as procedure that was completed without the need for general anesthesia in the two groups revealed a 100% success rate with the use of PN technique, while PV technique had a 93.9% success rate. This difference in success rate was, however, not statistically significant (P = 0.492). A comparable result was observed in studies[15],[16] which found that the success rate of the PN group was higher than that in the PV group.
Also, Perris and Watt[17] in presenting their experience of over 1000 AXBs done using PN technique reported an overall success rate of 97.9%. However, studies by Bernucci et al.[8] and Ambi et al.[18] showed a higher success with PV technique versus PN technique. Bernucci et al.[8] also using 32 ml of 1.5% lidocaine and 5 μg/ml of epinephrine reported a success rate of 92% using PN technique and a 96% using PV technique, respectively, while Ambi et al.[18] used 36 ml of 0.5% levobupivacaine and recorded a 93.3% success rate using PN technique and 96.7% rate using PV technique, respectively. The likely causes of differences in the success rates of the two techniques still remain unclear but could be due to the difference in the volume of LA used, anatomy of the nerves in relation to axillary artery, and the time set for success rate determination for the various studies cited.[8],[16],[18] These differences were, however, not statistically significant.
The imaging time observed during AXB using the PV technique was found to be significantly lower when compared to the PN technique. This finding is corroborated by Kasat et al.[16] A similar consistency was noticed with the mean needling time when comparing the PV technique with the PN technique. This result corresponded with studies by Balamurugan et al.[19] and Bernucci et al.[8]
In this study, the total anesthesia performance time, which is the summation of the imaging and needling times, was significantly shorter in the PV group when compared with the PN group. This was similar to results from studies by Vastrad et al.[20] and Kasat et al.[16] These differences in the imaging time, needling time, and subsequently total performance time were attributed to the difference in time needed for individual visualization and injection of LA around each of the axillary artery and the nerves in the PN group as relative to that required for just the musculocutaneous nerve and axillary artery in the PV group.
Furthermore, the result from the number of needle passes showed that the PV group had significantly lower number of passes required to achieve the required axillary block [Figure 4]. This observation of fewer number of needle passes with the use of PV technique was also reported in study by Cho et al.,[21] Balamurugan et al.,[19] Bernucci et al.,[8] and Vastrad et al.[20] The fewer needle passes may be due to the fact that identifying the axillary artery which is a much bigger and pulsatile structure was easier than having to locate each of the median, musculocutaneous, radial, and ulnar nerves individually in addition to the axillary artery.
A faster onset time of sensory block was observed in the PN group, which corresponded with what Balamurugan et al.,[19] Bernucci et al.,[8] and Vastrad et al.[20] reported. The block onset time only showed a similar clinical difference in both groups just as an earlier study by Cho et al.[21] who reported no significant difference in the onset time using these two techniques. Studies by Brummett et al.,[22] Esmaoglu et al.,[23] and Swami et al.[24] had demonstrated that the addition of dexmedetomidine shortened sensory and motor block onset times and also improved the duration of bupivacaine anesthesia when added. However, in this study, the addition of dexmedetomidine had no influence on the block onset time between the two groups thus suggesting that the techniques and not the composition of LA mixture were more important in terms of block onset times.
Another characteristic that measured the quality of the block was the time to regression of motor block. The mean time to regression of motor block in the PV group was slightly lower than in the PN group. This result was congruous with the findings of Ambi et al.[18] which reported a lower mean time in the PV group. The addition of dexmedetomidine to the LA was also expected to affect this similarity between the PV and the PN techniques seen in previous studies, however, the results from this study did not show any significant difference between the two groups. The shorter onset time of motor block compared to previous studies may be due to the fact that the LA mixture in this study contained three drugs (bupivacaine, lidocaine, and dexmedetomidine) compared to the earlier studies where Ambi et al.[18] used levobupivacaine alone while Brummet et al.[22] and Esmaoglu et al.[23] used dexmedetomidine with bupivacaine and dexmedetomidine with levobupivacaine, respectively.
The anesthetic outcome from this study revealed a higher mean sensory block duration of 7.88 ± 2.03 min in the PV group versus 7.33 ± 1.43 min in the PN group. This result was similar to the one obtained by Ambi et al.[18] which also observed a higher mean sensory block duration in the PV group than the PN group. The time to achieve a Bromage score of 2 was shorter in the PV group than in the PN group. This was contrary to the findings of Ambi et al.[18] who had hypothesized and also found that the PN group would achieve faster sensory/motor block than the PV group because of the direct deposition of LA around individual nerves.
The time to first request for analgesic was found to be a little longer in the PV group when compared to the PN group. Although it was thought that the PN group would be more effective and should provide a longer duration of anesthesia due to the fact the drug would have close contact with the nerves, the reverse was the case. The difference seen between the two groups was not statistically significant, and this might be explained based on the fact that the total volume of LA was deposited at a spot in the PV group and allowed to spread over time, unlike when the same volume was divided and deposited around the individual nerves in the PN group.
Conclusion The results from this study showed that using the PV and PN techniques are comparable in terms of their success rates and total anesthesia-related times. Despite the fact that the PN technique had a higher success rate and faster block-onset time as compared to the PV technique, the PV technique provided quicker procedural performance time, lesser needle passes, shorter imaging time, and more prolonged time to first request for analgesic.
Acknowledgment
The Head and all Resident doctors in the Department of Anesthesia, University College Hospital, Ibadan for their support during the conduct of this study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References 
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