A comparison of nerve stimulator guided paravertebral block and ilio-inguinal nerve block for analgesia after inguinal herniorrhaphy in children

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1 doi:./j x A comparison of nerve stimulator guided paravertebral block and ilio-inguinal nerve block for analgesia after inguinal herniorrhaphy in children Z. M. Naja, M. Raf, M. El Rajab, N. Daoud, F. M. Ziade, M. A. Al Tannir 6 and P. A. Lönnqvist Chairman, Department of Anaesthesia, Consultant, Department of Paediatrics, Consultant, Department of Paediatric Surgery, 6 Head of Research Unit, Makassed General Hospital, Beirut, Lebanon Assistant Professor, Department of Anaesthesia and Intensive Care, KS Astrid Lindgrens Children s Hospital, Stockholm, Sweden Assistant Professor, Faculty of Public Health, Lebanese University, Beirut, Lebanon Summary The aim of this study was to compare the efficacy of nerve stimulator guided paravertebral block with ilio-inguinal nerve block in children undergoing inguinal herniorrhaphy. Eighty children were randomly allocated to receive either paravertebral block or ilio-inguinal nerve block. Each block was evaluated in terms of intra-operative haemodynamic stability, postoperative pain scores at rest, on movement and during activity, requirement for supplemental analgesia and parental satisfaction. Haemodynamic stability was maintained significantly better during sac traction in the paravertebral block group (p <.). Pain scores and analgesic consumption were significantly lower in the paravertebral block group during the postoperative follow-up period (p <.). Parental satisfaction (9% vs 69%) and surgeon satisfaction (9% vs 6%) were significantly higher in the paravertebral block group (p <.). Paravertebral blockade improved and prolonged postoperative analgesia, and was associated with greater parental and surgeon satisfaction when compared to ilio-inguinal nerve block.... Correspondence to: Dr Z. M. Naja zouhnaja@yahoo.com Accepted: July 6 Regional analgesia for inguinal hernia repair in children has attracted increasing interest over the past few years [ 6]. Caudal block, lumbar epidural block and wound infiltration using a variety of local anaesthetic drugs and adjuncts have been used with varying success [, 9]. Ilio-inguinal nerve blockade has been widely used in this context [,, ] but when using a landmark-based technique its success rate is not high [,, ] and despite being generally safe, complications may occur [, ]. The duration of ilio-inguinal nerve block is also limited to the early postoperative period [,, ] and thus further extension of the duration of postoperative analgesia would be desirable, particularly given the increasing number of patients being treated as day cases. Paravertebral blockade has recently been shown to produce long-lasting postoperative analgesia when used in combination with general anaesthesia in paediatric herniorrhaphy, and has also been proposed as an alternative to general anaesthesia in adult inguinal hernia repair [, 6]. However, there are no comparative studies of ilio-inguinal nerve block and paravertebral block in children undergoing inguinal hernia repair. The aim of this prospective, randomised study was to compare the postoperative analgesic efficacy of ilio-inguinal nerve block and nerve stimulator guided paravertebral blockade in children undergoing herniorrhaphy. Methods With approval from the Makassed General Hospital Research and Ethics Committee and after written, informed parental consent had been obtained, 8 children aged years who were scheduled for elective outpatient herniorrhaphy were enrolled in this prospective, 6 Journal compilation Ó 6 The Association of Anaesthetists of Great Britain and Ireland

2 Z. M. Naja et al. Æ Paravertebral nerve block in children randomised, observer-blinded study conducted from March to June. Exclusion criteria comprised bilateral inguinal hernia repair, a history of allergic reactions to local anaesthetics, bleeding diatheses and spinal abnormality. Patients were randomly allocated using computergenerated random numbers to one of two treatment groups: landmark-based ilio-inguinal nerve block (INB Group, n = ) or nerve stimulator guided paravertebral block (PVB Group, n = ) using the sealed opaque envelope technique. Specially trained nurses were responsible for data collection during the postoperative period and were kept blinded at all times to group allocation. General anaesthesia was induced with sevoflurane in oxygen and was maintained during the performance of both the block and the operation with spontaneous ventilation via a facemask. No nitrous oxide or intravenous fentanyl was given as part of the anaesthetic. Inhaled sevoflurane concentrations during surgery were kept in the range..8%. It should be emphasised that the patients received fentanyl.7 lg.kg ) and clonidine. lg.kg ) contained in the local anaesthetic mixture used (see below). During the operation, any haemodynamic changes in excess of % from baseline values resulted in a step-wise increase or decrease of the sevoflurane concentration. Unilateral paravertebral blocks were performed on patients in the PVB Group at the T -L,L -L, and L -L vertebral levels with three separate injections with the child lying in the lateral position with the operative side uppermost. The needle insertion sites were.. cm lateral to the midline depending on the age and the body mass index of the child [7]. After aseptic preparation of the skin, each injection site was infiltrated with lidocaine %. ml. A nerve stimulator (Stimuplex, B Braun AG, Melsungen, Germany) was used to identify an evoked muscular contraction appropriate for the T -L levels. A -mm G insulated needle (Stimuplex A, B Braun AG) was introduced perpendicular to the skin using the following nerve stimulator settings: current = ma; frequency = Hz. Initially, contractions of the paraspinal muscles were seen as a result of direct muscle stimulation. After the paravertebral space had been entered, the stimulating needle was gently moved so as to produce the appropriate evoked muscle contraction with a threshold stimulating current of..6 ma. The movement of the needle tip within the paravertebral space is not an inand-out movement; rather, it is an angular movement and rotation around the axis of the needle to place the tip of the needle in close proximity to the corresponding nerve root. Provoked muscle responses judged to be appropriate were low abdominal, inguinal and cremaster muscle contractions for the T -L, L -L, and L -L levels, respectively. A volume of. ml.kg ) of local anaesthetic mixture was injected at each level, to give a total volume injected of. ml.kg ) of the mixture. Each ml of the local anaesthetic mixture contained: lidocaine % 6. ml, lidocaine % with adrenaline : 6 ml, bupivacaine.% 6 ml, fentanyl lg.ml ) ml and clonidine lg.ml ). ml. The paravertebral block technique and local anaesthetic mixture have been described previously by our group [, 6, 8]. Patients in the INB Group had an ilio-inguinal nerve block performed by injecting. ml.kg ) of the anaesthetic mixture described above into the oblique abdominal muscles through the lateral edge of the planned skin incision in the area just medial to the anterior superior iliac spine using a syringe and a G needle. Monitoring comprised ECG, pulse oximetry and automated, non-invasive blood pressure. Systolic blood pressure and heart rate were recorded immediately prior to skin incision (baseline), 6 s after skin incision, during sac traction and on closure of the wound. If the visual analogue pain score (VAS) was, a paracetamol mg suppository was given. If the VAS was >, oral tramadol mg.kg ) was given. On discharge, paracetamol suppositories mg were prescribed for all children as needed (maximum four suppositories in h). During hospital stay, trained nurses who were blinded to group allocation collected VAS scores from the patients. After discharge from hospital, VAS scores were assessed by parents during telephone calls made by the same nurses. Postoperative pain at rest (in bed), on movement (flexing the hip) and during activity (walking around the room) were assessed during the first two postoperative days at predetermined time intervals (, 6,,, 6 and 8 h) using an -point VAS, where represents no pain and the worse imaginable pain. Surgeon satisfaction was based on the overall postoperative clinical status of the patient. Parental satisfaction after surgery was based on their child s comfort and activity level. Parents were asked to rate their degree of satisfaction as satisfied (excellent), moderately satisfied (good) or unsatisfied. Based on clinical observations, a sample size of patients in each study group was deemed adequate to detect a % difference between the VAS scores at rest, with a power of 9% at the % significance level. Data are reported as mean (SD) or number (%). Two-way analysis of variance for repeated measurements was used to identify significant differences between the two groups when comparing pain scores and intra-operative haemodynamic data, followed by the Mann Whitney test to compare significant differences between the two groups. The Chisquared test was used to compare analgesic consumption in the two groups. Journal compilation Ó 6 The Association of Anaesthetists of Great Britain and Ireland 6

3 Z. M. Naja et al. Æ Paravertebral nerve block in children Results Full data from 79 patients were analysed; one patient in the INB Group was lost to follow-up. Patient characteristics, operation data and satisfaction results are shown in Table. Intra-operative haemodynamic stability on sac traction was significantly better in the PVB Group than in the INB Group (7 vs 8 patients did not need an increase in inspired Table Patient characteristics, operation data and satisfaction results. Values are mean (SD) or number (%). INB Group (n = ) PVB Group (n = ) p value Age; years 7. (.9) 7. (.8) Sex ratio; M : F : 9 : Weight; kg. (6.). (.) Height; cm. (.).9 (.) Duration of surgery; min.8 (6.) 7. (.8) Surgeon satisfaction Excellent 7 (69.%)* 7 (9.%) Good 8 (.%) (7.%). Dissatisfied (.%) (%) Parent satisfaction Excellent (6.%)* 7 (9.%).9 Good 9 (.%) (.%) Unsatisfied (.8%) (.%) INB, ilio-inguinal nerve block; PVB, paravertebral nerve block. *Postoperative data available from 9 patients in the INB Group. VAS scores duing activity VAS scores on movement VAS scores at rest h 6 h h 8 h h 8 h 8 h Time after surgery Percentage of SBP increase Percentage of HR increase Base line On incision Sac traction Wound closure Figure Postoperative data available from 9 patients in the INB Group. Mean systolic blood pressure (SBP) and heart rate (HR) at four time points during the study. Error bars indicate 9% CI. Ilio-inguinal block group: solid line. Paravertebral block group: dashed line. Significant difference between groups, p <.. Figure Mean visual analogue pain scores (VAS) during movement, activity and rest during the postoperative period. Error bars indicate 9% CI. Ilio-inguinal block group: solid line. Paravertebral block group: dashed line. There were statistically significant differences between the groups for all three VAS assessments at all seven postoperative assessment times, p <.. sevoflurane concentration, p <.) (Fig. ). Pain scores at rest, on movement and during activity for the two groups during the first 8 h after surgery are shown in Fig.. Twoway analysis of variance showed a significant difference in favour of the PVB Group (p <.). At each assessment time point, all three VAS pain scores (at rest, on movement and during activity) were found to be significantly lower in the PVB Group than in the INB Group (p <. to p <.) (Fig. ). The consumption of analgesic drugs was significantly higher in the INB Group than in the PVB Group during the first 6 h after surgery (p <.) (Fig. ). Only seven (8%) patients in the PVB Group needed additional analgesic drugs compared to (%) patients in the INB Group. Only one patient in the PVB Group was given tramadol compared to six patients in the INB Group. Parental satisfaction (9% vs 69%) and surgeon satisfaction (9% vs 6%) were significantly higher in the PVB Group 66 Journal compilation Ó 6 The Association of Anaesthetists of Great Britain and Ireland

4 Z. M. Naja et al. Æ Paravertebral nerve block in children Number of patients needing analgisics than in the INB Group (p <.). No complications apart from mild local tenderness at the paravertebral block injection sites in three patients were noted in the PVB Group patients. However, two children in the INB Group had transient femoral nerve blocks. Discussion Time after surgery The main finding of this study was a significant improvement in postoperative analgesia and a decreased need for postoperative analgesic drugs after herniorrhaphy in children treated with nerve stimulator guided paravertebral nerve blockade compared to those undergoing ilioinguinal nerve block. Another important finding was better intra-operative haemodynamic stability in the PVB Group. Pre-incision ilio-inguinal nerve block is widely used as a supplement to general anaesthesia in children undergoing inguinal hernia repair [ ]. However, the use of ilio-inguinal nerve block is often associated with adjustments to the inspired concentration of volatile agent during hernia sac traction due to insufficient blockade of this anatomical structure []. Studies have shown that ilioinguinal nerve blocks have a limited success rate in terms of postoperative analgesia in both adults (6%) [] and children ( 7%) [, ]. Attempts to improve the technique either by using a double injection approach or with the addition of a genitofemoral nerve block have not been successful [, ]. Before commenting on our findings, we would like to discuss some limitations of the study. Firstly, to provide a proper double-blind situation, a design involving placebo blocks would have been necessary. However, in common with many other authors, we believe that such a study design is not appropriate in children for ethical reasons and we therefore decided to use an observer-blinded study design instead, well aware that such a study design INB PVB h 6 h h 8 h h 8 h 8 h Figure Number of patients given postoperative analgesic drugs. INB: Ilio-inguinal block group. PVB: Paravertebral block group. Significant difference between groups, p <.. might introduce a degree of bias. Furthermore, parental blinding could not be fully guaranteed throughout the duration of the study as treatment allocation may have been revealed when the dressings were removed after discharge from hospital. Second, the pain assessment tool we used may be academically questionable from a purist s point of view. However, we believe that the VAS methodology described is the only realistic tool that can be used considering the age range of the study population and the fact that a large proportion of pain assessments would have to be carried out by the parents after hospital discharge. Readers should be aware of these limitations when reading and interpreting the results of our study. Although the success of our ilio-inguinal nerve blocks compare well with those reported in other studies in terms of intra-operative haemodynamic stability and postoperative analgesia [,, ], the success of our paravertebral blocks was clearly superior. The main reason for this finding is, in the authors opinion, most likely related to the innervation of the surgical field. The inguinal region receives sensory innervation from the ilioinguinal, iliohypogastric and genitofemoral nerves []. Studies show great variation in the sensory innervation of the inguinal region [] and against this anatomical background, the relatively poor performance of the landmark-based ilio-inguinal nerve block is not surprising []. As the peripheral nerves supplying the inguinal region are derived from the spinal nerve roots of T -L [7], a better and more reliable block would be expected if these structures were the primary target of the block. The paravertebral block technique we describe not only accomplishes this but also will most likely be able to block the visceral innervation of the hernia sac due because that a large proportion of the visceral afferent nerves that supply the hernia sac are included in the above-mentioned spinal nerve roots, whereas the more peripheral ilio-inguinal nerve block is unable to block these visceral nerves []. Another factor that may explain the excellent results of paravertebral blockade in this study is the use of a nerve stimulator technique that allows the anaesthetist to direct the needle into close proximity to the spinal nerves just after leaving the intervertebral foramen. The above-mentioned factors may explain the excellent results of using paravertebral blockade for inguinal hernia repair, both as described in children in the present study and as described in previous reports in both adults [, ] and children [6]. This study is too small to allow any comparison of the two techniques with regard to incidence of sideeffects and complications. However, when paravertebral blocks are performed at T -L levels, the risk of pneumothorax should be minimal. In agreement with other studies [, 6, 8, 9], no major complications Journal compilation Ó 6 The Association of Anaesthetists of Great Britain and Ireland 67

5 Z. M. Naja et al. Æ Paravertebral nerve block in children resulted from the use of paravertebral block, although local tenderness at the injection points was observed in three patients. In conclusion, the use of paravertebral blockade in combination with sevoflurane anaesthesia resulted in improved and prolonged postoperative analgesia, better intra-operative haemodynamic stability, and higher parent and surgeon satisfaction compared to ilio-inguinal nerve block for inguinal hernia repair in children. References Lim SL, Ng Sb A, Tan GM. Ilioinguinal and iliohypogastric nerve block revisited: single shot versus double shot technique for hernia repair in children. Paediatric Anaesthesia ; : 6. Tsuchiya N, Ichizawa M, Yoshikawa Y, Shinomura T. Comparison of ropivacaine with bupivacaine and lidocaine for ilioinguinal block after ambulatory inguinal hernia repair in children. Paediatric Anaesthesia ; : Ivani G, Conio A, De Negri P, Eksborg S, Lönnqvist PA. Spinal versus peripheral effects of adjunct clonidine: comparison of the analgesic effect of a ropivacaine-clonidine mixture when administered as a caudal or ilioinguinaliliohypogastric nerve blockade for inguinal surgery in children. Paediatric Anaesthesia ; : 68. Sasaoka N, Kawaguchi M, Yoshitani K, Kato H, Suzuki A, Furuya H. Evaluation of genitofemoral nerve block, in addition to ilioinguinal and iliohypogastric nerve block, during inguinal hernia repair in children. British Journal of Anaesthesia ; 9: 6. Machotta A, Risse A, Bercker S, Streich R, Pappert D. Comparison between instillation of bupivacaine versus caudal analgesia for postoperative analgesia following inguinal herniotomy in children. Paediatric Anaesthesia ; : Splinter WM, Bass J, Komocar L. Regional anaesthesia for hernia repair in children: local vs caudal anaesthesia. Canadian Journal of Anesthesia 99; : Schindler M, Swann M, Crawford M. A comparison of postoperative analgesia provided by wound infiltration or caudal analgesia. Anaesthesia and Intensive Care 99; 9: Breschan C, Jost R, Krumpholz R, et al. A prospective study comparing the analgesic efficacy of levobupivacaine, ropivacaine and bupivacaine in paediatric patients undergoing caudal blockade. Paediatric Anaesthesia ; : 6. 9 Dalens B, Hasnaoui A. Caudal anaesthesia in paediatric surgery: success rate and adverse effects in 7 consecutive patients. Anaesthesia and Analgesia 989; 68: 8 9. Dalens B, Ecoffey C, Joly A, et al. Pharmacokinetics and analgesic effect of ropivacaine following ilioinguinal iliohypogastric nerve block in children. Paediatric Anaesthesia ; :. Wassef MR, Randazzo T, Ward W. The paravertebral nerve root block inguinal herniorrhaphy; a comparison with the field block approach. Regional Anesthesia and Pain Medicine 998; : 6. Rosario DJ, Jacob S, Luntley J, Skinner PP, Raftery AT. Mechanism of femoral nerve palsy complicating percutaneous ilioinguinal field block. British Journal of Anaesthesia 997; 78: 6. Naja MZ, El Hassan M, Oweidat M, Zbibo R, Ziade MF, Lönnqvist PA. Paravertebral blockade vs. general anaesthesia or spinal anaesthesia for inguinal hernia repair. Middle East Journal of Anesthesiology ; 6:. Weltz CR, Klein SM, Arbo JE, Greengrass RA. Paravertebral block anaesthesia for inguinal hernia repair. World Journal of Surgery ; 7: 9. Klein SM, Greengrass RA, Weltz C, Warner DS. Paravertebral somatic nerve block for outpatient inguinal herniorrhaphy. an expanded case report of patients. Regional Anesthesia and Pain Medicine 998; : 6. 6 Naja ZM, Raf M, El Rajab M, Ziade FM, Al Tannir MA, Lönnqvist PA. Nerve stimulator-guided paravertebral blockade combined with sevoflurane sedation versus general anaesthesia with systemic analgesia for postherniorrhaphy pain relief in children: a prospective randomized trial. Anesthesiology ; : 6. 7 Starling JR, Harms BA, Schroeder ME, Eichman PL. Diagnosis and treatment of genitofemoral and ilioinguinal entrapment neuralgia. Surgery 987; : Naja MZ, Ziade MF, Lönnqvist PA. Nerve-stimulator guided paravertebral blockade vs. general anaesthesia for breast surgery: a prospective randomized trial. European Journal of Anaesthesiology ; : Naja Z, Ziade MF, Lönnqvist PA. Bilateral paravertebral somatic nerve block for ventral hernia repair. European Journal of Anaesthesiology ; 9: Journal compilation Ó 6 The Association of Anaesthetists of Great Britain and Ireland