British Journal of Anaesthesia, 2004, Vol. 92, No. 2 273-274
© 2004 The Board of Management and Trustees of the British Journal of Anaesthesia
Short Communications |
Leg weakness is a complication of ilio-inguinal nerve block in children
1 Anaesthetic Department, 2 Day Procedure Unit and 3 Department of Paediatrics, Norfolk and Norwich University Hospital, Norwich NR4 7UZ, UK
*Corresponding author. E-mail: anna@lipp.org.uk
Accepted for publication: July 25, 2003
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Abstract |
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Background. Ilio-inguinal nerve block is commonly used in children to provide analgesia after surgery in the groin. Several case reports and clinical studies have described leg weakness after this technique and suggest that it may caused by inadvertent femoral nerve block. No prospective studies describing the incidence of this complication have been published.
Methods. We carried out a prospective, observational study to find out how many children had leg weakness after ilio-inguinal nerve block. We studied 200 children having day-case surgery in the groin under a general anaesthetic with an ilio-inguinal nerve block. All children performed a simple leg-raising test with each leg before induction of general anaesthesia with a standardized ilio-inguinal nerve block on the side of surgery. When the child was awake and comfortable after surgery, they repeated the leg-raising test.
Results. Sixteen of 182 children (8.8%) had leg weakness after surgery on the side of the nerve block only, as detected by a leg-raising test.
Conclusions. Leg weakness consistent with a femoral nerve block occurs after ilio-inguinal nerve block in approximately one in nine children.
Br J Anaesth 2004; 92: 273–4
Keywords: anaesthetic techniques, ilio-inguinal nerve block; anaesthesia, day-case
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Introduction |
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Ilio-inguinal nerve block provides analgesia for several hours after surgery in the groin and is commonly used for children undergoing day-case procedures. However, there have been case reports of leg weakness occurring after these nerve blocks which have resulted in serious injury to patients1 and delayed discharge home.2 Cadaver studies have shown that this leg weakness could be caused by inadvertent femoral nerve block.3
A well recognized textbook of regional anaesthesia4 specifically describes ilio-inguinal nerve block as being free of the complications of lower limb motor block, and it has been stated that the risk of a femoral nerve block after an ilio-inguinal nerve block is so negligible that patients need not be warned about this risk.5
We performed a prospective, observational study with two aims: to find out how common leg weakness is after ilio-inguinal nerve block and to investigate the practical use of a leg-raising test to demonstrate leg weakness in children.
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Methods and results |
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The study was approved by the local research ethics committee and took place in the day surgery unit of a large district general hospital. The participants were 200 children aged 2–12 yr having surgery in the groin. Their parents gave consent for their inclusion in the study after reading an information sheet and asking staff any questions.
All children in the study were encouraged to perform a leg-raising test with each leg before going to the anaesthetic room. The child was asked to lift each leg in turn off the bed to touch a ball held in a net approximately 30 cm directly above them with the foot. This manoeuvre produced extension of the knee against gravity.
After induction of general anaesthesia, an ilio-inguinal nerve block was performed on the side of surgery using plain bupivicaine 0.25%, 0.25 ml kg–1 body weight, injected with a regional block needle at a point 1.5 cm medial to the anterior superior iliac spine. The needle was advanced until a pop was felt. After aspiration, half the bupivicaine was injected then the needle was redirected towards the anterior superior iliac spine and the remaining anaesthetic injected. Additional analgesia was given by the anaesthetist during surgery.
In the recovery room, the nurse assessed whether analgesia was adequate and gave appropriate additional analgesia if necessary. When the child was awake and completely comfortable they were asked to repeat the leg-raising test with each leg in turn. If the child was able to touch the ball with one leg but not the other, we considered this to be the result of leg weakness. If the child was unwilling to do the leg-raising test with either leg we excluded them from the study. In total 200 children were recruited, of whom 182 cooperated with the leg-raising test before and after surgery.
Analgesia was judged inadequate by the recovery nurse in six children and additional analgesia was given: morphine 0.1 mg kg–1 in one patient and acetaminophen suspension in three patients; the analgesia given to the other two patients was not recorded. No leg weakness was noted in the six children in whom analgesia was inadequate.
Of the 182 children who completed the leg-raising tests, 16 (8.8%, 95% confidence intervals 5.1–13.9%) had postoperative leg weakness on the side of the nerve block. There was no significant difference in the proportion of children with leg weakness in different age groups (Fisher’s exact two-sided test, P=0.57) nor was there a trend with age (
2 linear trend P=0.69).
All children with leg weakness were discharged on the same day (except one who was admitted because they were epileptic) with instructions to the parents to support or carry their child until they could bear their own weight safely. In all children the leg weakness had resolved by the next day when a follow-up telephone call was made.
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Comment |
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This study has shown that leg weakness can occur after ilio-inguinal nerve block in children. The weakness noted was in active knee extension, which is consistent with the theory that weakness after ilio-inguinal nerve block is the result of a femoral nerve block, as suggested by a cadaver study.5 In this study of three adult cadavers, methylene blue dye was injected sequentially into the plane superficial to transversus abdominis and then in the plane between transversus abdominis and transversalis fascia. When a volume of only 1 ml was injected deep to transversus abdominis, discoloration was noted around the femoral nerve. This study demonstrated that the needle tip only needs to be 2–3 mm deeper than desired for local anaesthetic to track around the fascial plane and lie around the femoral nerve, causing a block of that nerve.
The leg-raising test we used was specifically designed to demonstrate femoral nerve function to see if the theoretical situation described above occurs in practice. The apparent weakness was unlikely to be caused by pain as none of the children who were judged to be in pain showed leg weakness and those with leg weakness were all comfortable when they performed the leg-raising test.
We have shown that one in nine children who have had an ilio-inguinal nerve block have leg weakness afterwards, consistent with a femoral nerve block. We have also demonstrated a high level of compliance by children performing a postoperative leg-raising test that can be used to detect leg weakness.
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References |
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1 Szell K. Local anaesthesia and inguinal hernia repair; a cautionary tale. Ann R Coll Surg Engl 1994; 76: 139–40[Medline]
2 Rosario DJ, Skinner PP, Raftery AT. Transient femoral nerve palsy complicating preoperative ilioinguinal nerve blockade for inguinal herniorrhaphy. Br J Surg 1994; 81: 897[Web of Science][Medline]
3 Rosario D, Jacob S, Luntley J, Skinner P, Rafter A. Mechanism of femoral nerve palsy complicating percutaneous ilio-inguinal field block. Br J Anaesth 1997; 78: 314–18
4 Wildsmith J, Armitage E. Principles and Practice of Regional Anaesthesia. Edinburgh: Churchill Livingstone, 1993; 161–3
5 McNicol LR. A complication of ilio-inguinal block for inguinal hernia repair. Anaesthesia 1988; 43: 706
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