Department of Anesthesiology, Nara Medical University, Nara, Japan. 1 Department of Anesthesiology, Izumisano Municipal Hospital, Izumisano, Osaka, Japan
* Corresponding author. E-mail: ne6n-ssok{at}asahi-net.or.jp
Accepted for publication September 24, 2004.
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Abstract |
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Methods. Ninety-eight children undergoing inguinal hernia repair were assigned randomly to receive either IG-IH nerve block (Group I) or IG-IH and genitofemoral nerve blocks (Group II). Systolic arterial pressure (SAP) and heart rate (HR) were recorded before surgery (control), after skin incision, at sac traction and at the end of surgery. Postoperative analgesic requirements and incidence of complications were recorded until discharge.
Results. At sac traction, SAP and HR were significantly higher in Group I (P<0.05), and the incidence of episodes of increased HR was also significantly higher in Group II (29 vs 12%, respectively, P<0.05). There were no significant differences in SAP and HR at other time points, postoperative analgesic requirements or incidence of complications between the groups.
Conclusions. The benefit of the additional genitofemoral nerve block to IG-IH nerve block was limited only to the time of sac traction without any postoperative effect. This suggests there is little clinical benefit in the addition of a genitofemoral nerve block.
Keywords: nerve block, genitofemoral ; nerve block, iliohypogastric ; nerve block, ilioinguinal ; surgery, inguinal hernia repair
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Introduction |
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It has been demonstrated that IG-IH and genitofemoral nerves have a variable origin, course, and distribution in the inguinal region.8 9 Consequently the inguinal region may also receive sensory innervation from the genitofemoral nerve. Genitofemoral entrapment neuralgia as a result of inguinal surgery has been reported.810 We therefore proposed that the addition of genitofemoral nerve block to IG-IH nerve block may improve the quality of analgesia for surgery in the inguinal region. The study prospectively investigated the additional efficacy of the genitofemoral nerve block to IG-IH nerve block for pain management in children undergoing inguinal hernia repair.
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Methods |
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We considered an increase of more than 10% in HR at skin incision or sac traction to be clinically relevant. Based on our previous studies and a pilot study and assuming an SD of 20 beats min1, a type 2 error protection of 0.05 and a power of 0.80, 49 patients in each group were required for appropriate study power. Continuous variables were expressed as mean (SD). Patient characteristics and haemodynamic variables before the surgery between the groups were compared using the Student's t-test. Percentage changes of SAP and HR were analysed by using two-way analysis of variance with repeated measurements, followed by StudentNewmanKeuls test for multiple comparisons. Categorical data are presented as absolute numbers (%) and were analysed by using Fisher's exact test or 2-test. A P-value <0.05 was considered statistically significant.
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Results |
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There were no significant differences in postoperative analgesic requirements and the incidence of complications between the groups (Table 2). No patient developed a haematoma related to the block during the study period.
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Discussion |
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The inguinal area receives sensory innervation from ilioinguinal, iliohypogastric, and genitofemoral nerves. The genital branch of the genitofemoral nerve generally passes along the psoas major through the internal inguinal ring. In male subjects, it descends behind the spermatic cord and supplies motor fibres to the cremasteric muscle and sensory fibres to a part of scrotal skin. In female subjects, it accompanies the round ligament and supplies partial sensation to the skin of the mons pubis and labium majus. Therefore, it has been considered that the addition of the genitofemoral nerve block would be effective in cases making incision in scrotal skin. However, previously published studies9 10 showed great variation in the sensory innervation of the inguinal region, with free communication between branches of the three nerves. Morikawa11 pointed out that only 37% of cases investigated were found to have the typical pattern, as described in textbooks. We therefore considered that incomplete effect of IG-IH nerve block in some patients might be due, in part, to the involvement of the genitofemoral nerve in the innervation of the inguinal region.
Back in 1980, von Bahr12 illustrated the anaesthetic techniques for inguinal herniorrhaphy, in which the IG-IH nerve block was combined with the genitofemoral nerve block. This suggested that the use of this combination technique was not uncommon at that time. Shandling and colleagues3 also reported genitofemoral nerve block along with IG-IH nerve block in some patients early in their series of inguinal heriotomy. However, this technique was abandoned later because it was of doubtful benefit and constituted a potential cause of haematoma formation within the cord. Subsequently there have been no reports of genitofemoral nerve block for inguinal hernia repair.
To the best of our knowledge, this is the first report to evaluate the efficacy of the additional genitofemoral nerve block to the IG-IH nerve block during inguinal hernia repair. The results suggested that genitofemoral nerve may be also involved in nociceptive afferent inputs during the inguinal hernia repair and the addition of the genitofemoral nerve may be useful at the time of sac traction, in some cases. However, as the incidence of episodes of increased SAP and HR in response to sac traction was 19 and 29%, respectively, in Group I, this implies that 7181% of patients, without such haemodynamic changes, did not require the additional genitofemoral nerve block. The benefit of the genitofemoral nerve block was noted only at the time of sac traction. There were no postoperative benefits of the addition of the genitofemoral nerve block, which suggests any clinical advantage of adding a genitofemoral nerve block to IG-IH nerve block appears is minimal.
Although, in this study, the addition of a genitofemoral nerve block did not produce any adverse effects, possible effects such as cord haematoma3 should be kept in mind. Although the exact incidence of adverse effects with the addition of the genitofemoral nerve block is unknown, its indication should be carefully determined considering the risk of such sequela.
In summary, the addition of a genitofemoral nerve block attenuated the SAP and HR responses at sac traction, suggesting that it may be involved in nociceptive afferent input during inguinal hernia repair. However, benefit was noted only at the sac traction and not after the operation. This block is unlikely to be of great clinical use for children undergoing common inguinal hernia repair.
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References |
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