1 Department of Anaesthesia and Intensive Care Medicine, Medical University of Vienna, A-1090 Vienna, Austria. 2 Department of Anaesthesia, University Cape Town, Red Cross Children Hospital, Klipfontein Rd, Rondebosch 7700, South Africa. 3 Division of Anaesthesia and Intensive Care Medicine, Orthopaedic Hospital Gersthof, A-1180 Vienna, Austria
* Corresponding author: Department of Anaesthesia and Intensive Care Medicine, Medical University of Vienna, Währinger Gürtel 1820, A-1090 Vienna, Austria. E-mail: peter.marhofer{at}meduniwien.ac.at
Accepted for publication March 24, 2005.
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Abstract |
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Methods. One hundred children (age range, 1 month8 years) scheduled for inguinal hernia repair, orchidopexy or hydrocele repair were included in the study. Following induction of general anaesthesia, the children received an ilioinguinal/iliohypogastric block performed either under ultrasound guidance using levobupivacaine 0.25% until both nerves were surrounded by the local anaesthetic or by the conventional fascial click method using levobupivacaine 0.25% (0.3 ml kg1). Additional intra- and postoperative analgesic requirements were recorded.
Results. Ultrasonographic visualization of the ilioinguinal/iliohypogastric nerves was possible in all cases. The amount of local anaesthetic used in the ultrasound group was significantly lower than in the fascial click group (0.19 (SD 0.05) ml kg1 vs 0.3 ml kg1, P<0.0001). During the intraoperative period 4% of the children in the ultrasound group received additional analgesics compared with 26% in the fascial click group (P=0.004). Only three children (6%) in the ultrasound-guided group needed postoperative rectal acetaminophen compared with 20 children (40%) in the fascial click group (P<0.0001).
Conclusions. Ultrasound-guided ilioinguinal/iliohypogastric nerve blocks can be achieved with significantly smaller volumes of local anaesthetics. The intra- and postoperative requirements for additional analgesia are significantly lower than with the conventional method.
Keywords: anaesthesia, paediatric ; monitoring, ultrasonography ; nerve block, ilioinguinal/iliohypogastric
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Introduction |
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Ultrasonographic guidance of peripheral nerve blocks of both the upper and lower extremities in adults7 8 reduces the number of complications and improves the quality of the blocks. Recently, direct ultrasonographic visualization of the brachial plexus in children was shown to improve sensory and motor block, as well as the speed of onset and duration of sensory blockade, in lateral infraclavicular brachial plexus blocks when compared with those performed using a nerve stimulator.9
Direct ultrasonographic visualization of the inguinal and iliohypogastric nerves might improve the quality of the block and reduce the risk of complications. Therefore we designed a randomized prospective double blinded clinical study to compare the efficacy of ultrasound-guided ilioinguinal/iliohypogastric nerve blocks with the conventional blind technique.
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Methods |
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Before induction of anesthesia children were randomized into two groups. The randomization was performed outside the study centre and delivered in sealed opaque envelopes which were numbered sequentially. According to the randomization children received an ilioinguinal block using the traditional fascial click method (fascial click group) or an ultrasound-guided ilioinguinal block (ultrasound group).
Premedication was given at the discretion of the anaesthesiologist and consisted of oral midazolam 0.5 mg kg1. General anaesthesia was induced with 8% sevoflurane via a facemask. After establishing venous access, a laryngeal mask was placed and anaesthesia was maintained with 1 MAC halothane in nitrous oxide and oxygen. Intraoperative monitoring included ECG, heart rate, pulse oximetry, non-invasive blood pressure and end tidal carbon dioxide concentration.
In the ultrasound group, a SonoSite 180plus portable ultrasound unit (SonoSiteTM, Bothell, WA, USA) and a 510 MHz linear hockey stick probe were used to identify the targeted nerves and surrounding anatomical structures. Adjustments (depth, probe frequency, low and far gain) were performed in order to achieve optimal ultrasonographic figures of the nerves and the surrounding anatomical structures (muscles, peritoneum). Figure 1 shows the position of the probe and the needle relative to the skin, Figure 2 shows an example of the ultrasonographic views of the ilioinguinal nerve and the muscles of the anterior abdominal wall in a cross-sectional view, and Figure 3 shows the ultrasonographic view of the tip of the needle relative to the ilioinguinal nerve.
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Following aseptic preparation of both the puncture site and the ultrasonographic probe, the nerve block was performed using an insulated 22-gauge 40-mm needle with a facette tip and an injection line (PajunkTM, Geisingen, Germany). Once the needle had been visualized by ultrasound and placed in an optimal position relative to the nerves, a single injection of levobupivacaine 0.25% (ChirocaineTM, Abbott, Roscrea, Ireland) was administered under real-time ultrasound control until both nerves were surrounded by the local anaesthetic (Fig. 4). The amount administered was recorded.
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In both groups skin incision was performed 15 min after the block. On completion of skin closure, the laryngeal mask was removed and the general anaesthesia discontinued. Heart rate, and the OPS score (see below) were monitored in the recovery room.
An intraoperative decrease in mean arterial pressure and heart rate >30% from baseline was defined as hypotension or bradycardia, respectively, and were treated with a bolus infusion of fluid. If this was unsuccessful, a vasoconstrictor (etilefrine [EffortilTM] 0.02 mg kg1 or atropine 0.01 mg kg1) was administered as indicated. Respiratory depression was defined as a decrease in to <93% and requiring supplementary oxygen. An increase in heart rate or mean arterial pressure of >10% following skin incision and during surgery was defined as insufficient analgesia and treated with fentanyl 3 µg kg1 i.v.
The efficacy of postoperative analgesia was measured using the OPS score, in which objective behavioural variables (crying, facial expression, position of torso and legs, motor restlessness) are assessed. Each pain variable is scored on a three-point scale (1=none, 2=moderate, 3=severe) to give a maximum cumulative score of 15. If the OPS score was 11 in two subsequent measurements, the child received acetaminophen 40 mg kg1 rectally. Duration of the local analgesia was defined as the time from completion of the ilioinguinal/iliohypogastric nerve blocks to the first administration of rescue analgesia. The time to discharge from the hospital was also recorded.
Statistical analysis
All values are expressed as mean (SD). Differences in demographics, surgical time, time to discharge and amount of local anaesthetic used were evaluated using an independent t-test. To detect intergroup differences in haemodynamic changes ANOVA for repeated measurements was used. Intergroup differences in the frequency of postoperative acetaminophen use, the need for additional systemic analgesia at skin incision and the frequency of the nerve being found within the local anaesthetic were evaluated using the 2-test. Based on preliminary data we expected a 50% difference between the two groups in block sufficiency. Therefore we calculated an n=100 to detect this difference with P<0.05 and a power of 90%. Correlations were calculated using the Pearson correlation coefficient (SPSS 11.1.2, SPSS Inc., Chicago, IL). The level of statistical significance was set at P
0.05.
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Results |
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Only three children (6%) in the ultrasound-guided group needed postoperative rectal acetaminophen compared with 20 children (40%) in the fascial click group (P<0.0001).
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Discussion |
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In this study the precise administration of lower volumes of local anaesthetic under ultrasound guidance resulted in effective ilioinguinal/iliohypogastric nerve blocks in children, with a reduced failure rate and no complications. Despite its popularity, when conventional methods are used, the ilioinguinal/iliohypogastric nerve block only has a success rate of 7080% in some published series.3 Several complications such as colonic or small bowel puncture,45 pelvic haematoma,6 femoral nerve palsy and quadriceps muscle paresis1012 have been described. Possible reasons for the relatively poor success rate of the fascial click method include imprecise description of the landmarks (e.g. 12 finger breadths medial to the anterior superior iliac spine, quarter of the distance along the line from the anterior superior iliac spine to the umbilicus). Insufficient understanding of the anatomical landmarks may also be a factor and an explanation for some complications.13
The relationship of the ilioinguinal/iliohypogastric nerves to the abdominal muscles varies relative to the anterior superior iliac spine.13 14 At the lateral border of the quadratus lumborum muscle, the two nerves pierce the lumbar fascia to reach a plane between the internal oblique abdominal muscle and the transverse abdominal muscle. The iliohypogastric nerve is situated superiorly and continues ventrally between the internal and external oblique abdominal muscles.
High-resolution imaging of the ilioinguinal/iliohypogastric nerves with the high-frequency linear probe was possible in all our patients. The nerves were found in close proximity to one another between the internal oblique and transverse abdominal muscles. Importantly, in 50% of the patients only two muscle layers could be identified by ultrasound in this area where the external oblique abdominal muscle is only aponeurosis. There was no correlation between the position of the nerves in relation to the anterior superior iliac spine, the depth of the nerves or the distance from the nerves to the peritoneum. An important finding in our study is the close proximity of the nerves to the peritoneum, i.e. a distance of 3.3 (1.3) mm (shortest distance, 1 mm). This emphasizes the risk of undetected peritoneal puncture when using the fascial click method. This may contribute to failed blocks and is a strong argument for the use of ultrasound guidance in young children.
By using real-time imaging, as in previous studies,15 the precise location of the needle tip between the ilioinguinal and iliohypogastric nerves and within the correct fascial plane could be detected and the spread of the local anaesthetic around both nerves could be observed. In this way significantly smaller amounts of local anaesthetics were used and clinically effective blocks were still achieved. This is particularly relevant for neonates and infants who are at risk of local anaesthetic toxicity and higher free plasma concentrations of local anaesthetic agents in view of their lower plasma concentration of the binding protein alpha-1 acid glycoprotein.16 The results of this study are encouraging and demonstrate a further application of the use of ultrasonography in paediatric regional anaesthesia. Recently, other investigators have used ultrasound to elucidate sciatic nerve anatomy17 and neuraxial anatomy,18 and for infraclavicular brachial plexus blocks.9 Ultrasound guidance of ilioinguinal/iliohypogastric nerve blocks proved easy to perform using the portable Sonosite 180plus ultrasound unit.
In summary, ultrasound guidance of ilioinguinal/iliohypogastric nerve blocks offers the advantage of direct visualization of the nerves and the adjacent anatomical structures. The real-time imaging of the local anaesthetic spread around the nerves maintains the quality of the block whilst significantly reducing the amounts of local anaesthetic required compared with the recommended dose for the conventional methods. We recommend the use of ultrasonography for ilioinguinal/iliohypogastric nerve blocks, particularly in small infants and children.
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Acknowledgments |
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Footnotes |
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References |
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17 Schwemmer U, Markus CK, Greim CA, et al. Sonographic imaging of the sciatic nerve and its division in the popliteal fossa in children. Paediatr Anaesth 2004; 14: 10058[CrossRef][Medline]
18 Marhofer P, Bösenberg A, Sitzwohl C, et al. A pilot study of neuraxial imaging by ultrasound in infants and children. Paediatr Anaesth 2005; in press
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