Lumbar neuraxial anatomical changes throughout pregnancy: a longitudinal study using serial ultrasound scans.

This observational study was designed to investigate the anatomical changes of the lumbar spine over the course of pregnancy using serial ultrasound scans. We performed paramedian scans on 58 women at the L2-3, L3-4 and L4-5 levels; these were done at four periods of 11+0-13+6, 19+0-23+0, 28+0-32+0 and 38+0-40+0 weeks gestation. At each intervertebral level, the length of the interlaminar space, length of the visible intervertebral posterior dura and depth of the posterior dura mater from the skin were measured. The length of the interlaminar space and length of the visible intervertebral posterior dura mater were longer, and the depth of the posterior dura mater was shallower, with ascending spinal interspace. The depth of the posterior dura mater increased during pregnancy, although it plateaued between the third and fourth measurement periods. The other spinal measurements were not affected by gestation. These findings indicate that the L2-3 level is the most appropriate puncture site for epidural anaesthesia in pregnant women. Our results ought to be embraced as a departure point towards developing neuraxial insertion techniques guided or aided by ultrasound.

Effective local anaesthetic volumes for sciatic nerve blockade: a clinical evaluation of the ED99.

Previous results in volunteers have indicated the effective dose in 99% of subjects (ED99 ) of local anaesthetic volume to be 0.10 ml.mm(-2) of cross-sectional nerve area for sciatic nerve blockade. The objective of this prospective, randomised, double-blind study was to investigate the ED99 of local anaesthetic for ultrasound-guided sciatic nerve blockade in patients undergoing foot surgery, according to Dixon's up-and-down method and probit analysis. A starting volume of 0.20 ml local anaesthetic per mm(2) cross-sectional nerve area was used. If surgical anaesthesia was judged to be adequate, the volume of local anaesthetic for the next case was reduced by 0.02 ml.mm(-2), until the first block failed. Thereafter, the volume of local anaesthetic was increased by 0.02 ml.mm(-2). The ED99 volume of local anaesthetic for ultrasound-guided sciatic nerve blockade was calculated to be 0.15 ml.mm(-2) cross-sectional nerve area, which is higher than the previously evaluated ED99 volume in volunteers.

Does circumferential spread of local anaesthetic improve the success of peripheral nerve block?

BACKGROUND: The relation between the pattern of local anaesthetic (LA) spread and the quality of peripheral nerve block is unclear. METHODS: Twenty-one volunteers were randomized to receive a median nerve block with intended circumferential or intended non-circumferential spread of LA. Different predetermined volumes and needle placement techniques were used to produce the different patterns of LA spread. Volumetric, multiplanar 3D ultrasound imaging was performed to evaluate the pattern and extent of LA spread. Sensory block was assessed at predetermined intervals. RESULTS: Complete circumferential spread of LA was achieved in only 67% of cases in the intended circumferential study group and in 33% of cases in the intended non-circumferential group. Block success was similar (90%) and independent of whether circumferential or non-circumferential spread of the LA was achieved. All block failures (n=4) occurred in the intended non-circumferential group with low volumes of LA. The onset of sensory block (independent of group allocation) was faster with circumferential spread of LA [median (IQR) onset time, 15 (8; 20) min] compared with non-circumferential spread of LA [median (IQR) onset time, 20 (15; 30) min]. More LA was used for circumferential blocks [median (IQR) volume of LA 2.8 (1.3; 3.6) vs 1.3 (1.1; 2.4) ml]. CONCLUSIONS: Even under optimal conditions, it was not possible to achieve circumferential spread of LA in all intended cases. The success of median nerve block seems to be independent of the pattern of LA spread. CLINICAL TRIAL REGISTRATION: DRKS 00003826.

Dexmedetomidine as an adjuvant to ropivacaine prolongs peripheral nerve block: a volunteer study.

BACKGROUND: Dexmedetomidine is an α-2-receptor agonist which might be used as an additive to local anaesthetics for various regional anaesthetic techniques. We therefore designed this prospective, double-blinded, controlled volunteer study to investigate the effects of dexmedetomidine as an adjuvant to ropivacaine on peripheral nerve block. METHODS: Ultrasound-guided ulnar nerve block (UNB) was performed in 36 volunteers with either 3 ml ropivacaine 0.75% (R), 3 ml ropivacaine 0.75% plus 20 µg dexmedetomidine (RpD), or 3 ml ropivacaine 0.75% plus systemic 20 µg dexmedetomidine (RsD). UNB-related sensory and motor scores were evaluated. RESULTS: Sensory onset time of UNB was not different between the study groups, whereas motor onset time was significantly faster in Group RpD when compared with the other study groups [mean (sd)] [21 (15) vs 43 (25) min in Group RsD and 47 (36) min in Group R, P<0.05 Group RpD vs other groups]. The duration of sensory block was 350 (54) min in Group R, 555 (118) min in Group RpD, and 395 (40) min in Group RsD (P<0.01 Group RpD vs other groups, P<0.05 Group RsD vs Group R). Motor block duration was similar to the duration of sensory block. CONCLUSIONS: A profound prolongation of UNB of ∼60% was detected with perineural dexmedetomidine when added to 0.75% ropivacaine. The systemic administration of 20 µg dexmedetomidine resulted in a prolongation of ∼10% during UNB with 0.75% ropivacaine. Eudra-CT No.: 2012-000030-19.

Clinical validation of a continuous non-invasive haemodynamic monitor (CNAP™ 500) during general anaesthesia.

BACKGROUND: We conducted a prospective study to test the validity of a new continuous non-invasive blood pressure (NIBP) monitor (CNAP) (CNAP™ Monitor 500). METHODS: One hundred patients undergoing elective surgery under general anaesthesia were included in the study after informed written consent. The CNAP finger cuffs were placed on the fingers of one arm, an arterial catheter was inserted into the same arm and data were recorded simultaneously. Agreement between invasive arterial pressure (IAP) and blood pressure obtained by CNAP was compared using the Bland-Altman method for repeated measurements. The data from the first 50 patients (software V3.0) were used to improve the software of the CNAP (software V3.5), which was then evaluated in another 50 patients. We defined a clinically acceptable agreement according to the standards of the American Association for the Advancement of Medical Instrumentation for NIBP measurements [limits of agreement (LOA) ± 15 mm Hg]. RESULTS: We analysed 524 878 paired measurements in 100 patients. The mean bias of the mean arterial pressure in the first 50 patients was -2.9 mm Hg (sd 10.6 mm Hg, LOA -23.7 to 17.9 mm Hg), and in the consecutive 50 patients (using software V3.5) the bias was -3.1 mm Hg (sd 9.5 mm Hg, LOA -21.6 to 15.4 mm Hg). CONCLUSIONS: The new CNAP monitor showed an agreement with the IAP that is promising but did not match our predefined criteria.

Ultrasound-guided cannulation of the great saphenous vein at the ankle in infants.

BACKGROUND: The establishment of peripheral venous access in infants is the most common invasive technique in paediatric anaesthesia. Venous puncture can be challenging due to the small size of vessels in this patient population. The present study was designed to investigate the practicability of ultrasound-guided vascular access to the great saphenous vein (GSV) at the level of the medial malleolus in infants ≤ 12 months. METHODS: Ninety consecutive infants ≤ 12 months undergoing elective surgery were included in this prospective study and divided into two age groups (0-6 and 7-12 months). After anaesthesia induction with sevoflurane, an ultrasound investigation of both GSVs at the level of the medial malleoli was performed. Subsequently, venous access in one GSV was established under direct ultrasound control. Anatomical ultrasound data and success rates of venous accesses were analysed. RESULTS: While not deeper relative to the skin, the GSV was significantly larger in older infants. The success rate in infants ≤ 6 months was 96%, whereas in older infants, the success rate was 100%. The overall success rate in all infants was 98%. CONCLUSIONS: Ultrasound facilitates venous puncture of the GSV in the vast majority of infants ≤ 12 months. Direct visualization via ultrasound is a promising technique for the establishment of venous access in the GSV at the level of the medial malleolus in infants.

Pharmacokinetics of the local anesthetic ropivacaine after transversus abdominis plane block in healthy volunteers.

PURPOSE: The transversus abdominis plane (TAP) block is a regional anesthetic technique used for pain control following abdominal surgical procedures. While a minimum of systemic side effects is usually expected after local anesthesia, it is unknown to which extent systemic absorption and redistribution to the abdominal wall contributes to the effects of anesthetics. The aim of this study was to determine concentration-time profiles of ropivacaine after the injection of 150 mg of ropivacaine into the lateral abdominal wall in various compartments. METHODS: The microdialysis technique was used to measure ropivacaine in plasma as well as at abdominal wall sites cranial from the injection site (below the 12th rip) and caudal from the injection site (cranial from the iliac crest) and in the skeletal muscle tissue of the contra lateral thigh of eight healthy volunteers. RESULTS: The mean exposure to ropivacaine measured as the area under the concentration-time curve was significantly higher at the two abdominal sites (240.9 ± 409.1  and 86.18 ± 133.50 µg h/mL, respectively) than in plasma (5.1 ± 1.0 µg h/mL) or in peripheral tissue (1.1 ± 1.2 µg h/mL). While the high mean concentrations of ropivacaine measured at the abdominal wall sites support the topical concept of the TAP block, the observed variability was striking. CONCLUSIONS: While the systemic pharmacokinetics was comparable between subjects, the local distribution of ropivacaine was highly variable after TAP block.

Does regional anaesthesia really improve outcome?

In recent decades, a number of studies have attempted to determine whether regional anaesthesia offers convincing benefits over general anaesthesia. However, today we interpret meta-analyses more carefully, and it remains unclear whether regional anaesthesia reduces mortality. However, regional anaesthesia offers superior analgesia over opioid-based analgesia, and a significant reduction in postoperative pain is still a worthwhile outcome. Recent developments in technical aspects of regional anaesthesia have the potential to provide significant advantages for many patients in all age groups. Moreover, studies focusing on specific outcomes have shown benefits for regional anaesthesia used for surgery and postoperative analgesia.

Ultrasound assessment of cranial spread during caudal blockade in children: the effect of different volumes of local anaesthetics.

BACKGROUND: Despite the large amount of literature on caudal anaesthesia in children, the issue of volume of local anaesthetics and cranial spread is still not settled. Thus, the aim of the present prospective randomized study was to evaluate the cranial spread of caudally administered local anaesthetics in children by means of real-time ultrasound, with a special focus on the effects of using different volumes of local anaesthetics. METHODS: Seventy-five children, 1 month to 6 yr, undergoing inguinal hernia repair or more distal surgery were randomized to receive a caudal block with 0.7, 1.0, or 1.3 ml kg(-1) ropivacaine. The cranial spread of the local anaesthetic within the spinal canal was assessed by real-time ultrasound scanning; the absolute cranial segmental level and the cranial level relative to the conus medullaris were determined. RESULTS: All the blocks were judged to be clinically successful. A significant correlation was found between the injected volume and the cranial level reached by the local anaesthetic both with regards to the absolute cranial segmental level and the cranial level relative to the conus medullaris. CONCLUSIONS: The main finding of the present study was positive, but numerically small correlation between injected volumes of local anaesthetic and the cranial spread of caudally administered local anaesthetics. Therefore, the prediction of the cranial spread of local anaesthetic, depending on the injected volume of the local anaesthetic, was not possible. EudraCT Number: 2008-007627-40.

Lateral ultrasound-guided paravertebral blockade: an anatomical-based description of a new technique.

BACKGROUND: Paravertebral blockade (PVB) is a regional anaesthetic technique with a large number of indications. PVB is usually performed with landmark-based techniques or methods that rely on pressure differences between the extra- and intraparavertebral space. This consecutive case series was designed to describe the ultrasound appearance of the lateral thoracic paravertebral space (PVS) and develop an ultrasound-guided method for PVB. METHODS: The PVS of 20 women undergoing breast cancer surgery was investigated with a high-frequency linear ultrasound transducer in the sitting position. After identification of the transverse process, internal intercostal membrane (IIM), and pleura at the T3 and T6 levels, the depths of the IIM and pleura, and the sagittal diameter of the PVS were determined. An out-of-plane needle guidance technique was used to perform the PVB with ropivacaine 0.75% (12 ml) at both levels. Successful blockade was determined by the ability to perform surgery under light general anaesthesia without opioids. RESULTS: Appropriate ultrasound identification of the IIM, transverse processes, and pleura was possible in all cases. Correct placement of the tip of the needle in the PVS resulted in successful PVB. No correlations of morphometric data with ultrasound measurements of the PVS were detected. CONCLUSIONS: After ultrasound identification of the boundaries of the lateral PVS, an out-of-plane needle guidance technique facilitated successful PVB. There were no clinically relevant correlations between morphometric data and ultrasound measurements.

Effect of earplugs on propofol requirement and awareness with recall during spinal anesthesia.

UNLABELLED: investigator either placed or did not place earplugs into the patients' ears (PLUG or noPLUG groups, respectively). Propofol requirements for stable sedation guided by the bispectral index and incidence of postoperative recall of intraoperative events were assessed in a double-blinded fashion. RESULTS: We found high but comparable propofol requirements in both groups (PLUG 4.4+/-1.2 vs. noPLUG 4.2+/-1.0 mg kg-1 h-1, p=NS). The incidence of intraoperative awareness was lower in the PLUG compared to the noPLUG group (16 vs. 56%; P<0.001). CONCLUSION: Although no sedative-sparing effect could be found in patients who wore earplugs during elective orthopedic surgery under spinal anesthesia, we nevertheless recommend using single-use paraffin wax earplugs. Beside their beneficial effect against potential harmful intraoperative noise, they reduce the incidence of intraoperative awareness with recall.

Great auricular nerve blockade using high resolution ultrasound: a volunteer study.

This prospective, observational volunteer study aimed to describe the appearance of the great auricular nerve using ultrasound and its blockade under ultrasound guidance. An in-plane needle guidance technique was used for blockade of the great auricular nerve with 0.1 ml mepivacaine 1%. Sensory block was evaluated by pinprick testing in comparison with the contralateral area propriae. The great auricular nerve was successfully seen in all volunteers and the tail of the helix, antitragus, lobula and mandibular angle were blocked in all cases whereas the antihelix and concha were never blocked. Ultrasound imaging of the great auricular nerve can be reliably achieved and successful blockade with minimal volumes of local anaesthetic is another example of the benefits of ultrasound-guided peripheral nerve blocks.

Caudal anaesthesia under sedation: a prospective analysis of 512 infants and children.

BACKGROUND: Caudal anaesthesia is a common procedure for infants and children undergoing subumbilical surgery, mostly performed in conjunction with general anaesthesia. Even if complications are rare, the risk of postoperative apnoea is significant, especially in infants born preterm or operated upon before 46 weeks of post-conceptual age. Caudal block in sedated, spontaneously breathing patients might be a safe alternative. METHODS: We investigated 512 infants and children. Premedication consisted of midazolam, sedation was induced with i.v. nalbuphine 0.1 mg kg(-1) and propofol 1 mg kg(-1), and maintained with propofol 5 mg kg(-1) h(-1) in children, if necessary. Caudal block was performed with ropivacaine 1 ml kg(-1) (0.2% or 0.35%). RESULTS: Data were obtained from 228 infants and 284 children. Median (IQR) age was 1.3 (0.2, 3.4) yr; median body weight was 10.0 (4.8, 15.3) kg. Two hundred and thirty-three (45.51%) were born preterm and 47 (9.18%) were operated upon before 46 weeks of post-conceptual age. Caudal block was successful in 98.05% and adverse events occurred in 7.03% patients. The incidence of adverse events was not higher in born preterm or operated upon before 46 weeks of post-conceptual age than in term born infants (P=0.35 and 0.35, respectively), or in infants vs children (P=0.61). There was no correlation between the incidence of adverse events and continuous sedation (P=0.07), coexisting diseases (P=0.11), or ASA classification (P=0.33). CONCLUSIONS: Caudal anaesthesia under sedation is associated with high success rates and a low incidence of adverse events, but requires careful and anticipatory perioperative management.

Fifteen years of ultrasound guidance in regional anaesthesia: part 1.

Ultrasound guidance for regional anaesthesia has gained enormous popularity in the past decade. The use of ultrasound guidance for many regional anaesthetic techniques is common in daily clinical practice, and the number of practitioners using it is increasing. However, alongside the enthusiasm, there should be a degree of informed scepticism. The widespread use of the various techniques of ultrasound-guided regional blocks without adequate training raises the danger of malpractice and subsequent impaired outcome. Adequate education in the use of regional block techniques under ultrasound guidance is essential. This review article addresses ultrasound guidance for regional anaesthesia, and is divided into two parts because of the size of the topic and the number of issues covered. This first part includes a review and preview of ultrasound guidance in regional anaesthesia and discusses all aspects of ultrasound for regional anaesthesia with a focus on recent technical developments, the positive implications in economics, further potential advantages (e.g. detection of anatomical variants, painless performance of blocks) and education. It also attempts to define a 'gold standard' in regional anaesthesia with the most recent findings in adequate volumes of local anaesthetics for peripheral nerve blocks. This standard should include an extraneural needle position, a high success rate, and wide application of ultrasound guidance in regional anaesthesia. The second part describes the impact of ultrasound on the development of nerve block techniques in the past 5 yr.

Minimal local anaesthetic volumes for sciatic nerve block: evaluation of ED 99 in volunteers.

BACKGROUND: This randomized, double-blinded volunteer study was designed to evaluate the ED(99) volume of local anaesthetic for sciatic nerve blocks using a step-up/step-down methodology. METHODS: A maximum of 20 volunteers were included to receive an ultrasound-guided sciatic nerve block with mepivacaine 1.5% and a starting volume of 0.2 ml mm(-2) cross-sectional nerve area. In cases of a complete sensory block, the volume was reduced by 0.02 ml mm(-2) cross-sectional nerve area until the first block failed. Thereafter, the volume of local anaesthetic was increased by 0.02 ml mm(-2) cross-sectional nerve area. After three cycles of successful/failed blocks, the ED(99) volume of local anaesthetic could be calculated by a probability function. The influence of the volumes of local anaesthetics on sensory onset times and duration of sensory block was evaluated by linear regression. RESULTS: The ED(99) volume of local anaesthetic for sciatic nerve block was calculated with 0.10 ml mm(-2) cross-sectional nerve area. The correlation between the volume of local anaesthetic and the sensory onset time was weak (r=0.14), whereas the correlation between the volume of local anaesthetic and the duration of sensory block was moderate (r=0.65). CONCLUSIONS: This is the first study where an ED(99) volume of local anaesthetic for sciatic nerve block has been evaluated. The resulting local anaesthetic volume of 0.10 ml mm(-2) cross-sectional nerve area seems to have no impact on sensory onset time, whereas the duration of sensory block is shorter.

Comparison of economical aspects of interscalene brachial plexus blockade and general anaesthesia for arthroscopic shoulder surgery.

BACKGROUND: This study investigated the cost-effectiveness of ultrasonographic-guided interscalene brachial plexus blockade (ISB) in comparison with general anaesthesia (GA) for arthroscopic shoulder surgery. METHODS: Forty patients undergoing arthroscopic shoulder surgery received either an ultrasonographic-guided ISB or GA. ISB was performed outside the operation room (OR) and patients were transferred in the OR at the earliest 20 min after block performance. All drugs and disposables were recorded to evaluate the costs for both techniques. The following anaesthesia-related times were defined: ready for surgical preparation (from arrival in the OR until end of anaesthesia induction), OR emergence time (from end of dressing until leaving the OR), anaesthesia control time (from patient's arrival in the OR until readiness for positioning plus time from the end of surgery to patient's discharge from the OR), and post-anaesthesia care unit (PACU) time (from patient's arrival in the PACU to the eligibility for discharge to normal ward). Personnel costs were excluded from statistical analysis. RESULTS: The total costs were [mean (sd)] 33 (9)euro for patients with ISB and 41 (7)euro for those who received GA (P<0.01). The anaesthesia-related workflow was improved in the ISB group when compared with the GA group [ready for surgical preparation 8 (3) vs 13 (5) min, P<0.001; OR emergence time 4 (3) vs 10 (5), P<0.001; anaesthesia control time 12 (4) vs 23 (6), P<0.001; and PACU time 45 (17) vs 70 (20), P<0.001]. CONCLUSIONS: Ultrasonographic-guided ISB is a cost-effective method for arthroscopic shoulder surgery.

Ultrasound-guided transversus abdominis plane block: description of a new technique and comparison with conventional systemic analgesia during laparoscopic cholecystectomy.

BACKGROUND: The transversus abdominis plane (TAP) block is usually performed by landmark-based methods. This prospective, randomized, and double-blinded study was designed to describe a method of ultrasound-guided TAP block and to evaluate the intra- and postoperative analgesic efficacy in patients undergoing laparoscopic cholecystectomy under general anaesthesia with or without TAP block. METHODS: Forty-two patients undergoing laparoscopic cholecystectomy were randomized to receive standard general anaesthetic either with (Group A, n=21) or without TAP block (Group B, n=21). Ultrasound-guided bilateral TAP block was performed with a high frequent linear ultrasound probe and an in-plane needle guidance technique with 15 ml bupivacaine 5 mg ml(-1) on each side. Intraoperative use of sufentanil and postoperative demand of morphine using a patient-controlled analgesia device were recorded. RESULTS: Ultrasonographic visualization of the relevant anatomy, detection of the shaft and tip of the needle, and the spread of local anaesthetic were possible in all cases where a TAP block was performed. Patients in Group A received significantly less [corrected] intraoperative sufentanil and postoperative morphine compared with those in Group B [mean (SD) 8.6 (3.5) vs 23.0 (4.8) microg, P<0.01, and 10.5 (7.7) vs 22.8 (4.3) mg, P<0.05]. CONCLUSIONS: Ultrasonographic guidance enables exact placement of the local anaesthetic for TAP blocks. In patients undergoing laparoscopic cholecystectomy under standard general anaesthetic, ultrasound-guided TAP block substantially reduced the perioperative opioid consumption.

Propofol-based sedation regimen for infants and children undergoing ambulatory magnetic resonance imaging.

BACKGROUND: Propofol is widely used for infants and children requiring sedation for magnetic resonance imaging. However, increased doses of propofol may quickly lead to an unintended deep sedation and respiratory depression. Thus, an appropriate low dosage, which nevertheless ensures sufficient sleep for successful magnetic resonance imaging (MRI) completion, would probably minimize respiratory adverse events. We investigated the safety and efficacy of a low-dose propofol-based sedation regimen in a broad age range of children. METHODS: We investigated 500 infants and children, prospectively. Premedication consisted of i.v. midazolam 0.1 mg kg(-1). Sedation was induced with i.v. nalbuphine 0.1 mg kg(-1) and propofol 1 mg kg(-1), and maintained with propofol 5 mg kg(-1) h(-1). Outcome measures were induction time, sedation time, recovery time, need for additional sedation, respiratory events, cardiovascular events, paradoxical reactions, and sedation failure. RESULTS: Data were obtained from 53 infants and 447 children. Median (IQR) age was 5.3 (4.5, 6.1) yr and body weight was 19.3 (16.5, 24.7) kg. The induction time was 2 (1, 2) min, sedation time 55 (45, 65) min, and recovery time 8 (8, 9) min. Additional sedation was necessary in 11 patients (2.2%), mild respiratory events occurred in five patients (1%). All MRI examinations could be completed without paradoxical reaction or sedation failure. CONCLUSION: This sedation regimen provides the shortest induction time so far described, a rare demand for additional sedation, a low incidence of respiratory events, and a rapid recovery.

Ultrasonographic guidance for sciatic and femoral nerve blocks in children.

BACKGROUND: Recent studies have shown that ultrasound guidance for paediatric regional anaesthesia can improve the quality of upper extremity and neuraxial blocks. We therefore investigated whether ultrasound guidance for sciatic and femoral nerve blocks prolongs sensory blockade in comparison with nerve stimulator guidance in children. METHODS: Forty-six children scheduled for surgery of one lower extremity were randomized to receive a sciatic and femoral nerve block under either ultrasound or nerve stimulator guidance. After induction of general anaesthesia, the blocks were performed using an ultrasound-guided multiple injection technique until the nerves were surrounded by levobupivacaine, or by nerve stimulator guidance using a predefined dose of 0.3 ml kg(-1) of levobupivacaine. An increase in heart rate of more than 15% of baseline during surgery defined a failed block. The duration of the block was determined from the injection of local anaesthetic to the time when the patient received the first postoperative analgesic. RESULTS: Two blocks in the nerve stimulator group failed. There were no failures in the ultrasound group. The duration of analgesia was longer in the ultrasound group mean (sd) 508 (178) vs 335 (169) min (P < 0.05). The volume of local anaesthetic in sciatic and femoral nerve blocks was reduced with ultrasound compared with nerve stimulator guidance [0.2 (0.06) vs 0.3 ml kg(-1) (P < 0.001) and 0.15 (0.04) vs 0.3 ml kg(-1) (P < 0.001), respectively]. CONCLUSIONS: Ultrasound guidance for sciatic and femoral nerve blocks in children increased the duration of sensory blockade in comparison with nerve stimulator guidance. Prolonged sensory blockade was achieved with smaller volumes of local anaesthetic when using ultrasound guidance.