Feasibility of ultrasound measurement in a human model of acute compartment syndrome.

BACKGROUND: Early diagnosis of acute compartment syndrome (ACS) of the leg is essential to improve the outcome. Direct invasive measurement is currently recommended to measure intracompartmental pressure. A non-invasive and reproducible means of making the diagnosis would be a step forward. The purpose of this exploratory study was to investigate the feasibility of non-invasive ultrasound-guided angle measurement as a surrogate of increased pressure in a model of ACS. METHODS: A model of ACS was generated by infusion of saline into the anterior compartment of the leg of human cadavers to incrementally increase the intracompartmental pressure from 10 to 100 mmHg. In 40 legs (20 cadavers), the angle (TFA, tibia-fascia angle) between the anterolateral cortex of the tibia and the fascia of the anterior compartment was measured at each 10 mmHg pressure increase using ultrasound in a standardized transversal plane. A multilevel linear regression model was used to estimate intracompartmental pressure from delta TFA (ΔTFA). RESULTS: TFA (mean [± SD]) increased from 61.0° (± 12.0°) at 10 mmHg up to 81.1° (± 11.1°) at 100 mmHg compartment pressure. Each increase ΔTFA by one degree was associated with an increase in pressure by 3.9 mmHg (95% CI, 3.8-4.0, p < 0.001). CONCLUSIONS: We found that intracompartmental pressure of the anterior compartment of the calf can be well estimated by ultrasound-based ΔTFA in this post mortem experiment. Our findings indicate that non-invasive TFA measurement is feasible and it is reasonable that this will hold true in real life, but the findings are too preliminary to be used in clinical practice now.

Use of ropivacaine and lidocaine for axillary plexus blockade.

OBJECTIVE: The use of certain peripheral nerve blocks in paediatric patients is gaining increasing popularity, although distinctive characteristics of the juvenile anatomy, psychological barriers, time constraints on block placement, and risks of neurotoxic and cardio toxic side effects are still mentioned. However, newer agents like Ropivacaine and Levobupivacaine seem to offer excellent alternatives to Bupivacaine and Lidocaine, especially for use in paediatric patients. MATERIALS AND METHODS: We evaluated Ropivacaine 0.5% and Lidocaine 1.0% using axillary plexus blockade as a single-shot technique in 50 children in the age group of 2 to 10 years and undergoing short upper limb surgery. The primary objectives were to compare onset time, duration and quality of block and the incidence of breakthrough pain. RESULTS: Onset time was longer in the Ropivacaine group (15.4 minutes) than in the Lidocaine group (8.2 minutes). The duration of the effect was greater in patients in the Ropivacaine group (337 minutes) than in the Lidocaine group (137 minutes). Duration appeared to vary with patient's age but this effect was not statistically significant. CONCLUSION: Axillary plexus anaesthesia provides satisfactory perioperative pain relief in infants undergoing short-trauma surgery. Apart from its safety, these results underline that Ropivacaine 0.5% can be recommended for axillary brachial plexus block in children.

Ultrasonographic guidance improves the success rate of interscalene brachial plexus blockade.

BACKGROUND AND OBJECTIVES: The use of ultrasonography in regional anesthetic blocks has rapidly evolved over the past few years. It has been speculated that ultrasound guidance might increase success rates and reduce complications. The aim of our study is to compare the success rate and quality of interscalene brachial plexus blocks performed either with direct ultrasound visualization or with the aid of nerve stimulation to guide needle placement. METHODS: A total of 160 patients (American Society of Anesthesiologists physical status classification I-III) scheduled for trauma-related upper arm surgery were included in this randomized study and grouped according to the guidance method used to deliver 20 mL of ropivacaine 0.75% for interscalene brachial plexus blockade. In the ultrasound group (n = 80), the brachial plexus was visualized with a linear 5 to 10 MHz probe and the spread of the local anesthetic was assessed. In the nerve stimulation group (n = 80), the roots of the brachial plexus were located using a nerve stimulator (0.5 mA, 2 Hz, and 0.1 millisecond bandwidth). The postblock neurologic assessment was performed by a blinded investigator. RESULTS: Sensory and motor blockade parameters were recorded at different points of time. Surgical anesthesia was achieved in 99% of patients in the ultrasound vs 91% of patients in the nerve stimulation group (P < .01). Sensory, motor, and extent of blockade was significantly better in the ultrasound group when compared with the nerve stimulation group. CONCLUSIONS: The use of ultrasound to guide needle placement and monitor the spread of local anesthetic improves the success rate of interscalene brachial plexus block.

Ilioinguinal/iliohypogastric blocks in children: where do we administer the local anesthetic without direct visualization?

BACKGROUND: Ultrasonographic observation of peripheral nerve blocks enables direct visualization of the spread of local anesthetic around the targeted nerves. Similarly, ultrasonography may be used to determine the site of local anesthetic placement when landmark-based techniques are used. We performed a study to determine the actual location of local anesthetic when ilioinguinal/iliohypogastric nerve blocks are performed using landmark-based techniques in children in an attempt to explain a failed block. METHODS: After induction of general anesthesia (1 minimum alveolar anesthetic concentration halothane and laryngeal mask airway), 62 children scheduled for inguinal surgery received an ilioinguinal/iliohypogastric nerve block based on standard anatomical landmarks. Ultrasonography was then used to determine the actual location of local anesthetic placement. The anesthesiologist performing the block was blinded to the ultrasonographic investigation. Successful blocks were recorded either when the local anesthetic surrounded the nerves or were based on clinical signs after skin incision. RESULTS: In 14% of the blocks, the local anesthetic was administered correctly around the nerves resulting in successful blocks. In the remaining 86%, the local anesthetic was administered in adjacent anatomical structures (iliac muscle 18%, transverse abdominal muscle 26%, internal oblique abdominal muscle 29%, external oblique abdominal muscle 9%, subcutaneous 2%, and peritoneum 2%), and 45% of these blocks failed. CONCLUSION: Accurate placement of local anesthetic around the ilioinguinal/iliohypogastric nerves in children is seldom possible when landmark-based techniques are used. In the majority of patients, the local anesthetic was inaccurately placed in adjacent anatomical structures with unpredictable block results.

Epidural catheter placement in neonates: sonoanatomy and feasibility of ultrasonographic guidance in term and preterm neonates.

BACKGROUND: We report the first prospective sonoanatomic study in neonates with the aim to perform ultrasonographic-guided epidural catheter placement in this age group. METHOD: One hundred forty-five neonates with a body weight < or =4 kg (0.53-4 kg) were included in this prospective study. The study was divided into 3 consecutive parts. In the first part, the neuraxial sonoanatomy of 60 neonates was evaluated. In the second part, 50 neonates scheduled for major abdominal surgery were enrolled. In this part, the depth of the ligamentum flavum measured with ultrasound was matched up to the depth evaluated clinically with the loss-of-resistance technique. In the third part, ultrasonographic epidural catheter placement was performed in 35 neonates weighing between 620 g and 4 kg. RESULTS: The ligamentum flavum, the dura mater, and the termination of the spinal cord could be identified in all patients. The first part showed a good correlation between body weight and depth of the ligamentum flavum. The median termination of the spinal cord corresponded to vertebral level L2. The second part confirmed a good correlation between depth of the ligamentum flavum evaluated clinically and the depth predicted with ultrasound. Finally, real-time ultrasound-guided epidural placement was possible in all 35 neonates. CONCLUSION: Ultrasound examination of the spinal cord anatomy provides valuable information for epidural catheter placement in neonates. Ultrasonography enables a real-time identification of the tip of the needle within the epidural space and a visualization of the spread of local anesthetic in these patients.

Pilot study of neuraxial imaging by ultrasound in infants and children.

BACKGROUND: Ultrasonography is becoming an important adjunct in regional anesthesia. Epidural anesthesia may pose significant challenges in infants and children because of difficulties in identifying the epidural space. In addition, epidural catheters are sometimes difficult to advance. The present study was performed to evaluate an optimal ultrasound technique for direct visualization of neuraxial structures in children. METHODS: A total of 32 infants and children scheduled for minor surgery were prospectively included in a high-resolution ultrasound study. Scans were performed using either a sector or linear probe and views from a longitudinal paramedian, median and transversal angle at lumbar and thoracic levels of the spinal cord were analyzed. RESULTS: In all children investigated, the linear probe generated better images than the sector probe. Of the various scanning perspectives, the paramedian longitudinal approach offered the best views at both cord levels. Broken down by age groups, the best visibility was clearly obtained in neonates up to 3 months of age (P < 0.0001 Vs all other age groups). In older children, the quality of ultrasound decreased in an age-dependent manner. CONCLUSIONS: Paramedian longitudinal scans with linear probes are the most favorable method of imaging neuraxial anatomy at lumbar and thoracic cord levels in infants and children, with the best results in neonates up to 3 months of age. Based on these results, and using real time imaging, a practical technique for ultrasound-guided epidural anesthesia for neonates and infants at lumbar and thoracic levels of the spinal cord is planned.

Ultrasound-guided lumbar facet nerve block: a sonoanatomic study of a new methodologic approach.

BACKGROUND: Lumbar facet nerve (medial branch) block for pain relief in facet syndrome is currently performed under fluoroscopic or computed tomography scan guidance. In this three-part study, the authors developed a new ultrasound-guided methodology, described the necessary landmarks and views, assessed ultrasound-derived distances, and tested the clinical feasibility. METHODS: (1) A paravertebral cross-axis view and long-axis view were defined under high-resolution ultrasound (15 MHz). Three needles were guided to the target point at L3-L5 in a fresh, nonembalmed cadaver under ultrasound (2-6 MHz) and were subsequently traced by means of dissection. (2) The lumbar regions of 20 volunteers (9 women, 11 men; median age, 36 yr [23-67 yr]; median body mass index, 23 kg/m2 [19-36 kg/m2]) were studied with ultrasound (3.5 MHz) to assess visibility of landmarks and relevant distances at L3-L5 in a total of 240 views. (3) Twenty-eight ultrasound-guided blocks were performed in five patients (two women, three men; median age, 51 yr [31-68 yr]) and controlled under fluoroscopy. RESULTS: In the cadaver, needle positions were correct as revealed by dissection at all three levels. In the volunteers, ultrasound landmarks were delineated as good in 19 and of sufficient quality in one (body mass index, 36 kg/m2). Skin-target distances increased from L3 to L5, reaching statistical significance (*, **P < 0.05) between these levels on both sides: L3r, 45+/-6 mm*; L4r, 48+/-7 mm; L5r, 50+/-6 mm*; L3l, 44+/-5 mm**; L4l, 47+/-6 mm; L5l, 50+/-6 mm**. In patients, 25 of 28 ultrasound-guided needles were placed accurately, with the remaining three closer than 5 mm to the radiologically defined target point. CONCLUSION: Ultrasound guidance seems to be a promising new technique with clinical relevance and the potential to increase practicability while avoiding radiation in lumbar facet nerve block.

Thoracic epidural anesthesia increases tissue oxygenation during major abdominal surgery.

UNLABELLED: Intraoperative surgical stress may markedly increase adrenergic nerve activity and plasma catecholamine concentrations, which causes peripheral vasoconstriction and decreased tissue oxygen partial pressure possibly leading to tissue hypoxia. Tissue hypoxia is associated with an increased incidence of surgical wound infections. Thoracic epidural anesthesia blocks afferent neural stimuli and inhibits efferent sympathetic outflow in response to painful stimuli. Consequently, we tested the hypothesis that supplemental thoracic epidural anesthesia during major abdominal surgery improves tissue perfusion and subcutaneous oxygen tension. Thirty patients were randomly assigned to two groups: general (n = 15) or combined general and epidural anesthesia (n = 15). Anesthesia technique and fluid management were standardized. Subcutaneous tissue oxygen tension was measured continuously in the upper arm with a Clark type electrode. Data were compared with unpaired, two-tailed t-tests, Wilcoxon's ranked sum test, or repeated-measures analysis of variance and Scheffé F tests as appropriate; P < 0.05 was considered statistically significant. After 60 min, intraoperative tissue oxygen tension was significantly larger during combined anesthesia than during general anesthesia (54.3 +/- 7.4 mm Hg versus 42.1 +/- 8.6 mm Hg; P = 0.0002). Subcutaneous tissue oxygen tension remained significantly higher in the combined general/epidural anesthesia group throughout the observation period. Hemodynamic responses and global oxygen variables were similar in the groups. Thoracic epidural anesthesia improved intraoperative tissue oxygen tension outside the area of the epidural block. Thus, our results give evidence that supplemental neural nociceptive block blunts generalized vasoconstriction caused by surgical stress and adrenergic responses. IMPLICATIONS: Thoracic epidural anesthesia blunts the decrease of subcutaneous tissue oxygen tension caused by surgical stress and adrenergic vasoconstriction during major abdominal surgery. Consequently, combined general and epidural anesthesia helps to provide sufficient tissue oxygenation.

Onset time, quality of blockade, and duration of three-in-one blocks with levobupivacaine and bupivacaine.

Levobupivacaine is the isolated S(-)-stereoisomer of racemic bupivacaine. Important pharmacodynamic properties of levobupivacaine have not been determined for the femoral three-in-one block. In this randomized, controlled, double-blinded trial, we studied 60 ASA physical status I-III patients scheduled for surgery of the lower limb. A nerve-stimulator-guided three-in-one block was performed as supplemental analgesic therapy with 20 mL of bupivacaine 0.5% (n = 20), levobupivacaine 0.5% (n = 20), or levobupivacaine 0.25% (n = 20). Sensory onset time, quality of blockade, and duration of blockade were assessed by pinprick test in the central sensory innervation region of the femoral nerve (distribution of the anterior femoral cutaneous nerve). A rating scale from 100% (normal sensation) to 0% (no sensation at all) as compared with the contralateral leg was used. No significant difference in sensory onset time among the three local anesthetic solutions was observed (mean [95% confidence interval]): bupivacaine 0.5%, 27 min (20-33 min); levobupivacaine 0.5%, 24 min (18-30 min); and levobupivacaine 0.25%, 30 min (23-36 min) (P = 0.49). The analgesic quality of the blockade was also not significantly different among the three groups, whereas a complete sensory block was achieved in significantly fewer patients in the levobupivacaine 0.25% group (P = 0.02). The duration of blockade was significantly shorter with levobupivacaine 0.25% compared with the other groups: bupivacaine 0.5%, 1053 min (802-1304 min); levobupivacaine 0.5%, 1001 min (844-1158 min); and levobupivacaine 0.25%, 707 min (551-863 min) (P = 0.01). Levobupivacaine 0.5% is recommended instead of bupivacaine 0.5% for the three-in-one block.