M.J.M. Gielen

Ultrasound-guided low-dose interscalene brachial plexus block reduces the incidence of hemidiaphragmatic paresis.

Background and Objectives: Interscalene brachial plexus block is associated with 100% incidence of hemidiaphragmatic paresis as a result of phrenic nerve block. We examined whether an ultrasound (US)-guided interscalene brachial plexus block performed at the level of root C7 versus a nerve stimulation interscalene brachial plexus block, both using 10 mL of ropivacaine 0.75%, resulted in a lower incidence of hemidiaphragmatic paresis. Methods: In a prospective randomized controlled trial, 30 patients scheduled for elective shoulder surgery under combined general anesthesia and interscalene brachial plexus block were included. Interscalene brachial plexus block using the same dose was performed using either US or nerve stimulation guidance of ropivacaine for both groups. General anesthesia was standardized. Ventilatory function was assessed using spirometry, and movement of the hemidiaphragm was assessed by US. Results: Two patients in the US group showed complete paresis of the hemidiaphragm, but in the nerve stimulation group, 12 patients showed complete and 2 patients had partial paresis of the hemidiaphragm (13% versus 93%, respectively; P < 0.0001). Ventilatory function (forced expiratory volume at 1 second, forced vital capacity, and peak expiratory flow) was significantly reduced in the nerve stimulation group compared with the US-guided group (P < 0.05). One block failure occurred in the nerve stimulation group compared with none in the US group. No adverse effects occurred in either group. Conclusions: Ultrasound-guided interscalene brachial plexus block performed at the level of root C7 using 10 mL of ropivacaine 0.75% reduces the incidence of hemidiaphragmatic paresis.

Minimum effective volume of local anesthetic for shoulder analgesia by ultrasound-guided block at root C7 with assessment of pulmonary function.

Background and Objectives: This study was performed to determine the minimum effective volume of ropivacaine 0.75% required to produce effective shoulder analgesia for an ultrasound (US)-guided block at the C7 root level with assessment of pulmonary function. Methods: Using the Dixon and Massey up-and-down method study design, 20 patients scheduled for elective open shoulder surgery under combined general anesthesia and continuous interscalene brachial plexus block were included. Initial volume of ropivacaine 0.75% was 6 mL; block success or failure determined a 1-mL decrease or increase for the subsequent patient, respectively. General anesthesia was standardized. A continuous infusion of ropivacaine 0.2% was started at a rate of 6 mL/hr at 2 hrs after completion of surgery. Ventilatory function was assessed using spirometry, and movement of the hemidiaphragm was assessed by US. Results: The minimum effective volume of local anesthetic in 50% and 95% of the patients was 2.9 mL (95% confidence interval, 2.4-3.5 mL) and 3.6 mL (95% confidence interval, 3.3-6.2 mL), respectively. Ventilatory function and hemidiaphragmatic movement was not reduced up to and including 2 hrs after completion of surgery, but 22 hrs after start of the continuous infusion of ropivacaine 0.2%, ventilatory function and hemidiaphragmatic movement were significantly reduced (P < 0.001). Conclusions: The minimum effective volume of local anesthetic for shoulder analgesia for a US-guided block at the C7 root level in 50% and 95% of the patients was 2.9 and 3.6 mL, respectively. Pulmonary function was unchanged until 2 hrs after completion surgery, but reduced 22 hrs after start of a continuous infusion of ropivacaine 0.2%.

Intravenous regional anesthesia with 0.5% articaine, 0.5% lidocaine, or 0.5% prilocaine : a double-blind randomized clinical study

Background and Objectives. The purpose of this study was to compare the effectiveness of three local anesthetic agents for intravenous regional anesthesia in the upper limb. Side effects and plasma concentrations of the drugs in the doses administered for IVRA were also studied. Methods. Thirty patients in ASA groups I and II received intravenous regional anesthesia for surgery of the upper limb. In a double‐blind prospective study, they were randomly allocated to receive one of three local anesthetics: articaine, lidocaine, or prilocaine. Patients received 40 mL of a 0.5% solution of the local anesthetic. The onset time of sensory block was assessed by pinprick and the extent of motor block was was scored as 0‐3. Plasma concentrations of local anesthetics were determined in all patients from serial arterial blood samples drawn at predetermined times before and after tourniquet release. Results. The onset time of sensory block was significantly shorter (2.5 minutes) in the articaine group than in the lidocaine group (11.1 minutes) or the prilocaine group (10.9 minutes) (Scheffe, P < .05). Development of motor block was equal in all three groups (score 2). Estimation of plasma concentrations by high performance liquid chromatography showed that the peak level in all 30 patients was reached immediately after release of the tourniquet; plasma concentrations thereafter gradually declined. Maximum concentrations of articaine, lidocaine, and prilocaine were, 1.85, 8.5, and 4.4 μg/mL, respectively. No signs of local anesthetic toxicity of the cardiovascular or central nervous systems were seen. Conclusion. Articaine had the fastest onset of sensory block and the lowest peak plasma concentration of the three local anesthetics when used for intravenous regional anesthesia.

Visualization of the course of the sciatic nerve in adult volunteers by ultrasonography

Background: The sciatic nerve block by the posterior approaches represents one of the more difficult ultrasound‐guided nerve blocks. Our clinical experiences with these blocks indicated a point slightly distal to the subgluteal fold as an advantageous position to allow good ultrasonic visibility. In this study, we systematically scanned the sciatic nerve from the subgluteal fold to the popliteal crease, to determine an optimal point for ultrasonographic visualization.

A needle guidance device compared to free hand technique in an ultrasound-guided interventional task using a phantom.

In this in vitro study, a needle guidance device and a ‘free hand’ technique for ultrasound guided needle insertion were compared in a simulated ultrasound‐guided interventional task using a porcine phantom. Residents inexperienced in using ultrasonography were asked to insert a needle, using an in‐plane techniques, and to make contact with metal rods at a depth of 2 and 4 cm in the phantom. The transducer made angles of 90°, 60° and 45° with the surface of the phantom. The times to perform the procedures were significantly shorter and the needle visualisation was significantly better when using the needle guidance device. The residents ranked their satisfaction with the needle‐guidance device significantly better than the ‘free‐hand’ technique. This device may be beneficial when performing ultrasound guided peripheral nerve blocks, especially by inexperienced operators.

Ultrasound-guided training in the performance of brachial plexus block by the posterior approach: an observational study

The application of ultrasonography in guiding and controlling the path of the stimulating needle to the brachial plexus via the posterior approach (Pippa technique) was studied. In 21 ASA physical status 1 and 2 patients, scheduled for surgery of the shoulder or upper arm, needle insertion was monitored by ultrasonography and the interaction between needle, surrounding structures and brachial plexus was followed. During injection, the spread of local anaesthetic was visualised and a prediction of block success was made. One failure was predicted. Complete block was achieved in 20 (95%) patients. One potential complication, puncture of the carotid artery, was prevented using ultrasound. Ultrasound is a useful tool in the training and performance of a neurostimulation‐guided brachial plexus block by the posterior approach. Ultrasonographic guidance may prevent serious complications associated with this approach to the brachial plexus.

Ultrasound-guided bilateral continuous sciatic nerve blocks with stimulating catheters for postoperative pain relief after bilateral lower limb amputations*.

The performance of continuous bilateral sciatic nerve blocks under ultrasonographic control using stimulating catheters is described in a 4‐year‐old child with VACTERL syndrome. Ultrasound showed an abnormal vascular and nerve supply to the lower limbs. The use of ultrasound guidance made successful continuous sciatic nerve blocks possible in a child in whom the traditional method of nerve localisation was unlikely to succeed for anatomical reasons.

Soft tissue landmark for ultrasound identification of the sciatic nerve in the infragluteal region: the tendon of the long head of the biceps femoris muscle

Background and objectives: The sciatic nerve block represents one of the more difficult ultrasound‐guided nerve blocks. Easy and reliable internal ultrasound landmarks would be helpful for localization of the sciatic nerve. Earlier, during ultrasound‐guided posterior approaches to the infragluteal sciatic nerve, the authors recognized a hyperechoic structure at the medial border of the long head of biceps femoris muscle (BFL). The present study was performed to determine whether this is a potential internal landmark to identify the infragluteal sciatic nerve.

Evaluation of thoracic epidural catheter position and migration using radio-opaque catheters

Migration of thoracic epidural radio‐opaque catheters was evaluated in 25 patients scheduled for thoracic surgery in the supine position (n = 5) or in the lateral position with lateral extension of the thoracic spine (n =20). Chest radiography was performed daily for 3 days after operation. Eighty‐nine per cent of catheter tips were visualised in the epidural space. The catheter tip position was unchanged in all patients operated upon in the supine position. In the group operated upon in the lateral position, the catheter tip retracted from day 1 to day 2 by an average of 0.69 cm (SD 1.08; p <0.05); from day 2 to day 3 the average retraction was 0.35 cm (SD 0.67; p <0.05).

Contractures in skeletal muscle of malignant hyperthermia susceptible patients after in vitro exposure to sevoflurane

Background: Sevoflurane, a potent inhalational anaesthetic agent that is structurally similar to halothane, has some favourable characteristics, but may also be able to trigger malignant hyperthermia (MH) in susceptible patients. The diagnosis of malignant hyperthermia susceptibility relies on the in vitro contracture test on skeletal muscle. The present study was undertaken to investigate whether exposure to sevoflurane of muscles of malignant hyperthermia susceptible (MHS) patients would also cause an abnormal contracture.