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%.

Ultrasound-guided continuous phrenic nerve block for persistent hiccups.

BACKGROUND: Phrenic nerve block can be performed and repeated if necessary for persistent hiccups, when conservative and pharmacological treatment is unsuccessful. We report the first description of an in-plane ultrasound (US)-guided phrenic nerve block (PhNB) with a catheter, after US investigation of the bilateral diaphragm, to treat hiccups while avoiding repeated PhNBs. CASE: A 36-year-old man had persistent postoperative hiccups not responding to conservative and pharmacological treatment. Bilateral diaphragmatic US evaluation showed abnormal right-sided movement. A right-sided in-plane US-guided PhNB with catheter was performed. Injection of local anesthetic stopped the hiccups, and a continuous infusion of local anesthetic was started for 24 hrs. After discontinuation of the infusion, the hiccups recurred. Restart of the continuous infusion of the local anesthetic through the catheter was performed, and after discontinuation 24 hrs later, no further hiccups occurred. No adverse effect occurred. CONCLUSIONS: An US-guided in-plane PhNB with catheter is feasible and avoids repeated PhNB when hiccups reoccur. Ultrasound investigation of the bilateral diaphragm should be performed before performing the nerve block.

Ultrasound-guided proximal and distal sciatic nerve blocks in children.

STUDY OBJECTIVE: To present the use of ultrasonography for the performance of proximal subgluteal and distal sciatic nerve blocks in children. DESIGN: Prospective descriptive study. SETTING: University hospital. PATIENTS: 45 ASA physical status I, II, and III patients, aged between 8 months and 16 years, scheduled for lower limb surgery. INTERVENTIONS: During general anesthesia, proximal, subgluteal, and distal sciatic nerve blocks using ultrasonography were performed. If severe postoperative pain was expected, a catheter technique was used. MEASUREMENTS: The injected amount of local anesthetic was noted. Based on the spread of local anesthetic, prediction for successful block was made. Complications, adverse effects, postoperative pain scores, and parent satisfaction scores were noted. MAIN RESULTS: 21 proximal sciatic nerve blocks (12 single-injection and 9 continuous blocks) and 35 distal sciatic nerve blocks (17 single-injection, 6 bilateral single-injection, 4 continuous, and one bilateral continuous block) were performed. A mean initial dose of 0.25 mL.kg(-1) of ropivacaine 0.375% was injected. A successful block was obtained in all children. Excellent postoperative pain relief was obtained. All parents were satisfied with the postoperative pain relief. No complications occurred. CONCLUSION: Ultrasonography is useful in the identification of the sciatic nerve and it facilitates needle and catheter placement for proximal and distal nerve blocks in children.

In-plane ultrasound-guided thoracic paravertebral block: a preliminary report of 36 cases with radiologic confirmation of catheter position.

BACKGROUND AND OBJECTIVES: Thoracic paravertebral block (TPVB) can be used for unilateral surgical procedures. Modifications of the classic approach have been proposed to minimize the risk of pleural puncture. In this study, we evaluated the feasibility and success rate of a transverse in-plane ultrasound (US)-guided TPVB with radiologic confirmation of catheter position. METHODS: A total of 36 patients scheduled for unilateral surgery with a TPVB catheter were included in this prospective study. Ultrasonographically, the transverse process of the thoracic vertebra and rib were identified at the appropriate thoracic level. The transducer was moved cranially until an intercostal US view was obtained, indicated by visualization of the parietal pleura. An in-plane needle insertion approach from lateral to medial was used, and a total of 20 mL ropivacaine 0.75% was injected through the needle and a subsequently threaded catheter, while the spread of local anesthetic was observed. Sensory spread of the block was evaluated by loss of cold sensation in the dermatomes. Catheter position was radiologically evaluated with radiopaque dye. RESULTS: Block success rate was 100%. In all patients, correct radiologic thoracic paravertebral catheter position was confirmed; 1 patient also showed additional epidural spread. The median number of total dermatomal segments with loss of cold sensation was 6. No pneumothorax or contralateral loss of cold sensation occurred. CONCLUSION: An in-plane transverse US-guided TPVB using the described technique is feasible and has a high success rate. In all patients, correct catheter position in the thoracic paravertebral space was radiologically confirmed.

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.

Hemidiaphragmatic paresis can be avoided in ultrasound-guided supraclavicular brachial plexus block.

BACKGROUND AND OBJECTIVES: Supraclavicular brachial plexus block is associated with 50% to 67% incidence of hemidiaphragmatic paresis as a result of phrenic nerve block. We examined whether ultrasound-guided compared with nerve stimulation supraclavicular brachial plexus block using 0.75% ropivacaine results in a lower incidence of hemidiaphragmatic paresis. METHODS: In a prospective randomized observer-blinded controlled trial, 60 patients scheduled for elective elbow, forearm, wrist, or hand surgery under supraclavicular brachial plexus block without sedation were included. Supraclavicular brachial plexus block was performed with 20 mL of 0.75% ropivacaine using either ultrasound or nerve stimulation guidance. Ventilatory function was assessed by ultrasound examination of hemidiaphragmatic movement and spirometry. RESULTS: None of the 30 patients in the ultrasound group showed complete or partial paresis of the hemidiaphragm (95% confidence interval, 0.00-0.14), whereas in the nerve stimulation group, 15 patients showed complete paresis of the hemidiaphragm and 1 patient showed partial paresis of the hemidiaphragm (0% versus 53%, respectively; P < 0.0001). Ventilatory function (forced expiratory volume 1, forced vital capacity, peak expiratory flow) was significantly reduced in the nerve stimulation group compared with the ultrasound-guided group (P < 0.05). Two block failures occurred in the nerve stimulation group compared with none in the ultrasound group (P = 0.49). No adverse effects occurred in either group. CONCLUSIONS: Ultrasound-guided supraclavicular brachial plexus block, using 20 mL of 0.75% ropivacaine with the described technique, is not associated with hemidiaphragmatic paresis.

Spinal anesthesia for intrapartum Cesarean delivery following epidural labor analgesia: a retrospective cohort study.

PURPOSE: Failed conversion of epidural labor analgesia (ELA) to epidural surgical anesthesia (ESA) for intrapartum Cesarean delivery (CD) has been observed in clinical practice. However, spinal anesthesia (SA) in parturients experiencing failed conversion of ELA to ESA has been associated with an increased incidence of serious side effects. In this retrospective cohort analysis, we examined our routine clinical practice of removing the in situ epidural, rather than attempting to convert to ESA, prior to administering SA for intrapartum CD. METHODS: Hemodynamic data, frequencies of either high or total spinal block, and maternal and neonatal outcome data were gathered from the anesthesia records of all parturients at the Amphia Hospital, undergoing intrapartum CD between January 1, 2001 and May 1, 2005. RESULTS: Complete data were available for 693 patients (97.6%) of the 710 medical records that were identified. Of the 693 patients, 508 (73.3%) had no ELA and received SA, 128 patients (18.5%) received SA following epidural anesthesia for labor, 19 (2.7%) underwent conversion of ELA to ESA, and 38 (5.5%) received general anesthesia. When comparing both SA groups, no clinically relevant differences were observed regarding the incidence of total spinal block (0% in both groups) or high spinal block (0.2 vs 0.8%, P = 0.36). The number of hypotensive episodes, the total amount of ephedrine administered, and the Apgar scores recorded at 5 and 10 min were similar amongst groups. CONCLUSIONS: The incidence of serious side effects associated with SA for intrapartum CD following ELA is low and not different compared to SA only.

Factors affecting the distribution of neural blockade by local anesthetics in epidural anesthesia and a comparison of lumbar versus thoracic epidural anesthesia.

The spread of sensory blockade after epidural injection of a specific dose of local anesthetic (LA) differs considerably among individuals, and the factors affecting this distribution remain the subject of debate. Based on the results of recent investigations regarding the distribution of epidural neural blockade, specifically for thoracic epidural anesthesia, we noted that the total mass of LA appears to be the most important factor in determining the extent of sensory, sympathetic, and motor neural blockade, whereas the site of epidural needle/catheter placement governs the pattern of distribution of blockade relative to the injection site. Age may be positively correlated with the spread of sensory blockade, and the evidence is somewhat stronger for thoracic than for lumbar epidural anesthesia. Other patient characteristics and technical details, such as patient position, and mode and speed of injection, exert only a small effect on the distribution of sensory blockade, or their effects are equivocal. However, combinations of several patient and technical factors may aid in predicting LA dose requirements. Based on these results, we have also formulated suggested epidural insertion sites that may optimize both analgesia and sympathicolysis for various surgical indications.

Continuous positive airway pressure breathing increases cranial spread of sensory blockade after cervicothoracic epidural injection of lidocaine.

BACKGROUND: Continuous positive airway pressure (CPAP) increases the caudad spread of sensory blockade after low-thoracic epidural injection of lidocaine. We hypothesized that CPAP would increase cephalad spread of blockade after cervicothoracic epidural injection. METHODS: Twenty patients with an epidural catheter at the C6-7 or C7-T1 interspace received an epidural dose of lidocaine while breathing at ambient pressure (control group), or while breathing with 7.5 cm H2O CPAP. After injection, we evaluated the spread of sensory blockade. Spirometry variables before and after epidural injection were also measured. RESULTS: Data are presented as median (interquartile range) values. Sensory block ranged from C7 (C4-7) to T4 (T4-6) in the control group and from C2 (C2-4) to T4 (T2-5) in the CPAP group (P = 0.003 for the cranial border). The total number of segments blocked was 7.5 (6.8-9.8) in the control group and 10 (8-12) in the CPAP group (P = 0.13). The number of segments blocked cranial to the injection site was one (0.8-3.5) in the control group and five (3.5-7) in the CPAP group (P = 0.006). The number of patients with a maximal cranial block (up to C2) was one in the control group and seven in the CPAP group (P = 0.02). In both groups, there was a small but significant decrease from baseline in spirometry values, with no differences between groups. CONCLUSION: Applying CPAP during cervicothoracic epidural injection of lidocaine resulted in a more cranial extension of sensory blockade when compared with breathing at ambient pressure.

A comparison of epidural pressures and incidence of true subatmospheric epidural pressure between the mid-thoracic and low-thoracic epidural space.

BACKGROUND: Differences in epidural pressure (EP) may influence the spread of blockade in thoracic epidural anesthesia. We evaluated if EP and the incidence of subatmospheric EP differ between the mid- and low-thoracic epidural space. METHODS: Patients received an epidural catheter at the T3-5 (MID group, n = 20) or T7-10 (LOW group, n = 20) intervertebral space, respectively. The epidural space was identified using a Tuohy needle connected to a pressure transducer, after which EP was measured. RESULTS: The epidural space could not be identified in three patients who were excluded from the study. EP data are presented as median value (interquartile range). Median EP was 1 mm Hg (-1 to 4.5) in the MID group, and 4 mm Hg (2-7.8) in the LOW group (P = 0.04). The incidence of an EP

A comparison of the lateral and posterior approach for brachial plexus block.

BACKGROUND: Brachial plexus block by the posterior approach described by Pippa is not widely used in contrast to the lateral approach of Winnie. We compared the clinical efficacy of both approaches in a randomized prospective study. METHODS: Eighty patients, American Society of Anesthesiologists physical status I or II, scheduled for surgery of the shoulder or upper arm were randomized in 2 groups: lateral (Winnie, n = 40) or posterior approach (Pippa, n = 40). A single injection of ropivacaine 7.5 mg/mL, 0.5 mL/kg, was made after obtaining a motor response in the distribution of the axillary nerve at a current below 0.5 mA (2 Hz, 0.1 millisecond). Onset and distribution of analgesia and motor block were assessed at 5, 10, 15, 20, 30, and 60 minutes after the local anesthetic injection. Complete block was defined as anesthesia in all dermatomes C3-C6 at 60 minutes after injection. RESULTS: The posterior approach provided complete block in 36 patients (90%) and the lateral approach in 33 patients (83%). Corresponding motor block was similar in both approaches, but the block procedure time was faster in the posterior approach (6.2 [5.2-7.2] minutes v 8.4 [7.1-10.2] minutes; P < .001). Surgical success rate (posterior 95% v lateral 93%) and side effects were similar in both approaches. One complication (thoracic epidural block) was seen using the lateral approach, whereas none occurred in the posterior approach. There was no difference in patient satisfaction scores of the 2 approaches, which were equally high in both groups (posterior 98% v lateral 95%). CONCLUSION: Both approaches are comparable regarding clinical efficacy for anesthesia of the shoulder and upper arm.

Continuous positive airway pressure breathing increases the spread of sensory blockade after low-thoracic epidural injection of lidocaine.

Factors affecting the distribution of sensory blockade after epidural injection of local anesthetics remain incompletely clarified. To evaluate if increasing intrathoracic pressure affects the spread of thoracic epidural anesthesia, we randomized 20 patients who received an epidural catheter at the T7-8 or T8-9 intervertebral space into 2 groups. The control group (n = 10) received an epidural test dose of 4 mL lidocaine 2% during spontaneous breathing at ambient pressure. The continuous positive airway pressure (n = 10) group received the same epidural test dose but during spontaneous respiration with 7.5 cm H2O continuous positive airway pressure. The groups were comparable with respect to demographic variables. Fifteen minutes after the conclusion of the epidural injection, the sensory block ranged from from T4 [median, interquartile range 2.75 segments] to T11 (interquartile range 3.5 segments) in the control group and from T5 (interquartile range 2.25 segments) to L2 (IQR 2.25 segments) in the continuous positive airway pressure group (P = 0.005 for the caudal border). The total number of segments blocked was 7 (median, interquartile range 2.25) in the control group and 11 (interquartile range 3.5) in the continuous positive airway pressure group (P = 0.004). The number of segments blocked caudad to the injection site was 3 (median, interquartile range 3.5) in the control group and 6 (interquartile range 2.25) in the continuous positive airway pressure group (P = 0.005). We conclude that continuous positive airway pressure increases the spread of sensory blockade in thoracic epidural anesthesia, primarily by a more caudad extension of sensory blockade.

Vertical infraclavicular block of the brachial plexus: effects on hemidiaphragmatic movement and ventilatory function.

BACKGROUND AND OBJECTIVES: Several case reports have suggested that block of the brachial plexus by the vertical infraclavicular approach influences hemidiaphragmatic movement and ventilatory function. These effects have not been evaluated in a prospective study. METHODS: Thirty-five consecutive patients scheduled for elective surgery under brachial plexus anesthesia were included. A vertical infraclavicular block was performed with ropivacaine 0.75%, 0.5 mL/kg. Ipsilateral hemidiaphragmatic movement was measured by ultrasonography at maximal forced inspiration and sniff. Forced vital capacity (FVC) and forced expiratory volume (FEV(1)) were measured by a portable vitalograph. All measurements were performed before the block procedure and at 5, 10, 30, and 60 minutes after the block. RESULTS: The block was successful in 34 of 35 patients. In 9 patients (26%), a change in hemidiaphragmatic movement (reduced or paradoxical) was observed. A significant decrease in ventilatory function was found in 8 of these 9 patients between baseline and at 60 minutes: FVC = -0.8 +/- 0.4 L and FEV(1) = -0.7 +/- 0.3 L, mean +/- SD (relative decrease: FVC = 30 +/- 14% and FEV(1) = 32 +/- 13%, mean +/- SD). Horner's syndrome was seen in 4 patients (12%), and in all, a change in hemidiaphragmatic movement was observed. No clinical signs of ventilatory dysfunction were noticed. CONCLUSION: The vertical infraclavicular block can result in a change in ipsilateral hemidiaphragmatic movement, with a decrease of ventilatory function. Although a correlation between the presence of Horner's syndrome and hemidiaphragmatic dysfunction was observed, hemidiaphragmatic dysfunction also occurred independently.

Clinical pharmacology and the use of articaine for local and regional anaesthesia.

Quicker onset and shorter elimination time favours (+/-) articaine as a short-acting local anaesthetic for regional anaesthesia in day-case settings, e.g. arthroscopy (shoulder, knee), hand and foot surgery, and dentistry, because patients treated with articaine will be 'drug free' more quickly than those who receive other local anaesthetics. Articaine diffuses better through soft tissue and bone than other local anaesthetics. The concentration of articaine in the alveolus of a tooth in the upper jaw after extraction was about 100 times higher than that in systemic circulation. Articaine is metabolised via hydrolysis into articainic acid, 75% of which in turn is excreted as such and 25% in the glucuronidated form by the kidneys. The half-lives of elimination (t1/2alpha and t1/2beta) of articaine are 0.6 and 2.5 hours, whereas the apparent half-life of the metabolite articainic acid is 2.5 hours. Intrinsic half-lives of articainic acid are: t1/2alpha 12 minutes, and t1/2beta 64 minutes (1 hour). In dentistry, articaine is the drug of choice in the vast majority of literature. In other regional anaesthesia techniques (intravenous regional anaesthesia, epidural, spinal and plexus blocks) there are not enough data to prove that (+/-) articaine is safer and more effective than the short-acting local anaesthetics lidocaine, (+/-) prilocaine or (+/-) mepivacaine.

Similar motor block effects and disposition kinetics between lidocaine and (+/-)mepivacaine in patients undergoing axillary brachial plexus block during day case surgery.

The aim of this investigation was to compare the clinical effects and pharmacokinetics of lidocaine (one metabolite) and mepivacaine (two metabolites) in 2 groups of 15 patients undergoing axillary brachial plexus anaesthesia. The study had a randomised design. The 30 patients were divided into 2 groups. The patients received either lidocaine (600 mg = 2.561 mMol + 5 mg ml(-1) adrenaline) or mepivacaine (600 mg = 2.436 mMol + 5 microg ml(-1) adrenaline), injected via the axilla near the brachial plexus over a period of 30 s. Onset of surgical analgesia was defined as the period from the end of the local anaesthetic injection to the loss of pinprick sensation in the distribution of the ulnar, radial, and median nerve. Motor block was measured. Onset of motor block was similar for both drugs. Lidocaine is eliminated biexponentially with a t1/2alpha of 9.95 +/- 14.3 min and a t1/2beta of 2.86 +/- 1.55 h. Lidocaine is metabolised into MEGX (tmax 2.31 +/- 0.84 h; Cmax 0.32 +/- 0.13 mg l(-1); t1/2beta 2.36 +/- 2.35 h; total body clearance was 67.9 +/- 28.9 l h(-1)). Mepivacaine is eliminated rapidly and monoexponentially with a t1/2 of 4.78 +/- 2.38 h, a Cmax of 3.89 +/- 0.83 mg l(-1), and a tmax of 0.41 +/- 0.19 h. The total body clearance of mepivacaine is 50% of that of lidocaine, 26.9 +/- 10.6 l h(-1) vs. 67.9 +/- 28.9 l h-1, respectively (p < 0.0001). (+/-)mepivacaine is metabolised into (+/-)4-OHmepivacaine (Cmax 0.45 +/- 0.25 mg l(-1); t1/2beta 6.48 +/- 6.57 h) and (+/-)2,6-pipecoloxylidide (Cmax 0.56 +/- 0.30 mg l(-1); t1/2beta 1.48 +/- 0.74 h). For the axillary brachial plexus block, lidocaine and mepivacaine show similar pharmacodynamic and pharmacokinetic behaviour, despite the number of metabolites, and can therefore be used to the clinical preference for this regional anaesthetic technique.