CCR5 tyrosine sulfation heterogeneity generates cell surface receptor subpopulations with different ligand binding properties

BACKGROUND

Chemokine receptor tyrosine sulfation plays a key role in the binding of chemokines. It has been suggested that receptor sulfation is heterogeneous, but no experimental evidence has been provided so far. The potent anti-HIV chemokine analog 5P12-RANTES has been proposed to owe its inhibitory activity to a capacity to bind a larger pool of cell surface CCR5 receptors than native chemokines such as CCL5, but the molecular details underlying this phenomenon have not been elucidated.

METHODS

We investigated the CCR5 sulfation heterogeneity and the sensitivity of CCR5 ligands to receptor sulfation by performing ELISA assays on synthetic N-terminal sulfopeptides and by performing binding assays on CCR5-expressing cells under conditions that modulate CCR5 sulfation levels.

RESULTS

Two commonly used anti-CCR5 monoclonal antibodies with epitopes in the sulfated N-terminal domain of CCR5 show contrasting binding profiles on CCR5 sulfopeptides, incomplete competition with each other for cell surface CCR5, and opposing sensitivities to cellular treatments that affect CCR5 sulfation levels. 5P12-RANTES is less sensitive than native CCL5 to conditions that affect cellular CCR5 sulfation.

CONCLUSIONS

CCR5 sulfation is heterogeneous and this affects the binding properties of both native chemokines and antibodies. Enhanced capacity to bind to CCR5 is a component of the inhibitory mechanism of 5P12-RANTES.

GENERAL SIGNIFICANCE

We provide the first experimental evidence for sulfation heterogeneity of chemokine receptors and its impact on ligand binding, a phenomenon that is important both for the understanding of chemokine cell biology and for the development of drugs that target chemokine receptors.

Parecoxib, propacetamol, and their combination for analgesia after total hip arthroplasty: a randomized non-inferiority trial

BACKGROUND

This study assessed non-inferiority of parecoxib vs. combination parecoxib+propacetamol and compared the opioid-sparing effects of parecoxib, propacetamol, and parecoxib+propacetamol vs. placebo after total hip arthroplasty.

METHODS

In this randomized, placebo-controlled, parallel-group, non-inferiority study, patients received one of four IV treatments after surgery: parecoxib 40 mg bid (n = 72); propacetamol 2 g qid (n = 71); parecoxib 40 mg bid plus propacetamol 2 g qid (n = 72); or placebo (n = 38) with supplemental IV patient-controlled analgesia (morphine). Patients and investigators were blinded to treatment. Pain intensity at rest and with movement was assessed regularly, together with functional recovery (modified Brief Pain Inventory-Short Form) and opioid-related side effects (Opioid-Related Symptom Distress Scale) questionnaires up to 48 h.

RESULTS

After 24 h, cumulative morphine consumption was reduced by 59.8% (P < 0.001), 38.9% (P < 0.001), and 26.8% (P = 0.005) in the parecoxib+propacetamol, parecoxib, and propacetamol groups, respectively, compared with placebo. Parecoxib did not meet criteria for non-inferiority to parecoxib+propacetamol. Parecoxib+propacetamol and parecoxib significantly reduced least-squares mean pain intensity scores at rest and with movement compared with propacetamol (P < 0.05). One day after surgery, parecoxib+propacetamol significantly reduced opioid-related symptom distress and decreased pain interference with function compared with propacetamol or placebo.

CONCLUSION

Parecoxib and parecoxib+propacetamol provided significant opioid-sparing efficacy compared with placebo; non-inferiority of parecoxib to parecoxib+propacetamol was not demonstrated. Opioid-sparing efficacy was accompanied by significant reductions in pain intensity on movement, improved functional outcome, and less opioid-related symptom distress. Study medications were well tolerated.

Clinically relevant concentrations of lidocaine and ropivacaine inhibit TNFα-induced invasion of lung adenocarcinoma cells in vitro by blocking the activation of Akt and focal adhesion kinase

BACKGROUND

Matrix-metalloproteinases (MMP) and cancer cell invasion are crucial for solid tumour metastasis. Important signalling events triggered by inflammatory cytokines, such as tumour necrosis factor α (TNFα), include Src-kinase-dependent activation of Akt and focal adhesion kinase (FAK) and phosphorylation of caveolin-1. Based on previous studies where we demonstrated amide-type local anaesthetics block TNFα-induced Src activation in malignant cells, we hypothesized that local anaesthetics might also inhibit the activation and/or phosphorylation of Akt, FAK and caveolin-1, thus attenuating MMP release and invasion of malignant cells.

METHODS

NCI-H838 lung adenocarcinoma cells were incubated with ropivacaine or lidocaine (1 nM-100 µM) in absence/presence of TNFα (20 ng ml(-1)) for 20 min or 4 h, respectively. Activation/phosphorylation of Akt, FAK and caveolin-1 were evaluated by Western blot, and MMP-9 secretion was determined by enzyme-linked immunosorbent assay. Tumour cell migration (electrical wound-healing assay) and invasion were also assessed.

RESULTS

Ropivacaine (1 nM-100 μM) and lidocaine (1-100 µM) significantly reduced TNFα-induced activation/phosphorylation of Akt, FAK and caveolin-1 in NCI-H838 cells. MMP-9 secretion triggered by TNFα was significantly attenuated by both lidocaine and ropivacaine (half-maximal inhibitory concentration [IC50]=3.29×10(-6) M for lidocaine; IC50=1.52×10(-10) M for ropivacaine). The TNFα-induced increase in invasion was completely blocked by both lidocaine (10 µM) and ropivacaine (1 µM).

CONCLUSIONS

At clinically relevant concentrations both ropivacaine and lidocaine blocked tumour cell invasion and MMP-9 secretion by attenuating Src-dependent inflammatory signalling events. Although determined entirely in vitro, these findings provide significant insight into the potential mechanism by which local anaesthetics might diminish metastasis.

Funktionsverlust der oberen Extremität nach Bankart-Schulteroperation unter Interscalenus- Blockade und Allgemeinanästhesie

For correction of a shoulder instability (Bankart's operation) in a 33-year-old woman, a combined regional and general anaesthesia was chosen. An interscalene catheter to block the brachial plexus was placed preoperatively without complication. The following day this resulted in an upper extremity almost without motor function and with complete hypoesthesia of the dermatomes C5-C7. Surgical exploration of the plexus was performed 41/2 months later. Stimulation of the three truncs of the brachial plexus was possible and showed electrophysiological signs of recovery of distal parts of the plexus. After 2 years no clinical corresponding recovery could be observed. Despite all investigations (electroneuromyography, evoked potentials, etc.) no clear etiology could be established to explain this adverse outcome.

In vitro exposure of human fibroblasts to local anaesthetics impairs cell growth

Lidocaine, bupivacaine or ropivacaine are used routinely to manage perioperative pain. Sparse data exist evaluating the effects of local anaesthetics (LA) on fibroblasts, which are involved actively in wound healing. Therefore, we investigated the effects of the three LA to assess the survival, viability and proliferation rate of fibroblasts. Human fibroblasts were exposed to 0·3 mg/ml and 0·6 mg/ml of each LA for 2 days, followed by incubation with normal medium for another 1, 4 or 7 days (group 1). Alternatively, cells were incubated permanently with LA for 3, 6 or 9 days (group 2). Live cell count was assessed using trypan blue staining. Viability was measured by the tetrazolium bromide assay. Proliferation tests were performed with the help of the colorimetric bromodeoxyuridine assay. Production of reactive oxygen species (ROS) was determined, measuring the oxidation of non-fluorescent-2,7'-dichlorofluorescin. Treatment of cells with the three LA showed a concentration-dependent decrease of live cells, mitochondrial activity and proliferation rate. Group arrangement played a significant role for cell count and proliferation, while exposure time influenced viability. Among the analysed LA, bupivacaine showed the most severe cytotoxic effects. Increased production of ROS correlated with decreased viability of fibroblasts in lidocaine- and bupivacaine-exposed cells, but not upon stimulation with ropivacaine. This study shows a concentration-dependent cytotoxic effect of lidocaine, bupivacaine and ropivacaine on fibroblasts in vitro, with more pronounced effects after continuous incubation. A possible mechanism of cell impairment could be triggered by production of ROS upon stimulation with lidocaine and bupivacaine.

Sedation and regional anaesthesia in the adult patient

This review discusses sedation for regional anaesthesia in the adult population. The first section deals with general aspects of sedation and shows that the majority of patients receiving sedation for regional anaesthesia are satisfied and would choose it again. Methods of assessing the level of sedation are discussed with emphasis on clinical measures. The pharmacology of the drugs involved in sedation is discussed, with propofol and remifentanil appearing to be the combination of choice for sedation in regional anaesthesia. The techniques for administering sedation are discussed and replacement of the traditional repeated boluses or continuous infusion with pharmacokinetic and patient-controlled systems is supported. Patient satisfaction studies suggest that patient-controlled systems are preferred.

Hypoxia attenuates effector-target cell interaction in the airway and pulmonary vascular compartment

Leucocyte infiltration is known to play an important role in hypoxia-induced tissue damage. However, little information is available about hypoxia and interaction of effector (neutrophils) with target cells (alveolar epithelial cells, AEC; rat pulmonary artery endothelial cells, RPAEC). The goal of this study was to elucidate hypoxia-induced changes of effector-target cell interaction. AEC and RPAEC were exposed to 5% oxygen for 2-6 h. Intercellular adhesion molecule-1 (ICAM-1) expression was determined and cell adherence as well as cytotoxicity assays were performed. Nitric oxide and heat shock protein 70 (HSP70) production was assessed in target cells. Under hypoxic conditions enhanced ICAM-1 production was found in both cell types. This resulted in an increase of adherent neutrophils to AEC and RPAEC. The death rate of hypoxia-exposed target cells decreased significantly in comparison to control cells. Nitric oxide (NO) concentration was enhanced, as was production of HSP70 in AEC. Blocking NO production in target cells resulted in increased cytotoxicity in AEC and RPAEC. This study shows for the first time that target cells are more resistant to effector cells under hypoxia, suggesting hypoxia-induced cell protection. An underlying mechanism for this phenomenon might be the protective effect of increased levels of NO in target cells.

Neurologic and histologic outcome after intraneural injections of lidocaine in canine sciatic nerves

BACKGROUND

Inadvertent intraneural injection of local anesthetics may result in neurologic injury. We hypothesized that an intraneural injection may be associated with higher injection pressures and an increase in the risk of neurologic injury.

METHODS

The study was conducted in accordance with the principles of laboratory animal care, and was approved by the Laboratory Animal Care and Use Committee. Fifteen dogs of mixed breed (16-21 kg) were studied. After general endotracheal anesthesia, the sciatic nerves (n= 30) were exposed bilaterally. Under direct vision, a 25-gauge, long-beveled needle (30 degrees) was placed either epineurally (n= 10) or intraneurally (n= 20), and 4 ml of preservative-free lidocaine 20 mg/ml was injected using an automated infusion pump (4 ml/min). Injection pressure data were acquired using an in-line manometer coupled to a computer via an analog-to-digital conversion board. After injection, the animals were awakened and subjected to serial neurologic examinations. One week later, the dogs were killed, the sciatic nerves excised and histologic examination was performed by pathologists blind to the purpose of the study.

RESULTS

All perineural injections resulted in low pressures (< or = 5 psi). In contrast, eight of 20 intraneural injections resulted in high pressures (20-38 psi) at the beginning of the injection. Twelve intraneural injections, however, resulted in pressures of less than 12 psi. Neurologic function returned to baseline within 3 h after perineural injections and within 24 h after intraneural injections, when the measured injection pressures were less than 12 psi. Neurologic deficits persisted throughout the study period after all eight intraneural injections that resulted in high injection pressures. Histologic examination of the affected nerves revealed fascicular axonolysis and cellular infiltration.

CONCLUSIONS

The data in our canine model of intraneural injection suggest that intraneural injections do not always lead to nerve injury. High injection pressures during intraneural injection may be indicative of intrafascicular injection and may predict the development of neurologic injury.

Inflammation and infection complications of 2285 perineural catheters: a prospective study

BACKGROUND

Perineural catheters (PNCs) are increasingly being used. Few data are available on the infectious complications of PNCs. The incidence and localization of local inflammation and infection associated with PNCs were assessed.

METHODS

PNCs placed under sterile conditions for regional anesthesia and post-operative analgesia were evaluated prospectively. Local inflammation was defined as redness, swelling or pain on pressure at the catheter insertion site. Infection was defined as purulent material at the catheter insertion site with or without the need for surgical intervention.

RESULTS

In total, 2285 PNCs were evaluated: 600 axillary, 303 interscalene, 92 infraclavicular, 65 psoas compartment, 574 femoral, 296 sciatic and 355 popliteal. Local inflammation occurred in 4.2% and infection in 3.2%. The duration of PNC placement was a risk factor (P < 0.05). Surgical intervention was necessary in 0.9%. No late complications occurred in any patient. Interscalene catheters were associated with an increased risk of infection (4.3%; P < 0.05). Anterior proximal sciatic catheters were associated with a lower risk of local inflammation (1.7%; P < 0.05) and infection (0.4%; P < 0.05). Staphylococcus epidermidis and Staphylococcus aureus were isolated in 42% and 58% of catheter tip cultures, respectively.

CONCLUSION

In the present study population, infection of PNCs was a rare occurrence, but the incidence increased with the duration of PNC placement, and close clinical monitoring is required.

Neurologic deficit after peripheral nerve block: what to do?

Regional nerve injury is a recognized complication of plexus anesthesia. Nerve damage after regional anesthesia is the most frightening complication for the patient, the anesthetist and the surgeon too. In order to limit possible medico-legal issues, the anesthetist has to follow an algorithm. The indication and information obtained from the ultrasonography, the sudomotor test, the electromyogram, the elctroneuromyogram and the evoked potentials are discussed. The principles to avoid anesthetic-related nerve damage during regional anesthesia are given. Finally treatment and surveillance, after nerve damage has occurred, are explained.

Continuous spinal anesthesia/analgesia vs. single-shot spinal anesthesia with patient-controlled analgesia for elective hip arthroplasty

BACKGROUND

In total hip replacement surgery several anesthesiological techniques can be used. In this study we compared continuous spinal anesthesia (CSA) and postoperative analgesia vs. single-shot spinal anesthesia (SPA) and postoperative patient-controlled intravenous analgesia with morphine (SPA).

METHODS

In a prospective randomized study, 68 patients, ASA I-III, between 50 and 85 years of age were allocated to these two groups. Quality of analgesia, hemodynamic stability and technical difficulties, as well as incidence of postoperative nausea and vomiting (PONV) and post dural puncture headache (PDPH), were recorded during a 24-h period.

RESULTS

Visual analog scale (VAS) scores were significantly lower in the CSA group from 3 h post operation (P < 0.05). Mean arterial pressure dropped by 21 +/- 11 mmHg in the CSA group and 29 +/- 14 in the SPA group during induction (P < 0.05). Technical difficulties and incidence of PDPH were similar in both groups. Postoperative nausea and vomiting was lower in the CSA group (P < 0.05).

CONCLUSIONS

Continuous spinal anesthesia/analgesia is a very practicable method providing better postoperative analgesia and better hemodynamic stability during anesthesia induction than SPA followed by morphine PCA analgesia after total hip replacement surgery.

[Local anesthetics. Differences and similarities in the "-cains"]

Local anesthetics provoke reversible blockade of nerves by interaction with sodium channels in membranes of nerves. The uncharged molecular configuration of the local anesthetic penetrates the membrane from the outside and the charged configuration then interacts with the sodium channel from the inside. The potency of a local anesthetic is determined mainly by lipid solubility, the time of onset by the pK(a) of the substance and the duration of action by protein binding. Local anesthetic molecules consist of a hydrophilic tertiary amine and a lipophilic aromatic system combined by an ester or amide linkage. Local anesthetics may therefore be classified as aminoester or aminoamide compounds. Aminoesters are hydrolysed by plasmacholinesterase whereas aminoamides undergo metabolisation in the liver. Aminoamides cause fewer allergic reactions. Local anesthetics show dose-dependent CNS and cardiac toxicity. Reports of toxicity, mainly involving bupivacaine and etidocaine initiated the development of ropivacaine which is the first aminoamide marketed as a pure S-enantiomer. Recently introduced was levo-bupivacaine, the S-enantiomer of bupivacaine.

Propofol 1% versus propofol 2% in children undergoing minor ENT surgery

BACKGROUND

The induction characteristics of propofol 1% and 2% were compared in children undergoing ENT surgery, in a prospective, randomized, double-blind study.

METHODS

One hundred and eight children received propofol 1% (n=55) or 2% (n=53) for induction and maintenance of anaesthesia. For induction, propofol 4 mg kg(-1) was injected at a constant rate (1200 ml h(-1)), supplemented with alfentanil. Intubating conditions without the use of a neuromuscular blocking agent were scored.

RESULTS

Pain on injection occurred in 9% and 21% of patients after propofol 1% and 2%, respectively (P=0.09). Loss of consciousness was more rapid with propofol 2% compared with propofol 1% (47 s vs 54 s; P=0.02). Spontaneous movements during induction occurred in 22% and 34% (P=0.18), and intubating conditions were satisfactory in 87% and 96% (P=0.19) of children receiving propofol 1% or 2%, respectively. There were no differences between the two groups in respect of haemodynamic changes or adverse events.

CONCLUSIONS

For the end-points tested, propofol 1% and propofol 2% are similar for induction of anaesthesia in children undergoing minor ENT surgery.

Propofol and midazolam versus propofol alone for sedation following coronary artery bypass grafting: a randomized, placebo-controlled trial

The aim was to compare the efficacy and side-effects of propofol combined with a constant, low dose of midazolam versus propofol alone for sedation. In a prospective, randomized and double-blinded study, 60 male patients scheduled for elective coronary bypass grafting were enrolled. Postoperatively, patients were stratified to receive either a continuous intravenous infusion of midazolam 1 mg/h or placebo. Target Ramsay sedation score was 3 to 5 corresponding to conscious sedation. An intention-to-treat design for propofol was performed to reach target sedation. Efficacy of sedation was statistically significantly higher in the group midazolam + intention-to-treat with propofol compared with the group placebo + intention-to-treat with propofol (91% vs 79%; P=0.0005). Nine of 27 patients in the midazolam group (33.4%) and nine of 26 patients in the placebo group (34.6%) needed no supplementary propofol. Weaning time from mechanical ventilation was longer in the midazolam group whether or not they required supplemental propofol when compared with placebo group (all: 432 +/- 218 min vs 319 +/- 223 min; P=0.04; supplementary propofol: 424 +/- 234 min vs 265 +/- 175 min; P=0.03). The cumulative number of patients remaining intubated was significantly higher in the group midazolam + propofol compared with the group placebo + propofol (P=0.03). In conclusion, target sedation is reached slightly more often by the co-administration of propofol and a low dose of midazolam, but weaning time from mechanical ventilation is prolonged by the co-administration of propofol and a low dose of midazolam.

Acute and nonacute complications associated with interscalene block and shoulder surgery: a prospective study

BACKGROUND

The incidence, etiology, and evolution of complications after interscalene brachial plexus block (ISB) are not well-known. The authors prospectively monitored 521 patients for complications during the first 9 months after ISB.

METHODS

A total of 521 adults scheduled for elective shoulder surgery performed with an ISB were included in this prospective study. The ISB procedure was standardized for all patients Acute complications were recorded. Patients were observed daily (for 10 days) for paresthesias, dysesthesias, pain not related to surgery, and muscular weakness and were evaluated at 1, 3, 6, and 9 months after surgery. Persistence of paresthesias dysesthesias, pain not related to surgery, or muscular weakness was investigated at 1 or 3 months by means of electroneuromyography. Final evaluation was performed at 9 months.

RESULTS

A total of 520 patients completed the study; one was excluded after surgical axillary nerve damage. Two hundred thirty-four patients had an interscalene catheter. Acute complications consisted of one pneumothorax (0.2%) and one episode of central nervous system toxicity (incoherent speech; 0.2%). A 10 days, 74 patients (14%) were symptomatic, and none had muscular weakness. At 1 month, 41 patients (7.9%) had symptoms, and none had muscular weakness. Thirty patients under went electroneuromyography; sulcus ulnaris syndrome (n = 8) carpal tunnel syndrome (n = 2), and complex regional pain syndrome (n = 1) were diagnosed. At 3 months 20 patient (3.9%) were symptomatic, and none had muscular weakness All underwent electroneuromyography; carpal tunnel syndrome (n = 2), complex regional pain syndrome (n = 4), plexus neuropathy (n = 1), and plexus damage (n = 1) were diagnosed. At 6 months, 5 patients (0.9%) were symptomatic. At 9 months 1 patient (0.2%) had persistence of dysesthesia.

CONCLUSIONS

Interscalene brachial plexus block performed with a standardized technical approach, material, and drugs is associated with an incidence of short- and severe long-term complications of 0.4%. In case of persistent paresthesia, dysesthesia, or pain not related to surgery after ISB, sulcus ulnaris syndrome, carpal tunnel syndrome, or complex regional pain syndrome should be excluded since specific treatment may be required.

An evaluation of the infraclavicular block via a modified approach of the Raj technique

Infraclavicular plexus block has recently become a technique of increasing interest. However, no approach has provided easily identifiable landmarks, good conditions for catheter placement, and lack of complications (mainly pneumothorax). We describe a modified approach of the Raj technique based on the identification of the anterior acromial process, jugular notch, and emergence of the axillary artery within the axillary fossa, with the arm abducted to 90 degrees and elevated by approximately 30 degrees. We evaluated the clinical characteristics of this approach by injecting 40 to 50 mL of ropivacaine 0.6% in 150 patients scheduled for elective surgery of the forearm, wrist, or hand. Success was defined as a sensory block of the 5 nerves with territories distal to the elbow within 30 min after performing the block. The success rate was 97% when a distal response (flexion or extension of the wrist or fingers) was elicited and 44% when a proximal (contraction of the triceps, biceps) was obtained using a nerve stimulator. Complications were rare: aspiration of blood was seen in 2% of patients and hematoma was seen at the puncture site in 0.6%; no pneumothorax occurred. Eleven patients (7%) complained of some pain during the procedure. We conclude that the modified approach of the Raj technique for infraclavicular block is very effective when a distal nerve stimulator response is obtained with a small complication rate and a high degree of patient satisfaction.

IMPLICATIONS

We describe a modified approach of the Raj technique for the infraclavicular brachial plexus. The elicitation of a distal nerve stimulator response is associated with a high success rate, a low incidence of complications and a high degree of patient satisfaction.

From cocaine to ropivacaine: the history of local anesthetic drugs

In 1850, about three centuries after the conquest of Peru by Pizzaro, the Austrian von Scherzer brought a sufficient quantum of coca leaves to Europe to permit the isolation of cocaine. As suggested by his friend Sigmund Freud, descriptions of the properties of the coca prompted the Austrian Koller to perform in 1884 the first clinical operation under local anesthesia, by administration of cocaine on the eye. The use of cocaine for local and regional anesthesia rapidly spread throughout Europe and America. The toxic effects of cocaine were soon identified resulting in many deaths among both patients and addicted medical staff. Local anesthesia was in a profound crisis until the development of modern organic chemistry which led to the synthesis of pure cocaine in 1891. New amino ester local anesthetics were synthesized between 1891 and 1930, such as tropocaine, eucaine, holocaine, orthoform, benzocaine, and tetracaine. In addition, amino amide local anesthetics were prepared between 1898 and 1972 including nirvaquine, procaine, chloroprocaine, cinchocaine, lidocaine, mepivacaine, prilocaine, efocaine, bupivacaine, etidocaine, and articaine. All of these drugs were ostensibly less toxic than cocaine, but they had differing amounts of central nervous system (CNS) and cardiovascular (CV) toxicity. Bupivacaine is of special interest because of its long duration of action and history of clinical application. Synthesized in 1957, the introduction of bupivacaine on the market in 1965 paralleled the progressive and cumulative reports of CNS and CV toxicity, leading to the restriction of its use and the identification of a special therapy-resistant CV toxicity. Numerous experimental studies were conducted to identify the fine cellular mechanism of this toxicity, which refines our understanding of the action of local anesthetics. The identification of optically active isomers of the mepivacaine family led to the selection of ropivacaine, a pure S-(-) enantiomer, whose toxicology was selectively and extensively studied before its introduction on the market in 1996. During the rapid and extensive use of ropivacaine in the clinic, unwanted side-effects have been found to be very limited.

Nerve injury associated with regional anesthesia

Neural damage is a possible consequence of general anesthesia, central nervous system blockade, and regional anesthesia. Dainage may be caused by ischaemic and mechanical or chemical factors, which may occur either alone or in combination. Neural damage may be secondary to prolonged and severe arterial hypotension compromising blood supply to the cord, a spinal haematoma whose main etiological factor is a coagulation abnormality, an intraneural injection, and peripheral neuropathy related to perioperative positioning. Mechanical trauma by the needle bevel is an important factor contributing to neuropathy. Neurological complications may also result from a direct neurotoxic effect of local anesthetic agents which is concentration and dose-dependent. A better understanding of these mechanisms will provide a reliable basis for the development of improved pharmaceutical therapy.

The enantiomers: revolution or evolution

The use of single stereoisomers are gaining popularity in the world of anesthesiology. The reduced costs of production have made these compounds available for clinical application. The majority of drugs used in anesthesiology such as ketamine, isoflurane, etomidate, atracurium, bupivacaine and ropivacaine have an asymmetric carbon, and are still used primarily as racemic mixtures (1:1 mixture of R and S enantiomers). Among local anesthetics, the S enantiomers often have favorable biological properties. This insight has led to the development of ropivacaine. Ropivacaine is the first local anesthetic marketed as pure S-(-) enantiomer. Its pharmacodynamic and pharmacokinetic profile is similar to that of bupivacaine, but in vitro and in vivo studies have shown that ropivacaine is less cardiotoxic. Clinical data suggests that ropivacaine has a greater margin of safety than bupivacaine, which is necessary for further expanding the application of regional anesthesia. The time has come for the use of single enantiomers in regional and general anesthesia

Patient-controlled interscalene analgesia with ropivacaine 0.2% versus bupivacaine 0.15% after major open shoulder surgery: the effects on hand motor function

We compared the effects of patient-controlled interscalene analgesia with ropivacaine 0.2% and patient-controlled interscalene analgesia (PCIA) with bupivacaine 0.15% on hand grip strength after major open shoulder surgery. Sixty patients scheduled for elective major shoulder surgery were prospectively randomized to receive in a double-blinded fashion either ropivacaine or bupivacaine through an interscalene catheter. Before surgery, all patients received an interscalene block (ISB) with either 40 mL of 0.6% ropivacaine or 40 mL of 0.5% bupivacaine. Six h after ISB, the patients received a continuous infusion of either 0.2% ropivacaine or 0.15% bupivacaine for 48 h. In both groups, the PCIA infusion rate was 5 mL/h plus a bolus of 4 mL with a lockout time of 20 min. Strength in the hand was assessed preoperatively, 24 h, and 48 h after ISB and 6 h after stopping the infusion of local anesthetic. The presence of paresthesia in the fingers was checked. Pain relief was assessed using a visual analog scale; side effects were noted, and the patients rated their satisfaction 54 h after the block. A significant decrease of strength in the hand was observed in the Bupivacaine group 24, 48, and 54 h after ISB (P < 0.05). Paresthesia was more frequently reported in the Bupivacaine group for the second and third fingers 48 h after ISB (P < 0.05) and in the first three fingers 6 h after discontinuation of the local anesthetic infusion (P: < 0.05). The pain score was similar in the two groups at all times, and patient satisfaction was comparable between the two groups. We conclude that the use of the PCIA technique with ropivacaine 0.2% or bupivacaine 0.15% provides a similar pain relief after major shoulder surgery. However, ropivacaine 0.2% is associated with better preservation of strength in the hand and less paresthesia in the fingers.

IMPLICATIONS

We compared the patient-controlled interscalene analgesia technique with ropivacaine 0.2% and bupivacaine 0.15% after major open shoulder surgery. For similar pain control ropivacaine is associated with better preservation of strength in the hand and less paresthesia in the fingers.

Myopexy (Faden) results in more postoperative vomiting after strabismus surgery in children

BACKGROUND

Strabismus correction in children is associated with a high incidence of postoperative nausea and vomiting. The purpose of this prospective, double-blind study was to examine the influence of the surgical method for correction of squint on the incidence of postoperative vomiting.

METHODS

One hundred and twenty consecutive children aged 2-12 years, scheduled for elective strabismus surgery, were enrolled in this prospective, double-blind study. A standardised total intravenous anaesthesia was given to all children. The development of perioperative oculocardiac reflex was noted and the number of episodes of vomiting during the first 48 h postoperatively was recorded. At the completion of the study, the children who were operated with myopexy according to Faden, were allocated to a Faden group, those without a myopexy to the non-Faden group. All the patients included in this study were operated on by the same surgeon with standardised techniques.

RESULTS

The Faden group was younger, lighter and the operation time was longer (P<0.05). The incidence of vomiting was greater in the Faden group; 53% versus 12% (P<0.05). The incidence of oculocardiac reflex was similar in both groups; 40% in the Faden versus 28% in the non-Faden group, respectively. The total dose of propofol and alfentanil was similar between the groups. Requirement of analgesics for postoperative pain was similar in both groups. The only independent risk factor for postoperative vomiting was the Faden operation.

CONCLUSION

The surgical method used for strabismus correction in children has a great influence on the incidence of postoperative vomiting. The Faden operation is associated with a very high incidence of postoperative vomiting; this particular group of patients has to be considered as a high risk group for postoperative vomiting and deserves an antiemetic prophylaxis.