Single stimulation of the posterior cord is superior to dual nerve stimulation in a coracoid block

BACKGROUND

Both multiple injection and single posterior cord injection techniques are associated with extensive anesthesia of the upper limb after an infraclavicular coracoid block (ICB). The main objective of this study was to directly compare the efficacy of both techniques in terms of the rates of completely anesthetizing cutaneous nerves below the elbow.

METHODS

Seventy patients undergoing surgery at or below the elbow were randomly assigned to receive an ICB after the elicitation of either a single radial nerve-type response (Radial group) or of two different main nerve-type responses of the upper limb, except for the radial nerve (Dual group). Forty milliliters of 1.5% mepivacaine was given in a single or a dual dose, according to group assignment. The sensory block was assessed in each of the cutaneous nerves at 10, 20 and 30 min. Block performance times and the rates of complete anesthesia below the elbow were also noted.

RESULTS

Higher rates of sensory block of the radial nerve were found in the Radial group at 10, 20 and 30 min (P<0.05). The rates of sensory block of the ulnar nerve at 30 min were 97% and 75% in the Radial and in the Dual groups, respectively (P<0.05). The rate of complete anesthesia below the elbow was also higher in the Radial group at 30 min (P<0.05).

CONCLUSIONS

Injection of a local anesthetic after a single stimulation of the radial nerve fibers produced more extensive anesthesia than using a dual stimulation technique under the conditions of our study.

A comparison of single versus multiple injections on the extent of anesthesia with coracoid infraclavicular brachial plexus block

Single-injection coracoid infraclavicular brachial plexus block produces inconsistent anesthesia of the upper limb. In this study, we sought to determine the number of injections needed to provide a reasonably complete anesthesia of the upper limb with this approach. Seventy-five patients were randomly assigned to receive a coracoid block guided by nerve stimulator with 42 mL of 1.5% mepivacaine with a single-injection (Group 1), dual-injection (Group 2), or triple-injection (Group 3) technique. No search for a specific motor response was performed in any group. Sensory and motor block was assessed 5 and 20 min after the end of the injection of local anesthetic. Significantly less complete anesthesia to pinprick in the distributions of the axillary, musculocutaneous, radial, ulnar, and medial cutaneous forearm nerves was found in Group 1 at 20 min. Significantly less complete paralysis for arm, wrist, and hand movements was found in Group 1 at 20 min. No significant difference was found between Groups 2 and 3. We conclude that dual and triple injection of local anesthetic guided by nerve stimulator increases the efficacy of coracoid block when compared with a single-injection technique.

Increased success rate with infraclavicular brachial plexus block using a dual-injection technique

STUDY OBJECTIVE

To test the hypothesis that dual injection of the local anesthetic in coracoid infraclavicular brachial plexus block might enhance both sensory and motor block for anesthesia of the upper limb when compared with a single-injection technique.

DESIGN

Comparative, prospective, randomized, investigator-blinded study.

SETTING

University-affiliated hospital.

PATIENTS

60 patients scheduled for surgery of the hand, forearm, or elbow.

INTERVENTIONS

Patients were randomly assigned to receive either a coracoid infraclavicular block guided by nerve stimulator with a single injection technique (Group 1) or a dual-injection technique (Group 2). Injection of 40 mL 1.5% mepivacaine was made after eliciting one evoked motor response in the upper limb with a nerve stimulator for coracoid infraclavicular block in Group 1 and injection of two separate doses of 20 mL 1.5% mepivacaine after elicitation of two motor responses in Group 2.

MEASUREMENTS

Assessment of sensory and motor block in the upper limb 5 and 20 minutes after the end of the injection of the local anesthetic. The time needed to elicit the second response and to inject the second dose of local anesthetic was also recorded.

MAIN RESULTS

Significantly higher rates of sensory block to pinprick on the distributions of axillary, musculocutaneous, radial, ulnar, and medial cutaneous of the forearm nerves were found in Group 2 at 20 minutes. Significantly higher rates of motor block for arm, wrist, and hand movements were found in Group 2 at 20 minutes.

CONCLUSIONS

Dual injection of local anesthetic guided by nerve stimulator increases the efficacy of coracoid block when compared with a single injection of the same dose of local anesthetic.

[Acute contralateral hemothorax after cannulation of the left subclavian vein for hemodialysis]

Contralateral hemothorax after subclavian vein cannulation is a rare complication of this procedure. We report one case of acute contralateral hemothorax due to perforation of the superior vena cava during left subclavian vein cannulation for hemodialysis. Perforation was attributed to the forced insertion of the skin dilator, which was accidentally pushed too far. Chest pain began immediately after perforation and was followed, a few minutes later, by hemodynamic instability. The signs and symptoms described in this report may serve to warn of the possibility of this complication.

Epidural washout with high volumes of saline to accelerate recovery from epidural anaesthesia

BACKGROUND

Prolonged postoperative blockade can follow neuraxial blocks for short surgical procedures. We investigated whether washout with a high volume of saline through an epidural catheter could provide a faster recovery after epidural anaesthesia.

METHODS

Thirty patients were randomly assigned to a control group (no washout), to group 2x (epidural washout with twice the volume of 2% mepivacaine) and group 4x (epidural washout with four times that volume).

RESULTS

Recovery times from sensory blockade at L2 were 151+/-24, 122+/-29 and 116+/-24 min for control, 2x and 4x groups respectively. Significant differences were found in both saline groups when compared with control group, but not between group 2x and group 4x. No differences were found concerning motor blockade. One patient in group 4x demonstrated signs of intracranial hypertension. Mepivacaine plasma concentrations were increased by saline washout in group 4x.

CONCLUSIONS

Epidural washout with a high volume of saline can not be recommended since no clinically significant reduction in the recovery time can be achieved without risk.

High doses of mepivacaine for brachial plexus block in patients with end-stage chronic renal failure. A pilot study

BACKGROUND AND OBJECTIVE

Patients with end-stage chronic renal failure are at risk of developing several serious postanaesthetic complications. Many anaesthesiologists perform brachial plexus anaesthesia with high doses of local anaesthetic in order to achieve an extensive blockade of the upper limb. Brachial plexus block is a suitable technique for anaesthesia for creation, repair or removal of vascular access for haemodialysis. The aim of this study was to measure mepivacaine plasma concentrations after axillary block with 650 mg plain mepivacaine in patients with end-stage chronic renal failure.

METHODS

Mepivacaine plasma concentrations were assessed throughout a 150-min period, in 10 patients after axillary block with 650 mg plain mepivacaine (600 mg for axillary block and 50 mg for supplementation).

RESULTS

Mepivacaine plasma concentrations expressed in microg mL(-1) as medians and their ranges were: 1.69 (1.23--7.78) at 5 min, 5.61 (4.36--8.19) at 30 min, 8.28 (3.83--11.21) at 60 min, 7.93 (5.63--11.1) at 90 min and 6.49 (5.56--8.35) at 150 min without any symptoms of toxicity.

CONCLUSIONS

Brachial plexus anaesthesia with 650 mg plain mepivacaine did not result in serious systemic toxicity in these patients despite the high mepivacaine plasma concentrations found.

A novel neural network technique for analysis and classification of EM single-particle images

We propose a novel self-organizing neural network for the unsupervised classification of electron microscopy (EM) images of biological macromolecules. The radical novelty of the algorithm lies in its rigorous mathematical formulation that, starting from a large set of possibly very noisy input data, finds a set of "representative" data items, organized onto an ordered output map, such that the probability density of this set of representative items resembles at its possible best the probability density of the input data. In a way, it summarizes large amounts of information into a concise description that rigorously keeps the basic pattern of the input data distribution. In this application to the field of three-dimensional EM of single particles, two different data sets have been used; one comprised 2458 rotational power spectra of individual negative stain images of the G40P helicase of Bacillus subtilis bacteriophage SPP1, and the other contained 2822 cryoelectron images of SV40 large T-antigen. Our experimental results prove that this technique is indeed very successful, providing the user with the capability of exploring complex patterns in a succinct, informative, and objective manner. The above facts, together with the consideration that the integration of this new algorithm with commonly used software packages is immediate, prompt us to propose it as a valuable new tool in the analysis of large collections of noisy data.

pH-controlled quaternary states of hexameric DnaB helicase

DnaB is the major helicase in the Escherichia coli replisome. It is a homohexameric enzyme that interacts with many other replisomal proteins and cofactors. It is usually loaded onto a single strand of DNA at origins of replication from its complex with its loading partner DnaC, then translocates in the 5' to 3' direction, unwinding duplex DNA in an NTP-driven process. Quaternary polymorphism has been described for the DnaB oligomer, a feature it has in common with some other hexameric helicases. In the present work, electron microscopy and in- depth rotational analysis studies of negatively stained specimens has allowed the establishment of conditions that govern the transition between the two different rotational symmetry states (C(3) and C(6)) of DnaB. It is shown: (a) that the pH value of the sample buffer, within the physiological range, dictates the quaternary organisation of the DnaB oligomer; (b) that the pH-induced transition is fully reversible; (c) that the type of adenine nucleotide complexed to DnaB, whether hydrolysable or not, does not affect its quaternary architecture; (d) that the DnaB.DnaC complex exists only as particles with C(3) symmetry; and (e) that DnaC interacts only with DnaB particles that have C(3) symmetry. Structural consequences of this quaternary polymorphism, as well as its functional implications for helicase activity, are discussed.

Mapping and fuzzy classification of macromolecular images using self-organizing neural networks

In this work the effectiveness of the fuzzy kohonen clustering network (FKCN) in the unsupervised classification of electron microscopic images of biological macromolecules is studied. The algorithm combines Kohonen's self-organizing feature maps (SOFM) and Fuzzy c-means (FCM) in order to obtain a powerful clustering technique with the best properties inherited from both. Exploratory data analysis using SOFM is also presented as a step previous to final clustering. Two different data sets obtained from the G40P helicase from B. Subtilis bacteriophage SPP1 have been used for testing the proposed method, one composed of 2458 rotational power spectra of individual images and the other composed by 338 images from the same macromolecule. Results of FKCN are compared with self-organizing feature maps (SOFM) and manual classification. Experimental results prove that this new technique is suitable for working with large, high-dimensional and noisy data sets and, thus, it is proposed to be used as a classification tool in electron microscopy.

Polymorphic quaternary organization of the Bacillus subtilis bacteriophage SPP1 replicative helicase (G40 P)

The Bacillus subtilis bacteriophage SPP1 gene 40 product (G40P), which belongs to the DnaB-like family of helicases, is essential for SPP1 genome replication. The active form of the enzyme is the hexamer, capable of DNA unwinding with a 5' to 3' polarity fueled by the hydrolysis of a nucleoside 5'-triphosphate. We have used electron microscopy of negatively stained G40P samples and image processing techniques to study the structural characteristics of the hexameric assemblies of this protein. Our results provide the first low resolution data on a hexameric helicase of a Gram-positive bacterial origin. A novel approach has been adopted to analyze possible symmetry heterogeneities, an unsupervised method based on a neural network self-organizing algorithm, which has led to the detection of different subclasses of G40P views. Two different quaternary states of G40P homohexamers sharing a C3 symmetry organization have been found, as well as a minor class that seems to reflect an alternative C6 symmetry architecture. These forms show general features known for other hexameric helicases, such as the ring-like arrangement of monomers around a central hole. A clear structural handedness has also been detected in some of these forms. An analysis of these quaternary states and a model for the structural organization of G40P are presented.

Infraclavicular brachial plexus block effects on respiratory function and extent of the block

BACKGROUND AND OBJECTIVES

Axillary block is devoid of severe respiratory complications. However, incomplete anesthesia of the upper limb is the main disadvantage of the technique. Theoretically, the more proximal infraclavicular approach would produce a more extensive block without the risk of pneumothorax. However, neither its effects on respiratory function nor a detailed characterization of the extent of neural block has been assessed. The goal of this study was to evaluate the possible changes in respiratory function and also the extent of the block after infraclavicular block.

METHODS

We performed an infraclavicular block with a mixture of 40 mL 1.5% plain mepivacaine and 4 mL 8.4% sodium bicarbonate in 20 patients. Forced expiratory volumes were measured before and 15 minutes after the injection of local anesthetic, and sensory and motor block were evaluated at 10 and 20 minutes.

RESULTS

We did not find significant differences from baseline in the forced expiratory volumes in any of the patients. Axillary and musculocutaneous nerve distributions had the lowest rate of sensory block at 20 minutes.

CONCLUSIONS

Infraclavicular block does not produce a reduction in respiratory function.

[Post-obstructive pulmonary edema after adenoid-amygdalectomy]

A two-years-old boy with Down's Syndrome and a small interauricular communication was given priority scheduling for adenoidectomy and tonsillectomy to correct subacute obstruction of the upper airway. The only noteworthy event during surgery was an SpO2 of 92% during mechanical ventilation with FiO2 of 0.5 from no apparent cause. The patient suffered acute respiratory insufficiency due to the post-obstructive pulmonary edema in the hours immediately following surgery. The incidence of post-obstructive pulmonary edema is higher than might be expected, as symptoms can be interpreted as aspiration pneumonitis or left ventricular failure. Given the high prevalence of adenoiditis and tonsillitis with varying degrees of airway obstruction in children, we consider it useful to report this case. Such patients should be monitored carefully in the early postoperative period.

[Arm adduction does not increase block extension in anesthesia of the brachial plexus by the axillary approach]

INTRODUCTION

Arm abduction of 90 degrees during injection of local anesthetic followed by adduction of the arm has been recommended traditionally to favor proximal distribution of local anesthetic and extension of the blockade in the brachial plexus by the axillary route. A recent study demonstrated that there are no clinical or radiological differences between axillary blockades performed with abduction or adduction.

OBJECTIVE

To compare the extension of sensory blockade in axillary anesthesia performed with adduction or abduction.

MATERIAL AND METHODS

Forty patients were randomly distributed in two groups, 20 in the adduction group and 20 in the abduction group. The axillary catheter was inserted 3 cm in the proximal direction and a mixture of 40 ml of 1.5% mepivacaine without adrenaline and 4 ml of 8.4% bicarbonate soda was injected into each patient.

RESULTS

No statistically significant differences in extension of sensory blockade, including circumflex, musculocutaneous and radial nerve blockade, were observed.

CONCLUSIONS

Axillary rotation of the arm is not a determining factor in sensory blockade in brachial plexus anesthesia by the axillary route.

The RepA protein of plasmid RSF1010 is a replicative DNA helicase

The RepA protein of the mobilizable broad host range plasmid RSF1010 has a key function in its replication. RepA is one of the smallest known helicases. The protein forms a homohexamer of 29,896-Da subunits. A variety of methods were used to analyze the quaternary structure of RepA. Gel filtration and cross-linking experiments demonstrated the hexameric structure, which was confirmed by electron microscopy and image reconstruction. These results agree with recent data obtained from RepA crystals diffracting at 3.5-A resolution (Röleke, D., Hoier, H., Bartsch, C., Umbach, P., Scherzinger, E., Lurz, R., and Saenger, W. (1997) Acta Crystallogr. Sec. D 53, 213-216). The RepA helicase has 5' --> 3' polarity. As do most true replicative helicases, RepA prefers a tailed substrate with an unpaired 3'-tail mimicking a replication fork. Optimal unwinding activity was achieved at the remarkably low pH of 5.5. In the presence of Mg2+ (Mn2+) ions, the RepA activity is fueled by ATP, dATP, GTP, and dGTP and less efficiently by CTP and dCTP. UTP and dTTP are poor effectors. Nonhydrolyzable ATP analogues, ADP, and pyrophosphate inhibit the helicase activity, whereas inorganic phosphate does not. The presence of Escherichia coli single-stranded DNA-binding protein stimulates unwinding at physiological pH 2-3-fold, whereas the RSF1010 replicon-specific primase, RepB' protein, has no effect, either in the presence or in the absence of single-stranded DNA-binding protein.

Axillary brachial plexus anesthesia: electrical versus cold saline stimulation

The aim of this study was to investigate which of two methods of nerve stimulation, cold saline-induced paresthesia or use of a nerve stimulator, was more effective in increasing the successful brachial plexus block rate by the axillary approach. Twenty patients were randomly assigned to Group A (saline below 11 degrees C), and 20 patients to Group B (nerve stimulator). All blocks were performed by the same anesthesiologist using 40 mL of 1.5% mepivacaine and 4 mL of 8.4% sodium bicarbonate. Successful block was defined using Vester-Andersen et al.'s criteria. Cold saline-induced paresthesiae in the hand or forearm were obtained in 19 patients (95%) during one of four attempts allowed, and in 15 patients (75%) on the first attempt. A motor response was evoked by a nerve stimulator in 17 patients (85%). Two patients (10%) had a paresthesia in the hand without a motor response with the current at less than 1 mA. A successful block was achieved in 19 patients in each group.

EMLA cream for renal extracorporeal shock wave lithotripsy in ambulatory patients

The effectiveness of a Eutectic Mixture of Local Anaesthetics (EMLA cream) for pain control during renal extracorporeal shock wave lithotripsy (ESWL) was evaluated in a group of 20 patients who had not been able to tolerate a previous session without intravenous (i.v.) analgesia. EMLA cream (10 g) was applied on the skin over the area (64-100 cm2) where the shock waves were to be focussed. A second generation lithotriptor Siemens Lithostar was used. The following measurements were made: the shock wave (kV) maximum voltage, the number of successful stone fragmentations (SSF), the visual analogue scale score (0-10) for pain (VAS), and the tolerance scale score (1-4) for the tolerance for the procedure. Significantly higher voltage (17.9 +/- 0.6 kV vs. 16.2 +/- 0.8 kV), lower VAS scores (5.9 +/- 1.1 vs. 8.7 +/- 1.3), lower TS score (2.3 +/- 0.6 vs. 3.6 +/- 0.6) and a higher number of SSF (18 vs. 5) were found in those patients for whom EMLA cream was used. Intravenous analgesia was not needed in nine patients. Nine patients received fentanyl 0.05 mg, one 0.10 mg and another 0.15 mg. These favourable results were attributed both to the sequence of gradual voltage increments used and to the cutaneous analgesia produced by EMLA cream.

DNA photocleavage by novel intercalating 6-(2-pyridinium)phenanthridinium viologens

A new type of DNA-intercalating viologen dications, derived from the N,N'-dialkyl-6-(2-pyridyl)phenanthridine structure (in which dialkyl is -CH2CH2-,-CH2CH2CH2-, or (-CH3)2, abbreviated dq2pyp, dq3pyp, and Me2pyp, respectively), are able to produce frank strand breaks in supercoiled plasmid DNA upon irradiation with visible light. The amount of photocleavage is similar for the three drugs. The observed DNA photosensitization appears to follow a single-strand cleavage model, as shown by a kinetic analysis of the reaction with dq2pyp. The photodynamic action of the drugs seems to be initiated by a light-induced electron transfer reaction from the nucleobases, given the singlet excited-state redox potentials (ca. + 2.1 V vs. SHE) and the low quantum yields of singlet molecular oxygen production of the drugs (0.1-0.2 in aerated D2O).

Stereospecific DNA binding of luminescent atropisomeric viologens

Binding to B-DNA of one enantiomer of dq3pyp, --a member of a novel family of intercalating luminescent viologens derived from N,N'-dialkyl-6-(2-pyridyl)phenanthridine, in which dialkyl is -(CH2)2- (dq2pyp), -(CH2)3- (dq3pyp), or (-CH3)2 (Me2pyp)--, is strongly favored compared to its estable atropisomer. Evidence of the stereospecific interaction has been gained by resolution of a rac-dq3pyp mixture upon dialysis in the presence of DNA, monitored by circular dichroism. Molecular modeling suggests that the S enantiomer of both dq3pyp and dq2pyp is the one preferred for the binding. No similar resolution has been achieved with rac-dq2pyp due to the lower barrier to interconversion of its atropisomers, as shown by 1H-NMR. The identical binding energy of the two modeled diastereoisomeric Me2pyp-DNA complexes discard enantiospecific interaction of this drug. Affinity chromatography on DNA-cellulose allows isolation of the pure enantiomers of dq3pyp.

Cold saline is more effective than room temperature saline in inducing paresthesia during axillary block

Confirmation of the perivascular position of the needle by the injection of cold saline may be helpful to the perivascular technique, since the elicitation of a paresthesia indicates the correct positioning of the needle. In this prospective, randomized study of 48 patients, we found a 100% incidence of successful block with saline at 8-11 degrees C compared to 75% in a control group with saline at room temperature. The paresthesia induced by cold saline appears to be due to thermic stimulation and not to mechanical nerve compression by the saline entering the axillary space. A more frequent rate of correct positioning of the needle was found in the group with cold saline.

Interaction with DNA of photoactive viologens based on the 6-(2- pyridinium)phenanthridinium structure

A new type of DNA-interacting violgens derived from the N,N'-dialkyl 6-(2-pyridinium)-phenanthridinium structure (in which dialkyl is -CH2CH2-,-CH2CH2CH2-, or (-CH3)2) have been synthesized. Electronic spectroscopy, steady-state and time-resolved fluorescence, cyclic voltammetry, binding isotherms, viscosity titrations, and molecular modeling techniques were employed to characterize the structural, photophysical and redox properties of the novel drugs as well as the corresponding drug-DNA complexes. The viologens display significant visible absorption (up to ca. 490 nm), and a rather intense luminescence (phi cm from 0.06 to 0.20 at 491-565 nm wavelength maxima) which is efficiently quenched by DNA. The calculated redox potentials of these drugs in their singlet excited state (+2.1 V vs. SHE) predict a large driving force for a photoelectron transfer reaction from the nucleobases to the drugs. Photochemical measurements of the viologens in the presence of mononucleotides, nucleosides, and deoxyribose indicate that the observed fluorescence quenching occurs indeed by electron transfer from the DNA bases rather than the sugar phosphate backbone. Large association constants to double helical DNA (in the order of 10(5) M-1) have been evaluated from the absorbance-based binding isotherms. Viscosimetry supports intercalation of the drugs into the DNA helix. Computer simulations (molecular mechanics of d(CGCGCG)2-drug complexes) confirm the intercalative nature of the binding and provide finer details about the geometry of the different viologen-DNA complexes. Molecular modeling has also revealed a stereoselective interaction of the enantiomeric drug conformers with the chiral DNA helix. A DNA-targeted drug design of future generations of these ligands in order to improve and/or modulate their photochemical, redox, and nucleic acid binding properties appears to be possible by a careful selection of the N,N'-dialkylating chain and/or the substituents on the azaheterocyclic moieties.

Bradycardia and asystole following atropine-neostigmine administration after caesarean section in a parturient receiving methyldopa for pregnancy-induced hypertension

We report one case of bradycardia and asystole immediately after the administration of 1 mg atropine and 2 mg neostigmine after the completion of an urgent caesarean section. We attribute this adverse reaction to the treatment of pregnancy-induced hypertension with methyldopa, perhaps facilitated by other drugs employed. Similar reactions have been reported relating to beta-receptor antagonists and tricyclic antidepressants, but not to methyldopa.