Peripheral nerve blocks on the upper extremity: Technique of landmark-based and ultrasound-guided approaches

The German Society of Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und Intensivmedizin, DGAI) established an expert panel to develop preliminary recommendations for the application of peripheral nerve blocks on the upper extremity. The present recommendations state in different variations how ultrasound and/or electrical nerve stimulation guided nerve blocks should be performed. The description of each procedure is rather a recommendation than a guideline. The anaesthesiologist should select the variation of block which provides the highest grade of safety according to his individual opportunities. The first section comprises recommendations regarding dosages of local anaesthetics, general indications and contraindications for peripheral nerve blocks and informations about complications. In the following sections most common blocks techniques on the upper extremity are described.

[Perioperative pain management: what is evidence based?]

BACKGROUND

Adequate post-operative acute pain therapy after spinal surgical procedures is essential for many patients. However, patients already receiving chronic opioid therapy pre-operatively present a special challenge for the treating physician during the post-operative period when managing their acute pain. The team must consider multiple approaches of acute pain management and it is important to proceed according to current evidence-based methods.

THERAPY

A wide spectrum of options for pain management after spinal surgery is currently available. This includes various therapeutic methods as well as regional anesthesia. Considering the various options, the method of choice for post-operative analgesia depends on the expected pain, therapy effectiveness, and the applicability with regard to potential side-effects.

METHOD

In addition to the basic analgesic therapy consisting of opioid and non-opioid drugs, chronic pain patients may require co-analgesics or combination analgesics from this class.

CONCLUSION

Regional anesthesia is currently the predominant method of choice for post-operative acute pain management. Neuraxial blockage is especially important when considering all spinal procedures.

Influence of fatigue on EMG/force ratio and cocontraction in cycling

PURPOSE

The purpose of the present study was to observe force and power losses and electromyographic manifestations of fatigue during repeated sprints performed on a friction-loaded cycle ergometer.

METHODS

Ten subjects performed 15 maximal 5-s sprints with 25-s rests between them. Power, velocity, and torque were measured during sprints 1 and 13 and during two submaximal constant-velocity (50 rpm) periods of cycling performed before and after the sprints. The EMG signals of five leg muscles were stored to determine the EMG/force ratio of power producer muscles and the coactivation of antagonist muscles. The power producer muscles were activated to the same level during sprints 1 and 13, despite a loss of force, whereas the vastus lateralis muscle was recruited more during the submaximal cycling period under fatigue conditions.

RESULTS

This led to an increased EMG/force ratio for the power producer muscles, indicating the peripheral fatigue status of these muscles. Antagonist muscles were less activated during the sprints after fatigue; whereas they stayed unchanged during the last submaximal cycling period.

CONCLUSIONS

This suggests that there is a decrease in coactivation as agonist force is lost. This decrease in coactivation under fatigue conditions has not been previously reported and is probably due to the training status of the subjects. Subjects may have learned to better use their antagonist muscles to efficiently transfer force and power to the rotating pedal. This coordination can be adapted to cope with fatigue of the power producer muscles.

Urogenital re-education by electrostimulation: modelling for minimum energy computation

The analysis of the voltage curve V(t) picked up between the two electrodes of a vaginal plug used with a current source stimulation allowed us to suggest a simple electrical model for intravaginal tissue. It is made up of three cells in series: a resistor in parallel with a capacitor for the first two, and a simple resistor for the third. Measurements throughout the hormonal cycle exhibit large variations in resistance and capacitance, and justify the use of a current source device to keep reproducible conditions of stimulation. Subjective detection of sensitivity threshold currents shows results which are independent of the day in the cycle and thus confirms the use of current source stimulation. The curve representing dissipated energy as a function of the pulse duration tau exhibits a minimum value different from the chronaxie (here 800 microseconds). The minimum value is effectively obtained at lower values of tau between 450 and 500 microseconds, dependent on the day of the cycle and the electrical characteristics of vaginal tissue. Two values of tau (230 and 1000 microseconds) between which the energy dissipated is less than Emin + 10 per cent are determined. This gap of pulse duration seems to be a correct range according to the minimum energy criterion for electrostimulation applied to urogenital re-education.

Transoesophageal cross-sectional echocardiography with a phased array transducer system. Technique and initial clinical results

Cardiac imaging by transthoracic two dimensional echocardiography is impaired in patients with chronic lung disease, those with obesity, and those with abnormal chest wall configuration. In order to overcome these limitations, a miniature phased array ultrasound transducer fitted to the tip of a commercially available gastroscope was developed. Transducer position and orientation can be adjusted completely by external control of vertical displacement inside the oesophagus, rotation, and angulation. Introduction and operation of the transducer gastroscope system are usually well tolerated by the patients, since no mechanical vibrations are generated and there is no need for an oil bag to secure oesophageal wall contact. Cardiac images of high quality are obtained even from structures and regions that are poorly or not at all imaged from external transducer positions.