[Peripheral truncal blocks-Overview and assessment]

By implementation of sonography for regional anesthesia, truncal blocks became more relevant in the daily practice of anesthesia and pain therapy. Due to visualized needle guidance ultrasound supports more safety and helps to avoid complications during needle placement. Additionally, complex punctures are possible that were associated with higher risk using landmarks alone. Next to the blocking of specific nerve structures, interfascial and compartment blocks have also become established, whereby the visualization of individual nerves and plexus structures is not of relevance. The present review article describes published and clinically established puncture techniques with respect to the indications and procedures. The clinical value is reported according to the scientific evidence and the analgesic profile. Moreover, the authors explain potential risks, complications and dosing of local anesthetic agents.

[Stocktaking of local anesthetics 2020]

For decades local anesthetics have proven to be safe and effective drugs in the clinical practice, crucially promoting the enormous achievements in regional anesthesia. Meanwhile, it is a well-known fact that local anesthetics are much more than just "simple" sodium channel blockers. They also interact with numerous other ion channels and subcellular structures, enhancing nerve blockade and resulting in systemic "alternative" effects, which can sometimes even be clinically used. By the simultaneous administration of various adjuvants (e.g., opioids, corticosteroids and α₂-receptor agonists) attempts are made to prolong the time of action of local anesthetics after a single administration in order to achieve the best possible improvement in postoperative analgesia. In this context, ultralong-acting local anesthetics, such as liposomal bupivacaine, which at least theoretically can provide a sensory nerve block for several days, have been developed and clinically introduced. The coming years will show whether these approaches will develop into genuine alternatives to the personnel and cost-intensive continuous nerve blockades.Local anesthetic-induced systemic toxicity is meanwhile rare but still a potentially life-threatening event, frequently resulting from accidental intravascular injection or extensive systemic resorption. Consequently, slow and fractional application of these agents with intermittent aspiration helps to prevent toxic sequelae. If toxic symptoms occur, however, the intravenous infusion of 20% lipid solutions in addition to basic treatment measures can enhance the success of treatment.

Hypothermia does not influence liver damage and function in a porcine polytrauma model

BACKGROUND

Previous studies revealed evidence that induced hypothermia attenuates ischemic organ injuries after severe trauma. In the present study, the effect of hypothermia on liver damage was investigated in a porcine long term model of multi-system injury, consisting of blunt chest trauma, penetrating abdominal trauma, musculoskeletal injury, and hemorrhagic shockMETHODS: In 30 pigs, a standardized polytrauma including blunt chest trauma, penetrating abdominal trauma, musculoskeletal injury, and hemorrhagic shock of 45% of total blood volume was induced. Following trauma, hypothermia of 33∘C was induced for 12 h and intensive care treatment was evaluated for 48 h. As outcome parameters, we assessed liver function and serum transaminase levels as well as a histopathological analysis of tissue samples. A further 10 animals served as controls.

RESULTS

Serum transaminase levels were increased at the end of the observation period following hypothermia without reaching statistical significance compared to normothermic groups. Liver function was preserved (p⩽ 0.05) after the rewarming period in hypothermic animals but showed no difference at the end of the observation period. In H&E staining, cell death was slightly increased hypothermic animals and caspase-3 staining displayed tendency towards more apoptosis in hypothermic group as well.

CONCLUSIONS

Induction of hypothermia could not significantly improve hepatic damage during the first 48 h following major trauma. Further studies focusing on multi-organ failure including a longer observation period are required to illuminate the impact of hypothermia on hepatic function in multiple trauma patients.

Pre-operative fluid bolus for improved haemodynamic stability during minor surgery: A prospectively randomized clinical trial

BACKGROUND

Haemodynamic instability during the induction of anaesthesia and surgery is common and may be related to hypovolaemia caused by pre-operative fasting or chronic diuretic therapy. The aim of our prospective, controlled, randomized study was to test the hypothesis that a predefined fluid bolus given prior to general anaesthesia for minor surgery would increase haemodynamic stability during anaesthetic induction.

METHODS

Two hundred and nineteen fairly healthy adult patients requiring minor surgery were enrolled. All received standard treatment, including a pulse contour analysing device for non-invasive measurement of cardiac index. Infusion therapy was started in all patients at induction. The intervention group (106 patients) was randomized to receive an additional fluid bolus of 8 mL/kg Ringer's acetate solution before the induction of anaesthesia. The primary endpoint was the incidence of haemodynamic instability, defined as a significant reduction of blood pressure or cardiac index during induction of anaesthesia.

RESULTS

The interventional group had a lesser incidence of haemodynamic instability during induction (41.5% vs 56.6%, P = .025). This group also had higher cardiac index, stroke volume index, systolic and mean blood pressure and a greater left ventricular end-diastolic area.

CONCLUSIONS

A fluid bolus prior to anaesthesia reduced the incidence of haemodynamic instability during induction of general anaesthesia. The total fluid volume was slightly greater in the intervention group compared to the control group (1370 ± 439 mL vs 1219 ± 483 mL, P = .007). We conclude that a defined fluid bolus can help stabilizing haemodynamics in patients undergoing general anaesthesia.

Intraneural injection of a test dose of local anesthetic in peripheral nerves - does it induce histological changes in nerve tissue?

BACKGROUND & OBJECTIVES

Most anesthesiologists use the injection of a test dose of local anesthetic in order to evaluate the final needle tip position. Thus, the intraneural injection of a full dose can be avoided. The aim of this study was to analyze whether an intraneural injection of a test dose of bupivacaine could trigger histological changes.

METHODS

Intraneural injections under direct vision were performed in 40 brachial plexus nerves in seven anesthetized pigs. Tibial nerves served as positive and negative controls. Two milliliter of bupivacaine 0.5% was injected in three nerves on the left brachial plexus. For control of local anesthetic's toxicity Ringer's solution was applied intraneurally on the right side. After maintaining 48 h of general anesthesia, the nerves were resected. The specimens were processed for histological examination and assessed for inflammation (hematoxylin and eosin stain, CD68-immunohistochemistry) and myelin damage (Kluver-Barrera stain). The degree of nerve injury was rated on a scale from 0 (no injury) to 4 (severe injury).

RESULTS

Statistical analysis showed no significant differences between the bupivacaine group [median (interquartile range) 1 (1-1.5)] and the Ringer's solution group [1 (0.5-2) P = 0.772]. Mild myelin alteration was found in 12.5% of all specimens following intraneural injection, irrespective of the applied substance.

CONCLUSIONS

"In our experimental study, intraneural injection of 2 ml of bupivacaine or Ringer's solution showed comparable mild inflammation. Nevertheless, inflammation can only be prevented by strictly avoiding nerve perforation followed by intraneural injection, as mechanical nerve perforation is a key factor for evolving inflammation.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

Phrenic palsy and analgesic quality of continuous supraclavicular vs. interscalene plexus blocks after shoulder surgery

BACKGROUND

Hemidiaphragmatic palsy is a common consequence of the interscalene brachial plexus block. It occurs less commonly with the supraclavicular approach. Register data suggest that the analgesic quality of a supraclavicular blockade is sufficient for arthroscopic shoulder surgery, although data on the post-operative analgesic effect are lacking.

METHODS

After approval by the ethics committee, patients having arthroscopic shoulder surgery under general anaesthesia were randomized to receive a continuous interscalene or supraclavicular blockade. Phrenic nerve function was evaluated through ultrasound examination of the diaphragm in combination with spirometry. Pain scores at rest and activity etc. were determined before catheter insertion, during observation in the post- anaesthesia care unit (PACU) and on post-operative day 1 (POD1). The initial application of 10 ml of ropivacaine 0.2% was followed by continuous application of 4 ml of ropivacaine 0.2%, plus a patient controlled analgesia (PCA) bolus of 4 ml/h.

RESULTS

One hundred and twenty patients were randomized, of which 114 data sets were analysed. Complete hemidiaphragmatic paresis occurred in 43% of the interscalene group vs. 24% in the supraclavicular group during PACU stay. Rates of dyspnoea and hoarseness were similar. Horner's syndrome occurred in 21% of the interscalene but only 3% of the supraclavicular group on POD1. Pain scores were comparable for pain at rest and during stress at each time point.

CONCLUSIONS

This trial showed a significantly greater incidence of phrenic nerve palsy of the interscalene group in PACU, but not on POD1. Post-operative analgesic quality was similar in both groups. Continuous supraclavicular blockade is a suitable alternative to the continuous interscalene technique.

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.

Tunnelling of thoracic epidural catheters is associated with fewer catheter-related infections: a retrospective registry analysis

BACKGROUND

Catheter-related infections are a serious complication of continuous thoracic epidural analgesia. Tunnelling catheters subcutaneously may reduce infection risk. We thus tested the hypothesis that tunnelling of thoracic epidural catheters is associated with a lower risk of catheter-related infections.

METHODS

Twenty-two thousand, four hundred and eleven surgical patients with continuous thoracic epidural analgesia included in the German Network for Regional Anaesthesia registry between 2007 and 2014 were grouped by whether their catheters were tunnelled (n=12 870) or not (n=9541). Catheter-related infections in each group were compared with Student's unpaired t and χ(2) tests. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated with logistic regression, adjusting for potential confounding factors, including age, ASA physical status score, use of catheter for ≥4 days, multiple skin puncture, hospital, and surgical department.

RESULTS

There were fewer catheter-related infections in patients with tunnelled catheters (4.5 vs 5.5%, P<0.001). Mild infections were also less common (4.0 vs 4.6%, P=0.009), as were moderate infections (0.4 vs 0.8%, P<0.001). After adjustment for potential confounding factors, tunnelling remained an independent prevention for any grade of infection (adjusted OR 0.51, 95% CI 0.42-0.61, P<0.001) and for mild infections (adjusted OR 0.54, 95% CI 0.43-0.66, P<0.001) and moderate and severe infections (adjusted OR 0.44, 95% CI 0.28-0.70, P=0.001).

CONCLUSION

Tunnelling was associated with a lower risk of thoracic epidural catheter-related infections.

[Bipolar Sealing of Lung Veins with 5 mm and 10 mm Instruments - Bursting Pressures Measured in an Ex-Vivo Model]

BACKGROUND

In every anatomic lung resection, lung veins need to be sealed and divided. If open surgery is performed, veins are usually treated with ligatures. In minimally-invasive procedures a vascular stapler is used. Blood vessels can be securely closed with modern bipolar sealing technology. Since this method has rarely been used in lung veins, we carried out the present study on an ex-vivo model to test whether satisfactory bursting pressures can be achieved using 5 mm and 10 mm MARSEAL® sealing instruments.

MATERIAL AND METHODS

The experimental investigations were carried out on heart-lung preparations (including both lungs) from freshly-slaughtered pigs (weight: 199 lbs). After the lung veins were dissected, three groups were formed according to size: group 1: 1-7 mm, group 2: 8-10 mm and group 3: > 10 mm. Bipolar sealing was performed with a 5 mm or 10 mm MARSEAL® sealing device and the special SealSafe® G5 electric current. Vessels closed by simple ligation served as a control group. A pressure sensor was implanted into the unsealed end of the blood vessel. Air was pumped into the blood vessel and the bursting pressure - the pressure (in mbar) at which the vessel began to leak - was determined digitally. The mean bursting pressures were compared using the non-parametric Mann Whitney U test (the level of significance was p < 0.05).

RESULTS

In group 1 the mean bursting pressures for the 5 mm and 10 mm instruments were found to be 167.1 ± 38.7 mbar and 113.8 ± 23.3 mbar, respectively. Both were significantly inferior to the pressure of 178.8 ± 44.5 mbar achieved by the control group. In group 2 the bursting pressures were 122.7 ± 27.8 mbar with the 5 mm instrument and 93.5 ± 39.6 mbar with the 10 mm instrument. The mean bursting pressure for the control group was 180.7 ± 35.8.mbar. In group 3 the mean bursting pressures were 98.2 ± 28.8 mbar with the 5 mm instrument and 65.5 ± 19.7 mbar with the 10 mm instrument. All attempts to seal the entire left atrium failed.

CONCLUSION

In our ex-vivo model of lung veins, acceptable bursting pressures were achieved in blood vessels with a maximum diameter of 10 mm. Bipolar impedance-controlled sealing may create an adequate seal on pulmonary veins up to a diameter of 10 mm. The use of a 10 mm instrument has no advantage compared to a 5 mm instrument. Secure sealing of the left atrium is not possible.

[Glucocorticoids as an adjunct in peripheral regional anesthesia. Move to the "Holy Grail of perineural analgesia"?!]

BACKGROUND

The role of dexamethasone as an adjunct in peripheral nerve blockades is still unclear.

OBJECTIVES

This article reviews the actual knowledge and scientific evidence for dexamethasone as an adjunct in peripheral regional anesthesia. Moreover, it discusses the benefits of the systemic versus the perineural mode of application.

RESULTS

Dexamethasone prolongs sensible as well as motor blockades in peripheral nerve blocks when applied intravenously or perineurally. Regarding potentially local neurotoxicity, published patient data are not sufficient for final conclusions.

CONCLUSIONS

After reviewing the actual literature, the authors prefer a systemic application mode (intravenously) over a perineural route of administration of dexamethasone as an adjunct for peripheral nerve blocks. This is due to the better understanding of potential side effects of the drug when applied intravenously. Dexamethasone might be a useful drug adjunct to prolong peripheral single shot nerve blocks.

Risk evaluation for needle-nerve contact related to electrical nerve stimulation in a porcine model

BACKGROUND

For performing peripheral nerve blocks, the risk for needle-nerve contact (NNC) as an adverse event for low and high current thresholds has not yet been clearly defined when nerve stimulator guided techniques were applied. This experimental study aimed to investigate the risk of NNCs when applying stimulation currents between 0.1 and 2 mA (in increments of 0.1 mA).

METHODS

Brachial plexus nerves were exposed surgically in five anesthetized pigs. An insulated needle connected to a nerve stimulator was placed at 10 mm distance to the targeted nerves. Current intensity was adjusted according to randomization (0.1-2.0 mA, increments of 0.1 mA). The needle tip was advanced toward the nerve until a motor response was elicited. The frequencies of NNCs for each of the adjusted current intensities were noted. Risks of NNCs were calculated according to the analysis of 95% confidence intervals (95% CI).

RESULTS

We executed 2000 needle placements with stimulation currents ranging from 0.1 to 2.0 mA. The risks for NNC at low current intensities were 0.85 (95% CI, 0.77-0.91) for 0.3 mA and 0.5 (95% CI, 0.4-0.6) for 0.5 mA, respectively. For high current intensities, risks of 0.13 (95% CI, 0.07-0.21) for 0.9 mA and 0.01 (95% CI, 0-0.05) for 1.1 mA were calculated.

CONCLUSIONS

In this experimental animal study, a relevant reduction in the risk of NNCs could be observed when high current intensities (0.9-1.1 mA) were applied compared to low current intensities (0.3-0.5 mA).

A porcine polytrauma model with two different degrees of hemorrhagic shock: outcome related to trauma within the first 48 h

BACKGROUND

An animal polytrauma model was developed, including trunk and extremity injuries combined with hemorrhagic shock and a prolonged post-traumatic phase. This could be useful for the assessment of different therapeutic approaches during intensive care therapy.

METHODS

A standardized polytrauma including lung contusion, liver laceration and lower leg fracture was applied in 25 pigs. They underwent controlled haemorrhage either with a blood volume loss of 45 % and a median arterial pressure (MAP) <30 mmHg/90 min (group L, n = 15) or a 50 % blood loss of and an MAP <25 mmHg/120 min (group H, n = 10). Five non-traumatized pigs served as a control (group C). Subsequently, intensive care treatment was given for an observational period of 48 h.

RESULTS

Both trauma groups showed signs of shock and organ injury (heart rate, MAP and lactate). The frequency of cardiopulmonary resuscitation (CPR) and lung injury was directly related to the severity of the haemorrhagic shock (CPR-group L: 4 of 15 pigs, group H: 4 of 10 pigs; Respiratory failure-group L: 3 of 13, group H: 3 of 9. There was no difference in mortality between trauma groups.

CONCLUSION

The present data suggest that our model reflects the mortality and organ failure of polytrauma in humans during shock and the intensive care period. This suggests that the experimental protocol could be useful for the assessment of therapeutic approaches during the post-traumatic period.

Obesity in regional anesthesia--a risk factor for peripheral catheter-related infections

BACKGROUND

Obesity is believed to increase the risk of surgical site infections and possibly increase the risk of catheter-related infections in regional anesthesia. We, therefore, analyzed the influence of obesity on catheter-related infections defined within a national registry for regional anesthesia.

METHODS

The German Network for Regional Anesthesia database with 25 participating clinical centers was analyzed between 2007 and 2012. Exactly, 28,249 cases (13,239 peripheral nerve and 15,010 neuraxial blocks) of patients ≥ 14 years were grouped in I: underweight (BMI 13.2-18.49 kg/m(2) , n = 597), II: normal weight (BMI 18.5-24.9 kg/m(2) , n = 9272), III: overweight (BMI 25.0-29.9 kg/m(2) , n = 10,632), and IV: obese (BMI 30.0-70.3 kg/m(2) , n = 7,744). The analysis focused on peripheral and neuraxial catheter-related infections. Differences between the groups were tested with non-parametric ANOVA and chi-square (P < 0.05). Binary logistic regression was used to compare obese, overweight, or underweight patients with normal weight patients. Odds ratios (OR and 95% confidence interval) were calculated and adjusted for potential confounders.

RESULTS

Confounders with significant influence on the risk for catheter-related infections were gender, age, ASA score, diabetes, preoperative infection, multiple skin puncture, and prolonged catheter use. The incidence (normal weight: 2.1%, obese: 3.6%; P < 0.001) and the risk of peripheral catheter-related infection was increased in obese compared to normal weight patients [adjusted OR: 1.69 (1.25-2.28); P < 0.001]. In neuraxial sites, the incidence of catheter-related infections differed significantly between normal weight and obese patients (normal weight: 3.2%, obese: 2.3%; P = 0.01), whereas the risk was comparable [adjusted OR: 0.95 (0.71-1.28); P = 0.92].

CONCLUSION

This retrospective cohort study suggests that obesity is an independent risk factor for peripheral, but not neuraxial, catheter-related infections.

Focused intraoperative transthoracic echocardiography by anesthesiologists: a feasibility study

BACKGROUND

Focused transthoracic echocardiography (TTE) is frequently used perioperatively for hemodynamic monitoring and diagnosis of cardiovascular instability, but less commonly intraoperatively.

METHODS

To evaluate the feasibility of intraoperative TTE, we enrolled 222 anesthetised patients from August to November 2012 into a prospective observational study. 162 patients underwent TTE examination according to the Focused Assessed Transthoracic Echocardiography (FATE) protocol after positioning and draping for surgery. Sixty additional hemodynamically unstable subjects were examined during anesthesia and surgery. The imaging quality of four FATE views was rated on a scale from 1 (impossible) to 5 (perfect). TTE was assessed as applicable, if at least two of the four basic FATE views were graded 4 or 5, or three views were assessed as grade 3.

RESULTS

Imaging quality was unacceptable in 20 patients, resulting in a feasibility rate of 91% (97.5%-CI 0.86-1, P=0.01). TTE was feasible in hemodynamically unstable subjects (91.7%; 97.5%-CI 0.82-1.0), in orthopedic and trauma patients (>95% respectively, [97.5%-CI 0.83-1]) and in abdominal surgery (78%).

CONCLUSION

TTE can be applied in the operating theatre during surgery, although its use during abdominal surgery is somewhat limited.

Impact of haemorrhagic shock intensity on the dynamic of alarmins release in porcine poly-trauma animal model

PURPOSE

Traumatic insults result in an altered inflammatory response, in which alarmins release has a central role. The impact of haemorrhagic shock intensity on the long-term kinetics of alarmins is not yet fully elucidated. We investigated these aspects in a combined trauma (chest, abdominal, and extremities injury) porcine model with different severities and durations of haemorrhagic shock.

METHODS

After induction of combined trauma (tibia fracture, lung contusion, and liver laceration), haemorrhagic shock was induced at different intensities: moderate haemorrhage (MH; n = 15): mean arterial pressure (MAP) <30 ± 5 mmHg [maximum loss of total blood volume (TBVmax): 45 %] for 90 min, and severe haemorrhage (SH; n = 10): MAP <25 ± 5 mmHg (TBVmax 50 %) for 120 min. Resuscitation was performed using a standardized crystalloid infusion protocol. Animals were mechanically ventilated and underwent ICU-monitoring for 48 h (MH) and 48.5 h (SH). Blood samples were collected over the clinical time course, and systemic levels of serum alarmins [High-Mobility Group Protein B-1 (HMGB-1) and Heat Shock Protein 70 (HSP70)] were measured using an ELISA kit.

RESULTS

Heart rate, systemic blood pressure, lactate, and base excess were significantly altered as a function of haemorrhagic shock in both trauma groups (MH and SH). Systemic HMGB-1 levels were significantly elevated in both trauma groups when compared to the sham group. Haemorrhagic shock severity and duration were positively correlated with HMGB-1 levels and compared to baseline values, concentrations remained significantly increased in SH when compared to MH. On the other hand, we observed a significant decrease in the systemic HSP70 levels of trauma groups (MH, and SH) when compared to the sham group, which was significantly decreased compared to baseline values in SH over the entire time course.

CONCLUSION

Our data show that haemorrhagic shock duration and severity affect the systemic levels of HMGB-1 and HSP70. This early alarmins release after trauma can be used to guide the treatment strategies (e.g. surgical procedures) of polytrauma patients.

[Seeing more : Technical innovations in regional anesthesia]

Visualization and verification are key factors since the implementation of ultrasound-guided regional anesthesia. This article reviews and discusses newer technical innovations in regional anesthesia with regard to optimization of needle guidance, improvements in needle visibility, technical improvements in ultrasound techniques and innovative technologies in regional anesthesia. Clinically available applications are presented as well as experimental tools and techniques with a potential for clinical implementation in the future. Mechanical needle guides are used to improve alignment of needle axis and ultrasound beam axis. Compound imaging technology improves needle visibility in steep needle insertion angles and is already implemented in daily clinical practice. Sonoelastography improves tissue discrimination and detection of small amounts of fluids. Benefits of 3D and 4D ultrasound in regional anesthesia are discussed as well as experimental tools for tissue discrimination, such as optical reflection spectrophotometry.

[Localization of peripheral nerves. Success and safety with electrical nerve stimulation]

Peripheral electrical nerve stimulation is one of the standard applications in peripheral regional anesthesia in addition to the ultrasound technique. Among other findings, the visualization of needle and nerve during ultrasound-guided blockade caused a change in clinical practice of peripheral nerve stimulation in the last decade. In the present article old and new aspects of principles and clinical practice of the nerve stimulation technique are presented and summarized in a total clinical concept in order to achieve safe and successful peripheral regional anesthesia using electrical peripheral nerve stimulation.

Supplemental single shot femoral nerve block for total hip arthroplasty: impact on early postoperative care, pain management and lung function

BACKGROUND AND AIM

Peripheral regional anesthesia is beneficial in the management of postoperative pain in hip surgery, and can also reduce post-operative care unit (PACU) stay. Its opioid-sparing actions may also be beneficial for respiratory mechanics and pulmonary function. The aim of our pilot study was to evaluate the effect of a supplemental single shot femoral block for elective total hip arthroplasty on early respiratory function and postoperative management within the first 24 postoperative hours.

METHODS

We prospectively studied 80 patients undergoing total hip arthroplasty. Written informed consent was obtained after ethics committee approval. Forty patients were randomLy assigned to receive single shot femoral nerve block (FNB) using 15mL bupivacaine 0.25% and 20 mg clonidine while the remainder received standard treatment without nerve block (STN). Premedication and general anesthesia were standardized. Pulse oximetry saturation and spirometric lung function were measured preoperatively (baseline) and at 0.5 h, 2 h, 6 h and 24 h, after extubation breathing room air. PACU surveillance and postoperative pain therapy was standardized.

RESULTS

Oxygen saturation and spirometry results were significantly better within the FNB group during the first six postoperative hours. Although VAS scores during the PACU stay did not significantly differ between the study groups, PACU discharge criteria were met earlier in the FNB group (116±40 min [mean±SD] vs. 152±47 min in the STN group). The FNB group exhibited significantly lower VAS scores at 6 and 24 hours.

CONCLUSION

Supplemental single shot femoral nerve block for total hip arthroplasty resulted in earlier PACU discharge capability, improved lung function during the first six hours and better pain control within the first 24 postoperative hours.

Nerve perforation with pencil point or short bevelled needles: histological outcome

BACKGROUND

In the case of needle nerve contact during peripheral blocks, pencil point needles are considered less traumatic compared with bevelled needles. However, there are not enough data to prove this notion. Therefore, the aim of this study was to challenge the hypothesis that nerve perforation with short bevelled needles is associated with major nerve damage compared with pencil point needles.

METHODS

In five anaesthetised pigs, the brachial plexus was exposed bilaterally. Up to eight nerves underwent needle nerve perforation using a pencil point needles cannula or an short bevelled needle. After 48 h, the nerves were resected. The specimens were processed for visual examination and the detection of inflammatory cells (haematoxylin-eosin, i.e. CD68-immunohistochemistry to detect macrophages), myelin damage (Kluver-Barrera staining) and intraneural haematoma. The grade of nerve injury was characterised by an objective score ranging from 0 (no injury) to 4 (severe injury).

RESULTS

Fifty nerves were examined. According to the injury score applied, there was no significant difference between the pencil point needles [median (inter-quartile range) 2.0 (2.0-2.0)] and the short bevelled-needle group [median 2.0 (2.0-2.0) P=0.23]. No myelin damage was observed. Signs of post-traumatic inflammation were equally distributed among both groups.

CONCLUSIONS

In the present study, the magnitude of nerve injury after needle nerve perforation was not related to one of the applied needle types. Post-traumatic inflammation rather than structural damage of nerve tissue is the only notable sign of nerve injury after needle nerve perforation with either needle type. However, neither the pencil point- nor the short bevelled needle can be designated a less traumatic device.

Systematic evaluation of the highest current threshold for regional anaesthesia in a porcine model

BACKGROUND

The purpose of this study was to determine systematically the highest minimal stimulation current threshold for regional anaesthesia in pigs.

METHODS

In an established pig model for regional anaesthesia, needle placements applying electric nerve stimulation were performed. The primary outcome was the frequency of close needle to nerve placements as assessed by resin injects and subsequent anatomical evaluation. Following a statistical model (continual reassessment method), the applied output currents were selected to limit the necessary number of punctures, while providing guidance towards the highest output current range.

RESULTS

Altogether 186 punctures were performed in 11 pigs. Within the range of 0.3-1.4 mA, no distant needle to nerve placement was found. In the range of 1.5-4.1 mA, 43 distant needle to nerve placements occurred. The range of 1.2-1.4 mA was the highest interval that resulted in a close needle to nerve placement rate of > or =95%.

CONCLUSIONS

In the range of 0.3-1.4 mA, all resin deposition was found to be adjacent to nerve epineurium. The application of minimal current intensities up to 1.4 mA does not obviously lead to a reduction of epineural injectate contacts in pigs. These findings suggest that stimulation current thresholds up to 1.4 mA result in equivalent needle tip localisation in pigs.

Femoral nerve block with ropivacaine or bupivacaine in day case anterior crucial ligament reconstruction

BACKGROUND/OBJECTIVE

Our aim was to evaluate analgesia, motor block and pharmacokinetics of ropivacaine 0.2% and 0.75% in a femoral nerve block (FNB) in day case patients for anterior crucial ligament (ACL)-reconstruction compared with bupivacaine 0.25% and placebo.

METHODS

Following ethics committee approval and informed consent, 280 patients were randomly allocated to four groups for single-shot FNB [30 ml ropivacaine 0.2% (group RO2.0), 0.75% (RO7.5), bupivacaine 0.25% (BU2.5) and NaCl 0.9% (NaCl)]. Analgesia (pain scores, primary outcome) and motor block were assessed at 4 h (dismissal) and up to 24 h. Plasma concentration was determined up to 240 min thereafter.

RESULTS

Pain scores at 4 h were significantly higher for NaCl 4 (0-8) (median, range) (vs.) BU2.5 2 (0-8), RO2.0 3 (0-9) and RO7.5 2 (0-8) (NS within the LA groups). Patients of the NaCl group needed analgesics significantly more often (93%) within 4 h after surgery vs. 16% of group RO2.0, 19% of group RO7.5 and 19% of group BU2.5. Motor block was significantly increased with all local anesthetics without a significant difference within the LA groups 3 (0-5) in RO2.0, 3 (0-5) in RO7.5 and 3 (0-4) in BU2.5 vs. 0 (0-3) in group NaCl (median (range); scale from 0=full strength to 5=complete paralysis). Peak plasma concentrations differed significantly: RO7.5: 1.4 +/- 0.4 (0.73-2.6) [microg/ml, mean +/- SD (range)] after 33 +/- 14 (10-40) min, RO2.0: 0.6 +/- 0.3 (0.13-1.0) after 22+17 (10-60) and BU2.5: 0.3 +/- 0.16 (0.05-0.62) at 31 +/- 17 (10-60), respectively.

CONCLUSION

FNB for ACL reconstruction with ropivacaine or bupivacaine provided better post-operative analgesia than placebo without reaching toxic plasma concentrations. Significant motor block was observed after 4 h in all groups including the lowest concentration of ropivacaine but occurred even with placebo.

High or low current threshold for nerve stimulation for regional anaesthesia

BACKGROUND

The purpose of this study was to determine whether the application of high stimulation current thresholds (SCT) leads to a distant needle to nerve proximity (NNP) compared with low SCT during nerve localization for regional anaesthesia in pigs.

METHODS

A minimal motor response to the stimulation of femoral or brachial plexus nerves in 16 anaesthetized pigs was triggered either by a minimal SCT of a low (0.01-0.3 mA) or a high (0.8-1.0 mA) current in a random order. After eliciting a motor response with a predetermined SCT, synthetic resin was injected via the needle. After postmortem dissection of the injection site, the localization of the resin deposition was determined verifying the final position of the needle tip. Depending on the proximity of resin deposition to the nerve epineurium, the needle tip placement was considered either as a close or a distant NNP.

RESULTS

A total of 235 punctures were performed. Ninety-one punctures were carried out with low SCT and 92 with a high SCT. Fifty-two punctures served as a control (1.8-2.0 mA). All injectates following both high or low SCT were considered 'close needle tip to nerve placement', whereas 27 of 52 injectates of the control group appeared distant to nerve epineurium.

CONCLUSION

Regardless of the applied SCT, i.e. high or low, all resin deposition was found adjacent to nerve epineurium. These findings suggest that high and low SCT result in equivalent needle tip localization in pigs.

Analgetikakombinationen zur postoperativen Schmerztherapie

BACKGROUND

The supplementation of an opioid by a non-opioid analgesic is a widely accepted technique for the treatment of postoperative pain. However, it is still unclear whether a combination of different non-opioids has an advantage in terms of an improved analgesia and/or a reduction of the opioid-related adverse effects.

METHODOLOGY

A systematic analysis of the literature was performed searching for randomized, controlled trials studying the effects of a combination of two non-opioid analgesics in order to reduce postoperative opioid requirements and/or postoperative pain. Significant reduction of the postoperative opioid requirement and/or postoperative pain were defined as main rating criteria. To facilitate comparisons between the trials, the relative (proportional) reduction of postoperative opioid administration and the relative reduction of postoperative pain were calculated on defined pain scales.

RESULTS

A total of 25 trials were identified, mainly studies comparing non-steroidal anti-inflammatory drugs (NSAIDs) with paracetamol. Only 3 trials found a statistically improved analgesic efficacy and 15 studies did not show any relevant improvement or the combination group was only significantly superior to one of the groups receiving monotherapy. A further seven studies could not be evaluated due to methodological issues. There was no evidence for a significant reduction of opioid-induced adverse effects.

CONCLUSION

A combination of non-opioid analgesics, in particular NSAIDs with paracetamol, cannot be recommended at present due to the lack of data showing improved effectiveness.

[Anaesthesia education at german university hospitals: the teachers' perspective -- results of a nationwide survey]

AIM OF THIS STUDY

The principle purpose of this study was to collect data on the conditions and practice of anaesthesia education as well as the teaching qualification of consultants at German university hospitals. Based upon the collected data, areas of weakness and strength as well as measures required to improve anaesthesia training are described.

METHODS

A questionnaire containing 26 items was mailed to 607 consultants employed at 41 German university hospitals in June 2003.

RESULTS

A total of 255 questionnaires was analysed (response rate: 43 %). Genuine training activities account for 14 % of the working hours of the participating consultants. On average, at the institutions of participating consultants, novices work for a duration of 1 month together with a consultant anaesthetist before they give anaesthetics without direct and constant supervision. When asked to describe the predominant method of training at their institution 71 % indicated "case-oriented teaching"; however, 53 % chose "see one, do one, teach one" and 49 % "learning by doing" as method of training as well (multiple choice). According to 63 % of respondents, departmental educational activities usually happen after their regular working hours. "Daily workload" (96 %), "time pressure" (96 %), "lack of time" (96 %) and "lack of personnel" (90 %) were indicated as the main obstacles of teaching. According to 80 % of respondents, a dedicated financial budget for education does not exist; instead, financial resources of third parties (industry) (58 %), of the state (for research und undergraduate education) (60 %) and of patients service (66 %) are used to ensure training of anaesthesia residents.

CONCLUSION

Due to a lack of a dedicated financial budget for resident training and an increasing economic pressure, "lack of time" and "lack of personnel" are the main factors leading to the situation at German university hospitals that consultants can only spend 14 % of their working hours for teaching purposes despite of sufficient qualification and motivation. As a consequence, novice anaesthetists are faced with the situation to be working without direct and constant supervision after 1 month of training.

Videolaryngoskopie zur modifizierten „Rapid-sequence-Narkoseeinleitung“

BACKGROUND

There is evidence that cricoid pressure, one of the key elements of rapid sequence induction (RSI) in patients at risk of aspiration, can distort the glottic view obtained by direct laryngoscopy (DL) and consequently impair or delay endotracheal intubation (ETI). The fact that cricoid pressure is applied by an assistant "blindly", i.e. without any visual feedback, is believed to be a contributing factor. Video laryngoscopy (VIL) offers the advantage that both the anaesthetist and the assistant can follow laryngoscopy. This could be useful for ETI during RSI.

METHODS

We used VIL for a simulated RSI in 170 adult patients randomised to either video laryngoscopy-guided application of cricoid pressure (group I) or conventional, i.e. "blind", application of cricoid pressure (group II). Time to ETI was compared between groups. The laryngoscopy view obtained by VIL was compared with the view of conventional DL obtained before, in all patients.

RESULTS

Time to ETI did not differ between groups (p=0.2): 25.1+/-14.2 s (group I) vs. 23.7+/-12.1 s (group II). Laryngoscopy scores were significantly better for VIL than conventional DL (p<0.001).

CONCLUSIONS

Visualisation of the larynx during RSI can be improved using VIL. Time to ETI is not decreased by use of video laryngoscopy-guided application of cricoid pressure.

Analysis of the subcellular localization of the proteins Rep, Rep' and Cap of porcine circovirus type 1

Porcine circovirus type 1 (PCV1) encodes two major ORFs. The cap gene comprises the major structural protein of PCV, the rep gene specifies Rep and Rep', which are both essential for initiating the replication of the viral DNA. Rep corresponds to the full-length protein, whereas Rep' is a truncated splice product that is frame-shifted in its C-terminal sequence. In this study, the cellular localization of PCV1-encoded proteins was investigated by immune fluorescence techniques using antibodies against Rep, Rep' and Cap and by expression of viral proteins fused to green and red fluorescence proteins. Rep and Rep' protein co-localized in the nucleus of infected cells as well as in cells transfected with plasmids expressing Rep and Rep' fused to fluorescence proteins, but no signal was seen in the nucleoli. Rep and Rep' carry three potential nuclear localization signals in their identical N-termini, and the contribution of these motifs to nuclear import was experimentally dissected. In contrast to the rep gene products, the localization of the Cap protein varied. While the Cap protein was restricted to the nucleoli in plasmid-transfected cells and was also localized in the nucleoli at an early stage of PCV1 infection, it was seen in the nucleoplasm and the cytoplasm later in infection, suggesting that a shuttling between distinct cellular compartments occurs.

Rep and Rep' protein of porcine circovirus type 1 bind to the origin of replication in vitro

Genome replication of Porcine circovirus type 1 (PCV1) relies upon expression of the full-length protein Rep and a spliced isoform (Rep'), and the presence of a 111-bp genomic fragment comprising the origin of replication. Using an electrophoretic mobility shift assay (EMSA), the capability of both Rep proteins to bind to partial fragments of the origin of replication of PCV1 was investigated in vitro. Both proteins formed complexes with double-stranded DNA origin fragments containing a stem-loop structure with a conserved nonamer and four hexamer repeats (5'-CGGCAG; H1 to H4). Use of truncated EMSA substrates identified minimal binding sites (MBS) for Rep and Rep' protein: The Rep binding site was mapped to the right leg of the stem-loop and the two inner hexamer repeats H1/H2, while binding of Rep' required only the presence of two hexamer repeats. Two differentially retarded complexes were observed with Rep protein, which presumably result from alternative binding to the MBS or to H3/4.