[Hypotension induced by spinal anesthesia during cesarean section : Current treatment concepts]. / Spinalanästhesieinduzierte Hypotension bei Sectio caesarea : Aktuelle Behandlungskonzepte.

Arterial hypotension during cesarean delivery under spinal anesthesia can cause maternal and fetal adverse effects. Therefore, current guidelines recommend the continuous and preferably prophylactic use of vasopressors, emphasizing the use of alpha-agonists, such as phenylephrine. Besides a left lateral uterine displacement either an intravenous colloid preloading or a crystalloid co-loading is recommended. The blood pressure goal is to maintain a systolic arterial blood pressure of at least 90% of the initial baseline value and to avoid a drop to less than 80% of this baseline. To achieve this goal a prophylactic continuous phenylephrine infusion with an adjustable flow rate is recommended. It is advised to start with an initial dose of 25-50 µg/min, initiated immediately following the intrathecal injection of the local anesthetic and titrated according to the vital parameters. Parturients with cardiac diseases should be preoperatively evaluated following individual hemodynamic goals.

[Regional anesthesia in daily clinical practice: an economic analysis based on case vignettes]. / Regionalanästhesie im klinischen Alltag: eine ökonomische Analyse anhand eines Versorgungsbeispiels.

BACKGROUND: The economic effect is a crucial aspect of every medical procedure. This article analyzes the economic implications of various methods in anesthesia based on three case vignettes. METHODS: The management of anesthesia of a forearm fracture with sufficient brachial plexus blockade, general anesthesia and insufficient brachial plexus blockade with subsequent general anesthesia was analyzed with respect to the relevant cost factors (personnel costs, durables, consumables, fixed assets costs, anesthesia-related overhead costs). RESULTS: Sufficient regional anesthesia was the least expensive method for a forearm fracture with 324.26 €, followed by general anesthesia with 399.18 € (+23% compared with regional anesthesia). Insufficient regional anesthesia was most the expensive method, which necessitated an additional general anesthesia (482.55 €, +49% compared with sufficient regional anesthesia). CONCLUSION: Even considering that this cost analysis was calculated based on data from only one medical institution (General Hospital of Vienna, Medical University of Vienna), regional anesthesia appeared to be cost efficient compared with other anesthesia procedures. Main cost drivers in this example were personnel costs.

Cutaneous innervation of the hand: clinical testing in volunteers shows high intra- and inter-individual variability.

BACKGROUND: Many clinicians require a solid understanding of the anatomical areas supplied by specific peripheral nerves. Virtually all pertinent medical textbooks claim that the entire (palmar and dorsal) surface of the hand is supplied by three (median, radial, and ulnar) nerves and that each of these covers a well-defined area. This study was designed to evaluate the sensory-distribution pattern of peripheral nerves in the hand. METHODS: Twelve volunteers were enrolled and randomly allocated to have median, ulnar, or radial nerve blocks to each hand on three successive days. All blocks were performed using ultrasound guidance. A neurologist carried out pinprick testing to define the sensory-distribution area of each procedure. The hand surface was then scanned, and the sensory-distribution area of the blocked nerve was traced, measured, and quantified in relation to the entire hand surface for descriptive and comparative statistical analyses. RESULTS: The sensory-distribution areas of the three nerves revealed a high degree of inter-individual and intra-individual variabilities. Sizeable areas were not covered by any of the three nerves, again involving great variability. Conversely, 15 of the 24 hands showed areas of overlapping supply from more than one nerve. CONCLUSIONS: Our findings suggest that the anatomical areas supplied by peripheral nerves are characterised by much greater variability than is routinely claimed. CLINICAL TRIAL REGISTRATION: DRKS00010707.

Penetration of linezolid into synovial fluid and muscle tissue after elective arthroscopy.

Objectives: Penetration of antibiotics into synovial fluid is crucial to combat septic arthritis efficiently. Since linezolid may be used for treatment of septic arthritis when methicillin-resistant bacterial strains are suspected, we investigated its target-site concentrations in synovial fluid. Patients and methods: Ten patients undergoing elective knee arthroscopy were included in this study. Subjects received a single dose of 600 mg of linezolid intravenously and linezolid concentrations were measured in plasma and by using microdialysis in muscle tissue and synovial fluid. Pharmacokinetic/pharmacodynamic calculations to predict bacterial killing ability were performed using CLSI breakpoints and MIC90 for clinical isolates. Results: All 10 subjects tolerated linezolid well. As indicated by AUCtissue/AUCfree plasma ratios of 0.76 ±âŸ0.34 (synovial fluid) and 0.98 ±âŸ0.62 (muscle tissue) linezolid penetrated well into the knee gap and tissue. In synovial fluid AUC0-24/MIC ratios for bacteria with an MIC of 1, 2 and 4 mg/L were 86.8 ±âŸ47.0, 43.4 ±âŸ23.5 and 21.7 ±âŸ11.8, respectively. Conclusions: Linezolid may be used to treat septic arthritis caused by bacterial strains with an MIC ≤1 mg/L. Assuming a pharmacokinetic/pharmacodynamic target of > 50 for AUC0-24/MIC, when treating strains with an MIC >1 mg/L treatment surveillance is warranted. However, pharmacokinetic/pharmacodynamic targets for tissue are poorly understood and clinical data are needed to verify our assumptions.

Pharmacokinetics of Cefuroxime in Synovial Fluid.

Cefuroxime is frequently used as preoperative antibiotic prophylaxis and may be used for the treatment of septic arthritis. A prerequisite for successful treatment of septic arthritis is the ability of an antibiotic agent to penetrate into the target site. Therefore, the concentration of cefuroxime in synovial fluid was evaluated. Ten patients who underwent elective knee arthroscopy were included in this study. Patients were treated with a single dose of 1,500 mg cefuroxime intravenously, and subsequently, the concentrations in plasma, the interstitial fluid of muscle tissue, and synovial fluid were measured by using microdialysis. Pharmacokinetic/pharmacodynamic calculations to predict bacterial killing were performed using the epidemiologically defined MIC90 for clinical isolates and CLSI breakpoints. Cefuroxime penetrated excellently into muscle tissue (ratio of the area under the concentration-time curve [AUC] for muscle tissue/AUC for free plasma, 1.79) and synovial fluid (ratio of the AUC for synovial fluid/AUC for free plasma, 1.94). The cefuroxime concentration was greater than the MIC90 for Staphylococcus aureus and S. epidermidis strains (≤2 mg/liter) over the complete dosing interval (the percentage of the dosing interval during which the free cefuroxime concentration exceeded the MIC for the pathogen [fTMIC]). CLSI defines staphylococci with MICs of ≤8 mg/liter to be susceptible to cefuroxime. For staphylococci with MICs of ≤8 mg/liter, the fTMIC in plasma was 52.5%, while the fTMIC in muscle tissue and synovial fluid was 93.6% and 96.3%, respectively. Cefuroxime may be used to treat septic arthritis caused by susceptible bacterial strains (MIC ≤ 8 mg/liter). The activity of cefuroxime in septic arthritis might be underestimated when relying exclusively on plasma concentrations.

An observational study of the macro- and micro-haemodynamic implications of epidural anaesthesia in children.

The haemodynamic implications of epidural anaesthesia in children are poorly documented. We report macro- and micro-haemodynamic data from an observational study of 25 children ranging from neonates to six-years old, who underwent surgery conducted with a specific combination of monitoring systems. We analysed 90 min of study-related monitoring after epidural catheterisation, with skin incision taking place after around 30 min. We recorded macrohaemodynamic parameters (monitored using LiDCOrapid) including heart rate, mean arterial pressure, cardiac output, stroke volume, systemic vascular resistance and stroke volume variation. Microhaemodynamic parameters (monitored using Invos™) included cerebral and peri-renal oxygenation. Based on the entire 90 min of study-related monitoring, we found significant increases in cardiac output (p = 0.009), stroke volume (p = 0.006) and stroke volume variation (p = 0.008), as well as decreases in systemic vascular resistance (p = 0.007) around 30 min after epidural blockade. There were no significant changes in heart rate, arterial pressure and cerebral or peri-renal oxygenation during these 90 min. Considering that the microhaemodynamic parameters were not affected by the macrohaemodynamic changes, we conclude that autoregulation of the brain and the kidneys was maintained in children under epidural anaesthesia.

[Hygiene aspects in ultrasound-guided regional anesthesia]. / Hygieneaspekte in der ultraschallgestützten Regionalanästhesie.

BACKGROUND: Sterile and clean working conditions are one of the keystones of medical practice and this is also true for ultrasound-guided regional anesthesia. The routine clinical practice in ultrasound-guided regional anesthesia does not always comply with the principles of sterile and clean working conditions in medicine: therefore, patients are exposed to potential hazards regarding the transmission of pathogens via the ultrasound equipment. OBJECTIVE: This article deals with the question of whether sterile working conditions in ultrasound-guided regional anesthesia are a relevant topic with medical and economic implications. Is it possible to implement the general recommendations for sterile working conditions in ultrasonography for the specific application of ultrasound-guided regional anesthesia? MATERIAL AND METHODS: A search of the available literature and published guidelines in the field of sterile working conditions with ultrasound was carried out. RESULTS: The association between cross-infections and ultrasound equipment is undeniable. Many methods for cleansing and disinfection of ultrasound equipment have been published. All these methods are associated with advantages and disadvantages. The direct sterilization of ultrasound probes with high-percentage alcohol can damage ultrasound probes (especially linear). The use of self-adhesive sterile ultrasound probe covers is a practical method to achieve sterile working conditions in ultrasound-guided regional anesthesia. CONCLUSION: The use of sterile ultrasound probe covers and sterile ultrasound contact media is an important prerequisite to avoid cross-infection between patients. An appropriate scientific evaluation should serve as evidence in this field.

Lumbar neuraxial anatomical changes throughout pregnancy: a longitudinal study using serial ultrasound scans.

This observational study was designed to investigate the anatomical changes of the lumbar spine over the course of pregnancy using serial ultrasound scans. We performed paramedian scans on 58 women at the L2-3, L3-4 and L4-5 levels; these were done at four periods of 11+0-13+6, 19+0-23+0, 28+0-32+0 and 38+0-40+0 weeks gestation. At each intervertebral level, the length of the interlaminar space, length of the visible intervertebral posterior dura and depth of the posterior dura mater from the skin were measured. The length of the interlaminar space and length of the visible intervertebral posterior dura mater were longer, and the depth of the posterior dura mater was shallower, with ascending spinal interspace. The depth of the posterior dura mater increased during pregnancy, although it plateaued between the third and fourth measurement periods. The other spinal measurements were not affected by gestation. These findings indicate that the L2-3 level is the most appropriate puncture site for epidural anaesthesia in pregnant women. Our results ought to be embraced as a departure point towards developing neuraxial insertion techniques guided or aided by ultrasound.

Effective local anaesthetic volumes for sciatic nerve blockade: a clinical evaluation of the ED99.

Previous results in volunteers have indicated the effective dose in 99% of subjects (ED99 ) of local anaesthetic volume to be 0.10 ml.mm(-2) of cross-sectional nerve area for sciatic nerve blockade. The objective of this prospective, randomised, double-blind study was to investigate the ED99 of local anaesthetic for ultrasound-guided sciatic nerve blockade in patients undergoing foot surgery, according to Dixon's up-and-down method and probit analysis. A starting volume of 0.20 ml local anaesthetic per mm(2) cross-sectional nerve area was used. If surgical anaesthesia was judged to be adequate, the volume of local anaesthetic for the next case was reduced by 0.02 ml.mm(-2), until the first block failed. Thereafter, the volume of local anaesthetic was increased by 0.02 ml.mm(-2). The ED99 volume of local anaesthetic for ultrasound-guided sciatic nerve blockade was calculated to be 0.15 ml.mm(-2) cross-sectional nerve area, which is higher than the previously evaluated ED99 volume in volunteers.

A retrospective analysis of 509 consecutive interscalene catheter insertions for ambulatory surgery.

Effective pain therapy after shoulder surgery is the main prerequisite for safe management in an ambulatory setting. We evaluated adverse events and hospital re-admission using a database of 509 interscalene catheters inserted during ambulatory shoulder surgery. Adverse events were recorded for 34 (6.7%) patients (9 (1.8%) catheter dislocations diagnosed in the recovery room, 9 (1.8%) catheter dislocations at home with pain, 2 (0.4%) pain without catheter dislocation, 1 (0.2%) 'secondary' pneumothorax without intervention and 13 (2.6%) other). Twelve (2.4%) patients were re-admitted to hospital (8 (1.6%) for pain, 2 (0.4%) for dyspnoea and 2 (0.4%) for nausea and vomiting), 9 of whom had rotator cuff repair. A well-organised infrastructure, optimally trained medical professionals and appropriate patient selection are the main prerequisites for the safe, effective implementation of ambulatory interscalene catheters in routine clinical practice.

Reduction of cerebral mean blood flow velocity and oxygenation after high-volume (1.5 ml kg⁻¹) caudal block in infants.

BACKGROUND: We have recently described a bi-directional bulk flow of cerebrospinal fluid (CSF) (coined 'the CSF rebound mechanism') after the use of high-volume caudal block in infants, which may explain the secondary longitudinal spread of the block. If important the initial cephalad transfer of CSF should be of such a magnitude that it would cause a transient reduction in cerebral blood flow (CBF) and cerebral oxygenation. The primary aim of this observational study was to delineate the magnitude of the reduction of CBF velocity (CBFV) associated with high-volume caudal block in infants. METHODS: Ultrasound Doppler measurements of CBFV in the middle cerebral artery and also haemodynamic parameters and cerebral regional oxygenation (C(R)SO2) were followed during 5 min after the initial caudal injection (1.5 ml kg(-1), ropivacaine 0.2%) in 12 infants <3 months of age. RESULTS: The caudal injection was associated with immediate and major reductions in CBFV indicating a concomitant reduction in CBF. A significant reduction of cerebral regional oxygenation C(R)SO2 was also observed. Systemic haemodynamic parameters were unchanged during the observation period. CONCLUSION: High-volume caudal block causes a biphasic change in CBFV and was also found to affect cerebral oxygenation. Our findings lend further support to 'the CSF rebound mechanism' for secondary spread of high-volume caudal block.

Does circumferential spread of local anaesthetic improve the success of peripheral nerve block?

BACKGROUND: The relation between the pattern of local anaesthetic (LA) spread and the quality of peripheral nerve block is unclear. METHODS: Twenty-one volunteers were randomized to receive a median nerve block with intended circumferential or intended non-circumferential spread of LA. Different predetermined volumes and needle placement techniques were used to produce the different patterns of LA spread. Volumetric, multiplanar 3D ultrasound imaging was performed to evaluate the pattern and extent of LA spread. Sensory block was assessed at predetermined intervals. RESULTS: Complete circumferential spread of LA was achieved in only 67% of cases in the intended circumferential study group and in 33% of cases in the intended non-circumferential group. Block success was similar (90%) and independent of whether circumferential or non-circumferential spread of the LA was achieved. All block failures (n=4) occurred in the intended non-circumferential group with low volumes of LA. The onset of sensory block (independent of group allocation) was faster with circumferential spread of LA [median (IQR) onset time, 15 (8; 20) min] compared with non-circumferential spread of LA [median (IQR) onset time, 20 (15; 30) min]. More LA was used for circumferential blocks [median (IQR) volume of LA 2.8 (1.3; 3.6) vs 1.3 (1.1; 2.4) ml]. CONCLUSIONS: Even under optimal conditions, it was not possible to achieve circumferential spread of LA in all intended cases. The success of median nerve block seems to be independent of the pattern of LA spread. CLINICAL TRIAL REGISTRATION: DRKS 00003826.

Dislocation rates of perineural catheters: a volunteer study.

BACKGROUND: Dislocation rates of continuous peripheral nerve block are poorly described even though this technique is frequently used in clinical practice. The present study was designed to evaluate dislocation rates over time of interscalene and femoral nerve catheters under defined experimental circumstances. Ultrasound (US) monitoring was used to detect the position of the perineural catheters. METHODS: Twenty volunteers received US-guided interscalene and femoral nerve catheters. The volunteers performed standardized physical exercises in regular intervals and the position of both catheters was examined by US confirmation of the spread of fluid. The maximal time of investigation in each volunteer was 6 h. The main outcome parameters were the overall dislocation rates and the cumulative dislocation rates at a given time point. RESULTS: We observed an overall dislocation rate of 15% (5% for interscalene catheters, 25% for femoral nerve catheters) and a significant correlation between time and rate of dislocations (r=0.99, P=0.001). US visualization of the spread of fluid was possible in all cases. CONCLUSIONS: This is the first dedicated evaluation of dislocation rates of peripheral nerve catheters (PNCs) via US investigation. Both movement and time are considerable factors for perineural catheter displacement. US is useful for the performance of PNCs and for the continuous detection of the spread of fluid relative to the nerve and adjacent anatomical structures. Translational research is required to confirm the study results in the clinical practice.

Dexmedetomidine as an adjuvant to ropivacaine prolongs peripheral nerve block: a volunteer study.

BACKGROUND: Dexmedetomidine is an α-2-receptor agonist which might be used as an additive to local anaesthetics for various regional anaesthetic techniques. We therefore designed this prospective, double-blinded, controlled volunteer study to investigate the effects of dexmedetomidine as an adjuvant to ropivacaine on peripheral nerve block. METHODS: Ultrasound-guided ulnar nerve block (UNB) was performed in 36 volunteers with either 3 ml ropivacaine 0.75% (R), 3 ml ropivacaine 0.75% plus 20 µg dexmedetomidine (RpD), or 3 ml ropivacaine 0.75% plus systemic 20 µg dexmedetomidine (RsD). UNB-related sensory and motor scores were evaluated. RESULTS: Sensory onset time of UNB was not different between the study groups, whereas motor onset time was significantly faster in Group RpD when compared with the other study groups [mean (sd)] [21 (15) vs 43 (25) min in Group RsD and 47 (36) min in Group R, P<0.05 Group RpD vs other groups]. The duration of sensory block was 350 (54) min in Group R, 555 (118) min in Group RpD, and 395 (40) min in Group RsD (P<0.01 Group RpD vs other groups, P<0.05 Group RsD vs Group R). Motor block duration was similar to the duration of sensory block. CONCLUSIONS: A profound prolongation of UNB of ∼60% was detected with perineural dexmedetomidine when added to 0.75% ropivacaine. The systemic administration of 20 µg dexmedetomidine resulted in a prolongation of ∼10% during UNB with 0.75% ropivacaine. Eudra-CT No.: 2012-000030-19.