Thomas Wiesmann

Recommendations for anesthesia and perioperative management in patients with Ehlers-Danlos syndrome(s)

Ehlers-Danlos syndrome (EDS, ORPHA98249) comprises a group of clinically and genetically heterogeneous heritable connective tissue disorders, chiefly characterized by joint hypermobility and instability, skin texture anomalies, and vascular and soft tissue fragility. As many tissues can be involved, the underlying molecular defect can manifest itself in many organs and with varying degrees of severity, with widespread implications for anesthesia and perioperative management. This review focuses on issues relevant for anesthesia for elective and emergency surgery in EDS. We searched the literature for papers related to all EDS variants; at the moment most of the published data deals with the vascular subtype and, to a lesser extent, classic and hypermobility EDS. Knowledge is fragmented and consists mostly of case reports, small case series and expert opinion. Because EDS patients commonly require surgery, we have summarized some recommendations for general, obstetrical and regional anesthesia, as well as for hemostatic therapy.

Histological analysis after peripheral nerve puncture with pencil-point or Tuohy needletip

BACKGROUND:Continuous peripheral nerve blocks typically are performed with a “through-the-needle technique” and require needles with an inner diameter allowing catheter placement. In case of direct needle–nerve contact, the pencil-point needletip is currently considered less traumatic than are other needle configurations. In this study we determined whether nerve puncture with pencil-point needles is associated with fewer nerve injuries in comparison with Tuohy needles. METHODS:In 6 anesthetized pigs the brachial plexus were exposed bilaterally. Up to 8 nerves underwent nerve puncture with a pencil-point or a Tuohy needle. After 48 hours, the nerves were resected during anesthesia. The specimens were processed for visual examination and the detection of inflammatory cells, myelin damage, and intraneural hematoma. The grade of nerve injury was assessed using an objective score ranging from 0 (no injury) to 4 (severe injury). RESULTS:Fifty-eight nerves, including controls, were examined. According to the applied injury score, there was no significant difference between the pencil-point needle group [median (interquartile range) 3 (3–4)] and the Tuohy needle group [3 (3–4) P = 0.97]. The occurrence of posttraumatic regional inflammation, myelin damage, and intraneural hematoma was similarly high in both groups. CONCLUSIONS:Regardless of the needletip configuration applied for nerve puncture, pencil-point and Tuohy needletips may both lead to comparable magnitude of posttraumatic inflammation and considerable structural changes within the nerve. No significant differences were found comparing pencil-point with Tuohy tip–configured needles.

Minimal current intensity to elicit an evoked motor response cannot discern between needle-nerve contact and intraneural needle insertion.

BACKGROUND:The ability of an evoked motor response (EMR) with nerve stimulation to detect intraneural needle placement reliably at low current intensity has recently been challenged. In this study, we hypothesized that current intensity is higher in needle-nerve contact than in intraneural needle placement. METHODS:Brachial plexus nerves were exposed surgically in 6 anesthetized pigs. An insulated needle connected to a nerve stimulator was placed either with 1 mm distance to the nerve (control position), adjacent to nerve epineurium (needle-nerve contact position), or inside the nerve (intraneural position). Three pulse duration settings were applied in random fashion (0.1, 0.3, or 1.0 milliseconds) at each needle position. Starting at 0.0 mA, electrical current was increased until a minimal threshold current resulting in a specific EMR was observed. Fifty threshold current measurements were scheduled for each needle position-pulse duration setting. RESULTS:Four hundred-fifty threshold currents in 50 peripheral nerves were measured. Threshold current intensities (mA) to elicit EMR showed small differences between the needle-nerve contact position [median (25th–75th percentiles); 0.1 milliseconds: 0.12 (0.08–0.18) mA; 0.3 milliseconds: 0.10 (0.06–0.12) mA; 1.0 milliseconds: 0.06 (0.04–0.10) mA] and the intraneural position (0.1 milliseconds: 0.12 [0.10–0.16] mA; 0.3 milliseconds: 0.08 [0.06–0.10] mA; 1.0 milliseconds: 0.06 [0.06–0.08] mA) that are neither statistically significant nor clinically relevant. Regardless of the pulse duration that was applied, the 98.33% confidence interval revealed a difference of at most 0.02 mA. However, threshold current intensities to elicit EMR were lower for the needle-nerve contact position than for the control position (0.1 milliseconds: 0.28 [0.26–0.32] mA; 0.3 milliseconds: 0.20 [0.16–0.22] mA; 1.0 milliseconds: 0.12 [0.10–0.14] mA). CONCLUSIONS:The confidence interval for differences suggests minimal current intensity to elicit a motor response that cannot reliably discern between a needle-nerve contact from intraneural needle placement. In addition, an EMR at threshold currents <0.2 mA (irrespective of the applied pulse duration) indicates intraneural needle placement or needle-nerve contact.

Postoperative nausea and vomiting -- a narrative review of pathophysiology, pharmacotherapy and clinical management strategies

Introduction: Postoperative nausea and vomiting (PONV) are common complications concerning patients undergoing general anesthesia. Intensive research was performed during the last two decades in order to develop therapeutic and prophylactic strategies to prevent this complication. Areas covered: This article reviews the pathophysiology as well as pharmacological aspects of PONV prophylaxis and treatment. Relevant strategic aspects for pharmacological prophylaxis of PONV are discussed and clinical standard operating procedures are presented. Expert opinion: The expert opinion focuses on poor implementation of actual PONV guidelines and future considerations.

Compound imaging technology and echogenic needle design: effects on needle visibility and tissue imaging.

Introduction Needle visualization in ultrasound-guided regional anesthesia can be improved by using needles of echogenic design with higher rate of reflection of ultrasound waves. Imaging solutions such as compound imaging might further improve imaging of both needle and tissue; these effects have not yet been studied. We hypothesized that compound imaging would significantly improve needle visibility, regardless of the insertion angle or needle type used. The effects of compound imaging on needle artifacts and tissue imaging were also investigated. Methods A total of 200 video clips of in-plane needle insertions were obtained in embalmed cadavers with a conventional needle and an echogenic needle at 5 different insertion angles, with both conventional B-mode ultrasound imaging and compound imaging technology. Visibility of the needle shaft and needle tip as well as the needle artifact rate were assessed by a blinded investigator on a 4-point ordinal scale. The effects on tissue image quality and speckle artifacts were also assessed. Stepwise linear regression was performed to differentiate effects on needle visibility scores. Results Imaging of the needle shaft and tip was significantly enhanced when compound imaging technology was used (P < 0.0001). Use of echogenically designed needles or shallow needle insertion angles improved visibility of both shaft and tip (both P < 0.0001). With compound imaging, there are fewer needle artifacts, and tissue imaging quality and speckle artifact rate are significantly improved. Conclusions Compound imaging technology enhances needle imaging with both echogenic and conventional needles. Tissue imaging and speckle artifacts are also optimized. Echogenic needle design results in better needle visibility scores in both B-mode and compound imaging.

Perineural Hematoma May Result in Nerve Inflammation and Myelin Damage

Background and Objectives Perineural hematoma may occur during performance of peripheral nerve blocks. The aim of this study was to test the hypothesis that an iatrogenic hematoma in the immediate vicinity of a peripheral nerve may cause histologic evidence of nerve injury. Methods Fifty milliliters of autologous blood was injected adjacent to the right sciatic nerve in 20 anesthetized female pigs. In order to discern between blood-related volume and immune effects, 50 mL of albumin was injected at the same location in an additional 22 pigs. Either blood or albumin was injected in random order. The left sciatic nerve served as a negative control in all animals, that is, either no needle placement or needle placement without injection. After 48 hours, the nerves were resected. The grade of nerve injury was scored from 0 (no injury) to 3 (severe injury) by histologic analysis of myelin tissue and inflammatory cells. Results Eighty-two nerve specimens were examined. Injury scores were significantly (P < 0.01) higher in the blood injection (n = 20; median [interquartile range] 2 [2-2]) and albumin injection (n = 22, 1 [1–2]) conditions compared with the no needle placement (n = 22, 0 [0–1]) and “dry needle placement” (n = 20, 1 [0–1]) conditions. Widespread inflammatory changes were seen in the blood injection group, in which 15% of nerve specimens showed damage to myelin. Conclusions Our data suggest that hematoma adjacent to nerve tissue may result in structural nerve injury and inflammatory changes.

Dual guidance improves needle tip placement for peripheral nerve blocks in a porcine model

The objective of the study was to evaluate whether the use of ultrasound (US) together with nerve stimulation (USNST) provides a better needle tip position for performing peripheral regional anaesthesia than the use of US or nerve stimulation (NST) alone.

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.

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

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.

Needle visibility in different tissue models for ultrasound-guided regional anaesthesia

Models for ultrasound‐guided regional anaesthesia (USGRA) are important for research and training. However, the limited data available show great differences in quality of needle and tissue visualisation with regard to the applied model. This study aims to compare common USGRA models and human tissue with regard to their influence on needle visibility.