Tuning in C-nociceptors to reveal mechanisms in chronic neuropathic pain.

OBJECTIVE: Develop and validate a low-intensity sinusoidal electrical stimulation paradigm to preferentially activate C-fibers in human skin. METHODS: Sinusoidal transcutaneous stimulation (4Hz) was assessed psychophysically in healthy volunteers (n = 14) and neuropathic pain patients (n = 9). Pursuing laser Doppler imaging and single nociceptor recordings in vivo in humans (microneurography) and pigs confirmed the activation of "silent" C-nociceptors. Synchronized C-fiber compound action potentials were evoked in isolated human nerve fascicles in vitro. Live cell imaging of L4 dorsal root ganglia in anesthetized mice verified the recruitment of small-diameter neurons during transcutaneous 4-Hz stimulation of the hindpaw (0.4mA). RESULTS: Transcutaneous sinusoidal current (0.05-0.4mA, 4Hz) activated "polymodal" C-fibers (50% at ∼0.03mA) and "silent" nociceptors (50% at ∼0.04mA), intensities substantially lower than that required with transcutaneous 1-ms rectangular pulses ("polymodal" ∼3mA, "silent" ∼50mA). The stimulation induced delayed burning (nonpulsating) pain and a pronounced axon-reflex erythema, both indicative of C-nociceptor activation. Pain ratings to repetitive stimulation (1 minute, 4Hz) adapted in healthy volunteers by Numeric Rating Scale (NRS) -3 and nonpainful skin sites of neuropathic pain patients by NRS -0.5, whereas pain even increased in painful neuropathic skin by approximately NRS +2. INTERPRETATION: Sinusoidal electrical stimulation at 4Hz enables preferential activation of C-nociceptors in pig and human skin that accommodates during ongoing (1-minute) stimulation. Absence of such accommodation in neuropathic pain patients suggest axonal hyperexcitability that could be predictive of alterations in peripheral nociceptor encoding and offer a potential therapeutic entry point for topical analgesic treatment. Ann Neurol 2018;83:945-957.

Implementation and Evaluation of a Web-Based Distribution System For Anesthesia Department Guidelines and Standard Operating Procedures: Qualitative Study and Content Analysis.

BACKGROUND: Digitization is spreading exponentially in medical care, with improved availability of electronic devices. Guidelines and standard operating procedures (SOPs) form an important part of daily clinical routine, and adherence is associated with improved outcomes. OBJECTIVE: This study aimed to evaluate a digital solution for the maintenance and distribution of SOPs and guidelines in 2 different anesthesiology departments in Switzerland. METHODS: A content management system (CMS), WordPress, was set up in 2 tertiary-level hospitals within 1 year: the Department of Anesthesiology and Pain Medicine at the Kantonsspital Lucerne in Lucerne, Switzerland, as an open-access system, followed by a similar system for internal usage in the Department of Anaesthesiology and Pain Medicine of the Inselspital, Bern University Hospital, in Bern, Switzerland. We analyzed the requirements and implementation processes needed to successfully set up these systems, and we evaluated the systems' impact by analyzing content and usage. RESULTS: The systems' generated exportable metadata, such as traffic and content. Analysis of the exported metadata showed that the Lucerne website had 269 pages managed by 44 users, with 88,124 visits per month (worldwide access possible), and the Bern website had 341 pages managed by 35 users, with 1765 visits per month (access only possible from within the institution). Creation of an open-access system resulted in third-party interest in the published guidelines and SOPs. The implementation process can be performed over the course of 1 year and setup and maintenance costs are low. CONCLUSIONS: A CMS, such as WordPress, is a suitable solution for distributing and managing guidelines and SOPs. Content is easily accessible and is accessed frequently. Metadata from the system allow live monitoring of usage and suggest that the system be accepted and appreciated by the users. In the future, Web-based solutions could be an important tool to handle guidelines and SOPs, but further studies are needed to assess the effect of these systems.

[Measurement of attitudes toward interprofessional collaboration in an operating theatre - a cross-sectional study]. / Messung der Haltung zur interprofessionellen Zusammenarbeit in einer Operationsabteilung ­ eine Querschnittsstudie.

Measurement of attitudes toward interprofessional collaboration in an operating theatre - a cross-sectional study Abstract.Background: Interprofessional cooperation (IC) between healthcare professionals is essential for good treatment outcomes. Surgical departments place special demands on interprofessional cooperation (situational team formation, alterning work environment, coordinative overcrowding of work) within a health organisation. In order to achieve common goals in a team, it is important that those involved have a comparable understanding of and attitude towards interprofessional cooperation, regardless of their profession. Research Question: What is the internal consistency of the German version of the Jefferson Scale of Attitudes Toward Interprofessional Collaboration (JeffSATIC) when applied to personnel in an operating theatre? What is the attitude towards interprofessional cooperation between the various occupational groups in a surgical department of an acute care hospital functioning as a centre and a training establishment? Are there differences between the individual occupational groups and the sexes? Method: The validated JeffSATIC questionnaire was translated back into German and sent to 283 people in a surgical department with eleven operating theatres. The internal consistency of the questionnaire and differences in attitude towards interprofessional cooperation were examined. Findings: The German version of the JeffSATIC questionnaire is a reliable instrument for measuring the attitude of individuals towards interprofessional cooperation. It was used for the first time in the context of a surgical department. In the institution examined, there are no statistically significant differences between the different occupational groups and sexes in relation to the attitude to IC in the dimensions 'work relationship' and 'responsibility' determined by the questionnaire. The medical service anaesthesia shows the greatest divergence in attitude towards interprofessional cooperation within a professional group. Conclusions: In the institution examined, the prerequisites for successful interprofessional cooperation exist. In general, it should be further examined which factors influence the divergence in attitude per occupational group and whether these divergences in attitude are also associated with the quality of the actual cooperation.

How current transfusion practices in geriatric patients with hip fracture still differ from current guidelines and the effects on outcome: A retrospective observational study.

BACKGROUND: Transfusion guidelines have become increasingly restrictive. We investigated actual transfusion practices in geriatric hip fracture patients, why they differ from current guidelines and how this affects outcome. OBJECTIVES: The primary aim was to examine transfusion timing, evaluate how many red blood cell (RBC) transfusions are in keeping with guidelines and how this affects morbidity (infection, cardiac events and delirium), mortality and length of stay (LOS). Our secondary aim was to test the hypothesis that guidelines were more likely to be deviated from shortly before discharge and with consecutive transfusions. DESIGN: A retrospective observational study. SETTING: The Luzerner Kantonsspital, a major trauma centre, over a 12-month period from 1 February 2015 to 31 January 2016. PATIENTS: All patients over 70 years of age admitted to the Luzerner Kantonsspital with hip fractures over a 12-month period in 2015 to 2016 were included. RESULTS: 156 patients were included, to which 141 units of RBCs were transfused. All pre and intra-operative transfusions were according to guidelines; 110 transfusions were postoperative and 37 of these were not according to guidelines. Patients who were transfused had longer LOS in hospital (P = 0.002) and an odds ratio (OR) of 2.7 of contracting an infection (P = 0.04) in comparison with patients who were not transfused. No significant differences in mortality, LOS or morbidity were found between patients transfused according to guidelines and more liberal thresholds. Guidelines were more likely to be deviated from within the last 2 days before discharge than prior to this (58 vs. 24%, P = 0.03). Furthermore, 24 stable patients received two consecutive RBC units resulting in posttransfusion haemoglobin values of between 83 and 124 g l. CONCLUSION: Most RBC transfusions occur postoperatively, many still according to liberal transfusion thresholds, in particular shortly before discharge and as part of consecutive transfusions. Transfused patients had longer LOS and more infections than patients not transfused, but there was no difference in mortality, LOS or morbidity between patients transfused according to current guidelines and those where guidelines were deviated from.

[OR-management and self-improvement - a discrepancy?]. / OP-Management - OP-Management†/†effiziente Klinikführung und Weiterbildung - ein Widerspruch?

Today, operating room management is essential for a modern hospital. The strategic controls of this cost-intensive area and the ongoing cost pressure have necessitated management attention to this area. Economical, processual and quality data are well-known and established, although analysis of different health delivering organisations by benchmarking is still difficult. It remains still a severe task for the management of an OR and anaesthesia department. For these fields data is needed to identify and measure the performance of these departments in the dimensions of finances, development, processes and patient's needs. The key performance indicators are exemplified for an anaesthesia department and discussed.

[Case report - a dangerous intoxication after ingestion of alkyl nitrite ("poppers")]. / Kasuistik - Schwere Intoxikation nach oraler Einnahme von Alkylnitrit ("Poppers").

This case report describes the inadvertent poisoning of a young man with "poppers" after having ingested an unknown amout of the drug. "Poppers" (alkyl nitrite) were made famous in the 1960s as a party drug, and during certain sexual practices, and are still in use today. The drug's inhalation leads to a short-lived rush, vasodilation and relaxtion of smooth muscles. An accidental ingestion can lead to a significant build-up of methemoglobin with dire consequences. The therapy consists of the intravenous administration of methylene blue.

Mechano-insensitive nociceptors are sufficient to induce histamine-induced itch.

The nerve fibres underlying histamine-induced itch have not been fully elucidated. We blocked the lateral femoral cutaneous nerve and mapped the skin area unresponsive to mechanical stimulation, but still sensitive to electrically induced pain. Nerve block induced significantly larger anaesthetic areas to mechanical (100 mN pin-prick, 402 ± 61 cm²; brush, 393 ± 63 cm²) and heat pain stimuli (401 ± 53 cm²) compared with electrical stimulation (352 ± 62 cm², p < 0.05), whereas the anaesthetic area tested with 260 mN (374 ± 57 cm²) did not differ significantly. Histamine was applied by iontophoresis (7.5 mC) at skin sites in which mechanical sensitivity was blocked, but electrical stimulation was still perceived 30 min after the nerve block (n = 9). In these areas iontophoresis of histamine provoked itching in 8/9 subjects with a mean maximum of 4.6 ± 1 (on an 11-point rating scale). Histamine-induced itch can thus be perceived at skin sites where input from mechano-sensitive polymodal nociceptors is blocked. In conclusion, input from mechano-insensitive nociceptors is sufficient to generate histamine-induced itch.

Anaesthesia related complications - a single centre data analysis at a tertiary hospital in central Switzerland.

AIMS: Anaesthesia safety has improved over time with severe anaesthesia-related complications and death becoming rare events. We investigated anaesthesia-related complications over a period of 17 years in this single centre retrospective observational cohort study. The main aims were to assess the temporal trends of anaesthesia-related complications, their distribution among clinics and their relation to emergency versus non-emergency interventions. METHODS: In this retrospective, observational cohort study, anaesthesia and event protocols of patients who suffered from an anaesthesia-related complication were collected in the period from 1 January 2003 to 31 December 2019. These data sets were anonymised and grouped into demographic information, ASA physical status, information about dental status and hospital department. Out of the total of 257 cases that were reported to the department of anaesthesia at the Luzerner Kantonsspital, 110 were excluded as they were not anaesthesia-related and 14 because of incomplete reporting forms. The different complications were categorised by the severity injury scale score. The total number of anaesthetics during the study period amounted to 399,583. RESULTS: 133 patients with complications were included. Six patients died owing to a partially anaesthesia-related complication, two suffered from permanent damage, 62 had temporary symptoms and in 63 patients dental damage occurred. The temporal trend showed a major decrease in severe anaesthesia complications and deaths, whiledental injuries were the main complications after 2010. Most of the complications were reported in the orthopaedic department, whereas dental injuries were predominantly reported in the otorhinolaryngology department. The majority of complications occurred during elective surgery although this was not significant (p = 0.53). CONCLUSIONS: Severe anaesthesia-related complications and death decreased dramatically during the study period. Anaesthesia complications are not more frequent in emergency surgeries. Overall, complications occurred more frequently in orthopaedics, and dental injuries predominated in otorhinolaryngology.

[Use of high-flow oxygen treatment in the emergency medical service: what are the dangers for users from the perspective of occupational and fire protection?] / Anwendung von "High-flow"-Sauerstoff-Therapie im Rettungsdienst: Welche Gefahren ergeben sich für Anwender aus der Perspektive des Arbeits- und Brandschutzes?

INTRODUCTION: The administration of high concentrations of oxygen may harm patients or paramedics by increasing the probability of fire. The presented work investigated the effect of oxygen applied via high flow in different concentrations and flow rates on environmental oxygen concentrations in the patient compartment of an ambulance. RESULTS: Environmental oxygen concentrations increased rapidly over time and oxygen is stored in blankets and clothes over a long period. Simulation in a fire laboratory showed that also in high oxygen concentration settings fire needs a flame or temperatures above 300 °C. Sparks alone were not able to start a fire. CONCLUSION: Ventilation of patient compartment and clothes with ambient air are mandatory to reduce dangerous oxygen concentrations in transport of patients on high-flow oxygen treatment.

Long-acting local anesthetics attenuate FMLP-induced acute lung injury in rats.

BACKGROUND: Endothelin-1 (ET-1) is a mediator of lung diseases and a potent pulmonary vasoconstrictor. In addition to thromboxane A2, it participates in the formation of lung edema. Both lidocaine and mepivacaine attenuate the increase of pulmonary arterial pressure (PAP) and lung edema development. We examined the effects of procaine, bupivacaine, and ropivacaine on experimentally evoked PAP increase and ET-1 release. METHODS: PAP and lung weight were measured in isolated rat lungs during perfusion with Krebs-Henseleit hydroxyethyl starch buffer. Bupivacaine, ropivacaine, or procaine was added to the solution at concentrations of 10(-2)-10(-7) mg/kg. ET-1 levels were measured in the perfusate by enzyme-immunoassay, and thromboxane A2 levels were assayed by radioimmunoassay. N-formyl-L-leucine-methionyl-L-phenylalanine was used to activate human polymorphonuclear neutrophils. RESULTS: Bupivacaine, ropivacaine, and procaine significantly attenuated increases of PAP (P < 0.05) and resulted in a reduction of lung weight in these treatment groups compared with the sham group (P < 0.05). The long-acting anesthetics bupivacaine and ropivacaine (P < 0.05), but not procaine, reduced ET-1 levels, produced low inflammation rates, and did not affect lung structures at doses from 10(-3) to 10(-6) mg/kg. CONCLUSION: Bupivacaine and ropivacaine attenuated N-formyl-L-leucine-methionyl-L-phenylalanine-induced PAP, reduced lung edema, and diminished ET-1 release. Lidocaine and mepivacaine are more effective in reducing PAP and edema formation, but long-acting local anesthetics also inhibit ET-1 depletion and therefore have increased anti-inflammatory properties.

[Co-analgesics--today and tomorrow--a receptor-based overview of therapeutical options]. / Co-Analgetika--heute und morgen--Eine rezeptorbasierte Ubersicht analgetischer Therapieoptionen.

The sensation of pain arises through stimulation of peripheral nociceptors and is transmitted centrally involving several receptors and ion channels. In addition many endogenous physiologic pain-modulating mechanisms exist. Besides of classical analgesics, numerous other drugs showed analgesic properties based on diverse modes of actions along the pain pathway. These co-analgesics, administered in combination with classical drugs, are able to reduce painful states of different origin. We describe the peripheral action sites of co-analgesics, such as cannabinoids, capsaicin, bisphosphonates, steroids and somatostatin. We also summarise the effect of peripherally and centrally acting ion-channel blockers, e.g. local anaesthetics, carbamazepine and tolperisone working on sodium channels and gabapentin and pregabalin working on calcium channels. Finally, central analgesic mechanisms are discussed, for instance the inhibition of NMDA-receptors by ketamine or magnesium, the stimulation of alpha2-receptors by clonidine, tizanidine or antidepressants, the activation of GABA-receptors through baclofen and other analgesic mechanisms of i.e. ondansetron and neostigmine.

Painful and nonpainful phantom and stump sensations in acute traumatic amputees.

BACKGROUND: The formation, prevalence, intensity, course, and predisposing factors of phantom limb pain were investigated to determine possible mechanisms of the origin of phantom limb pain in traumatic upper limb amputees. METHODS: Ninety-six upper limb amputees participated in the study. A questionnaire assessed the following question: side, date, extension, and cause of amputation; preamputation pain; and presence or absence of phantom pain, phantom and stump sensations or stump pain or both. RESULTS: The response rate was 84%. Sixty-five (81%) participants returned the questionnaire. In 64 (98.5%) participants a traumatic injury led to amputation; the amputation was necessary because of infection in one patient (1.5%). The median follow-up time (from amputation to evaluation) was 3.2 years (range, 0.9-3.8 years) The prevalence of phantom pain was 44.6%, phantom sensation 53.8%, stump pain 61.5%, and stump sensation 78.5%. After its first appearance, phantom pain had a decreasing course in 14 (48.2%) of 29 amputees, was stable in 11 (37.9%) amputees, and worsened in 2 (6.9%) of 29 amputees. Stump pain had a decreasing course in 19 (47.5%) of 40 amputees but was stable in 12 (30%) amputees. Phantom pain occurred immediately after amputation in 8 (28%) of 29 amputees between 1 month and 12 months in 3 (10%) amputees and after 12 or more months in 12 (41%) amputees. CONCLUSION: Stump pain and stump sensation predominate traumatic amputees' somatosensory experience immediately after amputation; phantom pain and phantom sensations are often long-term consequences of amputation. Amputees experience phantom sensations and phantom pain within 1 month after amputation, a second peak occurs 12 months after amputation. Revised diagnostic criteria for phantom pain are proposed on the basis of these data.

Functional Characterization of At-Level Hypersensitivity in Patients With Spinal Cord Injury.

At-level and above-level hypersensitivity was assessed in patients with chronic complete thoracic spinal cord injury (SCI). Patients were classified using somatosensory mapping (brush, cold, pinprick) and assigned into 2 groups (ie, patients with at-level hypersensitivity [SCIHs, n = 8] and without at-level hypersensitivity [SCINHs, n = 7]). Gender and age-matched healthy subjects served as controls. Quantitative sensory testing (QST), electrically- and histamine-induced pain and itch, laser Doppler imaging, and laser-evoked potentials (LEP) were recorded at-level and above-level in SCI-patients. Six of 8 SCIHs, but 0 of 7 SCINHs patients suffered from neuropathic below-level pain. Clinical sensory mapping revealed spreading of hypersensitivity to more cranial areas (above-level) in 3 SCIHs. Cold pain threshold measures confirmed clinical hypersensitivity at-level in SCIHs. At-level and above-level hypersensitivity to electrical stimulation did not differ significantly between SCIHs and SCINHs. Mechanical allodynia, cold, and pin-prick hypersensitivity did not relate to impaired sensory function (QST), axon reflex flare, or LEPs. Clinically assessed at-level hypersensitivity was linked to below-level neuropathic pain, suggesting neuronal hyperexcitability contributes to the development of neuropathic pain. However, electrically evoked pain was not significantly different between SCI patients. Thus, SCI-induced enhanced excitability of nociceptive processing does not necessarily lead to neuropathic pain. QST and LEP revealed no crucial role of deafferentation for hypersensitivity development after SCI. PERSPECTIVE: At-level hypersensitivity after complete thoracic SCI is associated with neuropathic below-level pain if evoked by clinical sensory stimuli. QST, LEP, and electrically-induced axon reflex flare sizes did not indicate somatosensory deafferentation in SCIHs.

Sensitization and habituation of AMH and C-fiber related percepts of repetitive radiant heat stimulation.

OBJECTIVE: Pain perception involves neuronal plasticity at peripheral and central stages, resulting in sensitization or habituation, depending on intensity and temporal features of stimulation. Concurrent assessment of perceptual change over different time spans is therefore important for understanding the dynamics of pain processing. METHODS: A new psychophysical procedure was established to assess sensitization and habituation during repetitive radiant heat stimulation. Short-term perceptual change (<1 min) during trials with 10 stimuli applied at 3 frequencies (0.2-0.6-1.8 Hz) and 3 intensities was assessed for AMH-II or C-fiber related percepts. Perceptual changes were monitored for medium-term (1-15 min) and for long-term (15-90 min) time spans. RESULTS: Short-term sensitization occurred only at frequencies above 0.3 Hz and was affected by both stimulus frequency and intensity, but the AMH-fiber related sensitization depended on intensity only above 0.6 Hz. Multiple stimulation of the same skin area during medium-term time spans resulted in habituation. No long-term perceptual changes occurred. CONCLUSIONS: The procedure permits concurrent assessment of short-term sensitization and medium-term habituation, assumed to be related to spinal windup and cutaneous nociceptive fiber fatigue, respectively. SIGNIFICANCE: The method is suitable for quantitative sensory testing of dynamic pain processing over different time spans, relevant in clinical testing of pain and in drug assessment.

Delta-9-THC based monotherapy in fibromyalgia patients on experimentally induced pain, axon reflex flare, and pain relief.

OBJECTIVE: Fibromyalgia (FM) is a chronic pain syndrome characterized by a distinct mechanical hyperalgesia and chronic pain. Recently, cannabinoids have been demonstrated as providing anti-nociceptive and anti-hyperalgesic effects in animal and human studies. Here, we explored in nine FM patients the efficacy of orally administered delta-9-tetrahydrocannabinol (THC) on electrically induced pain, axon reflex flare, and psychometric variables. RESEARCH DESIGN AND METHODS: Patients received a daily dose of 2.5-15 mg of delta-9-THC, with a weekly increase of 2.5 mg, as long as no side effects were reported. Psychometric variables were assessed each week by means of the West Haven-Yale Multidimensional Pain Inventory (MPI), Pittsburgh Sleep Quality Index (PSQI), Medical outcome survey-short form (MOS SF-36), the Pain Disability Index (PDI), and the Fibromyalgia Impact Questionnaire (FIQ). In addition, patients recorded daily, in a diary, their overall pain intensity on a numeric scale. Each week, pain and axon reflex flare was evoked experimentally by administration of high intensity constant current pulses (1 Hz, pulse width 0.2 ms, current increase stepwise from 2.5-12.5 mA every 3 minutes) delivered via small surface electrodes, attached to the volar forearm skin. MAIN OUTCOME MEASURES: Daily pain recordings by the patient, experimentally induced pain, and axon reflex flare recorded by a laser Doppler scanner. RESULTS: Five of nine FM patients withdrew during the study due to adverse side effects. Delta-9-THC had no effect on the axon reflex flare, whereas electrically induced pain was significantly attenuated after doses of 10-15 mg delta-9-THC (p < 0.05). Daily-recorded pain of the FM patients was significantly reduced (p < 0.01). CONCLUSIONS: This pilot study demonstrated that a generalized statement that delta-9-THC is an analgetic drug cannot be made. However, a sub-population of FM patients reported significant benefit from the delta-9-THC monotherapy. The unaffected electrically induced axon reflex flare, but decreased pain perception, suggests a central mode of action of the cannabinoid.

Reduction of pulmonary edema by short-acting local anesthetics.

BACKGROUND AND OBJECTIVES: Local anesthetics (LAs) possess a variety of effects that cannot be explained by the typical block of neuronal sodium channels. Antithrombotic effects of LAs are well known, but LAs also act as bactericides. Therefore, an investigation of the influence of LAs on the inflammatory response of the isolated rat lung (n = 78) to an N-formyl-l-leucin-methionyl-l-phenylalanine (FMLP) stimulus was performed. METHODS: The experiments were performed on isolated and ventilated rat lungs perfused with cell-free and plasma-free buffer. LAs (lidocaine and mepivacaine) were injected in various concentrations before application and activation of human granulocytes by FMLP. Pulmonary arterial pressure (PAP) and lung weight gain were monitored continuously. LAs in final dosages from 10(-2) to 10(-7) mg/kg body weight (n = 6 each) were injected into the pulmonary artery before treatment with FMLP (10(-6) M) to induce pulmonary arterial hypertension. Perfusate samples were taken intermittently to determine thromboxane A(2) (TX A(2)) and endothelin-1 concentrations. Microscopic analyses were performed to assess the degree of lung injury. RESULTS: Pretreatment with LAs significantly reduced the FMLP-induced PAP increase (treatment group v sham group: 0.5 to 5 mm Hg v 8 mm Hg; P < .05) and the release of endothelin-1 (2.4 v 5 fmol/mL). Histologic damage seen as acute granulocytic alveolitis was reduced by lidocaine and mepivacaine, even below clinically relevant concentrations. CONCLUSION: LA pretreatment reduces inflammatory reactions after FMLP stimulus.

Duration of effects of aspirin on platelet function in healthy volunteers: an analysis using the PFA-100.

STUDY OBJECTIVE: The aim of the study was to determine the duration and effects of aspirin on platelet function. STUDY DESIGN: Prospective investigation. SETTING: Blood samples from volunteers. PATIENTS AND MONITORING: Ten healthy male volunteers took part in this investigation. After having measured baseline hemostatic parameters, 2000-mg aspirin was taken orally. Subsequently, the hemostatic profile had been compiled daily for a duration of 4 days after ingestion. MEASUREMENTS AND MAIN RESULTS: Platelet function was analyzed (1) after 3 hours and (2) daily for 4 days by the platelet function analyzer (PFA-100, Dade Co, Miami, Fla), which represents a sensitive investigation method for measuring platelet function and dysfunction. Routine hemostatic parameters were investigated. Three hours after ingestion of aspirin, abnormal PFA-100 values could be detected. Further detectable elevated values were found during the following 3 days. CONCLUSION: Effects of single-dose aspirin 2000 mg on platelet function were detected after 3 hours and had been lasting for the following 3 days. This result shows that PFA-100 may help by evaluating hemostasis during the preoperative period.

Ultrasound-guided carotid sheath block for carotid endarterectomy: a case series of the spread of injectate.

INTRODUCTION: We aimed to show the spread of local anesthetic following an ultrasound-guided, double-injection technique of a carotid sheath block before carotid endarterectomy. METHODS: The study included 15 patients scheduled for elective carotid endarterectomy. The carotid sheath block was performed after ultrasound-guided localization of the carotid bifurcation (level C4-C6) at the posterior border of the sternocleidomastoid muscle. A mix of 7.5 mL ropivacaine 0.75%, 7.5 mL prilocaine1% and 3 mL iopromidum was injected at the base of the carotid bifurcation. An additional 15 mL of the mixture was administered subcutaneously at the surgical incision line. Thirty minutes after the block, a computed tomography scan of the head, neck region and upper thorax was performed to reconstruct a 3-D distribution of the injectate. RESULTS: All patients achieved C2-C4 dermatomal sensory blockade. None required conversion to general anesthesia. The injectate spread ranged from the vertebral body of C1 to the vertebral body of T3. The mean volume of distribution was 97±13 mL, the craniocaudal spread 138±19 mm, dorsoventral 57±8 mm and coronal 53±8 mm. The mean carotid artery circumference contact was 252°±77, with four patients (27%) presenting with a ring formation (360°) around the carotid artery. CONCLUSIONS: Ultrasound-guided carotid sheath block provided an extensive spread of local anesthetic. A complete ring formation of local anesthetic around the artery does not seem necessary for a successful anesthesia. The resulting nerve blockade thus appears sufficient for surgery, with minor risks compared to blind methods.