An observational study to identify the prevalence of thrombocytopenia and anti-PF4/polyanion antibodies in Norwegian health care workers after COVID-19 vaccination.

BACKGROUND: The COVID-19 vaccine from AstraZeneca (AZD1222) is one of several vaccines introduced to provide immunity against SARS-CoV-2. Recently, more than 50 cases have been reported presenting a combination of thrombosis, thrombocytopenia, and remarkably high levels of anti-platelet factor 4 (PF4)/polyanion antibodies post-AZD1222 vaccination. Now linked to the vaccine, the condition is referred to as vaccine-induced immune thrombotic thrombocytopenia. The European Medicines Agency still recommends vaccination with AZD1222, but several European countries have temporally paused and/or restricted its use because of the perceived risk of this severe side effect. Because there is no description of PF4/polyanion antibody testing in the clinical trials, knowledge about the prevalence of such antibodies in a vaccinated cohort is needed. OBJECTIVES: To investigate prevalence of thrombocytopenia and anti-PF4/polyanion antibodies in a population recently vaccinated with AZD1222. PATIENTS/METHODS: Four hundred and ninety-two health care workers recently vaccinated with the first dose of AZD1222 were recruited from two hospitals in Norway. Study individuals were screened for thrombocytopenia and the presence of anti-PF4/polyanion antibodies with a PF4/PVS immunoassay. Side effects after vaccination were registered. RESULTS: The majority of study participants had normal platelet counts and negative immunoassay. Anti-PF4/polyanion antibodies without platelet activating properties were only detected in six individuals (optical density ≥0.4, range 0.58-1.16), all with normal platelet counts. No subjects had severe thrombocytopenia. CONCLUSIONS: We found low prevalence of both thrombocytopenia and antibodies to PF4/polyanion-complexes among Norwegian health care workers after vaccination with AZD1222.

Electrical nerve stimulation or ultrasound guidance for lateral sagittal infraclavicular blocks: a randomized, controlled, observer-blinded, comparative study.

BACKGROUND: Ultrasound guidance is frequently used to perform infraclavicular brachial plexus blocks. In this study, we compared electrical nerve stimulation and ultrasound guidance for the lateral sagittal infraclavicular block. METHODS: Eighty patients, ASA 1-2, were randomized for either nerve stimulation (group NS) or ultrasound-guided blocks (group US). The brachial plexus was anesthetized with 0.6 mL/kg mepivacaine (15 mg/mL) with epinephrine (2.5 microg/mL) in both groups. For ultrasound-guided blocks, local anesthetic was injected cranioposterior to the axillary artery. An observer who was blinded for the method assessed the blocks and questioned the patients. Successful block was defined as analgesia or anesthesia of all five nerves distal to the elbow. The main outcome variables were the time until readiness for surgery, quantified discomfort during the block, and pain related to tourniquet ischemia on a numeric rating scale (0-10). RESULTS: Block performance time was 4.3 min (sd 1.3) and 4.1 min (sd 1.3) (P = 0.64) in group NS and group US, respectively. Onset time for sensory block was 13.7 min (sd 6.6) and 13.9 min (sd 5.8), (P = 0.99). The time until readiness for surgery was 18.1 min in both groups (sd 6.6 and 6.0) (P = 0.99). Median discomfort related to the block procedure was 1 in both groups (P = 0.92), and median tourniquet pain was 0.5 in group NS and 1 in group US (P = 32). Differences in success rates, between 85% in group NS and 95% in group US, were not significant (P = 0.26). CONCLUSIONS: We conclude that favorable results can be obtained when either nerve stimulation or ultrasound guidance is used for lateral sagittal infraclavicular block. Using ultrasound, local anesthetic injection cranioposterior to the artery appears feasible.