Small‐Conductance Calcium‐Activated Potassium Current in Normal Rabbit Cardiac Purkinje Cells

Background: Purkinje cells (PCs) are important in cardiac arrhythmogenesis. Whether small‐conductance calcium‐activated potassium (SK) channels are present in PCs remains unclear. We tested the hypotheses that subtype 2 SK (SK2) channel proteins and apamin‐sensitive SK currents are abundantly present in PCs. Methods and Results: We studied 25 normal rabbit ventricles, including 13 patch‐clamp studies, 4 for Western blotting, and 8 for immunohistochemical staining. Transmembrane action potentials were recorded in current‐clamp mode using the perforated‐patch technique. For PCs, the apamin (100 nmol/L) significantly prolonged action potential duration measured to 80% repolarization by an average of 10.4 ms (95% CI, 0.11–20.72) (n=9, P=0.047). Voltage‐clamp study showed that apamin‐sensitive SK current density was significantly larger in PCs compared with ventricular myocytes at potentials ≥0 mV. Western blotting of SK2 expression showed that the SK2 protein expression in the midmyocardium was 58% (P=0.028) and the epicardium was 50% (P=0.018) of that in the pseudotendons. Immunostaining of SK2 protein showed that PCs stained stronger than ventricular myocytes. Confocal microscope study showed SK2 protein was distributed to the periphery of the PCs. Conclusions: SK2 proteins are more abundantly present in the PCs than in the ventricular myocytes of normal rabbit ventricles. Apamin‐sensitive SK current is important in ventricular repolarization of normal PCs

Multicenter assessment of cryoanalgesia use in minimally invasive repair of pectus excavatum: A 20-center retrospective cohort study

Objective: To assess the clinical implications of cryoanalgesia for pain management in children undergoing minimally invasive repair of pectus excavatum (MIRPE).Background: MIRPE entails significant pain management challenges, often requiring high postoperative opioid use. Cryoanalgesia, which blocks pain signals by temporarily ablating intercostal nerves, has been recently utilized as an analgesic adjunct. We hypothesized that the use of cryoanalgesia during MIRPE would decrease postoperative opioid use and length of stay (LOS).Materials and methods: A multicenter retrospective cohort study of 20 US children\u27s hospitals was conducted of children (age below 18 years) undergoing MIRPE from January 1, 2014, to August 1, 2019. Differences in total postoperative, inpatient, oral morphine equivalents per kilogram, and 30-day LOS between patients who received cryoanalgesia versus those who did not were assessed using bivariate and multivariable analysis. P value \u3c0.05 is considered significant.Results: Of 898 patients, 136 (15%) received cryoanalgesia. Groups were similar by age, sex, body mass index, comorbidities, and Haller index. Receipt of cryoanalgesia was associated with lower oral morphine equivalents per kilogram (risk ratio=0.43, 95% confidence interval: 0.33-0.57) and a shorter LOS (risk ratio=0.66, 95% confidence interval: 0.50-0.87). Complications were similar between groups (29.8% vs 22.1, P=0.07), including a similar rate of emergency department visit, readmission, and/or reoperation.Conclusions: Use of cryoanalgesia during MIRPE appears to be effective in lowering postoperative opioid requirements and LOS without increasing complication rates. With the exception of preoperative gabapentin, other adjuncts appear to increase and/or be ineffective at reducing opioid utilization. Cryoanalgesia should be considered for patients undergoing this surgery