Internal deformation of the human crystalline lens during accommodation

Purpose: To describe the internal deformations in the crystalline lens that occur during accommodation. Methods: A computer‐based mechanical model of accommodation was created using the finite element method. The lens geometry of the model was based on in vivo measurements of human lenses in the accommodated state. The mechanical properties of the lens were based on ex vivo measurements of human lenses. To achieve a state of disaccommodation, the lens equator was stretched by 7%. The internal strains and displacements were calculated for a young accommodating lens, a lens of pre‐presbyopic age and a lens of presbyopic age (20, 40 and 60 years old, respectively). Results: The model showed that the radial strain was maximal in the nucleus for the young accommodating lens and minimal in the nucleus for the oldest non‐accommodating lens. In the young lens the deformations occurred throughout the entire lens, whereas in the older non‐accommodating lens the deformations were concentrated in the equatorial region. Conclusions: The model predicted that during accommodation, changes in lens thickness are mainly caused by deformation of the nucleus. In the older, non‐accommodating lens, the deformations occur predominantly in the equatorial region and do not affect the central curvatures of the lens.     

Early Reversal of Profound Rocuronium-induced Neuromuscular Blockade by Sugammadex in a Randomized Multicenter Study: Efficacy, Safety, and Pharmacokinetics

Background: Sugammadex reverses the neuromuscular blocking effects of rocuronium by chemical encapsulation. The efficacy, safety, and pharmacokinetics of sugammadex for reversal of profound rocuronium-induced neuromuscular blockade were evaluated.

Methods: Ninety-eight male adult patients were randomly assigned to receive sugammadex (1, 2, 4, 6, or 8 mg/kg) or placebo at 3, 5, or 15 min after 0.6 mg/kg rocuronium. Patients were anesthetized with propofol and fentanyl. The primary endpoint of the study was the time to achieve a recovery of train-of-four ratio to 0.9. Neuromuscular blockade was measured using acceleromyography. Concentrations of rocuronium and sugammadex were determined in venous blood and urine samples. A population pharmacokinetic model using NONMEM (GloboMax LLC, Hanover, MD) was applied.

Results: The mean time to recovery of the train-of-four ratio to 0.9 after dosing at 3, 5, and 15 min decreased from 52.1, 51.7, and 35.6 min, respectively, after administration of placebo to 1.8, 1.5, and 1.4 min, respectively, after 8 mg/kg sugammadex. Sugammadex was safe and well tolerated. However, 20.4% of patients showed signs of inadequate anesthesia after its administration. The median cumulative excretion of rocuronium in the urine over 24 h was 26% in the placebo group and increased to 58-74% after 4-8 mg/kg sugammadex. The mean plasma clearances of sugammadex and rocuronium were 0.084 and 0.26 l/min, respectively.     

Results of early curettage of giant congenital melanocytic nevi; a report of eight cases and review of the literature

The aim of this study was to investigate the long-term cosmetic and oncologic results following early curettage of giant congenital melanocytic nevi (GCMN). Neonates with GCMN treated with curettage within 4 weeks of age and with a minimum follow-up of 2 years were evaluated at the outpatient department. Scar formation was evaluated by means of the patient and observer scar assessment scale (POSAS). Biopsy specimens were analysed. In 9 years, eight neonates were treated. The mean follow-up period was 5.6 years. Six (75%) patients developed re-pigmentation of the curetted skin, hypertrichosis returned in five cases. One patient developed hypertrophic scars, all others formed good scars. None of the patients developed a melanoma. Biopsy specimens showed nevus cells in the skin after curettage. In 50% of the patients curettage is followed by severe re-pigmentation. Since this treatment does not remove all nevus cells, long-term follow-up is essential to detect malignant transformation.     

COVID-19 and the ethics of human challenge trials

Medicine, Health Care and Philosophy -