Dnmt3a deficiency in the skin causes focal, canonical DNA hypomethylation and a cellular proliferation phenotype.

DNA hypomethylation is a feature of epidermal cells from aged and sun-exposed skin, but the mechanisms responsible for this methylation loss are not known. Dnmt3a is the dominant de novo DNA methyltransferase in the skin; while epidermal Dnmt3a deficiency creates a premalignant state in which keratinocytes are more easily transformed by topical mutagens, the conditions responsible for this increased susceptibility to transformation are not well understood. Using whole genome bisulfite sequencing, we identified a focal, canonical DNA hypomethylation phenotype in the epidermal cells of Dnmt3a-deficient mice. Single-cell transcriptomic analysis revealed an increased proportion of cells with a proliferative gene expression signature, while other populations in the skin were relatively unchanged. Although total DNMT3A deficiency has not been described in human disease states, rare patients with an overgrowth syndrome associated with behavioral abnormalities and an increased risk of cancer often have heterozygous, germline mutations in DNMT3A that reduce its function (Tatton-Brown Rahman syndrome [TBRS]). We evaluated the DNA methylation phenotype of the skin from a TBRS patient with a germline DNMT3AR882H mutation, which encodes a dominant-negative protein that reduces its methyltransferase function by ∼80%. We detected a focal, canonical hypomethylation phenotype that revealed considerable overlap with hypomethylated regions found in Dnmt3a-deficient mouse skin. Together, these data suggest that DNMT3A loss creates a premalignant epigenetic state associated with a hyperproliferative phenotype in the skin and further suggest that DNMT3A acts as a tumor suppressor in the skin.

Factors Associated With Desaturation in Prehospital Rapid Sequence Intubation in a Helicopter Emergency Medical Service.

OBJECTIVE: Desaturation during prehospital rapid sequence intubation (RSI) is common and is associated with patient morbidity. Past studies have identified oxygen saturations at induction, the grade of laryngoscopy, and multiple attempts to intubate as being associated with desaturation. This study aimed to investigate whether there are other factors, identifiable before RSI, associated with desaturation. METHODS: This was a study of a physician-paramedic critical care team operating as Aeromedical Operations, NSW Ambulance. Prehospital RSIs (using paralysis) were studied retrospectively via patient case notes, monitor data, and an airway database. The review occurred between April 1, 2016, and December 31, 2018. Desaturation was defined as monitor recordings of saturations ≤ 92%. Logistic regression was performed for factors likely to be associated with desaturation. RESULTS: Desaturation occurred in 67 of 350 (19.1%) RSIs. Factors significantly associated with desaturation included male sex, a chest injury, increased weight, and lower saturations pre-RSI. CONCLUSION: Increased weight, chest injuries, and lower oxygen saturations are associated with desaturation at RSI. The variable male sex may be a surrogate for other as-yet unidentified factors.

The effect of ketamine and fentanyl on haemodynamics during intubation in pre-hospital and retrieval medicine.

BACKGROUND: Ketamine use for rapid sequence intubation (RSI) is frequent in pre-hospital and retrieval medicine (PHARM) and is associated with potentially deleterious haemodynamic changes, which may be ameliorated by concurrent use of fentanyl. OBJECTIVES: To describe the frequency with which fentanyl is used in conjunction with ketamine in a system where its use is discretionary, and to explore any observed changes in haemodynamics with its use. METHODS: A retrospective observational study of over 800 patients undergoing RSI with ketamine ± fentanyl in the PHARM setting between 2015 and 2019. The primary outcome was the proportion of patients in each group who had a systolic blood pressure (SBP) outside a pre-specified target range, with adjustment for baseline abnormality, within 10 min of anaesthetic induction. RESULTS: Eight hundred and seventy-six patients were anaesthetised with ketamine, of whom 804 were included in the analysis. 669 (83%, 95% CI 80%-86%) received ketamine alone, and 135 (17%, 95% CI 14%-20%) received both fentanyl and ketamine. Median fentanyl dose was 1.1 mcg/kg (IQR 0.75-1.5 mcg/kg). Systolic blood pressure (SBP) at induction was consistently associated with SBP after intubation in multivariable logistic regression, but fentanyl use was not associated with a change in odds of meeting the primary outcome (OR 1.08; 95% CI 0.72-1.60), becoming hypertensive (OR 1.35; 95% CI 0.88-2.07) or hypotensive (OR 0.76; 95% CI 0.47-1.21). CONCLUSIONS: The addition of fentanyl to ketamine for RSI was not associated with an alteration of the odds of post-induction haemodynamic stability, although the doses used were low. These findings justify further study into the optimal dosing of fentanyl during RSI in pre-hospital and retrieval medicine.