Persistence in a large network of sparsely interacting neurons.

This article presents a biological neural network model driven by inhomogeneous Poisson processes accounting for the intrinsic randomness of synapses. The main novelty is the introduction of sparse interactions: each firing neuron triggers an instantaneous increase in electric potential to a fixed number of randomly chosen neurons. We prove that, as the number of neurons approaches infinity, the finite network converges to a nonlinear mean-field process characterised by a jump-type stochastic differential equation. We show that this process displays a phase transition: the activity of a typical neuron in the infinite network either rapidly dies out, or persists forever, depending on the global parameters describing the intensity of interconnection. This provides a way to understand the emergence of persistent activity triggered by weak input signals in large neural networks.

The impact of perioperative hypothermia on plastic surgery outcomes: a multivariate logistic regression of 1062 cases.

BACKGROUND: Perioperative hypothermia has been associated with increased rates of infection, prolonged recovery time, and coagulopathy. OBJECTIVES: The authors assessed the impact of hypothermia on patient outcomes after plastic surgery and analyzed the impact of prewarming on postoperative outcomes. METHODS: The medical charts of 1062 patients who underwent complex plastic surgery typically lasting at least 1 hour were reviewed. Hypothermia was defined as a temperature at or below 36°C. Postoperative complication data were collected for outcomes including infection, delayed wound healing, seroma, hematoma, dehiscence, deep venous thrombosis, and overall wound problems. Odds ratios (ORs) were estimated from 3 multivariate logistic regression models of hypothermia and one model of body contouring procedures that included prewarming as a parameter. RESULTS: Perioperative hypothermia was not a significant predictor of wound problems (OR = 0.83; P = .28). In the stratified regression model, hypothermia did not significantly impact wound problems. The regression model measuring the interaction between hypothermia and operating time did not show a significantly increased risk of wound problems. Prewarming did not significantly affect perioperative hypothermia (P = .510), and in the model of body contouring procedures with prewarming as a categorical variable, massive weight loss was the most significant predictor of wound complications (OR = 2.57; P = .003). Prewarming did not significantly affect outcomes (OR = 1.49; P = .212). CONCLUSIONS: Based on univariate and multivariate models in our study, mild perioperative hypothermia appears to be independent of wound complications. LEVEL OF EVIDENCE 4: Risk.

Barbed sutures and wound complications in plastic surgery: an analysis of outcomes.

BACKGROUND: Barbed sutures may expedite dermal approximation and improve tissue support while requiring less time and material than conventional sutures. Several types of barbed sutures are available, each with unique advantages. OBJECTIVES: The authors sought to determine whether the incidence of complications differed after wound approximation in plastic surgery when various brands of barbed vs nonbarbed traditional sutures were employed. METHODS: The authors conducted a retrospective review of outcomes in body contouring, free flap, and breast reconstruction. Suture type and closure method were noted for each case. The number of complications after traditional 2-layer closure with nonbarbed sutures was compared with the number of complications after closure via 1- and 2-layer techniques with several brands of barbed sutures, and the brands of barbed sutures were compared with each other. RESULTS: A total of 1011 unique surgical procedures, including 298 procedures with barbed sutures and 713 procedures with nonbarbed sutures, were performed by 5 members of the plastic surgery faculty. The 2-layer technique with barbed sutures was associated with significantly higher rates of wound separation than traditional methods. Excessive erythema along the incision site was significantly more frequent with Quill barbed sutures than with V-Loc barbed sutures. CONCLUSIONS: Barbed sutures were associated with significantly higher rates of minor wound complications, specifically when the 2-layer closure technique was performed. Significantly higher rates of erythema were associated with Quill barbed sutures than with V-Loc barbed sutures. LEVEL OF EVIDENCE 4: Risk.

Effectiveness of prophylactic antibiotics in outpatient plastic surgery.

BACKGROUND: The effectiveness of prophylactic antibiotics has not been established for patients who undergo plastic surgery as outpatients, and consensus guidelines for antibiotic administration in clean-contaminated plastic surgery are not available. OBJECTIVES: In a retrospective study of outpatients, the authors examined preoperative timing of prophylactic antibiotics, whether postoperative antibiotics were administered, and whether any correlations existed between these practices and surgical complications. METHODS: The medical records of 468 plastic surgery outpatients were reviewed. Collected data included preoperative antibiotic timing, postoperative antibiotic use, comorbidities, and complications. Rates of complications were calculated and compared with other data. RESULTS: All 468 patients received antibiotics preoperatively, but only 93 (19.9%) received them ≥1 hour before the initial incision. Antibiotics were administered 15 to 44 minutes before surgery in 217 patients (46.4%). There was no significant difference in complication rates between the 315 patients who received postoperative prophylactic antibiotics (16.2%) and the 153 who did not (20.9%). Comorbidities had no bearing on postoperative complications. CONCLUSIONS: Postoperative antibiotic prophylaxis may be unnecessary for outpatient plastic surgery patients. LEVEL OF EVIDENCE: 3.

Continuation versus discontinuation of renin-angiotensin system inhibitors in patients admitted to hospital with COVID-19: a prospective, randomised, open-label trial.

BACKGROUND: Biological considerations suggest that renin-angiotensin system inhibitors might influence the severity of COVID-19. We aimed to evaluate whether continuing versus discontinuing renin-angiotensin system inhibitors (angiotensin-converting enzyme inhibitors or angiotensin receptor blockers) affects outcomes in patients admitted to hospital with COVID-19. METHODS: The REPLACE COVID trial was a prospective, randomised, open-label trial done at 20 large referral hospitals in seven countries worldwide. Eligible participants were aged 18 years and older who were admitted to hospital with COVID-19 and were receiving a renin-angiotensin system inhibitor before admission. Individuals with contraindications to continuation or discontinuation of renin-angiotensin system inhibitor therapy were excluded. Participants were randomly assigned (1:1) to continuation or discontinuation of their renin-angiotensin system inhibitor using permuted block randomisation, with allocation concealed using a secure web-based randomisation system. The primary outcome was a global rank score in which participants were ranked across four hierarchical tiers incorporating time to death, duration of mechanical ventilation, time on renal replacement or vasopressor therapy, and multiorgan dysfunction during the hospitalisation. Primary analyses were done in the intention-to-treat population. The REPLACE COVID trial is registered with ClinicalTrials.gov, NCT04338009. FINDINGS: Between March 31 and Aug 20, 2020, 152 participants were enrolled and randomly assigned to either continue or discontinue renin-angiotensin system inhibitor therapy (continuation group n=75; discontinuation group n=77). Mean age of participants was 62 years (SD 12), 68 (45%) were female, mean body-mass index was 33 kg/m2 (SD 8), and 79 (52%) had diabetes. Compared with discontinuation of renin-angiotensin system inhibitors, continuation had no effect on the global rank score (median rank 73 [IQR 40-110] for continuation vs 81 [38-117] for discontinuation; ß-coefficient 8 [95% CI -13 to 29]). There were 16 (21%) of 75 participants in the continuation arm versus 14 (18%) of 77 in the discontinuation arm who required intensive care unit admission or invasive mechanical ventilation, and 11 (15%) of 75 participants in the continuation group versus ten (13%) of 77 in the discontinuation group died. 29 (39%) participants in the continuation group and 28 (36%) participants in the discontinuation group had at least one adverse event (χ2 test of adverse events between treatment groups p=0·77). There was no difference in blood pressure, serum potassium, or creatinine during follow-up across the two groups. INTERPRETATION: Consistent with international society recommendations, renin-angiotensin system inhibitors can be safely continued in patients admitted to hospital with COVID-19. FUNDING: REPLACE COVID Investigators, REPLACE COVID Trial Social Fundraising Campaign, and FastGrants.

An Assessment of Fine Surgical KnotTying.

OBJECTIVE: Operating room simulation exercises have been well established as an effective means of improving confidence, task engagement, and learning retention among surgical residents. We have established a cost-effective model and scoring system assessing resident skills to tie secure surgical knots with minimal tension. DESIGN: A circular grid divided into 18 segments was placed underlying an aluminum can. Trainees tie 20 surgical square knots scored for time and total knot length. Movement of the can outside the grid served as a scoring penalty. Recorded were time, length of the 20 knots, and number of segments exposed at exercise end. A score was developed to identify a progression of skills with PGY level. All outcomes were compared between classes using ANOVA. SETTING: Brown University/Rhode Island Hospital Department of Surgery. PARTICIPANTS: Surgical residents (PGY1-PGY5) and participating attending surgeons employed by Rhode Island Hospital. RESULTS: Knot length and exposed segments showed trends of improved scores with ascending PGY level. Only average time attained statistical significance. Overall scores improved with PGY level: Composite scores significantly improved when comparing PGY1 to PGY3, PGY5, and Attending surgeons (p = 0.016, 0.011, and 0.011, respectively). Time significantly improved when comparing PGY1 to PGY3 and Attending surgeons (77vs. 50 and 47 seconds, p = 0.019 and 0.022 respectively). Composite scores were not significantly different above PGY3. CONCLUSIONS: A low fidelity, high impact knot tying model has been developed to assess the ability to securely tie surgical knots while minimizing tension, with linear increases in scores that appear to plateau at the PGY3 level.