The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AIM: The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery. METHODS: This was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin. RESULTS: Overall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P < 0.001). After adjustment, delay was not associated with a lower rate of complete resection (OR 1.18, 95% CI 0.90-1.55, P = 0.224), which was consistent in elective patients only (OR 0.94, 95% CI 0.69-1.27, P = 0.672). Longer delays were not associated with poorer outcomes. CONCLUSION: One in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease

Intraperitoneal drain placement and outcomes after elective colorectal surgery: international matched, prospective, cohort study

Despite current guidelines, intraperitoneal drain placement after elective colorectal surgery remains widespread. Drains were not associated with earlier detection of intraperitoneal collections, but were associated with prolonged hospital stay and increased risk of surgical-site infections.Background Many surgeons routinely place intraperitoneal drains after elective colorectal surgery. However, enhanced recovery after surgery guidelines recommend against their routine use owing to a lack of clear clinical benefit. This study aimed to describe international variation in intraperitoneal drain placement and the safety of this practice. Methods COMPASS (COMPlicAted intra-abdominal collectionS after colorectal Surgery) was a prospective, international, cohort study which enrolled consecutive adults undergoing elective colorectal surgery (February to March 2020). The primary outcome was the rate of intraperitoneal drain placement. Secondary outcomes included: rate and time to diagnosis of postoperative intraperitoneal collections; rate of surgical site infections (SSIs); time to discharge; and 30-day major postoperative complications (Clavien-Dindo grade at least III). After propensity score matching, multivariable logistic regression and Cox proportional hazards regression were used to estimate the independent association of the secondary outcomes with drain placement. Results Overall, 1805 patients from 22 countries were included (798 women, 44.2 per cent; median age 67.0 years). The drain insertion rate was 51.9 per cent (937 patients). After matching, drains were not associated with reduced rates (odds ratio (OR) 1.33, 95 per cent c.i. 0.79 to 2.23; P = 0.287) or earlier detection (hazard ratio (HR) 0.87, 0.33 to 2.31; P = 0.780) of collections. Although not associated with worse major postoperative complications (OR 1.09, 0.68 to 1.75; P = 0.709), drains were associated with delayed hospital discharge (HR 0.58, 0.52 to 0.66; P &lt; 0.001) and an increased risk of SSIs (OR 2.47, 1.50 to 4.05; P &lt; 0.001). Conclusion Intraperitoneal drain placement after elective colorectal surgery is not associated with earlier detection of postoperative collections, but prolongs hospital stay and increases SSI risk

Poisson structure for hyperbolic heat conduction

We use the method of extending the space of macroscopic variables (Gambar and Markus, 1994) to construct a Hamilton-Lagrange scheme for hyperbolic transport. Specifically, we propose a Lagrangian density to obtain the telegraphist type equations as the Euler-Lagrange equation of a Hamilton variational principle. Two evolution equations for the components of a conjugated variables space are obtained from the modified Hamilton principle. These equations are particular cases of a more general time evolution equations which contains a Poisson bracket with the Hamiltonian density as the movement generator. The bracket satisfies the Jacobi's identity giving us a Poisson structure for the problem. We discuss some aspects of the time evolution of fluctuations ot the temperature in a rigid heat conductor solid

NONEQUILIBRIUM VARIATIONAL PRINCIPLE FOR THE TIME EVOLUTION OF AN IONIZED-GAS

A restricted variational formulation for extended irreversible thermodynamics is proposed. Then, it is applied to a heat- and electricity-conducting viscous fluid, and the resulting equations are reduced to order two to be compared with those well known of kinetic theory. A better understanding of the phenomenological coefficients than in previous reported works is obtained

Influence of surface coverage on the effective optical properties of porous silicon modeled as a Si-wire array

The effective dielectric function, effective absorption coefficient and effective refractive index for a model of porous silicon (PS) are calculated using the volume and surface averaging method. The model consists of periodic Si wires with different surface coverages. This approach allows to obtain analytical results within certain approximations. The method uses experimental parameters to characterize the bulk and the surface. We choose the bulk c-Si, and cover it with three different possible surface skins: siloxanes, a-Si:H and SiO2. The results are compared with PS experimental data and other theoretical approaches for silicon wires. We obtain good agreement for certain coatings. Our results emphasize the important role of surface coatings in the effective response of porous silicon. (C) 1997 American Institute of Physics

NON-LINEAR HEAT WAVES IN EXTENDED IRREVERSIBLE THERMODYNAMICS

A variational approach to nonlinear heat waves in solids within extended irreversible thermodynamics is presented. The formalism gives a nonlinear in time evolution equation for the heat flux in a rigid solid which, together with the energy balance, describes in closed form the nonequilibrium processes which occur in a time scale comparable to the relaxation time of the heat flux. Well known results of heat transport are recovered in the appropriate limits by the structure of the equation which also allows for couplings not considered up until now whose consequences remain to be assessed

Fluctuations far from equilibrium: Hyperbolic transport

The problem of the statistical properties of fluctuations in systems far from equilibrium is addressed. The discussion is based on a variational approach to hyperbolic transport equations built in a space spanned by the usual thermodynamic properties plus a set of potential functions associated with them. The enlarged space characterizes the far from equilibrium states of the system and fluctuations in the potential functions satisfy the Chapman-Kolmogorov equation. Well known results on processes near equilibrium are recovered in the parabolic transport limit

Effective conductivity of chemically deposited ZnO thin films

Chemically deposited thin films have multiple applications. However, as a result of their complex structure, their physical properties are very difficult to predict. In this paper, we use an effective medium approach to model these heterogeneous systems. We extend Thorpe's formula for the effective electrical conductivity of elliptical holes randomly distributed in a matrix to a system composed of conducting ellipses in a conducting matrix. This extension is used to calculate the effective electrical conductivity of polycrystalline chemically deposited ZnO thin films. We compare experimental results obtained by two different deposition methods: spray pyrolysis and successive ion layer adsorption and reaction (SILAR) reported here. We select the elliptical geometric parameters from microstructural data. Good agreement between the experimental measurements and our calculation is obtained. In addition, we present a new proof of the reciprocity theorem used to derive the theoretical relation

Comments on the existence of Hamiltonian principles for non-selfadjoint operators

The thermodynamic transport equations contain the first time derivative, a non self-adjoint operator, which makes it impossible to derive them from Hamilton's variational principle. However, introducing new basic fields which generate measurable properties in the same way as the potentials in other held theories, the complete Hamilton Lagrange formalism may be established. This fact ostensibly surpasses Finlayson's work where special restrictions for classical variational principles are given. We point out that although these restrictions seem to preclude the construction of a variational scheme for the transport equations, a correct interpretation of these facts permits to solve this apparent paradox. The Onsager reciprocal relations play a central role in the compatibility between these two apparent opposite views

ON THE CONTRIBUTION OF THE MEXICAN SCHOOL TO EXTENDED IRREVERSIBLE THERMODYNAMICS

The postulates and methodology of the version of extended irreversible thermodynamics developed in Mexico are presented. Mention is made of the main features which make it different from other existing versions. The ionized gas modeled as a binary mixture is discussed to illustrate the approach. Some limitations and perspectives are also pointed out