The importance of hematocrit for oxygen delivery and hemodynamics

Anemia is common in elderly patients undergoing surgery and in critical patients. A 72-year-old man submitted to a revision of hip replacement implant was diagnosed with tuberculosis, followed by pulmonary fibrosis, pulmonary heart disease and compensatory erythrocytosis. In the postoperative period, he got anemia which improved his clinical status. Anemia reduces viscosity, i.e. one of the components of vascular resistance to laminar (according to the law of Hagen-Poiseuille) and turbulent flows. In conditions of decreased hematocrit, shear thinning occurs more easily and in larger caliber vessels. Hemodiluition reduces both right and left cardiac afterloads, thus provoking an improvement of the blood flow. As the hematocrit decreases, oxygen delivery increases, because the increase in the cardiac output is greater than the decrease in the concentration of hemoglobin. Further studies are needed to confirm this physical model and to establish the variable and degree of the transfusion trigger

Stress Hyperglycemia and Complications Following Traumatic Injuries in Individuals With/Without Diabetes: The Case of Orthopedic Surgery

Purpose: Hyperglycemia in trauma patients may stem from metabolic response to stress, both in the presence and the absence of underlying diabetes. We aimed to test the association of stress hyperglycemia with risks of adverse events subjects undergoing orthopedic surgery. Patients and Methods: In a prospective observational study, we enrolled 202 consecutive patients with hyperglycemia at hospital admission for trauma injuries requiring orthopedic surgery. Based on history, diabetes was present in 183, and 13 more were defined as unknown diabetes on the basis of HbA1c ≥48mmol/mol. Stress hyperglycemia was defined in subjects with/without diabetes by a stress hyperglycemia ratio (SHR) >1.14, calculated as admission glucose/average glucose, estimated from glycosylated hemoglobin. Logistic regression analysis was used to calculate the risk of post-surgery adverse events associated with different states of hyperglycemia, after correction for demographic and clinical confounders. Results: Stress hyperglycemia was diagnosed, either as superimposed to diabetes (54/196 cases, 27.6%) as well as in the 6 cases without diabetes. At least one complication was recorded in 68 cases (33.7%), the most common being systemic infection (22.8% of cases). In the total cohort, stress hyperglycemia, irrespective of the presence of diabetes, increased the risk of adverse events (any events, odds ratio [OR], 4.43; 95% confidence interval [CI], 2.11–9.30), cardiovascular events (OR, 7.09; 95% CI, 2.47–19.91), systemic infections (OR, 4.21; 95% CI, 1.97–9.03) and other adverse events (OR, 6.30; 95% CI, 1.41–28.03), after adjustment for confounders; hospital stay was much longer. The same was true when the analysis was limited to the diabetes cohort or by comparing pure stress hyperglycemia vs diabetes without stress hyperglycemia. Conclusion: The study highlights the importance of stress hyperglycemia for adverse events in the setting of orthopedic surgery following trauma injuries. This condition requires stricter management, considering the much longer length of hospital stay and higher costs

Towards a Muon Collider

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work.Comment: 118 pages, 103 figure

Towards a muon collider

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work

Erratum:Towards a muon collider

LPT

Towards a muon collider

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work

Erratum: Towards a muon collider

The original online version of this article was revised: The additional reference [139] has been added. Tao Han’s ORICD ID has been incorrectly assigned to Chengcheng Han and Chengcheng Han’s ORCID ID to Tao Han. Yang Ma’s ORCID ID has been incorrectly assigned to Lianliang Ma, and Lianliang Ma’s ORCID ID to Yang Ma. The original article has been corrected

Managing the combination of nonalcoholic fatty liver disease and the metabolic syndrome

Introduction: Metabolic syndrome (MetS) and nonalcoholic fatty liver disease (NAFLD) are part of the same metabolic defect, both having insulin resistance as the main pathogenic mechanism and sharing similar outcomes (i.e., cardiovascular and liver-related mortality). The prevalence of NAFLD is expected to rise, owing to the increasing worldwide prevalence of obesity and MetS; therefore, the identification of factors responsible for disease progression is essential to devise therapeutic strategies. Areas covered: The available and potential future treatments for NAFLD in combination with MetS are reviewed in this paper, following an extensive literature search and personal experience. Expert opinion: All NAFLD patients should be evaluated for their metabolic, cardiovascular and liver-related risk. Weight loss through lifestyle intervention remains the most comprehensive and safe treatment of NAFLD and associated MetS; however, > 50% of patients fail to achieve target weight loss. Pharmacologic treatment seems to be important for these patients and for NAFLD cases with more advanced liver disease. It temporarily reverses metabolic alterations, but liver disease progresses after the treatment is stopped. Although current treatments are unsatisfactory, new drugs have been proposed and a few innovative compounds are in the pipeline of pharmaceutical companies. Before pharmacologic treatment can be routinely recommended for NAFLD, long-term randomized trials are needed, along with assessments of the safety and benefits of drugs on proper histological outcomes or validated surrogate markers. The intensive control of individual features of MetS remains mandatory

The determinants for oxygen delivery: is increased fraction of inspired oxygen always crucial?

Oxygen (O2) therapy consists in the administration of a gas mixture with a percentage of O2 increased and it is one of the most common aids used in hypoxia. In this paper we presented the data analyzed by Huang, as a pretext to try to provide an explanation of the physiopathological effects of oxygen administration on tissue oxygenation. The rationale of O2 therapy is to increase the inspired partial pressure of O2, increasing the fraction of inspiratory O2. Oxygen induces a vasoconstriction on sistemic circulation and this effect reduces the cardiac output, increasing the afterload. The mechanisms by which hyperoxia induces vasoconstriction are different. Oxygen also has effects on lung function, redox balance, and it is involved in the production of reactive O2 species (ROS) and other systemic effects, which in turn are involved in the changes of reduced oxygen delivery (DO2). This last would possibly help to consider carefully the risk of DO2 in each patient

Nurse-managed basal-bolus versus sliding-scale insulin regimen in subjects with hyperglycemia at admission for orthopedic surgery: a propensity score approach

Aims: A sliding-scale (SS) regimen is discouraged to correct hyperglycemia in hospital patients, but there is resistance to adoption of basal-bolus (BB) treatment in surgical units. We tested the feasibility and the effects of a nurse-based BB regimen in orthopedic surgery. Methods: Following an intense training to implement a protocol amenable by nurses, a group of patients admitted with hyperglycemia in an orthopedic institute were prospectively followed according to a basal-bolus insulin regimen (BB, n = 80). They were compared with a hyperglycemic group eventually treated by sliding-scale insulin on demand (SS, n = 122). Diabetes was present in 196 cases. Metabolic control was assessed during the first 3 days of surgery; outcome data were tested by logistic regression, after adjusting for propensity score. Result: Average blood glucose and glucose variability were lower in BB versus SS (P < 0.001), in the presence of similar 3-day insulin doses. Complications were recorded in 68 cases (16.2% vs. 45.1% in BB and SS, respectively). BB regimen was associated with propensity-adjusted reduction in all adverse events [odds ratio (OR) 0.36; 95% confidence interval (CI) 0.17-0.76] and of systemic infections (OR 0.18; 95% CI 0.07-0.50) and with shorter hospital stay (8.8 \ub1 SD 5.2 days vs. 12.5 \ub1 7.4; P < 0.01). The superiority of BB regimen was confirmed in the pair-matched analysis. Conclusions: The study proves the feasibility and the superiority of nurse-based BB versus SS treatment in metabolic control and on the risk of adverse events in orthopedic surgery patients with hyperglycemia