Endothelial Dysfunction in Patients Undergoing Cardiac Surgery: A Narrative Review and Clinical Implications

Cardiac surgery is one of the highest-risk procedures, usually involving cardiopulmonary bypass and commonly inducing endothelial injury that contributes to the development of perioperative and postoperative organ dysfunction. Substantial scientific efforts are being made to unravel the complex interaction of biomolecules involved in endothelial dysfunction to find new therapeutic targets and biomarkers and to develop therapeutic strategies to protect and restore the endothelium. This review highlights the current state-of-the-art knowledge on the structure and function of the endothelial glycocalyx and mechanisms of endothelial glycocalyx shedding in cardiac surgery. Particular emphasis is placed on potential strategies to protect and restore the endothelial glycocalyx in cardiac surgery. In addition, we have summarized and elaborated the latest evidence on conventional and potential biomarkers of endothelial dysfunction to provide a comprehensive synthesis of crucial mechanisms of endothelial dysfunction in patients undergoing cardiac surgery, and to highlight their clinical implications.

On pandemics and pivots: a COVID-19 reflection on envisioning the future of medical education

The required adjustments precipitated by the coronavirus disease 2019 crisis have been challenging, but also represent a critical opportunity for the evolution and potential disruptive and constructive change of medical education. Given that the format of medical education is not fixed, but malleable and in fact must be adaptable to societal needs through ongoing reflexivity, we find ourselves in a potentially transformative learning phase for the field. An Association for Medical Education in Europe ASPIRE Academy group of 18 medical educators from seven countries was formed to consider this opportunity, and identified critical questions for collective reflection on current medical education practices and assumptions, with the attendant challenge to envision the future of medical education. This was achieved through online discussion as well as asynchronous collective reflections by group members. Four major themes and related conclusions arose from this conversation: Why we teach: the humanitarian mission of medicine should be reinforced; what we teach: disaster management, social accountability and embracing an environment of complexity and uncertainty should be the core; how we teach: open pathways to lean medical education and learning by developing learners embedded in a community context; and whom we teach: those willing to take professional responsibility. These collective reflections provide neither fully matured digests of the challenges of our field, nor comprehensive solutions; rather they are offered as a starting point for medical schools to consider as we seek to harness the learning opportunities stimulated by the pandemic.

WHAT IS STRESS HYPERGLYCEMIA? A SUGGESTION FOR AN IMPROVEMENT OF ITS DEFINITION

CONTEXT

Stress hyperglycemia has been studied in numerous critical illnesses for several decades. Despite the extensive accumulation of knowledge about this topic, the definition of stress hyperglycemia is not updated since 2007.

SUBJECTS AND METHODS

We performed a narrative review about stress hyperglycemia in acute myocardial infarction (AMI), aiming to improve its current definition and to give evidence supporting this.

RESULTS

The definition of stress hyperglycemia in 2021 we recommend is: "SH is a high ABGly in an AMI patient irrespective of DM status. It can be calculated as e.g., "stress hyperglycemia ratio" or "admission glucose delta"/"glycemic gap". This definition may serve to start a consensus document of the experts in the field. The evidence accumulates supporting the possibility to recognize stress hyperglycemia also in AMI patients with diabetes mellitus (DM) by calculating glycemia during the previous 2-3 months using glycated hemoglobin. Moreover, it is now obvious that 2007 definition of stress hyperglycemia did not take into account the necessity to separate cut-offs for the subgroups with vs. without DM.

CONCLUSIONS

We demonstrated the insufficiency of the current 2007 definition of stress hyperglycemia, provided evidence-based recommendation for the improvement and suggested the need for a consensus of the experts on this topic. In order to optimize the treatment of stress hyperglycemia in numerous critical illnesses, we ought to have its universal definition (as we already have the universal definition of AMI).

High likelihood for atrial fibrillation in Cushing's syndrome

OBJECTIVE

This review analyzes the prevalence of the most important comorbidities associated with atrial fibrillation (AF) in the growing population of patients with Cushing's syndrome (CS).

MATERIALS AND METHODS

The review is arranged in a way to list important risk factors for AF and the references, which suggest the significant prevalence of these particular risk factors in CS. The search is conducted on PubMed, Science Direct, Springer, Wiley, SAGE, Oxford Press, and Google Scholar. PubMed search for "Cushing's syndrome atrial fibrillation" on 8/7/2019 revealed 4 papers only. None of them either analyzed or implicated high risk for AF in CS.

RESULTS

Arterial hypertension (AHT) can be found in approximately 80% of adult individuals with endogenous CS and in 20% of patients with exogenous CS. The reported prevalence of diabetes mellitus (DM) is from 13% to 47% in CS patients and the risk for de novo DM is approximately two-fold higher in individuals treated with glucocorticoids. High risk for myocardial infarction (MI) with hazard ratio (HR) 3.7 (95% confidence intervals, CI 2.4-5) in patients with endogenous CS was found. In CS patients the obesity can be detected in up to 41% and overweight in 21-48%. Left ventricular hypertrophy (LVH), pulmonary thromboembolism (PTE), infections, and hypokalemia are also more prevalent in CS as compared to healthy population. All cited comorbidities have been associated with AF. Therefore, clustering of the important factors associated with AF is confirmed repeatedly in CS.

CONCLUSIONS

The prevalence of AF in CS should be studied more precisely, both in a scientific way and at the individual patient's level.

Effects of the reservoir bag disconnection on inspired gases during general anesthesia: a simulator-based study

BACKGROUND

Fresh gas decoupling is a feature of the modern anesthesia workstation, where the fresh gas flow (FGF) is diverted into the reservoir bag and is not added to the delivered tidal volume, which thus remains constant. The present study aimed to investigate the entraining of the atmospheric air into the anesthesia breathing circuit in case the reservoir bag was disconnected.

METHODS

We conducted a simulator-based study, where the METI HPS simulator was connected to the anesthesia workstation. The effect of the disconnected reservoir bag was evaluated using oxygen (O2) and air or oxygen and nitrous oxide (N2O) as a carrier gas at different FGF rates. We disconnected the reservoir bag for 10 min during the maintenance phase. We recorded values for inspiratory O2, N2O, and sevoflurane. The time constant of the exponential process was estimated during reservoir bag disconnection.

RESULTS

The difference of O2, N2O and sevoflurane concentrations, before, during, and after reservoir bag disconnection was statistically significant at 0.5, 1, and 2 L/min of FGF (p < 0.001). The largest decrease of the inspired O2 concentrations (FIO2) was detected in the case of oxygen and air as the carrier gas and an FGF of 1 L/min, when oxygen decreased from median [25th-75th percentile] 55.00% [54.00-56.00] to median 39.50% [38.00-42.50] (p < 0.001). The time constant for FIO2 during reservoir bag disconnection in oxygen and air as the carrier gas, were median 2.5, 2.5, and 1.5 min in FGF of 0.5, 1.0, and 2 L/min respectively.

CONCLUSIONS

During the disconnection of the anesthesia reservoir bag, the process of pharmacokinetics takes place faster compared to the wash-in and wash-out pharmacokinetic properties in the circle breathing system. The time constant was affected by the FGF rate, as well as the gradient of anesthetic gases between the anesthesia circle system and atmospheric air.

Liver anatomy, intrahepatic vascular and biliary branching system of the mole rat (Spalax leucodon)

BACKGROUND

There are many studies on the morphology of the liver and its blood vessels in experimental animals, but such studies are lacking in the mole rat (Spalax leucodon). The aim of this paper was a detailed basic study on the topography, morphology, vascular and biliary branching systems of the liver in the mole rat.

MATERIALS AND METHODS

Coloured gelatine and mixture of coloured lead oxide and linseed oil were injection contrast masses used to obtain vascular and biliary branching pattern in the liver. It was revealed that the liver of the mole rat had five lobes (left, quadrate, right medial, right lateral and caudate lobes).

RESULTS

The left, undivided lobe was the largest lobe of the liver. The quadrate lobe was divided into two components by a deep notch. The gallbladder, of cylindrical shape, was present and attached to the quadrate lobe. The common bile duct was formed by the union of the left and right hepatic ducts. The pancreatic duct joined the common bile duct before it entered the duodenum. In the present study, only the right medial lobe and quadrate lobe always showed a single lobar artery, portal and hepatic veins. The left lobe showed four lobar arteries, portal and hepatic veins. The caudate lobe with its two processes and the right lateral and medial lobes had different arterial and portal blood supply as well as hepatic and biliary drainage of these lobes. The intrahepatic branches of the proper hepatic artery ran parallel to the branches of the common portal vein in the same lobes of the liver.

CONCLUSIONS

The results of this study are significant for comparative studies among different species of rodents and other experimental animals. Morphology, vasculature and biliary tract of the liver in the mole rat were similar to that of other experimental animals and identified differences may be related to the adaptation to the mode of life and diet of this rodent.

Usefulness of heart rate recovery parameters to monitor cardiovascular adaptation in elite athletes: The impact of the type of sport

PURPOSE

The purpose of this study is to determine heart rate (HR) recovery after maximal test in elite athletes who compete in high dynamic, high static, and in mixed sport disciplines; to assess differences in HR recovery between these groups of athletes; and to measure the association of HR index (HRI) with heart adaptation variables to determine whether these values were correlated with the type of exercise.

METHODS

One hundred and ninety-four elite athletes were divided into three groups according to the predominant type of exercise performed: endurance (n = 40), strength-sprinter (n = 36), and ball-game players (n = 118). They performed maximal cardiopulmonary exercise testing on a treadmill and were subjected to echocardiography. The rate of decline (HR recovery) was calculated as the difference between maximum and recovery HRs (HRrec1 and HRrec3). The HRI was calculated as HR_max - 1-min post-exercise HR (HRrec1).

RESULTS

The most significant correlation of HRI was with posterior wall diameter and left ventricular (LV) mass index (r = 0.43 and r = 0.51; p = 0.012 and p = 0.003, respectively). LV mass index [Beta (B) = 0.354, p = 0.001] was an independent predictor of HRI and HRrec1. HRI may be an effective tool for discrimination of physiological and "gray zone" LV hypertrophy, with area under the curve of 0.545 (95% CI = 0.421-0.669, p = 0.0432). HRI displayed a sensitivity of 50% and specificity of 52.2% at the optimal cut-off value of 23.5.

CONCLUSION

HR recovery pattern, especially HRI, may offer a timely and efficient tool to identify athletes with autonomous nervous system adaptive changes.

Students as partners: Our experience of setting up and working in a student engagement friendly framework

BACKGROUND

Student engagement (SE) in the curriculum is a positive indicator in the development of students deeply involved in their learning. It also has several benefits for the schools' level of educational innovation and quality assurance.

METHOD

In order to identify the most important pearls from the last decade of educational developments within the field of SE at the Faculty of Medicine University of Maribor, we searched through our school's archives, publications and research in the field of medical education.

RESULTS

Three areas were identified as the most important SE complements: (i) peer teaching, (ii) school governance, and (iii) extracurricular activities. The paper highlights how many student-driven initiatives move from informal frameworks toward a formal structure, elective courses, and, in the end, compulsory components of the curriculum.

DISCUSSION

As demonstrated by the three educational achievements at our school, fostering a high level of SE can lead to innovative curricular changes, benefit the whole school and enable students to deliver highly impactful extracurricular projects.

[Ochronosis--an autopsy case report]

The authors have presented a case of ochronosis, as the incidental finding during the autopsy of a female patient, aged 59 years. It was the case of suicidal drug poisoning. Ochronosis is a rare disease, with chronic benign course, but frequently followed by complications. Histopathological criteria for the diagnosis of this disease are described in detail.

Ouabain arrhythmogenicity in hypertrophied right and left ventricle of the rat

Susceptibility to the arrhythmogenic action of ouabain was tested in rats with right ventricular hypertrophy, due to experimental chronic hypoxic pulmonary hypertension, and in spontaneously hypertensive (SH) rats with left ventricular hypertrophy. As parameters of arrhythmogenicity the time-duration of infusion of a solution of ouabain (1 g/100 ml), at a rate of 0.7 mg/kg per minute, was measured until the appearance on the ECG of the first premature ventricular contraction, ventricular tachycardia and cardiac arrest. All three effects of digitalis toxicity (premature ventricular contraction, ventricular tachycardia and cardiac arrest) appeared significantly earlier both in rats with right ventricular hypertrophy, due to chronic experimental hypoxic pulmonary hypertension, and in SH rats with hypertrophy of the left ventricle, as compared to the infusion time of the same solution of ouabain needed to elicit the mentioned toxic effects in control rats without ventricular hypertrophy.

Hypotensive effect of heparin on experimental chronic pulmonary hypertension in rats

Daily heparin injections (300 mg s.c.) during four weeks of hypoxic exposure resulted in a smaller rise in pulmonary artery pressure as compared with otherwise nontreated rats exposed to the same regimen of hypoxia. Heparin treatment did not significantly affect the systemic arterial pressure of the hypoxic rats. In spite of the different pressure load of the right ventricle after hypoxia in treated and control rats, there was no difference in parameters indicative of the degree of right ventricular hypertrophy between these two groups of hypoxic rats. This finding suggests that the difference in pressure load between the two groups of hypoxic rats occurred late in the course of hypoxic exposure.

Platelets in rats with chronic normobaric hypoxic pulmonary hypertension

A study of the platelet count in rats exposed to normobaric hypoxia for 4 weeks revealed that hypoxia alone, without any change in barometric pressure, considerably reduced the number of thrombocytes. In order to elucidate the mechanism of hypoxic thrombocytopenia, the survival and recovery of 51Cr-labelled platelets were tested. The survival and recovery of platelets from hypoxic rats injected into normoxic recipients were normal. However, when 51Cr-labelled platelets from normoxic rats were injected into a hypoxic recipient, the survival was found to be normal but the recovery of those platelets was lower than in the normal rat. This finding suggests that the reduction of platelet counts in normobaric hypoxia may be due to the platelets' partial sequestration.

Separate and combined use of verapamil, aspirin and captopril in experimental chronic pulmonary hypertension

In Wistar rats, rendered pulmonary hypertensive by chronic confinement in normobaric "hypoxic cages", impairment of transmembrane transport of calcium by Verapamil and blockage of the action of Angiotensin I converting enzyme by Captopril when applied simultaneously did not show an additive effect in reducing the rise of pulmonary artery pressure and decreasing the augmentation of right ventricular mass. Similarly, the action of Verapamil together with decrease of prostaglandin synthetase activity by Aspirin showed no additive effect. Although in this way the results of the present study failed to give substantial support to the idea of the existence of several mediators of hypoxic pulmonary vasoconstriction, they by no means deny this possibility.

A sex difference in the hemodynamic effects of chronic normobaric hypoxia in rats

The packed cell volume was higher and the increase in systolic pressure in the right ventricle, as an indication of systolic pressure in the pulmonary artery, was smaller in female rats previously exposed for 4 weeks to normobaric hypercapnic hypoxia, as compared to males treated in the same way. Gonadectomy performed in male rats either on the first day of life or after maturation did not have a significant influence on circulatory reaction to chronic normobaric hypoxia. Female rats in permanent estrus and those with ovariectomy had larger posthypoxic hypertrophy of the right ventricle as indicated by higher values for right/left ventricular weight ratio and relative weight of the right ventricle, than untreated controls.

Effects of verapamil and aspirin on experimental chronic hypoxic pulmonary hypertension and right ventricular hypertrophy in rats

Rats made hypoxic by confinement in hypoxic cages for 4 weeks developed pulmonary hypertension and right ventricular hypertrophy. Treatment with Verapamil or aspirin reduced both chronic hypoxic pulmonary hypertension and the hypertrophy of the right ventricle. The antihypertensive effect of Verapamil is explained by the involvement of the transmembrane calcium flux in pulmonary vascular smooth muscle in the hypoxic vasoconstrictory response. Part of the antihypertensive effect of inhibition of prostaglandin synthesis is attributed to a decrease in packed cell volume produced in hypoxic, aspirin treated rats.

In vitro contractility of the hypertrophied right ventricle of rats with pulmonary hypertension due to confinement in "hypoxic cages"

Four weeks' confinement of rats in individual airtight cages with walls of defined permeability for respiratory gases induced hypoxic pulmonary hypertension and right ventricular hypertrophy. Parameters of isometric contractility of strips of hypertrophied right myocardium did not show significant changes when compared with the parameters of the inotropic state of slices of normal right ventricle.