Conceptual Approach to Body Fluids and Edema, Education Determines Clinical Outcomes in Heart Failure.

In this brief communication, we reemphasize the importance of critical thinking in clinical practice using the example of edema. The common practice of thinking and inquiry by practicing clinicians has beneficial implications for healthcare by improving outcomes and patient care while alleviating the burden of misconceptions in practice. We provide an in-depth and interactive investigation of physiological concepts as a foundation for understanding body fluid dynamics. Finally, we offer a new classification of symptoms of heart failure. DOI: 10.52547/ijkd.8171.

An Agent-Based Modeling and Virtual Reality Application Using Distributed Simulation: Case of a COVID-19 Intensive Care Unit.

Hospitals and other healthcare settings use various simulation methods to improve their operations, management, and training. The COVID-19 pandemic, with the resulting necessity for rapid and remote assessment, has highlighted the critical role of modeling and simulation in healthcare, particularly distributed simulation (DS). DS enables integration of heterogeneous simulations to further increase the usability and effectiveness of individual simulations. This article presents a DS system that integrates two different simulations developed for a hospital intensive care unit (ICU) ward dedicated to COVID-19 patients. AnyLogic has been used to develop a simulation model of the ICU ward using agent-based and discrete event modeling methods. This simulation depicts and measures physical contacts between healthcare providers and patients. The Unity platform has been utilized to develop a virtual reality simulation of the ICU environment and operations. The high-level architecture, an IEEE standard for DS, has been used to build a cloud-based DS system by integrating and synchronizing the two simulation platforms. While enhancing the capabilities of both simulations, the DS system can be used for training purposes and assessment of different managerial and operational decisions to minimize contacts and disease transmission in the ICU ward by enabling data exchange between the two simulations.

Arterial Versus Venous Blood Gas Analysis Comparisons, Appropriateness, and Alternatives in Different Acid/Base Clinical Settings: A Systematic Review.

Arterial blood gases (ABGs) are routinely done in critical clinical settings to ascertain acid-base status. Due to difficulties and the potential side effects following arterial blood sampling, much research has been done to find the possibility of using venous samples as an alternative. However, this comparison needs to be evaluated in various contexts. Hence, this systematic review aims to explore the differences, appropriateness, and alternatives of arterial versus venous blood gas (VBG) analysis in different acid-base states. A comprehensive literature search was conducted through electronic databases using the terms "ABG," "VBG," "Arterial Blood Gas," "Venous Blood Gas," and "Gas analysis." Studies' qualities were assessed by using Newcastle - Ottawa Quality Assessment Scale. Of 531 articles, 22 were included in the study after title, abstract, and full-text screening. Based on the Newcastle - Ottawa Quality Assessment Scale, 23% of the studies had good quality (score ≥ 7), 77% fair quality (score 2-6), and none of the studies had poor quality (score ≤ 1). Moreover, 22.5% of the included articles found a strong correlation between ABG and VBG. 73% compared arterial and VBG parameters among patients with any clinical contexts, 22.5% in respiratory diseases, and 4.5% in metabolic conditions, and their results had a significant disparity. There was a considerable discrepancy among authors about the appropriateness and utilization of VBG as an alternative to ABG. Our findings suggest that those studies did not consider physiological differences between venous and arterial blood values and obviated the significance of sampling procedures.

Perioperative Hypertension Etiologies in Patients Undergoing Noncardiac Surgery in University Health Network Hospitals-Canada from 2015-2020.

Introduction: Perioperative hypertension, defined as increased blood pressure around the surgery, is a known risk factor for perioperative complications, including cardiovascular events. Identifying reasons associated with hypertension in each period is of great help in preventing and better managing perioperative hypertension. Objective: The aim of the study was to explore common etiologies of hypertension during the perioperative period (pre, intra, and post-operation) in patients who underwent noncardiac surgeries in University Health Network (UHN) hospitals, Canada, from 2015 to 2020. Patients and Methods: We retrospectively analyzed the medical records of 174 patients undergoing noncardiac surgeries who experienced perioperative hypertension. We assessed the prevalence of 10 reasons for perioperative hypertension as a whole and also each period separately according to the physicians' notes in patients' medical records. Two-way measurements ANOVA was used to determine the change of mean hypertension among patients for specific etiology. Results: The common etiologies of perioperative hypertension were poorly controlled hypertension (21.8%), excessive fluid therapy (19.5%), excessive vasopressor (18.4%), and medication withdrawal (13.7%). Regarding each period separately, the most common reasons were poorly controlled hypertension for pre (42.9%) and intraoperative period (22.7%) and fluid overload for the postoperative period (20.1%). Poor control of hypertension showed both within-subject statistical significance for systolic and between-subject statistical significance for diastolic blood pressure. Conclusion: Poorly controlled hypertension is the most significant etiology of perioperative hypertension in patients undergoing noncardiac surgeries. Apart from poorly controlled hypertension, as a patient-related factor, iatrogenic factors such as excessive vasopressor therapy, aggressive fluid replacement and poor management of antihypertensive medications can also cause perioperative hypertension.

Conceptual Approach to Body Fluids and Edema, Education Determines Clinical Outcomes in Nephrotic Syndrome Management.

The objective of our paper is to reemphasize the importance of critical thinking in clinical practice and education in the field of internal medicine using the example of edema. We provide an in-depth and interactive investigation of physiological concepts as a foundation for the understanding of body fluid dynamics. Four fundamental concepts described are the hydrostatic and oncotic pressure gradients, capillary permeability, and lymphatic drainage. Furthermore, we visit the causes of edema in nephrotic syndrome. Traditional teaching considers hypoalbuminemia as a primary cause of edema formation in nephrotic syndrome. It has been proven that other etiologies causing edema include salt and water retention by the kidneys and a possible increase in capillary permeability are more important causes in the development of edema in nephrotic syndrome.

Are individual analyses of multiple short urine collections throughout the 24 hours superior to a standard 24-hour urine collection in precipitation risk assessment of healthy subjects?

PURPOSE: The commonly used 24-hour collection technique has been the mainstay of diagnosis for supersaturation but has some certain limitations. Hence, superiority of multiple short urine collections as a new alternative in precipitation risk assessment was assessed compared to the standard 24-hour urine collection among healthy subjects. MATERIALS AND METHODS: Individual urine samples of 26 healthy subjects were acquired every 2 to 3 hours throughout the 24 hours. Urine samples were obtained and the time and volume of each sample were recorded. Urinary constituents involved in precipitation including, sodium-potassium, chloride, calcium, phosphate, citrate, magnesium, urea, creatinine and pH were measured. A simulated 24-hour collection was recalculated by the totalling of all shorter urine collections volume and urinary constituents excretions throughout the day. RESULTS: Urine pH, urine creatinine and precipitation rate had a significantly lower values in 24-hours urine collection compared to one individual value of multiple urine collections by -0.769 (P < .0001), -7.305 (P < .0001), and - 12.838 (P < .0001), respectively. However, calcium (2.697, P < .0001), citrate (3.54, P < .0001), total phosphate (19.961, P < .0001) and total creatinine (9.579, P < .0001) had statistically significantly higher values in the 24-hours urine collection compared to individual value of multiple urine collections. CONCLUSION: Based on the results, individual analysis of multiple shorter urine collections throughout the day improves the ability of identifying supersaturation points, precipitation risk zones and may potentially improve risk assessment compared to the 24-hour urine collection method.

Impact of Prolonged Fasting on the Risk of Calcium Phosphate Precipitation in the Urine: Calcium Phosphate Lithogenesis during Prolonged Fasting in a Healthy Cohort.

PURPOSE: Intermittent fasting and curtailing water intake for extended periods were likely common in Paleolithic times. Today it occurs for religious and dietary reasons. This restriction in intake should cause a decrease in the urine flow rate while raising the concentration of certain substances in urine to the point of precipitation. In this study we measured the risk of CaHPO4 precipitation following 18 hours of food and water deprivation. MATERIALS AND METHODS: Urine samples were periodically collected from 15 healthy subjects who fasted and abstained from drinking any liquid for 18 hours. The urine constituents Ca2+, HPO42- and pH involved in CaHPO4 formation were measured at various times throughout the fasting day. A comparison was made with control data, which consisted of diurnal urine collections taken throughout a separate nonfasting day prior to the fasting day. RESULTS: The mean ± SEM urine flow rate decreased significantly from 0.93 ± 0.1 ml per minute in the control group to 0.37 ± 0.05 ml per minute in the fasting group (p <0.05). Mean Na+ and Ca2+ excretion rates decreased significantly from 127 ± 12 to 54 ± 13 µmol per minute and from 3.2 ± 0.4 to 0.80 ± 0.21, respectively. Mean urinary Na+ and Ca2+ concentrations also decreased from 161 ± 11.6 to 122 ± 16.0 mmol/l and from 3.7 ± 0.5 to 2.0 ± 0.55, respectively. Urinary pH and the concentration of phosphate, citrate and magnesium were not significantly affected. CONCLUSIONS: Although the steady decrease in the urine flow rate was statistically significant during 18 hours of food and water deprivation, there was no evidence that the calculated risk of CaHPO4 precipitation in the healthy subjects had increased.

How Protective Mechanisms Interact to Prevent Overnight Calcium Phosphate Precipitation - An Observational Study to Determine Factors Against Calcium Phosphate Lithogenesis in a Healthy Cohort.

BACKGROUND/AIMS: As restful, non-interrupted sleep is essential for normal mental and physical functioning, the urine flow rate (UFR) overnight remains low. Due to this reduced UFR, the kidneys produce a lower urine volume, which may lead to supersaturation of lithogens in the renal collecting system. The protective mechanisms that prevent the rise in the concentration of the lithogenic substances in urine, such as calcium phosphate, are explored. METHODS: Urine samples were collected from 26 subjects every 2-3 h during daylight with one nocturnal collection; the UFR was calculated in the median time for each collection period. Urinary constituents for calcium phosphate precipitation including electrolytes, calcium, phosphate, citrate, and pH were measured. Comparisons within individuals were done by paired t test. RESULTS: The calcium excretion rate fell significantly overnight (from 2.4 ± 0.2 µmol/min during the daytime to 1.5 ± 0.3 µmol/min, p < 0.05), in parallel with sodium excretion (54 ± 16 µmol/min from its daytime 127 ± 12 µmol/min, p < 0.05), preventing nocturnal calcium concentration from increasing (3.0 ± 0.3 mmol/l daytime to 2.5 ± 0.5 mmol/l overnight), while citrate concentration did not change significantly. The total urine phosphate concentration rose significantly overnight (daytime 18.7 ± 1.4 µmol/min vs. nocturnal 20.9 ± 1.7 µmol/min), but the concentration of divalent phosphate did not increase in the overnight period. CONCLUSIONS: Although the UFR was lower overnight, there was no evidence that the risk of calcium phosphate precipitate formation in healthy subjects was increased.

Studies to identify the basis for an alkaline urine pH in patients with calcium hydrogen phosphate kidney stones.

BACKGROUND: Patients with CaHPO(4) kidney stones belong to a diagnostic category that has a high urine pH as its common feature. Our objective was to provide a new clinical approach to examine the basis for this high pH. METHODS: The study group consisted of 26 CaHPO(4) stone formers and 28 normal volunteers. Urine was collected q2h plus an overnight sample to identify patients with a urine pH > 6.5 for 12/24 h. Urine ammonium (U(NH4)), sulphate (U(SO4)) and citrate were measured and diet net alkali was calculated. RESULTS: Of the 26 patients, 13 had persistently alkaline urine. In 7/13, U(NH4) (68 +/- 13 mEq/day) and U(SO4) (57 +/- 7 mEq/day) were both high. In 6/13 patients, U(NH4) was the usual 31 +/- 3 mEq/day; in 4/6, U(NH4)/U(SO4) was 0.9 +/- 0.1; the cause of the alkaline urine pH seemed to be a dietary alkali load because the rise in urine pH was episodic and coincided with a high net diet alkali load and peak citrate excretion rates. The remaining two patients had a high U(NH4)/U(SO4) (2.2 and 1.6). Citrate excretion was very low in the male, but not in the female patient. CONCLUSIONS: There are heterogeneous causes for a persistently high urine pH. Two of the patients had a possible molecular basis: the lesion could be a low proximal convoluted tubule cell pH in the male and an increased entry of NH(3) into the late distal nephron in the female.

Defining conditions that lead to the retention of water: the importance of the arterial sodium concentration.

BACKGROUND: A water diuresis occurs when a large volume of water is ingested rapidly. Nevertheless, water conservation is required to provide a source of water for evaporative heat dissipation throughout the day. Therefore, the objective was to define conditions that permit the retention of ingested water. METHODS: Volunteers collected urine q2h plus an overnight specimen; water loading was conducted after overnight food and water restriction; paired arterialized and venous blood samples were analyzed. RESULTS: When 20 mL water/kg was consumed in <15 minutes, the peak urine flow rate was 11 +/- 0.6 mL/min. The volume of water retained after water intake stopped, and when the urine was hyperosmolar, correlated directly with the daily excretion of sodium plus potassium (r(2)= 0.63). The plasma sodium concentration (P(Na)) was 4.0 +/- 0.5 mmol/L lower in arterialized than paired venous blood 30 to 40 minutes after water ingestion began (P < 0.01). In preliminary studies, the smallest water load consumed in 15 minutes that would reproducibly cause a water diuresis was defined in each subject. This same acute water load was retained, however, if it contained 150-mmol/L fructose, but not glucose, or if it was consumed slowly (sipping). The arterialized P(Na) was not significantly lower than in paired venous samples when water was sipped. CONCLUSION: A large fall in arterialized and not venous P(Na) best reflected the signal to induce a water diuresis. Although a very large water load can induce a water diuresis, smaller water loads can be retained for future heat dissipation.

Dogmas and controversies in the handling of nitrogenous wastes: excretion of nitrogenous wastes in human subjects.

Two major nitrogenous waste products, urea and ammonium (NH(4)(+)), are produced in humans when proteins are oxidized, and in this manuscript their excretions are examined from two perspectives. First, the specific physiology of each nitrogenous waste is reviewed and the current dogmas summarized. Second, their excretions are considered in the context of integrative physiology, i.e. the need to ensure that the urine composition is appropriate to minimize the risk of kidney stone formation. After the latter analysis, weak links in our understanding of the overall physiology become apparent and a conundrum is defined. The conundrum for the excretion of urea focuses on the fact that urea is not an effective osmole in the medullary-collecting duct when vasopressin acts. As a result, it appears that urinary urea cannot prevent a large decline in the urine flow rate and thereby minimize the risk of forming kidney stones in electrolyte-poor urine. The conundrum for the excretion of NH(4)(+) is: high rates of NH(4)(+) excretion require a low urine pH, yet a pH approximately 6.0 must be maintained in order to reduce the risk of precipitating uric acid in the urine. Possible ways of resolving these conundrums require novel physiological interpretations.