Arterial Blood Gases and Acid-Base Regulation.

Disorders of acid-base status are common in the critically ill and prompt recognition is central to clinical decision making. The bicarbonate/carbon dioxide buffer system plays a pivotal role in maintaining acid-base homeostasis, and measurements of pH, PCO2, and HCO3 - are routinely used in the estimation of metabolic and respiratory disturbance severity. Hypoventilation and hyperventilation cause primary respiratory acidosis and primary respiratory alkalosis, respectively. Metabolic acidosis and metabolic alkalosis have numerous origins, that include alterations in acid or base intake, body fluid losses, abnormalities of intermediary metabolism, and renal, hepatic, and gastrointestinal dysfunction. The concept of the anion gap is used to categorize metabolic acidoses, and urine chloride excretion helps define metabolic alkaloses. Both the lungs and kidneys employ compensatory mechanisms to minimize changes in pH caused by various physiologic and disease disturbances. Treatment of acid-base disorders should focus primarily on correcting the underlying cause and the hemodynamic and electrolyte derangements that ensue. Specific therapies under certain conditions include renal replacement therapy, mechanical ventilation, respiratory stimulants or depressants, and inhibition of specific enzymes in intermediary metabolism disorders.

Concomitant Lung and Kidney Disorders in Critically Ill Patients: Core Curriculum 2022.

The lungs and kidneys are cooperative and interdependent organs that secure the homeostasis of the body. Volume and acid-base disorders sit at the nexus between these two systems. However, lung-kidney interactions affect the management of many other conditions, especially among critically ill patients. Therefore, management of one system cannot proceed without a thorough understanding of the physiology of the other. This installment of AJKD's Core Curriculum in Nephrology discusses the complex decision-making required in treating concomitant respiratory and kidney disorders. We cover systemic diseases of the pulmonary and glomerular capillaries, acute decompensated heart failure, management of acid-base disorders in acute respiratory distress syndrome and chronic obstructive pulmonary disease, and venous thromboembolism. Through a case-based approach, we weigh the factors affecting the risks and benefits of therapies to enable the reader to individualize treatment decisions in these challenging scenarios.

Potassium balance in dialysis patients.

The advent of dialytic therapy has enabled nephrologists to provide life-saving therapy, but potassium balance continues to be an ever present challenge in the ESRD population. Although a small percent of patients are chronically hypokalemic, hyperkalemia is by far the most common abnormality in dialysis patients. It is associated with increased all-cause mortality, cardiovascular mortality, and arrhythmogenic death. Although alterations of the dialysis bath may decrease predialysis potassium, potassium baths <2 mEq/l are associated with a higher risk of sudden cardiac death. Studies show that patients are aware of the risks of hyperkalemia, but adherence to a low potassium diet is suboptimal. ACEI, ARBs, and spironolactone may cause slight increases in potassium even in anuric patients, requiring increased surveillance. Fludrocortisone and potassium binders have not been proven to be beneficial in lowering interdialytic potassium levels. Frequent hemodialysis may be a viable option, and studies of prophylactic placement of implantable cardioverter/defibrillators are underway.

Dietary sodium: a therapeutic target in the treatment of hypertension and CKD.

Interventional trials of dietary sodium reduction have demonstrated improvements in blood pressure, cardiovascular events, and chronic kidney disease (CKD). Furthermore, public health initiatives to reduce population sodium intake in Finland and Japan have shown similar benefit in blood pressure and stroke reduction. Recent follow-up data from large cohort trials that suggest increased mortality among individuals with lower urinary sodium excretion have generated controversy regarding the optimal sodium intake. This paper reviews the evidence for the reduction of dietary sodium to prevent and manage chronic diseases, including hypertension, cardiovascular disease, and CKD.

Right Ventricle Dilation Detected on Point-of-Care Ultrasound Is a Predictor of Poor Outcomes in Critically Ill Patients With COVID-19.

BACKGROUND: During the COVID-19 pandemic, the need for judicious use of diagnostic tests and to limit personnel exposure has led to increased use and dependence on point-of-care ultrasound (POCUS) examinations. We reviewed POCUS findings in patients admitted to the intensive care unit (ICU) for acute respiratory failure with COVID-19 and correlated the findings to severity of illness and 30-day outcomes. METHODS: Patients admitted to the ICU in March and April 2020 were reviewed for inclusion (acute hypoxemic respiratory failure secondary to COVID-19 pneumonia; documentation of POCUS findings). RESULTS: Forty-three patients met inclusion criteria. B lines and pleural thickening were associated with a lower PaO2/FiO2 by 71 (P = .005; adjusted R 2 = 0.24). Right ventricle (RV) dilation was more common in patients with 30-day mortality (P = .02) and was a predictor of mortality when adjusted for hypertension, diabetes mellitus, and age (odds ratio, 12.0; P = .048). All patients with RV dilation had bilateral B lines with pleural irregularities. CONCLUSIONS: Although lung ultrasound abnormalities are prevalent in patients with severe disease, RV involvement seems to be predictive of outcomes. Further studies are needed to discern the etiology and pathophysiology of RV dilation in COVID-19.

Histopathologic and Clinical Features in Patients with Diabetes and Kidney Disease.

Background: The discovery of nondiabetic kidney disease (NDKD) in an individual patient with diabetes may have significant treatment implications. Extensive histopathologic data in this population are lacking, but they may provide insights into the complex pathogenesis of diabetic nephropathy (DN) and reveal specific phenotypes for the development of targeted therapies. This study seeks to elucidate the clinical and laboratory parameters associated with the spectrum of kidney histopathologic features in patients with diabetes. Methods: This study is a retrospective analysis of 399 kidney biopsies assessed from 2014 to 2016 at the University of Washington among patients with diabetes. More comprehensive clinical data were evaluated in a subset of 79 participants. Results: Of the 399 biopsies reviewed, 192 (48%) had a primary diagnosis of DN (including 26 with an additional diagnosis), and 207 (52%) had a primary diagnosis of NDKD (including 67 who also had DN). Retinopathy (sensitivity: 0.86; specificity: 0.81; OR, 27.1; 95% CI, 6.8 to 107.7) and higher levels of proteinuria (7.6 versus 4.1 g/d; P=0.004) were associated with DN, whereas a physician description of AKI was associated with a lower risk of DN (OR, 0.13; 95% CI, 0.04 to 0.38). The four most prevalent diagnoses in participants with NDKD were FSGS in 39, nephrosclerosis in 29, IgA nephropathy in 27, and acute tubular injury in 21. Conclusions: Among patients with diabetes who undergo kidney biopsy in the Pacific Northwest, approximately half have DN, and half have NDKD. Retinopathy and more severe proteinuria were associated with DN, and AKI was a more common descriptor in NDKD.Podcast: This article contains a podcast at https://www.asnonline.org/media/podcast/K360/2020_11_25_KID0003962020.mp3.

Practical use of home blood pressure monitoring in chronic kidney disease.

Despite the availability of blood pressure (BP)-lowering medications and dietary education, hypertension is still poorly controlled in the chronic kidney disease (CKD) population. As glomerular filtration rate declines, the number of medications required to achieve BP targets increases, which may lead to reduced patient adherence and therapeutic inertia by the clinician. Home BP monitoring (HBPM) has emerged as a means of improving diagnostic accuracy, risk stratification, patient adherence, and therapeutic intervention. The definition of hypertension by HBPM is an average BP >135/85 mm Hg. Twelve readings over the course of 3-5 days are sufficient for clinical decision making. Diagnostic accuracy is especially important in the CKD population as approximately half of these patients have either white coat hypertension or masked hypertension. Preliminary data suggest that HBPM outperforms office BP monitoring in predicting progression to end-stage renal disease or death. When combined with additional support such as telemonitoring, medication titration, or behavioral therapy, HBPM results in a sustained improvement in BP control. HBPM must be adapted to provide information on the phenomena of nondipping (absence of nocturnal fall in BP) and reverse dipping (paradoxical increase in BP at night). These diurnal patterns are more prevalent in the CKD population and are important cardiovascular risk factors. Ambulatory BP monitoring provides nocturnal BP readings and unlike HBPM may be reimbursed by Medicare when certain criteria are met. Further studies are needed to determine whether HBPM is cost-effective in the current US healthcare system.