Dexamethasone and postoperative analgesia in minimally invasive thoracic surgery: a retrospective cohort study

BACKGROUND

Dexamethasone is commonly used for the prevention of postoperative nausea and vomiting (PONV), and recent reviews suggest a role for dexamethasone in postoperative analgesia. The aim of this study is to evaluate the efficacy of dexamethasone as an analgesic adjuvant in minimally invasive thoracic surgery. Primary outcome was morphine consumption 24 h after surgery; secondary outcomes were pain control, measured as numeric rating scale (NRS), glycemic changes, PONV, and surgical wound infection.

RESULTS

We performed a retrospective cohort study considering 70 patients who underwent elective lobectomy, segmentectomy, or wedge resection surgery with a mini-thoracotomy approach or video-assisted thoracoscopic surgery (VATS). All patients received the same locoregional techniques and short-acting opioids during surgery; 46 patients received dexamethasone at induction. There were no significant differences in morphine consumption at 24 h (p = 0.09) and in postoperative pain scores. Nevertheless, a higher frequency of rescue therapy (p = 0.01) and a tendency for a higher attempted-PCA pushes count were observed in patients who did not receive dexamethasone. No cases of surgical wound infections were detected, and the incidence of PONV was similar in the two groups. Postoperative glycemia was transiently higher in the dexamethasone group (p = 0.004), but the need of hypoglycemic therapy was not significantly different.

CONCLUSIONS

Preoperative administration of dexamethasone did not cause a significant reduction in morphine consumption, but appears to be safe and plays a role in a multimodal anesthesia approach for patients undergoing elective minimally invasive thoracic surgery.

Addition of 5% CO2 to Inspiratory Gas Prevents Lung Injury in an Experimental Model of Pulmonary Artery Ligation

Rationale: Unilateral ligation of the pulmonary artery may induce lung injury through multiple mechanisms, which might be dampened by inhaled CO2. Objectives: This study aims to characterize bilateral lung injury owing to unilateral ligation of the pulmonary artery in healthy swine undergoing controlled mechanical ventilation and its prevention by 5% CO2 inhalation and to investigate relevant pathophysiological mechanisms. Methods: Sixteen healthy pigs were allocated to surgical ligation of the left pulmonary artery (ligation group), seven to surgical ligation of the left pulmonary artery and inhalation of 5% CO2 (ligation + FiCO2 5%), and six to no intervention (no ligation). Then, all animals received mechanical ventilation with Vt 10 ml/kg, positive end-expiratory pressure 5 cm H2O, respiratory rate 25 breaths/min, and FiO2 50% (±FiCO2 5%) for 48 hours or until development of severe lung injury. Measurements and Main Results: Histological, physiological, and quantitative computed tomography scan data were compared between groups to characterize lung injury. Electrical impedance tomography and immunohistochemistry analysis were performed in a subset of animals to explore mechanisms of injury. Animals from the ligation group developed bilateral lung injury as assessed by significantly higher histological score, larger increase in lung weight, poorer oxygenation, and worse respiratory mechanics compared with the ligation + FiCO2 5% group. In the ligation group, the right lung received a larger fraction of Vt and inflammation was more represented, whereas CO2 dampened both processes. Conclusions: Mechanical ventilation induces bilateral lung injury within 48 hours in healthy pigs undergoing left pulmonary artery ligation. Inhalation of 5% CO2 prevents injury, likely through decreased stress to the right lung and antiinflammatory effects.

Unmatched ventilation and perfusion measured by electrical impedance tomography predicts the outcome of ARDS

Background

In acute respiratory distress syndrome (ARDS), non-ventilated perfused regions coexist with non-perfused ventilated regions within lungs. The number of unmatched regions might reflect ARDS severity and affect the risk of ventilation-induced lung injury. Despite pathophysiological relevance, unmatched ventilation and perfusion are not routinely assessed at the bedside. The aims of this study were to quantify unmatched ventilation and perfusion at the bedside by electrical impedance tomography (EIT) investigating their association with mortality in patients with ARDS and to explore the effects of positive end-expiratory pressure (PEEP) on unmatched ventilation and perfusion in subgroups of patients with different ARDS severity based on PaO₂/FiO₂ and compliance.

Methods

Prospective observational study in 50 patients with mild (36%), moderate (46%), and severe (18%) ARDS under clinical ventilation settings. EIT was applied to measure the regional distribution of ventilation and perfusion using central venous bolus of saline 5% during end-inspiratory pause. We defined unmatched units as the percentage of only ventilated units plus the percentage of only perfused units.

Results

Percentage of unmatched units was significantly higher in non-survivors compared to survivors (32[27–47]% vs. 21[17–27]%, p < 0.001). Percentage of unmatched units was an independent predictor of mortality (OR 1.22, 95% CI 1.07–1.39, p = 0.004) with an area under the ROC curve of 0.88 (95% CI 0.79–0.97, p < 0.001). The percentage of ventilation to the ventral region of the lung was higher than the percentage of ventilation to the dorsal region (32 [27–38]% vs. 18 [13–21]%, p < 0.001), while the opposite was true for perfusion (28 [22–38]% vs. 36 [32–44]%, p < 0.001).

Higher percentage of only perfused units was correlated with lower dorsal ventilation (r =  − 0.486, p < 0.001) and with lower PaO₂/FiO₂ ratio (r =  − 0.293, p = 0.039).

Conclusions

EIT allows bedside assessment of unmatched ventilation and perfusion in mechanically ventilated patients with ARDS. Measurement of unmatched units could identify patients at higher risk of death and could guide personalized treatment.

Atelectasis, Shunt, and Worsening Oxygenation Following Reduction of Respiratory Rate in Healthy Pigs Undergoing ECMO: An Experimental Lung Imaging Study

Rationale: Reducing the respiratory rate during extracorporeal membrane oxygenation (ECMO) decreases the mechanical power, but it might induce alveolar de-recruitment. Dissecting de-recruitment due to lung edema vs. the fraction due to hypoventilation may be challenging in injured lungs.

Objectives: We characterized changes in lung physiology (primary endpoint: development of atelectasis) associated with progressive reduction of the respiratory rate in healthy animals on ECMO.

Methods: Six female pigs underwent general anesthesia and volume control ventilation (Baseline: PEEP 5 cmH₂O, Vt 10 ml/kg, I:E = 1:2, FiO₂ 0.5, rate 24 bpm). Veno-venous ECMO was started and respiratory rate was progressively reduced to 18, 12, and 6 breaths per minute (6-h steps), while all other settings remained unchanged. ECMO blood flow was kept constant while gas flow was increased to maintain stable PaCO₂.

Measurements and Main Results: At Baseline (without ECMO) and toward the end of each step, data from quantitative CT scan, electrical impedance tomography, and gas exchange were collected. Increasing ECMO gas flow while lowering the respiratory rate was associated with an increase in the fraction of non-aerated tissue (i.e., atelectasis) and with a decrease of tidal ventilation reaching the gravitationally dependent lung regions (p = 0.009 and p = 0.018). Intrapulmonary shunt increased (p < 0.001) and arterial PaO₂ decreased (p < 0.001) at lower rates. The fraction of non-aerated lung was correlated with longer expiratory time spent at zero flow (r = 0.555, p = 0.011).

Conclusions: Progressive decrease of respiratory rate coupled with increasing CO₂ removal in mechanically ventilated healthy pigs is associated with development of lung atelectasis, higher shunt, and poorer oxygenation.

Potential for Lung Recruitment and Ventilation-Perfusion Mismatch in Patients With the Acute Respiratory Distress Syndrome From Coronavirus Disease 2019

OBJECTIVES

Severe cases of coronavirus disease 2019 develop the acute respiratory distress syndrome, requiring admission to the ICU. This study aimed to describe specific pathophysiological characteristics of acute respiratory distress syndrome from coronavirus disease 2019.

DESIGN

Prospective crossover physiologic study.

SETTING

ICU of a university-affiliated hospital from northern Italy dedicated to care of patients with confirmed diagnosis of coronavirus disease 2019.

PATIENTS

Ten intubated patients with acute respiratory distress syndrome and confirmed diagnosis of coronavirus disease 2019.

INTERVENTIONS

We performed a two-step positive end-expiratory pressure trial with change of 10 cm H2O in random order.

MEASUREMENTS AND MAIN RESULTS

At each positive end-expiratory pressure level, we assessed arterial blood gases, respiratory mechanics, ventilation inhomogeneity, and potential for lung recruitment by electrical impedance tomography. Potential for lung recruitment was assessed by the recently described recruitment to inflation ratio. In a subgroup of seven paralyzed patients, we also measured ventilation-perfusion mismatch at lower positive end-expiratory pressure by electrical impedance tomography. At higher positive end-expiratory pressure, respiratory mechanics did not change significantly: compliance remained relatively high with low driving pressure. Oxygenation and ventilation inhomogeneity improved but arterial CO2 increased despite unchanged respiratory rate and tidal volume. The recruitment to inflation ratio presented median value higher than previously reported in acute respiratory distress syndrome patients but with large variability (median, 0.79 [0.53-1.08]; range, 0.16-1.40). The FIO2 needed to obtain viable oxygenation at lower positive end-expiratory pressure was significantly correlated with the recruitment to inflation ratio (r = 0.603; p = 0.05). The ventilation-perfusion mismatch was elevated (median, 34% [32-45%] of lung units) and, in six out of seven patients, ventilated nonperfused units represented a much larger proportion than perfused nonventilated ones.

CONCLUSIONS

In patients with acute respiratory distress syndrome from coronavirus disease 2019, potential for lung recruitment presents large variability, while elevated dead space fraction may be a specific pathophysiological trait. These findings may guide selection of personalized mechanical ventilation settings.

Intramuscular islet allotransplantation in type 1 diabetes mellitus

OBJECTIVE

Alternative sites to the liver for islet transplantation have been studied for a long time. Intramuscular islet transplantation appears to be an alternative site to the liver because of the ease of access. First islet autotransplantations were reported in patients after total pancreatectomies. The transplanted islets showed a proper revascularization and their function was observed for up to 2 years after the implant. However, only a few cases of autotransplantation and no allotransplantation have been performed. The aim of this study was to verify the feasibility of islet allotransplantation into muscles.

PATIENTS AND METHODS

In four patients affected by type 1 diabetes mellitus in which liver islet allotransplantation was contraindicated, human islets were transplanted into patients' arm muscle with local anesthesia.

RESULTS

The surgery was minimally invasive, without complications. In one patient a moderate local inflammatory reaction was observed at the site of the implant, which resolved spontaneously within 4 days. Islet graft function was observed after transplantation in all patients, but it progressively disappeared in 3 out 4 patients within a short time.

CONCLUSIONS

In this first ever-reported intramuscular pancreatic islet allotransplantation, the procedure appears feasible but new strategies must be envisaged to significantly improve islet engraftment and the long-term graft function.

Paracrine effect of regulatory T cells promotes cardiomyocyte proliferation during pregnancy and after myocardial infarction

Cardiomyocyte proliferation stops at birth when the heart is no longer exposed to maternal blood and, likewise, to regulatory T cells (Tregs) that are expanded to promote maternal tolerance towards the fetus. Here, we report a role of Tregs in promoting cardiomyocyte proliferation. Treg-conditioned medium promotes cardiomyocyte proliferation, similar to the serum from pregnant animals. Proliferative cardiomyocytes are detected in the heart of pregnant mothers, and Treg depletion during pregnancy decreases both maternal and fetal cardiomyocyte proliferation. Treg depletion after myocardial infarction results in depressed cardiac function, massive inflammation, and scarce collagen deposition. In contrast, Treg injection reduces infarct size, preserves contractility, and increases the number of proliferating cardiomyocytes. The overexpression of six factors secreted by Tregs (Cst7, Tnfsf11, Il33, Fgl2, Matn2, and Igf2) reproduces the therapeutic effect. In conclusion, Tregs promote fetal and maternal cardiomyocyte proliferation in a paracrine manner and improve the outcome of myocardial infarction.

Regulatory T cells (Tregs) expand during pregnancy to promote tolerance towards the fetus. Here the authors show that Tregs induce proliferation of fetal and maternal cardiomyocytes during pregnancy and enhance myocardial repair via proliferation-promoting paracrine actions.

Impact of omega-3 polyunsaturated fatty acids on vascular function and blood pressure: Relevance for cardiovascular outcomes

AIMS

To overview the effects of omega-3 polyunsaturated fatty acids (PUFA) on blood vessels and blood pressure (BP) and their relevance for cardiovascular prevention.

DATA SYNTHESIS

The importance of omega-3 PUFA for the cardiovascular system has come under the spotlight during the last decades. These fatty acids are present in variable amounts in cell membranes of mammal species, and their content affects a variety of cellular functions. Evidence obtained in animal and human studies suggests that omega-3 PUFA affect many steps of the atherosclerotic process. In blood vessels, omega-3 PUFA improve endothelial function; promote vasodilatation through relaxation of smooth muscle cells; exert antioxidant, anti-inflammatory, and antithrombotic actions; delay development of plaques and increase their stability; and decrease wall stiffening. Omega-3 PUFA might affect BP, and studies conducted with ambulatory monitoring suggest that supplementation with these fatty acids decreases the average 24-h BP levels. This effect on BP is related to the pretreatment membrane content of omega-3 PUFA, and this might explain some inconsistencies among intervention trials. Meta-analyses indicate that omega-3 PUFA have a mild but significant BP lowering effect. While encouraging results were initially obtained with the use of omega-3 PUFA supplements in secondary prevention trials, meta-analyses have not confirmed the ability of these fatty acids to decrease the risk of coronary heart and cerebrovascular disease.

CONCLUSIONS

Omega-3 PUFA are associated with significant improvement in vascular function and lowering of BP. However, the evidence currently supporting the role of these fatty acids in cardiovascular prevention is weak and needs further investigation.

Aldosterone and Left Ventricular Remodeling

Experimental and clinical evidence obtained in the last 2 decades clearly indicates that protracted exposure to inappropriately elevated aldosterone levels causes significant changes in left ventricular structure and function. Animal studies have demonstrated that aldosterone induces myocardial inflammatory changes and fibrosis in the presence of a high salt diet. Moreover, the effects of aldosterone on the heart have been investigated in different clinical conditions. These conditions include systolic and diastolic heart failure, essential hypertension, and primary aldosteronism that offers a unique clinical model to study the cardiac effects of excess aldosterone because these effects are isolated from those of the renin-angiotensin axis. A relatively clear picture is emerging from these studies with regard to aldosterone-related changes in left ventricular mass and geometry. Conversely, no direct effect of aldosterone on left ventricular diastolic function can be demonstrated and improvement of diastolic function obtained in some studies that have employed mineralocorticoid receptor blockers could result from left ventricular mass reduction. Animal experiments demonstrate that effects of aldosterone on the left ventricle require high salt intake to occur, but the evidence of this contribution of salt to aldosterone-induced cardiac changes in humans remains weaker and needs further research. The article reviews the results of clinical studies addressing the role of aldosterone in regulation of LV remodeling and diastolic function, and focuses on the possible relevance of salt intake.

Carotid artery stiffness is related to hyperinsulinemia and insulin-resistance in middle-aged, non-diabetic hypertensive patients

BACKGROUND AND AIMS

Glycometabolic abnormalities are frequently found in hypertension and could affect the mechanical properties of carotid arteries. The aim of the study was to investigate the relationship of glucose tolerance, plasma insulin, and insulin sensitivity with carotid distensibility in middle-aged, non-diabetic hypertensive patients free of cardiac and vascular complications.

METHOD AND RESULTS

In 93 patients with grade 1-2, uncomplicated, primary hypertension and 68 matched normotensive controls we measured plasma glucose and insulin at fast and after an oral glucose load (OGTT), calculated the HOMA-index as a marker of insulin sensitivity, and assessed distensibility of common carotid arteries by B-mode ultrasonography. Hypertensive patients were hyperinsulinemic and insulin-resistant as compared to normotensive controls. Hypertensive patients with impaired fasting glucose and/or impaired glucose tolerance had comparable distensibility of carotid arteries. Patients with decreased carotid distensibility were older and had higher body mass, fasting and post-OGTT plasma insulin, HOMA-index, and carotid IMT than the remaining patients, but no differences in glycated hemoglobin, and fasting or post-OGTT plasma glucose. Carotid coefficient of distensibility was inversely related and β-stiffness directly related with fasting and post-OGTT plasma insulin, and HOMA-index. Multivariate logistic regression showed that age and post-OGTT plasma insulin levels predicted carotid artery stiffening independent of body mass index, sex, blood pressure, and plasma glucose levels.

CONCLUSIONS

The study demonstrates that decreased insulin sensitivity and the related hyperinsulinemia but not hyperglycemia could contribute to carotid artery stiffening in middle-aged, non-diabetic hypertensive patients free of cardiovascular complications.

Aldosterone and the heart: from basic research to clinical evidence

Recent views suggest that long-term exposure to elevated aldosterone concentrations might result in cardiac, vascular, renal, and metabolic sequelae that occur independent of the blood pressure level. Indirect evidence of the untoward effects of aldosterone on the heart has been clearly established in clinical studies that have tested the effects of mineralocorticoid receptor antagonists in the treatment of systolic heart failure. As it has become clear in recent years, the interaction between aldosterone and the heart has to deal with additional actions of the hormone on specific cell types, cellular mechanisms, and molecules that are involved in regulation of tissue responses, leading to hypertrophy, remodeling, and fibrosis. The majority of these effects are mediated by activation of the mineralocorticoid receptors that are expressed in cardiomyocytes and cardiac fibroblasts, and mediate the genomic effects of the hormone. Evidence of interactions between aldosterone and the heart that occur independent of the renal effects of aldosterone, however, is not limited to the context of systolic heart failure and observations obtained in other disease states have led, together with findings of animal studies, to a better understanding of the potential benefits of aldosterone antagonists. In this narrative overview, we highlight the most recent findings that have been obtained in experimental animal models and in clinical conditions that include, in addition to systolic heart failure, primary aldosteronism, essential hypertension, diastolic heart failure, and arrhythmia.

Mineralocorticoid antagonists treatment versus surgery in primary aldosteronism

Recent evidence indicates a greater frequency of primary aldosteronism (PA) among patients with hypertension than the previously accepted prevalence. PA was once considered a relatively benign form of hypertension associated with low incidence of organ complications. Recent views, however, suggest that long-term exposure to increased aldosterone levels might result in cardiovascular, renal, and metabolic sequelae that occur independently of the blood pressure level. Cross-sectional comparisons with patients with essential hypertension have demonstrated that patients with PA are at higher risk of cardiovascular events, have more frequent left ventricular hypertrophy and diastolic dysfunction, have greater urinary albumin losses as a marker of a hemodynamic intrarenal adaptation, and are insulin resistant. Some of these findings have been corroborated by the results of short-term, follow-up studies where it was shown that unilateral adrenalectomy or treatment with mineralocorticoid receptor (MR) antagonists are effective in correcting hypertension and hypokalemia. Normalization of blood pressure and correction of hypokalemia, however, are not the only goals in managing PA and effective prevention of organ complications is mandatory in these patients. The relative efficacy of adrenalectomy and MR antagonists, in the long-term, on the cardiovascular, renal, and metabolic outcomes still needs evaluation, being the aldosterone-induced tissue damage the main factor that could justify the cost of increasing efforts in screening of disease and differentiation of subtypes. In this narrative review, we summarize the results obtained with either surgical or medical treatment of PA and outline the findings of long-term, prospective studies on the effects of treatment on cardiovascular and renal outcomes and on insulin sensitivity.

Relationship of plasma renin with a prothrombotic state in hypertension: relevance for organ damage

BACKGROUND

Components of the renin-angiotensin-aldosterone system (RAAS) and a prothrombotic state are predictors of cardiovascular events in hypertensive patients. A relationship between the RAAS and the coagulation/fibrinolytic systems has been demonstrated, but its clinical relevance in hypertension is unclear. We investigated the relationships of the RAAS and the hemostatic system with hypertensive organ damage.

METHODS

Plasma components of the RAAS and parameters that directly assess the activation of coagulation and fibrinolysis were measured in 247 essential hypertensive patients in whom the extent of organ damage had been characterized at the cardiac, renal, and vascular level.

RESULTS

Positive association with increasing plasma renin activity (PRA) was demonstrated for plasma fibrinogen, D-dimer, and plasminogen activator inhibitor-1 (PAI-1) levels. PRA was directly correlated with plasma aldosterone, fibrinogen, d-dimer, and PAI-1. The relationship of PRA with fibrinogen and PAI-1 remained significant after correction for age, gender, duration of hypertension, and smoking status. Plasma aldosterone levels were directly correlated with fibrinogen, D-dimer, and PAI-1, whereas plasma angiotensin-converting enzyme was not related with any of the coagulation parameters. Elevated PRA, aldosterone, fibrinogen, D-dimer, prothrombin fragment 1+2, and PAI-1 levels were associated with clinical and/or instrumental evidence of hypertension-related cardiac and renal damage. Both fibrinogen and PAI-1 were independent predictors of the presence of organ damage and their inclusion in a multivariate model eliminated PRA and aldosterone as independent predictors.

CONCLUSIONS

A strong and independent association exists between renin, aldosterone, and markers of a prothrombotic state in essential hypertension. This relationship might contribute to the development of hypertensive organ damage.

Cutting Balloon angioplasty for the treatment of haemodyalisis vascular accesses: midterm results

PURPOSE

The purpose of this study was to assess the effectiveness of Cutting Balloon angioplasty in the treatment of stenoses in haemodialysis arteriovenous accesses.

MATERIALS AND METHODS

Over the past 2 years, we have observed 80 patients with stenotic haemodialysis accesses; 24 of these (mean age 66.4 years, range 50-81) with 26 stenoses of 24 accesses (21 Cimino-Brescia fistulas and 3 dialysis loops) were selected for Cutting Balloon angioplasty. In 11 cases, the Cutting Balloon device was used after failure to dilate the access with a high-pressure balloon whereas in 15 cases (10 focal stenoses and 5 restenoses), it was used as a first choice. Two Cutting Balloon devices had a diameter of 8 mm, two of 7 mm, 11 of 6 mm, eight of 5 mm and one of 4 mm. The follow-up was performed by colour Doppler ultrasound (CDUS) and clinical assessment at 1, 3, 6, 12, 18 and 24 months.

RESULTS

In all patients, postprocedure angiography demonstrated immediate technical success. No periprocedural complications occurred. Follow-up examinations (range 3-24 months, mean 18.2 months) demonstrated patency of the vascular access and its good functioning during dialysis in 23/24 cases (95%). Only in one case did we observe a haemodynamically significant restenosis, which was treated again with Cutting Balloon angioplasty.

CONCLUSIONS

Cutting Balloon angioplasty is safe and effective in the treatment of haemodialysis access stenosis, especially in cases of severe stenosis, with low restenosis rate both in the short and medium term.

Identification of a new candidate locus for uric acid nephrolithiasis

Renal stone formation is a common multifactorial disorder, of unknown etiology, with an established genetic contribution. Lifetime risk for nephrolithiasis is approximately 10% in Western populations, and uric acid stones account for 5%-10% of all stones, depending on climatic, dietary, and ethnic differences. We studied a small, isolated founder population in Sardinia, characterized by an increased prevalence of uric acid stones, and performed a genomewide search in a deep-rooted pedigree comprising many members who formed uric acid renal stones. The pedigree was created by tracing common ancestors of affected individuals through a genealogical database based on archival records kept by the parish church since 1640. This genealogical information was used as the basis for the study strategy, involving screening for alleles shared among affected individuals, originating from common ancestors, and utilization of large pedigrees to obtain greater power for linkage detection. We performed multistep linkage and allele-sharing analyses. In the initial stage, 382 markers were typed in 14 closely related affected subjects; interesting regions were subsequently investigated in the whole sample. We identified two chromosomal regions that may harbor loci with susceptibility genes for uric acid stones. The strongest evidence was observed on 10q21-q22, where a LOD score of 3.07 was obtained for D10S1652 under an affected-only dominant model, and a LOD score of 3.90 was obtained using a dominant pseudomarker assignment. The localization was supported also by multipoint allele-sharing statistics and by haplotype analysis of familial cases and of unrelated affected subjects collected from the isolate. In the second region on 20q13.1-13.3, multipoint nonparametric scores yielded suggestive evidence in a approximately 20-cM region, and further analysis is needed to confirm and fine-map this putative locus. Replication studies are required to investigate the involvement of these regions in the genetic contribution to uric acid stone formation.

Changes in circulating levels of atrial natriuretic factor (ANF) during orthotopic liver transplantation in humans

Atrial natriuretic factor (ANF) is a 28 amino acid peptide secreted by the atrial cardiocytes. Clearance is via the lung (50%) and the liver (25%). The main stimulus to ANF secretion is atrial distension but vasoconstrictors, sympathetic stimulation, catecolamines and tachycardia are able to enhance its circulating blood levels. ANF blood concentrations were measured during orthotopic liver transplantation in six postnecrotic cirrhotic patients. Significant increases in ANF blood levels occurred at the end of the anhepatic phase (P < or = 0.02 vs baseline) associated with low cardiac filling pressures (P < or = 0.02 vs baseline) and increased systemic vascular resistances (P < or = 0.02 vs preanhepatic phase). Aldosterone blood levels showed a similar behaviour, increasing significantly (P > or = 0.001 vs baseline) at the end of the anhepatic phase. ANF fell after reperfusion of the graft and returned towards baseline values at the end of the procedure. Since most of the total body clearance of ANF is performed by the lungs, its sharp increase at the end of the anhepatic phase could be considered a counterregulatory response to vasoconstricting stimulation and to fluid-sparing mechanisms in the presence of relative hypovolaemia. Its decrease after reperfusion could be related to volume normalization and partly to the enhanced clearance performed by the newly grafted liver.

Medical prevention and treatment of urinary stones

Despite revolutionary developments in minimally invasive methods for the removal of stones in the last 15 years, the medical prevention of urinary stones remains very rewarding, due to the continual increase in the prevalence of nephrolithiasis in western countries, the high recurrence rate of the disease, its complications, discomfort and the costs of lithotripsy. Medical prevention is highly effective (50-95% efficacy in different series) and cost-convenient; its basic elements are appropriate metabolic evaluation, adequate hydration, "common sense" diet, and, in selected cases, drugs of proven efficacy. Clinical-metabolic evaluation should aim at the recognition of specific types of nephrolithiasis, and sort out secondary and/or remediable cases, define urinary risk factors, assess patients' compliance and the side effects of any therapy during follow-up. Hydration has proved effective in clinical trials and population-based observational studies; "fluids" may consist of water (any kind), coffee (caffeinated or decaffeinated), tea, beer and wine; grapefruit juice appears to have an unexplained ill effect. Despite the lack of clinical demonstration that dietary manipulations reduce the recurrences of stones, biochemical and epidemiological data suggest that high sodium, animal protein and sucrose intake increase the risk. Undue reductions in Ca intake also appear to be detrimental both for stone recurrences and bone mineralisation: "adequate" Ca intake (800-1000 mg/day) should be encouraged, but only in food since supplemental Ca, as drugs, appears to increase the risk of stones. Effective drugs are available for cystine, uric acid, infected stones and several secondary causes of Ca nephrolithiasis; in "idiopathic" Ca nephrolithiasis, thiazides, allopurinol, K and K-Mg citrate and possibly neutral K phosphate have been shown to be effective, at least in specific metabolic contexts.

Paracellin-1, a renal tight junction protein required for paracellular Mg2+ resorption

Epithelia permit selective and regulated flux from apical to basolateral surfaces by transcellular passage through cells or paracellular flux between cells. Tight junctions constitute the barrier to paracellular conductance; however, little is known about the specific molecules that mediate paracellular permeabilities. Renal magnesium ion (Mg2+) resorption occurs predominantly through a paracellular conductance in the thick ascending limb of Henle (TAL). Here, positional cloning has identified a human gene, paracellin-1 (PCLN-1), mutations in which cause renal Mg2+ wasting. PCLN-1 is located in tight junctions of the TAL and is related to the claudin family of tight junction proteins. These findings provide insight into Mg2+ homeostasis, demonstrate the role of a tight junction protein in human disease, and identify an essential component of a selective paracellular conductance.

Genotype-phenotype correlations in normotensive patients with primary renal tubular hypokalemic metabolic alkalosis

Among the different forms of hereditary renal tubulopathies associated with hypokalemia, metabolic alkalosis and normotension, two main types of disorders have been identified: Gitelman disease, which appears to be a homogeneous post-Henle's loop disorder, and Bartter syndrome, a heterogeneous Henle loop disorder. A specific gene has been found responsible for Gitelman disease, encoding the thiazide-sensitive Na-Cl cotransporter (TSC) of the distal convoluted tubule. From a phenotypic point of view the characteristic findings of this disease are hypocalciuria, hypomagnesemia and tetanic crises appearing during childhood or later. Many subjects are asymptomatic. At least three different genes have been shown to be responsible for Bartter syndrome, characterized by mutations in the proteins encoding respectively the bumetanide-sensitive Na-K-2Cl cotransporter, the inwardly-rectifying renal potassium channel and a renal chloride channel, all protein transports located in the ascending limb of Henle's loop. Mutations in the first two transport proteins have been demonstrated in patients with the hypercalciuric forms of Bartter syndrome associated with nephrocalcinosis (respectively Bartter syndrome type I and II), who were often born after pregnancies complicated by polyhydramnios and premature delivery. Mutations in the gene encoding a renal chloride channel were recently recognized in patients with a Henle tubular defect not associated with nephrocalcinosis (Bartter syndrome type III). Most of the latter group of patients were normo-hypercalciuric and presented dehydration and life-threatening hypotension in the first year of life. However, these three genes do not explain all the patients with Bartter syndrome which unlike Gitelman disease, appears to be a very heterogeneous disorder. Clearance studies, especially if done during furosemide and/or hydrochlorothiazide administration, have been helpful in identifying the site of tubular involvement. Considering both phenotypic and genotypic data, we propose a clinical-pathophysiological and molecular approach to diagnose the different tubulopathies associated with hypokalemic metabolic alkalosis.

Abnormal reabsorption of Na+/CI- by the thiazide-inhibitable transporter of the distal convoluted tubule in Gitelman's syndrome

Eleven patients with Gitelman's syndrome and 23 controls underwent acute administration of the thiazide diuretic hydrochlorothiazide and/or the loop diuretic furosemide (FUR) in order to indirectly evaluate the activity of the two electroneutral Na+/Cl(-)-reabsorptive systems of the distal nephron, namely the thiazide-sensitive Na+-Cl- symporter of the distal convoluted tubule and the FUR-sensitive Na+-K+-2Cl- symporter of the loop of Henle. The patients were characterized by hypokalemia, mild metabolic alkalosis, hypomagnesemia, hypocalciuria, and reduced free water generation during maximally diluted diuresis which indicated reduced distal nephron NaCl reabsorption. The plasma Na and Cl levels were similar in patients and controls. Hydrochlorothiazide induced a significantly lower increase of urinary Na and Cl excretions in 6 patients with Gitelman's syndrome than in 6 controls, indicating reduced NaCl reabsorption by the thiazide-sensitive Na+/Cl- symporter of the distal convoluted tubule in Gitelman's syndrome. FUR induced a slightly higher increase of urinary Na and Cl excretions in 11 patients with Gitelman's syndrome than in 17 controls, in keeping with reduced NaCl reabsorption in tubular sites past the loop of Henle during FUR effect or increased NaCl reabsorption in the loop itself (as a compensatory mechanism for NaCl-reabsorptive defect in the distal convoluted tubule) or both. Our results confirm that the functional activity of the renal thiazide-sensitive Na+-Cl- cotransporter (but not of the FUR-sensitive carrier) is deficient in patients with Gitelman's syndrome, in keeping with the recently described genetic link between the syndrome and a wide variety of nonconservative mutations of the gene encoding the protein; it is suggested that dynamic studies with diuretic administration may be of diagnostic help in this condition.

Novel molecular variants of the Na-Cl cotransporter gene are responsible for Gitelman syndrome

A hereditary defect of the distal tubule accounts for the clinical features of Gitelman syndrome (GS), an autosomal recessive disease characterized by hypokalemia, hypomagnesemia, metabolic alkalosis, and hypocalciuria. Recently, we cloned the cDNA coding for the human Na-Cl thiazide-sensitive cotransporter (TSC; also known as ¿NCCT¿ or ¿SLC12A3¿) as a possible candidate for GS, and Simon et al., independently, described mutations in patients with GS. Now, we show 12 additional mutations consistent with a loss of function of the Na-Cl cotransporter in GS. Two missense replacements, R209W and P349L, are common to both studies and could represent ancient mutations. The other mutations include three deletions, two insertions, and six missense mutations. When all mutations from both studies are considered, missense mutations seem to be more frequently localized within the intracellular domains of the molecule, rather than in transmembrane or extracellular domains. One family, previously reported as a GS form with dominant inheritance, has proved to be recessive, with the affected child being a compound heterozygote. A highly informative intragenic tetranucleotide marker, useful for molecular diagnostic studies, has been identified at the acceptor splice site of exon 9.

Pseudohyperkalemia in extreme leukocytosis

Spurious elevation of blood K levels is a well known occurrence in patients with extreme leukocytosis. A common explanation is the in vitro release of K from leukocytes undergoing lysis during the clotting process. Since in clinical practice blood electrolytes are now being evaluated in plasma or whole heparinized blood rather than in serum, this source of error should almost have disappeared. Another mechanism may be prolonged storage of blood at room temperature or in the cold before performing the test, most likely since unphysiological conditions and/or shortage of metabolic fuels may impair Na/K-ATPase activity in leukocytes, ensuing in K release from these cells. For these reasons, it is commonly advised that patients with extreme leukocytosis should have K levels determined on plasma samples that are separated promptly from the cellular elements. We have recently observed a case of pseudohyperkalemia in a patient with chronic lymphocytic leukemia which was unrelated to both of these mechanisms, and was instead related to a common mode of drawing blood, i.e. with vacuum tubes.

Lymphocytic intracellular pH and Na+/H+ exchanger activity in hemodialysis patients

We have evaluated intracellular pH (pHi) and Na+/H+ exchanger activity in peripheral lymphocytes from 16 patients on regular acetate hemodialysis. All the patients were taking oral NaHCO3 supplementation (30 mmol/day), to maintain predialysis arterial blood acid-base status within normal range (pH 7.36 +/- 0.02, PHCO3- 23.3 +/- 1.2 mM, pCO2 40.9 +/- 1.4 mm Hg). pHi was measured, using the fluorescent probe BCECF (2',7'-bis-carboxyethyl-5,6-carboxyfluorescein), both in nominal absence of bicarbonate (Hepes solution, pH 7.4; n = 10) and in the presence of HCO3-/CO2 buffer system (pH 7.4, [HCO3-] 25 mM, pCO2 40 mm Hg; n = 6). Predialysis pHi did not differ from controls when measured in the presence of HCO3-/CO2 (7.28 +/- 0.04 vs. 7.29 +/- 0.04, p = NS), but was lower in dialysis patients than in normal subjects (7.11 +/- 0.04 and 7.20 +/- 0.02, respectively; p < 0.05) when measured in Hepes solution. This suggested that bicarbonate-independent pHi regulation was abnormal in dialysis patients. To further characterize this abnormality of pHi regulation, lymphocytes were exposed to ethylisopropylamiloride, a specific Na+/H+ antiporter inhibitor, in Hepes solution; this maneuver induced a significantly lower decrement in pHi (0.04 +/- 0.04 vs. 0.15 +/- 0.03, p < 0.05) in dialysis patients than in controls, indicating reduced Na+/H+ exchanger activity in the patients. The rate of pHi recovery during the first 30 s after induction of various degrees of cell acidification (pHi range 6.2-7.0), which in the absence of HCO3-/CO2 is dependent on Na+/H+ exchanger activity, was also reduced in the patients as compared to controls (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of the tubuloglomerular feedback system in human subjects

It has been shown in animals that GFR decreases after administration of a carbonic anhydrase inhibitor (CAI) because of activation of the tubuloglomerular feedback. However, the magnitude of this response has never been studied in healthy subjects, nor has the possibility of inhibiting tubuloglomerular feedback with frusemide (FRU). Changes in CCr, V, CNa, CCl, CH2O, CLi were studied before and after acute administration of acetazolamide (ACZ) to 11 normal subjects or FRU to 9 normal subjects. Both ACZ and FRU increased V, CNa, CCl and CLi. Only FRU decreased CH2O. ACZ but not FRU decreased CCr, despite lesser increases of V, CLi and CH2O+CCl (rough indexes of distal delivery). The magnitude of the GFR decrease after comparable increases in distal delivery varied greatly between subjects. There was a tendency for the subjects with lower basal GFRs to show tubuloglomerular feedback responses of lesser magnitude than those with higher GFRs. These results show that it is possible to study tubuloglomerular feedback and its sensitivity in humans using CAIs. FRU blocks the tubuloglomerular feedback response. Its sensitivity appears to vary widely in normal subjects.

Correction of hypokalemia with antialdosterone therapy in Gitelman's syndrome

Six adult patients (4 females and 2 males, age range 26-57 years) with Gitelman's syndrome (GS) were treated with spironolactone 200-300 mg/day (n = 5) and/or amiloride 10-30 mg/day (n = 3) for 1-18 months. The patients had hypokalemia, hyperreninemia, chloride-resistant metabolic alkalosis, renal hypomagnesemia (n = 5), and hypocalciuria (n = 5). Free water clearance studies during maximal water diuresis and furosemide administration were suggestive of a solute reabsorptive defect beyond the loop of Henle. Antialdosterone therapy induced a significant increase of PK (from 2.6 +/- 0.4 to 3.4 +/- 0.4 mM; p < 0.0001) and a decrease of CK (from 21.4 +/- 13.2 to 10.6 +/- 4.8 ml/min, p < 0.02) and FEK (from 21.0 +/- 13.6 to 13.4 +/- 5.7%; p < 0.03); PMg increased from 1.38 +/- 0.38 to 1.64 +/- 0.21 mg/dl (p < 0.03) with a parallel fall of CMg (from 5.5 +/- 2.3 to 2.9 +/- 1.5 ml/min; p < 0.02) and FEMg (from 5.7 +/- 2.6 to 2.9 +/- 0.6%; p < 0.05); arterial blood pH and HCO3- did not change (P = plasma, C = clearance, FE = fractional excretion). The creatinine clearance fell (from 90.5 +/- 16.8 to 65.8 +/- 20.9 ml/min; p < 0.05), and Prenin rose (from 16.6 +/- 8.9 to 35.3 +/- 25.3 ng/ml/h; p < 0.02, as did Paldo (from 26.1 +/- 12.3 to 109 +/- 82.6 ng/dl; p < 0.01), indicating extracellular fluid volume contraction; however no significant clinical symptoms of hypovolemia ensued.(ABSTRACT TRUNCATED AT 250 WORDS)

Tetany and rhabdomyolysis due to surreptitious furosemide--importance of magnesium supplementation

Diuretics may induce hypokalemia, hypocalcemia and hypomagnesemia. While severe hypokalemia may cause muscle weakness, severe hypomagnesemia is associated with muscle spasms and tetany which cannot be corrected by potassium and calcium supplementation alone (1,2). Surreptitious diuretic ingestion has been described, mainly in women who are concerned that they are obese or edematous. Symptomatic hypokalemia has been reported in such patients (3-7) and in one case hypocalcemia was observed (8), but the effects of magnesium depletion were not noted in these patients.

Hypercalcaemia in Addison's disease: calciotropic hormone profile and bone histology

Three cases of hypercalcaemia secondary to acute adrenocortical insufficiency are described; all the patients had moderate to severe renal impairment, one being on chronic dialysis treatment with no residual diuresis. Parathyroid hormone (PTH) and 1,25 dihydroxyvitamin D [1,25(OH)2D] were low, indicating a suppressed PTH-vitamin D axis. In the two patients with partial renal impairment, urine Ca excretion was increased, indicating increased load of the cation into the extracellular fluid (ECF), most probably from bone. Saline infusion, to correct any ECF depletion and to increase urine Ca excretion, could not fully correct the hypercalcaemia. Complete correction of plasma Ca levels was observed shortly after the institution of hormonal substitutive therapy. Despite the evidence of increased Ca mobilization from bone, bone biopsies in two patients did not show any signs of cell-mediated bone resorption; instead, bone cell activity appeared to be suppressed. Thus, glucocorticoid deficiency appears to induce Ca mobilization from bone stores by mechanism(s) unrelated to bone remodelling processes.

Distal nephron function in Bartter's syndrome: abnormal conductance to chloride in the cortical collecting tubule?

Five patients with the clinical patterns of Bartter's syndrome underwent a series of clearance studies in order to characterize the underlying tubule defect. Free water generation during maximal water diuresis (CH2O), expressed as percentage of the distal delivery (CH2O + CCl), was lower in the patients (72.5 +/- 3.2%) than in controls (84.4 +/- 5.5, p < 0.0001). During maximal water diuresis and furosemide administration (40 mg i.v. as bolus), NaCl reabsorption along the diluting nephron segments could be separated into 2 components, that occurring in the loop of Henle (DRNaHL) and that occurring in tubule segments beyond the macula densa (DRNaDT): DRNaHL was normal, while DRNaDT was reduced (3.1 +/- 0.8 vs. 6.2 +/- 2.5 ml/min in controls, p < 0.015). Thus, according to this furosemide protocol, our patients had normal solute reabsorption in the loop of Henle but reduced NaCl reabsorption in tubule segments beyond the macula densa. During 0.9% saline infusion (2 liters in 2 h, after stimulation of distal Na reabsorption with fludrocortisone) fractional excretion (FE) of K showed a linear rise with the increase of FECl-FEK, however, was much higher in the patients than in controls for every FECl level. In contrast, the infusion of Na2SO4, after fludrocortisone administration, induced similar FEK increases in patients and in controls. Thus, in these patients Na reabsorption in the distal nephron (possibly the cortical collecting tubule) was associated with the generation of a higher than normal electric potential gradient in the presence of Cl but not of another poorly reabsorbable anion, such as SO4(2-). These observations indicate that, in our patients, Henle's loop function is normal, while the collecting tubule function is abnormal. We suggest that NaCl wasting and enhanced tubular secretion of H+ and K in our patients might result from an abnormally low conductance to Cl in distal nephron site(s) where Na reabsorption is electrogenic, possibly the cortical collecting tubule. A larger than normal transtubular electric gradient would be generated by Na reabsorption, causing: (1) a direct stimulation of tubular secretion of K and H+ (leading to hypokalemia and alkalosis) and (2) inhibition of the reabsorption of Na ('trapped' into the tubular lumen by electric forces), with consequent extracellular volume contraction, hyperreninemia and hyperaldosteronism.

Cardiac arrhythmias and electrolyte changes during haemodialysis

Cardiac arrhythmias are a frequent event in chronic haemodialysis patients, and their pathogenesis is still poorly understood. We evaluated plasma K+ (PK), intraerythrocytic K+ (EK) and acid-base changes during haemodialysis in six patients with frequent arrhythmias (A-pts), and in six (used as controls) nonarrhythmic dialysis patients (C-pts). PK decreased significantly (P less than 0.01) during haemodialysis in both groups: A-pts (pre HD: 4.81 +/- 0.52 mM; 1st hour: 3.66 +/- 0.44; end HD: 3.17 +/- 0.38) and C-pts (4.75 +/- 0.80; 3.71 +/- 0.32 and 3.18 +/- 0.18 respectively) without any significant difference at any time between the two groups. Predialysis arterial pH and HCO3 were similar in A-pts (7.33 +/- 0.07 and 22.1 +/- 4.5 mM) and C-pts (7.29 +/- 0.04 and 19.7 +/- 2.6 mM) but an apparently better correction of acidosis within the treatment was seen in A-pts (arterial pH 1st hour: 7.38 +/- 0.07; end HD: 7.39 +/- 0.07) than C-pts (1st hour: 7.31 +/- 0.02, P less than 0.05 versus A-pts; end HD: 7.33 +/- 0.03, P less than 0.05 versus A-pts). EK was significantly (P less than 0.01) greater at all times in C-pts (pre HD: 90.6 +/- 15.7 mmol/l RBC; 1st hour: 93.3 +/- 11.7; end HD 96.6 +/- 10.7) than A-pts (72.1 +/- 9.0; 77.2 +/- 3.7 and 79.3 +/- 8.4, respectively). We conclude that haemodialysis patients with arrhythmias have a decreased intraerythrocytic K content in comparison with other patients despite similar PK values; this finding might constitute a predisposing factor for arrhythmias.

Pseudo-Bartter's syndrome from surreptitious diuretic intake: differential diagnosis with true Bartter's syndrome

Five patients with pseudo-Bartter's syndrome from surreptitious diuretic abuse were compared with six patients with true Bartter's syndrome, diagnosed as a normotensive, hyperreninaemic, hypokalaemic metabolic alkalosis with normal urine chloride excretion, low CH2O/(CH2O+CCl) ratio during maximal water diuresis and negative urine screen for diuretics. The latter was positive for frusemide in four and for hydrochlorothiazide in the remaining pseudo-Bartter's patients. The two groups of patients did not differ as for plasma Na+, Cl-, K+, HCO3-, renin, and aldosterone, while uric acid and Mg2+ were greater in pseudo-Bartter's patients. Daily and fasting urine Na+, Cl- and K+ excretion were less in pseudo-Bartter's patients; however, there was substantial overlap of values between the two groups. Fractional distal solute reabsorption during maximal water diuresis was low in the six patients with Bartter's syndrome and in two pseudo-Bartter's patients; thus, this parameter could not be taken as a specific diagnostic marker of Bartter's syndrome. Frusemide administration, 40 mg i.v., induced a brisk increase of urine flow (11.7-21.8 ml/min), UOsm (148-186 mOsm/kg H2O) and FENa (14.6-24%) in Bartter's syndrome, but not pseudo-Bartter's patients; in all pseudo-Bartter's patients frusemide-induced changes of UOsm (13-97) and FENa (-0.5 to 10.2) were markedly less than in Bartter's syndrome patients. Frusemide resistance in pseudo-Bartter's patients was most probably related to diuretic-induced ECF volume contraction and increased proximal tubule solute reabsorption; in fact fractional lithium clearance (FELi, a marker of post-proximal solute delivery) was low in pseudo-Bartter's, but not in Bartter's syndrome patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acute administration of acetazolamide and frusemide on lithium clearance in humans

To investigate the mechanism(s) of acute frusemide-induced increases in FELi, the effects of frusemide and acetazolamide, the carbonic anhydrase inhibiting agent, were evaluated in 19 healthy subjects either before or after pretreatment with acetazolamide or frusemide (11 subjects and eight subjects respectively). Acetazolamide pretreatment did not modify frusemide-induced increases in FELi (delta FLi 12.8 +/- 4.1% compared to 14.6 +/- 7.3%, P = NS); similarly, frusemide pretreatment did not modify acetazolamide-induced increases in FELi (delta FLi: 11.3 +/- 5.9% compared to 9.8 +/- 3.8%, P = NS). Acetazolamide-induced changes of FELi were correlated significantly with acetazolamide-induced increases of FEHCO3 (r = 0.61, P less than 0.05), FENa (r = 0.46, P less than 0.05) but not of FECl (r = 0.25, P = NS). On the other hand, frusemide-induced changes of FELi were correlated significantly with frusemide-induced increases of FENa (r = 0.62, P less than 0.005), FEC1 (r = 0.52, P less than 0.025) but not of FEHCO3 (r = 0.3, P = NS). Thus, frusemide effects on tubular lithium reabsorption are not related to carbonic anhydrase inhibition; furthermore, it appears that frusemide and acetazolamide affect lithium reabsorption by different and independent mechanism(s), possibly acting at different nephron site(s).