Pulmonary gas exchange during hemodialysis and peritoneal dialysis: interaction between respiration and metabolism

Pulmonary infectious mortality among patients with end-stage renal disease

BACKGROUND

Infection is the second-leading cause of death among patients with end-stage renal disease (ESRD). This is due in part to advanced age, comorbid conditions, and immune dysfunction observed in uremic states. Although one may hypothesize that pulmonary infectious mortality is higher among patients with ESRD compared with the general population (GP), no such data are currently available.

METHODS

We compared annual pulmonary infectious mortality rates among patients with ESRD to those in the GP. The data were abstracted from the United States Renal Data System and the National Center for Health Statistics, respectively, and were stratified by age, gender, race, and presence or absence of diabetes mellitus (DM). In the GP, primary and multiple cause-of-death analyses were performed to account for potential limitations of the data sources.

RESULTS

Overall, pulmonary infectious mortality rate was 14-fold to 16-fold higher in dialysis patients and approximately twofold higher in renal transplant recipients compared with the GP. After stratification for age, differences between groups decreased but retained their magnitude.

CONCLUSION

Patients with ESRD treated with dialysis have higher pulmonary infectious mortality rates compared with the GP, even after stratification for age, race, and DM. Consequently, this patient population must be considered at high risk for the development of lethal pulmonary infections.

Effects of haemodialysis on pulmonary clearance of Tc-99m diethylene triamine pentaacetate (DTPA)

OBJECTIVES

Hypoxaemia occurring during haemodialysis has long been known. Several mechanisms in the pathogenesis have been proposed. The present study was conducted to test whether changes in pulmonary alveolar permeability were among the operating mechanisms.

MATERIALS AND METHODS

Twenty haemodialysis patients (12 male, 8 female) were included in the study. The mean age was 49 years (age range: 18-85 years). Patients with known pulmonary disease, current smokers and those gaining more than 1 kg weight during the interdialytic period were excluded. Complete blood count, arterial blood gas analysis, pulmonary function tests and Tc-99m diethylene triamine pentaacetate (DTPA) inhalation scintiscan were carried out before and after haemodialysis. A bronchial provocation test was carried out after each session. A postero-anterior chest radiogram was taken for each patient.

RESULTS

When the results before and after haemodialysis were compared, it was observed that the pH and serum bicarbonate levels, haemoglobin and haematocrit values were significantly higher after haemodialysis. However, the platelet count was found to be decreased significantly. Bronchial hyperreactivity, tested by metacholine, Was positive in 5 of 19 patients (26%). No correlation between bronchial hyperreactivity and other factors could be identified. No significant difference was observed in pulmonary Tc-99m DTPA clearance after haemodialysis. All chest radiograms were interpreted to be within normal limits.

CONCLUSIONS

Since we observed no hypoxaemia following haemodialysis, we cannot comment as to whether the changes in pulmonary clearance play a role in the pathogenesis of haemodialysis-associated hypoxaemia. In order to reach reliable conclusions, additional studies are needed.

Thoracic complications in uremic patients and in patients undergoing dialytic treatment: state of the art

No organ in the chest is spared the negative effects of uremia. The dialytic treatment itself is often associated with a large array of thoracic complications. We review the main thoracic manifestations of the terminal uremia from the radiological point of view, such as: uremic pleuritis and pericarditis, uremic pneumonia, renal osteodystrophy, infections, and metastatic pulmonary calcifications. Respiratory function derangement and the problems related to peritoneal dialysis and hemodialysis are discussed in some detail, along with the diagnostic role of plain films, US, nuclear medicine, and CT. The main focus of this review is on the hydration problems and pulmonary edema, often related to a large number of pathogenetic factors. Based on our experience, we think that the chest X-ray is not able to accurately discriminate between cardiogenic edema and fluid overload edema (so-called renal pulmonary edema). The radiological findings of the thoracic complications in uremic patients are multiple and complex but, in most cases, the imaging techniques may offer an accurate and noninvasive diagnostic approach, with a high benefit-cost ratio.

A review of continuous renal replacement therapy

Patients in the Intensive Care Unit commonly develop acute renal failure (ARF). The kidneys are rarely the only organs failing in these patients. Frequently ARF is part of multiple organ dysfunction syndrome. The choice of dialytic therapy should consider, not only the efficacy of the therapy, but also the undesirable effects such therapy may have on the other failing organs. Intermittent Haemodialysis and Peritoneal Dialysis were the conventional forms of dialysis available. Both are associated with complications which may make them unsuitable for use in the haemodynamically unstable, hypercatabolic patients, seen in the Intensive Care setting. Continuous Renal Replacement Therapy (CRRT) has been introduced in many Intensive Care Units to provide a more stable, flexible form of dialysis. The purpose of this article is to give an overview of the various forms of CRRT and to discuss the advantages of this form of therapy.

Pulmonary function in children with chronic renal failure

Lung volumes were measured in 45 children with chronic renal failure and compared to 10 healthy controls. Six patients were receiving conservative treatment (CT), 11 were undergoing regular haemodialysis (HD), 8 were on continuous ambulatory peritoneal dialysis (CAPD) and 20 were post transplantation (TP). We measured vital capacity (VC) and forced expiratory volume in 1 s (FEV-1) with a bell spirometer. In addition residual volume (RV) was determined in CAPD patients. VC and FEV-1 values below the lower limit of predicted normal values from healthy children with the same body height were found in 38% and 52% of all patients respectively (P less than 0.05). Median values of VC and FEV-1 were lowest in CT and highest in TP patients. Median FEV-1 was significantly reduced to 79% of predicted values in CT and to 82% in HD patients (P less than 0.05). No correlation was found between FEV-1 and haemoglobin levels or the concomitant use of beta-blocking agents. During a HD session mean FEV-1 increased significantly. In CAPD patients the routine filling of the abdomen was followed by an 11% decrease of RV (non significant) while the other parameters remained stable. It is concluded that lung volumes are frequently reduced in chronic renal failure but remain essentially stable during the dialysis procedures.

Effect of uremia and its treatment on pulmonary function

Alterations in respiratory drive, mechanics, muscle function, and gas exchange are frequent if not invariable consequences of uremia. Pulmonary dysfunction may be the direct result of circulating uremic toxins or may result indirectly from volume overload, anemia, immune suppression, extraosseous calcification, malnutrition, electrolyte disorders, and/or acidbase imbalances. The pulmonary system is unique because it is affected by the disease and its treatment. Acetate hemodialysis reduces alveolar ventilation and PaO2 due to extrapulmonic CO2 unloading. Peritoneal dialysis increases alveolar ventilation and intraperitoneal pressure. The latter leads to an elevated and lengthened diaphragm, a reduced functional residual capacity, basilar atelectasis, possible hypoxemia, and altered respiratory muscle function. In patients on chronic peritoneal dialysis, adaptations may occur that limit the reductions in lung volumes, PaO2, and respiratory muscle strength that are often observed during acute peritoneal dialysis. This review details how uremia and dialysis interact to alter pulmonary function.

Extracorporeal treatment of acute renal failure in the intensive care unit: a critical view

Acute renal failure in critically ill patients is seldom an isolated problem but is more usually associated with multiple organ failure. When choosing an extracorporeal kidney replacement therapy, these other failing organs must be taken into account. Therefore the choice of an artificial kidney in patients requiring intensive care depends on both the efficacy of the technique and its possible adverse effects on cerebral, pulmonary and cardiovascular function. The most important pathogenic factors in the development of dysequilibrium syndromes, arterial hypoxemia and hypotension are treatment timing, diffusive solute transfer, bio-incompatible membranes and some specific dialysate components (buffer, electrolyte concentrations). It is important to understand the mechanisms by which these factors exert their adverse effects. Application of these pathophysiological mechanisms to the cardiopulmonary and neurologic status of the individual patient permits the prediction of their clinical outcome. This approach will lead to individualised treatment selection, thereby avoiding deleterious side-effects without loss of efficacy.

Hypoxemia during hemodialysis: a critical review of the facts

The literature describing the fall in PaO2 during dialysis is intensively and critically reviewed. This phenomenon is related to both the type of membrane used (cellulosic v noncellulosic membrane), and to the composition of the dialysate (acetate v bicarbonate). It appears that a ventilation/perfusion mismatch due to pulmonary leukostasis can, in part, explain hypoxemia in patients dialyzed with cellulosic membranes. This phenomenon is especially apparent in patients with preexisting pulmonary abnormalities. However, hypoventilation remains the major cause of hypoxemia. This hypoventilation is mainly due to CO2 consumption during acetate metabolism (acetate dialysis), or alkalinization of the blood (bicarbonate dialysis). The metabolic consequences of acetate metabolism, and of bicarbonate and CO2 losses through the dialyzer are critically analyzed. The cause for the increment in oxygen consumption during acetate dialysis is examined. Finally, the respective role of these combined factors are described and used to explain the changes in VCO2, VO2, respiratory quotient (RQ), and PaO2 reported in the literature during dialysis against acetate and/or bicarbonate.