Thiazolidinediones expand body fluid volume through PPARgamma stimulation of ENaC-mediated renal salt absorption

Thiazolidinediones (TZDs) are widely used to treat type 2 diabetes mellitus; however, their use is complicated by systemic fluid retention. Along the nephron, the pharmacological target of TZDs, peroxisome proliferator-activated receptor-gamma (PPARgamma, encoded by Pparg), is most abundant in the collecting duct. Here we show that mice treated with TZDs experience early weight gain from increased total body water. Weight gain was blocked by the collecting duct-specific diuretic amiloride and was also prevented by deletion of Pparg from the collecting duct, using Pparg (flox/flox) mice. Deletion of collecting duct Pparg decreased renal Na(+) avidity and increased plasma aldosterone. Treating cultured collecting ducts with TZDs increased amiloride-sensitive Na(+) absorption and Scnn1g mRNA (encoding the epithelial Na(+) channel ENaCgamma) expression through a PPARgamma-dependent pathway. These studies identify Scnn1g as a PPARgamma target gene in the collecting duct. Activation of this pathway mediates fluid retention associated with TZDs, and suggests amiloride might provide a specific therapy.

Effects of Ketamine on Serum and Tracheobronchial Aspirate Interleukin-6 Levels in Infants Undergoing Cardiac Surgery

OBJECTIVE

Corrective surgery for congenital heart defects in children frequently requires cardiopulmonary bypass (CPB). Serum and bronchoalveolar levels of interleukin-6 (IL-6) may be useful in assessing the severity of the systemic inflammatory response after CPB. In the present study, the authors aimed to compare the effects of ketamine anesthesia and isoflurane anesthesia with respect to serum and tracheobronchial aspirate (TBA) IL-6 levels in infants undergoing CPB for cardiac surgery.

DESIGN

Prospective and randomized controlled study.

SETTING

University-based teaching hospital.

PARTICIPANTS

Thirty-four infants aged 2 to 24 months were randomized into 2 groups.

INTERVENTIONS

In group K (n = 17), anesthesia was induced with intravenous (IV) ketamine, 1 to 2 mg/kg, and fentanyl, 1 to 2 microg/kg, and was maintained with infusions of ketamine, 25 to 75 microg/kg/min, and fentanyl, 10 microg/kg/h. In group I (n = 17), induction was achieved with IV thiopental sodium, 3 to 5 mg/kg, and fentanyl, 1 to 2 microg/kg, and was maintained with 1% isoflurane and fentanyl, 10 mug/kg/h. Blood and TBA samples were obtained at 6 and 4 stages, respectively.

MEASUREMENTS AND MAIN RESULTS

Serum IL-6 and TBA IL-6 levels were similar in the 2 groups at all stages (p > 0.05).

CONCLUSION

The present results show that ketamine anesthesia does not provide superiority over isoflurane anesthesia with respect to serum and TBA IL-6 levels.

The effectiveness of long-acting penicillin (penidur) in preventing recurrences of dermatolymphangioadenitis(DLA) and controlling skin, deep tissues, and lymph bacterial flora in patients with "filarial" lymphedema

Dermatolymphangioadenitis (DLA) is a common and serious complication of so-called "filarial" and bacterial non-filarial lymphedema of the limb, affecting skin, lymphatics and lymph nodes. In our previous studies, we demonstrated that more than 60% of patients revealed presence of bacterial isolates in deep tissues, tissue fluid and lymph from the lymphedematous limbs. The question remained open whether elimination or suppression of bacteria dwelling in lymphedematous tissues by administration of low doses of penicillin for long time periods would prevent recurrence of DLA attacks. In this study, we retrospectively evaluated a self/community-selected group of patients with lymphedema of the lower limbs with respect to the efficacy of long-acting penicillin in preventing episodes of DLA. There were no microfilariae or anti-filarial antibodies detected in the investigated group. The questions we asked were: (a) how effective is the benzathine penicillin in preventing recurrences of DLA attacks and (b) how does its long-term administration influence the bacterial spectrum of leg skin, deep tissues, lymph and lymph nodes and sensitivity to antibiotics. Two randomly selected groups of patients, receiving and not receiving penicillin during the same period of time, were compared. Evidently lower recurrence rate of DLA was observed in the treated group (p < 0.002). There was increased prevalence of cocci and gram-positive bacilli with a concomitant decrease of gram-negative bacilli on the foot and calf skin surface. Simultaneously, decreased prevalence of gram-positive cocci and gram-negative bacilli isolates in limb deep tissues and lymph was seen. No resistance to penicillin and other tested antibiotics developed in isolates from the skin surface, deep tissues and lymph. We conclude that long-lasting penicillin is effective in preventing recurrent DLA attacks.

Thiazolidinediones, peripheral oedema and congestive heart failure: what is the evidence?

Cardiovascular disease is the most common complication of type 2 diabetes mellitus (type 2 DM), accounting for approximately 80% of deaths. While atherosclerotic vascular disease accounts for much of the cardiovascular morbidity and mortality among diabetic patients, congestive heart failure (CHF) is another key complication associated with diabetes, with an incidence three to five times greater in diabetic patients than in those without diabetes. One of the most promising developments in the treatment of type 2 DM has been the introduction of the thiazolidinedione (TZD) class of drugs, which appear to have pleiotropic effects beyond glycaemic control. Enthusiasm has been tempered, however, by concerns for safety in patients with CHF, given reports of worsening heart failure symptoms and peripheral oedema. With the growing epidemic of type 2 DM and the increasing use of TZDs, such concern has important therapeutic implications for a population of patients with a high prevalence of often subclinical systolic and diastolic dysfunction. This review provides an overview of the currently available data regarding the effects of TZDs on fluid retention and cardiac function. Particular emphasis is placed on the mechanisms of development of peripheral oedema and its significance in patients with impaired left ventricular function. TZDs are well known to cause an expansion in plasma volume; there has also been concern that TZDs may have direct toxic effects on the myocardium, leading to impaired cardiac function. Studies to date do not support this hypothesis and in fact there is growing evidence from animal models and human trials that treatment with TZDs actually improves cardiac function. There are also preclinical data to suggest TZDs may protect the myocardium in the setting of ischaemic insult or the toxic effects of myocardial lipid deposition. Ongoing clinical trials examining the use of these agents in patients at risk for heart failure will probably provide further insight into the aggregate cardiovascular effects of this promising class of medications.

Effect of Metoclopramide on Gastric Fluid Volumes in Diabetic Patients Who Have Fasted before Elective Surgery

Background

Diabetes-induced gastroparesis is believed to increase fasting gastric fluid volume before elective surgery. Metoclopramide is routinely administered preoperatively to reduce gastric fluid volume in these patients. This study compared nondiabetic controls to non-insulin-dependent and insulin-dependent diabetics to determine the effect of metoclopramide, administered before surgery, on gastric volumes in patients who fasted before surgery.

Methods

Control and diabetic patients fasted preoperatively before receiving either placebo or 10 mg intravenous metoclopramide 20 min before induction of anesthesia. After intubation, a gastric tube was placed, and stomach contents were aspirated with volumes compared among the groups.

Results

Both groups of diabetic patients were older than the control group, and insulin-dependent patients had a higher incidence of comorbidities compared with the non-insulin-dependent group. Fasting blood sugar and hemoglobin A1C values were higher in both insulin-dependent and non-insulin-dependent patients. Gastric fluid volumes were similar in control, non-insulin-dependent, and insulin-dependent patients (8.0 +/- 2.6 vs. 9.6 +/- 4.1 vs. 17.7 +/- 2.5 ml, respectively). In insulin-dependent diabetic patients, metoclopramide decreased gastric volume compared with placebo treatment (17.7 +/- 2.5 vs. 7.8 +/- 2.9 ml; P = 0.027). After stratification, a subpopulation of patients with poorly controlled diabetes, regardless of type, were identified to have increased gastric residual volumes.

Conclusion

In elective surgical patients who have fasted before surgery, gastric volumes are minimal, even in diabetics with severe neuropathic symptoms. Metoclopramide prophylaxis to reduce gastric volumes seems to be unnecessary unless the patient has a prolonged history of poor blood glucose control.

Fluid Matters in Choosing Antihypertensive Therapy: A Hypothesis That the Data Speak Volumes

Assuming that blood pressure is lowered equivalently, diuretics are more effective than angiotensin-converting enzyme inhibitors (ACEIs), calcium channel blockers (CCBs), and alpha-adrenergic receptor blockers (alpha-blockers) at preventing heart failure, and they are more effective than ACEIs and alpha-blockers at preventing strokes. Compared with beta-adrenergic receptor blockers (beta-blockers) and ACEIs, CCBs are less effective at reducing myocardial infarcts and heart failure. There is currently no conceptual framework by which to organize data indicating that some antihypertensive medications are better than others at preventing cardiovascular diseases. The thesis of this article is that the fluid reduction or fluid retention attributable to antihypertensive medications, either alone or in combination, provides a basis for ranking these medications. Diuretics have a theoretical advantage compared with other antihypertensive medications because they reduce total body fluid more than other agents. Therefore, they are the preferred drugs for treating hypertension. The other antihypertensive agents that promote fluid reduction, ACEIs and angiotensin receptor blockers (ARBs), are next in preference, ranking a close second to diuretics. Because beta-blockers have a neutral effect on total body fluid, they rank on a third tier of preference, after ACEIs and ARBs. CCBs and alpha-blockers are the least preferred medications for treating hypertension because they promote fluid retention.

Epidural anaesthesia with bupivacaine does not cause increased oedema in small gut anatomoses in pigs

BACKGROUND AND OBJECTIVE

Epidural analgesia is widely used for abdominal surgery due to the properties of 'stress-free' anaesthesia and superior pain control. Nevertheless, sympathomimetics are known to antagonize inflammation. The present study was performed to investigate if epidural local anaesthetics caused increased local oedema formation.

METHODS

Thirty Dansk Landrace pigs were randomized into three groups: epidural bupivacaine, epidural morphine or intravenous (i.v.) fentanyl. All animals were anaesthetized with isoflurane and i.v. midazolam and received an identical fluid regimen. Six small bowel resections were performed over a 3-h period and during the following 3 h the anastomoses were resected. Primary end-points were water content in small bowel and mesentery samples before and after gut anastomosis, lymph flow and urine production.

RESULTS

The water content in the small bowel samples was not changed by surgery or by the different anaesthetic protocols. In the mesenteric tissue, there was a highly significant increase in water content of the postanastomotic samples compared to pre-anastomotic samples (P < 0.001) and a significant time treatment interaction was revealed (P < 0.05) suggesting an increase in oedema formation in the epidural local anaesthetic group. Lymph flow did not change during the experiments and there were no significant differences between the groups (P = 0.80). The mean total urine output was 44% higher in the epidural morphine group compared to the local anaesthetic group (P = 0.17).

CONCLUSIONS

Surgery did not increase gut wall water content, but acute oedema formation resulted in the peri-resectional mesenterial tissue, more prominently so in the bupivacaine group.

Voltammetric study of danazol and its determination in capsules and spiked biological fluids

The voltammetric behaviour of danazol DZ (antigonadotropin) was studied using cyclic voltammetry, direct current, differential pulse polarography (DPP) and alternating current polarography. Danazol exhibited irreversible cathodic waves over the pH range of 1-5 in Britton Robinson buffers. At pH 1 (the analytical pH), a well-defined wave with E1/2 of -1.04 V versus Ag/AgCl reference electrode was obtained. The diffusion current constant (Id) was 4.8+/-0.14 microA.L.m mole(-1) and the current-concentration plot was rectilinear over the range from 5 x 10(-6) to 1 x 10(-4) M with correlation coefficient (n = 11) of 0.995. The calculated detection limit was 1 x 10(-6) M using the DPP mode. The wave was characterized as being irreversible, diffusion-controlled although adsorption phenomenon played a limited role in the electrode process. The proposed method was applied to commercial capsules and the average percentage recovery was in agreement with that obtained by the official USP method. The method was extended to the in vitro determination of DZ in spiked human urine and plasma samples, the percentage recoveries were 96+/-4 and 97+/-5, respectively. A proposal of the electrode reaction was postulated.

Peptide metabolism and the control of body fluid homeostasis

In this paper, we review our current understanding of the medicinal chemistry of the major peptide systems, which influence body fluid homeostasis. Electrolytes play pivotal roles in intra- and intercellular communication, acid-base equilibrium and, when bound to several macromolecules, they regulate a myriad of enzymatic proteins, receptors and transcription factors. Cell turgor influences the plasma membrane, which activates mechanically-gated ion channels or mechanoreceptors, and the expression of a number of genes which underlie long-term metabolic responses to hormones, substrates and reactive oxygen intermediates. The altered kinetics and enzymatic cleavage of peptides during water-electrolyte imbalance can contribute to cardiac and renal damage associated with elevated blood pressure. Identification of the enzymes which are responsible for cleavage, together with emerging information about the mechanisms of action and structures of regulatory and effector peptides, has laid a foundation for the discovery of novel drugs, some of which are in use or are now undergoing evaluation in experimental trials. The development of models of hydrosaline challenge with relative efficiency to induce selective water-electrolyte imbalance has permitted the identification of kallikrein-kinin, renin-angiotensin-aldosterone, vasopressin-oxytocin, thyrotropin-releasing hormone and luteinizing hormone-releasing hormone as susceptible substrates. At present, the angiotensin-I converting enzyme inhibitors are well-known efficacious, orally active, blood pressure-lowering agents which have been used in hypertensive patients. In addition to several new analogues of this class of drug, some selective dual inhibitors of angiotensin-I converting enzyme and neutral endopeptidase and inhibitors of aminopeptidases are now also being rationally assayed and their beneficial effects on hypertension and hydromineral balance indicate that this type of drug may have powerful therapeutic effects for disorders of body fluid homeostasis.

Hydration of an amphiphilic excipient, Gelucire® 44/14

The incorporation of drugs into Gelucires has been reported to increase the dissolution rate of poorly soluble drugs, often leading to improved drug bioavailability. In pharmaceutical applications, it is important to know how the excipient interacts with the drug, and how the mixture behaves during manufacturing, storage as well as during administration. The uptake of water by an amphiphilic excipient, Gelucire 44/14, has been investigated in two ways: storage in humid air and addition of liquid water. During exposure to humid air, the uptake goes in stages that correspond to the dissolution of the components of the excipient, starting with the most hydrophilic ones: glycerol, then polyethylene glycol (PEG), PEG esters (PEG monolaurate and PEG dilaurate), and finally glycerides (trilaurin). At each stage, the remaining crystals are in equilibrium with an interstitial solution made of water and the dissolved components. In this range of hydrations, the total uptake is close to the sum of the equilibrium hydrations of the components. In the pharmaceutical formulation, the active ingredient could dissolve in the liquid phase. At larger hydrations, obtained through addition of liquid water, the state of Gelucire 44/14 differs from those of its components. Gelucire 44/14 forms a lamellar phase and this phase melts at 30 degrees C whereas the pure PEG esters form hexagonal and cubic mesophases. The cubic mesophases do not melt until the temperature exceeds 40 degrees C. At body temperature, all crystals in Gelucire 44/14 melt to an isotropic fluid as soon as the total water content exceeds 5%. Therefore the formulation of amphiphilic excipients can be optimized to avoid the formation of mesophases that impede dissolution of the excipient at body temperature.

Practical limitations of disinfection of body fluid spills with 10,000 ppm sodium hypochlorite (NaOCl)

The purpose of this study was to monitor disinfection with 10,000 ppm sodium hypochlorite for decontamination of common hospital spills. Simulated spills deliberately contaminated with 10(8) bacterial challenges were used for the study. Results showed greater than 5 log reduction in the challenge bacteria for all spills (serum, pus, sputum, csf, ascitic fluid, urine, and stool) except blood. Disinfection was satisfactory for blood contaminated with gram-negative bacteria, but not for staphylococci. As a practical procedure, surfaces contaminated from gross spillage of human body fluids should first be contained with absorbent materials, then disinfected with hypochlorite.

Effects of prolonged copper exposure in the marine gulf toadfish (Opsanus beta). I. Hydromineral balance and plasma nitrogenous waste products

Acute (96 h) and prolonged (30 days) copper exposure induced osmoregulatory disturbance and impaired nitrogenous waste excretion in the marine teleost, the gulf toadfish (Opsanus beta), which was found to be extremely tolerant to acute copper exposure with a 96 h LC50 exceeding 340 microM but exhibited disturbed mineral balance in response to both acute and prolonged exposure to approximately 12 microM copper. The main cause of copper toxicity was found to be Na+ and Cl- regulatory failure leading to elevated plasma [Na+] and [Cl-] and osmolality which in turn led to fluid loss from muscle tissue. Analysis of intestinal fluid composition revealed a complicated pattern of effects of copper exposure. Intestinal transport physiology was directly influenced by copper exposure with Cl- absorption being the most sensitive parameter. Evidence for increased Na+ and fluid absorption when the fish exhibited elevated plasma osmolality indicates that the intestine may also exhibit a compensatory response to impairment of branchial transport processes, suggesting at least two target organs (gill and intestine) for copper toxicity in marine fish. Plasma Mg2+ was elevated from approximately 1.5 mM to as much as 4.0 mM, likely as a result of increased branchial permeability. While plasma [ammonia] clearly responded to copper exposure, plasma [urea] exhibited a much more sensitive and pronounced response to both acute and prolonged copper exposure, resulting in as much as a three-fold increase in circulating urea levels. This response is most likely the result of the unique ability of this teleost to convert ammonia to urea.

Ethnomedical value of Cissampelos pareira extract in experimentally induced diarrhoea

The antidiarrhoeal activity of the ethanolic extract of Cissampelos pareira (Menispermaceae) roots was assessed on experimental animals. The hydroethanolic extract (25-100 mg dry extract kg(-1) body mass, p.o.) exhibited a dose dependent decrease in the total number of faecal droppings (control 65, reduced to 26-46) and 29.2-60.0% inhibition in castor oil-induced diarrhoea. Further, C. pareira produced a significant (p < 0.01) and dose dependent reduction in intestinal fluids accumulation (26.0-59.0%). The extract showed a greater inhibitory effect on the concentration of Na+ (20.0 and 34.5%) than on the concentration of K+ (6.7 and 9.4%). The extract also reduced dose dependently the gastrointestinal transit from 46.4 and 38.7%, equivalent to 53.6 and 61.3%. However, C. pareira significantly reduced the lipid peroxidation and inhibited the decrease in antioxidant enzyme levels (superoxide dismutase and catalase) on prior administration to castor oil-induced fluid accumulation. The extract of C. pareira had no effect on normal defecation at 25 mg kg(-1) in mice. However, 50 and 100 mg kg(-1) inhibited defecation by 100% in the initial 2 h and the activity was reduced to 40.0 and 73.0%, respectively, in the third hour.

Prevention of toxin-induced intestinal ion and fluid secretion by a small-molecule CFTR inhibitor

BACKGROUND & AIMS

The cystic fibrosis transmembrane conductance regulator (CFTR) provides an important apical route for Cl(-) secretion across intestinal epithelia. A thiazolidinone-type CFTR blocker (CFTR(inh)-172) reduced cholera toxin-induced fluid accumulation in mouse intestinal loops. Here, we characterize the efficacy and pharmacodynamics of CFTR(inh)-172 in blocking cAMP and cGMP induced Cl(-)/fluid secretion in rodent and human intestine.

METHODS & RESULTS

CFTR(inh)-172 inhibited cAMP and cGMP agonist induced short-circuit current by >95% in T84 colonic epithelial cells (K(I) approximately 3 micromol/L) and in mouse and human intestinal sheets (K(I) approximately 9 micromol/L). A single intraperitoneal injection of CFTR(inh)-172 (200 microg) blocked intestinal fluid secretion in a rat closed-loop model by >90% for cholera toxin and >70% for STa Escherichia coli toxin. In mice, CFTR(inh)-172 (20 microg) inhibited cholera toxin-induced intestinal fluid secretion by 90% (persistence t(1/2) approximately 10 hours, K(I) approximately 5 microg) and STa toxin by 75% (K(I) approximately 10 microg). Tissue distribution and pharmacokinetic studies indicated intestinal CFTR(inh)-172 accumulation facilitated by enterohepatic circulation. An oral CFTR(inh)-172 preparation reduced fluid secretion by >90% in a mouse open-loop cholera model.

CONCLUSIONS

A small molecule CFTR blocker markedly reduced intestinal ion and fluid secretion caused by cAMP/cGMP-dependent bacterial enterotoxins. CFTR inhibition may thus reduce fluid secretion in infectious secretory diarrheas.

The role of chloride in deoxycorticosterone hypertension: selective sodium loading by diet or drinking fluid

To evaluate the role of chloride in the pathogenesis of salt-dependent deoxycorticosterone (DOC) hypertension, we studied young Wistar rats chronically loaded with sodium bicarbonate (NaHCO(3)) or sodium chloride (NaCl) which were administered either in the diet or in the drinking fluid. Selective sodium loading (without chloride) increased blood pressure (BP) in DOC-treated animals only if NaHCO(3) was provided in the diet. In contrast, no significant blood pressure changes were induced by DOC treatment in rats drinking NaHCO(3) solution. Hypernatremia and high plasma osmolality occurred only in rats drinking NaCl or NaHCO(3) solutions. Compared to great volume expansion in NaCl-loaded DOC-treated rats, the degree of extracellular fluid volume expansion (namely of its interstitial fraction) was substantially lower in both NaHCO(3)-loaded groups in which significant hypokalemia was observed. NaHCO(3)-drinking rats without significant blood pressure response to DOC treatment represented the only experimental group in which blood volume was not expanded. In conclusion, our data confirm previous observations that NaHCO(3) loading is less potent in eliciting DOC hypertension than NaCl loading, but blood pressure rise in rats fed NaHCO(3) diet clearly demonstrated that selective sodium loading could potentiate the development of DOC hypertension if NaHCO(3) is offered within the appropriate dietary regimen. The reasons for the failure of NaHCO(3)-drinking rats to elevate blood pressure in response to chronic mineralocorticoid treatment are not obvious. However, the absence of a significant plasma volume expansion together with hypernatremia and increased plasma osmolality suggest a considerable degree of dehydration in these animals which fail to increase their fluid consumption compared to water drinking rats.

Lethal effects of elevated pH and ammonia on juveniles of neotropical fish Colosoma macropomum (Pisces, Caracidae)

Ammonia is the main nitrogenous waste material excreted by gills, then is oxided first to nitrite and then to nitrate. The proportion of ionized-un-ionized ammonia depends on pH and temperature, when this variables increase in a solution containing ammonia the equation goes to left, so the proportion of NH3 increases and the solution becomes more toxic. The purpose of this study was to investigate the acute lethal effects of elevated pH and ammonia on tambaqui juveniles. With a constant ammonia concentration of 5.0 mg/l NH3, there was no mortality a pH of 6.0 (control) and 7.0; but was of 10-20% a pH of 8.0 and 100% at 9.0. The lethal effects of elevated pH and un-ionized ammonia should be recognized as a potential factor contributing to the variable success of tambaqui production ponds, but this species is highly resistant in comparison with other freshwater fish.

The biological behaviour and bioavailability of aluminium in man, with special reference to studies employing aluminium-26 as a tracer: review and study update

Until 1990 biokinetic studies of aluminium metabolism and biokinetics in man and other animals had been substantially inhibited by analytical and practical difficulties. Of these, the most important are the difficulties in differentiating between administered aluminium and endogenous aluminium-especially in body fluids and excreta and the problems associated with the contamination of samples with environmental aluminium. As a consequence of these it was not possible to detect small, residual body burdens of the metal following experimental administrations. Consequently, many believed aluminium to be quantitatively excreted within a short time of uptake in all, but renal-failure patients. Nevertheless, residual aluminium deposits in a number of different organs and tissues had been detected in normal subjects using a variety of techniques, including histochemical staining methods. In order to understand the origins and kinetics of such residual aluminium deposits new approaches were required. One approach taken was to employ the radioisotope (67)Ga as a surrogate, but this approach has been shown to be flawed-a consequence of the different biological behaviours of aluminium and gallium. A second arose from the availability, in about 1990, of both (26)Al-a rare and expensive isotope of aluminium-and accelerator mass spectrometry for the ultra-trace detection of this isotope. Using these techniques the basic features of aluminium biokinetics and bioavailability have been unravelled. It is now clear that some aluminium is retained in the body-most probably within the skeleton, and that some deposits in the brain. However, most aluminium that enters the blood is excreted in urine within a few days or weeks and the gastrointestinal tract provides an effective barrier to aluminium uptake. Aspects of the biokinetics and bioavailability of aluminium are described below.

Cholera toxin protects against action by Clostridium difficile toxin A. The role of antisecretory factor in intestinal secretion and inflammation in rat

The protein antisecretory factor (AF) inhibits intestinal fluid secretion induced by the cholera toxin (CT) and Clostridium difficile toxin A (CDA). The present work investigated whether CT-induced AF protects against the enterotoxin action by CDA. Rats were pretreated perorally with CT or buffer as control, whereafter CDA-induced fluid secretion and cytotoxicity was tested in vivo in ligated intestinal loops; the mucosal level of AF was estimated using the Western blot technique. Rats given repeated peroral doses of CT became tolerant to CDA, the inhibition of fluid secretion and of cytotoxicity being 79% in eight out of nine animals. The repeated CT-treatment also induced long-lasting rise of AF in the mucosal epithelium. Recombinant AF given either perorally or intravenously inhibited both fluid secretion and cytotoxicity by CDA; similar results were obtained with a truncated 16-mer AF peptide.

IN CONCLUSION

peroral CT-treatment induced tolerance to CDA in rat small intestine. The tolerance was probably mediated by AF induced via action of cholera toxin on the enteric nervous and immune system.

Considerations for management of fluid dynamic issues associated with thiazolidinediones

Thiazolidinediones (TZDs) can cause weight gain and fluid retention in some patients. In most cases, fluid retention is expressed as mild hemodilution. The incidence of clinically evident edema is relatively uncommon. In large clinical trials with rosiglitazone and pioglitazone, the frequency of edema in TZD-treated patients was about 3 to 4 times higher than in placebo-treated patients. The precise mechanisms responsible for weight gain, fluid retention, and edema associated with TZD therapy are unclear but appear to be both dose- and host-related. Weight gain is most likely multifactorial, reflecting increased body fat and fluid retention. Available data are conflicting and do not completely support the concept that increased body weight and decreased hemoglobin/hematocrit are linked with evidence of fluid retention and hemodilution. As uncommon as edema is, new-onset heart failure is even less common in patients treated with a TZD. In controlled clinical trials, the frequency of congestive heart failure (CHF) was identical in rosiglitazone- and placebo-treated patients. The incidence of CHF is higher in patients receiving combination therapy with insulin and a TZD. Patients in the insulin-treated population who develop CHF tend to be older, have a longer history of type 2 diabetes mellitus, and have risk factors for heart failure in addition to diabetes. TZDs do not necessarily require discontinuation in patients who develop fluid retention or weight gain. Mild fluid retention can be treated by decreasing the TZD dose and/or adding a diuretic. Patients who are taking a TZD should be monitored for signs and symptoms of CHF, including excessive weight gain, edema, and dyspnea. Patients with New York Heart Association (NYHA) class I or II CHF can be treated with TZDs. Therapy should be initiated at low doses and slowly titrated to the lowest effective dose. If CHF worsens or becomes refractory to treatment, it may be necessary to discontinue the TZD. Diagnoses of NYHA class III and IV CHF were not studied in clinical trials of TZDs, and thus TZDs are not recommended for patients with CHF of this severity.

Effect of acetate and bicarbonate dialysate on whole body bioimpedance (BIS) and segmental (thoracic) bioimpedance in hemodialysed (HD) patients

There are sparse data about the influence of dialysis itself on bioimpedance measurement. The aim of this study was to evaluate the influence of dialysis without ultrafiltration on bioimpedance of thorax and bioimpedance of the whole body in hemodialysed patients. Isovolemic HD was performed during the first hour of dialysis session, using bicarbonate and then acetate dialysate. Thoracic impedance, whole body bioimpedance, blood pressure and blood density were measured. After bicarbonate dialysis significant TI lowering was observed with simultaneous R increase. There was a significant blood density lowering. Acetate hemodialysis caused no significant changes in TI but significant increase in R values. Blood density did not change after acetate HD. The influence of other factors, not only hydration status changes, must be considered in interpretation of bioimpedance measurement analysis.

Role of excess volume in the pathophysiology of hypertension in chronic kidney disease

BACKGROUND

The pathophysiology of hypertension in patients with chronic kidney disease (CKD) is largely attributed to positive sodium balance. It is unclear how loop diuretics affect fluid volume compartments, especially with respect to their antihypertensive effect.

METHODS

Subjects with CKD were administered a single therapeutically equivalent dose of an oral loop diuretic (furosemide or torsemide in randomized crossover design). We measured acute volume changes over 12 hours using biophysical and hormonal biomarkers and then 24-hour ambulatory blood pressure after daily diuretic therapy for 3 weeks.

RESULTS

Single-dose administration of loop diuretic decreased extracellular water (ECW) by 1.7 L [95% confidence interval (95% CI) 1.2, 2.2, P < 0.001], total body water (TBW) by 1.2 L (95% CI 0.5, 1.9, P < 0.001), and increased natural log (ln) plasma renin activity (PRA) from -1.2 +/- 1.3 ng/mL/hour to -0.5 +/- 1.5 ng/mL/hour (P < 0.001). Daily loop diuretic administration resulted in reduced ECW from 24.2 +/- 6.4 L to 22.3 +/- 5.2 L (P = 0.02) and TBW from 54.3 +/- 12.7 L to 51.6 +/- 11.9 L (P < 0.001) in 1 week. After 3 weeks of diuretic therapy, whereas ECW reduction persisted at 22.8 +/- 5.1 L (P = 0.05), TBW trended toward baseline level at 52.7 +/- 11.8 L. A concomitant increase in ln PRA from -1.0 +/- 1.3 ng/mL/hour to 0.4 +/- 1.9 ng/mL/hour (P < 0.001) and ln plasma aldosterone (PA) from 2.0 +/- 0.8 ng/dL to 2.3 +/- 0.8 ng/dL (P < 0.005) and fall in ln brain natriuretic peptide (BNP) from 4.3 +/- 0.9 pg/mL to 3.7 +/- 1.0 pg/mL (P < 0.01) were seen at 1 week. Despite a trend toward restoration of TBW, changes in hormonal biomarkers were maintained at 3 weeks. Over these 3 weeks, furosemide reduced 24-hour ambulatory blood pressure from 147 +/- 17/78 +/- 11 mm Hg to 138 +/- 21/74 +/- 12 mm Hg (P = 0.021) and torsemide reduced it from 143 +/- 18/75 +/- 10 mm Hg to 133 +/- 19/71 +/- 10 mm Hg (P = 0.007).

CONCLUSION

Patients with CKD have elevated extracellular fluid volume that can be corrected acutely with loop diuretics. Persistent diuretic use results in dynamic changes in ECW and other body fluid compartments that translate into chronic blood pressure reduction.

A randomized, controlled study of fluid management in infants and toddlers during surgery: hydroxyethyl starch 6% (HES 70/0.5) vs lactated Ringer's solution

BACKGROUND

Volume replacement with hydroxyethyl starch (HES), a synthetic colloid, is widely accepted in adults, but only few data exist regarding its use in children. The aim of this study was to assess the effect of a low molecular weight HES solution (HES 70/0.5) compared with lactated Ringer's solution (LR) on haemoglobin levels as an indirect measure of plasma expansion in infants and toddlers, and its perioperative safety.

METHODS

Sixty-four patients, aged 1-38 months, were allocated randomly to receive 20 ml x kg-1 body weight of either HES 70/0.5 or LR during the first hour of urological surgery lasting >2 h. Thereafter, only LR was infused to maintain haemodynamic stability. Intraoperative blood loss and administered fluid volumes were analysed. Haemoglobin levels were determined perioperatively and intraoperatively at completion of volume loading. Changes in body weight and the incidence of postoperative oedema were assessed 24 and 48 h after surgery. For the safety analysis, patients were monitored for 72 h.

RESULTS

Intraoperative haemoglobin levels decreased significantly more with HES 70/0.5 (30 +/- 10 g.l-1) compared with LR (21 +/- 12 g.l-1) (P < 0.01). The overall administered fluid volumes during surgery did not differ between groups. The postoperative changes in body weight and incidence of postoperative oedema did not differ between groups. No anaphylactoid reactions, pruritus or adverse effects were observed during the study period.

CONCLUSIONS

A larger decrease in haemoglobin levels in infants and toddlers after HES 70/0.5 (20 ml.kg-1) compared with LR indicates a more effective plasma expansion. HES might be considered as a volume expander in the paediatric population.