[Use of maintenance fluid therapy in surgery]

OBJECTIVE

To analyze the use of various maintenance fluid therapy regimens, as well as their adequacy to hospital recommendations, in adult in-patients admitted to a general surgery ward during 1 year.

MATERIAL AND METHODS

Data on solution type and volume, fluid therapy regimen, and duration in days were retrospectively collected for each administered solution from computerized medical orders within the Unit-Dose Drug Distribution Area. A database was developed including the composition of available solutions within our hospital, so that electrolytes, glucose and volumes administered may be calculated.

RESULTS

Out of 354 patients undergoing fluid therapy 125 were selected to receive maintenance regimens. Fluid therapy was administered for more than 5 days in 31% of patients. The most commonly supplied fluids were 5% glucose (43%) and 0.9% saline + 1500 mL of 5% glucose + 60 mEq potassium chloride (CIK). Amongst patients receiving the recommended volume/day (84%) 50% received sodium and potassium more than twice as much the recommended amount, and 70% received glucose amounts not covering minimal daily requirements. Potassium was administered according to recommendations in 85% of patients.

CONCLUSIONS

There is an excessive use of 0.9% saline and 5% glucose to the detriment of 1/3 glucosaline and 10% glucose, which translates as an excessive daily sodium and defective daily glucose provision. In our hospital we have recommended maintenance fluid therapy regimens, as well as fluids more appropriate for postoperative electrolyte replacement; however, their use is still deficient.

Diagnosis and management of electrolyte emergencies

Electrolyte and fluid imbalances are disorders frequently observed in critical care patients. In many instances patients are asymptomatic, but they may also present with neurological alterations, severe muscle weakness, nausea and vomiting or cardiovascular emergencies. Therefore, a pathophysiological understanding of these disorders is necessary for initiating an appropriate therapy. After a precise history-including drug prescriptions-has been obtained from the patient or his/her relatives, determination of the hydration status of the patient and measurement of acid-base status, plasma and urine osmolality and electrolytes are the first steps in the assessment of the disease. Once a diagnosis has been established, great attention has to be paid to the rate at which the disorder is corrected because this-if inappropriate-may cause more severe damage to the patient than the disease itself. This chapter addresses the initial diagnostic and therapeutic steps of the most common electrolyte emergencies.

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.

High-dose angiotensin-converting enzyme inhibition restores body fluid homeostasis in heart-transplant recipients

OBJECTIVES

We tested the hypothesis that salt and fluid retention in heart-transplant recipients (HTRs) is caused by a failure to reflexively suppress the renin-angiotensin-aldosterone system (RAAS).

BACKGROUND

It is known that extracellular fluid volume is expanded (12% to 15%) in HTRs who develop hypertension.

METHODS

Responses to volume expansion were measured in eight HTRs (ages 57 +/- 6 years) and six liver-transplant recipients (LTRs) (ages 52 +/- 2 years) both before and after treatment with captopril (225 mg/day). After three days of a standardized diet, 0.154 mol/l saline was infused at 8 ml/kg/h for 4 h. Blood pressure, hormones, and renal function were monitored for 48 h. After four months, the same subjects received captopril (225 mg/day), and the protocol was repeated.

RESULTS

Before captopril, saline infusion suppressed the RAAS in LTRs but not in HTRs, resulting in elimination of 86 +/- 12% versus 50 +/- 11% of the sodium load by 48-h postinfusion. Blood pressure increased only in the HTRs (+16 +/- 5/9 +/- 3 mm Hg) and remained elevated for 48 h (p < or = 0.05). After captopril, sodium elimination was comparable in the liver (87 +/- 13%) and heart groups (86 +/- 12%) and blood pressure did not change in either group. CONCLUSIONS; Heart transplant recipients have blunted diuretic and natriuretic responses to volume expansion that is mediated by their inability to suppress the RAAS. Pharmacologic suppression of the RAAS normalized defects in blood pressure and fluid homeostasis. These findings indicate that hypertension in HTRs is caused, in part, by a failure to reflexively suppress the RAAS when these patients become hypervolemic.

Vasopressin V2 receptor antagonists

Hyponatremia due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) and disorders of water retention such as congestive heart failure and cirrhosis is a common problem encountered in the care of the medical patient. Thus far, available treatment modalities for disorders of excess arginine vasopressin (AVP) secretion or action have been suboptimal. The development of nonpeptide AVP V2 receptor antagonists represents a promising treatment option to directly antagonize the effects of elevated plasma AVP concentrations by increasing the water permeability of renal collecting tubules, thereby promoting excretion of retained water and normalizing hypoosmolar hyponatremia. In this review, SIADH and other water retaining disorders are briefly discussed, after which the published preclinical and clinical studies in the development of several nonpeptide AVP V2 receptor antagonists are summarized. The likely therapeutic indications and potential complications of these compounds, as well as their vascular effects, are also described.

[Electrolyte abnormalities and metabolic acidosis in two Duchenne muscular dystrophy patients with advanced congestive heart failure]

We experienced two Duchenne muscular dystrophy patients with advanced congestive heart failure, who showed abrupt severe hyponatremia, hyperkalemia and metabolic acidosis. Two patients received respiratory management, parenteral nutrition, and drugs including angiotensin converting enzyme inhibitors (ACEI). The patient 1 who was 19 years old showed abdominal pain, hematuria, diarrhea and disorientation. Laboratory findings were as follows; Na 120 mEq/L, K 7.3 mEq/L, BUN > 140 mg/dl (scale over), ACTH 20.2 pg/ml, cortisol 25 micrograms/dl, renin 40.7 ng/ml/hr and aldosterone 203 ng/dl. Arterial blood gas analysis (ABG) showed metabolic acidosis (pH 7.232). Combination therapy with hydrocortisone, glucose-insulin therapy (GIT) and NaHCO3 successfully rescued this patient. The patient 2 (28 years of age) was admitted to our hospital because of congestive heart failure. Laboratory findings were as follows; Na 129 mEq/L, K 5.5 mEq/L, BUN 60 mg/dl, cortisol 21 micrograms/dl, renin 36 ng/ml/hr and aldosterone 47 ng/dl. He complained abdominal discomforts from the next day of admission. Ten days after the admission Na, K and BUN were 111 mEq/L, 6.2 mEq/L and 154 mg/dl, respectively. ABG showed compensated metabolic acidosis. He fell into shock during GIT therapy. Laboratory findings at that time were as follows; Na 108 mEq/L, K 3.2 mEq/L, ACTH 77.6 pg/ml, cortisol 24 micrograms/dl, renin 58 ng/ml/hr and aldosterone 24 ng/dl. Although hydrocortisone was introduced, he could not recover and died. There are some reports about life-threatening electrolyte abnormalities and metabolic acidosis in the patients receiving ACEI. These phenomena were more frequent in patients with renal dysfunction and/or congestive heart failure. Hyponatremia, hypovolemia, combination therapy with nonsteroidal anti-inflammatory drugs (NSAID) and/or potassium sparing diuretics were reported as risk factors. We could not prove the correlation between the acute changes in our cases and ACEI. However ACEI is suspicious, because many of these risk factors were observed in our cases. Aldosterone was extremely elevated in the patient 1 when potassium was severely elevated. On the other hand, the patient 2 showed lower aldosterone level after correction of potassium than that on admission. Potassium is regarded as a major secretion factor of aldosterone for patients receiving ACEI. The fact the patient 2 fell into shock during GIT, tells us that we should use steroid simultaneously when we try to correct potassium quickly in severe cases, because acute reduction of potassium may decrease aldosterone. Today, ACEI is a common drug for CHF, so we should pay attentions that ACEI could cause such acute changes. To prevent such acute changes, excessive restriction of water and sodium intake should be avoided. If possible, NSAID and potassium sparing diuretics also should be avoided. Steroid therapy must be introduced rapidly when needed.

Aminophylline in the treatment of fluid overload

OBJECTIVE

Aminophylline has not been studied as an adjunct diuretic in critically ill children. Our purpose was to evaluate its use in the treatment of fluid overload in these patients.

DESIGN

Open, controlled clinical trial.

SETTING

Pediatric intensive care unit.

PATIENTS

Study subjects ranged from 2-46 months of age, were fluid overloaded, and were receiving a continuous infusion of furosemide (> or =6 mg/kg/day). Patients with hemodynamic instability or liver dysfunction were excluded.

INTERVENTIONS

A single dose of aminophylline (6 mg/kg) was given after establishing baseline values. There were no additional diuretics or changes in vasoactive agents during the study.

MEASUREMENTS AND MAIN RESULTS

Urine output, creatinine clearance, and sodium and potassium excretion were measured before and after administration of the aminophylline bolus. Heart rate and mean arterial pressure (mm Hg) were recorded hourly. Urine output increased by >80% (p < .01) during the first 2 hrs after administration of the aminophylline bolus and then returned to baseline by 4 to 6 hrs. The change in urine output is consistent with the pharmacokinetics of aminophylline. Heart rate and mean arterial pressure exhibited a change of <10% from baseline.

CONCLUSIONS

These results suggest that aminophylline is an effective adjunct to furosemide in increasing diuresis in critically ill children with fluid overload. The increased diuresis can be accomplished without increased risk if drug levels are adequately monitored.

A patient-focused approach to managing diuretic therapy

The use of diuretic therapy has been shown to be efficacious in a variety of patient populations. However, its use is not without untoward side effects. Knowledge about the indications for and possible complications resulting from diuretic therapy is imperative to any practitioner prescribing and administering these medications. Informing your patients about why they are on these medications and any side effects will help to prevent the incidence of complications.

A comprehensive analysis of the fluid and electrolytes system. An interactive exercise

The fluid and electrolyte system is difficult to study because one cannot examine an organ in order to understand the anatomical and functional connection. This exercise was developed to emphasize the connection between different fluid and electrolyte situations.

Magnesium supplementation alleviates premenstrual symptoms of fluid retention

We investigated the effect of a daily supplement of 200 mg of magnesium (as MgO) for two menstrual cycles on the severity of premenstrual symptoms in a randomized, double-blind, placebo-controlled, crossover study. A daily supplement of 200 mg of Mg (as MgO) or placebo was administered for two menstrual cycles to each volunteer, who kept a daily record of her symptoms, using a 4-point scale in a menstrual diary of 22 items. Symptoms were grouped into six categories: PMS-A (anxiety), PMS-C (craving), PMS-D (depression), PMS-H (hydration), PMS-O (other), and PMS-T (total overall symptoms). Urinary Mg output/24 hours was estimated from spot samples using the Mg/creatinine ratio. Analysis of variance for 38 women showed no effect of Mg supplementation compared with placebo in any category in the first month of supplementation. In the second month there was a greater reduction (p = 0.009) of symptoms of PMS-H (weight gain, swelling of extremities, breast tenderness, abdominal bloating) with Mg supplementation compared with placebo. Compliance to supplementation was confirmed by the greater mean estimated 24-hour urinary output of Mg (p = 0.013) during Mg supplementation (100.8 mg) compared with placebo (74.1 mg). A daily supplement of 200 mg of Mg (as MgO) reduced mild premenstrual symptoms of fluid retention in the second cycle of administration.

Primary and drug-induced disorders of water homeostasis in psychiatric patients: principles of diagnosis and management

Psychotropic drugs, as well as some psychiatric disorders, can produce neurotoxic and life-threatening abnormalities of water and electrolyte balance that require prompt and appropriate medical intervention. Compulsive fluid intake by psychotic patients (primary polydipsia) can produce delirium due to water intoxication with hyponatremia. Several psychotropic drugs cause water retention by decreasing renal clearance, as in the syndrome of inappropriate antidiuretic hormone secretion. Lithium and other agents interfere with renal resorption of water to cause nephrogenic diabetes insipidus. Clinical signs in these disorders range from lethargy and confusion to stupor, seizures, coma, and death. This overview provides a conceptual framework for differentiating among and safely managing these relatively common disorders.

Sheep model for study of maternal adrenal gland function during pregnancy

Our goal was to develop a model for the study of maternal adrenal gland regulation and the effects of maternal cortisol secretion on fetal homeostasis. At about 108 days of gestation, before the time of rapid fetal growth or fetal adrenocortical maturation, ewes, under halothane anesthesia with controlled ventilation and positioned in sternal recumbency, were adrenalectomized. Ewes were treated with aldosterone by intravenous infusion (3 micrograms/kg of body weight per day) to induce normal late-gestation aldosterone concentration. Ewes were also treated with cortisol; for 2 postoperative days, this infusion (1 to 2 micrograms/kg per min) induced plasma concentration similar to that associated with stress. Thereafter, the dosage of cortisol was reduced to induce plasma values similar to normal late-gestation cortisol concentration in ewes (1 mg/kg per day), or to values in nonpregnant ewes (0.6 mg/kg per day). Administration of cortisol and aldosterone was required to prevent electrolyte imbalance and signs of hypoadrenocorticism. With steroid replacement, plasma protein, electrolyte, and glucose concentrations in adrenalectomized ewes were not different from those in sham-operated pregnant ewes. Of 11 adrenalectomized ewes, one died as a result of failure of the infusion pump, and one died as a result of inappropriate treatment for hypoglycemia. Of the remaining ewes, two aborted fetuses, three ewes each delivered one live and one dead fetus, two delivered live singleton fetuses, and two delivered twins. Therefore, this model of relative hypoadrenocorticism in pregnancy is feasible and practical for studying the influence of maternal cortisol concentration on maternal and fetal homeostasis.

Falciparum malaria and the kidney: a model of inflammation

Renal and renal-related disorders commonly occur in infection with Plasmodium falciparum, which can cause fluid and electrolyte disorders, glomerulonephritis, and acute renal failure (ARF). It appears that ARF and other life-threatening complications in falciparum malaria are not directly caused by the parasite itself but are the result of interaction of mechanical, immunologic, and humoral components. P. falciparum-infected erythrocytes impair microcirculation and cause hemolysis. Glycosylphosphatidylinositol moieties covalently linked to the surface antigens of falciparum malarial parasites appear to act like endotoxin. Glycosylphosphatidylinositol, via CD14, which is a receptor on monocytes, stimulates monocytes to release tumor necrosis factor, which in turn enhances synthesis of various cytokine cascades and mediators. Besides contributing to ARF, these mediators also cause changes in blood volume status. The degree of vasodilatation caused by vasodilating mediators varies with the severity of infection. Increased vascular permeability by the mediators occurs in severe infection, which results in hypovolemia and contributes to ARF. Although the cornerstone of treatment of malaria still is antimalarial drugs, several new modalities of treatment targeting toxin, signal transduction, mediators, and cytokines have great potential.

Anion gap acidosis

Although an anion gap at less than 20 mEq/L rarely has a defined etiology, significant elevations in the anion gap almost always signify presence of an acidosis that can be easily identified. Anion gap acidoses can be divided into those caused by lactate accumulation, ketoacid production, toxin/drugs, and uremia. Lactic acidoses caused by decreased oxygen delivery or defective oxygen utilization are associated with high mortality. The treatment of lactic acidosis is controversial. The use of bicarbonate to increase pH is rarely successful and, by generating PCO2, may worsen outcome. Ketoacidosis is usually secondary to diabetes or alcohol. Treatment is aimed at turning off ketogenesis and repairing fluid and electrolyte abnormalities. Methanol, ethylene glycol, and salicylates are responsible for the majority of toxin-induced anion gap acidoses. Both methanol and ethylene glycol are associated with severe acidoses and elevated osmolar gaps. Treatment of both is alcohol infusion to decrease formation of toxic metabolites and dialyses to remove toxins. Salicylate toxicity usually is associated with a mild metabolic acidosis and a respiratory alkalosis. Uremia is associated with a mild acidosis secondary to decreased ammonia secretion and an anion gap caused by the retention of unmeasured anions. A decrease in anion gap is caused by numerous mechanisms and thus has little clinical utility.

Hypomagnesemia: renal magnesium handling

Magnesium is an important constituent of the intracellular space that affects a number of intracellular and whole body functions. Magnesium balance depends on intake and renal excretion, which is regulated mainly in the thick ascending limb of the loop of Henle. The complex hormonal modulation that responds to changes in plasma concentration of other ions such as calcium and potassium is lacking for magnesium. As a result, negative magnesium balance results in a prompt decrease in plasma magnesium concentration, and hypermagnesemia accompanies renal failure with magnesium accumulation. Hypomagnesemia may result from gastrointestinal losses or renal losses, the latter due to primary renal magnesium wasting or in association with sodium loss. Hypomagnesemia may arise together with and contribute to the persistence of hypokalemia and hypocalcemia. The major direct toxicity of hypomagnesemia is cardiovascular. When urgent correction of hypomagnesemia is required, as with myocardial ischemia, post cardiopulmonary bypass, and torsades de pointes, intravenous or intramuscular magnesium sulfate should be used. Oral magnesium preparations are available for chronic use.

Protocol-guided diuretic management: comparison of furosemide by continuous infusion and intermittent bolus

OBJECTIVE

To evaluate the safety and relative effectiveness of two diuretic protocols in the intensive care unit (ICU).

DESIGN

Prospective, randomized comparative study.

PATIENTS

Thirty-three cardiac and medical ICU patients with pulmonary edema or fluid overload for which aggressive diuresis was intended.

INTERVENTIONS

Enrolled patients were randomized to fluid management strategies combining fluid restriction and individually adjusted diuretic therapy by either continuous or bolus infusions of furosemide, titrated to achieve negative hourly fluid balance.

MEASUREMENTS AND MAIN RESULTS

Cumulative intake minus output (primary endpoint); change in serum creatinine, and length of ICU and hospital stay (secondary endpoints). Diuresis by either protocol was feasible, safe, and effective. The main outcome measures were not significantly different for either group managed with a standardized protocol.

CONCLUSIONS

Protocol-guided diuretic management, with individualized titration of dosage to defined physiologic endpoints can be readily and safely implemented in the ICU. Both continuous and bolus diuretic regimens appear equally effective in achieving negative fluid balance. Larger studies with a randomized control arm are needed before these protocols can be recommended as routine practice.

Salt-losing nephropathy associated with inappropriate secretion of atrial natriuretic peptide--a new clinical syndrome

A state of normokalemic renal sodium wasting associated with an apparently inappropriate secretion of atrial natriuretic peptide (ANP) has not been previously recognized. We here report an 11-year-old boy who presented with a chronic "salt-losing" nephropathy manifested by normonatremic or mildly hyponatremic extracellular fluid volume depletion, hypodipsia, absence of salt appetite, normokalemic metabolic alkalosis, hyper-reninemic hyperaldosteronism, hypertrophy of the juxtaglomerular apparatus, and highly conserved capacities for concentrating diluting the urine. Plasma ANP values were paradoxically elevated (between 10 and 47 fmol/ml), despite the coexistence of intravascular volume depletion and increased plasma levels of renin and aldosterone. Although the patient had some clinical similarities to Bartter's syndrome, fractional sodium chloride (NaCl) reabsorption during hypotonic saline diuresis was normal and no clinical amelioration was observed while on indomethacin therapy. Neither a tumor nor cardiac or cerebral abnormalities, which could be responsible for the increased ANP secretion, were detected. These clinical, biochemical, and histological features have not been previously described together and may represent a new clinical syndrome. The pathophysiology of this entity remains unknown, but an attractive, although unproven, hypothesis is that the renal defect in NaCl reabsorption in this patient could be related to an inappropriate and unregulated secretion of ANP.

Postural hypotension and abnormalities of salt and water metabolism in myelopathy patients

To describe the clinical manifestations of postural hypotension (PH) in myelopathy patients a standardized interview and chart review were carried out. Of 232 myelopathy patients with more than 2 years of paralysis seen during a 2 year period, 30 had been treated for PH. All PH patients were paralysed at levels higher than thoracic 7. The highest risk patients were tetraplegic, motor complete, 24 of 73 (33%). The common symptoms of PH were those of reduced consciousness (100%), strength (75%), vision (56%) and breath (53%). Precipitating factors were hot weather (77%) bowel care (33%) and meals (30%). Symptoms worsened with the duration of paralysis in 12 patients. Chronic hyponatremia was found in 54% of the PH patients and 16% of those without, P < 0.001. Of five PH-hyponatremic patients with urine sodium and osmolality determinations, five continued to retain water (> 150 mOsm/kg) while four failed to conserve salt (> 19 mmol Na/L). PH is common among myelopathy patients with higher levels of paralysis, symptoms are variable, and abnormal salt and water metabolism often coexist.

[Significance of diuretics in the treatment of hypertension]

Due to new therapeutic substances the use of diuretics in the treatment of hypertension is decreasing slowly over the last few years. Nevertheless diuretics still represent one important cornerstone in the therapy of most forms of high blood pressure. Metabolic side effects of diuretics are often used as an argument against their clinical use. Indeed the diuretic therapy may lead as a function of the dosage and the duration of the therapy to an increase of total cholesterol and an impairment of the glucose tolerance. Spironolactone and other potassium sparing diuretics are "lipid-neutral". These metabolic side effects of the diuretics can be counterbalanced by the implementation of non-pharmacological means of blood pressure therapy. Body weight control seems to be of central importance. Therapy resistant forms of hypertension may be caused by many different pathogenetic mechanisms. Besides other reasons (such as secondary hypertension, non compliance ect) volume overload may represent one of the most important reasons of resistant forms of hypertension. Diuretics, especially also the aldosterone antagonists, play a central role in the control of most situations associated with volume overload in the setting of essential hypertension.