A critical evaluation of ultrasound measurement of inferior vena cava diameter in assessing dry weight in normotensive and hypertensive hemodialysis patients

The utility of measurement of the inferior vena cava diameter (IVCD) with ultrasound for the assessment of fluid status and posthemodialysis dry weight was studied in 35 hemodialysis (HD) patients, 17 with and 18 without hypertension. In 17 patients (group A), IVCD was measured before and 35 to 40 minutes after HD, pre-HD blood volume (BV) was measured with radiolabeled albumin and post-HD BV was calculated from the change in hematocrit. In 18 patients (group B), IVCD was measured repeatedly during HD and 2 hours after HD. Changes in BV were recorded by monitoring of the hematocrit "on line." Body weight, blood pressure (BP), BV, and IVCD decreased in the entire population. In group A, BV was significantly larger in the hypertensive patients than in the normotensive patients, and it was correlated with the mean BP before and after HD. In the whole population, IVCD was larger in the hypertensive than in the normotensive patients before and after HD. These results confirm that extracellular fluid overload plays an important role in the pathogenesis of dialysis-associated hypertension. In group B, BV and IVCD decreased in parallel during HD and increased during 2 hours after HD due to refilling of the intravascular space, indicating that changes in IVCD reflect changes in BV. In 8 patients studied twice, IVCD increased much more after a 3-hour HD session than after a 6-hour session. At the end of HD, several patients had IVCD below the reference range but IVCD increased during the following 1 to 2 hours, in some patients to values above the reference range. IVCD measured at the end or shortly after HD may therefore be misleading in assessing dry weight.

Pathophysiology of hyponatremia after transsphenoidal pituitary surgery

Hyponatremia after pituitary surgery is presumed to be due to antidiuresis; however, detailed prospective investigations of water balance that would define its pathophysiology and true incidence have not been established. In this prospective study, the authors documented water balance in patients for 10 days after surgery, monitored any sodium dysregulation, further characterized the pathophysiology of hyponatremia, and correlated the degree of intraoperative stalk and posterior pituitary damage with water balance dysfunction. Ninety-two patients who underwent transsphenoidal pituitary surgery were studied. To evaluate posterior pituitary damage, a questionnaire was completed immediately after surgery in 61 patients. To examine the osmotic regulation of vasopressin secretion in normonatremic patients, water loads were administered 7 days after surgery. Patients were categorized on the basis of postoperative plasma sodium patterns. After pituitary surgery, 25% of the patients developed spontaneous isolated hyponatremia (Day 7 +/- 0.4). Twenty percent of the patients developed diabetes insipidus and 46% remained normonatremic. Plasma arginine vasopressin (AVP) was not suppressed in hyponatremic patients during hypoosmolality or in two-thirds of the normonatremic patients after water-load testing. Only one-third of the normonatremic patients excreted the water load and suppressed AVP normally. Hyponatremic patients were more natriuretic, had lower dietary sodium intake, and had similar fluid intake and cortisol and atrial natriuretic peptide (ANP) levels compared with normonatremic patients. Normnonatremia, hyponatremia, and diabetes insipidus were associated with increasing degrees of surgical manipulation of the posterior lobe and pituitary stalk during surgery. The pathophysiology of hyponatremia after transsphenoidal surgery is complex. It is initiated by pituitary damage that produces AVP secretion and dysfunctional osmoregulation in most surgically treated patients. Additional events that act together to promote the clinical expression of hyponatremia include nonatrial natriuretic peptide-related excess natriuresis, inappropriately normal fluid intake and thirst, as well as low dietary sodium intake. Patients should be monitored closely for plasma sodium, plentiful dietary sodium replacement, mild fluid restriction, and attention to symptoms of hyponatremia during the first 2 weeks after transsphenoidal surgery.

Twenty-year experience with jejunal conduits

OBJECTIVES

To assess the results of jejunal conduit urinary diversion, with particular attention to electrolyte imbalance and long-term renal function.

METHODS

From 1976 to 1994, 50 patients underwent urinary diversion using a short jejunal loop (10 to 12 cm) placed transperitoneally. Of these patients, 18 received pelvic irradiation before diversion. Renal function and configuration of the upper urinary tract were assessed by creatinine clearance and excretory urography.

RESULTS

Median follow-up was 26 months (3 to 204). Of 50 patients, 22 had a follow-up more than 5 years later (median 86 months). Eight patients (16%) underwent 10 revision procedures postoperatively. Late complications related to urinary diversion included renal calculi (12%), parastomal hernia (6%), pyelonephritis (4%), ureterojejunal obstruction (4%), and stomal prolapse (2%). Electrolyte imbalance occurred in 2 patients (4%) and was easily corrected by 4 g sodium bicarbonate. No significant decrease in creatinine clearance (P = 0.6) was found in 22 patients with a follow-up of more than 5 years; however, of these patients, 2 had a decrease in creatinine clearance of greater than 20%, due to ureterojejunal obstruction. Of 42 ureterorenal units, hydronephrosis occurred and increased in 1 and 2 cases, respectively, and renal scarring occurred and progressed in 2 and 2 cases, respectively.

CONCLUSIONS

Urinary diversion using a short length of jejunum placed transperitoneally is a reliable procedure and gives good long-term renal function. Electrolyte imbalances are rare. Moreover, jejunal conduit can be used in almost all situations, especially after pelvic irradiation.

Fluid balance during hysteroscopic surgery

Absorption of irrigating solution may involve serious complications during hysteroscopic surgery. This absorption occurs mainly into the vessels opened during the procedure. Careful perioperative monitoring of the deficit of collected irrigating medium during transcervical surgery is mandatory. Significant absorption seems to be connected with the development of discrete cerebral oedema and nausea, secondary to dilutional hyponatraemia and elevation of several amino acids.

Abnormalities of aldosterone synthesis and action in children

Genetic defects in aldosterone biosynthesis and action affect blood pressure and electrolyte homeostasis. Aldosterone synthase deficiency, salt-wasting forms of congenital adrenal hyperplasia, and adrenal hypoplasia congenita all cause aldosterone deficiency, signs of which include hyponatremia, hyperkalemia, hypovolemia, elevated plasma renin activity, and sometimes shock and death. Conversely, the inappropriate regulation of aldosterone synthesis seen in glucocorticoid-suppressible hyperaldosteronism may cause hypokalemia, suppressed plasma renin activity, and hypertension. Similar problems occur when the normal ligand specificity of the aldosterone receptor is lost, as in the syndrome of apparent mineralocorticoid excess due to 11 beta-hydroxysteroid dehydrogenase deficiency. The effects of aldosterone are mediated largely through activation of the epithelial sodium channel, and inactivating or activating mutations of this channel leads to signs of mineralocorticoid deficiency or excess, termed pseudohypoaldosteronism and Liddle's syndrome, respectively.

[Surgery in patients with renal failure in emergency and elective interventions]

The classification of renal insufficiency into stages of full compensation, compensated and decompensated retention and terminal renal failure is of importance if patients with impaired renal function are to undergo elective and emergency surgery. Furthermore, it should be established whether the renal disease is stable or progressive. Preoperatively, particular attention should be paid to problems of fluid and electrolyte homoeostasis as well as to acid-base balance. Many drugs should be avoided altogether in patients with kidney disease.

[Severe and unexpected occurrence of water-electrolyte disorders in the postoperative period]

Unexpected severe electrolyte imbalance in the postoperative period. Report two cases. Two cases of inappropriate secretion of antidiuretic hormone are reported. In each patient, the physiopathology is reviewed. Differential diagnosis and treatment of hyponatremia is discussed.

Paraneoplastic syndromes of the kidney

Malignant disease is associated with a wide variety of derangements in renal function and electrolyte homeostasis. In many cases this leads to a clinically significant worsening of health status and rarely may lead to the patient's death. In this review we discuss several of the important abnormalities of renal structure and function associated with neoplastic disease.

[Disorders of water- and electrolyte balance in a triathlon. 2 case reports and review of the literature]

Triathlon is an increasingly popular sport. The number of active triathletes in Switzerland has increased greatly in recent years. We report two participants of the Zürcher Euroman. Triathlon 1995, who presented with clinically significant water and electrolyte disturbance. The race took place on a hot day and both athletes ingested large amounts of hypoosmolar fluids during and in case 1, after the competition. Case 1 was a 27 year old woman who developed generalized seizures one hour after finishing the race. She had confusion which persisted for several hours. The initial serum sodium concentration was 118 mmol/L. Case 2 was a 29 year old man who collapsed during the triathlon and was confused for hours afterwards. He presented with a serum sodium concentration of 120 mmol/L. Both patients had massive polyuria (first hour urine output of 900 ml, and 1300 ml respectively) that decreased in parallel with the normalization of the serum sodium. The pathophysiology, differential diagnosis and therapy of electrolyte and water disturbances in triathletes is discussed in relation to our two cases and the literature is reviewed.

Metabolic complications of urinary diversions: an overview

Patients with urinary diversions present unique challenges to internists who have an important role in their long-term management. Advances in surgical techniques over the past 30 years have given rise to a number of urinary diversion procedures that use various intestinal segments. In its normal function, the intestine absorbs water and solutes. When placed in contact with the urinary stream, the intestine can create numerous metabolic abnormalities. These include bone disease, hepatobiliary disease, infection, malignancy, neurologic complications, nutritional deficiencies, and a number of electrolyte and acid-base disorders. An overview of these metabolic abnormalities and their causes is provided, as well as recommendations for screening and management of patients.

Monitoring fluid absorption using 1% ethanol-tagged glycine during operative hysteroscopy

STUDY OBJECTIVE

To assess the value of expired breath ethanol as a marker of irrigating fluid absorption during hysteroscopic surgery using 1% ethanol-tagged 1.5% glycine.

DESIGN

Prospective analysis.

SETTING

Endoscopy training center of a university hospital.

PATIENTS

Forty-eight women undergoing major hysteroscopic surgery for menorrhagia (40 transcervical endometrial resections, 8 rollerball endometrial ablations).

INTERVENTIONS

Expired breath ethanol and venous blood samples were taken before and at 10-minute intervals during surgery. Volumetric absorption of irrigating fluid was checked at the same time.

MEASUREMENTS AND MAIN RESULTS

Expired breath ethanol concentration, serum ethanol, several biochemical variables, and volume of absorbed irrigating fluid (direct and indirect) were measured. There was a linear positive correlation (r = 0.86, p <0.001) between direct vascular absorption of the irrigating fluid and expired breath ethanol concentration. Prediction can be given with 95% confidence that if the alcolmeter reading is below 0.45%, the volume of irrigating fluid absorbed is below 2000 ml. No significant correlation was seen between expired breath ethanol and indirect fluid absorption.

CONCLUSIONS

As it is not possible to distinguish direct and indirect fluid absorption during hysteroscopic surgery, measuring expired breath ethanol is insufficient to assess overall fluid balance, and continuous volumetric assessment is still required.

Fluid resuscitation following a burn injury: implications of a mathematical model of microvascular exchange

A validated mathematical model of microvascular exchange in thermally injured humans has been used to predict the consequences of different forms of resuscitation and potential modes of action of pharmaceuticals on the distribution and transport of fluid and macromolecules in the body. Specially, for 10 and/or 50 per cent burn surface area injuries, predictions are presented for no resuscitation, resuscitation with the Parkland formula (a high fluid and low protein formulation) and resuscitation with the Evans formula (a low fluid and high protein formulation). As expected, Parkland formula resuscitation leads to interstitial accumulation of excess fluid, while use of the Evans formula leads to interstitial accumulation of excessive amounts of proteins. The hypothetical effects of pharmaceuticals on the transport barrier properties of the microvascular barrier and on the highly negative tissue pressure generated postburn in the injured tissue were also investigated. Simulations predict a relatively greater amelioration of the acute postburn edema through modulation of the postburn tissue pressure effects.

Response of severely malnourished patients to preoperative parenteral nutrition: a randomized clinical trial of water and sodium restriction

Preoperative parenteral nutrition (PPN) may be beneficial for severely malnourished patients who are candidates for a major elective surgical procedure. The response to PPN, however, has not been thoroughly investigated. Expansion of the extracellular water compartment may occur in some patients, producing a further decrease in the serum albumin concentration and increasing the postoperative complications. Our aims were to investigate the occurrence of and factors associated with water and sodium retention during PPN and its impact on postoperative respiratory complications. Forty-one patients with gastrointestinal cancer and severe malnutrition (weight loss > 15% and/or serum albumin < 35 g/L) were randomly allocated to two groups receiving isocaloric isonitrogenous PPN for 10 d. The Standard PPN Group (SG, n = 19) received 70% of nonprotein calories as glucose, 45 cc of water.kg-1.d-1, and 140 mEq/d of sodium chloride; and the Modified Group (MG, n = 22) received 70% of calories as fat, 30 cc of water.kg-1.d-1, and no sodium. Weight and albumin changes, diuresis, sodium and water balances, and postoperative complications were recorded. At the end of PPN, the SG showed a higher weight gain (0.8 versus -1.5 kg, P = 0.0001) and albumin decrease (-0.7 versus 2.3 g/L, P = 0.006). Diuresis and sodium balance were greater in the SG (1,230 versus 959 mL/d, P = 0.003 and 40 versus -27 mEq/d, P = 0.001). Weight changes correlated with water (r2 = 0.46, P = 0.001) and sodium (r2 = 0.62, P = 0.0001) balances. Inappropriate responses to PPN in both groups (expansion or depletion of the extracellular water compartment) were associated with a significant increase in pulmonary postoperative complications. During PPN, extracellular water expansion--as determined by increasing weight and lowering of the serum albumin concentration--and aggressive fluid therapy to treat water and sodium depletion seem crucial to the development of postoperative respiratory complications.