POSTURAL CHANGES IN PLASMA VOLUME IN HYPOALBUMINEMIA

Patient hydration: a major source of laboratory uncertainty

Movement of body water from compartment to compartment during any time period is attributable to forces active within and upon each space. The result of these forces leads to transfer of water between intravascular and extravascular compartments, as well as shifts between extracellular and intracellular spaces. The importance of these shifts and of the associated mechanism was described by Ernest Starling in 1896 in very much the same manner as it is viewed today. The end result of fluid transfer and its physiological and laboratory consequences has not been fully appreciated. Despite awareness that fluid shifts can affect laboratory analytical results, little recent investigation has addressed the problem in the routine clinical laboratory. Thus, the potential for significant misinterpretation remains. For example, it is known that individual laboratory test values can vary widely, depending on many factors including the subject's posture during and immediately before phlebotomy, leading to significant changes in the interpretation of blood analyte values. Furthermore, a variety of ubiquitous environmental effects have additional impact on fluid distribution and thus on test values. In other words, patient hydration status is a major pre-analytical variable that needs to be addressed by the clinical laboratory. The need to adjust data for patient hydration status is especially important in the case of colloid analytes for which the dynamic range includes a narrow "gray zone" where hydration changes of a few percentage points can change the clinical implications. The crucial importance of this adjustment is underscored by the fact that neither the testing laboratory nor the clinician are aware of this unseen circumstance and are thus compelled to work with data that do not necessarily reflect the clinical situation.

Effect of posture on sodium excretion and diuretic efficacy in nephrotic patients

It is well known that posture affects natriuresis in cirrhosis and heart failure. This study evaluates the role of posture on spontaneous urinary salt excretion (U(Na)V) and diuretic-induced natriuresis in nephrotic patients with mild renal impairment. U(Na)V and plasma concentrations of the main hormones involved in sodium regulation were evaluated at baseline (Baseline) and after furosemide administration (20 mg intravenously at 8:00 AM [Diuretic]) in seven nephrotic patients with mild renal impairment (creatinine clearance, 68.5 +/- 7.6 mL/min) in either the supine or upright position for 6 hours (from 8:00 AM to 2:00 PM). At baseline, U(Na)V was greater in the supine than upright position (sodium, 51.8 +/- 6.2 versus 38.3 +/- 6.1 mEq/d; P: < 0.01). Similarly, furosemide was more effective in increasing U(Na)V in the supine (sodium, 51.8 +/- 6.2 to 87.4 +/- 9.1 mEq/d; P: < 0.005) than upright position (sodium, 38.3 +/- 6.1 to 59.0 +/- 6.8 mEq/d; P: = not significant). Consequently, body weight decreased in the supine but not the upright position (-0.73 +/- 0.15 versus -0.17 +/- 0.22 kg; P: < 0. 05). Peripheral renin activity (PRA) and plasma aldosterone (Aldo) concentrations were greater in the upright than supine position at both Baseline and Diuretic. A similar pattern was observed for hematocrit, used as an index of plasma volume. In addition, a positive correlation was detected between hematocrit and PRA (r = 0.89; P: < 0.001) in the upright position. Postural changes did not influence plasma concentrations of atrial natriuretic peptide. These data indicate that in nephrotic patients with mild impairment of glomerular filtration rate, the upright position causes a reduction in plasma volume; this hypovolemia activates the renin-Aldo system responsible for sodium retention in unstimulated conditions and a blunted natriuretic response to furosemide.

Dilutional hyponatremia in pre-eclampsia

OBJECTIVE

The objective of this report is to describe a defect in water metabolism, characterized by hyponatremia, in patients with pre-eclampsia-induced nephrotic syndrom.

STUDY DESIGN

This was an observational study of 3 women.

RESULTS

Hyponatremia was observed in 3 women with pre-eclampsia characterized by various extrarenal manifestations, as well as by nephrotic syndrome with normal or nearly normal renal function. Restriction in water intake partially corrected hyponatremia before delivery in each case, and no complications were observed in the neonates. The mechanism of impaired excretion of water in these patients is proposed to involve persistent and inappropriate production of vasopressin through stimulation of the nonosmotic mechanism for vasopressin secretion in response to a reduction in effective plasma volume.

CONCLUSIONS

These results indicate for the first time that women with pre-eclampsia are, at least when nephrotic, at risk for development of dilutional hyponatremia, which can cause neurologic complications that simulate those of eclampsia.

A critique of the overfill hypothesis of sodium and water retention in the nephrotic syndrome

Recent reviews have claimed that the majority of patients with the nephrotic syndrome have plasma volume expansion (that is, they are overfilled). Here we attempt to re-establish balance to the debate on body fluid volume status in nephrotic patients by: (a) discussing the conflicting literature on plasma volume measurements in the nephrotic syndrome; (b) providing alternate explanations for data purporting to support an overfill hypothesis in the nephrotic syndrome; (c) emphasizing secondary neurohumoral responses that support underfilling at least as frequently as overfilling; and (d) emphasizing the clinical importance of fluid assessment in the individual patient with the nephrotic syndrome particularly in relation to diuretic use.

Pronounced and rapid plasma volume reduction upon quiet standing as revealed by a novel approach to the determination of the intravascular volume change

Plasma volume (PV) changes to 15 min quiet standing were analysed (Hb/Hct-alterations) in two studies (nine and 11 healthy males). Data confirmed and extended our findings that blood, arterial or venous, sampled on standing fails to reveal the induced overall haemoconcentration (PV loss). First, standing led to markedly incomplete mixing of blood between circulatory compartments. Secondly, with sampling of antecubital venous blood, haemoconcentration was strongly affected by regional plasma loss and, apparently equally important, by regional blood flow. These difficulties were circumvented, however, by the finding that the PV restitution (haemoconcentration) in the recumbent subject after standing fitted invariably a monoexponential function with striking precision. It allowed, by extrapolation, a seemingly superior definition of the PV reduction at the very end of standing as supported by the fact that PV changes from Hb/Hct and from IgM protein concentration changes were similar, refuting that Fcell-changes contributed to the pronounced Hb/Hct changes. The described novel approach revealed a nicely reproducible PV loss of no less than 692 +/- 46 mL (18.1 +/- 0.6%, Study I; 18.4 +/- 0.5%, Study II), or approximately 11% reduction of blood volume, showing that quiet standing leads to a much more rapid and haemodynamically important decrease in PV than reported previously. Yet, PV was virtually restored within 20 min of recumbency after standing, with 50% recovery within 6 min and regain of as much as 70 mL in the very first min. The latter data indicate that the body possesses a surprising capacity for rapid fluid transfer from the extra- to the intravascular space.

Improving malnutrition documentation enhances reimbursement

Diagnosis coding for malnutrition can positively affect hospital reimbursements. Our goal was to quantify the possible increase in reimbursements when the diagnosis of malnutrition was identified and appropriately coded. A sample of 234 cases representing 14% of Medicare patients seen from March 1991 through February 1992 at Allenmore Hospital in Tacoma, Wash, was retrospectively reviewed. Malnutrition diagnoses (using ICD-9-CM codes) were assessed according to established criteria. Ninety-four cases (39.7%) met the criteria for malnutrition. Seven demonstrated increased reimbursement, totaling $12,326 for the sample. Length of hospital stay was significantly longer in the malnourished group (P = .001). The results indicated a need for an improved system of documenting and coding malnutrition diagnoses for improved identification and reimbursement enhancement purposes. An example of criteria used for each malnutrition ICD-9-CM diagnosis code and a policy defining the criteria usage are shown. A nutrition assessment form, which includes each malnutrition ICD-9-CM code title for enhanced interdisciplinary communication leading to improved coding of malnutrition diagnoses, is also shown. We conclude that effective identification of malnutrition leading to enhanced reimbursement strengthens the leadership potential of hospital dietitians and improves hospital revenues. Additionally, we suggest that such a system initiates a process that may lead to improved, cost-effective treatment of persons identified as being malnourished and provide a foundation for surviving within the future health care reform environment.

Intra- and extrarenal factors of oedema formation in the nephrotic syndrome

The role of intra- and extrarenal factors in oedema formation in children with nephrotic syndrome is reviewed. Oedema reflects an abnormal accumulation of fluid within the interstitial tissue. At the capillary level oedema develops when increased lymph flow is no longer effective for the removal of interstitial fluid and the maintenance of intravascular volume. Alterations of intrarenal haemodynamics and tubular sodium reabsorption contribute to sodium retention. Recent studies suggest that during oedema formation reduced effective circulatory volume triggers changes in various hormonal systems, such as renin-angiotensin-aldosterone, noradrenaline, dopamine, vasopressin, prostaglandins and natriuretic factors, which contribute to sodium and water retention. It appears that the release of atrial natriuretic peptide following central volume expansion is responsible for the increased urine flow and natriuresis after intravenous administration of albumin.

A study on oedema mechanism in nephrotic syndrome

Colloid osmotic pressure in plasma (COPp) and interstitial fluid (COPi), plasma volume (PV) and interstitial fluid volume (IFV) were measured in 14 patients with hypoproteinaemia due to glomerulonephritis and in five healthy controls. In controls, COPp averaged 24.2 mmHg and COPi 12.0 mmHg. In patients with COPp above 12 mmHg, COPi was reduced nearly identical to the fall in COPp. The transcapillary COP gradient (COPp-COPi) was maintained, and PV and IFV were unchanged. When COPp was reduced below 12 mmHg, the transcapillary COP gradient was decreased. Both IFV increased and renal fluid retention occurred. This study demonstrates the relationship between COPp, transcapillary fluid transport, and renal fluid retention in nephrotic syndrome.

Effect of changes in posture on circulatory homeostasis in patients with the nephrotic syndrome

To assess whether the upright posture causes circulatory hypovolaemia in patients with the nephrotic syndrome (NS), we studied 12 subjects with NS and 12 healthy subjects during recumbency, 110 min of standing, followed again by recumbency. Control blood-pressure was 134/88 +/- 4/3 mmHg in the patients and 113/75 +/- 2/3 mmHg in the normal subjects (P less than 0.01), and remained higher in the patients throughout the procedure. Heart rate was continuously higher in the patients (P less than 0.05), but acceleration on standing was normal. The blood volume, which was not different during recumbency, had fallen below that in normal subjects after 25 min of standing (P less than 0.05), due to excessive plasma volume reduction (-16.8 +/- 0.8% in the patients against -11.7 +/- 1.2% in the normals, P less than 0.02). Plasma renin activity (PRA) was higher in the patients while recumbent (P less than 0.001) but not during standing, due to a blunted response in some. No significant differences in plasma noradrenaline were found, but four patients reacted with an excessive rise in plasma noradrenaline and heart rate. This subset, which had high PRA levels as well, comprised the only subject who experienced orthostatic hypotension. It is concluded that during standing an excessive drop in plasma volume leads to a lowered blood volume in NS patients. This forms a paradox with the heart rate acceleration and noradrenaline levels, which were mostly normal, and with the blood-pressure, which remained slightly elevated. Even in a few patients with enhanced stimulation of heart rate and noradrenaline, blood-pressure was found to be high in the majority of cases. PRA was usually found to be increased but, in part, independent of posture.

Increases in serum lipid and lipoprotein levels with movement from the supine to standing position in adult men and women

The effect of movement from the supine to the standing position on the magnitude of change in serum lipid and lipoprotein levels and its impact on the prediction of risk for coronary heart disease was investigated in 23 male and 18 female subjects. The mean age and body weight of the men was 34 years and 93 kg, respectively, while those of women were 36 years and 71 kg. Thirty minutes of standing following thirty minutes in the supine position was associated with hemoconcentration and a significant (P less than 0.05) plasma volume reduction of -13.8% for men and women combined. Posture-related increases in serum lipids and lipoproteins were similar among both men and women and averaged +12% for triglycerides, +9.3% for total cholesterol, +9.0% for low-density lipoprotein + very low-density lipoprotein cholesterol, and +10.4% for high-density lipoprotein cholesterol. Among men, the latter increased from 41.4 to 45.6 mg X dl-1 while among women, the increase was from 58.0 to 64.3 mg X dl-1. The total cholesterol/high-density lipoprotein cholesterol ratio was unaffected by the change in body position, thus strengthening the reliability of this ratio as a coronary heart disease risk measure. Our findings indicate that body position at time of blood withdrawal significantly influences lipid and lipoprotein levels, and, depending on the absolute concentration values of total or high-density lipoprotein cholesterol, can alter the predictive risk for coronary heart disease. Heart disease. Heart disease risk based on the Framingham probability tables and the multiplier for high-density lipoprotein cholesterol is unaffected by the change in body position.

Rapidly declining serum albumin values in newly hospitalized patients: prevalence, severity, and contributory factors

We had noted that a number of hospitalized patients showed abnormally low serum albumin levels within a few days of admission, although the albumin had been normal at admission. Since this rapid decline in albumin could not be accounted for on the basis of starvation, we hypothesized that the changes were due to the increase in intravascular fluid volume which normally occurs with assumption of the recumbent position. Since albumin is often a nutritional screening parameter in hospitalized patients, it is important to ascertain the incidence of such profound changes in albumin as well as to identify possible causes for this change. A survey of 34 concurrent hospital admissions showed that 28 out of 34 (82%) patients had a decline in serum albumin within 5 days of hospitalization. These 28 patients had a decrease of 0.5 +/- 0.09 g/dl. Twenty-five additional patients were studied in order to elucidate causative factors. Twenty out of the 25 showed a decrease in serum albumin within 5 days of admission (mean decrease 0.5 +/- 0.05 g/dl). Hemoglobins in these patients decreased by a mean of 1.1 +/- 0.34 g/dl (p less than 0.01), but BUN and uric acid levels did not change significantly. The one factor common to all patients with declining albumin values was change in posture. All patients were ambulatory at the time of the initial albumin determination but were on bedrest for at least 6 1/2 hours before the second determination. The findings indicate that most hospitalized patients have significant changes in serum albumin levels which occur with change in posture. If the albumin level is to be used as a nutritional indicator, the patient's position at the time of phlebotomy is essential for accurate interpretation of results.

Diurnal variations in cobalamin binding plasma proteins

The diurnal variations in cobalamin-binding plasma proteins were studied in 10 healthy volunteers. The unsaturated cobalamin-binding capacities of transcobalamins (TC-II and R-binders), P-cobalamin and P-protein were measured every third hour during 24h. Only small variations within an interval of +/- 20% were found. Highly significant decrements during the night were a uniform finding. After correction for variations of total plasma protein, the changes became less prominent, but still significant for P-cobalamin and P-R-binders. Hence the mean values of P-R-binders and P-cobalamin were 113 and 533 pmol/1 at 9:00 h, and decreased 12 and 8%, respectively, at 3:00 h. When using cobalamin binding plasma proteins in the monitoring of various malignant, haematological and autoimmune disorders, the specimens should, therefore, be collected at defined hours and in a uniform posture.

Effects of posture on concentrations of blood constituents in healthy adults: practical application of blood specimen collection procedures recommended by the Scandinavian Committee on Reference Values

Different procedures for the collection of blood for the determination of reference values in healthy adults have been subjected to practical testing. The Scandinavian Committee on Reference Values suggested that subjects lying in bed after an overnight sleep and ambulatory individuals, after 15 min of sitting in a chair, were two suitable and different reference populations. In forty subjects we found an increase from lying to sitting position of about 6.5% in the serum concentrations of proteins, enzymes and lipids. The corresponding increases for S-calcium and B-haemoglobin were approximately 3% whereas S-thyroxine, unexpectedly, changed by 11%. There were no significant changes of potassium and sodium values. For some constituents the changes were age and sex-dependent being greater in a group of elderly women as compared to a group of younger men. After 1 h of recumbency the concentrations of the constituents generally returned to those in the initial, lying position.