IFCC recommendation on reporting results for blood glucose.

In human beings, glucose is distributed like water between erythrocytes and plasma. The molality of glucose (amount of glucose per unit water mass) is the same throughout the sample. Different water concentrations in calibrator, plasma, and erythrocyte fluid can explain some differences that are dependent on sample type, methods requiring sample dilution, and direct reading biosensors detecting molality. Different devices for the measurement of glucose detect and report fundamentally different analytical quantities. The differences exceed the maximum allowable error of glucose determinations for diagnosing and monitoring diabetes mellitus, and they complicate the treatment. The goal of the International Federation of Clinical Chemistry, Scientific Division, Working Group on Selective Electrodes (IFCC-SD WGSE) is to reach a global consensus on reporting results. The document recommends harmonizing to the concentration of glucose in plasma (with the unit mmol/l), irrespective of sample type or technology. A constant factor of 1.11 will convert measured concentration in whole blood to the equivalent concentration in plasma.

Bone loss after renal transplantation: role of hyperparathyroidism, acidosis, cyclosporine and systemic disease.

UNLABELLED: In order to determine risk factors for bone loss after renal transplantation, dual energy X-ray absorptiometry was performed in 125 renal transplant patients. The bone mineral density (BMD) was expressed as a percentage of the normal population (BMD%) and Z-score (SD from normal). The whole body, lumbar spine and femoral neck BMD% (Z-score) values were 93.9 +/- 8.9 (-0.90 SD), 91.6 +/- 14.9 (-0.98 SD) and 87 +/- 15.3 (-1.0 SD)%, respectively. Low BMD% was associated with low creatinine clearance ( < 40 mL/min: 91.6 +/- 7.9, > 40 mL/min: 95.6 +/- 8.0, p < 0.01), repeated graft loss (0: 94.4 +/- 9.1, > 1: 87.4 +/- 9.3, p < 0.05), long dialysis duration ( < 1 yr: 95.2 +/- 7.9, > 5: 90.1 +/- 10.6, p < 0.05), acidosis (bicarbonate < 21 mmol/L: 89.6 +/- 8.0, > 27: 96.7 +/- 7.2, p < 0.01), secondary and tertiary hyperparathyroidism ( < 50 ng/L: 95.9 +/- 7.1, > 200: 87.7 +/- 5.0, p < 0.01), raised alkaline phosphatase ( < 200 units/L: 95.7 +/- 7.2, > 300: 85.6 +/- 13.2, p < 0.001), osteocalcin ( < 50 microg/L: 95.2 +/- 6.7, > 100: 89.3 +/- 7.6, p < 0.01) and urinary deoxypyridinoline (< 5 nM/mM creatinine: femoral neck 89.6 +/- 10.7, > 10: 82.1 +/- 20.1, p < 0.05), low 25-OH-vitamin D ( < 10 microg/L: 91.3 +/- 9.8, > 20: 96.9 +/- 7.4, p < 0.001) and high cyclosporine concentration (0 ng/L: 98.3 +/- 7.0, > 150: 92.1 +/- 9.3, p < 0.05). Patients with clinical atherosclerosis (91.7 +/- 8.6 vs. 95.4 +/- 8.8, p < 0.01), hypoalbuminemia ( < 550 micromol/L: 87.6 +/- 13.2, > 550: 94.2 +/- 7.8, p < 0.01), renovascular disease (89.7 +/- 5.7 vs. 95.0 +/- 5.7, p < 0.05) and diabetic nephropathy (femoral neck 76.6 +/- 8.8 vs. 89.3 +/- 15.1, p < 0.01) had lower bone masses. High bone mass was associated with previous dialysis alphacalcidol therapy (0: 92.2 +/- 7.5, > 3 microg/wk: 97.3 +/- 6.9, p < 0.05). No relationships with transplantation duration, 1,25-OH-vitamin D, aluminium, calcium or steroid dose were found. No involutional changes in tertiary hyperparathyroidism could be discerned. CONCLUSION: The major threats to bone mass after renal transplantation appear to be ongoing hyperparathyroid bone disease, low renal function, acidosis, systemic disease and hypo-vitaminosis D.

Use of ion-selective electrodes for blood-electrolyte analysis. Recommendations for nomenclature, definitions and conventions. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Scientific Division Working Group on Selective Electrodes.

This paper will familiarize the reader with the terms used to describe the behavior of ion-selective electrodes, particularly in relation to their use in clinical chemistry for determination of blood electrolyte cations. It serves as an introduction to a series of papers dealing with important cations in blood, namely calcium, sodium, and potassium. The detailed relationships between the ion activity determined by means of ion-selective electrode potentiometry in undiluted specimens, and the total substance concentration measured by flame atomic-emission spectrometry are described by flow chart and equations. Adoption of a convention for reporting results is recommended. The Working Group on Selective Electrodes has taken into account recent revisions of IUPAC recommendations on nomenclature and selectivity coefficient determinations for ion-selective electrodes, and benefited from the experience of a member of the WG, who was also involved in the IUPAC discussions. Nomenclature for determined quantities follows previous IUPAC/IFCC joint recommendations.

IFCC recommended reference method for the determination of the substance concentration of ionized calcium in undiluted serum, plasma or whole blood.

A reference method is described for the determination of the substance concentration of ionized calcium in plasma by which ionized calcium (free or unbound) may be reliably determined on the basis of calibration with aqueous solutions with known concentration of ionized calcium. The composition of the calibration solutions is chosen such that the activity coefficient of the calcium ion is assumed to be identical both in the calibration solutions and in "normal" plasma, i.e. by convention, the ionic strength (Im) is 0.160 mol/kg. The convention is adopted of reporting ionized calcium measurements as concentration expressed as mmol/l. The proposed reference method for ionized calcium measurement in plasma is based on the use of a cell consisting of an external reference electrode with a saturated potassium chloride liquid/liquid junction in combination with a calcium ion-selective membrane electrode of defined construction and performance. Procedures for using the reference cell and a protocol for sample measurement are described. The preparation of the calibration solutions to be used are described in detail in Appendix A, secondary calibration solutions and check standards in Appendix B, and reference cell vessel design in Appendix C.

Recommendations for measurement of and conventions for reporting sodium and potassium by ion-selective electrodes in undiluted serum, plasma or whole blood. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). IFCC Scientific Division Working Group on Selective Electrodes.

Ion-selective electrodes (ISEs) respond to ion-activity and therefore do not sense substance concentration directly. However, it is recognized that sodium and potassium in plasma will continue to be expressed for clinical purposes in terms of substance concentration (mmol/l). A convention is proposed whereby for routine clinical purposes results of ISE measurements of sodium and potassium in undiluted plasma should be reported in terms of substance concentration (mmol/l). In specimens with normal concentrations of plasma water, total CO2, lipids, protein and pH, the values will concur with the total substance concentration as determined for example by flame atomic emission spectrometry (FAES) or ISE measurements on diluted samples. In specimens with abnormal concentrations of plasma water, the results will differ. However, under these circumstances, measurements of sodium and potassium by ISE in the undiluted sample will more appropriately reflect the activity of sodium and potassium and are therefore clinically more relevant than the determination in diluted samples. Detailed recommendations are made about practical procedures to achieve this. The recommended name for this quantity is the substance concentration of ionized sodium or ionized potassium in plasma, as opposed to total sodium or total potassium determined by, e.g. FAES, or ISE measurements on diluted samples.

Non-steroidal anti-inflammatory drugs and renal response to exercise: a comparison of indomethacin and nabumetone.

Nabumetone, a newer non-steroidal anti-inflammatory drug (NSAID) which preferentially blocks cyclo-oxygenase-2 activity, may be less nephrotoxic than indomethacin. This study tested whether nabumetone has effects different from those of indomethacin on exercise-induced changes in renal function and the renin-aldosterone system. In a randomized fashion, ten subjects were studied after indomethacin (100 mg), nabumetone (1 g) or no medication (control) administered orally at 22.00 hours on the day before each study day, and again at 8.00 hours upon arrival at the laboratory. Renal function was studied at baseline, during graded 20-min exercise sessions at 25%, 50% and 75% of the maximal oxygen uptake rate, and subsequently during two 1-h recovery periods. Heart rate, arterial blood pressure, cardiac output and plasma catecholamines at rest and during exercise were not altered by indomethacin or nabumetone. Indomethacin decreased urinary rates of excretion of 6-oxo-prostaglandin F(1alpha) (6-oxo-PGF(1alpha)) and thromboxane B(2) in all study periods. Nabumetone decreased 6-oxo-PGF(1alpha) excretion during and after exercise. Excretion rates for PGE(2) did not change. Neither indomethacin nor nabumetone changed baseline values or exercise-induced decreases in renal plasma flow or glomerular filtration rate. Indomethacin, but not nabumetone, decreased sodium excretion, urine flow rate and free water clearance. The renal response to exercise, however, remained unchanged. In contrast with nabumatone, indomethacin decreased the plasma renin concentration. Thus, during exercise, nabumetone may decrease the excretion of 6-oxo-PGF(1alpha) by inhibition of cyclo-oxygenase-1 or by inhibition of specific exercise-induced activation of cyclo-oxygenase-2, or both. None of the drugs changed the renal response to exercise. Inhibition by indomethacin of angiotensin II and thromboxane A(2) synthesis may, during exercise, counterbalance renal vasoconstriction caused by blockade of vasodilatory prostaglandins.

Effects of nitric oxide blockade and cyclosporin A on cardiovascular and renal function in normal man.

OBJECTIVE: The present study investigated whether the nitric oxide (NO) system is involved in cyclosporin A (CsA)-induced changes in cardiovascular and renal function in man. SUBJECTS AND METHODS: Ten healthy volunteers were investigated twice--with and without intake of a single dose of CsA (8 mg/kg). N(G)-monomethyl-L-arginine (L-NMMA; 3 mg/kg) was injected 4 h after study start on each day. RESULTS: There was no change in glomerular filtration rate (GFR) on the day without CsA. CsA alone did not change GFR, but after L-NMMA injection, GFR decreased significantly from 101 +/- 4 to 91 +/- 4 ml/min. L-NMMA increased renal vascular resistance with no difference between the two study days. CsA increased significantly the diastolic blood pressure (BP) by 8 +/- 2% and the heart rate (HR) by 30 +/- 4%, without changes in cardiac output L-NMMA further increased BP by around 8%, and decreased HR by 11% and cardiac output by 20% on both study days. L-NMMA decreased urinary flow rate by around 25% and renal sodium clearance from 1.1 to approximately 0.6 ml/min on both study days. CsA decreased plasma renin significantly and increased the urinary excretion rate of prostaglandin E2 (PgE2), 6-keto-prostaglandin F1alpha (6-keto-PgF1alpha) and thromboxane B2(TxB2) when compared to the control day. The urinary excretion rate of NOx and cGMP declined gradually on the control day. In contrast, there was a minor, non-significant increase in NOx and cGMP excretion after CsA, followed by a decrease (29 +/- 2 and 16 +/- 4%, respectively) after L-NMMA in parallel with the decrease in GFR. CONCLUSION: The present findings suggest that NO does not play a major role during acute CsA-induced changes in cardiovascular function and renal haemodynamics in man. Renal NO synthesis, however, may attenuate the acute CsA-induced decrease in GFR.

Effects of hyperventilation and hypocapnic/normocapnic hypoxemia on renal function and lithium clearance in humans.

BACKGROUND: Using the renal clearance of lithium as an index of proximal tubular outflow, this study tested the hypothesis that acute hypocapnic hypoxemia decreases proximal tubular reabsorption to the same extent as hypocapnic normoxemia (hyperventilation) and that this response is blunted during normocapnic hypoxemia. METHODS: Eight persons were studied on five occasions: (1) during inhalation of 10% oxygen (hypocapnic hypoxemia), (2) during hyperventilation of room air leading to carbon dioxide values similar to those with hypocapnic hypoxemia, (3) during inhalation of 10% oxygen with the addition of carbon dioxide to produce normocapnia, (4) during normal breathing of room air through the same tight-fitting face mask as used on the other study days, and (5) during breathing of room air without the face mask. RESULTS: Hypocapnic and normocapnic hypoxemia and hyperventilation increased cardiac output, respiratory minute volume, and effective renal plasma flow. Glomerular filtration rate remained unchanged on all study days. Calculated proximal tubular reabsorption decreased during hypocapnic hypoxemia and hyperventilation but remained unchanged with normocapnic hypoxemia. Sodium clearance increased slightly during hypocapnic and normocapnic hypoxemia, hyperventilation, and normocapnic normoxemia with but not without the face mask. CONCLUSIONS: The results indicate that (1) respiratory alkalosis with or without hypoxemia decreases proximal tubular reabsorption and that this effect, but not renal vasodilation or natriuresis, can be abolished by adding carbon dioxide to the hypoxic gas; (2) the increases in the effective renal plasma flow were caused by increased ventilation rather than by changes in arterial oxygen and carbon dioxide levels; and (3) the natriuresis may be secondary to increased renal perfusion, but application of a face mask also may increase sodium excretion.

Glomerular and tubular function in renal transplant patients treated with and without ciclosporin A.

The present study evaluated whether chronically administered low-dose (<5 mg/kg) ciclosporin A (CsA) affects renal haemodynamics and tubular function in renal transplant recipients (RTx) when studied at nadir CsA blood levels. The renal clearance of lithium was used as an index of proximal tubular outflow of sodium and water. Effective renal plasma flow, glomerular filtration rate, and renal clearance of lithium were studied in 67 stable non-diabetic RTx and 44 healthy controls. Forty-eight of the RTx were treated with CsA, prednisone, and azathioprine. Nineteen were treated exclusively with prednisone and azathioprine. In RTx with a good graft function (serum-creatinine <125 micromol/l), no specific CsA-induced renal haemodynamic and tubular dysfunctions were evident. In CsA-treated RTx with a slightly reduced renal function (serum creatinine 125-180 micromol/l) a decrease in fractional proximal tubular reabsorption was found. The renal clearances of urate and magnesium were comparable between RTx treated with or without CsA, and a significant correlation between glomerular filtration rate and renal clearance of urate was found. CsA-treated RTx had a significantly higher blood pressure, independent of glomerular filtration rate and segmental tubular function. In conclusion, at nadir CsA blood levels, no specific CsA-induced tubular dysfunction evaluated by the renal lithium clearance method could be demonstrated in RTx receiving chronically low-dose CsA. The hyperuricaemia commonly seen in RTx seems to be mainly caused by the reduced glomerular filtration rate.

Acute cardiovascular effect of 1,25-dihydroxycholecalciferol in essential hypertension.

A role for vitamin D in the pathophysiology of essential hypertension has frequently been suggested, but acute direct effects on blood pressure, cardiac output, renal hemodynamics, or hormones have not previously been demonstrated. The rapid effects of 1,25-dihydroxycholecalciferol (1,25-D) were assessed over 120 min after a bolus injection (0.02 microg/kg body weight) in eight men with essential hypertension and in nine healthy men. A placebo group of 10 healthy men was also included. Ionized calcium was monitored closely during the study, and was kept constant with a clamping technique. In the hypertensive patients, a transient increase in blood pressure and a reciprocal fall in cardiac output measured by a CO2 rebreathing technique (-15%, P < .05) were observed after 1,25-D injection. In the control group, both blood pressure and cardiac output remained unchanged. The glomerular filtration rate, effective renal plasma flow, and urinary sodium and water excretions were unchanged in both groups. Plasma levels of atrial natriuretic peptide at baseline were higher in the hypertensive patients than in the control subjects (P < .02); plasma levels of renin, aldosterone, norepinephrine, endothelin, and parathyroid hormone(1-84) were similar in the two groups. None of these hormones was affected during the observation time after the injection of 1,25-D. In conclusion, acute administration of 1,25-D caused a fast and likely nongenomic-mediated decrease in cardiac output in patients with essential hypertension, which together with a transient BP increase implies a 1,25-D-induced increase in total peripheral resistance. These data suggest an enhanced cardiovascular responsiveness to 1,25-D in hypertensive compared to healthy normotensive subjects.

Renal haemodynamics, sodium and water reabsorption during continuous intravenous infusion of recombinant interleukin-2.

1. Renal haemodynamics, lithium and sodium clearance were measured in 14 patients treated with recombinant interleukin-2 for metastatic renal cell carcinoma. 2. Patients were studied before and after 72 h of continuous intravenous infusion of recombinant interleukin-2 (18x10(6) i.u..24 h-1.m-2) and 48 h post therapy. Cardiac output was measured by impedance cardiography. Effective renal plasma flow and glomerular filtration rate were determined by the renal clearances of 131I-hippuran and 99mTc-diethylenetriaminepenta-acetic acid (DTPA) respectively. Renal clearance of lithium (CLi) was used as an index of proximal tubular outflow. 3. Treatment caused a transient decrease in mean arterial blood pressure and systemic vascular resistance, but cardiac output remained unchanged. Renal blood flow decreased and renal vascular resistance increased during and after treatment. Sodium clearance decreased from 1.10 (0.63/1.19) ml/min to 0.17 (0.18/0.32) ml/min (P=0.003). Glomerular filtration rate remained unchanged, whereas the median CLi decreased from 26 (17/32) ml/min to 17 (10/21) ml/min (P=0.008). Calculated absolute proximal reabsorption rate of water increased from 63 (40/69) ml/min to 71 (47/82) ml/min (P=0.04). The urinary excretion rate of thromboxane B2 and the ratio between excretion rates of thromboxane B2 and 6-keto-prostaglandin-F1alpha increased by 98% (P=0.022) and 175% (P=0.022) respectively. 4. The study suggests a specific recombinant interleukin-2-induced renal vasoconstrictor effect. Changes in renal prostaglandin synthesis may contribute to the decrease in renal blood flow. The lithium clearance data suggest that an increased proximal tubular reabsorption rate may contribute to the decreased sodium clearance during recombinant interleukin-2 treatment.

Plasma volume in acute hypoxia: comparison of a carbon monoxide rebreathing method and dye dilution with Evans' blue.

Exposure to acute hypoxia is associated with changes in body fluid homeostasis and plasma volume (PV). This study compared a dye dilution technique using Evans' blue (PV[Evans']) with a carbon monoxide (CO) rebreathing method (PV[CO]) for measurements of PV in ten normal subjects at sea level and again 24 h after rapid passive ascent to high altitude (4,350 m). Hypobaric hypoxia decreased arterial oxygen saturation to 79 (74-83)% (mean with 95% confidence intervals). The PV(Evans') remained unchanged from 3.49 (3.30-3.68) l at sea level to 3.46 (3.24-3.68) l at high altitude. In contrast PV(CO) decreased from 3.39 (3.17-3.61) l at sea level to 3.04 (2.75-3.33) l at high altitude (P < 0.05). Compared with sea level, this resulted in an increase of the mean bias between the two methods [from 0.11 (-0.05-0.27) l at sea level to 0.43 (0.26-0.60) l at high altitude] so that the ratio between PV(Evans') and PV(CO) increased from 1.04 (0.99-1.09) at sea level to 1.15 (1.06-1.24) at high altitude (P < 0.05). In conclusion, the two methods were not interchangeable as measures of hypoxia-induced changes in PV. The mechanism responsible for the bias remains unknown, but it is suggested that the results may reflect a redistribution of albumin caused by the combined effects in hypoxia of both an increased capillary permeability to albumin and a decrease in PV. As a result, the small perivascular compartment of albumin beyond the endothelium may increase without changes in the overall albumin distribution volume.

Proposal for standardizing direct-reading biosensors for blood glucose.

Direct-reading glucose biosensors sense molality (glucose per unit water mass) in the sample. With aqueous calibration, a direct-reading glucose biosensor produces higher results in blood and plasma than methods measuring concentration, theoretically by the ratio of water concentrations in calibrator and sample. To confirm this, we measured glucose in 14- blood and 40 plasma samples with the direct-reading glucose sensor in the Chiron Model 860 Blood Gas and Critical Analyte System and with our routine method (ESAT 6660; Eppendorf). The Chiron instrument is calibrated with a 10 mmol/L (180 mg/dL0 glucose calibrator (mass concentration of water = 0.99 kg/L). Assuming normal water concentrations of 0.84 and 0.93 kg/L in blood and plasma, respectively, we multiplied results from the Chiron sensor by 0.84/0.99 and 0.93/0.99 to obtain concentrations in blood and plasma. This conversion resulted in agreement of results with our routine method. An individual conversion based on hematocrit in each whole-blood sample was less satisfactory. To avoid confusion over variously measured and reported glucose results and reference values, we suggest standardization and reporting of whole-blood glucose results as equivalent plasma concentrations. This proposal may be conveniently achieved by using a commercially available reference material for glucose, NIST SRM 965.

International Federation of Clinical Chemistry (IFCC). Recommendation on mean molar activity coefficients and single ion activity coefficients of solutions for calibration of ion-selective electrodes for sodium, potassium and calcium determination.

In principle, flame photometry measures substance concentration, and ion-selective electrodes (ISEs) measure ion activity. However, the situation regarding the comparison of results from the two techniques when applied to blood plasma is complex. The problem can be approached experimentally from the point of view of calibration of ion-selective electrodes with concentration calibrators, and similar procedures are adopted for commercial ISE-based clinical analysers. Nevertheless, there is interest in the evaluation of single ion activities in blood plasma and solutions simulating its ionic composition. Solutions are proposed for calibrating ion-selective electrodes for the determination of sodium, potassium and calcium. It is recommended that the values for single ion activities derived from the Pitzer treatment of mixed electrolyte solutions be adopted, because, although this has some empirical features, it has a sounder theoretical basis than the previously used Stokes-Robinson-Bates hydration approach.

Cyclosporine-induced hypertension and decline in renal function in healthy volunteers.

OBJECTIVE: To investigate the effect of cyclosporine A (CsA; Sandimmun Neoral) on systemic and renal hemodynamics, tubular function, and sodium excretion in healthy volunteers. Furthermore, we studied whether CsA enhances the systemic and renal hemodynamic sensitivity to norepinephrine. METHODS: Eighteen healthy volunteers were administered 10 mg/kg CsA or placebo capsules in a double-blind fashion. The mean arterial blood pressure (MAP), renal vascular resistance (RVR), glomerular filtration rate (GFR), and renal clearances of lithium (CLi) and sodium (CNa) were measured for 8 h after ingestion of the capsules. Norepinephrine (2 microg/kg per h) was infused intravenously for 1.5 h into nine subjects. RESULTS: CsA increased the MAP by 17+/-2 mmHg. The GFR decreased by 18+/-2% (P < 0.001) and the RVR increased by 37+/-4% (P< 0.001) after ingestion of CsA. The CsA-induced increase in MAP preceded the CsA-induced fall in GFR. The rise in MAP was followed by an early 35+/-8/0 increase in CNa (P < 0.001). At the end of the 8 h study period, CNa decreased by 25+/-7% (P < 0.001). Using CLi, it was found that the initial natriuresis had been caused by a relative decrease both in proximal and in distal tubular reabsorption of sodium, whereas the late sodium retention was secondary to the CsA-induced fall in GFR. Infusion of norepinephrine increased the MAP, RVR, and filtration fraction, and decreased the renal plasma flow, without CsA having any additional effect. CONCLUSION: It was demonstrated that a single oral dose of CsA caused a rise in blood pressure and transient natriuresis, followed by a fall in GFR and antinatriuresis. Thus, the present study confirms and extends earlier observations that renal dysfunction and sodium retention are not the initiating events in CsA-induced hypertension. The study also affords evidence suggesting that such rises in blood pressure are not mediated by an increased sensitivity to norepinephrine.

Effects of PTH(1-34) on blood pressure, renal function, and hormones in essential hypertension: the altered pattern of reactivity may counteract raised blood pressure.

As it has been suggested that parathyroid hormone (PTH) is implicated in the pathophysiology of essential hypertension, the effects of PTH(1-34) were assessed during infusion over 120 min in ten men with essential hypertension and in ten healthy men. Ionized calcium was kept constant by a clamping technique. Mean arterial blood pressure fell slightly in the patients (116 mm Hg, median, before, and 108 mm Hg during the infusion, P < .01), but remained unchanged in the controls (median 87 mm Hg). The pulse rate rose to a similar extent in the two groups, but cardiac output, measured by the CO2 rebreathing technique, was unchanged. The glomerular filtration rate (GFR) was slightly lower in the hypertensives than in the controls at baseline (92 v 109 mL/min, P < .02), but it increased similarly during PTH infusion in both groups (+13% v +9%, medians), as did the effective renal plasma flow (+50% v +38%). The urinary rate of sodium excretion, which was similar at baseline, increased more in the patients than in the controls (+191% v +46%, P < .05); this was mainly attributable to a reduction in the tubular reabsorption of sodium. Calculations based on lithium clearance indicated that mainly the proximal tubular reabsorption of sodium decreased during PTH infusion. Baseline plasma PTH(1-84) was higher in the patients than in the controls (20.5 ng/L v 16.5 ng/L, P < .05). The baseline plasma values of renin, aldosterone, atrial natriuretic peptide, endothelin, and noradrenaline were similar in the two groups. During infusion of PTH, renin increased less in the patients than in the controls (P < .02), and aldosterone increased only in the controls (P < .01). The other hormonal values remained unchanged. In conclusion, the patients with essential hypertension had increased baseline PTH values, but nevertheless PTH had more marked vasodilative and natriuretic effects than in the controls. PTH thus seems to counteract rather than aggravate elevation of blood pressure in these patients.

Recomendações para coleta, transporte e armazenamento de sangue total para determinações simultâneas de PH, gases e eletrólitos / Recommendations on whole blood sampling, transport and storage for simultaneous determination of PH, blood gases and electrolytes

As variáveis pré-analíticas: coleta, transporte e armazenamento, podem contribuir significativamente para a imprecisão dos valores de pH, gasometria e eletrólitos. A International Federation of Clinical chemistry (IFCC), através de seus comitês em pH, Gases Arteriais e eletrólitos, tem publicado recomendações específicas com o intuito de minimizar os efeitos indesejáveis das variáveis pré-analíticas. Estes comitês se basearam na experiências de seus próprios membros, como também em artigos publicados por outros. Especificamente, os comitês têm incluído rotinas e sugestões confeccionadas pelos: IFCC Working Group on Selective Electrodes (WGSE), National Committee on Clinical Laboratory Standards (NCCLS), Eletrolyte/Blood Gás Division of the American Association for Clinical Chemistry (AACC). Este artigo irá familiarizar o leitor com os efeitos de diferentes tipos de frascos e anticoagulantes. Também serão discutidos aspectos importantes dos procedimentos de coleta, incluindo o estado do paciente e as precauções especiais a serem tomadas quando utilizam-se catéteres ou cânulas para a coleta. Serão vistos também as diferentes normas para o armazenamento e tranporte das amostras, para as análises gasométrica e eletrolítica.

Haematological status in elite long-distance runners: influence of body composition.

In 10 female and eight male Danish elite middle- and long-distance runners, haematological status, including blood volume, was examined. Haemoglobin, haematocrit and serum (s)-ferritin concentrations were all within the normal range. In both men and women, blood volume, plasma volume and erythrocyte volume were increased in relation to various reference values. However, the runners had a low body weight due to a reduced fat level, 9.5% (7.3-15.1%) fat for the women, 5.9% (5.0-8.8%) fat (median and ranges) for the men, measured by dual-energy X-ray absorptiometry (DEXA) scanning. When the runners' body weights were 'normalized' to a reference population (25% fat for women, 15% fat for men), only plasma volume remained increased in relation to body weight for the women, whereas all the volumes remained increased for the men. This confirms that endurance training induces a true increased plasma volume. The lower erythrocyte volume in the women compared with the men could be a consequence of the generally poorer iron status in the women, indicating that a combination of haemolysis, menstruation and low caloric (iron) intake makes it difficult for trained women to obtain optimal effects on erythrocyte volume equal to those obtained by trained men. Furthermore, the study emphasizes the importance of taking body composition into consideration when comparing well-trained athletes with a reference population.

Endogenous versus exogenous lithium clearance for evaluation of dopamine-induced changes in renal tubular function.

1. The present randomized, double-blind cross-over study compared endogenous and exogenous lithium clearance (CLi) for estimation of the effect of dopamine on tubular sodium reabsorption. Twelve normal, salt-repleted male subjects were investigated on three different occasions with either placebo or 450 mg or 600 mg of lithium given in random order at 22.00 hours. After an overnight fast, renal clearance studies were performed during a 1 h baseline period and subsequently during the second hour of an infusion of 3 micrograms min-1 kg-1 of dopamine. 2. Baseline values of endogenous CLi and fractional excretion of lithium (FELi) [27.0 (23.5-30.5) ml/min and 24.2 (20.3-28.2)% (means with 95% confidence interval)] were lower than exogenous values [lithium, 450 mg: 32.7 (29.9-35.4) ml/min (P < 0.05) and 27.4 (25.2-29.6)% (P < 0.05); lithium, 600 mg: 33.4 (29.2-37.6)ml/min (P < 0.05) and 28.6 (26.3-31.0)% (P < 0.01)]. Both test doses of lithium increased the baseline sodium clearance (CNa), but glomerular filtration rate and urine flow rate remained unchanged. 3. Dopamine increased CNa to similar values on the three study days. CLi increased to 40.9 (35.5-46.5) ml/min (endogenous lithium, P < 0.001), 43.2 (40.8-45.6) ml/min (450 mg of lithium, P < 0.01) and 44.9 (41.3-48.4) ml/min (600 mg of lithium, P < 0.001), respectively. FELi increased to 32.2 (27.5-37.0)% (P < 0.01), 35.4 (33.0-37.7)% (P < 0.01) and 35.9 (32.8-38.9)% (P < 0.01), respectively. Values during dopamine infusion did not differ significantly. 4. The lower baseline values of endogenous CLi and FELi compared with exogenous values suggest that CLi in humans depends on the plasma concentrations of lithium. However, the effect of dopamine on CLi and FELi was expressed to the same extent with endogenous and exogenous lithium, indicating that the two methods are interchangeable for estimation of dopamine-induced changes in tubular function.