Studies on kinetics of albumin in uraemic patients on chronic haemodialysis: evidence of interstitial albumin wash-down

Summary. Albumin-kinetic studies were performed in nine uraemic patients without oedema on chronic haemodialysis and in seven normal controls in order to determine microvascular leakiness and thereby, during steady state, lymph drainage of albumin. Transvascular escape rate of albumin [TER_alb, i.e. the fraction of intravascular mass (IVM_alb) passing into, or returning from, the extravascular space per unit time] and the distribution ratio (DR_alb) between IvMalh and total albumin mass were determined from intravenously injected radioiodinated serum albumin. Before haemodialysis, TER_alb was significantly elevated (mean 9·6%IVM_alb h¹, range 5·9–14) as compared to the value 15 h after haemodialysis (mean 7–3, range 5·2–11, P < 0·02) and to controls (mean 5·9, range 4·3–7·4, P < 0·01). Average DR_alb, (mean 0·54, range 0·44–0·69) was clearly elevated in patients with respect to controls (mean 0·44, range 0·42–0·48, P < 0·01), and the extravascular mass of albumin was significantly decreased (mean 27.9 μmol kg¹, range 14·1–41·2 n?. mean 35·9, range 27·1–43·8, P < 0·05). We interpret the results as to indicate increased transvascular filtration of albumin in microcirculatory beds with permeable capillaries (splanchnic organs), in between the haemodialysis treatment, and filtration of protein-poor fluid in areas with ‘tight’ capillaries (skeletal muscle, cutis) resulting in interstitial space protein depletion here. As the patients were considered to be in steady state during the measurements, the increased TER_alh indicates increased lymph flux of albumin. The interstitial space protein ’wash-down’ and increased lymph drainage probably serve as oedema prevention.     

Protein-kinetic and haemodynamic studies in patients with liver cirrhosis. Evidence of a lymph-imbalance theory of ascites formation

Summary. Lymph drainage, splanchnic vascular pressures, plasma volume (PV), plasma renin (PRC) and aldosterone (PAC) concentrations were studied in different groups of patients with cirrhosis: I, patients who had never had ascites (n=17), II, patients with former but no actual ascites (n= 19), III, patients with slight or moderate ascites (n= 25), and IV, patients with tense ascites (n = 27). Lymph drainage, determined as TER_alb (the fraction of intravascular albumin mass (IVMaib), which leaves/returns into the vascular space per hour) was significantly elevated in cirrhotic patients (11.5% IVM_alb-h^-1) as compared to normal controls (5.9,P<0.001). TER_alb in patients with tense ascites (group IV) was on the average 8-4% IVMaib-h^-1, a value which is significantly above normal (P<0.05), but significantly below those of groups I, II and III (12.5,13.4,12.6,P<0.01). Wedged hepatic venous pressure increased from group I to IV: 16, 22, 25 and 34 mmHg, respectively (P<0.01). Inferior vena caval pressure in group IV (15 mmHg) was significantly above those of group III (8 mmHg) and group I+11 (6 mmHg), (P<0–01). From group I to III, PV increased significantly (3125, 3610, 3870 ml, P<0.01). In the ascitic patients PV was constant or fell slightly in patients with tense ascites (3730 ml). PRC in untreated patients with tense ascites (IV) was 287 mIU-1^-1, as compared to group III, I and normal controls (94, 50, 15, P<0.01). A similar pattern was found with respect to PAC. The results suggest that an imbalance between enhanced protein and fluid filtration (consequent on portal hypertension) on one side, and a relatively insufficient lymphatic drainage on the other side plays a substantial role in the pathogenesis of ascites in cirrhosis. The results do not support a progressive plasma volume expansion as the main cause of cirrhotic ascites.     

Pharmacokinetics and safety of bromotetrandrine (BrTet, W198) after single-dose intravenous administration in healthy Chinese volunteers

Objective: To investigate the safety and pharmacokinetics of bromotetrandrine (BrTet, W198), a novel inhibitor of P‐glycoprotein (P‐gp), after single‐dose i.v. infusion in healthy Chinese volunteers. Methods: We conducted a randomized, dose‐escalating, phase I clinical study for that purpose. Thirty healthy subjects received BrTet at the doses of 10, 20 or 30 mg/m² by i.v. infusion. Plasma and urine concentrations of bromotetrandrine were determined by using a liquid chromatography–tandem mass spectrometric (LC/MS/MS) method. AUC was calculated by the trapezoidal rule extrapolation method. C_max, T_max, t_1/2α, t_1/2β, Cl and V_d were compiled from the plasma concentration–time data. Results: Bromotetrandrine was generally well tolerated at all doses. No serious or severe adverse events were found in the study. The pharmacokinetic parameters of BrTet after single i.v. infusion doses of BrTet 10, 20 and 30 mg/m² were as follows: T_max were 1·5 h in three groups, C_max were 24·79, 39·59 and 64·31 μg/L, t_1/2α were 0·37, 0·29 and 0·30 h, t_1/2β were 62·88, 56·45 and 52·20 h. AUC_0–194h were 345·83, 688·15 and 1096·28 μg h/L, Cl were 23·68, 25·69 and 25·66 L h/m², V_d were 157·73,156·96 and 140·73 L/m². In urine, the total eliminate rate of originate compound was 0·61 ± 0·19%. Conclusions: This study suggested that bromotetrandrine was well tolerated in healthy volunteers within the dose range evaluated. The pharmacokinetics parameters of bromotetrandrine indicated that the compound was rapidly distributed and accumulated in the tissues, and slowly cleared from plasma, which supported the use of BrTet for a once or twice dosing per chemotherapy cycle.     

An 18oxygen inhalation method for determination of total body formation of nitric oxide in humans

The formation of nitric oxide (NO) and the subsequent conversion of the NO formed into nitrate require molecular oxygen. Based on this fact, we have recently developed a method using inhalation of the stable oxygen isotope, i.e. ¹⁸O₂, to determine total formation of NO in small laboratory animals. The method has now been further developed to be applicable also in humans. Five healthy awake male subjects inhaled a gas mixture of unlabelled and 18-labelled oxygen (approximate ratio 4:1) in nitrogen from a closed breathing system equipped with eliminators for carbon dioxide and water vapour. The ratio of unlabelled to 18-labelled oxygen, as well as the total oxygen concentration during the inhalation, were monitored. Venous blood samples were taken before and after the inhalation for analysis of unlabelled and ¹⁸O-labelled nitrate by gas chromatography/mass spectrometry. The procedure was repeated with the same protocol on a later occasion, during ongoing treatment with the NO synthesis inhibitor N^G-monomethyl- L -arginine ( L -NMMA). The average nitrate level in plasma in the absence of L -NMMA was 26 μmol l^–1. The rate of total synthesis of NO was estimated to be 0·38 ± 0·06 μmol kg^–1 h^–1, corresponding to a total body formation of 600–700 μmol/24 h in an adult male. Infusion of L -NMMA caused an increase in mean arterial blood pressure from 86 ± 4 to 99 ± 5 mmHg (P<0·05). The average plasma level of nitrate during infusion of L -NMMA was 24 μmol l^–1. NO formation during infusion of L -NMMA was 0·17 ± 0·03 μmol kg^–1 h^–1, i.e. significantly (P<0·05) lower than in the absence of L -NMMA. We suggest that the described method allows direct determination of total NO formation in man. The method may be useful in the study of various experimental and pathophysiological conditions affecting NO formation.     

Effects of atriopeptin III on renal function, regional blood flows and left ventricular function in conscious dogs in presence or absence of hypovolaemia

Abstract. The effects of atriopeptin III (AP III) on the left ventricular and renal functions were studied in thirteen chronically instrumented conscious dogs and compared to those of the solvent (saline). In the normovolaemic state, an AP III infusion (1 μg kg^-1 min^-1 i.v.) had no effects on heart rate, on mean arterial or left ventricular pressure, on (dP/dt) Max (2989±119 vs. 3007±155 mmHg s^-1; NS) or on the relaxation rate. The left ventricular endocardial and epicardial coronary blood flows (radioactive microspheres) and the renal flow in the outer cortex (707–683 ml (min^-1 100 g^-1); NS) or in the inner cortex (563–570; NS) were also insignificantly affected by AP III infusion. However, AP III increased urinary flow from 24±6 to 36±7 ml h^-1 (P<0·025) and the Na⁺ and Cl^- excretions by 92 and 98%, respectively, (P<0·025 and P<0·05 vs. saline group) without altering significantly K⁺, urea and creatinine eliminations. In the moderately hypovolaemic state (mean reduction in renal flow: outer cortex -15%; P<0·05, inner cortex -5%; NS), AP III infusion at two doses (1 and 3 μg kg^-1 min^-1) still had no effects on arterial pressure and on the indexes of left ventricular inotropic state and relaxation but in this setting, the diuretic effect of AP III became variable. Five dogs markedly increased their excretion of water, Na⁺ and Cl^- whereas no change was noted in the seven remaining dogs. Regional renal blood flows and urinary output before infusion were similar in the responders and non-responders but the mean arterial pressure (81±2 vs. 73±3 mmHg; P<0·01) was lower in the non-responders. It is concluded that AP III has no effect on left ventricular contractility or on the coronary vasculature; at small doses, its diuretic effects appear independent of a renal vasodilation and are rapidly blunted in the presence of hypotension.     

A limited sampling strategy for estimating mycophenolic acid area under the curve in adult heart transplant patients treated with concomitant cyclosporine

Objective: Heart transplantation studies have shown a relationship between the mycophenolic acid area under the curve (AUC) 0–12 h (MPA AUC_0–12h) values and risk of acute rejection episodes and fewer side‐effects in patient receiving cyclosporine during the first year post‐transplant. However, measurement of full AUC is costly and time consuming and in this case it is an impractical approach to drug monitoring. Therefore, the authors describe a limited sampling strategy to estimate the MPA AUC_0–12h value in adult heart transplant recipients. Methods: Ninety MPA pharmacokinetic (PK) profiles were studied. The samples were collected immediately before and 0·5, 1, 1·5, 2, 2·5, 3, 4, 6, 9, 12 h after the morning dose of mycophenolate mofetil (MMF) following an overnight fast. PK profiles were determined at 6–8 weeks, 6, 12 months and more than 1 year after transplantation. Using stepwise multiple linear regression analysis a sampling strategy from 60 of PK profiles was obtained and next the bias and precision of the model were evaluated in another 30 PK profiles. Results: The three‐point model using C_0·5h, C_1h, C_2h was found to be superior to all other models tested (r² = 0·841). The regression equation for AUC estimation which gave the best fit to this model is: 9·69 + 0·63C_0·5 + 0·61C₁ + 2·20C₂. Using that model 63 of the 90 (70%) full AUC values were estimated within 15% of their actual value. For the best‐fit model, the mean prediction error was 3·2%, with 95% confidence intervals for prediction error to range from ?42·2% to 40·3%. All other models which use one, two or three time‐points over the first 2 h are poorer predictors of the full AUC than the model above. Conclusion: The proposed three time‐point equation to estimate AUC will be helpful in optimizing immunosuppressive therapy in heart transplantation.     

Increased systemic microvascular albumin flux in septic shock

Lymph/plasma (L/P) albumin ratios were followed in a patient with a traumatic thoracic duct lymph fistula, during septic shock when lymph flow was high and at recovery when lymph flow was low. Higher albumin ratios were found during the former. On both occassions, the P-L difference of radioactive counts/min per gram was followed for 6 h after i.v. injection of ⁵¹Cr human serum albumin (HSA). Equilibration half times between plasma and lymph amounted to 0.85 h during septic shock and 2.49 h at recovery. The data indicate that systemic microvascular albumin flux had increased during shock in our patient. Increased permeability may have been responsible.     

Permselectivity of the liver blood-lymph (ascitic fluid) barrier to macromolecules in decompensated cirrhosis: relation to calculated pore-size

Summary. This study was undertaken to investigate permselectivity of the liver blood-lymph (ascitic fluid) barrier to endogeneous rnarcomolecules in patients with decompensated cirrhosis. Albumin (mol wt 69,000), immunoglobulin-G (mol wt 160,000) and immunoglobulin-M (mol wt 900,000) were determined in plasma and ascitic fluid from 13 cirrhotic patients. As previously substantiated in patients with cirrhosis, the ascitic fluid/plasma concentration ratio (R) of a protein is proportional to the transport rate from blood to lymph (ascitic fluid). Mean R_alh= 0·28 and R_IgG= 0·29 were identical, but significantly higher than, R_IgM= 0·18 (P < 0·01). R_alh was directly correlated to R_IgG (r= 0·97, P < 0·001) and to R_IgM (r= 0·78, P < 0·005). Mean R_IgM/R_alh= 1·03, which expresses the relative flux rates between IgG and albumin, was significantly above the ratio between the free diffusion coefficients (D_IgM/D_alb= 0·64, P < 0·01). Mean R_IgM/R_alh= 0·61 was significantly above D_IgM/D_alB= 0·39 (P < 0·05) and significantly below unity (P<0.0l). The resdts are best explained by filtration as the dominant mechanism of the liver blood-lymph (ascitic fluid) exchange of endogeneous macromolecules. A significant ‘sieving’ is present in this barrier to the largest macromolecule (IgM). Calculations of pore-size equivalent to the observed permselectivity of macromolecules suggest microvascular gaps (or channels) with an average radius about 300 Å, i.e. in the lower end of the range of gaps in normal liver sinusoids (from 200 to 5000 Å).     

The lymphocyte Na+/H+ antiport: activation in primary hypertension and during chronic NaCl-loading

Abstract. Increased activity of the Na⁺/H⁺ antiport may be a major abnormality in essential hypertension. The activity of this transport system was investigated in lymphocytes from 13 patients with untreated essential hypertension (Ht) and 13 normotensive control subjects (Nt) on an ad libitum (130–170 mmol d^-1) NaCl intake. Furthermore, the effects of different states of NaCl balance on lymphocyte Na⁺/H⁺ antiport were evaluated in two groups of Nt volunteers receiving 20 vs. 300 mmol d^-1 (n= 8) and 85 vs. 200 mmol d^-1 (n= 14) of NaCl for 1 week each and in seven Ht patients (20 vs. 300 mmol NaCl d^-1 for 1 week each). Additionally, during the 20 and 300 mmol/d NaCl intake red blood cell membrane transport was studied in eight subjects. For the determination of lymphocyte antiport activity, cells were loaded with the cytosolic pH (pH_i) indicator bis-carboxyethyl carboxyfluorescein (BCECF-AM) and acidified by addition of different amounts of Na⁺-propionate (5–40 mM). Initial pH_i-recovery was taken as the activity of the antiport system and plotted against pH_i-values after acidification. Non-linear regression analysis yielded higher ’apparent’ maximal transport rates in Ht than Nt (Nt: 2·00 pL 0·22; Ht: (3·81 pL 0·59)·10^-3 s^-1; P < 0·025). In contrast, baseline pH_i-values and pH_i-values at half-maximal activity (pK) were identical in Nt and Ht. In normotensive control subjects on an NaCl intake of 20, 85, 200 and 300 mmol d^-1 for 7 d, ’apparent’ maximal transport rates averaged 2.75 0·20, 2·89 0·17, 2·81 ± 0·18 and (3·62 ± 0·25) · 10^-3 s^-1, respectively. Thus, antiport activity was significantly (P < 0·05) stimulated on the 300 mmol d^-1 intake as compared to the three other NaCl intakes. The extreme intakes of NaCl (20 vs. 300 mmol d^-1) in normotensive volunteers did not affect the erythrocyte Na⁺/K⁺ pump, Na⁺/K⁺ cotransport and Na⁺/Li⁺ countertransport. Our study supports the concept that a group of patients with primary hypertension exhibit an activated Na⁺/H⁺ antiport. Furthermore, our data demonstrate that a chronic high intake of NaCl is associated with an increase in lymphocyte antiport activity towards the high values observed in primary hypertension.     

Interactions of stress hormones on lipid and carbohydrate metabolism in man with partial insulin deficiency

Abstract. The metabolic responses to 4-h infusions of adrenaline (3 μg kg^-1 h^-1) and cortisol (10 mg m^-2 h^-1 for 2 h followed by 5 mg m^-2 h^-1 for 2 h), separately and in combination, have been studied in six healthy subjects with concurrent somatostatin infusion (250 μg h^-1). A combined infusion of adrenaline, cortisol, glucagon (180 ng kg^-1 h^-1) and somatostatin has also been studied. Somatostatin plus adrenaline and somatostatin plus cortisol resulted in hyperglycaemia (at 240 min, somatostatin plus adrenaline 11·4 ± 0·4 mmol l^-1, P < 0·001; somatostatin plus cortisol 6·7 ± 0·3 mmol l^-1, P < 0·05; somatostatin alone 4·9 ± 0·4 mmol l^-1). No synergistic effect on blood glucose was seen with adrenaline and cortisol together. When glucagon was added, blood glucose rose more rapidly than without glucagon (9·3 ± 0·4 mmol l^-1v. 7·2 ± 0·5 mmol l^-1 at 45 min, P < 0·001), but plateau values were similar. Plasma NEFA levels were raised by somatostatin plus adrenaline (0·55 ± 0·04–1·82 ± 0·11 mmol l^-1 at 60 min). Somatostatin plus cortisol had no more effect on plasma NEFA than somatostatin alone. During the combined infusion of somatostatin plus adrenaline plus cortisol, a synergistic effect on plasma NEFA was observed (2·30 ± 0·11 mmol l^-1 at 60 min, P < 0·01 v. somatostatin plus adrenaline). This occurred despite a small escape of insulin secretion. The lipolytic actions of adrenaline are potentiated by elevated circulating cortisol levels in insulin-deficient man. Glucagon does not modify this response, but accelerates the development of hyperglycaemia.     

The direct measurement of plasma colloid osmotic pressure is superior to colloid osmotic pressure derived from albumin or total protein

Plasma colloid osmotic pressure (COP) has been calculated from both serum albumin concentration and plasma total protein concentration. These values have been compared to those measured directly using a membrane-transducer oncometer in a group of normal subjects, in a group of critically-ill patients with a variety of primary diagnoses and in a group of hypovolaemic patients before and after plasma volume replacement with 6% hydroxyethyl starch solution. In the normal samples, COP calculated from albumin (COP_alb) underestimated the measured COP (COP_m) by mean of 2.0 mmHg (p(0.002), with correlation coefficient r=0.39 (n/s). Similarly, the COP_alb underestimated COP_m by a mean of 5.7 mmHg (p(0.001) in the critically ill patient group; r=0.38 (p(0.02). Furthermore, in the patients receiving plasma volume replacement serum albumin concentration fell by 13.1% (p(0.001) whilst COP_m increased by 11.5% (p(0.002). In the normal subjects COP calculated from total protein concentration (COP_tp) underestimated the COP_m by 1.5 mmHg (p(0.02) with r=0.65 (p(0.01). Conversely, in the patient samples, mean COP_tp overestimated COP_m by 3.5 mmHg (p(0.001) with r=0.73 (p(0.002). We conclude that COP_alb is an inadequate estimate of COP_m particularly in patients where its use may have important clinical consequences. COP_tp provides a reasonable estimate of COP_m in normal subjects but in patients samples, where albumin: globulin ratio is low COP_tp overestimates substantially in many cases. We advocate the direct measurement of COP in critically-ill patients.     

Intensity of Nordic Walking in young females with different peak O2 consumption

The purpose of this cross‐sectional study was to determine the physiological reaction to the different intensity Nordic Walking exercise in young females with different aerobic capacity values. Twenty‐eight 19–24‐year‐old female university students participated in the study. Their peak O₂ consumption (VO₂ peak kg^?1) and individual ventilatory threshold (IVT) were measured using a continuous incremental protocol until volitional exhaustion on treadmill. The subjects were analysed as a whole group (n = 28) and were also divided into three groups based on the measured VO₂ peak kg^?1 (Difference between groups is 1 SD) as follows: 1. >46 ml min^?1 kg^?1 (n = 8), 2. 41–46 ml min^?1 kg^?1 (n = 12) and 3. <41 ml min^?1 kg^?1 (n = 8). The second test consisted of four times 1 km Nordic Walking with increasing speed on the 200 m indoor track, performed as a continuous study (Step 1 – slow walking, Step 2 – usual speed walking, Step 3 – faster speed walking and Step 4 – maximal speed walking). During the walking test expired gas was sampled breath‐by‐breath and heart rate (HR) was recorded continuously. Ratings of perceived exertion (RPE) were asked using the Borg RPE scale separately for every 1 km of the walking test. No significant differences emerged between groups in HR of IVT (172·4 ± 10·3–176·4 ± 4·9 beats min^?1) or maximal HR (190·1 ± 7·3–191·6 ± 7·8 beats min^?1) during the treadmill test. During maximal speed walking the speed (7·4 ± 0·4–7·5 ± 0·6 km h^?1) and O₂ consumption (30·4 ± 3·9–34·0 ± 4·5 ml min^?1 kg^?1) were relatively similar between groups (P > 0·05). However, during maximal speed walking, the O₂ consumption in the second and third groups was similar with the IVT (94·9 ± 17·5% and 99·4 ± 15·5%, respectively) but in the first group it was only 75·5 ± 8·0% from IVT. Mean HR during the maximal speed walking was in the first group 151·6 ± 12·5 beats min^?1, in the second (169·7 ± 10·3 beats min^?1) and the third (173·1 ± 15·8 beats min^?1) groups it was comparable with the calculated IVT level. The Borg RPE was very low in every group (11·9 ± 2·0–14·4 ± 2·3) and the relationship with VO₂and HR was not significant during maximal speed Nordic Walking. In summary, the present study indicated that walking is an acceptable exercise for young females independent of their initial VO₂ peak level. However, females with low initial VO₂ peak can be recommended to exercise with the subjective ‘faster speed walking’. In contrast, females with high initial VO₂ peak should exercise with maximal speed.     

Dose-dependent effects of almitrine on hemodynamics and gas exchange in an animal model of acute lung injury

Objective: To determine the dose-response relationship of almitrine (Alm) on pulmonary gas exchange and hemodynamics in an animal model of acute lung injury (ALI).¶Design: Prospective, randomized, controlled study.¶Methods: Twenty anesthetized, tracheotomized and mechanically ventilated (FIO₂ 1.0) pigs underwent induction of ALI by repeated saline washout of surfactant. Animals were randomly assigned to either receive cumulating doses of Alm intravenously (0.5, 1.0, 2.0, 4.0, 8.0 and 16.0 μg · kg^–1· min^–1) for 30 min each (treatment; n = 10) or to receive the solvent malic acid (controls; n = 10).¶Measurements and results: Measurements of pulmonary gas exchange and hemodynamics were performed at the end of each infusion period. Alm < 4.0 μg · kg^–1· min^–1 improved arterial oxygen pressure (PaO₂) (105 ± 9 mmHg for Alm 1.0 vs 59 ± 5 mmHg) and decreased intrapulmonary shunt (Q_s/Q_t) (32 ± 4 % for Alm 1.0 vs 46 ± 4 %) (P < 0.05). Alm ≥ 8.0 μg · kg^–1· min^–1 did not improve pulmonary gas exchange compared to controls. When compared to low doses of Alm < 4.0 μg · kg^–1· min^–1, high doses ≥ 8.0 μg · kg¹· min^–1 decreased PaO₂ (58 ± 11 mmHg for Alm 16.0) and increased Q_s/Q_t (67 ± 10 % for Alm 16.0) (P < 0.05).¶Conclusions: In experimental ALI, effects of almitrine on oxygenation are dose-dependent. Almitrine is most effective when used at low doses known to mimic hypoxic pulmonary vasoconstriction.     

Day-to-day variation in oxygen consumption and energy expenditure during submaximal treadmill walking in female adolescents

The day-to-day variation in oxygen consumption (V˙O ₂) and energy expenditure (EE) during horizontal treadmill walking was measured using indirect calorimetry in 20 female adolescents (mean age 17·3 years). Two different walking speeds were used: 5 km h^?1 and an individually convenient speed of 3·0 km h^?1 (mean). The two sets of measurements were performed on 2 consecutive days, and great care was taken to minimize possible disturbing factors. The mean V˙O ₂ was 919 ml min^?1 at 5 km h^?1 and 622 ml min^?1 at the individual speed, and the mean values of EE were 4·5 kcal min^?1 and 3·1 kcal min^?1 respectively. The individual day-to-day variation in V˙O ₂ (at 5 km h^?1) was between ?11·7% and +12·6% of the mean V˙O ₂. The coefficient of variation (CV) was 6·4% when values were calculated in ml min^?1 kg^?1. The energy expenditure varied somewhat less between the 2 days (CV = 5·7%). The corresponding value for EE when walking at the individual speed was 7·2%, and the mean day-to day variation in V˙O ₂ was 7·5% (CV). The rate of perceived exertion according to Borg's scale was lower on day 2 (11·9) compared with day 1 (13·0) when walking at 5 km h^?1. There was no difference in heart rate between the 2 days. It is concluded that EE varies somewhat less than V˙O ₂ on successive days, probably because of an interchangeable relationship between breathing gases, depending on which substrate is used for combustion. When using V˙O ₂ and EE for evaluation of physical capacity, the day-to-day variation in the measurements must be taken into consideration.     

Treatment of severe neutropenic sepsis with granulocyte transfusion in the current era – experience from an adult haematology unit in Singapore

Objectives: Granulocyte transfusion's (GT) efficacy among adult severe neutropenic sepsis (SNS) patients remains uncertain. We assessed GT's efficacy and its determinants among SNS patients in an adult haematology unit. The feasibility and safety of granulocyte donation (GD) and determinants of granulocyte yield were also evaluated. Methods: Retrospective analysis of granulocyte donors and recipients from March 2008 to October 2009. Results: Donors: Sixty GDs with a median WBC yield (WBCY) of 65·49 (31·30–131·72) × 10⁹ were collected from 48 donors (9 repeat donors) using hydroxyethyl starch and intermittent flow centrifugation aphaeresis after receiving 8 mg dexamethasone and 300 mcg granulocyte colony‐stimulating factor, with no serious adverse reactions (SAR). Six donations were urgently collected <3 h after pre‐medication, the median WBCY of which was not significantly different from donations collected >12 h after pre‐medication [59·18 (45·68–62·90) × 10⁹ vs 67·45 (31·30–131·72) × 10⁹, P = 0·140]. Only pre‐GD absolute neutrophil count (ANC) correlated with WBCY. Patients: Fifteen patients (12 acute leukaemias, 1 severe AA, 1 myelodysplastic syndrome and 1 lymphoma) received median 3 (2–9) ABO/RhD‐matched GTs over 2–24 (median 7) days at 3–61 (median 28) days from severe neutropenia (SN) onset without SAR. They received intensive chemotherapies (N = 9), allogeneic transplant (N = 3), autologous stem cell rescue (N = 1) or immunosuppressants (N = 2). Fourteen had bacterial (N = 1) infections, fungal (N = 3) infections or both (N = 10) and one had severe viral pneumonitis; 63·6 and 30·8% of bacterial and fungal infections responded, respectively. Median ANC increase (ANC_increase) was 1·26 (0–9·25) × 10⁹ at 5–20 (median 11) h post‐GT. On multivariate analysis, each patient's median ANC_increase only significantly correlated positively with median WBC dose/kg (P = 0·013). Five (33·3%) patients survived to discharge; the rest had infection‐related mortality (IRM). IRM was significantly associated with inotropic requirement (P = 0·004), ventilatory requirement (P = 0·017) and persistent SN (P = 0·007). Conclusion: GD is safe and feasible with good WBCY obtainable using our protocol. The effect of shortening pre‐medication interval on WBCY which may prevent delay in initiating GT is worth evaluating. GT most likely benefits SNS patients with prospects of neutrophil recovery before haemodynamic deterioration. Large randomised trials investigating the role and timing of GT among such patients are required.     

Alfentanil infusions on the intensive therapy unit

We have investigated the use of alfentanil by infusion to sedate 14 patients during controlled ventilation on the intensive therapy unit (ITU). An initial rate of 24 μg·kg^-1·h^-1 was chosen and altered there-after according to patient response. Incremental doses of midazolam (2.5–5.0 mg) were given intravenously (i.v.) if indicated. In 4 patients, the use of a muscle relaxant was necessary to allow adequate controlled ventilation of the patient. The mean duration of infusion was 27.9 h (range 10–141 h), and the mean total dose of alfentanil was 69.3 mg (12.5–240 mg). Spontaneous ventilation was rapidly achieved in 11 patients after stopping the infusion. The mean arterial carbon dioxide tension (PaCO₂) was 5.38 kPa, 15–30 min after stopping the infusion. The clinical condition of 2 patients necessitated a change in sedation technique and one patient died during the alfentanil infusion. Alfentanil by infusion caused no major cardiovascular effects and did not influence the plasma cortisol response to trauma. There was no major alteration in blood biochemistry or haematology during the infusions of alfentanil. The plasma concentrations of alfentanil during infusion showed a wide variability. These probably relate to both changes in the volume of distribution of the drug and in hepatic clearance.     

Transcapillary escape rate of albumin in juvenile hypertension

Summary. The transcapillary escape rate of albumin was studied in 24 juvenile hypertensives and in 13 controls on the basis of the radioactivities determined in the blood during 60 min after i.v. injection of human ¹³¹I–labelled albumin. In addition, the central haemodynamics of all hypertensive subjects was examined at rest and during exercise. The patients were grouped according to their pressure during the investigation at rest. The group whose mean arterial pressure did not exceed 100 mmHg, thus being within the range of normotension, did not exhibit a significant deviation from controls. The group with mean arterial pressure exceeding this limit (corresponding to the range of borderline hypertension) showed a significantly higher escape rate of albumin (9.3 ± 50%/h) than controls (5.2 ± 1.6%/h). The albumin escape rate was significantly correlated to the mean pulmonary artery pressure during exercise but not to the remaining central haemodynamic parameters at rest or during exercise. No difference was seen in the magnitude of plasma volumes of juvenile hypertensives and controls. The findings suggest that secondary changes of capillary functions are present already in the early stages of hypertension.     

Biopharmaceutical Characterization of Nebulized Antimicrobial Agents in Rats: 2. Colistin

The purpose of this study was to investigate the pharmacokinetic properties of colistin following intrapulmonary administration of colistin sulfate in rats. Colistin was infused or delivered in nebulized form at a dose of 0.35 mg/kg of body weight in rats, and plasma drug concentrations were measured for 4 h after administration. Bronchoalveolar lavages (BAL) were also conducted at 0.5, 2, and 4 h after intravenous (i.v.) administration and administration via nebulized drug to estimate epithelial lining fluid (ELF) drug concentrations. Unbound colistin plasma concentrations at distribution equilibrium (2 h postdosing) were almost identical after i.v. infusion and nebulized drug inhalation. ELF drug concentrations were undetectable in BAL samples after i.v. administration, but they were about 1,800 times higher than unbound plasma drug levels at 2 h and 4 h after administration of the nebulized drug. Simultaneous pharmacokinetic modeling of plasma and ELF drug concentrations was performed with a model characterized by a fixed physiological volume of ELF (V_ELF), a passive diffusion clearance (Q_ELF) between plasma and ELF, and a nonlinear influx transfer from ELF to the central compartment, which was assessed by reducing the nebulized dose of colistin by 10-fold (0.035 mg kg⁻¹). The k_m was estimated to be 133 μg ml⁻¹, and the V_{max, in}-to-K_m ratio was equal to 2.5 × 10⁻³ liter h⁻¹ kg⁻¹, which was 37 times higher than the Q_ELF (6.7 × 10⁻⁵ liter h⁻¹ kg⁻¹). This study showed that with the higher ELF drug concentrations after administration via nebulized aerosol than after intravenous administration, for antibiotics with low permeability such as colistin, nebulization offers a real potential over intravenous administration for the treatment of pulmonary infections.     

Pharmacodynamic comparison of two formulations of Acarbose 100-mg tablets

What is known and Objective: Acarbose, an α‐glycosidase inhibitor, is used to treat diabetic patients. Pharmacokinetic evaluation of acarbose is difficult because <2% is absorbed systemically. The current investigation evaluated the bioequivalence of two formulations of acarbose through pharmacodynamic comparison. Methods: This investigation consisted of a pilot study and a main study. The pilot study had an open, single‐dose, single‐sequence design. Subjects received placebo and then two tablets of reference formulation (Glucobay^® 100 mg tablet; Bayer Healthcare) on two consecutive days with sucrose. The main study was an open, randomized, two‐period, two‐sequence crossover study. Subjects randomly received placebo and two tablets of either test formulation (generic acarbose 100‐mg tablet) or reference formulation with sucrose on two consecutive days in the first period. In the second period, placebo and alternative formulation were administered. Serial blood samples for pharmacodynamic assessment were taken after each administration. The maximum serum glucose concentration (G_max) and the area under the serum glucose concentration–time profile (AUC_gluc) were determined and compared. Results and Discussion: Five subjects completed the pilot study. The AUC_gluc from dosing until 1 h post‐dose (AUC_{gluc,1 h}) was significantly different between the placebo and acarbose. A total of 33 subjects completed the main study. The mean differences in G_max (ΔG_max) and AUC_{gluc,1 h} (ΔAUC_{gluc,1 h}) for the reference formulation compared with placebo were 22·0 ± 18·3 mg/dL and 928·2 ± 756·0 mg min/dL, respectively. The corresponding values for the test formulation were 23·3 ± 21·2 mg/dL and 923·0 ± 991·4 0 mg min/dL, respectively. The geometric mean ratios (GMRs) of the test formulation to the reference formulation for ΔG_max and ΔAUC_{gluc,1 h} were 1·06 and 1·00, respectively, and the 90% confidence intervals (CIs) corresponding values were 0·79–1·39 and 0·64–1·36, respectively. What is new and Conclusion: The 90% CIs of GMRs for the pharmacodynamic parameters chosen for bioequivalence evaluation of two formulations of acarbose did not meet the commonly accepted regulatory criteria for bioequivalence (0·80–1·25).     

Transport of vitamin D sterols in human plasma: effect of excess vitamin D, 25 hydroxyvitamin D and 1,25 dihydroxyvitamin D

Abstract. Vitamin D and its more active metabolites, 25 hydroxyvitamin D (25-OH-D) and 1,25-dihydroxy-vitamin D (1,25-(OH)₂-D), are transported in human plasma on a specific binding protein (DBP), which has been shown to have an α-globulin electrophoretic mobility. Since the concentration of DBP in normal human plasma is approximately 5 μmol/l, whereas that of all the vitamin D metabolites is less than 0·2 μmol/l, DBP is less than 3% saturated under physiological conditions. We have studied the transport of the above-mentioned metabolites in human plasma in vitro at normal and saturating concentrations. Human plasma was incubated with increasing amounts of vitamin D metabolites together with their radiolabelled tracers. Ultracentrifugation was used to isolate plasma lipoproteins (density, d < 1·21 g/ml) and agarose gel electrophoresis of lipoprotein-free plasma (d > 1·21 g/ml) to separate DBP (α globulin) from albumin. The recovery of the tracer in plasma proteins was always more than 80%. At physiological concentrations [³H]25-OH-D bound almost exclusively to DBP (98%), [³H]vitamin D or [¹⁴C]vitamin D bound both to DBP and to lipoproteins (40%), and [³H]1,25-(OH)₂-D bound to DBP (62%), to lipoproteins (15%) and also to albumin (23%). When the concentration of vitamin D metabolites was increased, DBP became saturated. The binding capacity of DBP was similar for all three sterols, about 5 μmol/l plasma, or one mole of sterol per mole of protein, but the saturating concentration was different for the three sterols (vitamin D > 1,25-(OH)₂-D > 25-OH-D). 25-OH-D had the greatest affinity for DBP, and it completely displaced both vitamin D and 1,25(OH)₂-D from DBP at higher concentrations. All sterols bound to both plasma lipoproteins and albumin: vitamin D preferentially to lipoproteins and both 25-OH-D and 1,25-(OH)₂-D to albumin. A similar binding pattern for vitamin D in plasma was observed previously by us in a child with vitamin D toxicity. The increased binding of vitamin D to lipoproteins and especially to albumin may help explain the pathogenesis of toxicity in hypervitaminosis D, where the plasma levels of the more active metabolites are insufficient to account for the clinical signs.