Effect of posture on the plasma cholesterol level

Effects of Rest Position on Morphology of the Vastus Lateralis and Its Relationship with Lower-Body Strength and Power

Ultrasonography of the lower body typically encompasses supine rest due to fluid shifts affecting tissue size and composition. However, vastus lateralis (VL) examination is completed in the lateral recumbent position, and this positional change may influence morphology and its ability to predict function. This study aimed to examine the effect of position on VL morphology and its relationship with lower-body performance. Cross-sectional area (CSA), muscle thickness (MT), pennation angle (PA), echo intensity (UnCorEI), subcutaneous adipose tissue thickness (SFT), and echo intensity corrected for SFT (CorEI) were assessed in 31 resistance-trained males (23.0 ± 2.1 yrs; 1.79 ± 0.08 m; 87.4 ± 11.7 kg) immediately after transitioning from standing to supine (IP), after 15 min of standing (ST), and after 15 min of rest in three recumbent positions: supine (SUP), dominant lateral recumbent (DLR), non-dominant lateral recumbent (NDLR). Participants also completed unilateral vertical jumps, isometric/isokinetic tests, and a one-repetition maximum leg press. CSA, MT, PA, and SFT were greater in ST compared to NDLR, DLR, and SUP (p < 0.05). CSA, UnCorEI, and CorEI were different between recumbent positions; however no differences were observed for MT, PA, and SFT. Different magnitudes of relationships were observed between muscle morphological characteristics measured after rest in different positions and performance variables. Muscle morphology in IP generally appears to be the best predictor of performance for most variables, although utilizing the NDLR and DLR positions may provide comparable results, whereas morphology measured in ST and SUP provide weaker relationships with physical performance. IP also requires less time and fewer requirements on the technician and subject, thus researchers should consider this positioning for VL examination.

Acutely developing, spurious anaemia without actual blood loss. A paradigmatic case report

We describe the case of a 55-year old women admitted at night to the emergency department (ED), complaining for acute abdominal pain lasting for nearly 5 hours. A first blood testing, performed immediately after admission, revealed mild anaemia. A second blood sample, drawn two hours after admission, revealed a considerable decrease of haemoglobin, haematocrit, total white blood cell and platelet counts (between 10-15% reduction). Abdominal ultrasonography was normal and the patient had no signs or symptoms of internal or external haemorrhage. Pre-analytical and analytical errors were accurately excluded. No infusion therapy was administered. After thoughtful discussing the sequence of events, it was ascertained that the first set of blood samples was drawn with the patient in seated position, immediately after ED admission (i.e., approximately 1 min passed from standing to seated position before venipuncture), whereas the second set of blood samples was drawn with the patient lying for two hours in supine position. This case report highlights the importance of standardizing patient position before venous blood collection, along with the crucial role played by cooperation and communication between laboratory and clinical wards for identifying and troubleshooting potential causes of spurious results of in vitro diagnostic testing.

Time required for resetting postural effects on serum constituents in healthy individuals

OBJECTIVE

We investigated postural effects on concentrations of commonly measured serum analytes and sought for optimal duration of sitting before venipuncture in an outpatient setting.

METHODS

Seven healthy volunteers changed posture serially at 30-minute (min) intervals from lying, sitting, slowly walking, sitting, and to lying again. At the end of the first lying posture, wing-needle was inserted into cubital vein and 3mL of blood was drawn every 5min. All the serum was stored at -80°C until the time of collective measurements for 16 major chemistry analytes two weeks later.

RESULTS

Concentrations of macromolecular analytes (albumin, total cholesterol, alkaline phosphatase, etc.) in supine position were increased (on average 5-7%) after 30min of sitting and further increased (10-14%) during 30min of walking. After slow walking, time required for return of values to the levels of sitting posture took approximately 20min. Concentrations of small molecules (sodium, urea, etc.) did not show any variation by the postural changes. Potassium and inorganic phosphate showed walking-related increase in concentrations. Creatinine was lowered in sitting posture, which implicates postural changes in renal flow.

CONCLUSION

It is generally recommended to sit for 20min or more before venipuncture, although the effect of prior physical movement remains a little longer for potassium and inorganic phosphate.

Postural change during venous blood collection is a major source of bias in clinical chemistry testing

BACKGROUND

To investigate the influence of different phlebotomy postures on clinical chemistry testing.

MATERIALS AND METHODS

Nineteen volunteers were recruited from the laboratory staff. A first set of samples was drawn after 25 min of resting in supine position, a second after 20 min in sitting position, and a third after 20 min in upright position. Clinical chemistry testing was performed on Roche Cobas C501.

RESULTS

The plasma volume change (PVC) was -3.4% from supine to sitting, -14.1% from supine to standing and -9.7% from sitting to standing. Compared to quality specifications for bias, hemoglobin, hematocrit, albumin and total proteins exhibited meaningful increases from supine to sitting, whereas meaningful increases were observed for hemoglobin, hematocrit, albumin, alkaline phosphatase (ALP), amylase, aspartate aminotransferase (AST), total bilirubin, calcium, total and high-density lipoprotein (HDL) cholesterol, gamma-glutamyl transferase (GGT), glucose, lactate dehydrogenase (LDH), magnesium, total protein and triglycerides from sitting to standing. The parameters with meaningful bias from sitting to upright were hemoglobin, hematocrit, albumin, ALP, total bilirubin, calcium, total and HDL cholesterol, glucose, LDH and total protein.

CONCLUSIONS

These results provide further support to the need of standardizing patient's posture during phlebotomy.

Acute psychological stress and epinephrine infusion in normolipidemic and hyperlipidemic men: effects on plasma lipid and apoprotein concentrations

This study examined whether psychological stress and the infusion of epinephrine increase plasma lipid and apoprotein concentrations in normolipidemic and hyperlipidemic men. Subjects were studied during three separate 6-hour laboratory sessions: a control session, during which subjects rested quietly while blood samples and hemodynamic measurements were obtained; a stress session, during which subjects were presented with two challenging mental tasks, followed by quiet rest; and an epinephrine infusion session, during which subjects received a low-dose infusion of epinephrine followed by quiet rest. The stress and epinephrine infusion manipulations produced the expected changes in plasma epinephrine and norepinephrine levels, blood pressure, and heart rate. Free fatty acid concentration increased markedly during epinephrine infusion and less dramatically but consistently during mental stress. Both stress and epinephrine infusion produced acute increases in plasma total, low-density lipoprotein, very low-density lipoprotein, and high-density lipoprotein cholesterol and apoprotein B concentrations, but comparable increases during the control session were not observed. Changes in albumin concentration (an index of plasma volume) were associated with changes in lipid concentrations during psychological stress. Epinephrine increases during psychological stress were correlated with increases in free fatty acid and triglyceride levels both during and after task administration. It was concluded that psychological or pharmacological stress induced in the laboratory produces changes in lipid concentrations, which at least during psychological stress, may be attributed to concomitant changes in plasma volume. The association between task-induced changes in epinephrine and changes in free fatty acid and triglyceride levels, also supports the hypothesis that psychological stress increases lipolysis.

Accurate measurement of serum total cholesterol: the need for standardization

Heightened awareness of the importance of cholesterol and heart disease has increased cholesterol testing in the United States. The demand for reliable cholesterol measurements has become a focal concern of the patient as well as the clinician. This paper covers the major analytical and preanalytical issues and factors that can affect the reliability of cholesterol results. We discuss factors that lead to impression and inaccuracy; solutions for some of the major problems; resources and techniques to help standardize cholesterol measurement; and preanalytical issues that can affect cholesterol results--i.e., patient preparation; collection, processing, storage and proper analysis of the specimen; biological and seasonal variations; age and gender; diet; alcohol consumption; weight changes; exercise; primary diseases; and infections and trauma. Many of these can be controlled by the physician, resulting in more reliable cholesterol readings under stable metabolic conditions. Accurate values will help to classify the patient's coronary heart disease risk, define appropriate treatment strategies, and simplify monitoring of dietary and/or drug intervention.

Rising cholesterol levels in children with familial hypercholesterolaemia

Reference ranges (5th to 95th percentile) for fasting total serum cholesterol concentration were calculated for 571 unrelated children aged 4-19 years, without known predisposition to hypercholesterolaemia. Values were 3.31-5.81 mmol.l-1 for boys and 3.20-5.66 mmol.l-1 for girls, without significant differences between sexes at any age, compared to our laboratory reference ranges for men (3.46-6.87 mmol.l-1) and women (3.00-6.38 mmol.l-1). A further 85 children, each with a first degree relative with Familial Hypercholesterolaemia (FH), were studied. Initially, 39 had high cholesterol concentrations suggestive of FH. Repeated serial measurements were carried out in 18 of the 46 apparently unaffected children. Seven of these showed marked increases in serum cholesterol over 1-7 years, reaching concentrations above the 95th centiles of the appropriate reference ranges. The annual rate of increase was significantly higher than in the 11 who remained normocholesterolaemic. In 3 of these 7 children, diagnosis of FH was confirmed retrospectively, using recombinant DNA technology to show that each had inherited the defective allele of the LDL-receptor gene from an affected parent. Thus, serial cholesterol measurements may be needed to confirm or exclude FH in potential heterozygotes, while DNA studies can be used for definitive diagnosis in some families.

Oral contraceptives and coronary heart disease: modulation of glucose tolerance and plasma lipid risk factors by progestins

Widespread use of oral contraceptive formulations by women throughout their reproductive life has given rise to concerns about the effects of oral contraceptives on risk factors for coronary heart disease. Oral contraceptive-induced changes in both carbohydrate and lipoprotein risk factors may contribute to an increased risk of coronary heart disease. Carbohydrate and lipoprotein risk factors for coronary heart disease are reviewed, and oral contraceptive-induced changes in carbohydrate and lipoprotein metabolism, which may lead to altered risk status for coronary heart disease, are discussed. The importance of methodology in evaluating the results of studies assessing such oral contraceptive-induced changes is stressed. The role of progestins in influencing coronary heart disease risk factors is surveyed, and differences among progestins commonly used in oral contraceptive formulations are discussed. In addition, the effect of various combination oral contraceptives on risk factor status is outlined. Finally, the implications of available evidence for the selection of progestins for oral contraceptive formulations of the future are discussed. Current data indicate that medium- and low-fixed-dose oral contraceptive formulations containing estrogen/norethindrone acetate have less metabolic impact than do comparable levonorgestrel-containing formulations, including multiphasic formulations. Triphasic formulations may have less effect on coronary heart disease risk factors, although data are not yet conclusive. Novel progestins such as desogestrel may also have lesser effects on metabolic functions, but the reduced androgenicity of such compounds may expose women to an increased risk of estrogen-induced hypertriglyceridemia.

Paradoxical effects of the anti-androgen cyproterone acetate on lipid and lipoprotein metabolism

The effects on fasting serum lipids of the potent anti-androgen, cyproterone acetate (CA) and the oestrogen, ethinyl oestradiol (EO) given both alone and in combination were examined in women acting as their own controls. Cyproterone acetate alone caused significant reductions in total cholesterol, high density lipoprotein subfraction 2 cholesterol (HDL2) and low density lipoprotein cholesterol (LDL). Ethinyl oestradiol alone significantly increased triglycerides, HDL and HDL2 and reduced LDL, and there was also a significant increase in the HDL/LDL and HDL2/LDL ratios. The two steroids were administered in combination according to a reverse sequential regime. The 28-day treatment cycle thus included Phase A during which both drugs were given followed by Phase B when EO alone was given. Triglycerides rose significantly in Phases A and B to the same extent as for the group taking EO alone. High density lipoprotein cholesterol was unchanged but HDL2 was reduced in both phases and this effect could not be overcome by increasing the dose of oestrogen. Low density lipoprotein cholesterol fell and the HDL/LDL ratio rose during the two Phases and these changes were significant during Phase A. The effects of EO demonstrated in this study are consistent with previous reports. Cyproterone acetate, however, has properties conventionally ascribed to both synthetic androgens (e.g. lowering of HDL2) and oestrogens (e.g. lowering of LDL). The limitations of the terms androgenic and oestrogenic activity in relation to their conventional associations with changes in lipid and lipoprotein levels are discussed.

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.

Swelling of the foot, its vascular volume and systemic hemoconcentration during long-term constrained sitting

Swelling of the left foot and changes in its vascular volume (VV) were studied in seven healthy subjects during 8 h of seated work without leg movements. Changes in total plasma volume (PV) were calculated from hematocrit values. Reference values (r.v.) were obtained during a working day requiring intermittent physical activity (walking). Significant changes during the first 4 h: the foot swelled by 3.5% (r.v.: 2.2%) and VV was reduced by 0.5% of the foot volume (r.v.: increased by 0.3%). Accordingly, the interstitial fluid volume (IFV) of the foot increased by 4.0% (r.v.: 1.9%). The loss of PV was 6.3%. During the last 4 h the only significant change was an increase in foot volume by 1.9%. It is concluded that (1) foot swelling should be corrected for changes in VV to obtain an exact measure of the change in IFV, (2) prolonged elevated pressure, assumed to occur in the feet during relaxed sitting, does not imply distension ("delayed compliance") of the vascular system as previously suggested, (3) hemoconcentration seems to reach complete stability during the initial period of quiet sitting, (4) loss of PV during sedentary work may be avoided by a modest increase in leg activity.

The effect of progestins in combined oral contraceptives on serum lipids with special reference to high-density lipoproteins

Fasting serum lipids were measured in a group of 293 women desirous of using oral contraceptives (OCs) and 536 women who had been taking five varieties of OCS for many months before being tested. Parameters studied were serum cholesterol, triglyceride, high-density lipoprotein (HDL), the two main subfractions of HDL, namely, HDL2 and HDL3, and the ratio of HDL2 cholesterol to low-density lipoprotein (LDL) cholesterol. Studies of these five groups of women enabled us to compare the effect of varying amounts of levonorgestrel with norethindrone and to study the effects of estrogen combined with these progestins. The levonorgestrel-containing pills and the progestin-only OC significantly depressed HDL2 cholesterol levels and the ratio of HDL2 to LDL cholesterol.

Effects of two types of dietary fibre on faecal steroid and lipid excretion

Fibre supplements from wheat bran and sugar cane residue (bagasse) were added to the normal diet of volunteers for 12-week periods in a controlled metabolic study. Stool weights and stool fat excretion increased on both dietary fibres. Bagasse increased the daily loss of acid steroids, but bran failed to affect bile acid excretion. Decreased transit time without alteration in faecal flora occurred with bagasse. The raised excretion of bile acids and fatty acids failed to lower the plasma cholesterol and triglycerides after 12 weeks. Thus different fibre sources with variable components have dissimilar metabolic effects.

Effects of two types of dietary fibre on faecal steroid and lipid excretion

Fibre supplements from wheat bran and sugar cane residue (bagasse) were added to the normal diet of volunteers for 12-week periods in a controlled metabolic study. Stool weights and stool fat excretion increased on both dietary fibres. Bagasse increased the daily loss of acid steroids, but bran failed to affect bile acid excretion. Decreased transit time without alteration in faecal flora occurred with bagasse. The raised excretion of bile acids and fatty acids failed to lower the plasma cholesterol and triglycerides after 12 weeks. Thus different fibre sources with variable components have dissimilar metabolic effects.