Left ventricle haemodynamics and vaso-active hormones during graded supine exercise in healthy male subjects

Left ventricle systolic and diastolic functional parameters were measured by gated equilibrium radionuclide cardiography in 12 healthy men (age 33–51 years) at rest and during graded supine exercise. The leftventricle end-diastolic volume showed an initial small (11%) increase during low submaximal exercise [from mean 163 (SD 40) at rest to mean 181 (SD 48) ml], while left ventricle end-systolic volume decreased successively [from mean 59 (SD 19) to mean 39 (SD 21) ml] with increasing exercise. Stroke volume was therefore elevated at all exercise levels compared with rest [mean 104 (SD 23) ml], and the peak value [mean 128 (SD 33) ml] was found at the lowest exercise level, contributing 40% to the initial increase in cardiac output. Cardiac output increased from mean 6.2 (SD 1.4) at rest to mean 20.2 (SD 5.0) 1 · min^–1 at maximum. Left ventricle peak ejection and peak filling rates increased from mean 449 (SD 89) and mean 442 (SD 85) ml · s^–1 at rest to mean 996 (SD 227) and mean 1255 (SD 333) ml · s^–1, respectively, at maximum. The myocardium oxygen consumption, assumed to be proportional to the sum of the stroke work and the potential energy, increased fourfold, but absolute values were twice as high as expected, indicating that extrapolation from data obtained in dog hearts (as we have done) cannot be directly applied to humans. Selected vaso-active hormones were measured at all exercise intensities. Noradrenaline (NA), adrenaline (A) and angiotensin II (AII) concentrations showed a very pronounced increase at maximal exercise compared with the preceding lower intensites, while atrial natriuretic factor (ANF) and cyclic guanosinemonophosphate (cGMP) concentrations showed a more continuous increase, and dopamine (DA) remained almost unchanged. This speaks in favour of a crucial role for NA, A and AII in preserving blood pressure at maximum exercise, while DA probably has no importance for the cardiovascular homeostasis during exercise. Increases in concentrations of ANF and cGMP were highly correlated (r = 0.86). Our data supported the opinion that there is a cardiac limitation to maximal performance connected to the cardiac pumping capacity.     

Age-related changes of exercise-induced plasma catecholamines and neuropeptide Y responses in normal human subjects.

Age-related plasma noradrenaline and neuropeptide Y were evaluated in seven young (mean +/- SD, 28 +/- 3 years) and seven elderly (64 +/- 8 years) normal subjects during rest and different work loads on a cycle ergometer. In the supine and the sitting position plasma noradrenaline and neuropeptide Y were almost identical in the two groups. Plasma neuropeptide Y did not increase during exercise at 100 W for 15 min. At this load plasma noradrenaline levels were higher in the older subjects (mean +/- SEM, 0.97 +/- 0.12 vs. 0.60 +/- 0.09 ng ml-1). There was a significant correlation between plasma noradrenaline and the relative work load at 100 W (r = 0.794, P = 0.0007). At 75% of maximal work load plasma noradrenaline and neuropeptide Y were higher in the young group (1.84 +/- 0.16 vs. 1.26 +/- 0.13 ng ml-1 (noradrenaline) and 38 +/- 4 vs. 22 +/- 5 pmol l-1 (neuropeptide Y)). In the elderly group plasma neuropeptide Y did not increase during exercise and showed a tendency to fall below basal level 5 min post-exercise. It is concluded, that plasma noradrenaline does not increase more in older subjects during exercise when correcting for the generally lower physical fitness in this group compared to younger subjects, and that plasma neuropeptide Y does not increase during exercise in older subjects, suggesting an age-reduced capacity in this system.     

Menstrual patterns in Danish elite swimmers

Summary Questionnaires were given to 140 female elite swimmers from the highest ranking division in the Danish Swimming Association inquiring about their menstrual history. Eighty-nine percent completed the questionnaires. We found a very low incidence of menstrual dysfunction (16%) compared to other groups of endurance trained females. Hard physical endurance training did not seem to delay the onset of menarche among swimmers. Furthermore, no difference in adjusted body mass between a group with oligomenorrhoea and a normal menstruating group could be demonstrated. The study indicated that the influence of body mass or body fat content was a more important factor in menstrual function than the amount of training or psychological stress.     

First Clinical Experience with Intranasal Cooling for Hyperthermia in Brain-Injured Patients

Introduction

Hyperthermia is common in brain-injured patients and associated with a worse outcome. As brain rather than body temperature reduction, theoretically, is the most important in cerebral protection, there is logic in targeting cooling at the brain. Selective brain cooling can, in theory, be obtained by cooling the skull or by heat loss from the upper airways. In this preliminary safety and efficacy study, we report clinical data from brain-injured patients who because of hyperthermia were treated with intranasal cooling.

Methods

Nine intubated brain-injured patients with hyperthermia were treated using a prototype intranasal balloon system perfused with cold saline. Temperature in the cerebrum, esophagus, and bladder was monitored together with intracranial pressure.

Results

In only two of nine patients, normothermia was reached in the esophagus and in only four of nine patients it was reached in the bladder. When normothermia was reached, the time to normothermia was delayed. In the brain, normothermia was reached in two of five patients after approximately 72 h. Median temperature curves from the first 72 h of cooling showed that normothermia was not reached in any of the three compartments. The temperature in the brain and bladder were on average 0.6 and 0.5 °C higher than in the esophagus. ICP increased with increasing brain temperature. We found no signs of clinical important injury to the nasal mucosa from the cold saline or pressure in the balloons.

Conclusion

In brain-injured patients with hyperthermia, cooling with a prototype intranasal balloon system was clinically inadequate as the effect was delayed and not brain selective.     

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. Accepted: 31 October 1997     

Hyperparathyroidism and long-term bone loss after renal transplantation

BACKGROUND: While early bone loss after renal transplantation (RT) is well described, factors affecting the long-term fate of bone have received less attention. METHODS: Whole body (WB), lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) was measured using dual energy X-ray absorptionometry in 126 stable RT patients and repeated in 114 survivors after 3 yr. Percentage change per year (%/yr) was correlated to clinical and biochemical markers of bone metabolism. RESULTS: Low bone mass was a marker of increased mortality (FN < 80% normal 6.3%/yr; >80% 2.2%/yr). Percent change was WB -0.7 +/- 1.5 (p < 0.01); LS -0.3 +/- 2.6; FN -1.0 +/- 3.0 (p < 0.01) and, corrected for expected loss for age and sex: WB -0.5 (p < 0.01); LS 0.0; FN -0.8 (p < 0.05). Factors associated with increased loss rates were (LS%): short RT duration [<2 yr: -3.1 (p < 0.01)], high prednisone dose [>9 mg/d: -1.9 (p < 0.01)], high cyclosporine trough concentration [>175 ng/L: -1.9 (p < 0.05)], high hyperparathyroidism (PTH) [>150 ng/L: -1.5 (p < 0.05)], high alkaline phosphatase [>275 U/L: -1.6 (p < 0.05)], high osteocalcin [>75 microg/L: -1.6 (p < 0.05)]. Marginal detrimental effects of uremia, hypoalbuminemia and hyperphosphatemia were noted. Thiazide treatment seemed to protect against, and furosemide to exacerbate, bone loss, but this may have been related to associated uremia. Patients treated with vitamin D gained bone, while untreated patients with low initial 1,25-dihydroxyvitamin D lost bone [FN%-2.1 (p < 0.05)]. The prevalence of PTH (52%) and hypercalcemia (22%) remained unchanged. There was no effect of sex hormone levels, calcium and phosphate excretion, or serum calcium. CONCLUSION: While LS BMD stabilizes after RT, there is a continuing loss of WB and FN BMD. The major causes of bone loss are steroid therapy and continuing PTH, with no tendency towards spontaneous resolution. Increased vitamin D and calcium therapy should be considered for this patient group, and more aggressive therapy, e.g. parathyroidectomy given for patients with resistant PTH of >150 ng/L.     

Variability and reproducibility of hepatic FDG uptake measured as SUV as well as tissue‐to‐blood background ratio using positron emission tomography in healthy humans

Introduction: To investigate variability and reproducibility of hepatic [¹⁸F]‐2‐fluoro‐2‐deoxy‐d ‐glucose (FDG) uptake in healthy individuals. Methods:  Static images were obtained 70 min after the injection of 160 MBq FDG in six healthy subjects at two occasions with 13 days’ interval. FDG uptake was adjusted for tissue‐to‐blood background ratio (T/B), or measured as standardized uptake value (SUV). Small regions of interest (ROIs) of 10 cm³ in two different hepatic regions were analysed as well as the total liver. Results: Mean SUV was 1·16 ± 0·15 and mean T/B corrected values was 1·87 ± 0·17. The maximal values were 2·70 (SUV) and 4·67 (T/B). Reproducibility was 6·7% for the mean SUV and 0·2% for the max SUV values. The corresponding figures for the T/B corrected mean values were 6·4% and for the max T/B values 13·0%. In general, the small ROIs had a comparable or even lower CV% for SUV values, but a higher CV% for T/B corrected values. Conclusions: In normal subjects hepatic FDG‐uptake is high and homogeneous with a low CV% between days. T/B corrected values are largely comparable to SUV values but not superior, probably due to the standardization of procedures and homogeneity of the subjects. The T/B corrected method is theoretically superior in a more inhomogeneous population or when using different scanners and is shown here to be easy to apply. Small ROIs of 10 cm³ are representative with respect to mean FDG uptake in the total liver and reproducibility, but do not identify the max FDG uptake.     

Atrial natriuretic factor: comparability of venous and arterial plasma measurements in man at rest and during exercise

1. Simultaneously obtained arterial and venous plasma atrial natriuretic factor (ANF) concentrations were compared at supine rest and during graded dynamic leg exercise in 10 healthy male subjects (aged 33-51 years). 2. Arterial ANF concentrations ranged between 12 and 179 pg/ml and venous concentrations between 9 and 177 pg/ml. 3. A positive correlation between arterial and venous concentrations was found (r = 0.984). 4. Arterial ANF concentrations were higher than venous concentrations in all pairs of samples (n = 31), but the difference was small and changed little with exercise: the mean difference was 5 pg/ml at rest, 12 pg/ml during submaximal exercise and 6 pg/ml during maximal exercise. 5. The extraction ratios for ANF varied greatly, but were in general lower (P less than 0.05) during maximal exercise (median 0.07, range 0.01-0.32) than at rest (median 0.22, range 0.05-0.33). 6. It was concluded that the plasma ANF concentration in a peripheral arm vein is a good indicator of the systemic peptide concentration at rest as well as during dynamic leg exercise.     

Reference values for 99mTc-MAG3 renography determined in healthy,potential renal donors

Background: Reference values for ^99mTc‐MAG₃ renography were determined and the influence of sex and age (<50/≥50 years) was elucidated. Methods: Sixty‐eight potential renal donors were evaluated by renography among other tests. Through examination of their records 41 healthy subjects with a normal renal arteriography were included in this study and the reference values of the functional distribution (the split function, SF), the time to peak renal parenchymal activity (T_max) and the residual activity (RA) were calculated. Results: For T_max there was no significant influence of sex or age. Mean RA increased significantly with age (20·5 vs. 23·2%, P=0·03), but no difference was found between sexes. Mean SF (right kidney) was significantly higher among males. Conclusions: When a diuresis of at least 2 ml min^?1 is demanded we found the following normal ranges: SF >41%, T_max <4·3 min and RA <33·7%.