The Uremic Environment and Muscle Dysfunction in Man and Rat

BACKGROUND

Patients reaching end-stage renal disease experience debilitating fatigue, with progression of this disease, rendering patients dysfunctional in their everyday lives.

METHODS

In vivo measurements of muscle function, assessed using surface electromyography (EMG), were made on 25 patients prior to and after a session of hemodialysis (HD) treatment, along side in vitro measurements of muscle function in isolated rat muscles incubated in normal or uremic conditions approximating to those found in uremic rats (rat uremic: RU) or uremic humans (human uremic: HU).

RESULTS

HD significantly affected plasma values, e.g. reducing urea (69%), creatinine (62%), potassium (23%) and phosphate (48%) concentrations in patients (all p < 0.01). Treatment also improved the EMG frequency of 2nd dorsal interosseous (fast-twitch) (p < 0.01), although no change was noted for vastus lateralis (slow-twitch). In isolated rat muscles, a uremic environment had no significant effect on slow-twitch soleus during field stimulation, however, in fast-twitch extensor digitorum longus, a significant 23% (RU) and 22% (HU) faster rate of decline in force was measured, compared to controls (p < 0.001 and p < 0.01, respectively).

CONCLUSION

It is concluded that (1) muscle weakness and its electrophysiological correlates may be rapidly induced by uremic solutes and rapidly reversed when the solutes are removed by dialysis, and (2) fast-twitch muscles are more readily affected by uremic conditions than slow-twitch muscles.

Exercise training and the progression of chronic renal failure

The possible beneficial effect of regular exercise training on the progression of chronic renal failure was studied in a prospective randomized controlled study. Thirty patients with a median glomerular filtration rate (GFR) of 25 ml/(min.1.73 m2) (range 10-43) were randomized to physical training (30 min of bicycling daily or an equal amount of other physical activities) or to maintenance of the usual lifestyle. The median maximal work capacity increased significantly in the exercise group and remained unchanged in the control group during a median observation time of 20 months whereas the rate of progression judged by the slope of GFR versus time plot was equal in the two groups. Hence, the beneficial effect of exercise training, earlier observed in rat studies, could not be reproduced in our patients. Physical exercise had no untoward effect on progression of renal disease.

Insulin resistance and hyperinsulinaemia in mild to moderate progressive chronic renal failure and its association with aerobic work capacity

Tissue sensitivity to insulin and aerobic work capacity was measured in patients with mild to moderate progressive chronic renal failure. Twenty-nine non-diabetic patients with a glomerular filtration rate of 25 ml.min-1.1.73 m-2 (11-43) (median, range) and 15 sex, age, and body mass index matched control subjects with normal renal function were studied. Fasting blood glucose was comparable and in the non-diabetic range in the two groups as was the oral glucose tolerance test. Patients demonstrated hyperinsulinaemia both during fasting (p < 0.01) and during the test (p < 0.02). The tissue sensitivity to insulin, expressed by the amount of glucose infused during the last 60 min of a 120-min hyperinsulinaemia euglycaemic clamp (M-value) and the M/I ratio, was significantly lower in the patients than in the control subjects (M-value 404 +/- 118 vs 494 +/- 85 mg glucose/kg body weight, p < 0.02) (M/I ratio 1.77 +/- 0.71 vs 2.57 +/- 0.70 (mg/(kgBW.min) per pmol/l.100, p < 0.001). The maximal aerobic work capacity was significantly lower in the patients than in the control subjects (24 +/- 8 vs 32 +/- 11 ml O2/(kg body weight.min), p < 0.02) and positively correlated to the M-value and the M/I ratio in both groups. In conclusion, not only patients with end-stage chronic renal failure but also those with mild to moderate progressive chronic renal failure are insulin resistant and hyperinsulinaemic. The tissue sensitivity to insulin is correlated to the maximal aerobic work capacity suggesting that these patients might benefit from physical training programmes.

Vascular endothelial cell function and cardiovascular risk factors in patients with chronic renal failure

Cardiovascular risk factors and markers of endothelial cell function were studied in nondiabetic patients with mild to moderate chronic renal failure. The transcapillary escape rate of albumin and the plasma concentrations of von Willebrand factor, fibrinogen, and plasma lipids were measured in 29 nondiabetic patients (GFR of 25 (11-44) mL/min x 1.73 m2 (median and range)) and 14 normal subjects. The proportion of smokers was similar between the groups. In the patients, the plasma concentration of von Willebrand factor was elevated by 61% (1.27 +/- 0.44 versus 0.79 +/- 0.28 U/mL; P < 0.01) (mean +/- SD) and that of fibrinogen was elevated by 72% (10.18 +/- 4.14 versus 5.92 +/- 2.01 mumol/L; P < 0.01). The plasma concentrations of lipoproteins showed an atherogenic pattern in the patients with increased levels of very low-density lipoprotein cholesterol (0.57 +/- 0.31 versus 0.33 +/- 0.13 mmol/L; P < 0.01) and triglycerides (1.26 +/- 0.25 versus 0.71 +/- 0.28 mmol/L; P < 0.01), but a decreased level of high-density lipoprotein cholesterol (1.23 +/- 0.33 versus 1.46 +/- 0.35 mmol/L; P < 0.05). Total cholesterol and low-density lipoprotein cholesterol were similar in the groups. The observed differences were further aggravated among smoking patients, particularly with respect to von Willebrand factor and triglycerides. The transcapillary escape rate of albumin was similar in the patients and the controls and was not correlated to the level of albuminuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in blood and plasma volume during treatment with recombinant human erythropoietin

18 chronic dialysis patients with renal anemia were examined before and after three months of regular treatment with recombinant human erythropoietin (EPO). All patients responded with an increase in hemoglobin concentration (cHb). The target cHb of 7.0 mmol/L was subsequently maintained by one subcutaneous injection a week, obviating the need of blood transfusions. The amount of circulating hemoglobin and the volume of erythrocytes increased, but the plasma volume simultaneously decreased, maintaining a constant blood volume. Although some of the individual blood volumes varied, the relation between circulating hemoglobin and the hemoglobin concentration still existed. We conclude that the hemoglobin concentration gives an accurate measure of the degree of anemia, and measurement of circulating hemoglobin is unnecessary during routine treatment of dialysis patients with EPO.

Clinical evaluation of the Takeda Medical (A & D) TM 2420 ambulatory blood pressure monitor. Practical experience and comparison with direct and indirect measurements

Takeda Medical (A & D) TM 2420 is an automatic ambulatory blood pressure monitoring system employing the auscultatory technique. The device was used under stable conditions and compared to readings from the Hawksley random-zero sphygmomanometer using a double headset stethoscope and a Y-connection. We tested 85 subjects (aged 13-89 years, systolic blood pressure 85-212 mmHg, diastolic blood pressure 40-116 mmHg) and found a difference amounting to 1.6 +/- 6.7 mmHg (mean +/- SD) for systolic and 2.1 +/- 4.5 mmHg for diastolic readings (Hawksley-TM 2420). In 62 subjects a comparison with simultaneous measurement on the opposite arm with the Hawksley manometer showed similar results. When comparing intra-arterial readings from 10 subjects, a difference (intra-arterial-TM 2420) of -1.9 +/- 12.1 mmHg was found for systolic pressures, while the diastolic difference was -10.7 +/- 8.7 mmHg. Twenty-four hour monitoring was performed on 80 subjects; 70 of these yielded usable tracings. The proportion of successful recordings was acceptable, but the device was not suitable for bicycle stress testing. The quality of the accessories provided with the equipment could be improved, but in spite of this the monitoring system was found to be recommendable for clinical use.

[The new ambulatory non-invasive 24-hour blood pressure monitoring system, Takeda Medical TM 2420. Reliability and practical experiences]

Takeda TM 2420 is an automatic ambulant device for measuring blood pressure which functions by auscultation of the Korokoff sounds. During static conditions, the apparatus was investigated by means of a double stetoscope and a connecting branch with the Hawksley random zero manometer. Where 69 persons were concerned (ages 13-89 years, systolic blood pressures 85-212 mmHg, diastolic blood pressure 44-110 mmHg) a difference in the systolic blood pressure of 1.5 +/- 9.2 mm Hg were found (average +/- standard deviation) and where the diastolic blood pressure was concerned 2.8 +/- 6.3 mm Hg. Statistical comparison with the Hawksley manometer on the contralateral arm in 51 volunteers produced corresponding results. In 24-hour monitoring of 80 persons, useful results were obtained in 74. The proportion of erroneous measurements was acceptable but the apparatus was unsuitable for exercise testing on an ergometer bicycle. The quality of the cuff, the connecting tubing, the carrying strap and computer programmel should be improved but the apparatus was otherwise found to be useful for daily clinical use.

[The time interval before hospitalization in acute myocardial infarction]

The prehospital time interval in 103 patients with acute myocardial infarction was investigated. Twenty patients were admitted with cardiac arrest. In the remaining patients the average total delay was found to be 3.3 hours and the patient delay 1.5 hours. The total delay was significantly prolonged in patients who were admitted during working hours, patients who were unaffected on admission, patients transported for long distances, patients who had been visited by their doctors prior to admission and patients who contacted their own doctors. The authors find that attempts should be made to reduce these delays by means of information both to the public and to doctors.

[Heart-lung transplantation]

To date, more than 200 human heart-lung transplantations (HLT) have been performed in USA and Europe. The main indications are still primary pulmonary hypertension and Eisenmenger's syndrome but the intervention has also been employed in cases of parenchymatous pulmonary disease. At operation, the thoracic organ is replaced. The recipient's heart can frequently be donated. Recent reviews suggest acceptable two-year survival following HLT of approximately 60%. The direct economical costs of transplantation have been stated to be approximately 17,000 pounds but to this must be added the expenses for life-long immunosuppressive treatment and follow up control together with hospitalization during the time waiting for a suitable donor. The annual requirement for transplantation in Denmark is estimated at present to be approximately ten patients. The immediate requirement for transplantation will probably be covered by referral to the European centres via national or provincial hospitals and with the permission of the Danish Board of Health. The case reports of the first two Danes (both with emphysema secondary to alpha-1-antitrypsin deficiency) who underwent successful heart-lung transplantations in England are presented. In the long run, it will prove necessary to utilize Danish donors which necessitates alterations in the criteria of death.