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Biomedical subjects

C H Kong

Publications and source records attributed to C H Kong.

10 recordsLinked to original sources
PubMed1999

The effect of exercise during haemodialysis on solute removal.

BACKGROUND: Urea rebound results as urea re-equilibrates between intracellular and intravascular compartments post haemodialysis. The mechanism of the rebound is thought to be due to either a reduced diffusion rate or blood flow. It is hypothesized that low blood flow in the skeletal muscles might be responsible. We tested this by studying the effect of exercise during dialysis on the removal of urea, creatinine and potassium. METHODS: Eleven patients (aged 32-78 years) on haemodialysis (4-58 months) were studied on paired dialysis sessions; one with exercise and the other as a control. Patients pedalled on a cycle for 5-20 min at submaximal workload followed by 10 min rest to achieve a total of 60 min exercise. Plasma concentrations of urea, creatinine and potassium were measured pre-, post- and 30-min post dialysis. The post-dialysis rebound (% rebound) and reduction ratios (RR) of the solutes and equilibrated (two-pool) urea Kt/V were calculated for comparison. RESULTS: The rebound of all three solutes was reduced significantly following exercise. The rebound of urea decreased from 12.4 to 10.9% (median, P<0.01 Wilcoxon signed rank test), creatinine from 21.2 to 17.2% (P<0.001) and potassium from 62 to 44% (P<0.05). Kt/V and RR increased significantly as a result: Kt/V urea from 1.00 to 1.15 (P=0.001), RR urea from 0.63 to 0.68 (P<0.001); Kt/V creatinine from 0.71 to 0.84 (P<0.01); and RR creatinine from 0.51 to 0.57 (P<0.05). CONCLUSION: Exercise increased the efficiency of dialysis by reducing the rebound of solutes due to increased perfusion of the skeletal muscles.

Adult↗
PubMed1997

Correlation between bactericidal activity and postantibiotic effect for five antibiotics with different mechanisms of action.

Theoretically, if the postantibiotic effect (PAE) reflects the duration of cellular recovery, then the extent of cellular damage inflicted on bacteria by an antibiotic, as suggested by the degree of bactericidal activity, should reflect the length of PAE; this is especially true if binding of the antibiotic to bacterial receptors is irreversible. To test this hypothesis, correlation between PAEs and bactericidal rate constants measured simultaneously at various antibiotic concentrations was examined for five antibiotic-bacterium combinations. Each of the five antibiotics used, i.e. tobramycin, ciprofloxacin, dicloxacillin, trimethoprim and tetracycline, has a different mechanism of action: the first three bind irreversibly to bacterial receptors, while trimethoprim and tetracycline bind reversibly. Both PAE and bactericidal activity increased nonlinearly with concentrations in a saturable manner for all the combinations studied. Linear least-square regression analyses showed strong correlations (P < 0.01) between the two responses for individual combinations. Such a linear relationship also extended, with good correlation (P < 0.05), across the five combinations when individual maximal bactericidal rate constants and PAEs were considered separately. These observations suggest that cellular recovery from nonlethal damage following antibiotic exposure may be a major determinant of PAE.

Anti-Bacterial Agents↗
PubMed1993

The effect of recombinant human erythropoietin on cardiovascular responses to postural stress in dialysis patients.

The normal response to 45 degrees head-up tilt (decreased stroke volume and cardiac output and increased heart rate and peripheral resistance) is not seen in the majority of haemodialysis patients. This is due to both an abnormal baroreceptor reflex and increased venous tone which may be explained by a number of factors including hypoxia, acidosis and sodium retention. We have studied this response by impedance cardiography in eight chronic haemodialysis patients, both before and after 3 months of treatment with human recombinant erythropoietin. Before treatment the cardiovascular parameters were abnormal both at rest and on tilting in each patient. The change in each measurement following tilting was: stroke volume, 0.5 +/- 6%; cardiac output, 6 +/- 5%; peripheral resistance, -8 +/- 4%; and heart rate, 10 +/- 4%. After 3 months of erythropoietin (150 U/kg/week intravenously) the mean haematocrit had risen from 19.5 +/- 3% to 32.9 +/- 4% and all patients felt physically fitter. Impedance showed no change in the supine-indices but after tilting there was a dramatic fall in stroke volume (-26 +/- 7%) and cardiac output (-17 +/- 7%) and an increase in heart rate (15 +/- 4%) and peripheral resistance (28 +/- 10%) each moving towards the normal response. These results indicate that human recombinant erythropoietin normalizes the response to postural stress in these patients and suggest that anaemia is the principal cause of the abnormal venoconstriction seen in haemodialysis patients. The mechanisms involved warrant further investigation.

Adult↗
PubMed1993

Can bio-electrical impedance be used to measure total body water in dialysis patients?

The measurement of total body water (TBW) by bio-electrical impedance (BEI) in a group of renal patients was evaluated against the tritium dilution method. The effect of haemodialysis and the presence of peritoneal dialysate on the impedance were also investigated. The correlation between the two methods was r = 0.9, with the standard deviation of the differences being 3.66 l (TBW typically 40 l). The BEI method overestimated the actual weight loss after haemodialysis, but underestimated the volume of peritoneal dialysate in situ. The BEI method would not be appropriate for use in assessing total body water and monitoring acute volume changes in patients with renal failure who are on strict fluid restriction.

Adult↗
PubMed1993

Determination of total body water in uraemic patients by bioelectrical impedance.

The measurement of total body water by bioelectrical impedance in a group of renal patients was evaluated against the tritium dilution method. The effect of haemodialysis and the presence of peritoneal dialysate on the impedance were also investigated. The correlation between the two methods is r = 0.90 with a residual standard deviation of 3.7. The standard deviation of the differences between the two methods against the means was 3.66 which means that total body water (TBW) estimated by the bioelectrical impedance (BEI) method may be 6.18 l (X +/- 2 SD) above or 8.38 l below the 3H2O method. The BEI method overestimated the actual weight loss after haemodialysis (3.87 +/- 1.7 l versus 2.43 +/- 1.8 l) but underestimated the volume of peritoneal dialysate in situ. The BEI method would not be appropriate for use in assessing total body water and monitoring acute volume changes in patients with renal failure who are on strict fluid restriction.

Adult↗
PubMed1990

Cardiac output and oxygen uptake in patients with renal failure.

1. Cardiac index, oxygen uptake and haemoglobin concentration have been measured in eight patients with end-stage renal failure, and the values compared with those in eight healthy control subjects. Assuming the arterial blood to be 97% saturated, the oxygen saturation of mixed venous blood has been calculated. 2. Cardiac index was lower in the patients (2.45 +/- 0.42 litres min-1 m-2) compared with the control subjects (3.74 +/- 0.17 litres min-1 m-2). Oxygen uptake was reduced from 147 +/- 16 ml STP min-1 m-2 in the control subjects to 112 +/- 9 ml STP min-1 m-2 in the patients. 3. Oxygen saturation of mixed venous blood was 53 +/- 8% in the patients compared with 79 +/- 2% in the control subjects, suggesting some degree of tissue hypoxia. If oxygen uptake were not reduced in renal failure, then the mixed venous blood oxygen saturation would be as low as 40%. 4. The oxygen saturation of blood sampled from the superior vena cava of patients with renal failure was 57 +/- 6%. 5. The data on oxygen uptake and venous oxygen saturation suggest that in the patients with end-stage renal failure, the low values of cardiac index, previously measured by impedance cardiography, are accurate.

Adult↗
PubMed1990

Hemodynamic responses to head-up tilt in uremic patients.

The hemodynamic responses to 45 degrees C head-up tilt for 30 min were compared between a group of 13 normal healthy subjects, 16 patients with end-stage renal failure (Group 1) and 9 hypertensive patients (Group 2). In the normal subjects there was no change in systolic blood pressure (SBP), a significant increase in diastolic blood pressure (DBP) (9 +/- 1 mmHg, mean + SEM, p less than 0.01), heart rate (HR) (11 +/- 2 beats/min) and derived peripheral resistance (PR) (66 +/- 8%, p less than 0.001). Stroke volume (SV) and cardiac output (CO) fell significantly by 42 +/- 3% and 33 +/- 3%, respectively. The responses in Group 2 patients were similar to those of the controls. However in Group 1 patients, though there was a rise in heart rate (9 +/- 2, p less than 0.001), SBP fell significantly accompanied by no change in either DBP or PR. The decrease in SV was only 12 +/- 4% while there was no change in derived CO. The results suggest that there was a lack of vasoconstriction during postural stress in patients with endstage renal failure, which was probably due to a functional defect in the baroreceptor reflex. Concomitantly, the small decrease in SV suggests stiffness of the veins and/or active venoconstriction which may help to prevent a bigger fall in blood pressure.

Adult↗
PubMed1987

Cardiovascular and acid-base effects of acetate and bicarbonate haemodialysis.

Cardiovascular and acid-base changes were studied in 18 adult haemodialysis patients during a single dialysis against acetate or bicarbonate dialysate. Tachycardia was significantly greater with acetate but, otherwise, blood pressure and peripheral resistance fell and cardiac output increased to a similar degree with the two types of dialysate. Arterial PCO2 increased with bicarbonate and fell slightly with acetate, while hypoxaemia was significantly worse during acetate dialysis. Arterial acetate concentrations increased in 2 of 12 patients during bicarbonate dialysis. No differences in patient symptomatology or hypotensive episodes were noted with acetate or bicarbonate. Any beneficial effects of bicarbonate dialysis are more likely to be related to preservation of arterial PO2 than to the absence of adverse cardiovascular effects of acetate.

Acetates↗
PubMed1986

Effect of 2 liters of intraperitoneal dialysate on the cardiovascular system.

In 21 patients receiving continuous ambulatory peritoneal dialysis (CAPD), the effect of 2 liters of intraperitoneal dialysate on the supine and upright hemodynamics (19 patients), and the hemodynamic responses to 45 degrees head-up tilt (9 patients) were studied. Blood pressure (BP), heart rate (HR) and stroke volume (SV) (using impedance cardiography) were measured. In the supine position there was no significant difference in BP, SV, HR, derived cardiac output (CO) and peripheral resistance (PR) between "empty" (E) and "full" (F) conditions. On standing in both E and F conditions there were significant falls in systolic BP (p less than 0.001, compared with supine), SV and CO (p less than 0.05) accompanied by an increase in HR (p less than 0.001) but no significant change in peripheral resistance nor diastolic BP. The fall in systolic BP was greater in the E condition (from 149.3 +/- 4.5 mmHg to 134.6 +/- 5.9 in E, from 148.8 +/- 4 mmHg to 140.8 +/- 5.0 in F, p less than 0.001) and was accompanied by a bigger rise in HR (from 80.2 +/- 4.3 beat/min to 91.8 +/- 5.3 (E), from 79.4 +/- 4.4 to 87.7 +/- 5.2 (F, p less than 0.001). On tilting in 13 normal subjects there was an increase in diastolic BP (76.7 +/- 2.0 mmHg to 81.4 +/- 0.6, p less than 0.01), HR (63.3 +/- 2.4 beat/min to 73.6 +/- 1.0, p less than 0.01) and PR (13.4 +/- 1.0 mmHg/l/min to 21.3 +/- 0.2, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗