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J P de Vries

Publications and source records attributed to J P de Vries.

10 recordsLinked to original sources
PubMed1997

Impedance cardiography in cardiac surgery patients: abnormal body weight gives unreliable cardiac output measurements.

BACKGROUND: To study the accuracy of cardiac output measurement by means of Electrical Impedance Cardiography (EIC) in post-cardiac surgery patients. METHODS: In a prospective study, we compared cardiac output measurements by means of thermodilution (COTD) with impedance cardiographic-derived values (COEIC) in 37 mechanically ventilated patients after cardiac surgery. Both methods were used simultaneously. RESULTS: COEIC values were weakly correlated with COTD in the total group when the equation of Sramek-Bernstein was employed to calculate COEIC (r = 0.60, P < 0.001, mean difference and standard deviation: -0.06 +/- 1.25 l.min-1). After exclusion of the 12 patients whose body weight differed > 15% from their ideal body weight, no significant difference was found between the mean values (5.40 +/- 1.80 l.min-1 (COEIC) vs 5.31 +/- 1.69 l.min-1, n = 25) while the correlation coefficient increased substantially (r = 0.85, P < 0.001, mean difference and standard deviation: 0.09 +/- 0.96 l.min-1). CONCLUSIONS: The results of this study indicate that weight is a very important factor in unreliable measurement of CO by impedance cardiography in cardiac surgery patients. The calculation equation as proposed by Sramek and Bernstein is not accurate enough in patients with more than 15% of weight deviation. Therefore, the use of impedance cardiography in these patients is of limited value until an accurate correction factor has been developed.

Adult↗
PubMed1995

Interstitial fluid volume during cardiac surgery measured by means of a non-invasive conductivity technique.

Fluid accumulation in the interstitium is frequently found after cardiac surgery. In extreme this can lead to pulmonary and myocardial oedema. The origin of this accumulation is not exactly known and may be twofold. It is probably a combination of the noninfectious whole body inflammatory response and a change in Starling forces due to a decrease in colloid osmotic pressure (COP) which is caused by the primed extracorporeal circuit. To study the changes in interstitial fluid volume (ISFV) a non-invasive conductivity technique was used. The relationship between temperature and conductivity was first investigated in vitro. A linear relationship was found between conductivity and different saline solutions and temperature. From the in vitro experiments it can be concluded that temperature corrected conductivity does not depend on haematocrit. After the in vitro experiments eleven patients undergoing cardiac surgery were studied. During the first minutes of cardiopulmonary bypass (CPB) a steep significant decrease in COP to 61.4 +/- 6.9% (from 19.6 +/- 1.1 to 12.0 +/- 1.2 mmHg), and a rise in ISFV to 105.5 +/- 2.8% (from 12.3 +/- 1.4 mS to 14.0 +/- 1.3 mS) was noticed. After this decrease COP increased significantly, till the end of the operation, but did not reach the pre-operative level. An increase in ISFV was noticed till the rewarming point. After this point no significant change in ISFV was noticed. Furthermore, a significant correlation was found between the fluid balance and the ISFV increase at the start, at the end of CPB, and at the end of the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Determination of the relation between alterations of total body water and thoracic fluid content during ultrafiltration by bioelectrical impedance analysis.

UNLABELLED: Total body impedance (TBI) is used to monitor alterations in total body water (TBW), e.g. during haemodialysis. However, 80% of the TBI signal is due to the resistance in extremities. Therefore TBI measurements give little information about alterations in thoracic fluid content (TF). Measuring both total body impedance and thoracic impedance (THI) can be a useful method to monitor TBW and TF changes during haemodialysis. In this study TBI and THI measurements were performed during 30 dialysis sessions and also in one group of 24 control subjects with normal tissue hydration. During haemodialysis TBI and THI significantly increased, demonstrating a decrease of TBW and TF. The ratio THI/TBI did not differ significantly during haemodialysis, indicating a similar effect of ultrafiltration on TBW and TF. The finding that TF decreased during haemodialysis was rather surprising, whereas pulmonary oedema is not an evident clinical problem in patients on maintenance haemodialysis treatment. THI measurements after dialysis proved to be significantly higher in comparison to the control subjects. This finding supports the hypothesis that the decrease in TF during dialysis is partly due to the sudden ultrafiltration-induced hypovolaemia leading to a fall in thoracic blood volume. ABBREVIATIONS: UF volume, ultrafiltration volume; TBI, total body impedance; THI, thorax impedance; TBW, total body water; TF, thoracic fluid.

Aged↗
PubMed1994

Assessment of refill and hypovolaemia by continuous surveillance of blood volume and extracellular fluid volume.

During renal replacement therapy hypovolaemia due to ultrafiltration (UF) may, when not sufficiently counteracted by refill from the interstitium, result in hypotension. Combining two recently developed methods the haemodynamic process of refill was studied in order to find characteristics featuring hypotension. Relative blood volume (BV) and extracellular fluid volume (EFV) were measured continuously in 40 stable haemodialysis patients by means of an optical and a conductivity technique respectively. Regarding their postdialytic (PD) EFV the patients were divided into three groups: normohydrated (N, n = 20), dehydrated (D, n = 11) and overhydrated (O, n = 9). Significant differences between the groups were assessed in BV decrease (after 2 h until the end of treatment P < 0.05 and after 3 h P < 0.01), EFV decrease (after 3 h P < 0.05) and occurrence of hypotensive episodes (N,5; D,7; O,none; P < 0.01). During the entire session the speed of BV decrease was significantly higher in hypotensive patients (H) than in non-hypotensive patients (non-H). At the moment of hypotension (after 141 +/- 49 min) residual BV was less (P < 0.0005) in H (87.7 +/- 5.2%) than at the corresponding moment in non-H patients (96.5 +/- 4.0%). PD BV and PD EFV, both expressed as a percentage of the starting value, correlated significantly (r = 0.63, p < 0.005) and UF-volume (differences between the groups were not significant) correlated to EFV decrease (r = 0.45, P < 0.005). In conclusion, the combination of both non-invasive methods elucidates the pathophysiology of UF-induced hypotension and provides a means of reducing dialysis morbidity. The influence of tissue hydration state on these variables has been shown.

Aged↗
PubMed1993

Non-invasive monitoring of blood volume during hemodialysis: its relation with post-dialytic dry weight.

Hemodialysis has a profound effect on fluid balance. Since fluid is initially withdrawn from the intravascular compartment, blood volume will decrease rapidly. A fluid shift (refill) from the overhydrated interstitium towards the intravascular compartment counteracts hypovolemia. Underestimation of postdialytic dry weight will cause interstitial dehydration and consequently a low refill capacity. This can cause hypovolemia-induced hypotension, a serious problem in the daily practice of hemodialysis: during one out of three sessions a hypotensive episode occurs. Clinical criteria to estimate post-dialytic dry weight are insensitive. We have developed non-invasive methods to estimate dry weight and changes in blood volume (BV) more accurately. The aim of this study was to investigate the relation between hydration state of the patient and changes in BV during treatment. Therefore, 37 hemodialysis patients were divided into three groups according to their post-dialytic extracellular fluid volume (EFV), which was measured by means of the non-invasive conductivity method: de- (N = 11), normo- (N = 18), and overhydrated (N = 8). Using an on-line optical reflection method, changes in BV were measured continuously during hemodialysis. BV decrease, corrected for ultrafiltration, was stronger in the dehydrated (4.4 +/- 1.5%/liter) than in the normohydrated (3.3 +/- 1.5%/liter) and overhydrated (2.7 +/- 1.9%/liter) groups. In the dehydrated group, the frequency of hypotensive episodes (48.5 +/- 20.2%) was significantly greater compared to the normohydrated (20.5 +/- 23.5%) or overhydrated (6.5 +/- 6.5%) group, P < 0.005.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

The influence of Ringer's lactate and gelatin infusion on the internal fluid balance of healthy volunteers measured by a non-invasive conductivity technique.

Eight healthy male volunteers received in random order at an interval of 1 week 2 litres of Ringer's lactate or 0.8 litre of gelatin (Gelofusine) over half an hour, after overnight fasting. At the end of the infusion period, blood volume and mean arterial pressure had increased significantly in both groups but the increase in blood volume was more pronounced with the colloid. Extracellular fluid volume increased significantly after Ringer's lactate, while a significant decrease was noticed after gelatin. A small decrease in intracellular fluid volume was noted after infusion of Gelofusine, whereas it did not change after infusion of Ringer's lactate. During the 30 min after infusion, blood volume decreased significantly after both treatments but after the colloid it remained higher than the initial value. During the post-infusion period, no significant changes in either intra- or extracellular volume were seen after either treatments. At the end of the study, urine production was significantly more after the Ringer's lactate. It can be concluded that infusion of 0.8 litre of gelatin results in a larger and longer lasting increase in blood volume than 2 litres of Ringer's lactate, probably due to mobilization of extracellular fluid volume. It also leads to extracellular fluid accumulation. The decrease in blood volume after infusion is caused by increased urine production, since no changes were seen in intra- and extracellular fluid volume during this period.

Adult↗
PubMedDate not supplied

Continuous measurement of blood volume during hemodialysis by an optical method.

A new method is described to noninvasively and continuously measure changes in blood volume (BV) during hemodialysis by means of an optical reflection method with an optical monitor (950 nm) clipped onto the arterial blood line. The amount of reflected light (L) appeared to be linearly proportional to the erythrocyte concentration (r = 0.91). Changes in L correlated well with changes in erythrocyte concentration during hemodialysis (r = 0.94). A study in 10 patients on regular dialysis was done. The BV decrease after 3 hr of treatment was 17.0 +/- 5.2%, and it correlated with the amount of fluid withdrawn by ultrafiltration (mean, 2,519 +/- 589 ml). Five hypotensive episodes were seen that were characterized by a higher rate of BV fall during the preceding 15 min (9.9 +/- 1.9 versus 3.6 +/- 4.3%/hrp; p < 0.05) and by a lower BV value at that moment (78.2 +/- 3.4 versus 84.5 +/- 4.5%; p < 0.025) than in the other five patients at comparable times. It was concluded that this optical method was a means to detect hypovolemia at an early stage and to prevent ultrafiltration induced hypotension.

Adult↗