Volume 4 Supplement 1

20th International Symposium on Intensive Care and Emergency Medicine

Open Access

Carbon dioxide elimination during continuous venovenous hemodiafiltration (CVVHD)-laboratory experiment

  • J Ruzicka1, 2,
  • I Novak1, 2,
  • R Rokyta1, 2,
  • M Matejovic1, 2,
  • P Hora1, 2,
  • M Hadravsky1, 2 and
  • V Sramek1, 2
Critical Care20004(Suppl 1):P40

DOI: 10.1186/cc760

Published: 21 March 2000

Full text

Objective

In a previous experiment with crystalloid solution we have shown that during CVVH(D) CO2 losses are proportional to the fractional ultrafiltration (UF) rate of circulating solution, with only a marginal impact of dialysis and temperature [1]. We report here results of a similar experiment with packed RBC.

Methods

Packed RBC were heparinized, diluted with crystalloid solution with bicarbonate to hematocrit of 0.35 and continuously saturated in a special mixing chamber to targeted pCO2value of 5 kPa. After equilibration, the mixing chamber was connected to a PRISMA monitor (Prisma, Hospal, France) at a blood rate (Qb) of 150 mlhr-1and different CVVH(D) settings were tested for CO2 elimination at two temperature levels (37 and 40°C). Blood samples were drawn in triplicate at each setting before and after the filter for blood gases analysis (ABL 520, Radiometer, Denmark). CO2 content was calculated using standard formula [2] and CO2 removal was expressed as pre-postfilter CO2 content difference.

Results

CO2 removal values (in % of prefilter CO2content) are summarised in Table 1 (means).

Conclusion

The often used CVVH setting (UF 1000 ml/hr, Qb 150 ml/min) leads to CO2 elimination at about 5 ml/min, i.e. a negligible part of the whole body CO2 production (VCO2). A significant CO2 loss (about 15% ofVCO2) can be expected using high volume ultrafiltration techniques.

Table 1

Blood temperature 37°C

Blood temperature 40°C

 

UF 1000

UF 3000

 

UF 1000

UF 3000

Dial 0

4.2%

6.8%

Dial 0

5.2%

11.0%

Dial 1000

7.4%

9.6%

Dial 1000

7.0%

13.0%

Dial 2500

10.7%

13.3%

Dial 2500

9.4%

15.4%

Dial-dialysis [ml/hr], UF-ultrafiltration [ml/hr]

Declarations

Acknowledgement

This paper was supported by GAUK, Czech Republic.

Authors’ Affiliations

(1)
ICU and Department of Biophysics, Medical Faculty of Charles University
(2)
Department of Biophysics

References

  1. Ruzicka J, Šrámek V, Novák I, Hadravský M, Rokyta R, Hora P, Mate-jovic M, Nalos M: Gas exchange during continuous extracorporeal elimination techniques (CRRT). In Anaesthesia, Pain, Intensive Care and Emergency Medicine Selected Papers. Edited by Gullo A 1998, p409.Google Scholar
  2. Giovannini I, Chiarla C, Boldrini G, Castagneto M: Calculation of venoarterial CO 2 difference. J Appl Physiol 1993, 74: 959-964.PubMedGoogle Scholar

Copyright

© Current Science Ltd 2000

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