EDITOR:

We have read Dr Davidson’s article on volume replacement using colloids with great interest [Reference Davidson1]. The author made great efforts to analyse the influence of different colloids on kidney function. The author’s conclusion that ‘Colloids display important differences in their actions on the kidneys’ is precise and well balanced. Unfortunately, the author did not distinguish the effects of the different hydroxyethylstarch (HES) preparations on renal function with the same accuracy. He cited several studies and concluded that ‘Undesirable renal effects are common to all available HES solutions … ’. Several articles were cited, however, without any cautious comments of their value: the multicentre study by Schortgen and colleagues [Reference Schortgen, Lacherade and Bruneel2] is one such example. This study has already been criticized by others [Reference Gosling, Rittoo, Manji, Mahmood and Vohra3,Reference Godet4] showing that patients treated with 6% HES 200/0.62 were not different from a gelatin-treated group with regard to the need for renal-replacement therapy – mortality was also not different; there was even no trend for increased mortality in the HES 200/0.62-treated group. The definition of acute renal failure (ARF) was based only on the creatinine levels. Unfortunately, these were already higher in the HES-treated group at baseline compared to the gelatin-treated group, suggesting that renal function was perhaps quite different already at the start of the study.

Most importantly, however, we feel urged to comment on some of the author’s statements because he is referring to some of our articles – but with entirely different conclusions from those that we reached. In one of our studies focussing on the effects of HES 130/0.4 on kidney function in elderly patients undergoing cardiac surgery using cardiopulmonary bypass [Reference Boldt, Brenner, Lehmann, Lang, Kumle and Werling5], we used the gelatin-treated group as our control group because there are no well-performed studies showing increased incidence of ARF requiring haemodialysis after the use of gelatins. Dr Davidson confirmed his conclusion that ‘Renal dysfunction was documented in HES 130/0.4 recipients by all four markers (of impaired kidney integrity)’ by showing our graphs. In our study, we came to a completely different conclusion. All measured kidney-specific proteins increased in our elderly patients, without showing differences between the two volume-replacement regimens. There is convincing evidence that cardiac surgery using CPB is associated with alterations in kidney integrity [Reference Yallop and Smith6], especially in elderly patients. Kidney dysfunction can be either moderate or severe, requiring haemodialysis. Occult and moderate alterations in kidney integrity secondary to cardiopulmonary bypass have been identified by kidney-specific proteins [Reference Fauli, Gomar, Campistol, Alvarez, Manig and Matute7,Reference Loef, Epema, Navis, Ebels, vanOeveren and Henning8]. As increase of kidney-specific proteins was only moderate in our study and gelatin-treated patients showed very similar changes, we concluded that the newest, third generation HES preparation (HES 130/0.4) is unlikely to change kidney integrity.

The influence of volume-replacement strategies on kidney function is a much-debated issue. However, no more reviews, meta-analyses, or overviews are necessary; instead, further well-performed research must be undertaken to fully evaluate the influence of specific volume-replacement strategies in specific patient populations. The information given by Dr Davidson does not help us much. Perhaps we should remember Winston Churchill: ‘We are still confused – but on a much higher level’.