Microalbuminuria was one of the variables used in this study to measure the degree of vascular permeability. Microalbuminuria is non-specific and is known to occur after anaesthesia and surgery.2 3 Did microalbuminuria in these patients correspond to other measures of lung injury? These data are not reported.
Plasma elastase is another variable used to assess lung injury. Although it is specific for neutrophil activity, it can increase after red blood cell and cell saver blood transfusion.4 5 In this study, the patients received both red blood cell transfusion and cell saver blood, but the quantities administered in each group are not reported. Hence, it is unclear whether one can attribute the increase in neutrophil elastase to lung injury alone.
The authors have used the chest x-ray and /
to assess the presence of pulmonary oedema. A history of cardiac disease is present in >70% of patients presenting for aortic aneurysm surgery.6 The incidence of myocardial infarction and heart failure in the postoperative period in the same group of patients is 3.3%.6 We did not find any attempt by the investigators to rule out cardiac causes of pulmonary oedema.
Resuscitation using colloids has not been shown to be superior to crystalloids.7 8 In many practices (including our own), crystalloid solutions are the main resuscitation fluid. Given that colloid molecules do eventually cross even normal vascular epithelium, entering the interstitium where they continue to exert an oncotic effect,9 we question the long-term benefit of use of colloid resuscitation in these cases. We look forward to studies including a crystalloid resuscitation arm in the experimental design.
Boston, MA, USA
The authors' data show some intriguing results, especially in the difference in respiratory compliance between the two study groups. However, their paper is rendered less convincing by several errors and omissions. In particular, what we assume to be a typographical error (the time periods T7 and T8 both being stated as 48 h), made interpreting the information supplied difficult. Furthermore, as there is no mention of how the study is powered, we are uncertain as to the significance that we can attach to the statistics.
We would also appreciate some further information about the clinical course of the patient groups. Specifically, the postoperative fluid regimen is unclear to us. It appears that patients received both crystalloid at 2 ml kg1 h1 and crystalloid adjusted to maintain the urine output at 40 ml h1, but there is no mention of the postoperative colloid routine. Does this indicate that no colloid was used postoperatively? It would be useful for interpreting the data if the paper was a little clearer on when the colloid was stopped in relation to the time of surgery. More worryingly, there is no mention of the amount of donor blood and blood products transfused. Because donor blood transfusion may be an independent cause of acute lung injury, we believe this to be an important omission.1012
With respect to the scoring systems used, we would like some more information, especially as most of the data appear to have been transformed into another set of numerical values before being statistically evaluated. The authors comment that the calculation of the lung injury score was computed by the number of components used (the maximum of which was four), but no mention is made of how many patients were scored on fewer than four components, or how many components each patient was scored on. This appears to us to be important as it might statistically skew the data, invalidating the findings. We are also confused by the method of allocating the postoperative hypoxaemia score. Is there any significance to the ratio of 23.3? Why is this number used instead of 20.0 as the cut-off for severity?
We found this to be potentially interesting data, and it is a pity that it has been obscured by a lack of some important information.
London, UK
There is now extensive evidence that HES volume expansion has advantages over albumin, gelatin or crystalloid resuscitation. Space will not allow a full reference list, but we cite a recent comparison of crystalloid vs HES in elderly surgical patients demonstrating the anti-inflammatory effects of HES.15 It was considered unethical in our hospital to use crystalloids only as fluid resuscitation in patients undergoing aortic aneurysm surgery because of the now well-recognized advantages of HES over crystalloid-only volume therapy.
We thank van Hoogstraten for pointing out the typographical errors that are evident when reading the paper. The power calculation for this study was based on a similar study in trauma patients. The statistics used in the study are well laid out in a separate paragraph in the paper.
In this study, patients were randomized to receive the study colloid for the first 24 h only, and blood was transfused to maintain a haemoglobin concentration of 10 g dl1. While we accept that transfusion of large volumes of blood may cause acute lung injury, the volumes of blood transfused were comparable in both groups and we felt that this was not an important issue in this study. However, we accept that omission of these data may have obfuscated readers.
The lung injury score (LIS) was computed by dividing the aggregate score by the number of components used, the maximum of which was four. In seven patients in both groups of patients, only three components were used to compute the LIS. In the remaining patients all four components were used. The postoperative hypoxaemia score is based on published criteria.
Birmingham, UK
References
1 Rittoo D, Gosling P, Burnley S, et al. Randomized study comparing the effects of hydroxyethyl starch solution with Gelofusine on pulmonary function in patients undergoing abdominal aortic aneurysm surgery. Br J Anaesth 2004; 92: 616
2 De Gaudio AR, Piazza E, Barneschi MG, Ginanni R, Martinelli P, Novelli GP. Perioperative assessment of glomerular permeability. Anaesthesia 1995; 50: 81012[ISI][Medline]
3 Mercatello A, Hadj-Aissa A, Chery C, et al. Microalbuminuria is acutely increased during anesthesia and surgery. Nephron 1991; 58: 1613[ISI][Medline]
4 Nishiyama T, Aibiki M, Hanaoka K. The effect of ulinastatin, a human protease inhibitor, on the transfusion-induced increase of plasma polymorphonuclear granulocyte elastase. Anesth Analg 1996; 82: 10812[Abstract]
5 Sieunarine K, Langton S, Lawrence-Brown MM, Goodman MA, Prendergast FJ, Hellings M. Elastase levels in salvaged blood and the effect of cell washing. Aust N Z J Surg 1990; 60: 61316[ISI][Medline]
6 Cruz CP, Drouilhet JC, Southern FN, Eidt JF, Barnes RW, Moursi MM. Abdominal aortic aneurysm repair. Vasc Surg 2001; 35: 33544[Medline]
7 Bunn F, Alderson P, Hawkins V. Colloid solutions for fluid resuscitation. Cochrane Database Syst Rev 2003; CD001319
8 Virgilio RW, Rice CL, Smith DE, et al. Crystalloid vs colloid resuscitation: is one better? A randomized clinical study. Surgery 1979; 85: 12939[ISI][Medline]
9 Roberts JS, Bratton SL. Colloid volume expanders. Problems, pitfalls and possibilities. Drugs 1998; 55: 62130[ISI][Medline]
10 Silliman CC, Boshkov LK, Mehdizadehkashi Z, et al. Transfusion-related acute lung injury: epidemiology and a prospective analysis of etiologic factors. Blood 2003; 101: 454622
11 Wyncoll DL, Evans TW. Acute respiratory distress syndrome. Lancet 1999; 354: 497501[CrossRef][ISI][Medline]
12 Kopko PM, Holland PV. Transfusion-related acute lung injury. Br J Haematol 1999; 105: 3229[ISI][Medline]
13 Gosling P, Shearman CP, Gwynn BR, Simms MH, Bainbridge ET. Microproteinuria: response to operation. Br Med J 1988; 296: 3389[ISI][Medline]
14 Gosling P, Sanghera K, Dickson G. Generalized vascular permeability and pulmonary function in patients following serious trauma. J Trauma 1994; 36: 47781[ISI][Medline]
15 Boldt J, Ducke M, Kumle B, Papsdorf M, Zurmeyer EL. Influence of different volume replacement strategies on inflammation and endothelial activation in the elderly undergoing major abdominal surgery. Intensive Care Med 2004; 30: 41622[CrossRef][ISI][Medline]