HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Donald C. Whitaker Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Harrison, M. J.G. Articles by Newman, S. P. Search for Related Content PubMed PubMed Citation Articles by Harrison, M. J.G. Articles by Newman, S. P. Related Collections Extracorporeal circulation Related Article

Ann Thorac Surg 2006;82:1166
© 2006 The Society of Thoracic Surgeons

---

Correspondence

Hematocrit During Cardiopulmonary Bypass

Unit of Health Psychology, Centre for Behavioural and Social Sciences in Medicine, UCL, Wolfson Building, 48 Riding House St, London, W1W 7EY United Kingdom

(Email: s.newman{at}ucl.ac.uk).

To the Editor:

Karkouti and colleagues [1] have recently reported a positive association between the nadir of operative hematocrit (Hct) during coronary artery bypass surgery (CABS), and the risk of perioperative stroke. A survey of 5,000 consecutive operations by Habib and colleagues [2] found the lowest quintile of Hct was also linked to vital organ dysfunction, morbidity, and 6-year survival.

We sought evidence of whether a low operative Hct was a risk factor for the development of cognitive disturbance in the aftermath of CABS. This analysis was performed in a cohort of patients recruited into a study that examined the impact of leukocyte depleting filter in CABS [3].

The details of recruitment of the operative technique and the neuropsychological assessment preoperatively and 6 to 8 weeks after elective CABS are described in the full report of the interventional study [3]. Here we set out the results of venous Hct measured preoperatively (42.7%; standard deviation [SD], 4.6%) 30 minutes after initiation of bypass (27.4%; SD, 4.9%) 10 minutes after the end of bypass (29.5%; SD, 3.4) and on the first postoperative day (32.1%; SD, 3.9%) in the 111 patients with full data at the time points.

The Z change scores were calculated for each of the 10 tests in the neuropsychological test battery between individuals performances 6 to 8 weeks postoperatively compared with the preoperative score. A global Z change score was also calculated for each patient's performances in the test battery as a whole.

No correlation was found (Pearson) between Hct levels of any time point including the nadir, and Z change scores of neuropsychological performance using either the global or individual test data. The subset of patients who were older than 65 years of age showed no association between Hct level and cognitive outcome.

This absence of an effect may relate to the success of the operative strategy of restricting falls of Hct below 20 (only 1 patient had a hematocrit during bypass below this level of 19.4%). By contrast Karkouti and colleagues [1] reported that 25% of their cases had levels below 20. Although the optimal Hct for cerebral oxygen delivery in humans is held to be 35.2% from positron emission tomography, in animal studies the compensation for loss of oxygen carrying capacity at low Hct is not obvious until 19%. Also, a better than expected compensation has been reported for the special circumstances of hypothermic bypass.

The lack of evidence for a low Hct contributing to the cognitive disturbance after CPB does not of course mean that the ongoing debate about the optimal Hct during bypass for other organs and other outcomes should be neglected. It may however provide a further pointer to what the target level should be.

	References

Top References

 

1. Karkouti K, Djaini G, Borger M, et al. Low hematocrit during cardiopulmonary bypass is associated with increased risk of preoperative stroke in cardiac surgery Ann Thorac Surg 2005;80:1381-1387.[Abstract/Free Full Text]
2. Habib RH, Zacharias A, Schwann TA, Riordan CJ, Durham SJ, Shah A. Adverse effects of low hematocrit during cardiopulmonary bypass in the adultshould current practice be changed?. J Thorac Cardiovascular Surg 2003;125:1438-1450.[Abstract/Free Full Text]
3. Whitaker DC, Newman SP, Stygall J, Hope-Wynne C, Harrison MJG, Walesby RK. The effect of leucocyte-depleting arterial line filters on cerebral microemboli and neuropsychological outcome following coronary artery bypass surgery Eur J Cardiothorac Surg 2004;25:267-274.[Abstract/Free Full Text]

This article has been cited by other articles:

				G. Djaiani, K. Karkouti, and W. S. Beattie Reply. Ann. Thorac. Surg., September 1, 2006; 82(3): 1166 - 1166. [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Donald C. Whitaker Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Harrison, M. J.G. Articles by Newman, S. P. Search for Related Content PubMed PubMed Citation Articles by Harrison, M. J.G. Articles by Newman, S. P. Related Collections Extracorporeal circulation Related Article