oa Southern African Journal of Anaesthesia and Analgesia - Predicting the need for blood during cardiopulmonary bypass : research

Volume 11, Issue 1
  • ISSN : 2220-1181
  • E-ISSN: 2220-1173



&lt;I&gt;Background:&lt;/I&gt; Haematocrit (Hct) values <18%-20% during cardiopulmonary bypass (Hct&lt;sub&gt;CPB&lt;/sub&gt; ) are potentially unsafe. &lt;br&gt;&lt;I&gt;Aims:&lt;/I&gt; 1. To predict when bankedblood should be pre-issued. 2. To evaluate the sparing-effect of banked-blood by autologous blood transfusions. &lt;br&gt;&lt;I&gt;Methods:&lt;/I&gt; An equation for prediction of Hct&lt;sub&gt;CPB&lt;/sub&gt; (Hct<sub>pred</sub>), based on weight and pre-operative haemoglobin concentration was used to forecast which patients would develop Hct&lt;sub&gt;CPB&lt;/sub&gt; &lt;u&gt;&lt;&lt;/u&gt; 20%. Perioperative blood and fluid administration were recorded in 80 patients requiring CPB. Blood and fluid administration strived for Hct&lt;sub&gt;CPB&lt;/sub&gt; <u>></u>18% on CPB and 33% in the ICU. &lt;br&gt;&lt;I&gt;Results:&lt;/I&gt; Hct&lt;sub&gt;pred&lt;/sub&gt; bias and precision were 2.6% and 13.1%. A Hct&lt;sub&gt;pred&lt;/sub&gt; cut-off value of 23% reliably forecast a Hct&lt;sub&gt;CPB&lt;/sub&gt; &lt;u&gt;&lt;&lt;/u&gt; 20% (15 patients with mean Hct&lt;sub&gt;CPB&lt;/sub&gt; 16.5%). Despite a 31% false positive rate (FPR), there is emphasis on safety associated with the 23% Hct&lt;sub&gt;pred&lt;/sub&gt; cutoff-point. (100% negative predictive value; zero negative likelihood ratio). Applying the same predictive criterion to all blood transfusions performed in the OR, increased positive predictive values from 43% to 63% so that the FPR decreased to 24%. Autologous transfusion comprised 72% of transfused blood and was the only transfusion in 67% of patients. Banked-blood recipients weighed less and had lower pre-operative haemoglobin concentrations, Hct&lt;sub&gt;pred&lt;/sub&gt; and Hct&lt;sub&gt;CPB&lt;/sub&gt; . They received larger transfusions of which autologous blood formed 46%. &lt;br&gt;&lt;I&gt;Conclusions:&lt;/I&gt; 1. It is possible to predict which patients will develop potentially low Hct&lt;sub&gt;CPB&lt;/sub&gt; . 2. Autologous transfusions result in considerable reduction of banked blood usage.

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