Collagen-induced whole blood platelet aggregation in patients undergoing surgical procedures associated with minimal to moderate blood loss.

Intraoperative bleeding due to platelet disorders is a persistent problem. Therefore, a screening assay to identify patients who are likely to bleed as a result of platelet dysfunction would be useful in formulating decisions about patient care. A previous study indicated that preoperative collagen-induced whole blood platelet aggregation predicts bleeding in patients undergoing surgery with cardiopulmonary bypass, a procedure associated with substantial blood loss. In the current study, we assessed the ability of the same whole blood platelet aggregation test to predict blood loss in patients undergoing surgical procedures not associated with substantial blood loss. The study included 369 adult patients (165 men and 204 women). Patients were categorized in three groups depending on the invasiveness of the operation and the expected blood loss. The intraoperative estimated blood loss value, obtained from the operative report in the patient record, increased significantly with increasing surgical invasiveness. Patients with excessive blood loss (defined as blood loss at or above the 75th or 90th percentile of the estimated blood loss values of patients undergoing procedures of similar invasiveness) had similar platelet aggregation values as patients who did not experience excessive blood loss. Thus, for patients undergoing operations not associated with substantial blood loss, the results of preoperative collagen-induced whole blood platelet aggregation are not effective in identifying patients likely to experience excessive blood loss.

Purification of fatty acid ethyl esters by solid-phase extraction and high-performance liquid chromatography.

We have developed a two-step method to purify fatty acid ethyl esters (FAEE) using solid-phase extraction (SPE), with a recovery of 70 +/- 3% (mean +/- S.E.M.) as assessed using ethyl oleate as a recovery marker from a standard lipid mixture in hexane. The first step of the SPE procedure involves application of a lipid mixture to an aminopropyl-silica column with simultaneous elution of FAEE and cholesteryl esters from the column with hexane. Gas chromatographic analysis of FAEE without interference from cholesteryl esters may be performed using the eluate from the aminopropyl-silica column, thus eliminating the need for an octadecylsilyl (ODS) column in this case. The FAEE can then be separated from the cholesteryl esters, if necessary, by chromatography on an ODS column and elution with isopropanol-water (5:1, v/v). Both the aminopropyl-silica and ODS columns were found to be effective for up to four uses. To permit isolation of specific FAEE species following isolation of total FAEE by the two-step SPE method, we have also developed a purification scheme for individual FAEE by high-performance liquid chromatography (HPLC). Thus, this simple method allows for reproducible isolation of total FAEE by SPE and isolation of individual FAEE species by HPLC.