Possible side effects of Intralipid rescue therapy

Abstract

New details about the use of large volume Intralipid (Fresenius Kabi, Runcorn, UK) infusions continue to emerge [1]. Lipaemia causes analytical interference of blood samples by two separate mechanisms. The electrolyte exclusion effect is clinically minor, even at extremely elevated triglyceride levels [2]. Spectrophotometric interference is present at much lower triglyceride levels, and affects both biochemistry and haematology values. Haemoglobin and platelet count may be erroneously reported as elevated [3]. Pathology laboratories have a variety of methods to assist with the analysis of lipaemic samples. These include chemical methods to clear lipids, mathematical techniques to correct for differing proportions of lipid in the plasma, the use of direct ion-sensitive electrode techniques without pre-dilution of the sample and centrifugation at a higher than normal speed to increase separation of the lighter lipid layer from the serum [4]. Communication with the laboratory about the presence of lipid contamination is essential for efficient sample handling and to obtain rapid, accurate results. Blood gas machines usually use direct ion-sensitive electrode techniques giving reliable results. An additional mechanism of interference is that of lipid molecules coating and occluding the delicate membranes within the machine and interfering with both current and subsequent measurements [personal communication, Mr Christopher Neal, Product manager, Radiometer Pacific Proprietary Limited, Mt Waverley, Victoria, Australia]. A ‘turbidity detected error’ is usually flagged in this situation. Only two previously published case reports mention electrolyte levels measured after administration of Intralipid, and these were both obtained from blood gas machines [5, 6]. I have experienced two cases in which problems caused by Intralipid-associated analytical interference had potential or direct effects on patient care. In one, a 3-year-old developed a resistant supraventricular tachycardia after a local anaesthetic block and received three 1-mg.kg−1 Intralipid boluses. The cause was later determined to be a congenital conduction disorder, but at the time, the electrolyte results took over 90 min to obtain as the sample required repeated high speed centrifugation. In another case, a middle aged patient experienced sudden cardiovascular collapse towards the end of an abdominal operation. Intralipid was administered for possible local anaesthetic toxicity when she did not respond to other treatment measures. A considerable time lag in obtaining an accurate low haemoglobin result meant that the true underlying diagnosis of massive concealed retro-peritoneal haematoma was significantly delayed. Previous to Watts’ case, where the doses of Intralipid are unspecified, the largest dose reported in the literature is in a 67-kg patient who received a bolus dose of 100 ml plus an infusion of 400 ml Intralipid 20% [7]. Calculations suggest a peak plasma triglyceride level of 24.2 mmol.l−1, consistent with Watt et al.’s figures of approximately 25 and 28 mmol.l−1. Spectrophotometry would indeed not have been possible using routine techniques, but analysis, although delayed, should have been feasible using alternate methods. What is now clear is that after large doses of Intralipid, the results of blood tests may be difficult to analyse, delayed, or spuriously abnormal. If possible, all blood tests should be taken before the administration of Intralipid. While laboratories will readily identify significant lipaemia, communication about the presence of Intralipid is important.