Background Recently, Gong et al. (Gong et al. 2022) showed, in nine heathy subjects, that plasma clearance of high doses of iohexol given as contrast enhanced computed tomography (CT) could be used for determination of glomerular filtration rate (GFR). We utilized high doses of iohexol from angiographic or other contrast enhanced CT given to critical ill patients for calculation of GFR_iohexol and compared these data with standard low dose iohexol GFR determinations.

Method Patients at intensive care units (ICUs) in Southeast Sweden intended for radiographic investigations that included injection of 45-120 ml of iohexol (Omnipaque) were included, and the concentration of iohexol in plasma was measured by HPLC. Iohexol clearance was calculated by the method of Bröchner-Mortensen. The following days was iohexol clearance determined using the standard low dose of 5 mL of iohexol. Sixteen patients admitted to ICUs were included in this pilot study.

Results GFR after high dosing of iohexol at contrast enhanced CT could be measured for all sixteen critically ill patients. Patients with normal or increased renal function had neglectable iohexol concentrations the day following the CT scan. There was excellent correlation between GFR determination with high and standard low iohexol dosing among these 6 patients. Ten patients had decreased renal function and delayed elimination of iohexol, thus was not GFR measurement with low dose iohexol possible to analyse the day after CT scan with high dose iohexol.

Conclusion This pilot study showed that GFR can be measured after high doses of iohexol at enhanced CT and compare well with the standard low dose of iohexol clearance determinations.