O17 Prevalence and severity of hypomagnesaemia after liver transplantation

<h3></h3> Tacrolimus (FK506), a calcineurin inhibitor, is the mainstay of immunosuppression regimens post-liver transplantation. FK506 treatment is reportedly associated with hypomagnesaemia by increasing fractional excretion of Mg2+ by the kidneys through inhibition of resorption pathways. In light of a recent patient safety alert regarding the death related to hypomagnesaemia in a renal transplant patient taking tacrolimus (1), we performed a retrospective cohort study in liver transplant patients. This study comprised all adult patients who underwent a first liver transplantation at Queen Elizabeth Hospital Birmingham (QEHB) between 2014 and 2018. Hypomagnesaemia was defined as a serum magnesium level less than 0.7 mmol/L, with moderate and severe hypomagnesaemia defined as less than 0.5 mmol/L and 0.4 mmol/L, respectively. Clinical records and correspondence were reviewed to identify the lowest serum magnesium levels recorded. Serum magnesium values taken within 3 months of transplant were excluded. Cases of severe hypomagnesaemia were reviewed in detail to investigate patient settings (inpatient vs. outpatient), risk factors and outcomes. The present study comprised 852 patients with a mean age of 52.7 years. The predominant aetiologies were alcohol-related liver disease (28.1%), HCC (17.0%) and PSC (13.4%). The prevalence of chronic kidney disease (eGFR &lt; 60ml/min) was 10.6%. Patients that died (n = 40) or were lost to follow-up (n = 1) within three months of transplant were excluded. Of the 573 (66.5%) patients with at least one serum magnesium measurement, 343 (58.8%) had mild hypomagnesaemia, 43 (5.8%) had moderate hypomagnesaemia, and 12 (2.1%) patients had severe hypomagnesemia based on the lowest recorded serum magnesium level. Cases of severe hypomagnesaemia were typically associated with diarrhoea, AKI or sepsis and were observed in intensive treatment unit, inpatient and outpatient settings. There were no documented severe complications of hypomagnesaemia i.e., arrythmias, seizures or death. Severe hypomagnesaemia was most likely to occur within the first year following transplantation; however, hypomagnesaemia was observed up to 10 years after transplantation. Serum tacrolimus levels were very weakly negatively correlated with serum magnesium levels (R2 = 0.05, P &lt; 0.01). Our findings demonstrate hypomagnesaemia is common following liver transplantation with an incidence of 66.5% over a mean follow-up of 6.7 (±2.6) years. Despite the absence of severe adverse events related to hypomagnesaemia in this cohort, our findings indicate magnesium levels should be monitored regularly in all patients receiving tacrolimus following liver transplantation.