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Retrospective investigation on the effectiveness of weight based mannitol administration on kidney function during cardiopulmonary bypass : a thesis submitted to the faculty of the Milwaukee School of Engineering in partial fulfillment of the requirements for the degree of Master of Science in Perfusion / by Jessica Larson.

by Larson, Jessica., Milwaukee School of Engineering

Cardiopulmonary bypass -- Adverse effects

Acute renal failure -- Prevention

48 leaves : illustrations, some of which are in color ; 29 cm.

Introduction -- Background -- Methods -- Results -- Discussion -- Conclusion -- References.

Mannitol is a diuretic compound that has been proposed to help minimize renal dysfunction during surgeries utilizing cardiopulmonary bypass (CPB). There is, however, debate within the perfusion community over the level of efficacy of mannitol, and how it should be dosed in order to achieve perceived benefits. Literature comparing dosing strategies with renal function outcomes is limited and conclusions are inconsistent in determining effectiveness of varying doses and times of administration. To date, there have been no published studies that have investigated the most effective weight base dosing strategy of mannitol. The goals of this retrospective study were to 1) determine if a standard dose of mannitol (25 g) in the pump prime differentially affected renal function in patients of varying weights, and 2) determine if the use of a 25 g pump prime dose plus repeated doses of 12.5 g/hr were more effective in preventing renal dysfunction.

Data were collected from cardiac surgery patients placed on cardiopulmonary bypass between November 30th, 2011 and August 31st, 2013. Data were retrieved from Aurora St. Luke's Medical Center's Epic database, the Society of Thoracic Surgeons (STS) Database, and LUMEDX perfusion databases. The patient group was limited to those with normal pre-surgical renal function, common surgeries, and under 80 years of age. The ratio of post-operative to preoperative serum creatinine was used as the indicator of renal dysfunction. Patient groups were also analyzed for confounding variables including gender, age, laboratory values, cardiopulmonary bypass and aortic cross-clamp times, and type of procedure performed.

First, patients receiving only the standard dose of mannitol in the pump prime (25 g) were isolated (N=137 patients) and then divided into two groups, mimicking a weight based dosing strategy, where those patients in the lowest weight group had the highest weight based dose using a standard pump prime of mannitol. Statistical analysis was performed utilizing a one-way ANOVA. Secondly, the effects of repeated administration of 12.5 g/hr of mannitol (N=517) were analyzed utilizing multiple regression, and one-way ANOVA followed by Tukey comparison testing. In order to determine which dosing strategy was more effective, standard pump prime or repeated dosing, a one-way ANOVA was performed across strategies and weight classification. Urine output testing was also performed with correlation and one-way ANOVA testing.

Results showed that when administering 25 g of mannitol in the pump prime only, patients receiving >0.25 g/kg had lower serum creatinine ratio mean (1.03 ± 0.18) when compared to those receiving <0.25 g/kg (1.22 ± 0.44) (p>0.01). Hourly weight based dosing was a significant predictor of serum creatinine ratio (p>0.05) and a preliminary result found >0.45 g/kg/hr resulted in the lowest serum creatinine ratio (1.05 ± 0.25). As expected, urine output was significantly correlated to overall doses of mannitol (r=0.410, p<0.001).

This study demonstrated that weight based mannitol may be more effective than standard dosing but further study is required to determine the most effective dosing strategy in order to prevent renal dysfunction postoperatively in cardiac patients.

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