A mini volume loading test for indication of preoperative dehydration in surgical patients.
Previously, a mini volume loading test (mVLT) detected signs of dehydration in healthy volunteers after an overnight fast. Our objective was to investigate whether mVLT could indicate preoperative dehydration in patients after an overnight fast. The mVLT was performed in 36 elective primary total knee arthroplasty patients. Each subject received three fluid challenges before anesthesia induction. These consisted of 5mL/kg boluses of Ringer’s acetate infused over 3-5min and followed by a 5-min period without fluids. Invasive (arterial, venous) and noninvasive (capillary) measurements of hemoglobin concentration were performed before and after each fluid challenge, as well as after a 20-min period without fluids which followed the last bolus. Arterial, venous and capillary plasma dilutions were calculated in every data point. Dilution values were used to calculate the plasma dilution efficacy of each fluid challenge. Venous dilution was higher than capillary after the first fluid challenge (P=0.030), but lower than capillary after 20min period following the last bolus (P=0.009). Arterial dilution was lower than capillary (P=0.005) after 20min following the last bolus. Veno-capillary and arterio-capillary plasma dilution efficacy differences decreased (P=0.004 and P=0.033, respectively) from positive to negative during mVLT. These are signs of re-hydration from pre-existing dehydration according to a transcapillary reflux model. Signs of dehydration were observed during mVLT in patients after pre-operative overnight fast. A revised transcapillary reflux model was proposed to explain the results.
Correspondence to A. Andrijauskas Clinic of Anaesthesiology and Intensive Care, Faculty of Medicine, Vilnius University, Šiltnamių 2, 04130 Vilnius, Lithuania. E-mail address: firstname.lastname@example.org
Received 14 October 2014, accepted 27 February 2015, available online 18 March 2015.