title: A mini volume loading test for indication of preoperative dehydration in surgical patients.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  The mVLT was performed in 36 elective primary total knee arthroplasty patients. Each subject received three fluid challenges before anesthesia induction. These consisted of 5 mL/kg boluses of Ringer's acetate infused over 3-5 min 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.
  
  
  RESULTS
  Venous dilution was higher than capillary after the first fluid challenge (P=0.030), but lower than capillary after 20 min period following the last bolus (P=0.009). Arterial dilution was lower than capillary (P=0.005) after 20 min 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Clinic of Anaesthesiology and Intensive Care, Faculty of Medicine, Vilnius University, Vilnius, Lithuania. Electronic address: audrius.andrijauskas@mf.vu.lt.
authors.forename: Audrius
authors.initials: A
authors.lastname: Andrijauskas
authors.affiliation: Clinic of Anaesthesiology and Intensive Care, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Juozas
authors.initials: J
authors.lastname: Ivaškevičius
authors.affiliation: Clinic of Rheumatology, Orthopaedics Traumatology and Reconstructive Surgery, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Narūnas
authors.initials: N
authors.lastname: Porvaneckas
authors.affiliation: Institute of Physiology and Pharmacology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania.
authors.forename: Edgaras
authors.initials: E
authors.lastname: Stankevičius
authors.affiliation: Section of Anaesthesiology and Intensive Care, Department of Clinical Science and Education, Karolinska Institutet, Södersjukhuset, Stockholm, Sweden.
authors.forename: Christer H
authors.initials: CH
authors.lastname: Svensen
authors.affiliation: Clinic of Rheumatology, Orthopaedics Traumatology and Reconstructive Surgery, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Valentinas
authors.initials: V
authors.lastname: Uvarovas
authors.affiliation: Clinic of Anaesthesiology and Intensive Care, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Saulė
authors.initials: S
authors.lastname: Švedienė
authors.affiliation: Clinic of Rheumatology, Orthopaedics Traumatology and Reconstructive Surgery, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Giedrius
authors.initials: G
authors.lastname: Kvederas
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001808:Blood Vessels; D003681:Dehydration / Q000175:diagnosis*; D003955:Diagnostic Tests, Routine; D005260:Female; D005440:Fluid Therapy; D006801:Humans; D007263:Infusions, Parenteral; D007552:Isotonic Solutions / Q000008:administration & dosage; D008297:Male; D011300:Preoperative Care / Q000379:methods*
chemical_list: D007552:Isotonic Solutions; C028570:Ringer's acetate
keywords: Fluid therapy; Hydration status; Interstitial fluid expansion; Noninvasive hemoglobin measurement; Plasma dilution