title: A mini volume loading test (mVLT) using 2.5-mLkg-1boluses of crystalloid for indication of perioperative changes in hydration status.
abstract: OBJECTIVE
  A mini volume loading test (mVLT) evaluating hemodilution during step-wise crystalloid infusion has established that the arterio-capillary plasma dilution difference is inversely correlated to the body hydration level of subjects. This observational study aimed to test whether this can be replicated in a perioperative setting using a 2.5-mLkg-1boluses.
  
  
  METHODS
  The mVLT was performed before induction of regional anesthesia and 24h later. Step-wise infusion implied six mini fluid challenges. These consisted of 2.5-mLkg-1boluses of Ringer's acetate infused during 2-3min and followed by 5-min periods with no fluids. Invasive (arterial) and noninvasive (capillary) measurements of hemoglobin were performed before and after each mini fluid challenge, as well as after a 20-min period without fluid following the last bolus. Hemoglobins were used to calculate the arterio-capillary plasma dilution difference which is used as an indication of changes in body hydration level. The 24-h fluid balance was calculated.
  
  
  RESULTS
  Subjects were 69.5 (6.0) years old, their height was 1.62m (1.56-1.65), weight was 87.0kg (75.5-97.5) and body mass index (BMI) was 33.5kg/m2(31.0-35.1). Preoperative arterio-capillary plasma dilution difference was significantly higher than postoperative (0.085 [0.012-0.141] vs. 0.006 [-0.059 to 0.101], P=0.000). The perioperative 24-h fluid balance was 1976mL (870-2545).
  
  
  CONCLUSIONS
  The mVLT using 2.5-mLkg-1boluses of crystalloid was able to detect the higher postoperative body hydration level in total knee arthroplasty patients.
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: Section of Anaesthesiology and Intensive Care, Department of Clinical Science and Education, Karolinska Institutet, 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: Narūnas
authors.initials: N
authors.lastname: Porvaneckas
authors.affiliation: Clinic of Anaesthesiology and Intensive Care, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Jūratė
authors.initials: J
authors.lastname: Šipylaitė
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: Clinic of Anaesthesiology and Intensive Care, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Darius
authors.initials: D
authors.lastname: Činčikas
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: Igoris
authors.initials: I
authors.lastname: Šatkauskas
authors.affiliation: Clinic of Anaesthesiology and Intensive Care, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Saulius
authors.initials: S
authors.lastname: Vosylius
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; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077324:Crystalloid Solutions; D003681:Dehydration / Q000097:blood / Q000175:diagnosis / Q000628:therapy / Q000652:urine; D004311:Double-Blind Method; D005440:Fluid Therapy / Q000379:methods; D006454:Hemoglobins / Q000032:analysis; D007263:Infusions, Parenteral; D007552:Isotonic Solutions / Q000008:administration & dosage; D010477:Perfusion; D019990:Perioperative Care / Q000379:methods; D010949:Plasma / Q000737:chemistry; D015532:Rehydration Solutions / Q000008:administration & dosage; D018709:Statistics, Nonparametric; D013997:Time Factors; D059349:Urine Specimen Collection; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D000077324:Crystalloid Solutions; D006454:Hemoglobins; D007552:Isotonic Solutions; D015532:Rehydration Solutions; C028570:Ringer's acetate
keywords: Hydration level; Mini volume loading test; Noninvasive hemoglobin; Perioperative fluid balance; Stroke volume