title: Reference values for Lactate Pro 2™ in fetal blood sampling during labor: a cross-sectional study.
abstract: OBJECTIVE
  Lactate Pro™ (LP1) is the only lactate meter evaluated for fetal scalp blood sampling (FBS) in intrapartum use. The reference values for this meter are: normal value <4.2 mmol/L, preacidemia 4.2-4.8 mmol/L, and acidemia >4.8 mmol/L. The production of this meter has been discontinued. An updated version, Lactate Pro 2TM (LP2), has been launched and is shown to be differently calibrated. The aims of the study were to retrieve a conversion equation to convert lactate values in FBS measured with LP2 to an estimated value if using LP1 and to define reference values for clinical management when using LP2.
  
  
  METHODS
  A cross-sectional study was conducted at a university hospital in Sweden. A total of 113 laboring women with fetal heart rate abnormalities on cardiotocography (CTG) had FBS carried out. Lactate concentration was measured bedside with both LP1 and LP2 from the same blood sample capillary. A linear regression model was constructed to retrieve a conversion equation to convert LP2 values to LP1 values.
  
  
  RESULTS
  LP2 measured higher values than LP1 in all analyses. We found that 4.2 mmol/L with LP1 corresponded to 6.4 mmol/L with LP2. Likewise, 4.8 mmol/L with LP1 corresponded to 7.3 mmol/L with LP2. The correlation between the analyses was excellent (Spearman's rank correlation, r=0.97).
  
  
  CONCLUSIONS
  We recommend the following guidelines when interpreting lactate concentration in FBS with LP2: <6.4 mmol/L to be interpreted as normal, 6.4-7.3 mmol/L as preacidemia indicating a follow-up FBS within 20-30 min, and >7.3 mmol/L as acidemia indicating intervention.
authors.affiliation: Department of Obstetrics and Gynecology, Karolinska University Hospital, Stockholm.
authors.forename: Brynhildur Tinna
authors.identifier: http://orcid.org/0000-0001-9439-3084
authors.initials: BT
authors.lastname: Birgisdottir
authors.affiliation: Department of Obstetrics and Gynecology, Karolinska University Hospital, Stockholm.
authors.forename: Malin
authors.identifier: http://orcid.org/0000-0002-2640-0753
authors.initials: M
authors.lastname: Holzmann
authors.affiliation: Department of Obstetrics and Gynecology, Karolinska University Hospital, Stockholm.
authors.forename: Ingela Hulthén
authors.initials: IH
authors.lastname: Varli
authors.affiliation: Department of Obstetrics and Gynecology, Karolinska University Hospital, Stockholm.
authors.forename: Sofie
authors.initials: S
authors.lastname: Graner
authors.affiliation: Department of Obstetrics and Gynecology, Karolinska University Hospital, Stockholm.
authors.forename: Sissel
authors.initials: S
authors.lastname: Saltvedt
authors.affiliation: Department of Obstetrics and Gynecology, Karolinska University Hospital, Stockholm.
authors.forename: Lennart
authors.identifier: http://orcid.org/0000-0002-7547-2569
authors.initials: L
authors.lastname: Nordström
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D005323:Fetal Monitoring / Q000295:instrumentation / Q000706:statistics & numerical data; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007743:Labor, Obstetric / Q000097:blood*; D019344:Lactic Acid / Q000097:blood*; D019095:Point-of-Care Systems; D011247:Pregnancy; D012016:Reference Values; D012535:Scalp / Q000098:blood supply; D013548:Sweden
chemical_list: D019344:Lactic Acid
keywords: Fetal blood; fetal hypoxia; fetal monitoring; lactic acid; point-of-care systems; reference values