title: Insensible water loss from the Hilite 2400LT oxygenator: an in vitro study.
abstract: BACKGROUND
  Neonatal extracorporeal membrane oxygenation (ECMO) patients are particularly vulnerable to the effects of uncompensated insensible water loss resulting in hypernatraemia. There exists a long-standing relationship between hypernatraemia and varying degrees of cerebral dysfunction. The aim of this study is to explore the degree to which free water loss occurs across a commonly used ECMO oxygenator, the polymethylpentene (PMP) membrane Hilite 2400LT (Medos, Medizintechnik AG, Stolberg, Germany). The secondary aim is to assess to what extent the addition of heat and/or humidity ameliorates this water loss.
  
  
  METHODS
  An ECMO circuit consisting of a centrifugal pump and a Hilite 2400LT oxygenator was primed with crystalloid and albumin. Each experimental trial was carried out in triplicate, with gas flow rates of 1, 3 and 4.8 L/min being investigated. Fluid loss was assessed at six time points over a 24-hour period.
  
  
  RESULTS
  Water loss increased significantly from 1 to 3 L/min gas flow (p=0.05) and from 3 to 4.8 L/min gas flow (p=0.025). The mean water loss differences between the differing gas flow trials per L/min gas flow were non-significant (72.4 ±3.9 ml/24 hrs). The effect of heating the gas to 37 °C did not significantly alter water loss, whereas heat and humidity reduced water loss significantly (p=0.009).
  
  
  CONCLUSIONS
  Insensible water loss from a Hilite 2400LT oxygenator is approximately 72 ml/day per L/min gas flow over 24 hrs. Heating and humidifying the gas reduces the fluid loss significantly to approximately 8 ml/L/min gas flow over 24 hrs (p=0.009).
authors.affiliation: Perfusion Department, Heart Centre for Children, Sydney, Australia. khedlund@haysmed.com
authors.forename: Mc
authors.initials: M
authors.lastname: Gill
authors.forename: K
authors.initials: K
authors.lastname: O'Shaughnessy
mesh_terms: D015199:Extracorporeal Membrane Oxygenation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D006955:Hypernatremia / Q000097:blood / Q000209:etiology / Q000628:therapy; D008567:Membranes, Artificial; D014867:Water
chemical_list: D008567:Membranes, Artificial; D014867:Water