title: The effect of gain in total body water on haemoglobin concentration and body weight following cardiac surgery.
abstract: BACKGROUND
  Haemodilution contributes to a low post-operative haemoglobin concentration in cardiac surgery patients. An assessment of the degree of haemodilution could contribute to the avoidance of red cell transfusion when such an act is based simply on a haemoglobin "transfusion trigger". We have recorded post-operative change in total body water along with body weight to assess the impact of haemodilution on haemoglobin concentration.
  
  
  METHODS
  Total body water, measured by bio-electrical impedance analysis, haemoglobin and body weight were measured pre-operatively and on the 1st, 3rd, 5th and 10th post-operative days. The percentage peri-operative change in all three variables was used to examine the paired associations.
  
  
  RESULTS
  Total body water and body weight underwent a fall from day 1, with both variables significantly associated up until day 10. Haemoglobin rose steadily from day 1 to 10. This rise was associated with falling total body water and body weight until day 5, but not from day 5 to 10.
  
  
  CONCLUSIONS
  Following cardiac surgery, an individual's fluid state should be considered in determining a patient's need for red cell transfusion. Monitoring body weight provides a simple estimate. Such an approach may reduce the incidence of unnecessary, and potentially counterproductive, transfusion in cardiac surgery patients.
authors.affiliation: Department of Cardiothoracic Surgery, Royal Infirmary of Edinburgh, Little France Crescent, Old Dalkeith Road, Edinburgh, Scotland EH16 4SU, United Kingdom. rdslight@gmail.com
authors.forename: Robert D
authors.initials: RD
authors.lastname: Slight
authors.forename: Nestor
authors.initials: N
authors.lastname: Demosthenous
authors.forename: Onyekwelu C
authors.initials: OC
authors.lastname: Nzewi
authors.forename: Ahmed R
authors.initials: AR
authors.lastname: Soliman
authors.forename: D Brian L
authors.initials: DB
authors.lastname: McClelland
authors.forename: Pankaj S
authors.initials: PS
authors.lastname: Mankad
mesh_terms: D001834:Body Water / Q000378:metabolism*; D001835:Body Weight / Q000502:physiology*; D006348:Cardiac Surgical Procedures; D000075202:Contraindications; D017097:Electric Impedance; D017707:Erythrocyte Transfusion; D005260:Female; D006438:Hemodilution; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D006454:Hemoglobins