In the hypovolaemic patient

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In the hypovolaemic patient:

• fluid replacement is best achieved through the rapid infusion of repeated small volumes (250 ml of crystalloid or colloid) and close monitoring using a CVP line and urinary tract catheter (if clinically indicated, as its use is associated with an increased risk of infection )
• lactate and base excess measurements may also be helpful in conjunction with clinical judgment in assessing response to volume loading
• a decreasing urine output is a sensitive indicator of AKI and oliguric AKI is associated with a poorer prognosis
  • documentation of urine volume is part of fluid balance management in any acutely ill patient. However there are a number of caveats to consider
  • urine volume may not be diagnostic
    • particularly when diuretics have already been administered
    • also part of the usual stress response to surgery is an increased secretion of antidiuretic hormone (ADH) and an upregulation of the renin-angiotensin-aldosterone system resulting in avid salt and water retention
      • as a consequence there is decreased urine output and free water clearance in the first 12-24 hours following surgery

Reference

1. Gluw R et al. Fluid balance concepts in medicine: Principles and practice. World J Nephrol. 2018 Jan 6;7(1):1-28.