Fluid Management


Central Venous Catheter


  • Sits in subclavian or internal jugular with tip directed towards SVC.
  • Measures RAP RVEDP = RV preload and thought to parallel LAP and thus LV preload.
  • Inaccurate in ptatients with pulmonary HTN, Right heart disease, valvular pathologies, pulmonary edema, PEEP (↑ intrathoracic pressure during expiration ↑ CVP)
  • Also used to infuse inotropes or vasopressors

Causes of Preoperative Volume Loss

  • Vomiting
  • Diarrhea
  • Fever
  • Sepsis
  • Trauma
  • Fluid shifts (e.g. burns, ascites, pleural effusion)

Intraoperative Volume Assessment

Not very reliable:

  • HR and BP (control for PPV and anesthetics may cause relative hypovolemia)
  • Pulse Oximetry (waveform wanters from baseline)
  • Urine Output (stress response from surgery increases ADH so not reliable measure).
  • Serial ABGs to check lactate.

Reliable in the absence of heart pathology

  • Central Venous Catheter (for CVP).

Very reliable:

  • Pulmonary artery catheter: Most commonly used for in RV dysfunction, pulmonary hypertension, valvular pathology (AS, MR), LV dysfunction.
  • Transesophageal Echocardiogram: Commonly used in major cardiac surgeries and liver transplants.

Intraoperative Fluid Requirements

Maintenance: Generally 4-2-1 rule used. 4ml/hr/kg for first 10 kg, 2 ml/hr/kg for next 10 kg, 1 ml/hr/kg for each additional kg.

Compensation for pre-existing fluid defecits: Multiply maintenance requirements by the number of hours NPO. Give 1/2 of additional fluids in the first hour, 1/4 in the 2nd hour, and 1/4 in the 3rd hour.


For a 70 kg man, the total fluid requirements are 4 x 10 kg + 2 x 10 kg + 1 x 50 kg = 110 ml/hr.

If the man has been NPO for 8 hours, he needs an additional 880 ml (for a total of 990 ml). 440 ml (on top of the maintenance 110 ml) will be given in the first hour of the surgery. 220 ml (+110 ml maintenance) will be given in each of the next two hours).

Types of Fluid

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