Cardiac Output and Net Volume Balance in ICU Patients

Austin—Volume management for patients in the intensive care unit (ICU) aims to optimize intravascular volume and maximize cardiac output. Following giving volume to volume-depleted patients, cardiac output tends to increase. In volume-overloaded patients with end-stage renal disease, cardiac volume tends to increase with ultrafiltration, and to decrease with ultrafiltration in patients with ESRD who are prone to intradialytic hypotension. In patients in the ICU with volume overload, volume removal with intermittent hemodialysis may increase cardiac output.

Researchers, led by Martin Aldana-Campos, MD, conducted a retrospective study to test the hypothesis that assessing relative intravascular volume using inferior vena cava (IVC) collapsibility may guide volume management during intermittent hemodialysis and/or continuous renal replacement therapy (CRRT) in patients in the ICU. Results of the study were reported during a poster session at the NKF 2018 Spring Clinical Meetings in a poster titled Cardiac Output Relates to Net Volume Balance with Intermittent or Continuous Hemodialysis and to Relative Intravascular Volume in Critical Illness.

The analysis included patients in the ICU with relative intravascular volume assessed by IVC Collapsibility Index (IVC CI)=((IVCmax-IVCmin)/IVCmax *100%) by ultrasound within 24 hours of serial cardiac output measured by thermodilution during CRRT (six patients, 20 encounters) or before and after intermittent hemodialysis/ultrafiltration (17 patients, 34 encounters).

A change in cardiac output >10% was considered significant. Net volume changes between cardiac output measurement were estimated using mean sodium concentrations of body fluid losses including ultrafiltration and of enteral/parenteral fluids administered.

In patient encounters with IVC CI <10% (relative intravascular volume overload) (n=7/20 in the intermittent hemodialysis group and 4/13 in the CRRT group), cardiac output increased >10% with net volume losses more frequently, compared with patients with IVC CI ≥10% (n=1/4 in the intermittent hemodialysis group and 0/7 in the CRRT group). There was no difference in the frequency of increased cardiac output after net volume removal with IVC CI <10% between the intermittent hemodialysis group and the CRRT group.

In conclusion, the researchers said, “Cardiac output may increase with net volume removal by intermittent hemodialysis/ultrafiltration or CRRT in ICU patients with relative intravascular volume overload assessed by IVC collapsibility.”

Source: Aldana-Campos M, Kaptein MJ, Nguyen CD, et al. Cardiac output relates to net volume balance with intermittent or continuous hemodialysis and to relative intravascular volume in critical illness. Abstract of a poster presented at the National Kidney Foundation 2018 Spring Clinical Meetings, April 10-14, 2018, Austin, Texas.