Quantifying fluid responsiveness

Q: 48 years old male with previous history of HIV is admitted to ICU with septic shock. The ICU fellow decided to float pulmonary artery (swan-Ganz) catheter to better assess the fluid responsiveness. A predicted or good fluid responsiveness after 500 mL of intravenous fluid (IVF) is an increase in cardiac output (CO) by approximately? (select one)

A) 5 percent

B) 15 percent

C) hard to predict

Answer: C

It is a common practice in ICU to try to quantify fluid responsiveness by improvement in 'numbers' such as central venous pressure (CVP), cardiac output, Mean blood pressure (MAP), or pulmonary artery diastolic pressure (PADP). 

Although CO is expected to rise by 15 percent after a half liter of IVF, most of the parameters by numbers have very poor predictive values. Clinical exam and good clinical judgment continue to supersede any particular number including improvement in mental status, urine output, skin turgor, and mucous membrane dryness. The whole clinical picture should be read with all parameters. All quantifying numbers are highly influenced by cardiovascular, cardiac valvular, pulmonary, renal, and hepatic functions. Also, positive pressure ventilation, invasive or noninvasive may make numbers erroneous.

The objective of the question is to emphasize that clinical judgment should never be suppressed solely by the "numbers."

#hemodynamics

References:

1. Marik PE, Baram M, Vahid B. Does central venous pressure predict fluid responsiveness? A systematic review of the literature and the tale of seven mares. Chest 2008; 134:172.

2. Michard F, Teboul JL. Predicting fluid responsiveness in ICU patients: a critical analysis of the evidence. Chest 2002; 121:2000.

3. Osman D, Ridel C, Ray P, et al. Cardiac filling pressures are not appropriate to predict hemodynamic response to volume challenge. Crit Care Med 2007; 35:64.