Make the Diagnosis: Fluid Responsiveness in Unstable Patients
Prior Probability of Fluid Responsiveness in Unstable Patients
In patients who remain hemodynamically unstable after the initial resuscitation, further fluid administration can create volume overload and worsen outcomes. Among those unstable patients, 50% (95% CI, 42%-56%) will respond to continued fluid administration after their initial resuscitation.
Population of Unstable Patients Among Whom Fluid Responsiveness Should Be Considered
In studies of hemodynamic instability, the most frequent criteria for entrance into the studies were hypotension, oliguria, skin mottling, tachycardia, and the physician's overall clinical impression of hypovolemia. In every patient with persistent hypoperfusion and hypotension, the clinician must decide when to stop fluid replacement and shift to other approaches, such as vasopressors or inotropes.
Assessing the Likelihood of Fluid Responsiveness Findings
None of the commonly taught physical examination findings (dry mucous membranes, dry axilla, decreased tissue turgor, capillary refill time greater than 2 seconds, tachycardia, or low jugular venous pressure) have utility since the associated likelihood ratio (LR) CIs all include 1.
Bedside physiologic measures to predict fluid responsiveness are either static tests or dynamic tests. Invasive measurement of the central venous pressure (CVP) with a central vein catheter is a bedside static test. In studies with pressure thresholds from 8 to 12 cm water, patients with lower CVP were more likely to be fluid responsive while those with higher CVP were less likely (see Table 102-1).
Table 102-1.Useful Findings for Assessing the Likelihood of Fluid Responsiveness in Hemodynamically Unstable Patients |Favorite Table|Download (.pdf) Table 102-1. Useful Findings for Assessing the Likelihood of Fluid Responsiveness in Hemodynamically Unstable Patients
|Finding ||LR+ (95% CI) ||LR– (95% CI) |
|Static Measures |
|Central venous pressure < 8-12 cm water ||2.6 (1.4-4.6) ||0.50 (0.39-0.65 |
|Dynamic Measures |
|Passive leg raise || || |
| Increase in cardiac outputa ||11 (7.6-17) ||0.13 (0.07-0.22) |
| Increase in pulse pressure ||3.6 (2.5-5.4) ||0.45 (0.36-0.57) |
|IVC variationb || || |
| During controlled ventilation (TV < 8 mL/kg) ||5.3 (1.1-27) ||0.27 (0.08-0.87) |
|Pulse pressure variationc || || |
| During controlled ventilation (TV ≥ 7 mL/kg) ||5.3 (3.5-8.1) ||0.19 (0.12-0.30) |
| During controlled ventilation (TV < 7 mL/kg) ||7.9 (4.1-16) ||0.30 (0.21-0.44) |
Dynamic tests create reversible and transient changes in preload that suggest fluid responsiveness. The most common maneuvers are passive leg raising (to as much as a 45o angle) and, in ventilated patients, ...