|
Method | Advantages | Disadvantages |
|
Respiratory changes in CVP | Most critically ill septic patients have an IJ or SC CVL |
It requires that the inspiratory effort be significant—a fall in PAWP of ≥2 mmHg was used in the original study by Magder et al. [11] |
It can be used in spontaneously breathing patients | |
|
Respiratory changes in IVC diameter | It is non-invasive and requires an ultrasound with M-mode which is now becoming widely available |
It is only reliable in mechanically ventilated patients who are receiving ≥8 mL/kg PBW tidal volume, are not making any significant respiratory efforts, and are in NSR |
It is easy to learn and teach | It may not be reliable in conditions associated with IAH, for example, obesity, massive ascites, abdominal compartment syndrome |
It can be easily repeated as often as necessary | |
|
Respiratory changes in SVC diameter | It is more accurate than respiratory change in IVC diameter |
It is semi-invasive and requires TEE and expertise in using it |
It is not continuous |
It too is only reliable in mechanically ventilated patients who are receiving ≥8 mL/kg PBW tidal volume, are not making any significant respiratory efforts, and are in NSR |
|
PPV | PPV can be calculated manually from a 30 sec printout of the arterial blood pressure waveform | It is invasive and requires an arterial line |
It is only reliable in mechanically ventilated patients who are receiving ≥8 mL/kg PBW tidal volume, are not making any significant respiratory efforts, and are in NSR |
|
SVV-FloTrac Vigileo | It does not require frequent recalibration | It is invasive and requires an arterial line |
It provides additional data: SV, CO | It is only reliable in mechanically ventilated patients who are receiving ≥8 mL/kg PBW tidal volume, are not making any significant respiratory efforts, and are in NSR |
|
SVV-PiCCO Plus | It provides additional data: SV, CO, TBV, and EVLW | It is invasive and requires an IJ or SC CVL and a femoral arterial line with a thermistor |
It requires frequent recalibration |
It is only reliable in mechanically ventilated patients who are receiving ≥8 mL/kg PBW tidal volume, are not making any significant respiratory efforts, and are in NSR |
|
PVI | It is noninvasive | It is only reliable in mechanically ventilated patients who are receiving ≥8 mL/kg PBW tidal volume, are not making any significant respiratory efforts, and are in NSR |
It is easy to use |
It is not reliable if peripheral perfusion is severely compromised |
It does not require calibration | |
|
| | Semi-invasive and requires TEE or esophageal Doppler US and expertise in using it |
| | It is only reliable in mechanically ventilated patients who are receiving ≥8 mL/kg PBW tidal volume, are not making any significant respiratory efforts, and are in NSR |
| | It suffers from additional limitations: |
Respiratory changes in aortic blood flow velocity | Esophageal Doppler US monitoring uses a smaller esophageal probe than TEE and therefore is less invasive; it can also be left in place for continuous monitoring; it also requires less training to use and is less expensive | Long learning curve with a lack of reproducibility |
| | Inability to obtain continuous reliable measurements |
| | Requirement for 24-hour availability |
| | Practical problems related to the presence of the probe in the patient’s esophagus |
| | As esophageal Doppler probes are inserted blindly, the resulting waveform is highly dependent on correct positioning |
|
Respiratory changes in brachial artery blood flow velocity | It is non-invasive and requires only a US with Doppler which is now becoming widely available in ICUs |
It is only reliable in mechanically ventilated patients who are receiving ≥8 mL/kg PBW tidal volume, are not making any significant respiratory efforts, and are in NSR |
It is easy to learn and teach as demonstrated by a study where residents used it after learning the technique | |
|
PLR maneuver | It can be used in spontaneously breathing patients |
It requires continuous CO monitoring by a technology with a rapid response time, for example, USCOM, NICOM, FloTrac Vigileo, PiCCO, or PAC with such capability |
It can be used in patients with arrhythmias |
It can be completely noninvasive if CO is measured by a noninvasive method, for example, USCOM or NICOM |
|