Review Article

Optimization of Preload in Severe Sepsis and Septic Shock

Table 4

Advantages and disadvantages of the various dynamic parameters used to predict preload responsiveness.

MethodAdvantagesDisadvantages

Respiratory changes in CVPMost 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 diameterIt 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 teachIt 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 diameterIt 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

PPVPPV can be calculated manually from a 30 sec printout of the arterial blood pressure waveformIt 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 VigileoIt does not require frequent recalibrationIt is invasive and requires an arterial line
It provides additional data: SV, COIt 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 PlusIt provides additional data: SV, CO, TBV, and EVLWIt 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

PVIIt is noninvasiveIt 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 velocityEsophageal 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 expensiveLong 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 velocityIt 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 maneuverIt 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

CVP: central venous pressure, IJ: internal jugular, SC: subclavian, CVL: central venous line, PAWP: pulmonary artery wedge pressure, IVC: inferior vena cava, PBW: predicted body weight, NSR: normal sinus rhythm, IAH: intra-abdominal hypertension, SVC: superior vena cava, TEE: transesophageal echocardiography, PPV: pulse pressure variation, SVV: stroke volume variation, SV: stroke volume, CO: cardiac output, TBV: thoracic blood volume, EVLW: extravascular lung water, US: ultrasound, USCOM: ultrasonic cardiac output monitor, NICOM: noninvasive cardiac output monitor.