Therapeutic goals of fluid resuscitation

Optimizing tissue perfusion by administering intravenous fluids presents a special challenge to the intensive care unit (ICU) clinician. Recent studies have drastically altered how we assess a patient’s fluid responsiveness, particularly with regard to upstream surrogates of tissue perfusion. Central venous pressure and pulmonary capillary wedge pressure have been found to be inaccurate markers of fluid responsiveness and have given way to methods such as cardiac output as assessed by echocardiography and the various forms of arterial waveform analysis. These newer techniques, such as stroke volume variation, systolic pressure variation, and pulse pressure variation, have been found to better delineate which patients will respond to a fluid challenge with an increase in cardiac output, and which will not. In addition, traditional methods of assessing the consequences of excessive fluid administration, such as pulmonary oedema and the non-anion gap acidosis of saline administration, have given way to more sophisticated measurements of extravascular lung water, now available at the bedside. Downstream markers of tissue perfusion, such as base deficit, central venous oxygen saturations, and lactic acid, continue to be useful in particular clinical settings, but are all relatively non-specific markers, and are therefore difficult to use as resuscitation targets for ICU patients in general. Finally, recent data on septic shock and ARDS have demonstrated the importance of conservative fluid strategies, while data in surgical populations have emphasized the need for judicious fluid administration and attention to the balance of blood products used in resuscitation efforts.