Fluids and Vasopressors in Critical Care Nephrology
Kathleen Liu, MD (UCSF)
Dr. Liu started off her presentation with a review of what we’ve learned regarding shock. Surprising to many in the audience, Dr. Liu debunked a lot of the myths surrounding septic shock management. For example, the NICE-SUGAR trial put to rest the idea of intense glycemic control as beneficial to septic shock patients. The CORTICUS trial left open the question of whether glucocorticoid therapy has any role in septic shock management. The PROWESS trial, which actually confirmed the use of activated protein C in septic shock patients (a.k.a. Xigris) was debunked by ADDRESS, ENHANCE, RESOLVE and finally PROWESS-SHOCK. The latter trial showed that use of activated protein C did not change 28-day mortality versus placebo (26.4% v. 24.2%, p 0.31). About the only therapy that remains useful is early antibiotic administration (early in the onset of hypotension).
Dr. Liu then turned her attention to fluids. The SAFE trial debunked the notion that colloids (like albumin) are effective resuscitative fluids – no benefit in mortality (Note – try telling that to your local surgeon!). A trial in NEJM 2008 disproved any benefit of hetastarch in mortality, and showed a higher risk of developing AKI! The mechanism for this is thought to be osmotic damage to the tubules. Crystalloids like normal saline remain the resuscitative fluid of choice (she didn’t mention lactated ringers, though I would presume she would be fine with LR as well).
How do you measure volume status? If you’re like most physicians, you typically use central venous pressure (CVP), but new data shows that its ability to accurately predict volume changes is limited (ROC AUC 0.55). In fact, you could have 10-12% volume loss before you see a change in the CVP. More sophisticated measurements of volume include systolic pressure variation (ROC AUC 0.86) or the pulse pressure variation (ROC AUC 0.9). Unfortunately Dr. Liu did not go into greater detail about these measurements but I think they’re definitely worth learning about.
Finally, a brief sentence or two regarding vasopressor selection. The VASST data showed no difference in survival when you choose either norepinephrine or vasopressin as your first line vasopressor in septic shock patients. SOAP II, however, did show that in cardiogenic shock, norepinephrine is better than dopamine, perhaps because the latter was associated with greater incidence of arrhythmias. This trial also showed no difference between norepi and dopamine in non-cardiogenic shock (hypovolemia refractory to resuscitation or septic shock).
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