The Influence of Hemorrhagic Shock on the Disposition and Effects of Intravenous Anesthetics: A Narrative Review.

The need to reduce the dose of intravenous anesthetic in the setting of hemorrhagic shock is a well-established clinical dogma. Considered collectively,; the body of information concerning the behavior of intravenous anesthetics during hemorrhagic shock, drawn from animal and human data, confirms that clinical dogma and informs the rational selection and administration of intravenous anesthetics in the setting of hemorrhagic shock. The physiologic changes during hemorrhagic shock can alter pharmacokinetics and pharmacodynamics of intravenous anesthetics. Decreased size of the central compartment and central clearance caused by shock physiology lead to an altered dose-concentration relationship. For most agents and adjuncts, shock leads to substantially higher concentrations and increased effect. The notable exception is etomidate, which has relatively unchanged pharmacokinetics during shock. Increased concentrations lead to increased primary effect as well as increased side effects, notably cardiovascular effects. Pharmacokinetic changes are essentially reversed for all agents by fluid resuscitation. Propofol is unique among agents in that, in addition to the pharmacokinetic changes, it exhibits increased potency during shock. The pharmacodynamic changes of propofol persist despite fluid resuscitation. The persistence of these pharmacodynamic changes during shock is unlikely to be due to increased endogenous opiates, but is most likely due to increased fraction of unbound propofol. The stage of shock also appears to influence the pharmacologic changes. The changes are more rapid and pronounced as shock physiology progresses to the uncompensated stage. Although scant, human data corroborate the findings of animal studies. Both the animal and human data inform the rational selection and administration of intravenous anesthetics in the setting of hemorrhagic shock. The well-entrenched clinical dogma that etomidate is a preferred induction agent in patients experiencing hemorrhagic shock is firmly supported by the evidence. Propofol is a poor choice for induction or maintenance of anesthesia in severely bleeding patients, even with resuscitation; this can include emergent trauma cases or scheduled cases that routinely have mild or moderate blood loss.

Unanticipated critical findings on echocardiography in septic patients.

BACKGROUND: Echocardiography is increasingly performed among septic patients as a routine part of evaluation and management in the intensive care unit (ICU). The rate of unanticipated critical findings (e.g., severe left or right ventricular dysfunction or pericardial tamponade) on such echocardiograms is unknown. We evaluated a retrospective cohort of septic ICU patients in whom transthoracic echocardiography was performed as a routine part of sepsis management. In addition to identifying critical findings, we defined whether each critical finding was anticipated, and whether the clinical team responded to the critical finding. The primary outcome was rate of unanticipated critical findings, which we hypothesized would occur in fewer than 5% of patients. We also performed an exploratory analysis of the association between unanticipated critical finding and mortality, controlling for severity of illness. RESULTS: We studied 393 patients. Unanticipated critical findings were identified in 5% (95% CI 3-7%) of patients (n = 20). Among the 20 patients with unanticipated critical findings, a response to the unanticipated critical finding was identified in 12 (60%) patients. An unanticipated critical finding was not significantly associated with 28-day mortality when controlling for admission APACHE II (p = 0.27). CONCLUSIONS: Unanticipated critical findings on echocardiograms in septic ICU patients are uncommon. The potential therapeutic relevance of echocardiography to sepsis is more likely related to hemodynamic management than to traditional cardiac diagnoses. Research studies that employ blinded echocardiograms in septic patients may anticipate unblinding for critical findings approximately 1 in every 20 echocardiograms.