Objectives

1. Review emerging data on the influence of blood loss and resuscitation on the behavior of commonly used intravenous sedative hypnotics and opioids.

2. Discuss the rational selection and dosing of sedative hypnotics and opioids in settings of intravascular volume depletion.

SUMMARY

Anesthesiologists have long recognized the need to moderate doses of intravenous anesthetics in settings of significant blood loss. The scientific rationale for this practice, however, has not been well established. This chapter reviews recent investigations that have quantified how blood loss influences intravenous anesthetic behavior and synthesizes these findings into a set of clinical “take-home messages” targeted at improving patient safety.

INFLUENCE OF BLOOD LOSS ON INTRAVENOUS ANESTHETICS

Dr. Halford, a surgeon, wrote a letter to the editor of Anesthesiology after caring for several trauma victims after the attack on Pearl Harbor in 1941. He noticed that anesthetists had started using the intravenous (IV) anesthetic sodium pentothal. His comments were:

Anesthesiologists have recognized the need to incrementally dose these anesthetics, and to moderate the overall dose for patients who have significant blood loss before or during surgery. Through experience, they have learned that a full dose of certain IV anesthetics can lead to pronounced and often unwanted side effects with potentially disastrous consequences.