Fetal surgery is an evolving field. Some previously fatal diseases can be surgically corrected before birth. Animal models of the procedures have been carefully translated to humans, but less is known about anesthetic techniques. In children, inadequate anesthesia results in greater stress responses as shown by cardiovascular, neuro-endocrine, and metabolic changes. These stress responses have been associated with poorer outcomes. One of the major goals of anesthesia for these procedures is to attenuate this stress response. Fetuses get intramuscular opioids before their incision, and the mother is given high doses of volatile anesthetic (desflurane) with the assumption that whatever amount of desflurane crosses the placenta adequately anesthetizes the fetus. No studies have quantified the fetal levels of desflurane.~High pressure liquid chromatography (HPLC) has been used to measure levels of volatile anesthetic in various tissues. Measurement of desflurane has been challenging because of its higher boiling point (23.5 °C at one atmosphere pressure) when compared to older volatile anesthetics such as sevoflurane (boiling point 58.6 °C) and isoflurane (boiling point 48.5 °C). With techniques in cold rooms and using ice for sample transport, investigators have successfully measured desflurane levels in blood and brain tissue of mice.~Our eventual goal is to quantify fetal levels of desflurane in umbilical cord blood during fetal surgery, but we first propose a pilot study to assess and refine the ability of our assay to measure desflurane in human blood.
In this feasibility study we will collect blood from indwelling arterial catheters in up to 20 patients undergoing non-emergent surgery with desflurane anesthesia at Children's Hospital of Philadelphia. Desflurane levels will be determined by high pressure liquid chromatography (HPLC).~Our eventual goal is to quantify fetal levels of desflurane in umbilical cord blood during fetal surgery. We propose a pilot study to assess the ability of our assay to measure desflurane in human blood.