Journal: J Neurosurg Anesthesiol 19(4):268-272, 2007. 11 References
Reprint: Dept of Anesthesia and Critical Care, Jackson 4390, Massachusetts General Hospital, 565 Fruit Street, Boston, MA 02114 (RA Peterfreund, MD, PhD)
Faculty Disclosure: Abstracted by L. Easley, who has nothing to disclose.
Awareness during general anesthesia has become a subject of considerable concern for patients, their families, and anesthesia providers. Often the cause of a particular awareness event cannot be definitely determined from retrospective reviews of handwritten records, examinations of equipment, or interviews with clinicians. The authors reviewed the Anesthesia Information Management System (AIMS) records of 3 patients' anesthetics during which intraoperative awareness probably occurred, to identify potential causes of the awareness events. The reports of recall were evaluated by a departmental committee and judged to represent instances of awareness during general anesthesia. Reviews of anesthesia records focused on comparing the doses of IV drugs and the vaporizer and flowmeter settings for inhalation agents entered by the clinician with inspired or expired gas concentrations as automatically recorded by the AIMS.
The details of the reported awareness events were temporally correlated with the administration of IV drugs, hemodynamic data, and inspired or expired concentrations of anesthetic gases in an effort to determine if low concentrations were contributing factors. In Case 1, a 24-yr-old man received a diagnosis of an Arnold Chiari Type I malformation and presented for elective suboccipital craniectomy, C1 laminectomy, and duraplasty. At the postanesthetic visit 24 hours after surgery, the patient reported being aware of the endotracheal tube, the presence of the Mayfield headrest, and of the word "positioning." Inspection of the anesthetic record generated by the AIMS revealed an expired isoflurane concentration of 0% during the interval of positioning; the clinicians recorded a vaporizer setting of 2%.
In Case 2, a 16-yr-old girl with chronic abdominal pain was scheduled for diagnostic laparoscopy and appendectomy. Shortly after emergence, the patient became very upset and tearful. Inspection of the anesthesia record revealed that during the initial minutes of the surgery, the clinician recorded isoflurane vaporizer setting as > 1.5%, but the AIMS recorded end-tidal isoflurane concentrations of 0% to 0.04%. In Case 3, an 18-yr-old girl had a history of a posterior fossa cyst and associated hydrocephalus. She presented for ventriculoperitoneal shunt replacement, along with posterior fossa craniectomy and removal of synthetic graft material. The next day, the patient reported awareness of being turned prone, being naked, and coughing. Review of the anesthesia record revealed that during the interval of turning the patient from the supine to the prone position, the inspired oxygen concentration as automatically recorded by the AIMS was 91% and the expired concentration of nitrous oxide was 13.6%. Desflurane was added only after the prone position was established.
A variety of situational factors may contribute to the likelihood of awareness under general anesthesia. None of the 3 patients was at particularly high risk for awareness based on current understanding of possible predisposing factors. Inaccurate or incomplete capture of essential information about the anesthetics hampers the ability to analyze causes of awareness.
Because an AIMS automatically captures and preserves multiple types of data, it provides a useful tool to analyze cases for factors contributing to awareness. In the cases described here, the analysis of AIMS data reveals the possibility of clinical events, and perhaps clinical errors, that would not be demonstrable with traditional manual record keeping. Overall, the data collected by the AIMS reported in this study suggest that failure to deliver sufficient concentrations of anesthetic gases permitted awareness events. Means to prevent awareness can be instituted via alarm or advisory features built into anesthesia information management systems to enhance vigilance. |
