Assessment of intraoperative awareness with explicit recall: a comparison of 2 methods.

BACKGROUND: Superiority of the modified Brice interview over quality assurance techniques in detecting intraoperative awareness with explicit recall has not been demonstrated definitively. METHODS: We studied a single patient cohort to compare the detection of definite awareness using a single modified Brice interview (postoperative day 28-30) versus quality assurance data (postoperative day 1). RESULTS: The incidence of awareness based on the modified Brice interview was 19 per 18,847 or 0.1%. Fewer awareness cases (incidence 0.02%) were detected by the quality assurance approach (P < 0.0001). CONCLUSION: The modified Brice interview is the preferred modality for assessing intraoperative awareness with explicit recall.

Prevention of intraoperative awareness with explicit recall in an unselected surgical population: a randomized comparative effectiveness trial.

BACKGROUND: Intraoperative awareness with explicit recall occurs in approximately 0.15% of all surgical cases. Efficacy trials based on the Bispectral Index® (BIS) monitor (Covidien, Boulder, CO) and anesthetic concentrations have focused on high-risk patients, but there are no effectiveness data applicable to an unselected surgical population. METHODS: We conducted a randomized controlled trial of unselected surgical patients at three hospitals of a tertiary academic medical center. Surgical cases were randomized to alerting algorithms based on either BIS values or anesthetic concentrations. The primary outcome was the incidence of definite intraoperative awareness; prespecified secondary outcomes included postanesthetic recovery variables. RESULTS: The study was terminated because of futility. At interim analysis the incidence of definite awareness was 0.12% (11/9,376) (95% CI: 0.07-0.21%) in the anesthetic concentration group and 0.08% (8/9,460) (95% CI: 0.04-0.16%) in the BIS group (P = 0.48). There was no significant difference between the two groups in terms of meeting criteria for recovery room discharge or incidence of nausea and vomiting. By post hoc secondary analysis, the BIS protocol was associated with a 4.7-fold reduction in definite or possible awareness events compared with a cohort receiving no intervention (P = 0.001; 95% CI: 1.7-13.1). CONCLUSION: This negative trial could not detect a difference in the incidence of definite awareness or recovery variables between monitoring protocols based on either BIS values or anesthetic concentration. By post hoc analysis, a protocol based on BIS monitoring reduced the incidence of definite or possible intraoperative awareness compared with routine care.

Apneic oxygenation during prolonged laryngoscopy in obese patients: a randomized, controlled trial of nasal oxygen administration.

STUDY OBJECTIVE: To evaluate the influence of nasal oxygen (O(2)) administration on the duration of arterial oxygen saturation (SpO(2)) >or=95% during simulated difficult laryngoscopy in obese patients. DESIGN: Prospective, randomized, controlled trial. SETTING: University hospital. PATIENTS: 30 obese men undergoing general anesthesia. INTERVENTIONS: After thorough preoxygenation, and using total intravenous anesthesia, simulated difficult laryngoscopy was performed, with half the patients receiving additional nasal O(2) during apnea. MEASUREMENTS: Duration of SpO(2) >or=95% was measured up to a maximum of 6 minutes. Lowest SpO(2) values and time to regain 100% SpO(2) (resaturation time) also were recorded. MAIN RESULTS: Nasal O(2) administration was associated with significant prolongation of SpO(2) >or=95% time (5.29 +/- 1.02 vs. 3.49 +/- 1.33 min, mean +/- SD), a significant increase in patients with SpO(2) >or=95% apnea at 6 minutes (8 vs. one pt), and significantly higher minimum SpO(2) (94.3 +/- 4.4% vs. 87.7 +/- 9.3%). Resaturation times were no different between the groups. CONCLUSIONS: Nasal O(2) administration is associated with significant increases in frequency and duration of SpO(2) >or=95%, and higher minimum SpO(2) during prolonged laryngoscopy in obese patients.

Motion of a cadaver model of cervical injury during endotracheal intubation with a Bullard laryngoscope or a Macintosh blade with and without in-line stabilization.

BACKGROUND: Endotracheal intubation in patients with potential cervical injury is a common dilemma in trauma. Although direct laryngoscopy (DL) with manual in-line stabilization (MILS) is a standard technique there is little data on the effect of MILS on cervical motion. Likewise there is little data available regarding alternative airway techniques in this setting. This study compared intubations with and without MILS in a cadaver model of cervical instability. We also used this model to compare intubations using DL with a Macintosh blade versus a Bullard laryngoscope (BL). METHODS: Complete C4-C5 disarticulations were surgically created in 10 fresh human cadavers. The cadavers were then intubated in a random order with either BL or DL with and without MILS. The motion at the unstable interspace was measured for subluxation, angulation, and distraction. RESULTS: MILS did not significantly affect maximal motion of this model in any of the three measures using either DL or BL. There were no clinically significant differences in maximal median motion in any of the three measures when comparing the two blades. However, there was significantly more variance in the subluxation caused by DL than by BL. CONCLUSIONS: We were unable to demonstrate any significant effect of MILS on the motion of an unstable cervical spine in this cadaver model. The BL appears to be a viable alternative to DL in the setting of an unstable lower cervical spine.

A retrospective study of intraoperative awareness with methodological implications.

BACKGROUND: Awareness during general anesthesia is a problem receiving increased attention from physicians and patients. Large multicentered studies have established an accepted incidence of awareness during general anesthesia as approximately 1-2 per 1000 cases or 0.15%. More recent retrospective data, however, suggest that the actual incidence may be as low as 0.0068%. METHODS: To assess the incidence of awareness at our institution, we conducted a review of adult patients undergoing surgical procedures over a 3-year period. Information on awareness came from entries of "Intraoperative Awareness" captured during our standard evaluations on postoperative day one in our perioperative information system. Patients were not questioned specifically about awareness. RESULTS: We reviewed 116,478 charts; 65,061 patients received general anesthesia and 51,417 received other types of anesthesia. Of the patients receiving general anesthesia, 44,006 had complete postoperative documentation. The reported incidence of undesired intraoperative awareness in this population was 10/44,006 (1/4401 or 0.023%). Of the patients who received other anesthetic modalities, 22,885 had complete postoperative documentation. Undesired intraoperative awareness was reported in 7/22,885 patients who did not receive general anesthesia (1/3269 or 0.03%). The reported incidence of intraoperative awareness was not statistically different between the two groups (P = 0.54). Relative risk of intraoperative awareness during a general anesthetic compared with a nongeneral anesthetic was 0.74, with 95% confidence interval [0.28, 2.0]. CONCLUSION: Using a retrospective methodology, reports of intraoperative awareness are not statistically different in patients who received general anesthesia compared with those who did not. These results suggest that, despite success with other rare perioperative events, the resolution of retrospective database analyses may be too low to study intraoperative awareness.

The falcine trigeminocardiac reflex: case report and review of the literature.

BACKGROUND: Trigeminocardiac reflex (TCR), the reproducible hypotension and bradycardia upon stimulation of the trigeminal nerve, has been reported during craniofacial surgery and during surgery within the cerebellopontine angle, petrosal sinus, orbit, and trigeminal ganglion. Whereas the falx cerebri is known to be innervated by the nervus tentorii, a recurrent branch of V1, there have been no reports to date of this response upon mechanical stimulation of the falx. CASE DESCRIPTION: We report a case of immediate, reproducible, and reflexive response of asystole upon stimulation of the falx cerebri during operative resection of a parafalcine meningioma in a 53-year-old woman. Upon recognition of the reproducible relationship between falcine stimulation and increased vagal tone, the patient was given glycopyrrolate in an effort to block cholinergic hyperactivity. After glycopyrrolate was given, no further dysrhythmias occurred. CONCLUSION: In this patient, mechanical stimulation of the falx likely resulted in the hyperactivity of the trigeminal ganglion, thereby triggering TCR. The dorsal region of the spinal trigeminal tract includes neurons from hypoglossal and vagus nerves, and projections have been seen between the vagus and trigeminal nuclei. The vagus provides parasympathetic innervation to the heart, vascular smooth muscle, and abdominal viscera. Vagal stimulation via these connections after trigeminal nerve activation likely accounts for the reflexive response of asystole seen in this patient. This is confirmed by the observation that the reflex was inhibited by the anticholinergic effects of glycopyrrolate. Awareness of TCR allows for early detection and appropriate treatment.

Variable systolic pressure variation and dynamic hyperinflation due to an intrabronchial tumor.

Systolic pressure variation (SPV) is the cyclic change in systolic blood pressure secondary to positive-pressure ventilation. It is normally a good indicator of intravascular volume and often can be substituted for central venous pressure monitoring, but the reliability of SPV for this use depends on the multiple determinants of intrathoracic pressure remaining constant. We present a case in which an intrabronchial tumor caused dynamic hyperinflation of one lung. This situation, in turn, caused a marked increase in SPV but, more importantly, it increased variability of the SPV despite normal intravascular volume. We discuss the physiology of SPV and the implications of this case for the use of SPV as a monitor of intravascular volume.