APSF Papers Highlight Safety

Glenn S. Murphy, MD; Jeffery S. Vender, MD

Over 1500 abstracts were presented at the 2003 American Society of Anesthesiologists Annual Meeting in San Francisco. During 6 poster sessions, more than 100 scientific papers were exhibited which related directly to patient safety. The following review will highlight a few of the many interesting patient safety abstracts.

Airway Management

Prion proteins have been identified in human tonsillar tissue. There exists a theoretical risk of transmission of variant Creutzfeldt-Jakob disease from reusable anesthesia equipment. Mathur et al. (A-1232) examined the incidence of protein contamination on cleaned laryngoscope blades. Thirty previously used, cleaned blades were collected, as well as 6 used, unclean blades. Protein staining was identified on all previously used blades, and the degree of protein staining on cleaned blades was statistically indistinguishable from unclean blades. These data suggest that current methods of removing contaminants from airway devices (autoclaving and chemical processes) are insufficient in eliminating protein deposits.

The efficiency of cricoid pressure in reducing the risk of regurgitation during induction of anesthesia has not been previously studied. Oehlkern et al. (A-1235) randomized 130 patients at high-risk of regurgitation to receive cricoid pressure or no cricoid pressure. Prior to entering the operating room, each patient swallowed a capsule of methylene blue. During laryngoscopy, regurgitation was evaluated by the presence or absence of blue coloration in the pharynx. No methylene blue was observed in patients in the cricoid pressure group, whereas evidence of regurgitation was noted in 3 patients in the no cricoid pressure group. This study suggests that cricoid pressure might provide protection against gastric content regurgitation.

Two abstracts from the Mayo Clinic-Scottsdale (A-1244, A-1245) examined the effectiveness of methods used to communicate to patients a history of a difficult airway. During a 3 to 4 year period, all patients with a history of a difficult airway were informed of this problem during a postoperative visit and sent a “difficult airway” letter. Of the 113 patients contacted, 50% had no recall of any conversation with their anesthesiologist, and 29% claimed that they had not received a “difficult airway” letter. When 28 of these patients presented for a subsequent surgical procedure, the majority (22 patients) denied any history of previous anesthetic complications. Unfortunately, the combination of verbal communication and written notification might not be an effective method of identifying patients with a history of difficult airways.

Cervical spine surgery may be associated with postoperative airway swelling and the need for emergency re-intubation or tracheostomy. Matsumoto et al. (A-1254) performed a study to determine if combined anterior-posterior cervical spine surgery resulted in an increased risk of emergent re-intubation, compared with other cervical spine surgeries. Over a 2-year period, 156 patients underwent cervical spine surgery; an antero-posterior approach was used in 10 of these patients. Emergent postoperative re-intubation was required following 30% of the antero-posterior procedures, compared to only 1% of all other surgical approaches. Clinicians should be aware that combined anterior and posterior spine surgery appears to increase the risk of life-threatening postoperative airway swelling in this limited study.

Postoperative Hypoxemia

Hypoxemia after general anesthesia has been associated with adverse postoperative complications. The goal of the study by Billard et al. (A-1302) was to build a model that could identify patients at high risk for hypoxemia in the PACU. Six hundred and five patients were used to establish the model and 196 to validate it. Hypoxemia (SpO2 <90%) occurred in 23% of the subjects. Multivariate analysis found that body mass index, age, baseline SpO2, peripheral or laparoscopic surgery, anesthesia duration, and methylene blue administration were all significantly related to postoperative hypoxemia. The performance of the model was good when tested on the second group of patients.

Curry et al. (A-1306) compared the incidence of postoperative hypoxemic events in patients undergoing major abdominal or major peripheral orthopedic procedures. Continuous central pulse oximetry was performed for 24 hours. No significant differences were found between the groups in the probability of having hypoxemic events. These data suggest that factors other than type of surgery play a primary role in postoperative hypoxemia. The authors also observed that the number of hypoxemic events recorded with continuous oximetry (n=3959) was significantly greater than the number of episodes documented in the chart (n=23). In an additional study from the same group (Curry et al., A-1312), the authors tested the hypothesis that intensive postoperative pain control produces postoperative hypoxemia. Orthopedic patients (n=135) receiving either intrathecal morphine or intrathecal morphine plus narcotic PCA for postoperative pain management were monitored with central pulse oximetry for 24 hours. More than 75% of patients had 1-2 episodes of hypoxemia per hour, and 31% of these episodes were severe (SpO2< 85%). Hypoxemic events are common when an aggressive analgesic strategy is used, particularly when a PCA is used in combination with intrathecal morphine.


The relationship between bispectral index (BIS) monitoring and clinical outcomes was examined in a study by Monk et al. (A-1361). A retrospective analysis of mortality rates using Medicare data was performed. Overall 1-year, post-discharge mortality was 9.1%. Risk-adjusted mortality rates were lower in hospitals that routinely used BIS monitoring (8.7%) compared to hospitals with no BIS utilization (9.3%, p<0.001). The authors hypothesized that difference in mortality might be related to a decrease in cumulative deep anesthesia times at hospitals with higher levels of BIS monitoring.

The incidence of drug administration errors in a large academic anesthesia practice was reported by Bowdle et al. (A-1358). During a 21-week period, anonymous survey forms were returned following 6,709 anesthetics. There were 41 reports of errors (0.68%) which were distributed among attendings, residents, and CRNAs. Twenty-nine of these errors resulted in unintended drug effects, and 14 were associated with drug infusions delivered by a pump. These data support the belief that drug administration errors are not rare events in the operating room.
Bhananker et al. (A-1356) analyzed claims from the ASA Closed Claims database to determine patterns of injury and liability associated with monitored anesthesia care (MAC). Of a total of 4,454 cases in the database, MAC accounted for 150 claims. Monitored anesthesia care represented 2% of the claims before 1990, compared to 5% of claims after 1990 (p<0.05). Compared to general and regional claims, MAC cases involved older, sicker patients undergoing more eye and plastic surgery procedures. Inadequate oxygenation and ventilation was also more common in MAC claims. Payments for injuries during MAC were as high as those occurring after general or regional anesthesia.

The wrist is frequently maintained in a hyperextended position following radial artery catheter placement. Chowet et al. (A-1354) studied the effects of wrist hyperextension on motor and sensory conduction in the median nerve. Compound sensory and motor action potentials were measured in 12 awake volunteers. In 10 of 12 subjects, conduction block developed within an average time of 43 minutes. The authors state that prolonged periods of hyperextension may be associated with significant neuropathy.

This brief review only summarizes a small portion of the abstracts on patient safety that were presented at the 2003 ASA Annual Meeting. All of the abstracts from the 2003 meeting may be viewed at the Anesthesiology website at www.anesthesiology.org.

Dr. Murphy is the Director of Cardiac Anesthesia at Evanston Northwestern Healthcare and an Assistant Professor at Northwestern University Medical School.

Dr. Vender is Chairman of the Department of Anesthesia at Evanston Northwestern Healthcare and a Professor at Northwestern University Medical School. Both are members of the APSF Newsletter Editorial Board.