Predictors Listed of Prolonged Extubation After General Anesthesia

Author: Michael Vlessides

Anesthesiology News

Researchers have confirmed a series of independent patient-, procedure- and anesthesia-related predictors of prolonged extubation after general anesthesia.

The study also showed that patients who experience prolonged extubation are at significantly greater risk for immediate reintubation.

Andrea Vannucci, MD, and his colleagues at the University of Mississippi Medical Center and Washington University in St. Louis, were interested in examining the quality and patient safety implications of prolonged extubation.

“We know from several studies that prolonged extubation is associated with inefficient workflow in the operating room, including the possible delay of subsequent case starts,” said Dr. Vannucci, a professor of anesthesiology and the vice chair of quality and safety in anesthesiology at the University of Mississippi Medical Center, in Jackson. “This is particularly problematic in operating rooms that are scheduled to go for more than eight hours.

Factors Affecting Prolonged Extubation Poorly Understood

Research has shown that prolonged extubation can be affected by the use of specific anesthetic agents, as well as individual surgical and anesthesia-related variables, such as surgeon specialty, case length, intraoperative prone position and, possibly, use of an extraglottic airway instead of a tracheal tube. Nevertheless, the role of underlying patient characteristics and additional anesthesia-related factors—such as the choice of specific neuromuscular blocking agents, their reversal, and the administration of potential traumatic ventilation—is not well understood.

The investigators analyzed data from a cohort of 86,123 first-encounter adult patients who underwent general anesthesia with either an extraglottic airway or tracheal tube between Jan. 1, 2010, and Dec. 31, 2014.

“We focused on a population of patients supposedly at low risk of prolonged extubation, so we did not include those undergoing neurosurgery, cardiothoracic surgery or thoracic surgery,” Dr. Vannucci said. Other exclusion criteria included patients who came to the OR with a tracheal airway already in place, those discharged from the OR without undergoing extubation, and patients with no documented extubation time.

The observational study’s primary outcome was the time from end of surgery to extubation. Time intervals were categorized as:

• normal extubation (within 15 minutes);
• prolonged extubation (16-60 minutes); or
• very prolonged extubation (>60 minutes).

Univariable logistic regression was used to identify patient-, procedure- and anesthesia-related variables associated with prolonged and very prolonged extubation. All the variables that were found to be significantly associated with outcomes in the analysis, along with other clinically plausible variables, were then included in a multivariable logistic regression analysis.

“We were especially interested in the anesthesia-related predictors because they are under our control,” he explained.

Predictors Include Time of Day

In a conversation with Anesthesiology News at the 2019 annual meeting of the International Anesthesia Research Society (abstract F180), Dr. Vannucci reported that 77,628 patients (90.1%) were extubated within 15 minutes of the end of surgery, 8,138 patients (9.5%) were extubated between 16 and 60 minutes after surgery (prolonged extubation), and 357 patients (0.4%) were extubated more than 60 minutes after surgery (very prolonged extubation).

Several independent predictors of both prolonged and very prolonged extubation were identified.

“We were able to confirm that the intraoperative prone position is a strong predictor associated with both prolonged extubation and very prolonged extubation [odds ratio (OR), 2.31; 95% CI, 2.15-2.49],” Dr. Vannucci explained. “The use of a tracheal tube instead of an [laryngeal mask airway] was also associated with prolonged extubation [OR, 3.15; 95% CI, 2.55-3.91],” Dr. Vannucci said.

Of note, extubation after 5 p.m. (compared with 7 a.m. to 5 p.m.) was also associated with very prolonged extubation (OR, 2.32; 95% CI, 1.80-2.99). “I imagine this is likely because clinicians are more cautious at these times,” he said.

Similarly, receiving a blood transfusion was also associated with both prolonged and very prolonged extubation (OR, 3.58; 95% CI, 2.56-4.92). “Again, I think blood transfusion is a situation that prompts some caution and closer observation on the part of the anesthesiologist,” Dr. Vannucci said.

Perhaps not surprisingly, greater doses of neostigmine were also associated with prolonged and very prolonged extubation. Conversely, use of benzylisoquinolines was found to be protective against prolonged extubation (OR, 0.68; 95% CI, 0.54-0.87).

“This study was performed using data from the pre-sugammadex era, but it was interesting to see that benzylisoquinolines were the most protective against prolonged extubation among the neuromuscular blocking agents,” he explained.

The analysis yielded one finding that proved puzzling to the researchers. Nonprotective ventilation—which the researchers defined as either tidal volume greater than 12 mL/kg ideal body weight and/or peak airway pressure of at least 35 cm H₂O—was protective against prolonged and very prolonged extubation for the first 120 minutes, but became a strong predictor of both after two hours.

“I don’t know if it’s because a limited amount of nonprotective ventilation corresponds with a recruitment strategy or because maybe it takes some time for the damage to manifest itself,” Dr. Vannucci said.

The investigators also quantified the median extubation time associated with some of the risk factors. This analysis found that median extubation time was four versus six minutes when the airway was controlled with an extraglottic airway compared with a tracheal tube, and 10 versus six minutes when the intraoperative position was prone versus supine or lateral.

“Clinically, I think this could translate into different consequences,” Dr. Vannucci said. “When we schedule cases, we may need to be a little more realistic about turnover time,” he said. “So if the patient is prone or supposed to be intubated, we should consider that the turnover time is going to be longer. And all other things being equal in terms of safety for the patient, maybe this would prompt the more frequent use of the [laryngeal mask airway] rather than an endotracheal tube.”

Immediate Reintubation Also Studied

In a second part of the investigation, the researchers examined immediate reintubation rates among the three groups of patients. This analysis found that the immediate reintubation rate among the total population was 0.105% (95% CI, 0.08%-0.13%).

However, there was an incremental increase in the rate of immediate reintubation as extubation was prolonged: 0.1% in the normal extubation group; 0.3% in the prolonged extubation group; and 2.8% in the very prolonged extubation group.

“There was also an association between prolonged extubation and patients being ventilated or assisted in the PACU,” Dr. Vannucci added. “So these patients are not only reintubated more frequently; they also need more respiratory support in the PACU.

“That’s interesting to me because it means that we are all probably under a lot of pressure when patients are late to wake up because there is an expectation that we are efficient,” he added.