Author: Michael Vlessides
Propofol administered intravenously as an 0.5 mg/kg bolus at emergence does not reduce cough following desflurane-based general anesthesia, according to a new study. In addition, propofol was found to prolong extubation time by approximately three minutes over placebo, leading the authors to question the efficacy of the agent in these situations.
“We know that emergence is an important period after surgery, and cough can have several adverse effects,” said Marie-FÉlix Ouellet, MD, a resident at the University of Montreal. “There are many indications for smooth emergence; they can be patient-related or surgery-related.
“We also know that propofol inhibits airway reflexes and that [total IV anesthesia] is associated with a lower incidence of cough compared to inhalational anesthesia,” she added. “Therefore, we hypothesized that giving propofol as a single bolus would reduce cough at emergence from general anesthesia under desflurane.”
Patients were randomly assigned to receive a bolus of either 0.5 mg/kg of propofol or normal saline (0.05 mL/kg) at the end of surgery, at 1.0 minimum alveolar concentration (MAC). At that point, desflurane was discontinued and fresh oxygen flow was increased to 10 L per minute. A standardized “no-touch” emergence technique was also employed.
Extubation Time Longer With Propofol
Presenting the study at the 2018 annual meeting of the Canadian Anesthesiologists’ Society (abstract 441311), Dr. Ouellet noted that no significant difference was found between groups for the incidence of cough (propofol, 95.9% vs. controls, 83.8%; P=0.064). Cough occurred at an average of 0.12 MAC of desflurane in each group.
Similarly, the intensity of cough did not differ between groups (Table). “Our cough scale was very strict,” Dr. Ouellet said. “But if we remove patients who had no cough or mild cough and look at only those who had moderate and severe cough, we can still see that there was no difference between groups.”
|Table. Cough Intensity in Propofol And Control Groups|
|Cough Score||Propofol, n (%)||Normal Saline, n (%)|
|0 (no cough)||3 (4.1)||11 (16.2)|
|1 (mild, single cough)||19 (26.0)||16 (23.5)|
|2 (moderate; lasting <5 seconds)||29 (39.7)||18 (26.5)|
|3 (severe; sustained for >5 seconds)||22 (30.1)||23 (33.8)|
Interestingly, the time to extubation was found to be prolonged by three minutes and 26 seconds for patients who received propofol (10 minutes, 41 seconds vs. seven minutes, 14 seconds; P<0.01). More of the patients in the propofol group also needed vasopressors at emergence than those in the control group (eight vs. one; P=0.035). Finally, sore throat score was significantly higher among propofol patients (visual analog scale, 1.7 vs. 1.0; P=0.034), although the researchers acknowledged that the difference was not clinically relevant.
During recovery, the incidence of sedation, agitation, and postoperative nausea and vomiting were similar in the groups.
“So we can see that propofol 0.5 mg/kg administered at 1.0 MAC desflurane did not reduce cough following general anesthesia compared to placebo,” Dr. Ouellet said. “But why would TIVA with propofol reduce cough and not a single bolus? Maybe it’s because of the very short distribution half-life of propofol, or maybe we didn’t give the right dose at the right time.
“If we compare propofol to remifentanil—which has a very short half-life too—we know that an infusion of remifentanil will reduce cough, but not when given as a bolus,” she said. “For future research, I think that if you are studying a drug with a very short distribution half-life, it’s better to give it as an infusion rather than a bolus.”
Some of Dr. Ouellet’s audience members questioned the timing of the propofol administration. “Do you think you administered the propofol a little too early?” asked Sumitra G. Bakshi, MD, an attending anesthesiologist at Tata Memorial Hospital, in Mumbai, India. “You gave it at 1.0 MAC, when they’re still deep with desflurane. Maybe that’s the reason why you didn’t see a difference. Would it have helped if the propofol was administered at 0.2 or 0.3 MAC, when the patient was a bit lighter?” Dr. Bakshi asked.
“Cough usually occurs at 0.2 MAC or less,” Dr. Ouellet replied. “So at 0.2, it would likely be too late, because we may have already seen some coughs before that. So maybe it’s true that we gave it too early, but if we give it later, it will affect the extubation.”
“It is a tricky situation,” commented session moderator Mahesh Nagappa, MD, an assistant professor of anesthesia and perioperative medicine at Western University’s Schulich School of Medicine & Dentistry, in London, Ontario. “If you wait for the desflurane to wear off and then give propofol, every patient will respond very differently. Sometimes they move, which may be a problem. Because when you’re doing something like neuroanesthesia, a smooth extubation is a must.”