Author: Naveed Saleh MD MS
Monitored anesthesia care (MAC) might be preferred over general anesthesia (GA) in surgical patients with pulmonary hypertension, a study has concluded.
Patients with pulmonary hypertension have high perioperative mortality and morbidity rates, but few studies have compared MAC with GA. Consequently, it is unclear whether the type of anesthesia is a factor in these adverse events. Furthermore, no specific guidelines exist to help providers choose the appropriate type of anesthesia for their patients beyond concerns about hypoxia or hypercarbia—issues that are more challenging to manage with MAC.
“There is a common thought, especially in anesthesia, that MAC can be very dangerous for patients who have pulmonary hypertension,” said Emily Methangkool, MD, MPH, a cardiac anesthesiologist at UCLA Health, in Los Angeles. She presented the study findings (abstract SCA062) at the 2019 annual meeting of the Society of Cardiovascular Anesthesiologists. “Because while you are under sedation under MAC, patients can get hypoxic, hypercarbic, and their [pulmonary vascular resistance] can increase, which can lead to a lot of problems while they are under sedation. What our study showed, which was quite surprising to me, was that patients who had MAC did just as well if not better than patients who had GA.”
This retrospective study compared clinical outcomes in patients with pulmonary hypertension between GA and MAC during noncardiac surgery. Of note, researchers identified cases that could have been performed with either GA or MAC. Patients had right ventricular systolic pressure (RVSP) of 40 mm Hg or higher and were administered MAC at least once between April 1, 2013, and March 10, 2018. Cases were given surgical risk scores based on the 2007 guidelines of the American College of Cardiology and American Heart Association. Covariates were adjusted for in the analysis.
In total, 1,725 patients were included in the study, with 1,263 receiving MAC and 462 receiving GA. The mean RVSPs between the two groups were similar (MAC, 50.1±11.2 mm Hg; GA, 49.7±10.5 mm Hg; P=0.527). When compared with patients receiving MAC, those who underwent GA experienced poorer outcomes: longer hospital stays; higher rates of inpatient death; longer mechanical ventilation time; and increased rates of postoperative acute kidney injury, myocardial infarction and new diuretic use.
Dr. Methangkool attributed these results partly to intraoperative fluctuations. “We are giving much larger doses when we induce GA compared with MAC. You may have more hemodynamic fluctuations on induction of GA compared to initiation of MAC due to the larger doses required for GA, which may contribute to the results we saw in this study.”
Dr. Methangkool said she believes the study results will make providers more confident in MAC. “I think this gives a lot of assurance to a lot of anesthesia providers that MAC can be safe in patients with pulmonary hypertension, … especially since our patient population is quite large—over a thousand patients.”
However, she cautioned that MAC might not be the appropriate choice for every patient, especially those at risk for aspiration or who have severe acid reflux, severe abdominal distention, ascites, severe chronic obstructive pulmonary disease or severe obstructive sleep apnea.
“Sometimes MAC can be a little dangerous,” Dr. Methangkool said. “If there are unexpected problems during the procedure and MAC wouldn’t be sufficient, we would have to induce GA and give the patient an endotracheal tube.”
Dr. Methangkool noted that her study had certain limitations. “It was a single-center study only done at UCLA. Whether these results are applicable to a general population or other centers is questionable. Although we had 1,000 patients, I think if we had a larger number of patients it would reinforce the findings of our studies. That would be a good future direction of our studies.” Dr. Methangkool estimated that the use of MAC at UCLA is consistent with that of other centers.
In a separate interview with Anesthesiology News, Marie-Louise Meng, MD, an assistant professor of anesthesiology at NewYork-Presbyterian/Columbia University Medical Center, in New York City, said: “This retrospective study of patients with pulmonary hypertension who underwent surgery using MAC versus GETA [general endotracheal anesthesia] presents important evidence that avoiding the use of general anesthesia may decrease morbidity in this population. Therapies for pulmonary hypertension have improved over the last two decades, so these patients are living longer and presenting for noncardiac surgery as the risks of procedures in these patients are no longer always deemed prohibitive. The anesthesiologist, therefore, now needs to pay closer attention to risks of MAC versus GETA, and perhaps utilize regional anesthesia and sedation when possible over GETA.”