Elderly patients undergoing ambulatory gastrointestinal procedures often receive inappropriately high doses of anesthesia at induction, researchers have found.
The study, a review of the anesthetic management of patients undergoing upper endoscopy and colonoscopy at Yale School of Medicine, in New Haven, Conn., found that even with age-adjusted dosing, significant drops in mean arterial pressure occur.
“The elderly population may be more susceptible to adverse events from anesthesia, such as hypotension, given the cardiovascular, pharmacokinetic and pharmacodynamics changes associated with aging,” said Vicki Bing, BS, a medical student at Yale who helped conduct the study. “So it is recommended that anesthetic dose be adjusted for age. It’s been unclear, however, whether current practices adequately correct dosing for increasing age.”
Ms. Bing and her colleagues sought to determine whether induction anesthetics are dose-adjusted for age and, if they are, if this results in increased hypotension.
They examined the anesthesia records of 799 adults who underwent non-emergent, ambulatory gastrointestinal procedures at Yale over a six-week period in 2013. They recorded induction doses of propofol and fentanyl, and looked for changes in mean arterial pressure (MAP) within 10 minutes of induction. Anesthetic doses and changes in MAP were compared across age groups (the oldest group aged ≥80 years) and across ASA classes 1 to 4, which indicate severity of illness.
No Adjustment in Fentanyl Dosing for Age
The researchers found there was no difference in fentanyl dosing between age groups, indicating that this anesthetic’s dose is not being reduced appropriately for elderly patients. Interestingly, mean fentanyl dose increased with increasing ASA class (P=0.03).
Propofol dosage, in contrast, was significantly different across age groups (P<0.01), with older patients (≥65 years) receiving less drug than younger (<65) patients. An exception was patients in ASA classes 1 and 2, in which propofol dosage did not differ between young and old patients. Notably, despite the fact that older patients received lower propofol doses, patients aged 65 and older experienced significantly greater drops in MAP.
“Our take-home point is that propofol dosing is not appropriately adjusted for age and for ASA classes 1 and 2, and with propofol dose adjustments, MAP changes are still significant in older patients,” Ms. Bing said.
Shamsuddin Akhtar, MD, associate professor of anesthesia at Yale School of Medicine and senior author of the study, said the findings show that anesthesia providers are more likely to adjust dosing by ASA class than by age. “Sicker patients get a little less anesthetic,” Dr. Akhtar said.
The researchers’ next step, he said, is to delve into the pharmacodynamics data for the oldest age group, which is an area not well understood. He believes they will find that MAP reductions are even greater in that subset.
As for recommendations, Dr. Akhtar said, “We think there are opportunities to decrease the dose, and [clinicians] should not only be looking at ASA class but also age. There’s more room for reducing the dose in the elderly, especially patients above age 80.”
“We know the elderly lack the cardiac, respiratory and renal reserves that younger patients have,” he explained. “Significant drops in MAP can result in end-organ damage, but they also trigger therapeutic interventions with vasopressors, fluids and so forth that can have negative consequences in patients with minimal reserves. Prevention of these scenarios is better than cure.”
Basavana Goudra, MD, assistant professor of anesthesiology and critical care medicine at the Hospital of the University of Pennsylvania, in Philadelphia, said, “Almost 80% of my work is for gastrointestinal procedures, so I do these sedations frequently. I have found that optimal dosing goes far beyond just age and ASA classification. It’s more an art than a science,” Dr. Goudra said in an interview.
Anesthetic pharmacokinetics and pharmacodynamics are extremely variable among patients, he pointed out. “With older patients, we typically start with low doses, but having said that, I once sedated a 104-year-old patient for colonoscopy,” Dr. Akhtar said. “I ended up dosing her almost as much as a 50-year-old. If I administer propofol to maintain a plasma concentration of 2 mcg per cc in 100 patients, the response could range from awake to deep general anesthesia, depending on the brain response of the given patient.
“You need a very observant clinician,” he added. “No matter what you do, you will have some patients slipping too low and some being awake.”
Dr. Goudra added that he would like to see brain function monitoring be part of training clinicians to measure the depth of sedation. “It’s very difficult to learn dosing. It’s very provider-dependent,” he said.