A Metabolic Equivalent of Task (MET) is a standardized measurement of the energy cost associated with physical activities. It quantifies the rate at which the body expends energy relative to the energy expended while at rest. One MET is equivalent to the energy used when sitting quietly, serving as a baseline. For instance, an activity requiring 3 METs demands three times the energy expenditure of resting.
The Role of METS in Preoperative Assessment
Healthcare providers, especially anesthesiologists, assess a patient’s physical fitness before surgery. This helps them understand the body’s capacity to handle the procedure’s demands. Surgery and anesthesia introduce physiological stress, impacting organ systems like the heart and lungs. The body must increase oxygen consumption and cardiac output to meet these demands and recover effectively. A patient’s METS score gauges their “functional capacity,” reflecting their ability to respond to and recuperate from this stress.
A lower METS score indicates reduced functional capacity, linked to a greater likelihood of complications during and after surgery. Patients with a limited ability to perform daily activities face an increased risk of major adverse cardiac events (MACE) in the perioperative period. A score below 4 METs is a recognized threshold that raises concern in preoperative evaluations. This benchmark suggests insufficient cardiovascular reserve to withstand the physiological challenges of surgery.
Determining a Patient’s METS Score
A patient’s METS score is determined through a structured questionnaire or interview focusing on their ability to perform common daily activities. This assessment does not involve a physical exercise test, making it a practical tool for routine preoperative evaluations. Questions revolve around tasks such as self-care, household chores, and recreational pursuits. The responses help estimate the patient’s maximum sustained activity level.
For example, activities like sitting quietly or eating are assigned 1 MET. Light housework, such as dusting or walking leisurely, are 2 to 3 METs. More vigorous activities, like climbing one or two flights of stairs, walking briskly at 4 miles per hour, or scrubbing floors, are 4 to 5 METs. Strenuous activities, including jogging, swimming laps, or competitive sports, exceed 6 METs. The ability to perform activities valued at 4 METs or more indicates adequate functional capacity.
Anesthesia Management for Low METS Scores
Identifying a patient with poor functional capacity, such as a METS score below 4, does not automatically lead to surgery cancellation. Instead, this finding prompts a more thorough evaluation to quantify associated risks. The medical team may seek further consultation, often involving a cardiologist, to understand the patient’s cardiac health. This assessment might include an electrocardiogram (ECG) to check heart rhythm, an echocardiogram to visualize heart structure, or a cardiac stress test to measure exercise capacity and identify underlying heart issues.
The anesthesia plan is then adjusted to accommodate the patient’s reduced functional capacity and minimize physiological stress. This may involve more intensive intraoperative monitoring, such as an arterial line to track blood pressure. Anesthesiologists may also select specific anesthetic drugs gentler on the cardiovascular system, reducing heart strain. The postoperative care plan might be modified to include recovery in a high-dependency or intensive care unit, ensuring closer monitoring and specialized support.