Obesity and the Risks of Anesthetic Complications
The Global Textbook of Anesthesiology (1) states that there are a number of factors that anesthesiologists need to take into account when they are treating people who suffer from obesity or being overweight. There are a number of steps and precautions to be taken in any case when anesthetizing people who are obese; just some of these are avoiding opioids and sedation; avoiding intramuscular injections due to unpredictable absorption; an electrocardiogram (EKG) must be performed in advance to look for ischemia, arrhythmia, strain patterns and hypertrophy; a chest X-ray (CXR) should also be performed to examine the size of the heart; as well as consultation with a cardiology professional. (2) Additional caution must be taken when using mask ventilation and it’s also possible that the incubation process can cause airway collapse, which leads to upper airway obstruction. (3) Additionally, patients who are obese and need anesthetization also need to be taken care of more than others. It is even recommended that a tracheostomy kit and a surgeon remain on stand-by just in case airway management emergencies need to be dealt with.
Further complications can arise when treating obese patients and using anesthetization: there is an increased mortality rate (6.6% compared to 2.7% in non-obese patients), decreased lung-capacity is also expected, acute airway obstruction is more prevalent, wound infections are not uncommon, deep vein thrombosis and pulmonary embolism is also twice as more likely than in non-obese people. (4) Special humidified gases are required to oxygenate obese patients, as well as a semi-recumbent position, nasal continuous positive airway pressure (CPAP) devices and extubation (removal of breathing apparatus) only when the patient is fully awake. (5)
Obesity, bariatric surgery and anesthesia
According to a fact sheet published by the American Society for Metabolic & Bariatric Surgery, there is a surgery prescribed for candidates who have a body mass index (BMI) of 40 or more, or a BMI of 35 or more with an obesity-related disease, such as Type 2 diabetes, heart disease or sleep apnea. (6) The surgery limits drastically the amount of food the stomach can hold, by reducing the capacity of the organ to just a few ounces. This drastic surgery can resolve a large number of 30 obesity-related conditions, primarily Type 2 diabetes, heart disease, sleep apnea, hypertension and high cholesterol. The various types of surgery available are gastric bypass surgery (87% patient success rate at resolving Type 2 diabetes) and band surgery (73% Type 2 diabetes resolution). These surgical interventions cut the risk of developing coronary heart disease in half and can resolve obstructive sleep apnea in more than 85% of patients. (7)
The challenge to anesthesia and intensive care
Obesity presents a significant challenge to anesthetists and emergency care workers. (8) In particular, because of issues with the respiratory system, obesity can present a large problem for the introduction of certain breathing apparatus during the anaesthetic procedures (intubation). Additionally, approximately 5% of morbidly obese patients will have obstructive sleep apnea (OSA). (9)Problems with the respiratory system can interfere with the anesthetic process in a number of ways: episodes of apnea or hypopnea during sleep while undergoing surgery under a general anaesthetic can be fatal, so emergency crew need to be on hand as well as a breathing specialist. Snoring is also common and can interfere with medical equipment used for anesthesia. Apnea in general can lead to other physiological issues, such as hypoxemia, ypercapnia and pulmonary and systemic vasoconstriction. (10)
For all of these reasons, most of the medical and scientific texts advise that “a careful and detailed assessment of the morbidly obese patient’s upper airway is required before they are anesthetized.” (11) A proper evaluation has to include a) assessment of the head and neck flexion, extension and lateral rotation, b) assessment of jaw mobility and opening of the mouth, c) inspection of the teeth and gums, d) nostrils, and e) previous anesthetic charts and the patient’s medical history. If there is time, then it’s possible that both X-rays and CT scans along with consultation with an otolaryngoligist might be critical as well. (12)
A further point is that oxygen and carbon dioxide are both increased in the obese as a result of metabolic activity. This indicates that the doses used in the breathing apparatus and the quantities and metric volumes must be higher than in people of regular weight.
Body mass index and respiration
It has been shown that there is a direct relationship between increasing body mass index and a decline in respiratory ability. (13) An accumulation of fat tissue around the chest wall can block the entry of oxygen into the lungs. Obesity has a direct effect on the ability of the lungs to draw in the needed amount of oxygen for the body to function. One of the side-effects of this, which explains why overweight people breathe quickly, is that the lungs and the heart must work harder to draw the requisite amount of oxygen into the body, resulting in short and shallow breaths. This has an effect during sleep and if a patient sleeps on their back in the supine position, then it’s more likely that they will also snore and have difficulty breathing. (14)
Pressure from the abdomen, reduction in the ability of the lungs to draw in breath and an increase in metabolic demands for oxygen result in inefficiency of the muscles around the chest and lungs to breathe. Obese people generally work 30% harder to breathe and this explains why their lungs, heart and surrounding muscles become worn out faster and can also lead to cardiovascular issues.
The solution is weight loss and a healthy lifestyle!
While surgical intervention is possible for obesity, this should only ever be used as a last resort when regular weight-loss programs are ineffective or if there are other factors which prevent a change in lifestyle. But for people who are overweight or obese, regular exercise and a change to a healthy diet are the best ways to fight obesity, which means that if you need to be anesthetized, then the procedure is less taxing for the medical staff and also presents a much lower chance of complications that can even lead to unwanted death on the operating table. In fact, most doctors will recommend a regime of weight loss before any surgery is allowed to take place.