This was a lecture from the ASA national meeting.
Complications in treating obese patients were discussed Sunday in “Evidence-Informed Anesthesia for the Severely Obese: Example Obstetrics and Gynecology – Does It Exist?” Three presentations looked at challenges during childbirth, the effect of using higher doses of drugs based on weight and the respiratory physiology of the obese.
Addressing challenges during childbirth was Vilma E. Ortiz, M.D., of Massachusetts General Hospital, Boston, in “Safely Off to Sleep: General Anesthesia in the Obese Patient.” There is no definition of obesity in pregnancy, but in general, a pregnant woman is considered obese if her BMI is greater than 30, and morbidly obese if her BMI is greater than 40.
A study noted greater risks of several complications in extreme obesity during pregnancy, including need of a C-section, preterm delivery, preeclampsia and gestational diabetes mellitus. Among the conditions noted in the upper airway are rhinitis, an increased neck circumference and a more narrow airway.
Dr. Ortiz noted three “essential steps” for the safe induction of general anesthesia – a thorough airway evaluation, adequate preoxygenation and positioning considerations for preoxygenation, induction and emergence. It is important in airway evaluation to consider the size and quality of dentition, neck diameter and tongue size to estimate the likelihood of a difficult intubation. Adequate preoxygenation maximizes the oxygen reserves during the apnea that follows induction of a general anesthetic. For positioning, elevating the head is recommended for improved chest wall and lung expansion.
John L. Walsh, M.D., also of Massachusetts General Hospital, presented “Antithrombotics and Prophylactic Antibiotics in the Obese Patient” in which he discussed the use of higher doses of drugs.
Pregnant women have a fourfold to fivefold increased risk of thromboembolism compared with non-pregnant women. The risk increases with gestation and is highest in the first week post-partum, he said.
Some have argued that low molecular weight heparin (LMWH) is pharmacokinetically more predictable for preventing thromboembolism, so increased doses can be used. However, studies confirming the use of greater doses have not been conducted on obese or pregnant patients, Dr. Walsh said.
He also discussed clinical practice guidelines for antimicrobial prophylaxis in surgery, and focused on the use of cefazolin and gentamicin. Dr. Walsh concluded that there are data to support giving higher doses of antibiotics as prophylaxis.