Anesthesia-related morbidity, while rare, is a useful indicator for obstetric care quality and patient safety during childbirth. Previous studies—including those correlating anesthesia complications with cardiac arrest, pre-existing conditions, living in rural areas, neuraxial block, respiratory arrest, and unrecognized spinal catheterization—focused on specific neuraxial anesthesia or specific complications instead of analyzing multiple complications within a large population. The aim of this study was to determine the incidence of anesthesia complications as well as the association of anesthesia-related adverse events and medical or obstetric conditions.
This retrospective study used hospitalization data from ~75% of all obstetric deliveries in Canada from April 1, 2004 to March 31, 2017. This data from the Canadian Institute for Health Information was collected in all Canadian jurisdictions except one. The Canadian Institute for Health Information uses the Canadian 10th revision of the International Statistical Classification of Diseases and Related Health Problems for diagnoses and the Canadian Classification of Health Interventions for coding procedures. Patient demographics, preexisting medical conditions, obstetric complications, and potential etiologies of anesthesia-related complications were included in the calculations. Pre-existing medical conditions and obstetric conditions were assessed and selected by 2 study authors with specialty training in obstetric anesthesia.
Statistical calculations included univariate linear regression for annual adverse event rates, anesthesia interventions, and delivery method with a robust sandwich estimator for standard errors; multivariate logistic regression adjusted for demographics for associations between hospitalizations with anesthesia complications and patient characteristics, delivery method, and modality of anesthesia; and multivariate logistic regression adjusted for equivalent covariates for associations between anesthesia complications and obstetric and pre-existing medical conditions. The study utilized SPSS for analyses.
Of the 3,194,875 anesthesia interventions, there were 8361 events in 8130 hospitalizations that had anesthesia-related adverse events (0.3%, average annual incidence 262 events per 100,000 interventions, 95% CI, 256-267). Complications were significantly lower in neuraxial anesthesia procedures compared with general plus neuraxial anesthesia and general anesthesia. Neuraxial anesthesia adverse events occurred in 255 per 100,000 neuraxial anesthesia administrations (95% CI, 219-230). Annual incidence decreased throughout the years. Postdural puncture headache was the most common cause (86%) of serious adverse events although they also decreased over time. General plus neuraxial anesthesia adverse event incidences remained constant over time, representing 1476 per 100,000 general plus neuraxial anesthesia administrations (95% CI, 1284-1689). Postdural puncture headache represented 50% of the adverse events. General anesthesia adverse event incidence also remained constant over time, representing 488 per 100,000 general anesthesia administrations (95% CI, 438-542). Failed or difficult intubation was the most common cause of serious adverse events occurring in 88 of 135 (65%) serious adverse events.
Despite the increasing rate of obesity, advanced maternal age, and a higher incidence of many complications, anesthesia-related complications are decreasing likely secondary to the use of neuraxial anesthesia during labor, the use of neuraxial anesthesia during Cesarean delivery, and the use of dilute local anesthetic solutions during labor. Anesthesia-related adverse events reduced significantly over time from 327 to 222 per 100,000 (95% CI, 10 to −4; P<0.001) while total anesthesia intervention use increased. Risk factors for adverse outcomes include cardiomyopathy, obesity, eclampsia, and asthma.
In conclusion, during this 13-year study period one in 382 anesthetic interventions and one in 311 delivery hospitalizations was associated with an anesthesia-related adverse event. The incidence of these events decreased over time. Difficult intubation was the most common adverse event related to general anesthesia. Postdural puncture headache was the most common adverse event related to neuraxial anesthesia. This study recommended a variety of future steps including the creation of a national obstetric anesthesia or a serious complication registry.
Editorial to accompany article by Baghirzada et al above