The strongest predictor of anesthesia-related cardiac arrest in the POCA study was ASA physical status of 3 to 5; such status was associated with a 12-fold increase in the odds of cardiac arrest. ASA physical status as a predictor of increased risk is also supported by data from other studies.

Emergency surgery was associated with a three-fold increase in risk for cardiac arrest in the POCA study, as well as with
an increased risk of other anesthetic complications in a landmark French study.

The risk of anesthetic complications and cardiac arrest in children varies inversely with age. Neonates and infants are particularly at risk. Approximately 50% of all arrests in the POCA registry occurred in infants (<1 year of age), and 15% occurred in neonates (<1 month of age). Of note, however, is that when underlying disease severity was accounted for (i.e., ASA status), age alone was not a predictor of death in the POCA study.

Of the 150 cases of cardiac arrest submitted to POCA, 37% were related to medication. Two thirds were likely due to halothane, alone or in combination with other drugs. Medications were also deemed responsible for 64% of arrests in patients whose ASA physical status was 1 or 2. Based on the analysis of an additional 163 anesthesia-related cases added to the registry, medication-related causes declined from 37% to 20%, primarily due to a decline in cardiac depression induced by volatile agents. Cardiovascular causes of arrest are now the most common, increasing from 32% to 36%. In this category, hypovolemia (frequently due to hemorrhage) and hyperkalemia (secondary to massive transfusion) were the most frequent causes of arrest. Respiratory causes increased from 20% to 27%, with laryngospasm, airway obstruction, inadvertent extubation, difficult intubation, and bronchospasm being the most frequent events. Equipment-related arrests (4%) were commonly due to complications of central-venous-pressure (CVP) catheter placement. Assorted other causes included complex cyanotic congenital heart disease, pulmonary hypertension, myocarditis, prolonged QT syndrome, coronary artery disease, hypertrophic cardiomyopathy, topical vasoconstrictor use, and anaphylactic reactions.

The percentage of patients whose ASA physical status was 1 or 2 decreased from 33% in 1998 to 27% in 2003, along with the percentage of infants younger than 1 year of age (55% to 36%, p<0.05). The POCA investigators attribute the decline in medication-related arrests to these changes; halothane was often responsible for cardiac arrest in infants whose ASA physical status was 1 or 2. The mortality rate did not change significantly from 1998 to 2003 (26% in 1998, 28% in 2003), despite the altered profile of reported cases.