Preoperative Fluid Fasting Times and Postinduction Low Blood Pressure in Children: A Retrospective Analysis
Summary by Michelle Adamczyk, 9.1.23
https://pubs.asahq.org/anesthesiology/article/133/3/523/108227/Preoperative-Fluid-Fasting-Times-and-Postinduction
Article: Preoperative Fluid Fasting Times and Postinduction Low Blood Pressure in Children: A Retrospective Analysis
Clinical Hypothesis: Prolonged fasting before elective general anesthesia in pediatric patients causes volume depletion, manifested as low blood pressure
Take Home Message:
For pediatric patients, fasting for longer periods of time (4-8 hours, >12 hours) increases risk of hypotension during surgical preparation time by 30%
For pediatric patients receiving inhalational anesthesia for induction, 5% experience hypotension during induction of anesthesia and 7% experience hypotension during surgical preparation
Summary:
Background:
Patients fast before elective surgeries to allow time for elimination of gastric contents and reduce risks of emesis and aspiration of gastric contents. Pediatric hospitals are sometimes more liberal with fasting guidelines, particularly for clear fluids- given excessively long pre-operative fasting can cause patients discomfort throughout hunger, headaches, etc. In addition, previous studies have suggested that more strict fasting guidelines are associated with lower blood pressures in infants and young children (<36 months). This retrospective study evaluated the relationship between length of pre-operative fluid fasting time and occurrence of hypotension during anesthesia induction and preparation time and during post-induction surgical preparation time for children undergoing elective surgery.
Study Design: Retrospective cohort study
Methods:
Inclusion criteria: ASA I-IV patients, <18 years old, recorded data of last clear fluid intake
Exclusion criteria: Inpatients, patients undergoing surgery in the cardiothoracic suite, patients undergoing general anesthesia multiple times within the study period, patients with congenital heart defects, patients with ASA status of V/E, patients who received IVF during the fasting period, patients with IV access in pre-op
Primary outcome: Low systolic blood pressure (initially defined as SBP more than 20% below baseline, but changed to pediatric normograms specific to age and sex)
Secondary outcome: None
Results: 8.3% of all patients included in the study had a low SBP event during the course of their anesthesia and/or surgical preparation time post-induction. There was no association found between fluid fasting time and hypotension during the time between anesthesia induction and completion of anesthesia preparation. However, there was an increased rate of hypotension during surgical preparation time associated with longer periods of fluid fasting preoperatively, with statistically significant higher rates of hypotension in patients who fasted 4-8 hrs and >12hrs and numerically higher but not statistically significant hypotension in 8-12 hrs, compared to the group who fasted <4 hrs. The odds of hypotension was a nonlinear relationship.
Discussion/conclusion:
While there was a nonlinear relationship, there was overall evidence that prolonged clear fluid fasting was associated with increased events of hypotension for anesthetized children, especially in the window of time after anesthesia induction and preparation for surgery, but before surgical incision. This study does not measure more specific clinical outcomes such as end organ perfusion. This study aims to continue further discourse regarding clinical consequences of optimal clear fluid fasting times for pediatric patients before surgery, and balancing concern for gastric emptying and aspiration risk vs. patient comfort.