273 - Regional cerebral oxygenation changes during neonatal anesthesia

Neonatal anesthesia is a high risk procedure with sudden, unpredictable physiological changes occurring in 20-30% of the cases. Cerebral near infrared spectroscopy (NIRS) may be an important complimentary tool to standard monitoring, which can provide early warning sings of impaired tissue oxygenation (rSO₂); however, specific absolute rSO₂ thresholds are not available to guide management. Current recommendations suggest that rSO₂ values decreasing by 20% compared to baseline values may carry an increased risk, but the rate of this scenario is not known in the neonatal population.

Objective:

To describe changes in cerebral oxygenation during neonatal non-cardiac surgeries.

Design/Methods:

This was a prospective, observational study conducted in the operating room (OR) at the Department of Pediatrics, Semmelweis University. Synchronised high frequency time-series physiological data was collected from consecutive infants undergoing various types of non-cardiac surgery. The INVOS 5100C (Medtronic) with neonatal sensors was used for NIRS monitoring. Baseline rSO₂ data was registered before induction of anesthesia for each patient.  

Results:

Patient monitor and NIRS monitor data was collected real-time from a total of 25 patients, with median bodyweight 2.8 [1.9; 3.5] kg and 26.5 [5.0; 66.5] days postmenstrual age at the time of sugery. The most common types of surgeries were gastrointestinal and urinary tract surgeries. Median baseline NIRS values were 73% [min: 47,6%; max 92,7%]. One-third (8/25) of patients experienced more than 20% decrease in rSO₂ values during surgery. The average time spent 20% below baseline was 22 ± 19 minutes. Nadir rSO₂ values were median 59% [min: 15%; max 86%]. Conventionally monitored vital parameters have not always forewarn of low rSO₂. Peripheral oxygen saturation during rSO₂ nadir was normal, with a median 97 % [min: 76% ; max 100%]. Non-invasive blood pressure (BP) values were in the lower range (mean arterial pressure 40 mmHg [16; 74 mmHg]), whereas heart rate was 142 beat/min [min: 98; max 178 beat/min].  End-tidal CO₂ values during nadir rSO₂ were also in the lower range (31 mmHg [min: 14.5; max 50.5]).

Conclusion(s):

Undesired rSO₂ values were observed frequently during neonatal anesthesia, and these changes were not always coincident with extreme changes of regularly monitored vital parameters. The NIRS may be a useful addition to the neonatal monitoring setup in the OR.