Review

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The effect of intraoperative cerebral oxygen desaturations on postoperative cerebral oxygen metabolism in neonates and infants a pilot study

Pediatric Anesthesia

Submitted June 2024 by Dr Laura Panizza

Read by 87 Journal Watch subscribers

Summary:

This study by Jock et al assessed the effect of intraoperative cerebral oxygen desaturation on postoperative cerebral oxygen metabolism in neonates and infants undergoing non-cardiac surgery (1). It is a prospective single-centre pilot study from Germany and was published in Pediatric Anesthesia in 2024.

Thirty-seven neonates and infants undergoing general anaesthesia for greater than 30 minutes and necessitating invasive arterial blood pressure monitoring were enrolled. A non-invasive device called Oxygen-to-See (O2C), which combines laser Doppler flowmetry and white-light spectrometry, was placed over the right forehead to continuously measure regional blood flow. Cerebral fractional tissue oxygen extraction (cFTOE) and approximated cerebral metabolic rate of oxygen (aCMRO2) were derived from this and used as markers for cerebral oxygen metabolism. Monitoring occurred from prior to induction until one hour postoperatively.

Seventeen (46%) of the 37 neonates and infants had regional cerebral oxygen desaturation of below 20% of their baseline – this group was defined as the event group. cFTOE and aCMRO2 were significantly higher and cerebral regional oxygen saturation was significantly lower post-operatively in the event group as compared with the non-event group.

Commentary:

We already know cerebral oxygen desaturation occurs in neonatal and infant anaesthesia. An international multicentre observational study used near-infrared spectroscopy (NIRS) to measure regional cerebral oxygenation and reported incidences of mild (11-20% below baseline), moderate (21-30% below baseline), and severe (greater than 30% below baseline) intraoperative cerebral deoxygenation of 43%, 11%, and 2% respectively in infants aged less than 6 months.2 Jock et al’s article is the first to describe the effect of intraoperative cerebral oxygen desaturations on postoperative cerebral oxygen metabolism in noncardiac paediatric surgical patients, although similar studies have been performed in paediatric cardiac surgery.

Jock et al suggest that an increased aCMRO2 could indicate an increased cerebral oxidative energy metabolism due to repair processes. They found even short moderate cerebral desaturations were associated with higher postoperative cFTOE and aCMRO2 values. Although this study purports cFTOE and aCMRO2 as possible indicators for poor neurological outcome, the more tangible outcome of post-operative neurological function was not measured. The authors did not measure cerebral oxygenation beyond one hour postoperatively so could not comment at which point cerebral oxygenation returns to baseline, although studies in paediatric cardiac surgery have shown a normalisation after 24-48 hours. (3,4)

All patients were ASA 3 and 4, which is likely why there was a higher proportion of patients with intraoperative cerebral deoxygenation below 20% of baseline than Olbrecht et al (2). It is unclear if these results should be extrapolated to our ASA 1 and 2 neonates and infants. The event group had patients who were younger, had lower body weight, and had a higher proportion of thoracic surgery, and although these differences were not statistically significant they may be considered clinically significant by paediatric anaesthetists.

The authors did not postulate what caused cerebral oxygen desaturation, although they did measure some potential contributors including arterial oxygen saturation, arterial partial pressure of carbon dioxide (PaCO2), blood pressure, and temperature. Haemoglobin, anaesthetic medications, and depth of anaesthesia were not documented in this study. Cerebral desaturations were associated with lower arterial pressures, suggesting that adequate blood pressure should be maintained intraoperatively. There remains however a lack of a consensus definition for intraoperative hypotension in paediatric anaesthesia. NIRS and O2C may become useful in determining target blood pressures in neonates and infants in future. The study did not analyse the effect of hyperventilation on cerebral desaturation.

In summary, Jock et al have concluded that cerebral oxygen desaturation during major surgery in ASA 3 and 4 neonates and infants is associated with early postoperative increased cerebral oxygen extraction and possibly increased cerebral oxygen metabolism, which could indicate an elevated oxidative energy metabolism in the “stressed” brain.

References:

1. Jock A, Neunhoeffer F, Rorden A, et al. The effect of intraoperative cerebral oxygen desaturations on postoperative cerebral oxygen metabolism in neonates and infants a pilot study. Pediatr Anesth. 2024;34:138-144.
2. Olbrecht VA, Skowno J, Marchesini V, et al. An international, multicenter, observational study of cerebral oxygenation during infant and neonatal anesthesia. Anesthesiol. 2018;128(1):85-96.
3. Neunhoeffer F, Michel J, Nehls W, et al. Perioperative Assessment of cerebral oxygen metabolism in infants with functionally univentricular hearts undergoing the bidirectional cavopulmonary connection. Pediatr Crit Care Med. 2019;20(10):923-930.
4. Neunhoeffer F, Hofbeck M, Schlensak C, Schuhmann MU, Michel J. Perioperative cerebral oxygenation metabolism in neonates with hypoplastic left heart syndrome or transposition of the great arteries. Pediatr Cardiol. 2018;39(8):1681-1687.

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