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Peer-reviewedCC BY 4.0Anesthesiology Research and Practice

Effects of Permissive Hypercapnia Versus Normocapnia on Cerebral Oxygenation and Postoperative Outcomes in Adult Surgical Patients: A Systematic Review and Meta‐Analysis

  • Areej Riaz1
  • Amna Khan2
  • Fatima Nawaz3
  • Amna Shafaqat3
  • Hadia Sheraz4
  • Mohammed M. AlTelbany5
  • Nauroze Khan6
  • Adeel Ahmed Khan7
  • Bismah Rafique Malik8
  • Hermann Yokolo9
9 affiliations
  1. 1Department of Medicine Services Institute of Medical Sciences Lahore Pakistan sims.edu.pk
  2. 2Department of Medicine Ameer-ud-Din Medical College Lahore Pakistan duhs.edu.pk
  3. 3Department of Medicine University of Health Sciences Lahore Pakistan uhs.edu.kh
  4. 4Department of Medicine FMH College of Medicine and Dentistry Lahore Pakistan duhs.edu.pk
  5. 5Faculty of Medicine Al-Azhar University Gaza State of Palestine azhar.edu.eg
  6. 6Department of Medicine Pakistan Institute of Medical Sciences Islamabad Pakistan pims.gov.pk
  7. 7Department of Medicine Sindh Government Hospital Karachi Pakistan duhs.edu.pk
  8. 8Department of Medicine Dow University of Health Sciences Karachi Pakistan duhs.edu.pk
  9. 9Department of Research Medical Research Circle (MedReC) Goma Democratic Republic of the Congo
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Abstract

Background: Evidence suggests that intraoperative cerebral hypoxia is the main contributor of postoperative neurological complications, particularly postoperative cognitive dysfunction (POCD) and postoperative delirium (POD) in surgical patients. Permissive hypercapnia may improve cerebral oxygenation by increasing cerebral blood flow, but its perioperative benefits remain uncertain.

Research Question: In adult surgical patients, is permissive hypercapnia associated with improved cerebral oxygenation and perioperative outcomes compared with normocapnia?

Method: PubMed, Embase, Cochrane CENTRAL, and ClinicalTrials.gov were searched from inception to April 2026 for randomized controlled trials (RCTs) and cohort studies of adult surgical patients receiving permissive hypercapnia. Primary outcome included was intraoperative regional cerebral oxygen saturation (rSO2). Secondary outcomes were POCD, POD, all‐cause mortality, respiratory parameters, arterial blood gas variables, and hemodynamic outcomes.

Results: Seven studies comprising 824 patients were included. Permissive hypercapnia significantly improved intraoperative rSO2 (MD = 6.65%; 95% Cl: [4.93, 8.37]; p < 0.00001), PaCO2 (MD = 10.21 mmHg (95% CI: [8.81, 11.60]; p < 0.00001), and end‐tidal CO2 (MD = 10.83 mmHg; 95% CI [7.91, 13.76]; p < 0.00001), and significantly reduced dead space fraction (MD = −6.38%; 95% CI: [–9.26, −3.50], p < 0.00001), and arterial pH (MD = −0.08; 95% CI: [‐0.09, −0.07]; p < 0.00001). Hypercapnia had no significant effect on PaO2, mean arterial pressure, and heart rate. Qualitative analysis suggested reduced incidence of POCD with no significant effect on POD.

Conclusion: Permissive hypercapnia improves intraoperative cerebral oxygenation while maintaining hemodynamic stability. However, the available evidence for POCD and POD is limited and heterogeneous. Larger RCTs and observational studies are needed to confirm its effects on clinical outcomes before routine implementation.

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Cite

BibTeXRIS
BibTeX
@article{riaz2026effects,
  title = {{Effects of Permissive Hypercapnia Versus Normocapnia on Cerebral Oxygenation and Postoperative Outcomes in Adult Surgical Patients: A Systematic Review and Meta‐Analysis}},
  author = {Areej Riaz and Amna Khan and Fatima Nawaz and Amna Shafaqat and Hadia Sheraz and Mohammed M. AlTelbany and Nauroze Khan and Adeel Ahmed Khan and Bismah Rafique Malik and Hermann Yokolo},
  journal = {Anesthesiology Research and Practice},
  year = {2026},
  month = oct,
  doi = {10.1155/anrp/3569464},
  url = {https://doi.org/10.1155/anrp/3569464},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Effects of Permissive Hypercapnia Versus Normocapnia on Cerebral Oxygenation and Postoperative Outcomes in Adult Surgical Patients: A Systematic Review and Meta‐Analysis
AU  - Areej Riaz
AU  - Amna Khan
AU  - Fatima Nawaz
AU  - Amna Shafaqat
AU  - Hadia Sheraz
AU  - Mohammed M. AlTelbany
AU  - Nauroze Khan
AU  - Adeel Ahmed Khan
AU  - Bismah Rafique Malik
AU  - Hermann Yokolo
PY  - 2026
DA  - 2026/10/31
JO  - Anesthesiology Research and Practice
DO  - 10.1155/anrp/3569464
UR  - https://doi.org/10.1155/anrp/3569464
AB  - Background: Evidence suggests that intraoperative cerebral hypoxia is the main contributor of postoperative neurological complications, particularly postoperative cognitive dysfunction (POCD) and postoperative delirium (POD) in surgical patients. Permissive hypercapnia may improve cerebral oxygenation by increasing cerebral blood flow, but its perioperative benefits remain uncertain.  Research Question: In adult surgical patients, is permissive hypercapnia associated with improved cerebral oxygenation and perioperative outcomes compared with normocapnia?  Method: PubMed, Embase, Cochrane CENTRAL, and ClinicalTrials.gov were searched from inception to April 2026 for randomized controlled trials (RCTs) and cohort studies of adult surgical patients receiving permissive hypercapnia. Primary outcome included was intraoperative regional cerebral oxygen saturation (rSO2). Secondary outcomes were POCD, POD, all‐cause mortality, respiratory parameters, arterial blood gas variables, and hemodynamic outcomes.  Results: Seven studies comprising 824 patients were included. Permissive hypercapnia significantly improved intraoperative rSO2 (MD = 6.65%; 95% Cl: [4.93, 8.37]; p < 0.00001), PaCO2 (MD = 10.21 mmHg (95% CI: [8.81, 11.60]; p < 0.00001), and end‐tidal CO2 (MD = 10.83 mmHg; 95% CI [7.91, 13.76]; p < 0.00001), and significantly reduced dead space fraction (MD = −6.38%; 95% CI: [–9.26, −3.50], p < 0.00001), and arterial pH (MD = −0.08; 95% CI: [‐0.09, −0.07]; p < 0.00001). Hypercapnia had no significant effect on PaO2, mean arterial pressure, and heart rate. Qualitative analysis suggested reduced incidence of POCD with no significant effect on POD.  Conclusion: Permissive hypercapnia improves intraoperative cerebral oxygenation while maintaining hemodynamic stability. However, the available evidence for POCD and POD is limited and heterogeneous. Larger RCTs and observational studies are needed to confirm its effects on clinical outcomes before routine implementation.
SN  - 1687-6962
SN  - 1687-6970
ER  -