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Is pH-stat or alpha-stat the best technique to follow in patients undergoing deep hypothermic circulatory arrest?
Khairul Anuar Abdul Aziz1, Ayo Meduoye
1Department of Cardiothoracic Surgery, Glenfield Hospital, Leicester, LE3 9PQ, UK. anuar@doctors.net.uk
Insights
The best acid-base management during deep hypothermic circulatory arrest in cardiac surgery depends on patient age. pH-stat is preferred for pediatric patients, while alpha-stat is better for adults, optimizing cerebrovascular metabolism and outcomes.
Area of Science:
- Cardiac Surgery
- Cardiovascular Research
- Neuroanesthesia
Background:
- Deep hypothermic circulatory arrest (DHCA) is used in cardiac surgery.
- Acid-base management strategies (pH-stat vs. alpha-stat) are critical during DHCA.
- Optimal strategy for cerebrovascular metabolism and neurological outcomes remains debated.
Purpose of the Study:
- To determine the best acid-base management technique (pH-stat or alpha-stat) for patients undergoing DHCA in cardiac surgery.
- To evaluate the impact of these strategies on cerebrovascular metabolism and neuropsychological outcomes.
- To assess if patient age influences the efficacy of pH-stat versus alpha-stat.
Main Methods:
- Systematic review of 206 papers, focusing on 16 high-quality studies.
- Analysis of studies comparing pH-stat and alpha-stat for DHCA.
- Comparison of outcomes including cerebrovascular metabolism and neuropsychological status.
- Stratification of results based on patient age (pediatric vs. adult).
Main Results:
- Cerebrovascular metabolism: 6 studies favored alpha-stat, 3 favored pH-stat, 4 found no difference.
- Neuropsychological outcome: 3 studies favored alpha-stat, 3 favored pH-stat, 3 found no difference.
- Age-specific findings: pH-stat showed better outcomes in pediatric patients (3/4 studies), alpha-stat in adult patients (7/7 studies).
Conclusions:
- The optimal acid-base management strategy during DHCA in cardiac surgery is age-dependent.
- pH-stat is associated with better intraoperative and postoperative outcomes in pediatric patients.
- Alpha-stat is associated with better intraoperative and postoperative outcomes in adult patients.
Abstract:
A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether pH-stat or alpha-stat is the best technique to follow in patients undergoing deep hypothermic circulatory arrest. Altogether 206 papers were found using the reported search, of which 16 represent the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Excluding one paper which provided inconclusive results, six studies found better cerebrovascular metabolism with alpha-stat while three studies found better cerebrovascular metabolism with pH-stat. Four other studies showed no significant difference in the cerebrovascular metabolism between the two acid-base management strategies in patients undergoing deep hypothermic circulatory arrest. Nine studies compared the neuropsychological outcome in patients who underwent deep hypothermic circulatory arrest with three studies supporting each alternative conclusion of preference towards alpha-stat or pH-stat management. The remaining three studies showed no significant difference between the two groups of acid-base management. Comparing the 16 studies based on the age of the patients studied, three out of the four papers which demonstrated that the pH-stat method is a better strategy to improve intraoperative and postoperative outcome were based on a sample of paediatric patients. Conversely, all seven papers that suggested alpha-stat method is associated with better intraoperative and postoperative outcome were based on studies done on adult patients. The remaining four papers suggested no significant difference between the pH-stat group and alpha-stat group. In conclusion, there is evidence to suggest that the best technique to follow in the management of acid-base in patients undergoing deep hypothermic circulatory arrest during cardiac surgery is dependent upon the age of the patient with better results using pH-stat in the paediatric patient and alpha-stat in the adult patient.
