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The effect of cardiopulmonary bypass on cholinesterase activity
1University Department of Anaesthesia, Royal Liverpool University Hospital.
Insights
Cardiopulmonary bypass significantly reduces cholinesterase activity by approximately 60% in patients, regardless of hypothermic or normothermic conditions. Activity levels remained low for 7 days post-surgery before gradually recovering.
Area of Science:
- Biochemistry
- Anesthesiology
- Cardiovascular Surgery
Background:
- Cholinesterase activity is crucial for neurotransmission.
- Cardiopulmonary bypass (CPB) is a complex procedure with potential systemic effects.
- The impact of CPB on cholinesterase levels requires further elucidation.
Purpose of the Study:
- To investigate the changes in cholinesterase activity in patients undergoing hypothermic versus normothermic cardiopulmonary bypass.
- To determine the temporal profile of cholinesterase activity recovery post-CPB.
Main Methods:
- Cholinesterase activity was measured in 18 patients (9 hypothermic, 9 normothermic) undergoing CPB.
- Blood samples were collected pre-anesthesia, during CPB, and up to 7 days postoperatively.
- Activity was also assessed at 6 weeks in six patients; all had normal cholinesterase genotypes.
Main Results:
- A significant reduction of approximately 60% in cholinesterase activity was observed at the start of CPB in both groups (p < 0.001).
- Reduced cholinesterase activity persisted for at least 7 days postoperatively.
- No significant difference in cholinesterase activity was found between hypothermic and normothermic CPB groups at any time point.
Conclusions:
- Cardiopulmonary bypass induces a profound and sustained decrease in cholinesterase activity.
- Hypothermia during CPB does not appear to differentially affect cholinesterase activity compared to normothermia.
- Cholinesterase activity recovers to near baseline levels by 6 weeks post-CPB.
Abstract:
Cholinesterase activity was determined in 18 patients who had undergone either hypothermic (n = 9) or normothermic (n = 9) cardiopulmonary bypass. The anaesthetic technique was standardised to avoid agents known to affect cholinesterase. Activity was determined in blood samples taken before the induction of anaesthesia, during cardiopulmonary bypass and for at least 7 days postoperatively. In six patients cholinesterase activity was also measured at 6 weeks postoperatively. All the patients were of normal cholinesterase genotype. In both groups cholinesterase activity fell by approximately 60% coinciding with the start of cardiopulmonary bypass, from a mean of 5976 to 2636 IU.l-1 in the hypothermic group, and from 5901 to 2615 IU.l-1 in the normothermic group (p < 0.001 in both instances) (normal range 4300-10,500 IU.l-1). Cholinesterase activity remained at this reduced level for at least 7 days postoperatively. By 6 weeks, activity had returned to within 7% of pre-induction values. There were no differences in cholinesterase activity between the hypothermic and normothermic groups at any of the sampling times.