Key result
An end-tidal CO2 reduction >15% during aortic cross-clamping predicted a systolic arterial pressure decrease >20% after unclamping with 100% sensitivity and 100% specificity.
Why the study?
Does end-tidal CO2 variation during aortic cross-clamping predict unclamping hypotension in patients undergoing infrarenal aortic abdominal aneurysm repair?
Observational (n=33)
Does end-tidal CO2 variation during aortic cross-clamping predict unclamping hypotension in patients undergoing infrarenal aortic abdominal aneurysm repair?
Monitoring end-tidal CO2 variation during aortic cross-clamping provides a highly sensitive and specific non-invasive method to predict unclamping hypotension during abdominal aortic aneurysm repair.
Answers are grounded in this paper and cite their sources.
EtCO2 monitoring may anticipate unclamping hypotension; leaves open validation and outcome impact in larger cohorts.
BACKGROUND: To assess the variations in end-tidal CO2 in response to aortic cross-clamping and the relationship with systolic arterial pressure (SAP) changes induced by unclamping. METHODS: Thirty-three patients undergoing infrarenal aortic abdominal aneurysm repair by aorto-aortic prothetic bypass were prospectively studied. All patients were anesthetized with i.v. midazolam (0.05 mg x kg(-1)), thiopentone (3-5 mg x kg(-1)), fentanyl (5 microg x kg(-1)), pancuronium (0.1 mg x kg(-1)) and the maintainance of anesthesia used was 1-1.5% end-tidal isoflurane and i.v. fentanyl. The perioperative management was standardized. End-tidal CO2 and SAP were measured 5 min before (Pre-XAA), 15 min after infrarenal aortic cross-clamping (XAA), 5 min before (Pre-UXAA) and immediately after unclamping (UXAA). RESULTS: A total of 16 (48.5%) from 33 patients presented decrease in SAP following aortic unclamping, and 13 out of these patients had arterial hypotension defined as SAP<90 mmHg. End-tidal CO2 variation (PreXAA-PreUXAA) induced by aortic clamping was correlated with SAP variation (PreUXAA-UXAA) induced by unclamping (r=0.763; P=0.0001). An end-tidal CO2 reduction above 15% after aortic cross-clamping was found to have a 100% sensitivity to detect a SAP decrease greater than 20% after unclamping, with a 100% specificity and a negative predictive value of 1.0. Complete aortic occlusion duration was not correlated to SAP unclamping variation (deltaSAP). Intraoperative characteristics (fluid loading, hematocrits, urinary output) were comparable, although blood loss was higher in patients experiencing deltaSAP>20%. CONCLUSIONS: End-tidal CO2 variation monitoring during aortic cross-clamping may provide a reliable and non-invasive method to predict unclamping hypotension. When the aortic clamp was released, systolic hypotension (>20%) occurred in those subjects who had a decrease in end-tidal CO2 greater than 15% during aortic cross-clamping.
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Boccara et al. (2001) conducted an observational in Infrarenal aortic abdominal aneurysm (n=33). End-tidal CO2 monitoring was evaluated on Correlation between end-tidal CO2 variation induced by aortic clamping and systolic arterial pressure variation induced by unclamping (r=0.763, p=0.0001). An end-tidal CO2 reduction >15% during aortic cross-clamping predicted a systolic arterial pressure decrease >20% after unclamping with 100% sensitivity and 100% specificity.
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