Assessment of Ultrasonographic Measurement of Inferior Vena Cava Collapsibility Index in the Prediction of Hypotension Associated with Tourniquet Release in Total Knee Replacement Surgeries under Spinal Anesthesia
Authors: Mohammed Abdelfattah Ahmed Magdy Mohammed , Ali Sultan Sherif Sayed , Abdelmotaleb Ammar Mona Ahmed , Fouad Dawla Mohammed Farouk 
Published: July 2024

Abstract

This was a Prospective, observational study conducted on 60 patients with Total Knee Replacement (TKR); to characterize the collapsibility index of the IVC as a potential screening tool to identify patients who are candidate for hypotensive events after tourniquet release in TKR in an otherwise hemodynamically stable population.
We found that; the mean age of all patients was (57 ± 5.6) years. Regarding gender of the patients, (58.3%) of patients were females; while (41.7%) were males.
Regarding basic clinical data; the mean BMI of all patients was (25.7 ± 2.5); with (60%) of patients had DM, and (56.7%) had HTN.
Regarding ASA class, (3.3%) had class I, (73.3%) had class II, and (23.3%) had class III.
Regarding Baseline hemodynamic data; the average MAP was (104.6 ± 6) mmHg, the average RR was (10.5 ± 1.3) breath/min, and the average HR was (74.75 ± 7) beat/min.
Regarding Data before tourniquet release; the average MAP was (102.3 ± 7.5) mmHg, the average RR was (10.7 ± 1.2) breath/min, and the average HR was (75.3 ± 6.5) beat/min, with average IVC-CI of (48.4 ± 7.7).
Regarding Data 15-m after tourniquet release; the average MAP was (93.1 ± 9.3) mmHg, the average RR was (10.7 ± 1.4) breath/min, and the average HR was (76.45 ± 6.6) beat/min, with average IVC-CI of (51 ± 8.4).
Regarding final outcome, (11.7%) of patients suffered Hypotension (PTRH).
The 60 TKR patients were classified according to outcomes into 2 independent groups: group A IVCCI &gt;55,5% (12 patients) and group B IVCCI &lt;55,5% (48 patients).
Regarding comparative study between the 2 groups as regards demographic data; no statistically significant differences were found except for ASA physical status of patients where group A had patients in ASA I class and most of its patients are ASA II while group B had no patients in ASA I class and a quarter of its patients were ASA III.
Regarding comparative study between the 2 groups as regards hemodynamic and ultrasonographic data; no statistically different results were noted between groups in baseline readings. Results recorded before tourniquet release showed that IVC during inspiration reading was statistically lower while IVC collapsibility index was statistically higher in Group A when compared with group B . Results recorded 15 min after tourniquet release showed that IVC during inspiration reading was statistically lower while IVC collapsibility index was statistically higher in Group A when compared with group B, the IVC-CI before tourniquet release was not correlated with percent reduction in systolic blood pressure after tourniquet release in both groups with high (Group A) or low IVC-CI (Group B).
Comparing patients who developed hypotension versus patients who did not, the 60 TKR patients were classified into hypotensive (7 patients) and normotensive (53 patients) groups.
No statistically significant differences were found between hypotensive versus normotensive patients concerning demographic data and data recorded before tourniquet release. Baseline data showed significantly higher respiratory rate in hypotensive patients. Data recorded 15 min after tourniquet release showed statistically lower SBP, DBP and MAP, significantly higher HR and significantly lower IVC during inspiration and expiration in patients who developed hypotension.
We studied different factors that may be included before tourniquet release that may predict the degree of PTRH by using ROC-curve analysis. IVC-CI before tourniquet release and BMI failed to be predictive factors for the occurrence of PTRH, while respiratory and heart rates before tourniquet release significantly predict the occurrence of PTRH.
Performing multiple regression analysis using forward method showed that the increase in RR had an independent effect on increasing the probability of PTRH occurrence; with significant statistical difference (p &lt; 0.039).

Conclusion
IVC-CI before tourniquet release is not a predictor for PTRH in patients undergoing TKR under spinal anesthesia.