Prediction of post-spinal anaesthetic hypotension using USG

Post-spinal anaesthesia Hypotension (PSH) is one of the most often encountered complications of spinal anaesthesia. Hypotension is caused by a reduction in systemic vascular resistance (SVR) as a result of sympatholysis and a decrease in cardiac output (CO) as a result of decreased venous return. The inferior vena cava collapsibility index (IVCCI) and carotid artery peak systolic velocity variation (CAPVV) have been widely researched as indicators of fluid responsiveness in a variety of patient groups, most notably critically sick patients. The major purpose was to determine the predictive value of IVCCI and CAPVV for PSH. Recently published research attempted to examine the prediction power of these two measures and to identify other predictors of PSH.

The study comprised 50 patients aged 18 to 65 years who had elective lower abdomen operations under spinal anaesthesia. Preoperatively, the IVCCI and CAPVV were determined using ultrasonography. After spinal anaesthetic was administered, haemodynamic data were gathered for 15 minutes. Our major goal was to determine the predictive value of IVCCI and CAPVV for PSH. The secondary aims were to examine the predictive effectiveness of these two variables and to identify other variables associated with PSH prediction. The receiver operator characteristic (ROC) curves for IVCCI and CAPVV were generated and the optimal cut-off values were determined. PSH was detected in 34% of patients. IVCCI >21.15 had a sensitivity of 58.8 percent and a specificity of 69.7 percent for predicting PSH. CAPVV >18.33 indicated PSH with a sensitivity of 70.6 percent and specificity of 54.6 percent, whereas IVC max/IVCCI >60 predicted PSH with a sensitivity of 58.8 percent and specificity of 54.5 percent. PSH may be predicted using a composite model consisting of IVCmax (maximum IVC diameter), CAPVV, and baseline mean blood pressure.

In adult patients receiving elective infra-umbilical surgery, neither IVCCI nor CAPVV was able to predict PSH. PSH may be predicted using IVCmax, CAPVV, and baseline MBP. While the fundamental mechanism of PSH is a pre-ganglionic sympathetic block induced by local anaesthetics, it is not explained by reduced pre- or after-load. PSH has a complex pathophysiology that involves the circulatory effects of local anaesthetics, relative adrenal insufficiency, skeletal muscle paralysis, ascending medullary vasomotor block, and concomitant respiratory insufficiency. That is presumably why the techniques that have been useful in predicting fluid responsiveness in other circumstances are ineffective for predicting Post-spinal anaesthesia Hypotension.

However, the findings of this study should be taken cautiously, and more research with bigger sample sizes is recommended, especially in older individuals and those with pre-existing cardiovascular disease.

Reference -

Chowdhury, Sumit R.; Baidya, Dalim K.; Maitra, Souvik; Singh, Akhil K.; Rewari, Vimi; Anand, Rahul K., Assessment of role of inferior vena cava collapsibility index and variations in carotid artery peak systolic velocity in prediction of post-spinal anaesthesia hypotension in spontaneously breathing patients: An observational study, Indian Journal of Anaesthesia: February 2022 - Volume 66 - Issue 2 - p 100-106

doi: 10.4103/ija.ija_828_21