Preventing Post-induction Hypotension During General Anaesthesia: A Dose-Response Study of Ringer's Lactate Guided by the Inferior Vena Cava Collapsibility Index.

Introduction Post-induction hypotension (PIH) is a frequent and serious complication during general anesthesia (GA), leading to adverse outcomes like myocardial injury and acute kidney injury. Current methods for assessing preoperative volume status are often unreliable or invasive. Ultrasonography-guided Inferior Vena Cava Collapsibility Index (IVCCI) offers a non-invasive alternative for predicting fluid responsiveness. While IVCCI-guided fluid loading effectively prevents spinal anesthesia-induced hypotension, its role and the optimal Ringer's lactate (RL) dose in GA patients remain unclear. This study aimed to determine the optimal intravenous RL dose to prevent PIH, guided by IVCCI. Methods This prospective, randomized, interventional study enrolled 88 adult patients with American Society of Anesthesiologists (ASA) physical status I/II undergoing elective general surgery at Tata Main Hospital, Jamshedpur, India, from July 2023 to August 2024. Participants with an IVCCI ≥ 40% were randomized into two groups: Group A received 10 ml/kg of RL, and Group B received 15 ml/kg of RL, both administered over 30 minutes before anesthesia induction. Hemodynamic parameters, including heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP), were monitored at predefined intervals following induction of anesthesia. Hypotension was defined as a >30% fall in MAP from baseline or MAP < 60 mmHg, with mephentermine administered as needed. Statistical analysis used t-tests, Mann-Whitney U-tests, and chi-square tests. Results The 88 participants were demographically comparable across both groups. While the mean inferior vena cava (IVC) maximum values were similar, Group B showed a significantly higher mean IVCCI (48.1% vs. 43%; p < 0.001) compared to Group A, despite receiving more fluid. Post-induction, heart rate remained comparable. However, Group B consistently maintained significantly higher SBP, DBP, and MAP at multiple time points compared to Group A. Notably, four patients in Group A (10 ml/kg RL), all with pre-existing hypertension, required mephentermine for a >30% fall in SBP, whereas no patients in Group B (15 ml/kg RL) required vasopressor intervention. Conclusion The study reinforces the challenge of PIH and the utility of IVC ultrasound in assessing fluid status. It found that a higher dose of RL (15 ml/kg) was more effective in preventing PIH than 10 ml/kg, as evidenced by better-maintained SBP, DBP, and MAP and the complete absence of vasopressor requirements in the higher-dose group. The significant IVCCI difference between groups, despite higher fluid in Group B, suggests a greater baseline fluid responsiveness in this group. These findings suggest that 15 ml/kg of pre-induction RL, guided by IVCCI, improves hemodynamic stability, particularly beneficial for hypertensive patients, advocating for an individualized, dynamic fluid management strategy.