INTRODUCTION

Hypotension following general anesthesia induction is a common and significant clinical event characterised by a sudden drop in blood pressure that can occur during or immediately after the administration of anaesthetic agents. Fluid deficit plays a crucial role in the incidence of post-induction hypotension. Studies have found that around 63 percentage of elderly patients may experience hypotension after induction which is a substantial percentage. Patients undergoing surgery particularly those fasting for extended periods may experience preoperative hypovolemia which increases the likelihood of hypotension during induction. Perioperative fluid management is pivotal in attenuating the risk of hypotension both during and following the induction of anaesthesia. Proper hydration can help maintain hemodynamic stability by counteracting the vasodilatory effects of anaesthetic agents and addressing any pre existing hypovolemia. 

Various studies have demonstrated that severe or prolonged hypotension following the induction of general anesthesia can lead to organ hypoperfusion and ischemia. As a result their condition increases the risk of adverse post-operative outcome such as myocardial injury ischemic stroke or acute kidney injury.

The population of elderly patients undergoing elective surgery has been progressively growing in recent years. Elderly patients often present with various cardiovascular conditions. Consequently these patients are more susceptible to experiencing hypotension following the induction of general anesthesia which poses an increased risk for anesthesia management.

Previous studies pointed out that peri-operative fluid therapy administered to surgical patients prior to induction effectively reduces occurrence of post induction hypotension. However elderly individuals are less tolerant to fluid overload and implementing peri operative fluid therapy may lead to fluid overload. 

In recent years the carotid corrected flow time measured in the carotid artery has emerged as a potential predictor of fluid responsiveness in both spontaneously breathing and mechanically ventilated patients.

Carotid corrected flow time FTc changes is a specific predictive marker that offers a technically simple reliable and non-invasive method for predicting blood volume without requiring arterial cannulation. It reflects the time taken for blood to flow through the carotid artery corrected for heart rate and provides valuable insights into a patients cardiovascular status and fluid responsiveness. FTc is influenced by stroke volume, cardiac output, and vascular tone, making it a useful indicator of the bodys fluid balance and circulatory function, especially in patients at risk of hemodynamic instability. 

Doppler waveform analysis of carotid artery is a novel strategy to predict fluid responsiveness in patients undergoing elective surgery. Studies have consistently shown that carotid artery FTc remains unaffected by respiration, making it a more dependable static parameter for predicting fluid responsiveness in spontaneously breathing individuals.

When FTc is decreased, it can indicate hypovolemia, whereas an adequate FTc suggest normal or proper hydration. Using FTc to assess fluid status before anaesthesia induction, clinicians can guide pre-hydration strategies to ensure patients are adequately hydrated, thereby reducing the risk of post induction hypotension. 

However, an effective method for accurately predicting post induction hypotension and preventing and preventing it in advance in clinical practice is still lacking.

NEED FOR THE STUDY

In elderly patients, the cardiovascular system often exhibits impaired autonomic regulation, decreased vascular responsiveness, and reduced baroreceptor sensitivity, making them more susceptible to perioperative hypotension. Consequently, ensuring optimal pre-hydration strategies becomes crucial to mitigate this risk. 

Previous studies have demonstrated that changes in carotid corrected flow time could predict fluid responsiveness and thus help guide fluid administration during surgery. Despite its potential, FTc is not widely studied or incorporated into routine clinical practice in India, especially for elderly patients undergoing surgery. This study could fill this gap by evaluating its practical applicability and effectiveness in the Indian population. 

PRIMARY OBJECTIVE 

To evaluate the efficacy of pre-rehydration guided by carotid corrected flow time FTc in reducing the incidence of hypotension following general anaesthesia induction in elderly patients

Proposed Methodology 

SUBJECTS 

Inclusion Criteria 

Exclusion Criteria

Detail the ACTUAL METHODOLOGY

After obtaining IEC approval and written informed consent, 100 elderly patients undergoing elective surgeries under general anaesthesia were allocated randomly by a computer-generated lot system into 2 groups. 

Group A  conventional treatment group 

Group B  fluid treatment group based on carotid FTc, further divided into two groups 

1. Group B1  carotid FTc less than 340.7 ms 4 mL per kg of Normal Saline is administered half an hour before the scheduled procedure in the pre-operative room. 

2. Group B2  carotid FTc more than 340.7 ms,  Patient shifted directly to OT without any further intervention. 

All patients will undergo a 6-hour fast for solids and a 4-hour fast for liquids. Perioperative intravenous fluid therapy with normal saline will be administered to all patients, with the volume calculated using the Holliday-Segar formula. Upon arrival in the pre-operative area, patients heart rate , and pulse oxygen saturation will be recorded. Carotid ultrasound Doppler would be employed to measure right side carotid FTc values. In Group A, the conventional treatment group, patients will be transferred directly to the operating theatre without any further intervention as we do routinely. In Group B, right side carotid FTc is measured, and this group will be further divided into two subgroups. In Group B1, where FTc less than 340.7 ms, 4 mL per kg of Normal Saline will be administered half an hour before the scheduled procedure in the pre-operative area. In Group B2, where carotid FTc is more than 340.7 ms, patients will be directly transferred to the OT without any additional intervention. 

After shifting the patient to the operation theatre, all patients will be monitored with standard pre-induction monitors such as NIBP, ECG, SPO2 and temperature. Pre-induction SBP, DBP, MAP and HR will be recorded. After adequate preoxygenation, patients in both groups will be premedicated with 0.03 mcg perkg of midazolam, 0.15mg per kg of Ondansetron and 0.2mg of glycopyrrolate. Patients will be induced with 1.5mg per kg of propofol at push rate of 40mg per 10sec, 2mcg per kg of fentanyl and endotracheal intubation will be facilitated with 0.5mg per kg of Inj Atracurium. Post Induction hypotension defined as an absolute MAP of less than 65 mmHg or a more than 20 percentage drop in MAP from the baseline preoperatively. MAP and BP is monitored for every 1 minutes for the first 5 minutes and then every 3 minutes for the next 10 minutes post-induction. The lowest recorded values of systolic blood pressure, diastolic blood pressure, mean arterial pressure, and HR after induction will be documented by non-invasive continuous blood pressure and electrocardiogram monitoring.