The role of caval aortic index in predicting spinal anesthesia-induced hypotension

Aim: In this prospective study, the aim was to predict the risk of hypotension by measuring the caval aorta index (CAI) under ultrasound guidance in patients undergoing spinal anesthesia, and to take preventive measures before hypotension occurs. Method: This study was conducted after obtaining approval from the Ethics Committee for Non-Interventional Studies of Dicle University Faculty of Medicine. A total of 32 patients aged between 18-65, who were scheduled for elective and emergency surgeries at Dicle University Hospital between July 1, 2024, September 31, 2024, were included in the study. Inclusion criteria were: patient consent to participate in the study, age between 18-65 years, American Society of Anesthesiologists (ASA) classification of I or II, and scheduled for elective or emergency surgery. Exclusion criteria were: refusal to participate, ASA classification of III or IV, known carotid artery stenosis, inability to visualize the IVC and/or abdominal aorta, pregnancy, patients under 18 or over 65 years, hypertension, high intra-abdominal pressure, Body Mass Index (BMI) over 30 kg/m², patients receiving unilateral spinal anesthesia, and patients with spinal anesthesia levels above T5. All patients were fasted according to standard protocol (6-8 hours for solids and 2 hours for clear fluids). Participants were informed about the study in detail, both verbally and in writing, and written informed consent was obtained from all. Patients were monitored in the premedication area with electrocardiogram (ECG), pulse, non-invasive arterial blood pressure (NIBP), peripheral oxygen saturation (SpO2), and body temperature. An intravenous (IV) access was established using a 20-gauge angiocatheter. Routine care was provided throughout premedication and surgery, without any additional interventions. Patients were scanned in a supine position using ultrasonography (USG) to identify the abdominal aorta (Aa) and inferior vena cava (IVC). The internal antero-posterior diameter of the abdominal aorta and IVC was measured using M-mode, approximately 10 mm above the celiac trunk on the long axis. The caval aorta index (CAI) was calculated using the formula: CAI = maximum inferior vena cava diameter (dIVC max) / maximum abdominal aorta diameter (dAa max). The value obtained before spinal anesthesia was accepted as the baseline. Blood pressure was measured before the administration of anesthesia, and 10-15 mg of 0.5% bupivacaine was administered for spinal anesthesia. Blood pressure measurements were taken every 5 minutes post-anesthesia. Hypotension was defined as a drop in mean arterial pressure (MAP) below 65 mmHg and/or a decrease of more than 30% from baseline. Severe hypotension (MAP <55 mmHg or >40% reduction) or prolonged hypotension (lasting ≥2 minutes) was treated with IV ephedrine boluses (3 mg). Severe bradycardia (HR <40 bpm) was treated with IV atropine (0.3 mg). Patients were divided into two groups: those who developed hypotension (Group 1, n=15) and those who did not (Group 2, n=17), and were evaluated accordingly. Results: A total of 32 patients were included in the study. The mean age was 34.0 ± 11.6 years, mean weight was 68.0 ± 12.2 kg, and mean height was 169 ± 8.35 cm. Of the patients, 56.25% (n=18) were male and 43.75% (n=14) were female. In Group 1, the mean CAI was 0.83 ± 0.14, while in Group 2, it was 1.09 ± 0.12. The difference between the groups was statistically significant (p < 0.001). Conclusion: This study evaluated the effectiveness of the caval aortic index (CAI) in predicting hypotension following spinal anesthesia. The findings suggest that a lower CAI significantly increases the risk of developing hypotension and that CAI is an effective parameter in maintaining hemodynamic stability. The non-invasive use of CAI in the preoperative period can improve perioperative fluid management and patient safety by reducing the risk of complications. Further research is needed to validate CAI across larger patient populations and different clinical settings. Preoperative calculation of CAI may contribute to the creation of personalized treatment plans based on individual patient risk factors. Keywords: : Inferior vena cava, Aorta, Hypotension, Anesthesia, Ultrasonography