Spinal Anaesthesia Success: An Observational Study Assessing Subjective Sensations During Spinal Anaesthetic Drug Injection

Abstract

Introduction: Spinal Anaesthesia (SA) has stood as the most favoured and dependable technique in regional anaesthesia for the past century. However, despite its widespread use, there are instances of occasional SA failure. Currently, there is no straightforward, cost-effective, and easily administered real-time test-aside from the positive aspiration of Cerebrospinal Fluid (CSF)-that can reliably confirm the deposition of local anaesthetic in the subarachnoid space. Aim: To evaluate the predictive value of subjective sensations (warmth/tingling/numbness) during the administration of SA for enhancing success rates. Materials and Methods: A prospective observational study preceeded the recruitment of 500 patients for this investigation. Following the confirmation of CSF aspiration upon injecting the SA drug, Bupivacaine, patients were queried about the sensations of warmth and/or tingling numbness in the lower limb, saddle part, and inner thighs. This assessment was conducted at 30 seconds and one minute after injection. Additionally, patients were asked to report any increase in the area and/or intensity of these sensations. The adequacy of SA was determined by achieving a sensory block upto the desired dermatome level and reaching a Bromage scale score of IV. Evaluations were performed at two minutes, five minutes, 10 minutes, and 15 minutes from the initiation of SA. Results: The population, predominantly ASA Class-I (60%) and II (40%), exhibited a median age of 45 years, with 54% being male. Intraoperative vital signs, including Heart Rate (HR), Systolic Blood Pressures (SBP), and Diastolic Blood Pressures (DBP), showed a consistent declining trend post-SA administration. Efficacy assessments revealed that Bromage Grade-IV was achieved in 99% of patients at 15 minutes. Notably, subjective sensations of warmth, tingling, and/or numbness proved to be robust predictors of successful SA, with a 218-fold increased likelihood. The diagnostic model demonstrated a high sensitivity of 98%, specificity of 85%, and a Positive Predictive Value (PPV) exceeding 99%. Conclusion: This study highlights the crucial role of warmth, tingling, and numbness as reliable indicators for successful SA, supported by a robust 97% success rate. Incorporating these patient-reported sensations in assessments provides a practical and accessible approach to improve the efficacy of SA procedures.