This prospective, interventional, single-blinded, randomized controlled trial was conducted after obtaining approval from the institutional ethics committee and was registered with the Clinical Trial Registry of India. The study involved 138 patients classified as American Society of Anesthesiologists (ASA) physical status I-II, aged 18–60 years, with a Mallampati score of I or II. Patients scheduled for elective surgical procedures under general anesthesia, requiring single-attempt oral intubation via direct laryngoscopy, were included. Exclusion criteria encompassed patient refusal, inability to provide valid consent, pregnancy, known hypersensitivity to lignocaine, anticipated difficult airway, video laryngoscope-assisted intubation, and restricted neck mobility. Written informed consent was obtained from all participants. The patients were recruited between the periods from 21st June 2023 to 20th April 2024. The study adhered to the principles of the Helsinki Declaration 2013 and followed good clinical practices.
Patients were randomized into two groups using a computer-generated randomization chart: the intravenous group (Group IV) and the transtracheal group (Group TT). Baseline vitals were recorded in the preoperative holding area.
A standardized anesthesia protocol was followed for all patients. In the operating room, intravenous access was secured, and standard ASA monitors were attached. Ringer lactate was initiated intravenously at a rate of 2 ml/kg/hr. Patients were pre-oxygenated with 100% oxygen at 10 L/min for 3 minutes. General anesthesia was induced using fentanyl 2 µg/kg, propofol 2-2.5 mg/kg, and atracurium 0.5 mg/kg. Hypotensive episodes were treated with a 3 mg intravenous bolus of mephentermine. Mechanical ventilation was used to maintain normocapnia, with a tidal volume of 6–8 ml/kg ideal body weight and positive end-expiratory pressure (PEEP) of 5 cm H2O.
In Group IV, patients received preservative-free 2% lignocaine (Loxicard® 2%, Neon Laboratories Ltd, India) at 1.5 mg/kg intravenously immediately after induction. Three minutes post-administration, tracheal intubation was performed orally with an appropriate-sized endotracheal tube using a Macintosh laryngoscope in a single attempt.
In Group TT, patients received preservative-free 2% lignocaine (Loxicard® 2%, Neon Laboratories Ltd, India) at 1.5 mg/kg transtracheally immediately after induction. With the patient in a head-extended position, the cricothyroid membrane was identified and punctured perpendicularly using a 22 G needle attached to a 5 ml syringe loaded with the drug. Aspiration of air confirmed needle placement and the drug was instilled into the trachea. After 3 minutes of transtracheal injection of lignocaine, the trachea was intubated orally with an appropriate-sized endotracheal tube using a Macintosh laryngoscope in a single attempt.
Heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean blood pressure (MBP) were measured prior to intubation, immediately post-intubation, and at 1, 3, and 5 minutes post-intubation. The duration of laryngoscopy and intubation was recorded for both groups. General anesthesia was maintained with 50% nitrous oxide in oxygen each at 3 L/min and sevoflurane at a 2% dial concentration. After five minutes, routine anesthesia protocols were resumed, and surgical preparation commenced. The incidence of sore throat was noted in both groups once the patients were shifted to the recovery room.
The sample size was calculated using the UCSF-CTSI (University of California San Francisco Clinical and Translational Science Institute) online calculator [9], assuming a 5 mm Hg difference in mean of blood pressures between the two groups, with a standard deviation of 10 mm Hg, a 95% confidence interval, and 80% power. This resulted in a requirement of 63 patients per group. With an anticipated 10% attrition rate, the total sample size was adjusted to 138 patients.
Statistical analyses were performed using Jupyter Notebook [10] running in a Python 3.11 environment. The Shapiro–Wilk test was used to assess the normal distribution of continuous data. Non-normally distributed continuous and ordinal data were analyzed using the Wilcoxon rank-sum test, while normally distributed continuous data were analyzed using the two-tailed Student's t-test. The Chi-square test was used for categorical data. A p-value of < 0.05 was considered statistically significant. A post hoc power and sample size analysis was conducted to validate the findings.