Direct laryngoscopy and tracheal intubation are well-recognized stimuli for transient sympathetic activation, which can produce tachycardia and elevations in arterial blood pressure. Contemporary randomized evidence continues to evaluate pharmacologic strategies for attenuating these responses during general anaesthesia.¹

Lidocaine is an amide local anaesthetic with systemic actions extending beyond sodium-channel blockade, including antinociceptive and anti-inflammatory effects.² Perioperative intravenous lidocaine has also been

evaluated as part of multimodal analgesia and recovery pathways; current consensus guidance emphasizes both potential benefit and the need for careful dosing and safety oversight.³

Evidence suggests that intravenous lidocaine may reduce perioperative opioid requirements and improve some dimensions of postoperative recovery, although effect sizes vary across surgical populations.⁴ Its effect on the cardiovascular response to endotracheal intubation has also been investigated in randomized trials, with variable findings depending on dose, co-administered anaesthetic drugs and patient population.⁵

Other perioperative outcomes studied with systemic lidocaine include short-term cognitive outcomes, hemodynamic effects during induction in older adults, and responses to intubation in paediatric surgery.^6-8 Against this background, the present study compared intravenous lidocaine infusion with 0.9% isotonic saline in adults undergoing general anaesthesia, focusing primarily on serial MAP, SBP and HR responses around tracheal intubation, with peri-extubation respiratory events, PONV and postoperative analgesic demand as secondary outcomes.

Study design and setting This prospective randomized controlled study was conducted from 1 January 2024 to 30 June 2024 after approval from the Institutional Ethical Committee. Sixty patients from the Department of Surgery at PAF Hospital Mushaf, Sargodha, who were listed for elective surgery and met the eligibility criteria were included. Written informed consent was obtained from each participant. Eligibility criteria Inclusion criteria ● Age 18-65 years, either gender. ● ASA physical status I or II without known liver or kidney disease. ● Scheduled for elective surgery under general anaesthesia. Exclusion criteria ● Patient refusal. ● Contraindication to general anaesthesia. ● History of difficult intubation. ● Morbid obesity. ● Significant cardiovascular or respiratory disease. ● History of allergic or hypersensitivity reaction to lidocaine. ● Use of alpha-blockers, beta-blockers, anti-arrhythmic drugs or calcium-channel blockers. Allocation and intervention Eligible participants were randomly allocated in a 1:1 ratio by lottery method to Group A (lidocaine; n=30) or Group B (0.9% isotonic saline; n=30). On arrival in the operating room, standard monitoring included non-invasive blood pressure, pulse oximetry, electrocardiography, capnography and temperature monitoring. Group A: 1.5 mg/kg IV 2% lidocaine before intubation as the loading dose, followed by a maintenance infusion of 1.5 mg/kg/hour. Group B: 5 mL IV 0.9% isotonic saline before intubation, followed by a maintenance infusion of 1-2 mL/kg/hour. Five minutes before induction of general anaesthesia, patients began receiving the assigned lidocaine or saline regimen. General anaesthesia was then administered. Hemodynamic measurements were obtained before anaesthesia and after tracheal intubation as described below. Outcome assessment The primary outcomes were serial MAP, SBP and HR values measured before anaesthesia (baseline), immediately after intubation, and at 1, 5 and 10 minutes after intubation. These serial measurements were used to evaluate the magnitude and persistence of the hemodynamic response to intubation. Secondary outcomes included hypotension, bradycardia, hypoxemia (oxygen saturation <90%), coughing, laryngospasm and bucking on the endotracheal tube. PONV was recorded postoperatively. Pain was assessed using a 0-10 visual analogue scale, and ward staff recorded the number of analgesic requests during the first 24 postoperative hours when the VAS score was >4. Sample size and statistical analysis The calculated sample size was 60 patients (30 per group), using the WHO sample size calculator with a 95% confidence level and 80% power. Data were analyzed using IBM SPSS Statistics version 23. Continuous variables are presented as mean±SD and categorical variables as frequency and percentage. Independent-samples t-tests were used for between-group comparisons of continuous variables, including hemodynamic measurements at each recorded time point. Baseline categorical variables were compared using the chi-square test, while Fisher’s exact test was used for adverse-event comparisons with sparse cell counts. A two-sided p-value <0.05 was considered statistically significant.

Sixty patients were analyzed, with 30 participants in each group. Age and BMI were comparable between groups. The distributions of ASA physical status and gender were also similar (Table I). The mean number of analgesic requests in the first 24 postoperative hours was significantly lower in Group A than Group B (1.36±0.55 vs 2.10±0.80; p<0.001).

Table I. Baseline characteristics and postoperative analgesic requests

MAP was similar at baseline (88.03±1.09 vs 87.86±1.22 mmHg; p=0.571). Immediately after intubation, Group A remained close to its baseline MAP (88.50±0.50 mmHg), whereas Group B was 85.86±0.97 mmHg (p<0.001). At 1 and 5 minutes, MAP was lower in Group A than Group B (83.06±1.25 vs 95.40±1.83 mmHg and 83.43±1.69 vs 88.30±0.91 mmHg, respectively; both p<0.001). By 10 minutes, MAP was comparable (82.70±1.11 vs 82.40±1.75 mmHg; p=0.431) (Table II, Figure 1).

Table II. Comparison of mean arterial pressure (mmHg)

Baseline HR did not differ significantly between groups (83.06±1.25 vs 82.40±1.75 bpm; p=0.098). HR was lower in Group A immediately after intubation and at 1, 5 and 10 minutes (all p≤0.001), with the largest between-group separation at 1 minute (77.80±8.43 vs 102.73±1.11 bpm) (Table III, Figure 2).

Table III. Comparison of heart rate (beats/min)

Baseline SBP was similar between groups (124.20±4.08 vs 123.93±3.61 mmHg; p=0.787). At every post-intubation measurement, SBP was lower in Group A than Group B: immediately after intubation 132.10±4.57 vs 144.10±3.47 mmHg, at 1 minute 122.96±1.35 vs 138.43±1.67 mmHg, at 5 minutes 117.20±1.39 vs 132.20±2.26 mmHg, and at 10 minutes 113.80±1.60 vs 127.53±1.35 mmHg (all p<0.001) (Table IV, Figure 3).

Table IV. Comparison of systolic blood pressure (mmHg)

For peri-extubation and postoperative adverse outcomes, PONV occurred in 9 patients (30.0%) in Group B and none in Group A (p=0.002). Coughing was recorded in 10 patients (33.3%) in Group B compared with 1 patient (3.3%) in Group A (p=0.006). The between-group differences in bradycardia, laryngospasm and bucking on the endotracheal tube were not statistically significant. No hypotension was recorded in either group (Table V).

Table V. Peri-extubation and postoperative adverse outcomes (n=60). *Fisher’s exact test.

Figure 1. Mean arterial pressure before anaesthesia and after tracheal intubation.

Points show mean values and error bars show ±SD.

Figure 2. Heart rate before anaesthesia and after tracheal intubation.

Points show mean values and error bars show ±SD.

Figure 3. Systolic blood pressure before anaesthesia and after tracheal intubation.

Points show mean values and error bars show ±SD.

The present study found that intravenous lidocaine was associated with attenuation of several components of the cardiovascular response to tracheal intubation. Baseline MAP, HR and SBP were comparable, but post-intubation HR and SBP were consistently lower in the lidocaine group, while MAP differences were most evident immediately and during the first 5 minutes. These findings are clinically consistent with the concept that lidocaine can modulate airway-stimulation responses, although the magnitude and consistency of benefit reported in the literature vary across anaesthetic regimens and study populations. Recent dose-finding work by Mostafa et al. showed that higher intravenous lidocaine doses produced greater attenuation of the pressor response to endotracheal intubation, highlighting the importance of dose selection.9 In short airway procedures, target-controlled lidocaine infusion has also been examined as an anaesthetic adjunct, supporting continued interest in systemic lidocaine for peri-intubation and perioperative control.10 The secondary findings of reduced analgesic requests are compatible with randomized evidence showing an opioid-sparing effect of perioperative lidocaine, although effects on pain scores and recovery are not uniform across studies.11 Comparative trials with dexmedetomidine and fentanyl further demonstrate that different adjuncts influence HR and blood pressure in different ways and may introduce trade-offs such as bradycardia or hypotension.12 In hypertensive surgical patients, Feroze et al. reported that lidocaine attenuated the intubation stress response more effectively than magnesium sulphate.13 However, the present study excluded significant cardiovascular disease, so its results should be applied primarily to relatively low-risk ASA I-II adults rather than extrapolated directly to hypertensive or cardiac populations. Systemic lidocaine has also been investigated in procedural-sedation settings. In obese patients undergoing colonoscopy, lidocaine reduced oxygen-desaturation and apnoea episodes and reduced propofol requirements, while a randomized gastroscopy trial in older adults similarly reported lower propofol consumption and fewer selected respiratory events.14,15 These studies differ from the current surgical setting but reinforce the broader anaesthetic-sparing and airway-related effects being investigated with intravenous lidocaine. Meta-analytic evidence in older surgical patients suggests reductions in postoperative pain intensity and opioid consumption, with possible benefit for postoperative nausea but less consistent effects on vomiting and gastrointestinal recovery.16 More recent systematic reviews in gastrointestinal and breast surgery have likewise reported reductions in pain or opioid consumption in some settings, while PONV effects have not been uniform across all analyses.17,18 Dose and population remain important modifiers. A 2025 randomized study in elderly female patients undergoing endotracheal intubation found clinically relevant differences among lidocaine doses when used with propofol-remifentanil.19 A systematic review of gastrointestinal endoscopic procedures also found that supplemental intravenous lidocaine can reduce propofol requirements, supporting its role as an adjunct rather than a stand-alone anaesthetic strategy.20 The current PONV result (0% vs 30.0%) and the lower frequency of coughing (3.3% vs 33.3%) favor the lidocaine group, but the small number of participants and sparse adverse-event counts warrant cautious interpretation. Bradycardia, laryngospasm and bucking did not differ significantly after exact testing. The corrected analyses therefore present the individual respiratory outcomes separately. From a pharmacologic perspective, systemic lidocaine can act through voltage-gated sodium channels and several non-channel anti-inflammatory and antinociceptive pathways.2 The administered loading and maintenance regimen in this study is within the dose range commonly evaluated in perioperative studies; nevertheless, intravenous lidocaine should be used with careful attention to contraindications, cumulative local-anaesthetic exposure and institutional safety procedures.3 LIMITATIONS This was a single-center study with a modest sample size and short hemodynamic follow-up after intubation. The participants were ASA I-II adults, which limits generalizability to higher-risk cardiovascular or respiratory populations. The study included elective surgeries rather than one standardized surgical procedure. The adverse-event comparisons were based on small counts and should therefore be interpreted cautiously.

In this study, intravenous lidocaine was associated with lower post-intubation HR and SBP and with lower MAP at key early post-intubation time points compared with 0.9% isotonic saline. Lidocaine was also associated with fewer postoperative analgesic requests, less PONV and less coughing. These findings support intravenous lidocaine as a potentially useful perioperative adjunct for selected ASA I-II adults undergoing general anaesthesia, while larger controlled studies with standardized anaesthetic protocols are needed before routine use can be recommended broadly.

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