Local anaesthesia is indispensable in dermatologic practice, as it enables a wide range of minor surgical procedures with minimal discomfort and morbidity. However, the act of administering local anaesthetic itself can elicit physiological responses that may influence patient comfort and systemic stability. Pain and anxiety associated with needle penetration and injection have been linked to transient increases in heart rate and blood pressure, reflecting activation of sympathetic neural pathways in response to noxious stimuli and psychological stressors. For example, significant elevations in cardiovascular parameters have been observed during dental local anaesthesia delivery, particularly in patients with heightened anxiety or fear of injection, suggesting that both psychological and procedural factors contribute to these responses [1].

In addition to psychogenic influences, the pharmacological properties of local anaesthetics and their adjuncts such as vasoconstrictors may exert independent haemodynamic effects. Studies involving lidocaine with epinephrine have documented modest increases in systolic blood pressure and heart rate following administration, attributable to systemic absorption of vasoconstrictors and resultant sympathomimetic activity [2,3]. Although these changes are generally within physiological limits in healthy individuals, they can be clinically relevant in patients with cardiovascular comorbidities [4,5].

Despite extensive research in dental and other surgical settings, there remains a relative paucity of data specifically addressing the differential physiological impact of simple needle insertion versus actual drug infiltration in the context of dermatologic local anaesthesia. Understanding these distinctions is important because they may inform technique selection, patient counselling, and peri‑procedural monitoring, especially among individuals at risk for exaggerated sympathetic responses. Therefore, this study was designed to characterise and compare the immediate cardiovascular and oxygen saturation responses elicited by needle insertion alone versus drug infiltration during routine dermatologic anaesthetic administration.

This prospective, observational study was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants prior to inclusion in the study.

Study Population: Patients aged 18–65 years scheduled for minor dermatologic procedures requiring local anaesthesia were screened for eligibility. Exclusion criteria included known hypersensitivity to local anaesthetics, history of cardiovascular or autonomic dysfunction, chronic use of analgesic or sedative medications, and pregnancy or lactation.

Sample Size Calculation: The sample size was calculated based on a previous study evaluating hemodynamic responses to local anesthetic procedures, which reported a mean increase in heart rate of 8 ± 5 beats per minute following needle insertion. Assuming a two-sided significance level (α) of 0.05 and a power (1–β) of 80% to detect a similar difference between needle insertion and drug infiltration, the minimum required sample size was estimated to be 25 participants per group. To account for potential dropouts and incomplete data, 30 participants were enrolled in each group, yielding a total sample size of 60.

Study Design and Procedure: Participants were randomly assigned to two groups based on the type of stimulus: (1) needle insertion without drug infiltration and (2) drug infiltration using 1% lignocaine without epinephrine. All procedures were performed by a single experienced dermatologist to minimize procedural variability.

Physiological Monitoring: Baseline heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), and oxygen saturation (SpO₂) were recorded after a 5-minute rest in a supine position. Continuous monitoring was performed using a standard computerised multiparameter monitor.

Intervention Protocol:

• Needle Insertion Group: A sterile 26G needle was inserted subcutaneously at the procedure site without injecting any solution.
• Drug Infiltration Group: 1–2 mL of 1% lignocaine was injected subcutaneously at the procedure site using a 26G needle.

Physiological parameters (HR, SBP, DBP, and SpO₂) were recorded at the following time points: baseline, immediately after needle insertion or drug infiltration, and at 1, 3, and 5 minutes post-intervention.

Data Analysis: Data were compiled and analyzed using SPSS version 25. Continuous variables were expressed as mean ± standard deviation (SD), and categorical variables as frequencies and percentages. Comparison between groups was performed using independent t-tests for continuous variables and chi-square tests for categorical variables. A p-value <0.05 was considered statistically significant.

A total of 60 participants were included in the study, with 30 in the needle insertion group and 30 in the drug infiltration group. Baseline characteristics, including age, sex distribution, body mass index, heart rate, blood pressure, and oxygen saturation, were comparable between the two groups, with no statistically significant differences observed (Table 1).

Heart Rate Response: Following the intervention, the needle insertion group exhibited a more pronounced immediate increase in heart rate compared to the drug infiltration group (84.5 ± 9.2 vs. 79.2 ± 8.1 beats/min, p=0.01). This elevated heart rate persisted at 1 minute post-intervention (82.1 ± 8.7 vs. 77.5 ± 7.8 beats/min, p=0.02) but returned to near-baseline levels by 3 and 5 minutes, where the differences were no longer statistically significant (Table 2).

Blood Pressure Response: Systolic and diastolic blood pressures increased immediately after needle insertion and drug infiltration, with significantly higher values observed in the needle insertion group (SBP: 130.2 ± 11.1 vs. 125.4 ± 9.5 mmHg, p=0.03; DBP: 83.1 ± 7.6 vs. 79.8 ± 6.9 mmHg, p=0.04). At 1 minute, the needle insertion group continued to show elevated blood pressure compared to the drug infiltration group (SBP: 128.1 ± 10.6 vs. 124.0 ± 9.2 mmHg, p=0.04; DBP: 81.5 ± 7.4 vs. 78.7 ± 6.6 mmHg, p=0.05). By 3 and 5 minutes, blood pressure in both groups gradually returned to baseline levels, and differences were not statistically significant (Table 3).

Oxygen Saturation Response: SpO₂ remained stable in both groups throughout the observation period, with no significant changes from baseline or between groups at any time point (Table 4).

Table 1: Baseline Characteristics of Participants

Table 2: Heart Rate (HR) Response (beats/min)

Table 3: Blood Pressure Response (mmHg)

Table 4: Oxygen Saturation (SpO₂) Response (%)

In this study, needle insertion without drug infiltration produced more pronounced transient increases in heart rate and blood pressure compared with lignocaine infiltration, despite both stimuli being components of routine dermatologic anaesthesia. This pattern aligns with previous observations that noxious stimuli associated with needle penetration and injection provoke sympathetic activation, leading to transient cardiovascular changes [6]. Endogenous catecholamine release triggered by procedural pain has been shown to elevate both heart rate and blood pressure, even in normotensive patients undergoing simple dental procedures with local anaesthetics containing vasoconstrictors. Such haemodynamic responses are important to anticipate, particularly in patients with cardiovascular vulnerabilities [7].

Procedural anxiety and pain perception directly influence autonomic responses during local anaesthetic delivery. Studies have demonstrated that higher levels of anxiety correlate with increased cardiovascular reactivity during anaesthetic administration, suggesting a psychophysiological component to haemodynamic changes [8,9]. This interplay may partly explain why even minimal puncture stimuli, such as needle insertion alone, can elicit measurable increases in heart rate and blood pressure. These sympathetically mediated responses are not solely related to the pharmacodynamic effects of anaesthetic drugs but also to afferent nociceptive signalling from tissue trauma and psychological stressors associated with needle procedures [10].

Clinically, understanding the relative contributions of physical (needle trauma) and pharmacological (drug infiltration) factors in haemodynamic modulation can inform peri‑procedural planning. For example, strategies to reduce pain and anxiety—such as topical anaesthesia, slower injection techniques, or patient reassurance—have been shown to attenuate pain scores and may indirectly mitigate sympathetic activation [11,12]. Moreover, tailoring anaesthetic formulations and infiltration techniques to minimize discomfort may further reduce unnecessary physiological stress during dermatologic procedures.

In our results, oxygen saturation remained stable in both groups, indicating that short‑term procedural stimuli do not significantly impact peripheral oxygenation in healthy subjects. This is consistent with prior clinical studies demonstrating that while cardiovascular parameters may fluctuate with procedural pain and stress, oxygen saturation is typically preserved during brief local anaesthesia administration in outpatient settings. Overall, these findings reinforce the need for holistic approaches that consider both nociceptive and psychophysiological factors when administering local anaesthesia in dermatologic practice..

Needle insertion without drug infiltration induces a more immediate and pronounced hemodynamic response, reflected by transient elevations in heart rate and blood pressure, compared to subcutaneous lignocaine infiltration during minor dermatologic procedures. Oxygen saturation remains stable regardless of the type of intervention. These findings highlight the physiological impact of procedural stimuli and underscore the importance of anticipating transient cardiovascular responses even in routine dermatologic anesthesia, particularly in patients with underlying cardiovascular risk.

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