Intradermal and Subcutaneous Lignocaine for Arterial Blood Gas Sampling: A Randomized Controlled Trial

Abstract

Introduction: The use of local anesthesia (LA) prior to arterial blood gas sampling is recommended but is not widely used. We tested the hypothesis that intradermal administration of local anesthesia would be as effective as subcutaneous administration in reducing pain from arterial blood gas sampling. Aims: The primary aim of this study was to evaluate the effect of intradermal and subcutaneous lignocaine on patient-perceived pain during arterial blood gas sampling. The secondary aims were to evaluate if different routes of LA administration had an impact on the difficulty and complications of ABG sampling. Methods: We undertook a randomized, single-blind, placebo-controlled trial in New Zealand. We enrolled patients attending a nurse-led outpatient oxygen clinic who were 18 to 90 years of age and who had an oxygen saturation of 93% or less at rest. Patients were randomly assigned to receive intradermal 1% lignocaine, subcutaneous 1% lignocaine, or subcutaneous normal saline. Patients and nurse assessors were blinded to the treatment allocation. The primary endpoint was a patient-assessed pain score using a graphic rating scale (0-10). Results: 135 patients were randomized (54 patients in the intradermal lignocaine group, 54 patients in the subcutaneous lignocaine group, and 27 in the subcutaneous saline group). The mean patient-assessed pain score for the intradermal lignocaine group was 1.8 (+/- 1.1), which was a relative reduction of 47% (95% C.I. 31%-59%, p < 0.0001) from the mean patient-assessed pain score of 3.4 (+/- 1.1) for the subcutaneous saline group. The mean patient-assessed pain score for the subcutaneous lignocaine group was 2.1 (+/- 1.1), which was also a significant relative reduction of 36% (95% C.I. 17%-51%, p = 0.0001) compared to the subcutaneous saline group. Intradermal lignocaine reduced pain more than subcutaneous lignocaine, with a relative pain reduction difference of 20% (95% CI -4%-49%, p = 0.05). Bruising was more frequent in the subcutaneous lignocaine group (9.3%) than in the intradermal (0%) and saline groups (0%). Conclusion: Intradermal lignocaine is at least as effective as subcutaneous lignocaine for reducing patient-perceived pain from arterial blood gas sampling and results in less bruising.