Alcohol (70%) versus alcoholic chlorhexidine solution (0.5%) in skin antisepsis for neuraxial blocks: a randomized clinical trial

ABSTRACT Objective: to compare the use of 0.5% alcoholic chlorhexidine and 70% alcohol in skin antisepsis for neuraxial blocks. Method: this is a non-inferiority randomized clinical trial, with two parallel arms. Seventy patients who were candidates for neuraxial block were randomly allocated to group A (n = 35), in whom antisepsis was performed with 0.5% alcoholic chlorhexidine, or to group B (n = 35), in whom we used 70% hydrated ethyl alcohol. Swabs were harvested for culture at three times: before antisepsis, two minutes after application of the antiseptic, and immediately after puncture. The samples were sown in three culture media and the number of colony forming units (CFU) per cm² was counted. Results: there was no difference between the groups regarding age, sex, body mass index, time to perform the block or type of block. There were no differences between groups in the CFU/cm² counts before antisepsis. There was less bacterial growth in group B two minutes after application of the antiseptic (p = 0.048), but there was no difference between the groups regarding the number of CFU/cm² at the end of the puncture. Conclusion: 70% alcohol was more effective in reducing the number of CFU/cm² after two minutes, and there was no difference between the two groups regarding skin colonization at the end of the procedure. These results suggest that 70% alcohol may be an option for skin antisepsis before neuraxial blocks. Trial registration: ClinicalTrials.gov, NCT02833376.

Epidural anesthesia can also be used, with the difference that the blockade can be achieved by segments, such as only the trunk or abdomen. This type of anesthetic procedure has the main advantage of maintaining the patient's spontaneous ventilation and awareness 1 .
As it is an invasive procedure, to prevent

Original article A B S T R A C T A B S T R A C T
Objective: to compare the use of 0.5% alcoholic chlorhexidine and 70% alcohol in skin antisepsis for neuraxial blocks. Method: this is a non-inferiority randomized clinical trial, with two parallel arms. Seventy patients who were candidates for neuraxial block were randomly allocated to group A (n = 35), in whom antisepsis was performed with 0.5% alcoholic chlorhexidine, or to group B (n = 35), in whom we used 70% hydrated ethyl alcohol. Swabs were harvested for culture at three times: before antisepsis, two minutes after application of the antiseptic, and immediately after puncture. The samples were sown in three culture media and the number of colony forming units (CFU) per cm² was counted. Results: there was no difference between the groups regarding age, sex, body mass index, time to perform the block or type of block. There were no differences between groups in the CFU/cm² counts before antisepsis. There was less bacterial growth in group B two minutes after application of the antiseptic (p = 0.048), but there was no difference between the groups regarding the number of CFU/cm² at the end of the puncture. Conclusion: 70% alcohol was more effective in reducing the number of CFU/cm² after two minutes, and there was no difference between the two groups regarding skin colonization at the end of the procedure. These results suggest that 70% alcohol may be an option for skin antisepsis before neuraxial blocks. Trial registration: ClinicalTrials.gov, NCT02833376. The antiseptic activity of ethyl alcohol occurs by denaturation of proteins and removal of lipids, including the envelopes of some viruses. To achieve maximum germicidal activity, the alcohol must be diluted with water, which allows protein denaturation. The recommended concentration to achieve greater germ-killing speed is 70% 6 .
Chlorhexidine is a germicide from the group of biguanides, which is more effective at pH between five and eight, and acts better against gram-positive bacteria than gram-negative ones or fungi. It has immediate action and residual effect, in addition to low potential for toxicity and photosensitivity to contact, being poorly absorbed by intact skin. Its mechanism of action involves increasing the permeability of the cell wall, causing precipitation of intracellular components. This action is potentiated by alcohol, so the alcoholic solution is more Infections of the neuroaxis after anesthesia are rare, but serious. These complications are generally cited as case reports. The exact incidence is unknown, but they can result in devastating morbidity and mortality, including abscess formation, meningitis, or spinal cord compression secondary to abscess formation [8][9][10][11][12]  To calculate the sample size, we used data from the study by Sato et al. (1996) 15 . We applied the one-

Statistical analysis
Given the nature of the variables studied and the variability of the values found, we used nonparametric tests 17

RESULTS
We included 70 patients in the study. Figure 1 shows the flow of patients in the study. There was no exclusion. We excluded the result of cultures of one patient from Group B after puncture due to contamination of the samples. Both groups were homogeneous in terms of the main demographic characteristics. The puncture median time was three minutes for both groups, also with no statistical difference, and the most frequent type of anesthesia was spinal, in over 90% of patients in both groups (Table 1).

. Number of CFU in the Mannitol Agar medium in groups A and B in the three moments (Friedman Analysis of Variance by Ranks), and comparison between groups in each moment (Mann-Whitney test).
Mannitol

Table 4. Number of CFU in the Teague Agar medium in groups A and B in the three moments (Friedman Analysis of Variance by Ranks), and comparison between groups in each moment (Mann-Whitney test).
Teague Agar (Gram ) There are bacteria that are located deep in the skin, in places where antiseptics often do not penetrate, due to lipophilic secretions in the stratum corneum.
For this reason, the use of alcohol-based antiseptics is always indicated, due to the degreasing action, which provides greater penetration capacity and efficiency in the eradication of deeper bacteria 23,26,27 . Alcohol-based antiseptics have rapid action, denaturing proteins and removing lipids, with the ability to penetrate the stratum corneum, follicles and orifices of the sebaceous glands, sites where there is a higher concentration of bacteria 6,23,28,29 .
Studies have shown that one must wait a minimum of two minutes to antiseptic action after the application 8,23,30 . The protocol of the present study took into account this minimum time of two minutes between antisepsis and puncture, which proved to be sufficient to reduce the skin microbiota. The puncture time varied between one and 22 minutes, with a median of three, and even after the longest punctures, there was no significant bacterial growth, demonstrating that the two studied antiseptics showed satisfactory residual action for the procedure in question, which is fast.
Other authors have also demonstrated the satisfactory residual action of these two antiseptics in the short term, comparing the effect of alcoholic chlorhexidine and 70% alcohol. They collected samples with swabs of intact skin from different regions of the body, 10 minutes, six hours and 24 hours after application, and did not observe statistical difference in colonization after 10 minutes or six hours. However, they found that after 24 hours, chlorhexidine maintained the residual effect, which did not happen with alcohol, with statistical significance 28 .
Alcohol at 70% was more effective in reducing the number of CFU/cm 2 after two minutes, and there was no difference between the two groups regarding skin colonization at the end of the procedure. These results suggest that 70% alcohol may be an option for skin antisepsis before neuraxial anesthesia.