Lignocaine spray applicators are a potential source of cross-infection in the anaesthetic room

Topical lignocaine anaesthesia for oropharyngeal sampling for COVID-19

OBJECTIVES

To ascertain if topical lignocaine application in oropharynx prior to swab sampling to test for COVID-19 improves a patient's comfort and to assess its effect on the swab sample taken to conduct the RT-PCR.

METHODS

Adult patients testing positive on the RT-PCR COVID-19 test were sampled again within 48 h after administering topical oropharyngeal anaesthesia. Patients were asked to rate their discomfort on a visual analog scale (VAS) for both sample A and B. A qualitative real-time RT-PCR for detection of SARS-CoV-2 RNA, was performed, and the cycle threshold value (Ct), used as a surrogate marker for the viral load, was measured for the sample taken without lignocaine (sample A) and the sample taken post-lignocaine application (sample B). The difference in Ct values of both the groups was checked for any statistical significance using paired t-test. Wilcoxon signed rank test was used on VAS scores to determine any significant decrease in discomfort.

RESULTS

Forty patients were included in the study. Twenty-nine patients (72.5%) reported the procedure to be more comfortable post-lignocaine application. Median (IQR) discomfort on VAS decreased from 7 (1) to 5 (2) after lignocaine use, which was statistically significant (p < 0.05). Mean Ct value for sample A was 17.21 ± 5.25 and for sample B was 18.44 ± 4.8 (p > 0.05), indicating a non-significant effect of lignocaine on SARS-CoV-2 concentration in the sample.

CONCLUSION

Topical lignocaine, while improving the comfort of the procedure of oropharyngeal sampling for patient did not alter the SARS-CoV-2 viral load that was detected in nasal and oropharyngeal samples taken together.

The Comparative Risks of Bacterial Contamination between a Venturi Atomizer and a Positive Displacement Atomizer

Introduction

This laboratory study determined the incidence of internal contamination of Venturi principle atomizers and positive displacement atomizers exposed to high external concentrations of Staphylococcal aureus (Staph).

Methods

Atomizer device nozzle tips were immersed into a Staph solution and 1 ml of spray was atomized via compressed wall air (Venturi) or hydraulic pump (positive displacement). The Venturi nozzle was then wiped with 70% isopropyl alcohol while the disposable positive displacement nozzle was replaced. After 30 minutes, 1 ml of atomized fluid was collected and cultured and the process was repeated. After sixteen uses the fluid remaining in the bottles was cultured. The Venturi atomizer also was subjected to a single use trial to determine the location of device contamination.

Results

Venturi atomizers sprays grew Staph in every case (144/144), while positive displacement atomizer sprays never grew contaminants (0/144; p < 0.0001). At the end of 16 uses, 7/9 of Venturi atomizers had Staph within their medication reservoirs while none (0/9; p = 0.002) existed in the positive displacement atomizers. After a single use of the Venturi atomizer, the medication reservoir, the air lumen and the medication lumen of the nozzle were all contaminated with Staph.

Conclusions

External bacterial contamination of the atomizer nozzle tip results in internal bacterial contamination of Venturi devices in as little as one use but not of positive displacement devices. These results warrant further investigation to determine whether a risk of cross-contamination exists in a clinical setting.

An Assessment for the Presence of Bacterial Contamination of Venturi Principle Atomizers in a Clinical Setting

Background

Venturi principle atomizers have been criticized for potential contamination and disease transmission when used for nasal application. A recent laboratory study reported a high rate of contamination of these atomizers after their tips were immersed and sprayed into a broth containing Staphylococcus aureus. The objective of this study was to determine whether the Venturi-type atomizers used regularly at a busy referral center for sinonasal disorders were contaminated with bacteria.

Methods

Fifteen Venturi-type atomizers containing 2% lidocaine (four bottles), 4% lidocaine (three bottles), or 0.05% oxymetazoline (eight bottles) were sprayed onto blood agar plates. All atomizer bottles had been in routine use in a tertiary rhinology clinic for 1 month. The contents within each bottle's reservoir also were cultured. Thus, the total sample size was 30 plates. Then, the plates were incubated at 35°C for 48 hours and then at room temperature for 72 hours.

Results

Three of our 30 plates grew one colony each of Gram-positive bacilli, Gram-positive cocci, and Staphylococcus species.

Conclusion

The rare growth of any bacteria seen in our samples could as likely represent contamination during processing and handling of the plates as contamination of the atomizers themselves. Thus, Venturi-type atomizers may not have a high potential contamination risk, which has been suggested by previous reports.

Multiple-Use Atomizers in Outpatient Otolaryngology Clinics are not Necessarily an Infectious Risk

OBJECTIVE: We sought to determine the risk of bacterial transmission from multiple-use atomizers in an outpatient otolaryngology clinic.

STUDY DESIGN AND SETTING: Atomizers in 6 examination rooms were analyzed for bacterial contamination. Sterility of associated tubing from 1 atomizer was assessed. Multidose drug solutions in the atomizers (phenylephrine and tetracaine) were cultured multiple times over a 2-week period. Serial dilutions of the original sample were cultured to minimize inhibitory effects of antiseptic agents in the drug formulations.

RESULTS: No bacteria were recovered from tubing cultures. Only 2 (0.6%) of 336 cultures of the drug solutions yielded bacterial growth. In both cases, coagulase-negative Staphylococcus was recovered in 1 of the dilutions prepared from original samplings.

CONCLUSION: Multiple-use atomizers that contain phenylephrine and tetracaine solutions with bacteriostatic preservatives in an outpatient otolaryngology clinic do not yield significant bacterial growth and, when used as described, do not pose an infectious risk of bacterial transmission between patients.