Since the advent of flexible nasofibrolaryngoscopy (NSLF) in 1968, this has become an essential diagnostic tool in the doctor's otolaryngologist, largely due to the physical characteristics of the instrument (diameter, easy handling) and the advantages in visualization of structures of the upper aero-digestive tract. But never use free of discomfort to the patient condition, why various options topical anesthesia (ATL) have been proposed for the development of technology to reduce the discomfort.

Commercial preparations
  Initially, cocaine paste was one of the most popular drugs, the situation was changing over time and today is virtually obsolete due to adverse effects from a cardiovascular point of view which is associated use, apart from the high health cost involved^[1]. Later, in some countries the association of lignocaine and xylometazolina is marketed, showing at the time similar to that obtained with cocaine paste, with a much lower cost compared to this effect, but this mixture has been slowly losing presence in the market^[2-3]. Later in some Anglo-Saxon countries began to be marketed a drug called Co-Phenylcaine forte (lignocaine hydrochloride, phenylephrine and benzalkonium chloride), which has an anesthetic effect, vasoconstrictor and decongestant nasal level.

  Despite this, in many countries, either by not having specific preparations or inability to use legally prepared as cocaine paste is usually used a topical solution in which a local anesthetic is mixed and epinephrine with in order to achieve a local anesthetic effect and decongestant nasal mucosa. Lidocaine, usually one of the most widely used for this purpose drugs, is a member of the amine group local anesthetic acts by blocking the propagation of nerve impulses to prevent the entry of Na + ions through the nerve membrane, has its maximum effect from the first 2-5 min after application. Epinephrine is a catecholamine, acts as a vasoconstrictor, is usually added to various local anesthetics and absorption delaying allowing thus prolonging the local anesthetic effect.

Precautions
  It is important to note that the use of these preparations is not safe for all patients, is a serious and adverse effects to keep in mind when using a mixture of lidocaine and epinephrine are described, and the patient may experience tachycardia, AV block or tremors, which determines having to restrict their use in cardiac patients or patients allergic to the amide group. Similar situation in patients where cocaine paste is applied.

Comparative studies
  Is the use of topical anesthesia in flexible NSFL necessary? It is here that, despite being a rational factor to consider and possibly intuitive criterion, several studies question the use of topical nasal anesthesia (ATN) in relation to the reduction of discomfort during scanning NSFL. By consulting the literature (Table 1).

Table 1: Summary of studies included in this review

  we find work as developed by Singh et al^[4] who evaluated a total of 60 patients, using 4% cocaine in one nostril and saline in the pit contra-lateral, conducted the NSFL in each nasal and posterior fossa that each patient had to answer a scale of 0-5 points inconvenience. In their study, they were not needed anesthetics intranasal during NSFL (p = 0.411), but the fact of applying each substance in a separate nostril creates a potential bias in this study due to anatomical variations that may exist between each nostril. Subsequently Leder et al.^[5] evaluated a total of 152 patients were randomized into 3 groups (cocaine, decongestant and placebo), each patient had to respond after the test to a test of discomfort was 1 to 5, resulting in a slight trend toward decreased pain after application of ATN which was not statistically significant. While on the other hand Frosh et al.^[6] evaluated a total of 82 patients were randomized into 3 groups (lidocaine, placebo, nothing) and after testing each patient was consulted regarding a visual analog scale to assess the degree nuisance generated by the NSFL resulting in increased pain (p = 0.048) and the level of discomfort (p = 0.001) with the use of ATN Global Experience. Cain et al^[7] used a similar design, prospective, double-blind, 3 arm in which I compare a group of 90 patients using cophenylcaine, placebo and nothing, still the group less discomfort experiment which was treated with placebo, not getting advantages over the use of the ATN to testing. But these studies found a possible bias, since each individual underwent a scan with a single substance, so every opinion referred only to discomfort in relation to this matter and did not correspond to the comparison between different substances, apart from the aforementioned anatomical variations that can be found in the nostrils of the same patient.
  Bouralias et al.^[8] compared the use of lidocaine spray 10% versus the use of 2% tetracaine impregnated espongas neurosurgery, the aim of this study was to determine the validity of using such sponges when topically anesthetize the nasal cavity, resulting in a greater reduction of pain and discomfort when using these sponges soaked in tetracaine 2% (p = 0.001). While Bonaparte et al.^[9] compared the use of lidocaine spray versus placebo, associating or not to use mouthwash with listerine in 120 patients, achieving demonstrate a statistically significant reduction in pain with the use of lidocaine spray (p = 0011) and the discomfort (p = 0.008), compared to placebo, and showing a decrease in the degree of associating listerine even greater discomfort. Johnson et al.^[10] evaluated a total of 15 patients, using a crossover study, which compared the use of cocaine vs. oxymetazoline and placebo, and would achieve this study demonstrate the advantages of topical anesthesia using nasal cocaine paste during exploration NSFL a statistically significant ( p = < 0.05 ). Chiesa et al.^[11] in a study in 18 patients, also apply design crossover study in which they compared the use of Lidocaine + Epinephrine vs oxymetazoline and placebo during scanning NSFL, the degree of discomfort was assessed by visual analogue scale also demonstrated statistically significant (p = < 0.05) decreased pain and discomfort during the test run. Being perhaps this design ideal study in such tests as each individual is his own control, is explored in the three substances in one or both nostrils and possible anatomical variations will not be a factor affecting the possible outcomes.

Conclusion

  Despite the diversity of results in the literature, those with greater methodological rigor support the use of topical nasal anesthesia before the NSFL. Achieving demonstrate decreased pain and feeling of discomfort by the patient at the time of testing. However, it is likely that further studies with better methodological design help clarify the existing results. Based on the evidence we now have, it is possible to recommend the use of topical nasal anesthesia when performing this type of exploration, taking into account the potential risks in patients with underlying heart disease or allergy to any component mix.

References