The Use of Lidocaine in Endotracheal Tube Cuffs
Sometimes in a life and death situation where the patient is unconscious there is a need to secure the passageway of air, saving the person’s life. During this type of emergency an endotracheal tube (ETT) is inserted into the patient’s esophagus and with the use of medical technology allows the person to continually breathe without allowing the contents of the stomach to come out. The process of inserting ETT is commonly called endotracheal intubation. Although endotracheal intubation is the best way to secure the patient’s airway and has proven to be a very safe procedure, the side effects can be painful or at times even dangerous, putting the patient’s life in serious risk. The following studies will examine the effectiveness in the use of Licodaine, a common anesthetic in reducing the occurrence of side effects.
When an unconscious person is brought to the hospital there is sometimes the need to secure the person’s airway. In serious conditions the patient may have lost the ability to breathe on his own. The ingenious solution is to use ETT and to insert the same through the person’s mouth and then down to the esophagus. It does not require a medical practitioner to partially comprehend that it is not natural to insert a tube inside a person’s mouth and to even push it down into the esophagus. A simple experiment of pushing ones finger into the oral cavity will result in an unpleasant feeling.
But in the case of the ETT inside an unconscious person the immediate positive effect is in providing much needed oxygen so that the patient will not die. It is only after some time when the patient and the health worker will notice the side effects. Accoridng to Altintas, et al., “The insertion of an endotracheal tube usually causes hypertension, tachycardia or other dysrhythmias, myocardial ischaemia, surgical bleeding and some times bronchospasm; it provokes increase in intracranial and intraocular pressure that are particularly disturbing in neurosurgical, ophthalmic and plastic procedures” (2000). As mentioned earlier the esophagus area will react negatively when a foreign object is placed inside the throat.
The preceding discussion has made it very clear that the complications are serious. Furthermore, the side effects can also harm the patient in another way – by making the patient unstable in surgery. Aside from the complications listed above another common complaint among patients with ETT is sore throat, “…with a reported incidence ranging from 24% to 90% (Navarro & Baughman, 1997). Something has to be done to alleviate the pain and to minimize complication that will either seriously hurt the patient or make surgical procedures extremely difficult.
A standard ETT comes with a cuff, a feature in the ETT that allows pressure to be maintained in the airways during inhalation phase of artificial breathing. The cuff prevents exhalation of regurgitated gastroesophageal contents (Navarro, et al., 2007). But this little device is causing some problems. The pressure of the ETT cuff is transmitted to the tracheal mucosa. This pressure may cause ischemia of the mucosal vessels followed by serious complications such as ulceration, inflation, hemorrhaging, tracheal stenosis and tracheoesophageal fistula (Navarro, et al., 2007). The following studies will show how medical practitioners tried to turn this inherent weakness – in the design of the ETT – into strength.
They realized that since there is a need to maintain pressure in the cuff, it is then possible to maintain pressure using either air or liquid. At this point they tried to find out the effectiveness of the lidocaine in maintaining pressure while at the same time decreasing the incidence of side effects particularly sore throat, hoarseness and coughing. If the experiments prove successful then patients can benefit from the use of an ETT minus the side effects.
There can be two substances that can be used to maintain pressure: air or liquid. It was discovered that air causes exposure to hyperpressure because the gas used – nitrous oxide – diffuses more rapidly into the cuff but takes a slower time to be released out of the cuff. The improper pressure is creating damage to the pharyngeal mucosa. This is the reason why researchers turned to lidocaine as an alternative substance that can be used to create pressure while at the same time deliver a drug that will help minimize side effects.
The use of lidocaine is made possible by the fact that L-HCL placed inside ETT can readily be diffused across its hydrophobic membrane (Dollo, et al., 2001). It was hypothesized that the lidocaine would diffuse across the cuff to produce topical anesthesia on the trachea preventing a sore throat (Porter, 1999). Aside from providing anesthesia, lidocaine attenuates the cough reflex by action on the nerve ending found in the trachea this resulted in less coughing, bucking of the ETT, which in turn lessened the damage and irritation.
The results from the different studies did not result in a unanimous decision in favor of lidocaine. In some studies there was a significant decrease in sore throat after postoperative surgery while in others there was no significant effects that would have allowed the proponents to declare that lidocaine is the answer to ETT complications such as coughing, sore throat, and hoarseness. There is a need to reexamine the methodology especially in the way lidocaine was administered as well as the patients that were allowed to participate in the study.
It appears that the researchers were very thorough in their preparation and were very careful in designing a methodology that would have yield conclusive results as to the effectiveness of lidocaine. For instance they used a control, a saline solution, to show that another type of fluid other than lidocaine was used to be able to compare if the liquid state of the material used to maintain pressure is not the reason for a decrease in pain. Aside from that those who had surgical procedures done on their face, ear, eye, nose or throat were excluded from the list of participants.
Exclusion criteria also included those who had history of chemotherapy or radiation therapy, history of liver disease, cardiac dysrhytmias or heart block, sensitivity and allergy to lidocaine, prior lidocaine, anticholinergic or steroid therapy, known difficult airway, difficult intubation, intubation less than 30 minutes; nasogastric tube placement; upper respiratory tract infection, preoperative sore throat, pregnancy, weight less than 35 kgs (Porter, 1999). The exclusion criteria is easily understandable because their conditions may increase the severity of the sore throat or decrease the effect of the drug.
There was no significant improvement when the proponents used lidocaine, air, and saline in reducing the incidence of post operative sore throat. There was only one study the one performed by L.H.C. Navarro et al, which showed a significant decrease in postoperative sore throat. A closer examination will reveal that this group made a key adjustment in their research. Instead of using lidocaine to as a gel or as a means of improving the intubation process they place lidocaine inside the ETT cuff. This allowed for the slow release of the lidocaine within the trachea and allowed for its anesthetic properties to work well.
While it was made clear that there were no significant changes in the incidence of sore throat after surgery, it was found out that there was a significant difference at the 24-hour evaluation. Sixty eight percent (68%) of the lidocaine group reported no sore throat while there was only forty two percent (42%) of the air group that reported to have not experience sore throat. It was also noted that there was a significant decrease in severity of sore throat after one hour after surgery.
It can be argued that lidocaine indeed works as an anesthetic and minimized irritation, bucking, and other negative reactions of the nerve endings against the ETT. This is made evident by the decrease in severity of sore throat one hour after surgery. This was reinforced by the findings that 24 hours after surgery there was a significant number of patients who reported to have no sore throat as opposed to the control group. This can also be interpreted that lidocaine was still in effect after extubation.
The numerous studies conducted in the use of lidocaine may have not provided conclusive evidence that lidocaine can be used as a drug that will effectively lower the incidence of sore throat. But it can also be argued that changing the methodology will show the effectiveness of lidocaine. One possible modification is to fill up the cuff with lidocaine as opposed to using it merely as a lubricant or a anesthetic for easy intubation. The procedure were there was a slow release of lidocaine must be further improved. There must also be a new study where proponents will try to increase the length of time needed for ETT to remain in the trachea as this would increase the time needed for diffusing lidocaine. There is also a need to look into the impact of allowing smokers to participate in the study. Thus another study must be made using non-smokers as subjects. But there is evidence showing that the anesthetic properties of lidocaine contributed in lowering irritation and damage which could have lessened the incidence of sore throat.
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Navarro, R. & V.L. Baughman. (1997). Lidocaine in the endotracheal tube cuff reduces
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Navarro, L.H., et al. (2007) Effectiveness and safety of endotracheal tube cuffs filled with air
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Porter, N., V. Sidou, & J. Husson. (1999). Postoperative sore throat: incidence and severity after
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