Saline Injection - Assisted Anesthesia in Eyelid Surgery

Purpose:

To carry out a prospective randomised controlled clinical trial to compare the efficacy of saline injection prior to the injection of Lidocaine/Adrenaline in reducing the pain of local anaesthetic injections into the upper eyelid.

Hypothesis:

Injection of saline to the upper eyelids prior to lidocaine/adrenaline injection reduces the pain of anaesthetic injections in upper eyelid surgery.

Justification:

In many surgical procedures performed under local anaesthetic, the most frightening and painful aspect of the procedure for patients is the anaesthetic injection, and various techniques have been advocated to address this.

Simple measures that reduce the pain of anaesthetic injection and are widely practised include administering the injection slowly and using a fine-bore needle (30 Gauge). Other techniques that have been shown to be effective include warming or buffering the local anaesthetic. The use of 0.9% bacteriostatic saline solution in conjunction with lidocaine has been demonstrated to significantly reduce patients' perceived pain during the injection and operative procedure in eyelid surgery. Cooling the skin immediately prior to treatment has been shown to reduce the pain of dermatological laser procedures although this might be difficult to perform around the eyes because of the risk of injuring the cornea. Similarly, topical anaesthetic agents, such as EMLA (eutectic mixture of local anaesthetics) cream, which are applied to the skin one hour prior to injection are commonly employed for use on the limbs of infants and children but are not safe for use around the eyes since inadvertent ocular application causes corneal de-epithelisation.

Sedative agents, such as midazolam may be useful in anxious patients, but this requires the input of an anaesthetist and it is often difficult to finely control the level of sedation; it is usually preferable not to have patients sedated during eyelid surgery when patient cooperation is required intra-operatively to assess the height of the eyelids, for example in ptosis surgery.

The investigators have noticed in clinical practice that whenever the investigators injected saline into the upper eyelids prior to the injection of the mixture of lidocaine/adrenaline the patients reported of no pain. The investigators assume that by using the isotonic saline cells in the tissue are not harmed and a minor effect of anesthesia is achieved. The anesthetic solution injected later on is diluted, however the eyelid is properly anesthesized.

Research Methods:

The study will be a prospective, interventional, randomised, controlled clinical trial.

All patients who fit the inclusion criteria will be offered participation in the trial on the day their surgery is booked. They will be given an information leaflet about the trial, explaining the aim of the study without describing the effect of the saline injection prior to the anesthetic solution injection in order to reduce the risk of biasing their perception. They will be advised that non-participation will not affect their care in anyway.

The intervention is of no risk to the patient and will not affect the surgical procedure in any way. Any questions that the patient has will be addressed beforehand and they will be required to sign a consent form prior to inclusion in the trial.

They will be advised beforehand that they will be required to verbally rate their pain score on a scale of 0 to 10 immediately after both sides have been anaesthetised, with 0 being no pain and 10 being the worst imaginable pain.

All participants included in the study will undergo bilateral surgery and will therefore act as their own controls: Saline will only be injected prior to the injection of the anaesthetic into one side. The test and placebo will be randomly assigned to either the first or second eyelid; the right eyelid will be injected first in all patients, as is routine practice. Computer-generated sequential binary randomisation will be used. Allocation will be concealed from the surgeon until immediately prior to the anaesthetic injection.

All anaesthetic injections will consist of xylocaine 1% with 1:100,000 adrenaline and will be administered through a short 30 Gauge needle at a constant slow speed at multiple (6-7) sites along the upper lid by a single oculoplastic consultant.

Patients' verbal pain scores will be elicited and documented immediately by the oculoplastic fellow.

Planned sample size On a scale of 0 to 10 a difference in pain score of 1.5 may be considered to be clinically significant. The power calculation for a paired t-test with 90% power and p=0.05 demonstrated that a sample size of 80 patients to be more than sufficient to detect a significant difference.

The results will be submitted for publication in a peer-reviewed ophthalmological journal and presentation at international ophthalmological meetings.