Safety and efficacy of magnesium sulfate as an adjuvant to peribulbar block for glaucoma surgery in morbidly obese patients: A randomized clinical trial

Evaluation of the efficacy and safety of adding two different doses of magnesium sulfate (75 mg & 100 mg) as an adjuvant to peribulbar block in reducing the intraocular pressure in morbidly obese patients undergoing glaucoma surgery.

Parallel group randomized clinical trial with 1:1 allocation ratio.

Research Institute of Ophthalmology, Giza, Egypt.

We will include adult (18-70 years-old), morbidly obese (body mass index of 30-55 kg/m2), male or female patients, indicated for glaucoma surgery who are American Society of Anesthesiologists physical status I, II or III and have an axial length of 20-28 mm. We will exclude patients with coagulopathy or on anticoagulant drugs or having allergy to any of the used drugs. Also, we will exclude patients with conditions preventing them from lying flat or staying still during the operation as skeletal problems or orthopneic patients or those with uncontrolled tremors (as Parkinsonism).

The trial has two groups. The first group will be given peribulbar anesthesia with a local anesthetic mixture composed of 4 ml of lidocaine 2%, 4 ml of bupivacaine 0.5%, and hyaluronidase (at a concentration of 10 IU/ml of lidocaine) to which 75 mg of magnesium sulfate will be added. The second group will receive the same doses and concentrations of lidocaine, bupivacaine, and hyaluronidase to which 100 mg of magnesium sulfate will be added.

The primary outcome variables include the onset of globe akinesia, onset of lid akinesia, and intraocular pressure. The secondary outcomes include the duration of analgesia, duration of motor block, patient satisfaction, surgeon satisfaction, and vital data (heart rate, oxygen saturation, non-invasive blood pressure).

We used the sealed, opaque sequentially numbered envelopes method for randomization and allocation concealment of patients included in this trial. We used 46 identical, opaque, letter-sized envelopes. We used rolls of household aluminum cooking foil that we cut into 46 sheets (of the same width as and twice the height of the envelope). We prepared 46 envelope-sized sheets of white paper and 46 envelope-sized sheets of single sided carbon paper. We wrote “Treatment A” on 23 paper sheets and “Treatment B” on another 23 sheets. To prepare 23 “Treatment A” envelops, we selected one envelope-sized sheet of of Treatment A and placed one sheet of carbon paper on top of the Treatment A allocation paper with the carbon side facing the paper, then we put both papers inside a foil wrapper. Then, the completed insert was placed into a blank envelope with the carbon paper closest to the front of the envelope. Finally, the envelop was sealed and we signed across the seal. We completed all the 23 “Treatment A” envelops the same way. We prepared 23 “Treatment B” envelops the same way as “Treatment A” envelops. The two sets of envelops were combined and shuffled thoroughly. Using a pen we marked a number on the front of each envelope sequentially from 1 to 46. Logically, the carbon paper inside the envelope will transfer this number to the allocation paper inside. Finally, we placed these envelopes into a plastic container, in numerical order, ready for use.

All of the following will be blinded to the type of intervention: Participants, Care providers (carrying out the peribulbar block), Health professionals (assessing the participants' outcomes), and Data analyzers.

Magnesium sulfate in peribulbar block for glaucoma surgery IPD set (all collected deidentified IPD).

Beginning 6 months and ending 24 months following article publication.

Researchers from academic institutions whose proposal for the use of data has been approved by an independent review committee identified for this purpose.

For IPD meta-analysis.

From the principal investigator (A proposal for the use of data to be submitted to the principal investigator).

A proposal for the use of data to be submitted to the principal investigator, then evaluated by an independent review committee identified for this purpose.