Author: Walid
Last saved by: Walid Moussa
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PATIENTS  AND METHODS

Patients And Methods
 The study was conducted in ophthalmology department in Benha University Hospitals after approval from both anaethesia and ophthalmology departments (local ethical committee). An informed consent was obtained from each patient and a detailed explanation to the patient about the technique, the advantages of the block and possible complications was done. 
    
  The study included 60 adult patients of either sex scheduled for elective cataract surgery; all those patients were classified according to the American Society of Anesthesiologists (ASA I, II, III).   This is a single randomized controlled study, where patients were randomly allocated into two equal groups, (30 patients in each group) according to the medications they received: with a total volume of 4-6 ml.

Group I (control group): local anesthetic 2-3 ml of 2% plain lidocaine +2-3 ml plain bupivacaine+ 0.5 ml saline 0.9% .
Group II (study group): local anesthetic 2-3 ml 2% plain lidocaine + 2-3 ml 0.5% plain bupivacaine +0.5 ml atracurium besylate (5 mg).
   
All blocks were performed by the same investigator and the surgeries were done by different surgeons. Once the decision is made to operate, anaesthetic and surgical procedures are explained to the patients and the anaethetic mixture is freshly prepared by anaethesia doctor.

 Mild sedation in the form of 0.5-1 mg Midazolam were given to anxious patients , with emphasis that the patient should be cooperative before the start of surgery to avoid excessive or unexpected movements during surgery. 
          Preoperative assessment (history, examination and investigations) was done to all patients.  
The onset and duration of lid and globe akinesia were assessed every 1 minute until maximum blockade and then every 15 minutes after surgery until complete recovery of the block. 
Routine investigations of patients undergoing cataract surgery is not essential and does not improve health or outcome of surgery but tests can be done to improve general health of the patient if required. 
The preoperative assessment included specific enquiry about bleeding disorders and drugs, as there is an increased risk of haemorrhage in patients receiving anticoagulants and a clotting profile assessment is required prior to injection.
All monitoring  and  anaesthetic  equipment  in  the operating  environments  should  be  fully  functional . Blood pressure (BP), oxygen saturation and electrocardiogram (ECG) leads are connected and baseline recordings are obtained, a secure i.v. line was done to every patient.

The patients having the following criteria well be excluded from the study: 
•   Non consent.
•   Patients  with true allergy to local anesthetic drugs.  
•   Unsuitable psychological status  
•   Mental retardation  
•   Senile dementia  
•   Head movements or tremors (Parkinsonism)  
•   Inability to lie flat.  
•   Intractable cough  
•   Communication barrier (language, deafness)    
•   Neurological disease  
• Complication from local anesthesia in the same patient on earlier       occasion  
•   Patients with high myopia (axial length more than 26 mm).
•   Patients on anticoagulants or prolonged coagulation profile.  
•   ASA more than III. 
•   Previous surgery on the same eye. The block may be difficult to perform in patients who have had previous sub-Tenon’s block in the same quadrant, previous retinal detachment and strabismus surgery, eye trauma and infection to the orbit.
Equipments 
           Intravenous cannula, Benoxinte 0.4% eye drops,2% lidocaine,0.5% bupivacaine, Atracurium, Eye speculum, Westcott scissors, Moorfields forceps, 5ml syringe, Gauge swab and Sub-Tenon’s cannula; different cannulae can be used with similar effectiveness .
Intra-operative monitoring 
    The patient should be comfortable and soft pads are placed under the pressure areas. All patients were monitored with pulse oximetry, ECG, non-invasive BP measurement Patients received an oxygen enriched breathing atmosphere to prevent hypoxia.
   ECG and pulse oximetry was continuous. Once the patient is under  the  drapes,  verbal  and  tactile contact was maintained .
Technique of sub-Tenon’s block 
•  The patient lies supine with head on a pillow.
•  A few drops of topical anaesthetic are placed on the conjunctiva.
•  A few drops of 5% aqueous iodine are placed on the conjunctiva.
•  A small speculum is inserted to hold the eyelids apart.
•  The patient looks up and laterally.
• The conjunctiva and Tenon’s capsule are pinched firmly with non-         toothed forceps, 5–7 mm from the limbus in the inferonasal quadrant.
•  With round-ended spring scissors a small snip is made through both layers.
•  A failure to visualize the sclera often indicates that the Tenon’s capsule has not been breached. Attempting to inject local anaesthetic solution into this tissue plane will almost certainly result in gross conjunctival oedema (chemosis) and produce an inadequate block; a second attempt should be made at picking up the Tenon’s capsule and a further incision made. 
• The closed scissor tips are passed through the hole, and the blades are opened while gently withdrawing them to form a short tunnel.
• A blunt, curved 19G, 25 mm sub-Tenon’s cannula is passed into the sub-Tenon’s space and allowed to slide round the globe, over the sclera to a depth of 15–20 mm in the inferonasal quadrant.
Occasionally, resistance to the canula is felt around the equator where a fibrous band may be present as the ocular muscles approach to the capsule. This is usually easily overcomed by gentle pressure. 
• The appropriate volume of local anaesthetic is slowly injected to minimize chemosis.
• The cannula is withdrawn and slight pressure maintained over the closed eye for a few minutes when complete akinesia and anaesthesia are seen.
• Sub-conjunctival haemorrhage is kept to a minimum by using topical epinephrine 1:10,000, avoiding cutting conjunctival vessels and extensive dissection, and using gentle, direct pressure.
•  Slight proptosis of the  eye ball is normal after a correctly sited injection. There may be slight leakage of solution from the tunneled point of entry of the cannula into the conjunctiva.  
•  Ballooning of the conjunctiva may occur indicating that the anaesthetic solution was injected into an incorrect tissue plane. The cannula is removed, and gentle pressure is applied to the globe.  
Common pitfalls is related to the positioning of the conjunctival incision and the conformation of dissection down to the sclera. The incision is made at a distance of 7-10 mm from the limbus. Detecting the end point of dissection comes with experience. 
The sclera has a different more fibrous, and whiter appearance than either Tenon's capsule or the continuation of the fascial layer between the extraocular muscles. Good illumination is very important for these differences to be apparent. 
The following parameter was observed:
Regarding the drugs:
1-	Onset of action.
2- Local measurements:  
A-	Eye lid movement scoring:  
Eye lid akinesia  were assessed by asking the patient to squeeze the eye while it is opened in by the anaesthetists hand.

•	score of 2= if eye lid moves freely  
•	score of 1=if it is flickering only
•	score of 0=if there is no movement     
               	   B-	 Globe movement scoring: 
The system used to score akinesia was that described by Bramha;1994, in which globe movement was scored from three to zero in each of the secondary directions of gaze (abduction, adduction, depression, and elevation). Three to zero represent from full movement through partial and flicker of movement to no movement. A fully mobile eye scored 12, whereas an immobile eye scored zero.
 If the akinesia score was four or less, the block was deemed effective. If the akinesia score was five or more, the block was deemed ineffective. 
•	Score of 3 = full movement
•	Score of 2 = moderate movement
•	Score of 1 = flicker movement
•	Score of 0 = no movement.

Failure of the block was considered when the score was still unsatisfactory 10 minutes after supplementation.
C. Pain  
Pain was assessed postoperatively by first analgesic request. And supplementation with non-steroidal anti-inflammatory (NSAID) was given when needed.

Data Management And Statistical   Method
The data were collected, revised, verified and then analyzed by the department of statistics. The following statistical methods were used:
1-	Descriptive statistics:
a-	Mean (X): the sum of all observations divided by number of observations. This test was used in analysis of patient demographic data.
b-	Standard deviation (SD):  this test was applied on patient demographic data.
2-	Analytical statistics:
a-	Student’s (t) test:  to test for the significance of difference between two means.
b-	Chi square test (X²):   to calculate the collected value to the observed value.   
 The  P value {probability of chance} 
Non significant difference if P > 0.05.
Mildly significant difference if P < 0.05.
Moderately significant if P < 0.01.
Highly significant difference if P < 0.001