Anaesthesia in Ophthalmic Surgery

MM Sharma*, AM Sharma**

Introduction

Anaesthesia for ophthalmic surgery is recognized sub-speciality of anaesthetic practice. Anaesthetic services are provided to wide age range of patients from neonates {pre-mature babies having ROP} to very elderly.
Ophthalmic operations in adults are mostly done under local/regional anaesthesia. It is our knowledge that, “No local or regional technique is totally free from serious systemic adverse events, be it technique itself or patient factor.”
In last few years there are many advances in ophthalmic anaesthesia for patient’s safety. This is due to availability of excellent monitoring systems, more efficient OT management and superior anaesthetic drugs, but above all “man behind machine is more important”.
Patients for ophthalmic surgery are usually of high age group with many systemic diseases therefore belong to Anaesthesiological risk group ASA III or IV. Life threatening events like Cardio-vascular depression, brady or tachycardia, dysrhythmias, hypo or hypertension, hypoxia, hypercarbia, airway obstruction can take place even during local anaesthesia and may frequently need intervention, thus well-monitored anaesthesia care (stand by) is extremely important.

Role of Anaesthetist is to do pre-anaesthetic evaluation, including general and systemic examination, take h/o systemic diseases like HT, DM, CRF, IHD, etc., allergy to any drugs, h/o previous anaesthesia and intake of drugs which may interfere in anaesthesia or surgery e.g. anticoagulants, antiplatelets, antipsychotic, MAO inhibitors, etc.
Decide fasting policies, patient’s suitability for day care surgery and pre-anaesthetic counselling.
Beside general anaesthesia many different local and regional anaesthesia techniques are used with or without sedation.

Monitoring

• IV access, Clinical Observation : Pt’s skin colour, pulse, Respiration etc.
• Pulse oxymetry (SpO2), - A Must, B.P. (NIBP) if possible
• ECG : for arrhythmia, bradycardia, ST changes, VPC’s etc.,
• ET CO2 : very useful during GA in children and neonates.

• Conscious sedation depending on pt’s condition and type of operation commonly used drugs are midazolam, remifentanil, fentanyl in minimal doses.
• Other drugs used for deeper sedation are opiates, hypnotics, diazepam and propofol in titrated doses.

• Unwanted effects of sedation to be identified and immediate measures like oxygenation and medication accordingly to be administered at earliest.
  
• In Post-op period patient should be monitored and observed till fit for discharge from hospital.
  

• Sub-Tenon (preferred in Ant-segment surgery).
  
• Retro-bulbar (intra-cone) least preferred, almost outdated.
  
• Peri-bulbar (safe and most preferred ocular block with least complications) (Fig. 1, 2).

Severe Systemic Event
* Brain Stem Anaesthesia (xylocaine toxicity)
1. Drowsiness, light head ache.
2. Cranial nerve palsy.
3. Respiratory Arrest (if not treated).
4. Confusion, loss of verbal contact.
5. Respiratory depression.
6. Cardiac Arrest
Mind you all this is 100% reversible if treated early (a stitch in time can save from unwarranted complications).

* Allergic Reactions
1. Nausea, vomiting, skin rash, hives, wheals (urticaria) and / or itching (pruritus).
2. Shortness of breath, difficulty breathing, wheezing
3. Lump in the throat, difficulty talking or swallowing
4. Abdominal pain and/or sudden diarrhoea
5. Low blood pressure (feeling faint)
6. Feeling of doom or loss of consciousness
Training : All OT staff should be trained in basic CPR or BLS
Nowadays airplanes are very safe, that does not mean we don’t need pilots.