Authors

H R M A Barker and C M Moore

Summary

A 76yr old with complicated medical and ophthalmic history successfully underwent penetrating keratoplasty under sub-Tenon’s anaesthesia with no sedation. No postoperative complications occurred and no postoperative analgesia was required. Risks of penetrating keratoplasty under local anaesthesia are discussed.

Keywords

Anaesthetics, local: sub-Tenon’s.
Corneal graft; penetrating keratoplasty.

Introduction

In our institution, as in the United Kingdom in general, corneal graft surgery is routinely performed under general anaesthesia (G.A.) as an inpatient procedure1 because:

1. A G.A. with muscle relaxation provides a more controlled environment with the patient less likely to cough or move. Orbicularis oculi is relaxed so eyelid squeezing does not occur. The patient is unconscious and therefore there is no risk of anxiety, restlessness or confusion resulting in a sharp rise in intra-ocular pressure (i.o.p.), which increases the risks of prolapsed global contents or expulsive haemorrhage. The intra-ocular pressure is more easily controlled.
2. Penetrating keratoplasty is an ‘open sky’ procedure and therefore carries an increased risks of loss of global contents and expulsive haemorrhage than closed procedures especially if other procedures such as extracapsular cataract extraction or vitrectomy are performed at the same time.
3. The eye is in its virgin state unaffected by volume effects of the local anaesthesia (increased i.o.p.,chemosis, retinal vein +/- artery occlusion) or by needle or cannula damage( vessels, muscles, sclera and retina) or by direct damage of the optic nerve or central nervous system by local anaesthetic.
4. There is no constraint on the time required to perform the operation.

We report the case of successful corneal graft surgery performed under sub-Tenon’s local anaesthesia.

Case History
A 76 year old retired solicitor was referred to the ophthalmic service for penetrating keratoplasty under G.A. as treatment for pseudophakic bullous keratopathy of his right eye. He was a manic depressive psychotic on Lithium and Paroxetine; 40 a day smoker with a chronic cough and chronic obstructive airways disease on Salbutamol and Becotide inhalers; obese on Ranitidine for symptomatic hiatus hernia; in atrial fibrillation with a ventricular rate of 76 bpm controlled by Digoxin and on Asprin 75mg/day stopped 2 days prior to surgery; ischaemic heart disease on Amlodipine ; episodes of congestive cardiac failure in the past; glaucoma R eye (L eye blind due to glaucoma); had R phacoemulsification cataract surgery + posterior chamber IOL 18 months ago under sub- Tenon’s block. Blood investigations were normal except for a platelet count of 137,000 (150,000-> 400,000 normal values). His ecg showed atrial fibrillation, inferior ischaemia with possible inferior subendocardial damage and anterolateral ischaemia.

Stress echocardiogram taken the previous year revealed limited MI and impaired L ventricular function. An angiogram performed at that time showed triple vessel coronary artery disease. He was considered too high a risk for coronary artery bypass grafting, angioplasty had failed and he continued to smoke and drink heavily. He was told by his cardiologist that a general anaesthetic would kill him.

The decision was made to perform his graft surgery under sub-Tenon’s anaesthesia without sedation.

In the anaesthetic room, routine monitoring was applied and his preoperative observations were a blood pressure of 130/75, respiratory rate 20 breaths per min, pulse rate 78bpm irregularly irregular. An intravenous cannula was sited. 2drops of 0.4% Benoxinate and 2 drops of 1% Amethocaine were placed into the right eye. The skin was cleansed with 10% Providone-Iodine aqueous solution. A Barraquer lid speculum was inserted at which point the patient complained of pain. 2 more drops of 1% Amethocaine were applied and the speculum was repositioned. The patient was asked to look up and to the right. Conjunctiva and Tenons was grasped with Moorfields forceps 7mm from the limbus at a point midway between the insertions of the medial rectus and the inferior rectus muscles. A small incision was made with blunt ended Westcott scissors at the base of this tent of tissue revealing gleaming white sclera and the closed blunt ends of the scissors used to create a path along posterior subTenon’s space. A blunt ended 19G one inch subtenon’s cannula was introduced into the path and a mixture of 2.5ml Lidocaine 2% and 2.5ml Bupivacaine 0.5% and Hyaluronidase 1,500IU injected. The eyelid was then closed and gentle manual pressure applied for 5 minutes. The patient was told that if he coughed during the procedure, that there was a high risk of him losing his vision. No sedation was given to ensure that the patient remembered this fact. The patient was made comfortable in a slight head up position, and oxygen enriched air flushed under the sterile drapes to maintain oxygenation (saturation was 99% during surgery) and remove carbon dioxide during surgery. Surgery commenced 10min after the block was given, lasted 30 min and was without complication. As the patient was pseudophakic, a Flieringa ring was used to support the sclera during surgery.

Post operatively the patient remained in a head up position and was eating 1 hour after his operation. He required no postoperative analgesia and was discharged on the second postoperative day on Desamethasone and Chloramphenicol drops qds and Xalatan and Trusopt once daily.

Discussion

We have found no reports of corneal graft surgery under sub-Tenon’s anaesthesia in the literature. Penetrating Keroplasty has been performed under retrobulbar block with2 and without3 sedation as daycases, under peribulbar block4 and under topical (4% Lidocaine HCL) anaesthesia + facial block + intravenous opiate +/- intracameral Lidocaine5. All reports found good operating conditions and patient acceptance. Sub Tenon’s block has been shown to have advantages over retrobulbar (blind needle), peribulbar (blind needle, large volume), topical (no akinesia, less analgesia) techniques. Amaurosis is an advantage as is orbicularis oculi block without the need for painful facial nerve block.

Anaesthetic agents used have been mixtures of Lidocaine and Bupivacaine with hyaluronidase or Etidocaine and Bupivacaine with Hyaluronidase or Etidocaine and Bupivacaine with hyaluronidase to speed onset of the block and promote tissue spread thus helping to reduce volume/ pressure effects. Epinephrine or phenlyephrine were added to some agents to prolong the duration of local anaesthetic action (duration of action of Bupivacaine is unaffected) and possibly to counteract local anaesthetic block of sympathetic fibres in the short ciliary nerves which would otherwise produce vasodilation of uveal blood vessels promoting choroidal effusion or increasing the risk of choroidal haemorrhage.

Long acting local anaesthetic of low but adequate volume together with prolonged compression/ message (>12min) pre surgery is recommended.

One report4 suggest that analgesia may be less effective in cases of bullous Keratopathy where the eyes are inflamed or congested. In our patient this could account for the initial pain on inserting the speculum. The use of intravenous osmotic agents immediately prior to surgery is recommended to decrease the risk of choroidal bleed and globe prolapse. Avoiding spikes in systolic blood pressure (by blood pressure monitoring), avoiding venous obstruction (by careful head positioning) and coughing (by the prescription of 30mg codeine linctus preoperatively) and maintaining a head up position where possible are important measures. Pressure effects of the lid speculum on globe contents should be considered.

The risk of suprachoroidal haemorrhage as a complication of penetrating Keratoplasty has been noted as 0.56% under G.A.6 and 1% ->4% under L.A.4  6 . Risk factors include increasing age, hypertension, diabetes, atherosclerotic vascular disease and obesity, and an ocular history of myopia, glaucoma, previous ocular inflammation or surgery. Our patient was on aspirin and had a slight fall in his platelet count. His platelet function was unknown. He was at an increased risk of haemorrhage and blind needle technique would have increased this further.

Although sub-Tenon’s anaesthesia maintains or reduces intra-ocular pressure, we are uncertain of its effect on ocular blood flow (pulsatile blood flow) hence there is a potential risk of reducing vision in patients with glaucoma7.

Sedation + a dark environment may produce sleep with loss of control or confusion in the elderly hence this was avoided in our patient.

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References

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4. Muraine M, et al. Peribulbar anaesthesia during keratoplasty: a prospective study of 100 cases. Br J Ophthalmol 1999; 83: 104-109.
5. Yavitz EQ. Topical and intracameral anaesthesia for corneal transplants (letter). J Cataract Refract Surg 1997; 23: 1435.
6. Ingraham HJ., Donnenfeld ED., Perry MD. Massive suprachoroidal hemorrhage in penetrating keratoplasty. American J of Ophthalmology 1989; 108: 670-675.
7. Venkatesan. Pulsatile ocular blood flow and ophthalmic regional anaesthesia. Curr Opin Anaesthesiol Dec 2002; 15 (6): 615-620.