Systemic Complications of Anesthesia in Elective Eye Surgery

Introduction:

Eye surgery is also called ophthalmic or ocular surgery. An eye specialist performs it called an ophthalmologist. Elective eye surgery means surgery that need not be done immediately but has to be done sometime. The primary goal of anesthesia is to provide painless, safe, and successful surgery with no or minimal perioperative complications.

What Is the Normal Structure of the Eye and What Does It Do?

• The eye or orbit is located in a bony socket protected by small skull bones on all sides. It is pyramid-shaped, with a base toward the outside and an apex toward the back.

• Each orbit contains eyeballs, also known as globes.

• The globe is suspended in the front region of the orbit.

• The ophthalmic nerve, a branch of the trigeminal nerve, gives the sensory supply to the eye.

• Six extraocular muscles attached to the sclera, the white portion of the globe, regulate eye movements.

• The muscles are supplied by the oculomotor, trochlear, and abducens nerves.

• It helps the eye to move up and down, right and left, and to rotate the eyeball.

What Are the Indications of Anesthesia in Eye Surgery?

Patients who can communicate and cooperate during the procedure will be given local anesthesia. General anesthesia is required in children, patients who can not control their eye movements, and patients who are uncooperative and have difficulty communicating. The indications for ocular anesthesia are:

• Cataract removal

• Corneal transplantation

• Strabismus repair

• Glaucoma

• Vitreoretinal surgery

• Scleral buckling

• Enucleation

What Are the Contraindications of Anesthesia in Eye Surgery?

• There are certain conditions when anesthesia should be contraindicated during surgery like:

  • Allergic reaction to any of the anesthetic drugs

  • Nystagmus

  • Malignant hyperthermia

• There are some relative contraindications to anesthesia like:

  • Age of the patient (especially in children)

  • Dementia

  • Parkinson’s disease

  • Eye infection

  • Long axial length of eye

  • Inability to lie in a supine position

What Are the Ophthalmic Complications of Ocular Anesthesia?

• Administration of anesthesia can carry the risk of complications around the time of surgery, which are broadly classified into two types: Ophthalmic and systemic complications.

• Ophthalmic complications occur in and around the eye region or are related to the eye. It is seen during local or regional anesthesia.

1. Retrobulbar hemorrhage

2. Optic nerve damage

3. Globe perforation

4. Chemosis (conjunctival edema)

5. Subconjunctival hemorrhage (ecchymosis)

6. Myotoxicity

What Are the Systemic Complications of Ocular Anesthesia and How Are They Prevented?

When general or local anesthesia is given, systemic complications occur concerning other body parts.

1. Oculocardiac reflex:

1. It is a trigeminal-vagal reflex that occurs during strabismus surgery for children.

2. It is exaggerated by higher levels of acid in the blood, lower levels of oxygen in the blood, and hypoventilation.

3. This reflex causes cardiac arrest.

4. It is characterized by hypotension, severe bradycardia, and bradyarrhythmia. The risk factors are pulling off any ocular muscle, eye pain, pressure on the globe, and manipulation of the eyeball.

5. Prevention:

• Surgical stimulation of the eye should be stopped.

• Atropine is a better choice for increasing the heart rate.

• Glycopyrrolate can be given.

2. Respiratory arrest:

1. It occurs with the retrobulbar technique of anesthesia in which local anesthetic is given in the retrobulbar space present behind the globe.

2. It occurs because of an eye-breathing reflex that shows up as shallow and slowed breathing. It occurs due to pressure and manipulation of the eye, so it mostly occurs during strabismus surgery.

3. Prevention:

• By using a laryngeal mask airway (LMA) to secure the airway.

3. Systemic toxicity:

1. It often occurs during local anesthesia when there is an overdose or accidental intravascular (into the bloodstream) injection.

2. Confusion, convulsions, loss of consciousness, and respiratory or cardiac arrest are the symptoms.

3. Prevention:

• This type of complication can be avoided with a clear understanding of ocular anatomy and the support of an anesthesiologist.

• Treatment is intravenous administration of a 20% lipid emulsion in a 1.5 ml/Kg bolus followed by a 0.25 ml/kg/minute infusion.

4. Facial nerve block complications:

1. During retrobulbar blocking, the orbicularis oculi muscle is blocked.

2. It can cause hemifacial palsy and local anesthetic spread into the vagus, glossopharyngeal or spinal accessory nerve, and neurogenic pulmonary edema.

3. Prevention:

• Modern and advanced needle block techniques can block only the terminal part of the facial nerve, so there is no need to block the orbicularis oculi muscle.

5. Allergic reaction:

1. It is a common complication with amide-type local anesthetic drugs such as Lidocaine and Bupivacaine.

2. Prevention:

• Before surgery, a thorough evaluation should be done to determine if the person has ever had an allergy to these local anesthetics.

6. Pulmonary edema:

1. This complication occurs when the peribulbar block is given outside of the muscle cone in the peribulbar space.

2. It manifests as an initial symptom of local anesthetic toxicity, leading to difficulty breathing and desaturation.

3. They occur alone or with other symptoms of toxicity.

4. Management:

• This complication is reversible. So, constant monitoring with the help of an anesthesiologist is important to manage this.

7. Brainstem anesthesia:

1. The spread of local anesthesia into the central nervous system happens through the perforation of an optic nerve because the optic nerve is enclosed inside a sheath that fuses with the outer layer of the nerve and ends in the sclera.

2. The spread occurs subdurally when an injection is made to the optic nerve sheath.

3. Rarely central spread occurs via the orbital artery when a needle tip perforates it. The backward flow of anesthetic agents can occur from the ophthalmic artery to the midbrain.

4. This complication is characterized by palsy of the contralateral (opposite) oculomotor and trochlear nerve and amaurosis (temporary loss of vision due to a lack of blood flow to the retina).

5. Other symptoms include aphasia, vomiting, temporary hemiplegia, convulsions, tachycardia, hypertension, severe shivering, confusion, agitation, and unconsciousness.

6. Prevention:

• Needles should always be aspirated before injection to avoid intravascular injection.

• Blocks given inside and outside the cone of the orbit should be done with the patient in a primary gaze position (eyes looking forward with head straight).

• A needle injection should not be given too deeply where the optic nerve binds with the sheath.

• Treatment includes providing cardiac and respiratory support. Ventilation through the bag and mask is required.

• There is a spontaneous resolution of this complication.

Conclusion

Proper preparation, planning of elective eye surgeries, and using safe anesthetic agents and techniques by skilled and experienced anesthesiologists can achieve successful orbital anesthesia without any potential systemic complications. And in case of any sudden complications, a well-trained team of nurses, physicians, surgeons, and anesthesiologists should always be available during surgery. It should be able to recover the patient effectively.