Cryoanalgesia affords drug-free anaesthesia for phaco

By Cheryl Guttman

ORLANDO, FL - Cryoanalgesia is a safe and viable method for mitigating pain and discomfort in patients undergoing phacoemulsification, reported surgeons experienced in the technique at the annual meeting of the American Academy of Ophthalmology
Cryoanalgesia involves operating in a cooled environment created by preoperative cooling of the eye and use of chilled fluids.
Proponents say cryoanalgesia minimises pain and inflammation by diminishing the release of endogenous chemicals mediating those reactions and by decreasing corneal metabolism.
Spanish ophthalmologist Francisco J. Gutiérrez-Carmona MD, PhD presented the results of a randomised, blinded, comparative study performed with Jorge Alvarez-Marín, MD, PhD.

That trial comprised 82 eyes of 82 patients and, with very few exceptions, found no significant differences between the groups in operative length, incidence of complications, patient reported levels of pain, physiological responses or surgeon intraoperative comfort during various steps of the surgery.
The two study groups were well balanced in age, gender and nuclear density. The protocol excluded patients deemed uncooperative or who had difficulty expressing their pain level using a rating scale.
Also excluded were monocular individuals, and those with hypermature cataracts, narrow anterior chambers or those who achieved pharmacological mydriasis of less than 5.0 mm.

The topical anaesthesia group received two drops of a mixture of 1% tetracaine hydrochloride and 4% oxybuprocaine hydrochloride three times beginning 10 to 15 minutes before surgery.
Patients in the cryoanalgesia group received two drops of balanced salt solution (BSS) preoperatively according to the same regimen. In both groups, cold (4ºC) BSS was used to irrigate the ocular surface throughout surgery. Patients received no sedatives preoperatively or any non-steroidal anti-inflammatory drops.

Physiological responses to surgical stress, evaluated by monitoring heart rate and blood pressure, showed no significant differences between groups throughout surgery.
However, maximum blood pressure was significantly higher at the time of corneal incision hydration in the cryoanalgesia group, while two patients in the topical anaesthesia group required antihypertensive treatment, he noted.

Using a 4-point scale (0=none; 1=little; 2=some; 3=much), patients were asked to rate their pain at each of the following phases of surgery: speculum insertion; paracentesis; corneal incision; CCC; hydrodissection; phacoemulsification; cortex aspiration; IOL implantation; and incisional stromal hydration, as well as at 24 hours postoperatively.
In both groups, paracentesis, corneal incision and IOL implantation were the most painful steps, but the mean pain scores at those steps were just ‘1’ or slightly higher.

The only statistically significant difference between groups was observed during paracentesis, when patients operated on under cryoanalgesia reported significantly more pain than their counterparts in the topical anaesthesia group.
Nevertheless, the mean pain score in the cryoanalgesia group was less than 0.5. One patient in the topical anaesthesia group required intraoperative sedation.
The study also investigated the surgeon’s perspective on comfort during the different steps of the procedure. There were no statistically significant between-group differences in surgeon stress at any step during the procedure or in the overall evaluation.

Patient satisfaction was high in both study groups with 40 (95.2%) patients in the cryoanalgesia group and 39 (97.5%) patients in the topical anaesthesia group indicating they would undergo the same surgical technique again.
Three patients in the study underwent bilateral surgery with cryoanalgesia in one eye and topical anaesthesia in the fellow eye. Two of those individuals indicated a preference for cryoanalgesia.
Not only was cryoanalgesia well tolerated by the patients, the technique has a number of potential advantages compared with topical anaesthesia, Dr Gutiérrez-Carmona observed.

"We have found cryoanalgesia can be a very useful technique, although just as with surgery performed under topical anaesthesia, you need to select patients carefully based on their expected level of co-operation.
"Not only does cryoanalgesia allow us to operate comfortably on patients who are allergic to anaesthetics, but it may also improve postoperative outcomes," he said.
Dr Gutiérrez-Carmona added that with cryoanalgesia there is no exposure to medications and the cold irrigation might help reduce postoperative inflammation by diminishing uveal sanguineous flow and stabilising the blood-aqueous barrier.
In addition, it may minimise endothelial trauma from the heat of the phacoemulsification tip and the low temperature environment might inhibit growth of bacteria which could contribute to endophthalmitis. He said he hopes to study these benefits further in the future.

Tobias H. Neuhann MD concurs that no-anaesthesia cataract surgery facilitated with the use of cold fluids is a valuable technique. He said it is particularly useful in older patients who have a large arcus senilis and who understand that the surgery will not be sensation-free.
In contrast to Dr Gutiérrez-Carmona, Dr Neuhann does not offer this alternative approach routinely to his cataract surgery patients.

However, he said he has found it has a definite place for patients who are allergic to ‘caine’-type anaesthetics as well as for those who are opposed to medication use, either because they have a drug phobia, a distrust of medications or are strong believers in their body’s self-healing potential.
"When I first heard of no-anesthesia cataract surgery, I didn’t believe it was possible. However, I was convinced otherwise after watching Dr Amit Agarwal operate. I am not discussing it routinely with patients because considering the culture of older, German patients, I expect most would reject the idea of surgery without anaesthesia," Dr Neuhann said.

He added that he has found there is a niche for this technique, both for patients who need it and those who seek it. Rather than trying to argue and convince the latter patients to have topical anaesthesia, Dr Neuhann said he is prepared to offer a no-anaesthesia procedure and that makes his life as a surgeon easier.
Dr Gutiérrez-Carmona said he is currently searching for a laboratory that will manufacture a viscoelastic material which can maintain a cold temperature for a longer period.

Dr Neuhann noted that he favours Healon 5 (Pharmacia) as his viscoelastic of choice for the no-anaesthesia procedures because it enhances chamber stability and protects sensitive ocular tissues.
"When operating without an anaesthetic, it is important to perform phacoemulsification very carefully to avoid excessive pressure fluctuation that can cause pain. Healon 5 helps to minimise those events and also perfectly protects the cornea and iris," he explained.

Dr Gutiérrez-Carmona MD, PhD first introduced this strategy in 1999 as a variation on the no-anaesthesia technique developed by Dr Agarwal.
Dr Gutiérrez-Carmona says he now offers the cryoanalgesia option to any patient who he deems a candidate for topical anaesthesia and has found it is associated with high patient acceptance.