TORONTO - The volume of hyaluronidase should be administered according to whether a monophasic or polyphasic hyaluronic acid (HA) was injected into a patient, according to a plastic surgeon in private practice in Kitchener, Ontario, Canada. This also underscores the need for all injection specialists to have an intimate and meticulous knowledge of each filler product.
Speaking at the annual meeting of the Canadian Dermatology Association here about complications in fillers, Past President of the Canadian Society for Aesthetic Plastic Surgery Claudio DeLorenzi, M.D., F.R.C.S., former Surgeon in Chief in the Division of Surgery at St. Mary's General Hospital in Kitchener, noted that larger amounts of hyaluronidase and more frequent injections of it will be required when complications arise with the use of monophasic HA products, compared to polyphasic HA. The difference, he said, is related to the cross-linking of the respective types of HA products.
"You can have two patients who both have a filler problem, and you will need more hyaluronidase more often in a monophasic product," said Dr. DeLorenzi. "The attack surface of the matter that you are trying to enyzmatically degrade is orders of magnitude greater than in a polyphasic product. Polyphasic product degrades more quickly, and the rate of reaction is faster and the total amount of hyaluronidase needed is less."
Dr. DeLorenzi noted that whether hyaluronidase is able to penetrate the arterial wall is not a topic that has been well explored. He recently published work that illustrated cross-linked HA can be degraded with hydrolysis via hyaluronidase within the intact facial artery in a cadaver model, suggesting direct intra-arterial injection of hyaluronidase is probably not needed to help restore circulation of ischemic tissues. Dermaotologic Surgery. 2014 Aug;40(8):832-41.
"You apparently don't need to get into the artery itself (with hyaluronidase)," said Dr. DeLorenzi. "You just need to bathe the area around it with hyaluronidase."
Lump and bumps are common occurrences after injections with filling agents, and hyaluronidase is the treatment to resolve issues like swelling, said Dr. DeLorenzi.
"Patients can have persistent edema in the periorbital area," said Dr. DeLorenzi. "There may be numerous investigations, and it may be hyaluronic acid was the cause. Even a small amount of filler can cause persistent edema for a very long time, far longer than the expected duration of the filler agent."
If injectors are not well-versed with the anatomy in areas where they are injecting, there is increased potential for a complication like edema, said Dr. DeLorenzi. "It happens with anatomic structures in the peri-orbital area commonly if people are not familiar with the anatomy," said Dr. DeLorenzi. "Injectors should be injecting deep in the malar region."
The medical literature suggests that hyaluronidase should last up to 48 hours in soft tissues, but Dr. DeLorenzi reported that his clinical experience does not support that recommendation.
"That has not been my clinical experience at all," he said. "I think it is degraded much more quickly than that. Hyaluronidase turns over very quickly in the body."
In addition, the amount of hyaluronidase suggested is not adequate to resolve complications like necrosis, said Dr. DeLorenzi.
"The recommendations for treatment are on the order of 30 to 40 IUs," said Dr. DeLorenzi. "To my mind, this is horribly insufficient and ineffective, particularly with monophasic products like Juvederm and Voluma. They require much larger doses more frequently in order to achieve complete restoration of circulation."
When embolic events occur, they can affect not only skin, but they can also affect fat, muscles, and sometimes bone, according to Dr. DeLorenzi.
Clinicians should be aiming to optimize their use of hyaluronidase such that there is complete reversal and restoration of normal circulation, said Dr. DeLorenzi.
"If there has been progression to ischemic necrosis, and you have epidermal slough, that is a treatment failure," said Dr. DeLorenzi. "Usually, the cause is an insufficient amount of hyaluronidase."
Non-HA fillers produce more severe complications than HA fillers. "Hyaluronic acid fillers are different from particulate fillers like PMMA (polymethyl-methacrylate)," said Dr. DeLorenzi. PMMA injection can result in complete obstruction of circulation resulting in severe tissue loss, but this type of problem is not seen with HA fillers properly treated with hyaluronidase, he said.
Variables like total volume injected into the vessel, rapidity of injection, the amount of pressure applied, and flow rate influence the risk of necrosis, said Dr. DeLorenzi.
Clinicians should not have see cannulas as making injections of fillers a foolproof endeavour. "I have seen intra-arterial events despite cannula use," he said. "They reduce the risk, but they do not completely eliminate the risk (of intra-arterial events)."
Further study is needed to elucidate the risks associated with filler injections, according to Dr. DeLorenzi.
Dr. DeLorenzi had no relevant disclosures.