Pressure measurements during injection of corticosteroids: in vivo studies

Bridging a Century-Old Problem: The Pathophysiology and Molecular Mechanisms of HA Filler-Induced Vascular Occlusion (FIVO)-Implications for Therapeutic Interventions

Biocompatible hyaluronic acid (HA, hyaluronan) gel implants have altered the therapeutic landscape of surgery and medicine, fostering an array of innovative products that include viscosurgical aids, synovial supplements, and drug-eluting nanomaterials. However, it is perhaps the explosive growth in the cosmetic applications of injectable dermal fillers that has captured the brightest spotlight, emerging as the dominant modality in plastic surgery and aesthetic medicine. The popularity surge with which injectable HA fillers have risen to in vogue status has also brought a concomitant increase in the incidence of once-rare iatrogenic vaso-occlusive injuries ranging from disfiguring facial skin necrosis to disabling neuro-ophthalmological sequelae. As our understanding of the pathophysiology of these injuries has evolved, supplemented by more than a century of astute observations, the formulation of novel therapeutic and preventative strategies has permitted the amelioration of this burdensome complication. In this special issue article, we review the relevant mechanisms underlying HA filler-induced vascular occlusion (FIVO), with particular emphasis on the rheo-mechanical aspects of vascular blockade; the thromboembolic potential of HA mixtures; and the tissue-specific ischemic susceptibility of microvascular networks, which leads to underperfusion, hypoxia, and ultimate injury. In addition, recent therapeutic advances and novel considerations on the prevention and management of muco-cutaneous and neuro-ophthalmological complications are examined.

Dual-Drug Delivery via Zein In Situ Forming Implants Augmented with Titanium-Doped Bioactive Glass for Bone Regeneration: Preparation, In Vitro Characterization, and In Vivo Evaluation

In situ forming implants (IFIs) are non-surgical approach using biodegradable polymers to treat bone fractures. The study aimed at preparing dual-drug-loaded IFIs to deliver pitavastatin (osteogenic drug) and tedizolid (antibiotic) using zein as the implant matrix via solvent-induced phase inversion method. At first, several investigations were done on pitavastatin-loaded zein IFIs, where three concentrations of zein were used (10, 20, and 30% w/v). IFIs were evaluated for their solidification time, rheological properties, injectability, and in vitro release. IFIs containing bioactive glass nanoparticles were prepared by the addition of non-doped bioactive glass nanoparticles (BGT0; 1, 3, 5, and 10% w/v) or titanium-doped bioactive glass nanoparticles (BGT5; 1% w/v) to the selected concentration of zein (30% w/v) and then evaluated. The optimized dual-medicated implant (D-ZIFI 1) containing pitavastatin, tedizolid, sodium hyaluronate (3% w/v), and BGT5 (1% w/v) was prepared and compared to IFI lacking both sodium hyaluronate and BGT5 (D-ZIFI 2). D-ZIFI 1 and 2 sustained the release profiles of both drugs for 28 days. SEM images proved the interconnected porous structure of D-ZIFI 1 due to sodium hyaluronate. In vivo studies on surgically induced bone defects in Sprague-Dawley rats signified the proper accelerated bone healing ability of D-ZIFI 1 over D-ZIFI 2. Results presented D-ZIFI 1 as a promising, effective, non-surgical approach for bone healing.

In Situ-Forming Microparticles for Controlled Release of Rivastigmine: In Vitro Optimization and In Vivo Evaluation

In this work, sucrose acetate isobutyrate (SAIB) and polylactic co-glycolic acid (PLGA) were used alone or in combination as a matrix-former (MF) to prepare long-acting injectable rivastigmine (RV) in situ-forming microparticles (ISM). RV-ISM were prepared by the emulsification of an internal phase, containing the drug and the matrix former(s), into an external oily phase containing a stabilizer. The statistical design, Central Composite Design (CCD), was adopted as a quality by design (QbD) approach to optimize the formulation of RV-ISM systems. The fabricated RV-ISM systems was designed to minimize the initial burst drug release and maximize the sustainment of RV release from the ISM and ease of injection. The influence of critical formulation variables such as the matrix-former to drug (MF/D) ratio and SAIB to PLGA (S/P) ratio in the internal phase with respect to critical quality attributes (CQAs), such as the percentage drug release within the first day (Q₁), the time required for 50% drug release (T_50%) and the rate of injection, were studied using the CCD. The optimal RV-ISM system with the highest desirability value (0.74) was predicted to have an MF/D ratio of 11.7:1 (w/w) and an S/P ratio of 1.64:1 (w/w). The optimal RV-ISM system was assessed for its release profile, injectability, rheological properties, morphology, effect on cell viability, tolerance to γ-sterilization and in vivo performance in male albino rabbits. In vitro release studies revealed that the optimal RV-ISM system released 100% of its drug content throughout a release period of 30 days with only 15.5% drug release within the first day (Q₁) and T_50% of 13.09 days. Moreover, the optimal system showed a high injection rate of 1.012 mL/min, pseudoplastic flow, uniform spherical globules with homogenous particle size, minimal cytotoxicity and high tolerability to γ-sterilization. In vivo pharmacokinetic (PK) studies revealed that the rate of absorption of RV from the optimal RV-ISM system was controlled compared to a drug solution following either intramuscular (IM) or subcutaneous (SC) injection. Furthermore, the optimal RV-ISM was found to follow flip-flop PK with poor correlation between in vitro release and in vivo findings. These findings suggest that the optimal RV-ISM is a promising tool to achieve a sustained release therapy for RV; however, further investigation is still required to optimize the in vivo performance of RV-ISM.

Death Caused by Vaginal Injection of Hyaluronic Acid and Collagen: A Case Report

With the expanding utilization of hyaluronic acid (HA) and collagen as cosmetic fillers in plastic and reconstructive surgery, complications due to their excessive use and/or irregular procedures warrant great caution. Recently, a fatal case occurred caused by a poorly regulated procedure of vaginal injection of HA and collagen. A 33-year-old female was admitted to the emergency department 3 hours after the operation with a chief complaint of dyspnea, which initiated 5 to 10 minutes after the operation. Her blood pressure remained low while dopamine pressor and fluid replacement were used. Computed tomography of the chest showed local exudation in the lower lobe of the left lung, enlargement of right atrium and ventricle, and uneven development of the bilateral inferior lobar artery with filling defects. Pulmonary computed tomography angiography and three-dimensional reconstruction showed continuous interruption of pulmonary artery branches of the posterior basal segment of the right lower lobe. Unfortunately, the clinical symptoms caused by vaginal injection aggravated rapidly and could not be effectively controlled. The patient died 9 hours after injection. Pulmonary complications after injection of cosmetic fillers are scarcely reported. Thus far, only 2 cases of HA-related pulmonary complications after vaginal injection have been described. The present case emphasizes that surgeons and other healthcare providers must be aware of the risk of serious pulmonary complications and even death associated with these 2 widely utilized injectable fillers. Level of Evidence: 5.

Pathophysiology Study of Filler-Induced Blindness

Background

A number of authors have proposed retrograde arterial embolism as the responsible mechanism for filler-induced blindness. However, no previous human study has substantiated this proposed mechanism.

Objectives

The aim of this study was to investigate the pathophysiology of filler-induced blindness using a fresh cadaver perfusion technique.

Methods

A fresh cadaver head perfusion model that simulates both physiologic blood pressure and flow rate of the carotid artery, ophthalmic artery, and supratrochlear artery was used. The common carotid artery was cannulated and the internal jugular vein exposed for open venous drainage. A plasma-based perfusate was circulated through the cadaver head, which was connected to a perfusion system consisting of a roller pump, preload reservoir, and pressure monitor. The hyaluronic acid filler mixed with methylene blue was injected into the cannulated superficial branch of the supratrochlear artery. Cadaver dissection, angiographic study, and histology were used to investigate filler-induced blindness.

Results

Cannulation of the superficial branch of the supratrochlear artery was successful in all six cadavers. Emboli to the ophthalmic artery was successfully demonstrated in the three out of 6 fresh cadaver heads. The C-arm angiogram documented a cut-off sign in the ophthalmic artery due to hyaluronic acid filler emboli. An average intravascular volume of the intraorbital part of the supratrochlear artery was 50.0 µL. The average depth of location of the superficial branch of the supratrochlear artery from the epidermal surface was 1.5 mm.

Conclusions

Our cadaveric study demonstrated that retrograde hyaluronic acid filler emboli to the ophthalmic artery could be produced by the cannulation of the supratrochlear artery. The superficial location of the supratrochlear artery, the rich vasculature surrounding it, and the variability in the anatomy make this possible.

Reappraisal of astigmatism induced by periocular capillary hemangioma and treatment with intralesional corticosteroid injection

OBJECTIVE

To document refractive status and visual acuity before and after intralesional corticosteroid injection in children with astigmatism induced by periocular capillary hemangioma (PCH).

DESIGN

Retrospective, interocular comparison, interventional case series.

PARTICIPANTS

Thirteen infants with anisometropic astigmatism of at least 1.50 diopters (D) induced by PCH.

INTERVENTION

All infants had one or more intralesional corticosteroid injections of a PCH between 2 and 10 months of age. Injections of 0.3 to 1.0 ml of a 50:50 mixture of triamcinolone (40 mg/ml) and dexamethasone phosphate (4 mg/ml) were given at a single site under deep sedation.

MAIN OUTCOME MEASURES

Refraction and acuity using Teller acuity cards before and after injection.

RESULTS

In affected eyes, mean astigmatisms were 3.75 D (pretreatment) and 1.25 D (posttreatment), and mean spherical errors were 0.75 D (pretreatment) and 1.50 D (posttreatment). Reduction in astigmatism was observed within 1 to 14 months after the injection. Despite reciprocal changes in astigmatism and spherical error, the amount of anisometropia (spherical equivalent) remained constant. Amblyopia was not observed before treatment and was observed in only 2 of 13 children after treatment. Complications were limited to adrenal suppression with transient reductions of linear growth and localized eyelid necrosis.

CONCLUSIONS

Intralesional corticosteroid injections given in infancy (between 2 and 10 months) resulted in a 63% reduction in the mean amount of astigmatism induced by PCH. The reciprocal changes of astigmatism and spherical error without changes in anisometropia suggest that the treatment effect was due to restoration of the spherical shape of the cornea. Before 3 years of age, visual immaturity exceeded the optical blur related to astigmatism induced by PCH. Therefore, astigmatism, not anisometropia or amblyopia, is the immediate indication for treatment of PCH with intralesional corticosteroids. Injection of corticosteroid at a single site minimizes the potential for severe ocular complications owing to tissue pressure and tumor volume considerations.