No abstract

Despite current clinical practice, there is no objective evidence to demonstrate the efficacy or pain on injection when hyaluronidase is added to lidocaine as an anesthetic combination for local anesthesia. To evaluate the usefulness of hyaluronidase added to lidocaine in affecting pain on injection and effectiveness of local anesthesia, a prospective, randomized, double blind study comparing 1% lidocaine preparations with and without hyaluronidase (15 U/cc) was conducted. A paired experiment was done with each subject receiving both treatments. Solutions of these local anesthetics were prepared. A 0.5-cc intradermal injection of each was administered to the dorsum of the nondominant hand of 25 volunteers. After showing study participants a standard pain with a peripheral nerve stimulator, pain of anesthetic infiltration was rated by the subject using a visual analog scale. The amount of tissue deformation on injection was assessed. The area of anesthetized skin surrounding each injection was measured at 1/2, 1, 2 1/2, 4 1/2, 8, and 12 minutes after injection. The area of anesthesia achieved by 1% lidocaine infiltration can be significantly enhanced by the addition of hyaluronidase at a concentration of 15 U/cc (p = 0.0003). This raises the pH of the anesthetic to a slightly more physiologic level (6.33 versus 6.20) and makes the pH closer to the pK of the lidocaine. In addition, the hyaluronidase additive significantly decreases the amount of tissue distortion (p < 0.0001) without decreasing the efficacy of anesthetic action (p = 0.01). However, adding hyaluronidase to 1% lidocaine significantly increased the pain on injection (p = 0.0002). The injections of small amounts of hyaluronidase-containing solutions in this experiment did not produce any visible effects at 5 to 7 days after injection; however, the effect of hyaluronidase upon wound healing was not studied.

Retrobulbar hematoma leading to visual impairment is a rare but serious complication associated with elective blepharoplasty. A review of the literature addressing etiology, prevention, and management is presented. Removal of anterior orbital fat associated with traction and rupture of vessels within posterior orbital fat is currently most strongly supported as the cause of retrobulbar hematoma after blepharoplasty. Optic nerve ischemia is identified as the likely cause of visual impairment. Specific recommendations for avoidance and management of acute retrobulbar hematoma are offered. Recent background animal and human research is summarized.

A review of 134 cases of ketamine-induced intravenous sedation was undertaken. It was concluded that (1) whereas properly titrated midazolam with low-dose ketamine (0.5 mg/kg) can provide almost complete absence of behavioral problems and complete analgesia, transient oxygen desaturation may be seen, and (2) the induction phase of ketamine is an opportunity for the surgeon to rehearse mask ventilation.