Methylene blue dose-dependently induces cutaneous inflammation and heat hyperalgesia in a novel rat model.

Methylene blue (MB) has been shown to reduce mortality and morbidity in vasoplegic patients after cardiac surgery. Though MB is considered to be safe, extravasation of MB leading to cutaneous toxicity has been reported. In this study, we sought to characterize MB-induced cutaneous toxicity and investigate the underlying mechanisms. To induce MB-induced cutaneous toxicity, we injected 64 adult male Sprague-Dawley rates with 200 µL saline (vehicle) or 1%, 0.1%, or 0.01% MB in the plantar hind paws. Paw swelling, skin histologic changes, and heat and mechanical hyperalgesia were measured. Injection of 1%, but not 0.1% or 0.01% MB, produced significant paw swelling compared to saline. Injection of 1% MB produced heat hyperalgesia but not mechanical hyperalgesia. Pain behaviors were unchanged following injections of 0.1% or 0.01% MB. Global transcriptomic analysis by RNAseq identified 117 differentially expressed genes (111 upregulated, 6 downregulated). Ingenuity Pathway Analysis showed an increased quantity of leukocytes, increased lipids, and decreased apoptosis of myeloid cells and phagocytes with activation of IL-1ß and Fos as the two major regulatory hubs. qPCR showed a 16-fold increase in IL-6 mRNA. Thus, using a novel rat model of MB-induced cutaneous toxicity, we show that infiltration of 1% MB into cutaneous tissue causes a dose-dependent pro-inflammatory response, highlighting potential roles of IL-6, IL-1ß, and Fos. Thus, anesthesiologists should administer dilute MB intravenously through peripheral venous catheters. Higher concentrations of MB (1%) should be administered through a central venous catheter to minimize the risk of cutaneous toxicity.

Intraoperative inflation of laryngocele with LMA.

OBJECTIVES: Laryngoceles are pathologic air filled dilations of the laryngeal ventricle. They are most often benign and incidental findings. Resection may be necessary in the setting of infection, airway obstruction, dysphagia, and phonatory disturbances. External laryngoceles are almost universally treated with open resection via a lateral or midline cervical approach. Care must be taken to resect the laryngocele in its entirety to avoid recurrence. In cases of recurrent infection, normal surgical planes are often fibrosed and obscured increasing the risk of neurovascular sacrifice and functional losses. METHODS: We are reporting a case of recurrent infections in a large, palpable external laryngocele. During resection the patient was ventilated using an endotracheal tube (ETT). Additionally, a laryngeal mask airway (LMA) was inserted posterior to the ETT, resting in the hypopharynx and attached to a Jackson Rees circuit. Air was passed through the LMA to inflate the laryngocele and better define its borders. The LMA was also used to identify the root of the laryngocele in the paraglottic space and ensure its airtight closure. RESULTS: The LMA assisted our dissection and helped progress the surgery safely in a fibrosed surgical field. We have not seen this method described previously. The patient continues to be free of recurrence 2 years after surgery. CONCLUSION: While in most cases, with careful surgical technique, even a fibrotic and scarred laryngocele can be excised in its entirety without neurovascular sacrifice. In some cases where this may be difficult with a traditional approach, we offer the intra-operative trumpet maneuver as a viable method of better delineating the borders of a laryngocele.

Intraoperative epicardial ultrasound probe for visualization of embedded coronary arteries: a novel approach.

The identification of coronary anatomy at the time of cardiac revascularization can be problematic. Preoperative studies (ie, coronary angiography) can aid in the mapping of the coronary anatomy. However, there remain a select few patients with intramyocardial coronaries that provide challenges for surgical dissection during revascularization. Probing the visible portion of the coronary artery, intraoperative cine angiography, thermal angiography, and epicardial Doppler probes have been used to identify the coronary anatomy intraoperatively. Aggressive surgical maneuvers can result in damage and increased time on cardiopulmonary bypass. Previous studies have used epicardial echocardiography on patients undergoing off-pump coronary artery bypass grafting. We report 2 cases in patients undergoing cardiac revascularization on cardiopulmonary bypass where the use of a high-frequency epicardial ultrasound probe facilitated the identification of the embedded coronary arteries. We describe a technique of using antegrade and retrograde cardioplegia administration sequentially to locate the coronary arteries. Easy availability and familiar technology make the epicardial Doppler probe an attractive tool for the identification of embedded coronary arteries.