Utility of Rocuronium-Sugammadex Combination to Induce Apnea in Dogs Undergoing Stereotactic Radiation Therapy

Stereotactic radiation therapy (SRT) requires extreme precision due to its high dose per treatment, high total dose, and very small error margins. Even small positioning errors may result in serious normal tissue toxicity or underdosing the tumor. Respiratory motion (resulting in tumor motion) represents a significant challenge to the delivery of SRT in some tumor types. A retrospective study of pet dogs receiving a rocuronium-sugammadex combination (ROC-SUG) as a means of inducing apnea was performed. The study included 14 pet dogs (43 treatments; 1-5 treatments per patient) undergoing SRT. A bolus of ROC was effective in preventing spontaneous breathing during treatment in 3/11 (27%) treatments and in 28/32 (88%) treatments when an ROC constant rate infusion (CRI) was given throughout treatment delivery, following the initial bolus. The median duration of apnea per treatment session was 6 min (range 4-7 min). The longest period of apnea during any treatment without interruption was 7 min. Adverse effects encountered during treatment include hypercapnia, bradycardia, and hypotension. Hypercapnia was observed in 34/43 treatments (79%). However, only 1/43 treatments (2%) resulted in bradycardia and hypotension, which were rapidly reversed. All dogs recovered rapidly following SUG with complete neuromuscular blockade reversal in a median of 1 min (range: 1-2 min), and there was no evidence of recurarization in any patient. The ROC-SUG combination, particularly when used with an ROC CRI, facilitated the induction of apnea without significant adverse effects. Future studies should use a uniform treatment protocol to confirm efficacy and patient safety.