Using a 0.035-in. straight-tip wire and a small infant laryngoscope for safe and easy endotracheal intubations in rats for cardiovascular research

Objectives: Endotracheal intubation in rats is a challenging problem. This is a difficult procedure due to the narrow oral cavity and the difficulty in visualizing the vocal cord. It is associated with high complication rate. We have developed a very safe and simple method using a 0.035-in. straight tip wire as a guide and the small infantile laryngoscope for intubation in rats. Method: Seventy Sprague-Dawley rats weighing between 100 and 450 g were used for endotracheal intubation, utilizing a 0.035-in. straight-tip wire, infantile laryngoscope blade Miller size 0 and conventional cutdown 18-gauge catheter. Rats were anesthetized using a mixture of ketamine (50 mg/kg), xylazine (4 mg/kg) and acepromazine (1 mg/kg). The upper incisors were fixed with a rubber band. With the laryngoscope, the trachea and vocal cords were visualized with the tongue pulled back. Under direct visualization of the vocal cords, a 0.035-in. straight-tip wire was advanced into the trachea and an 18-gauge cutdown catheter was advanced over the wire into the trachea. The wire was removed and the catheter was attached to the respirator. With this method, the use of atropine was not necessary. Results: We successfully intubated all 70 rats without any complications. The successful rate was 100% with no mortality related to the intubation. This was performed within 1 to 2 min after induction of anesthesia without using atropin. There was no intra-esophageal or soft tissue intubation. Conclusion: With a 0.035-in. straight-tip wire as a guide and a small infant laryngoscope blade Miller size 0, endotracheal intubations in rats can be safely performed with high success rate without the use of atropine, which makes it better suitable for cardiovascular research.