Seizures in 3 juvenile dogs after intravenous anesthetic drug withdrawal during weaning from mechanical ventilation suspected to be a sign of iatrogenic withdrawal syndrome

OBJECTIVE

To describe seizure activity in juvenile dogs successfully weaned from long-term mechanical ventilation.

CASE SERIES SUMMARY

Three juvenile dogs (all approximately 3 months old) underwent long-term mechanical ventilation with IV anesthesia for suspected noncardiogenic pulmonary edema. Within 24 hours of extubation and within 10 hours of discontinuing midazolam continuous infusions, all dogs experienced seizures, which is 1 sign of iatrogenic withdrawal syndrome. Each dog was treated with an anticonvulsant protocol, and none experienced seizures after being discharged.

NEW OR UNIQUE INFORMATION PROVIDED

Each dog received IV anesthesia, including fentanyl, dexmedetomidine, midazolam, and propofol, during mechanical ventilation and subsequently experienced seizures after successful weaning from mechanical ventilation. Juvenile dogs may be at risk for seizures after weaning from mechanical ventilation and IV anesthesia. Neurological monitoring and further research into an appropriate weaning protocol may prove beneficial in juvenile dogs requiring prolonged anesthesia.

Principles of mechanical ventilation

Mechanical ventilation is an enormous undertaking for a veterinary hospital in general and for any patient in particular. It is a team effort requiring large amounts of space, supplies, labor, and time. It requires committed owners and clinicians who communicate clearly with each other. It also requires a significant financial commitment initially from the hospital to obtain the equipment and expertise and then from the owner to maintain the patient. All members of the patient care team should have a basic understanding of respiratory physiology and ventilator mechanics. Clear goals for therapy and end points should be established. If they cannot be met, the goals should be reassessed in light of changes in patient condition. Weaning may be difficult and long, but once successful, it is most rewarding for the patient, family, clinician, and team.

Weaning from mechanical ventilation

Patients that require positive pressure ventilation to maintain sufficient alveolar ventilation or pulmonary gas exchange may eventually reach a point in the course of their care wherein mechanical ventilation is no longer necessary. This process of transferring the work of breathing from the ventilator back to the patient is referred to as ventilator weaning. The term "ventilator weaning" may be used to refer to all methods by which this transfer of workload may be accomplished. In many patients, particularly those with short-lasting or readily correctable causes of respiratory insufficiency (e.g., general anesthesia), the discontinuation of positive pressure ventilation may be easily achieved. Indeed, in patients awakening from general anesthesia, the axiom "awake enough to blink, awake enough to breath" may prove to be a sufficient guideline. However, in those patients requiring long-term mechanical ventilatory support, the process can prove to be both frustrating and exceptionally challenging. It is of crucial importance to identify those patients that may be successfully weaned because of both the financial impact of prolonged intensive care unit hospitalization and the risks imposed on the patient by the process of positive pressure ventilation. To be able to predict which patients may be ready to be weaned from the ventilator requires an understanding of the balance between the work of breathing (ventilatory load) and the ability of the patient's respiratory pump to meet those needs (ventilatory capacity). The management of patients experiencing difficulty during the weaning process requires that the clinician recognize imbalances between ventilatory load and capacity and to correct these imbalances once identified.