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Reply To: Managing degranulation reactions in MCTs

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Hello Emma.

Hope you are safe and well. I think your comments above are really valid regarding pre-treatment. That is definitely a really important step. Otherwise, I would treat as any anaphylaxtic reaction. Thankfully I have not been in this situation many times either!

Initial treatment of a dog or cat with anaphylaxis consists of the basics of emergency medicine and the administration of adrenaline. A patent airway and effective breathing/ventilating should be confirmed immediately. Respiratory distress can result from upper airway obstruction, necessitating intubation with an endotracheal tube or tracheostomy if intubation is not possible. If respiratory distress without airway obstruction is present, oxygen should be administered by mask or flow-by during initial assessment and stabilization, and then by nasal catheter or oxygen cage. Hypovolemic shock is a significant contributor to morbidity and mortality in anaphylaxis. Hypovolemia occurs secondary to increased vascular permeability and venous pooling. Ongoing crystalloid therapy usually will be necessary at rates higher than maintenance to keep up with ongoing losses and will need to be tailored to the individual patient.

Regarding adrenaline (taken from Ettinger); traditionally, a dosage of 0.01 mg/kg given slowly IV is recommended, although 0.02 mg/kg can be given into the trachea if the patient is intubated and IV access cannot be obtained. A maximum dose of 0.5 mg IV for patients weighing >40 kg is recommended. Adrenaline also can be administered IM at a dosage of 0.01 mg/kg. Doses can be repeated every 5-15 minutes as needed. Adrenaline is useful because of its inotropic and chronotropic effects on the heart as well as vasoconstriction. Adrenaline also causes bronchodilation and increased intracellular concentrations of cyclic adenosine monophosphate, which decreases synthesis and release of inflammatory mediators of anaphylaxis. A single dose of adrenaline given IV, IM, or SC after maximal hypotension had developed did not produce a sustained improvement in hemodynamic parameters in a study on dogs with induced anaphylactic shock; only the IV dose produced a transient improvement (<15 minutes) in mean arterial pressure, stroke volume, and pulmonary wedge pressure. A later study of anaphylaxis induced in dogs showed that administration of adrenaline by constant rate intravenous infusion (CRI) was the only route that caused sustained improvement in hemodynamic parameters compared to the nontreatment group and the groups that received a bolus given IV, SC, or IM. The dosage used for the IV CRI was 0.05 mcg/kg/min. These studies suggest that adrenaline acts primarily as a vasopressor rather than specifically improving immunologic recovery. Consideration should be given to administering adrenaline as a CRI rather than an IV bolus.

Other medications that can be useful in the treatment of systemic anaphylaxis include vasopressors, glucocorticoids, antihistamines, aminophylline, and atropine. Dopamine at a dosage of 5-10 mcg/kg/min IV CRI or norepinephrine at a dosage of 0.01-1 mcg/kg/min IV CRI can be used if refractory hypotension is present. Vasopressin (0.5-1.25 mU/kg/min IV CRI) can be used if the patient is refractory to fluid and catecholamine therapy. Aminophylline or a selective beta2 agonist such as albuterol may be used if bronchoconstriction is refractory to adrenaline.

I hope that helps!

Scott x