Patients whose shock has not responded to volume expansion and other interventions may require various inotropic or pressor support. Invasive monitoring should be considered for patients who are refractory to volume expansion and initial inotropics.
The choice of agent may be determined by some of the known pharmacological actions of the toxin involved, generally does the toxin cause pump (inotropic with or without negative chronotropic effects) failure or peripheral vasodilation, or a combination of both. Most patients with drug induced shock have low systemic vascular resistance.
Adrenaline in conjunction with high dose diazepam appeared to have efficacy in chloroquine poisoning. The initial dose for adults is 1 µg/min titrated to desired haemodynamic response (2-10 µg/min).
Dopamine is an initial pressor of choice (75% response) for diltiazem overdose, it should be used in high doses (10-20 microg/kg/min). Isoproterenol produces a therapeutic response in 50% of patients. These agents are often ineffective as a chronotropic agent when there is a high degree of conduction block as their action is predominantly through increasing the frequency of impulses originating in the SA node.
Norepinephrine is “indicated in patients with severe hypotension (systolic blood pressure less than 70 mm Hg) and a low total peripheral resistance. Patients with refractory shock may require 8 to 30 µg/min of norepinephrine.
Isoprenaline may be used for beta blocker poisonings but as it has to compete directly with the beta receptor high doses may be required.