Pharmacoepidemiology of metaraminol in critically ill patients with shock in a tertiary care hospital.

BACKGROUND: Metaraminol is increasingly used as a vasopressor in critically ill patients. Nevertheless, there remains limited evidence to support its use in international guidelines for management of shock. OBJECTIVES: The aim of the study was to describe the pharmacoepidemiology of metaraminol in critically ill patients with shock. METHODS: A retrospective observational study was conducted in an intensive care unit (ICU) in Sydney, Australia. Patients admitted during a 1-year time frame who received metaraminol intravenous infusions for management of shock were included. RESULTS: A total of 152 patients were included. When metaraminol was used, it was the most common first-line vasopressor started for management of shock (97%, n = 147) and was used as monotherapy in 53% (n = 81) of patients. The median duration of metaraminol infusion in the ICU was 7 h (interquartile range [IQR] = 3 to 19), and the median maximum metaraminol infusion rate in the ICU was 4.0 mg/h (IQR = 2.5 to 6.0). Peripheral vasopressor infusions were used in 96% (n = 146/152) of patients for a median duration of 7 h (IQR = 2 to 18). In all these cases, the peripheral vasopressor used was metaraminol (100%, n = 146/146). Patients were commonly switched from metaraminol to noradrenaline infusions after insertion of a central venous catheter (R2 = 0.89). Patients treated with metaraminol monotherapy had a lower Acute Physiology and Chronic Health Evaluation III score (58 vs 68; median difference = -9, 95% confidence interval = -16 to -3; p < 0.01) and a shorter duration of overall vasopressor use in the ICU (12 vs 39 h, median difference = -24 h, 95% confidence interval = -31 to -18; p < 0.01) than those treated with combination vasopressors. No extravasation injury was reported in the study cohort. CONCLUSIONS: Metaraminol is often administered as a first-line peripheral vasopressor in the ICU and is used as a single agent in patients with lower severity of shock.

Vasopressor dose equivalence: A scoping review and suggested formula.

PURPOSE: Calculating equipotent doses between vasopressor agents is necessary in clinical practice and research pertaining to the management of shock. This scoping review summarizes conversion ratios between vasopressors and provides a formula to incorporate into study designs. MATERIALS AND METHODS: Medline, Embase and Web of Science databases were searched from inception to 21st October 2020. Additional papers were obtained through bibliography searches of retrieved articles. Two investigators assessed articles for eligibility. Clinical trials comparing the potency of at least two intravenous vasopressors (norepinephrine, epinephrine, dopamine, phenylephrine, vasopressin, metaraminol or angiotensin II), with regard to an outcome of blood pressure, were selected. RESULTS: Of 16,315 articles, 21 were included for synthesis. The range of conversion ratios equivalent to one unit of norepinephrine were: epinephrine (0.7-1.4), dopamine (75.2-144.4), metaraminol (8.3), phenylephrine (1.1-16.3), vasopressin (0.3-0.4) and angiotensin II (0.07-0.13). The following formula may be considered for the calculation of norepinephrine equivalents (NE) (all in mcg/kg/min, except vasopressin in units/min): NE = norepinephrine + epinephrine + phenylephrine/10 + dopamine/100 + metaraminol/8 + vasopressin*2.5 + angiotensin II*10. CONCLUSION: A summary of equipotent ratios for common vasopressors used in clinical practice has been provided. Our formula may be considered to calculate NE for studies in the intensive care unit.