This study aimed to measure cardiac output, systemic vascular resistance, cardiac index, and systemic vascular resistance index in emergency department patients with poorly controlled hypertension; and to determine the frequency in which antihypertensive drugs prescribed do not address the predominant haemodynamic abnormality. This cross-sectional observational study was conducted in an emergency department of a 1400-bed tertiary hospital in Hong Kong. Patients aged 18 years or above, with systolic blood pressure of ≥160 mm Hg or diastolic blood pressure of ≥100 mm Hg based on two or more measurements and on two separate occasions within 2 to 14 days, were included. Haemodynamic measurements were obtained using a non-invasive Doppler ultrasound monitor. Doctors were blinded to the haemodynamic data. Any antihypertensive medication adjustment was evaluated for correlation with haemodynamic changes. Overall, 164 patients were included. Their mean age was 69.0 years and 97 (59.1%) were females. Systemic vascular resistance and cardiac output were elevated in 65.8% (95% confidence interval, 57.9-72.9%) and 15.8% (10.8-22.5%) of patients, respectively. Systemic vascular resistance index and cardiac index were elevated in 43.9% (95% confidence interval, 36.2-51.8%) and 19.5% (13.9-26.5%) of patients, respectively. Of 71 patients in whom antihypertensive medications were adjusted, 25 (35.2%; 95% confidence interval, 24.5-47.5%) were prescribed agents that did not correlate with the primary haemodynamic abnormality. The profile of haemodynamic changes in emergency department patients with poorly controlled hypertension is characterised. The antihypertensive drugs prescribed did not correspond to the patient's primary haemodynamic derangement in 35% of cases.