Sun14November1246PM 30

A 74-year-old man is admitted to the Intensive care unit following an emergency laparotomy for faecal peritonitis.

He is intubated, sedated and ventilated. His vital signs are: temperature 37.8°C, pulse rate 110 beats per minute, BP 130/90 mmHg, Central venous pressure 15 mmHg and urine output 20 ml/hr.

Which one of the following drug infusion regimens is most likely to improve hepatosplanchnic and renal blood flow?

(Please select 1 option)

Dopamine 15 mcg/kg/minute Incorrect answer selected

Noradrenaline 0.5 mcg/kg/minute

Dopexamine 1 mcg/kg/minute This is the correct answer

Adrenaline 0.05 mcg/kg/minute

Isoprenaline 2 mcg/kg/minute

Explanation

Dopexamine hydrochloride is a synthetic catecholamine and is a structural analogue of dopamine. It has marked intrinsic activity at the beta-2 adrenoreceptor and to a lesser extent dopaminergic - 1 (DA1) and dopaminergic- 2 receptors. It has no alpha-1 adrenoreceptor activity. DA1 and DA2 receptors are present in the smooth muscle of the mesenteric and renal vasculature. Stimulation of these receptors increases vasodilatation and improved blood flow.

Both dopamine and dopexamine have been used to improve urine output (increasing renal blood flow, glomerular filtration and causing a natriuresis) and splanchnic blood flow.

However, low dose infusions of these drugs have not shown to reduce the incidence of renal failure and mortality in high risk patients. Dopexamine will also increase cardiac output and blood flow via beta-1 agonist activity.

Dopamine at an infusion rate of 15 mcg/kg/minute will exert beta-1 and alpha-1 effects and negligible DA1 activity.

Adrenaline and noradrenaline both have beta-1, beta-2 and alpha-1 activity but no dopaminergic activity.

Isoprenaline has beta activity only.

The use of vasopressors may have a detrimental effect on hepatosplanchnic and renal blood flow (vasoconstriction) and at best in fluid resuscitated no significant effects. The addition of a dopamine agonist will improve flow.

Reference:

Gopal S, et al. Meta-analysis on the effect of dopexamine on in-hospital mortality. Anaesthesia. 2009;64:589-94.

Answer Statistics

1

40%

2

21%

3

32%

4

5%

5

4%

Times answered: 276