a. Event A: Option 5 ** of adrenaline infusion. This corresponds to a ** of increased heart rate and widening of the pulse pressure with a fall in diastolic pressure, whereas at the second event heart rate decreased and both systolic and diastolic pressure increased, indicating that noradrenaline was infused during ** B.
b. Trace C: Option 2 Heart rate. Adrenaline accelerates the heart but noradrenaline causes reflex slowing produced by the steep rise in mean arterial pressure. This is the only scale giving an initial value (around 80) corresponding to a normal (slightly apprehensive) heart rate.
c. Trace D: Option 1 Arterial pressure. Adrenaline lowers the diastolic pressure but noradrenaline raises it. This is the only dual trace corresponding to systolic and diastolic pressures; the initial value 130/80 corresponds to normal blood pressure.
d. Trace E: Option 3 Cardiac output. Adrenaline raises cardiac output but noradrenaline reduces it because of the reflex depression of cardiac activity. Again the scale corresponds to an initially normal/slightly raised cardiac output around 6–7 litres/minute.
e. Trace F: Option 4 Peripheral resistance. Noradrenaline raises total peripheral resistance because of its predominant effect on alpha adrenoceptors which mediate vasoconstriction; adrenaline lowers it because of its predominant effect on beta adrenergic receptors which mediate vasodilation. These units are appropriate for peripheral resistance: from the equation
Mean arterial pressure = Cardiac output x Peripheral resistance we can derive that
Peripheral resistance = Mean arterial pressure/Cardiac output
For the initial state this equals approximately 100/7 = 14–15 as in F (the units are mmHg/litre/minute).
Note that for this question it was necessary to consider all aspects of the diagram together, rather than consecutively.
