Inotropes for the management of septic shock have been explored in various ways, be they for septic cardiomyopathy or to massage the sluggish microcirculation. The college have asked about them in Question 7 from the first paper of 2005, where the candidates were invited to compare adrenaline, dopamine and dobutamine. The canonical sources for answering such a question in the modern era might include the following:
It is another one of those answers which works very well as a table.
Observe:
Features |
Dopamine |
Dobutamine |
Adrenaline |
Class |
Endogenous catecholamine |
Synthetic catecholamine |
Endogenous catecholamine |
Pharmacokinetics |
Half-life 2-3minutes |
Half-life 2-3minutes |
Half-life 2-3minutes |
Receptor activity |
Predominantly beta-1 agonist activity; |
Predominantly beta-1 receptor agonist at low doses, with more alpha-effects as dose escalates |
Mixed non-selective alpha and beta agonist |
Mechanism |
Increases intracellular IP3, which in turn increases the availablility of intracellualr calcium to smooth muscle contractile proteins |
Increases intracellular cAMp, thus increasing the amount of intracellular calcium available for contractile elements. |
Increases intracellular IP3, which in turn increases the availablility of intracellualr calcium to smooth muscle contractile proteins. Additionally, the beta-effects increase intracellular cAMp, thus increasing the amount of intracellular calcium available for contractile elements. |
Benefits in sepsis |
Maintenance of vascular smooth muscle tone to maintain normotension |
Maintenance of vascular smooth muscle tone to maintain normotension Increase cardiac contractility, thus increasing tissue perfusion |
Maintenance of vascular smooth muscle tone to maintain normotension Increase cardiac contractility, thus increasing tissue perfusion |
Adverse effects |
Peripheral vasoconstriction may worsen the microcirculatory shunting of sepsis |
Arrhythmogenic at the high doses required for treatment of severe sepsis Increased cardiac oxygen demand due to increased contractility and heart rate may cause ischaemic phenomena No evidence for any renal protective effects |
The beta-2 vasodilatory effect may result in a decrease of blood pressure, which would be counterproductive in sepsis. Increased cardiac oxygen demand due to increased contractility and heart rate may cause ischaemic phenomena Peripheral vasoconstriction may worsen the microcirculatory shunting of sepsis Lactic acidosis develops due to beta-2 and beta-3 effects |
That is probably enough to answer Question 7 from the first paper of 2005. As usual, unnecessary detail is available below:
The CICM examiners often look for a finishing statement to their "critically evaluate" questions, which might start with something like "In my practice, I would...". In order for the reader to generate a confident-sounding "own practice" statement, a model is offered below.
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Zhang, Zhongheng, and Kun Chen. "Vasoactive agents for the treatment of sepsis." Annals of Translational Medicine (2016).
Morelli, Andrea, et al. "Levosimendan for resuscitating the microcirculation in patients with septic shock: a randomized controlled study." Critical care 14.6 (2010): 1.
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Mavrothalassitis, Orestes Y., et al. "Impact of Vasodilator Administration on Survival in Patients with Sepsis: A Systematic Review and Meta-Analysis." Annals of the American Thoracic Society ja (2023).