Critical Care Flashcards
Vasoactive drugs - how can these be used in critical care? Categories?
Agents that act directly on the cardiovascular system are then required to support the circulation
* Inotropes
* Vasopressors
Inotropes
Mechanism of action [3] Side effect
- Act on the heart increasing force and rate of myocardial contraction.
- Tend to increase CO and blood pressure.
- Increase cardiac work and myocardial oxygen demand.
- Increase risk of tachyarrhythmias, which would be undesirable in a heart with already compromised
contractility.
Vasoactive drugs
Vasopressors
Mechanism of action, con
- Act on the circulation causing vasoconstriction.
- Main function is to increase mean arterial pressure (MAP).
- Have the potential to compromise blood flow to limbs and vital organs – the opposite of their
desired effect.
Phosphodiesterase inhibitors
MOA, Uses, examples
- MOA - prevent the inactivation of intracellular cAMP > Phosphorylation of calcium channels permits an increase in calcium influx into the cell permitting increased contractility
- Used in cardiogenic shock
- Amrinone, enoximone, milrinone
Types of shock
- Distributive - loss of vascular tone, sepsis, anaphylaxis, SCI
- Hypovolaemic - loss of circulating volume, major haemorrhage
- Obstructive - blood flow obstructed, massive PE, tamponade
- Cardiogenic -pump failure, anterior MI, mitral valve rupture, CCB overdose
Hypovolaemic shock: spinal shock
Spinal shock results from disordered autonomic activity following spinal cord injury.
In high cord injuries sympathetic supply to the heart and peripheral circulation is lost in the presence of preserved vagal tone, leading to profound veno- and vasodilatation without an ability to mount a tachycardia and preserve CO.
Management of sepsis & septic shock
Fluid management - dangers of too much NaCl, adjunctive therapies
- Large volume infusion of sodium chloride may cause a hyperchloraemic metabolic acidosis and increase the risk of acute kidney injury; the use of balanced fluids such as Hartmann’s may be preferable.
- A modest amount of fluid and a modest amount of noradrenaline are better than very large quantities of either in isolation – the two should be used in conjunction.
- CCS
- Vasopressin
- Dobutamine - for impaired contractility
- Blood transfusion if <70 g/L Hb in absence of acute bleeding, cardiac ischaemic, profound hypoxemia.
Sedatives used in critical care
- Propofol - hypotension
- Midazolam - long half life
- Ketamine - increases sympathomimetic activity, HR & BP
- Etomidate - adrenal suppression
Neuromuscular blockers
Suxamethonium
Rocuronium
Atracurium
Common medical problems in critical care
Critical illness polyneuropathy and myopathy
Definition, risk factor
An acute sensorimotor axonal polyneuropathy and myopathy is associated with critical illness, especially in the setting of sepsis.
Prolonged use of neuromuscular blocking drugs is a major risk factor.
Common medical problems in critical care
Delirium
Haloperidol is commonly used to treat delirium in ICU patients though evidence is lacking to support this approach.
ARDS
- Acute respiratory distress syndrome (ARDS) is a condition characterised by the rapid onset of diffuse bilat- eral alveolar damage
- classified according to the severity of hypoxaemia relative to the FiO2
- key features are disruption of the alveolo-capillary barrier, recruitment of inflammatory cells (especially neutrophils) and surfactant dysfunction.
- Recovery may be characterised by the development of fibrosing alveolitis.
- Management - aggressive treatment of the underlying cause, avoidance of fluid overload and lung-protective ventilation
Management of status asthmaticus
- The inhalational anaesthetic agent isofluorane, which has a bronchodilator action.
- Ketamine or adrenaline infusions, both of which cause bronchodilatation.
- Extracorporeal CO2 removal and/or membrane oxygenation (ECMO) when adequate oxygenation
and/or carbon dioxide clearance cannot be achieved despite maximal therapy and an appropriate mode of mechanical ventilation.
Acute heart failure
- Intra-aortic balloon counterpulsation - anterior MI
- Vasoactive drugs - adrenaline (inotrope), levosimendan (lusitrope)
- Ventricular assist devices - mechanical pumps take over work of driving blood through circulation
- Temporary pacing wire for complete heart block
Indications for haemodialysis in ICU [4]
- Biochemical abnormalities- hyperkalemia, RFTs, hypo/hypernatremia, metabolic acidosis
- Volume overload refractory to diuretics
- Low urine output
- Removal of dialysable toxin
