Presentation on theme: "Dr Bronwyn Avard, July 2010 To understand the basic physiology of shock To understand the pharmacodynamics and pharmacokinetics of vasoactive drugs."— Presentation transcript:
Dr Bronwyn Avard, July 2010
To understand the basic physiology of shock To understand the pharmacodynamics and pharmacokinetics of vasoactive drugs used in ICU To know the indications for the administration of different inotropes and vasopressors in the critically ill patient To know the complications of administering these vasoactive drugs, and relevant patient care issues
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Cardiac output = stroke volume x heart rate amount of blood ejected from the ventricle in systole depends on : - preload - afterload - contractility
Cardiac output = stroke volume x heart rate › Preload = end-diastolic ventricular volume › Afterload = resistance against which ventricle contracting › Contractility = strength of muscle activity Cardiac index = cardiac output / BSA
Oxygen delivery = cardiac output x arterial oxygen content stroke volume x heart rate preload afterload contractility [haemoglobin] x SaO 2
Vasoconstriction caused by higher dose noradrenaline redistributes blood flow to essential organs Even though MAP rises, splanchnic perfusion falls & rising lactate can indicate gut ischaemia
Acts on both beta 1 and 2 receptors Net effects are › Increased contractility › Increased heart rate › Mild vasodilation Effect on MAP variable and not always predictable – may increase or decrease
76 year old woman post NSTEMI HR 84bpm MAP 64mmHg Cool peripherally Begun on dobutamine 7.5mcg/kg/minute MAP falls to 60mmHg WHAT WOULD YOU DO?
She was probably vasoconstricted prior to infusion. Beginning dobutamine caused vasodilatation hence MAP fell. Fluid bolus or noradrenaline would be appropriate.
mcg/kg/min = rate (mL/h) x concentration (mcg/mL) weight (kg) x 60
mcg/kg/min = rate (mL/h) x concentration (mcg/mL) Weight (kg) x 60 You are caring for a 60 year old man, weighing approximately 90kg, admitted after a non-ST elevation myocardial infarction. He is receiving adrenaline at 5mL/h. The 100mL bag has 8mg adrenaline in it. What dose of adrenaline is he receiving ? (in mcg/kg/min)
ANSWER : 0.07 mcg/kg/min
mcg/kg/min = rate (mL/h) x concentration (mcg/mL) weight (kg) x 60 mcg/min = concentration (mg/mL) x 1000 x rate (ml/h) 60
mcg/min = concentration (mg/mL) x 1000 x rate (mL/h) 60 You are looking after a 25 year old woman who has been admitted with sepsis. She has 6mg noradrenaline in 100mL bag of normal saline, which is running at 5mL/hour. How many mcg/minute is she receiving?
ANSWER : 5mcg/min This is why we use the concentration of 6mg/100mL as the “mL/h” equals “mcg/min” (she was on 5mL/h noradrenaline)