Dawes: Inotropic Drugs Flashcards
What is an inotrope? what is shock?
An inotrope is a drug that positively or negatively changes the force of contraction.
Shock: This is a state characterised by inadequate organ perfusion to meet the tissues oxygenation demand leading to organ dysfunction.
What are the different categories of shock?
- Hypovolemic
- Haemorrhage and Dehydration
- Cardiogenic
- Heart Failure
- Distributive
- Sepsis and Anaphylaxis
- Obstructive
- Cardiac Tamponade and Pulmonary Embolism.
What are the features of patients in shock?
They will usually be very unwell and as a result in an intensive treatment unit/high dependency unit. As well as this they will present with hypotension, hypovolemia, LV impairment, changes in vascular resistance, poor renal/peripheral perfusion and will be disorientated.
What are the goals of shock resuscitation?
- Restore Blood Pressure
- Ensure euvolemic
- Normalise Systemic Perfusion
- Inotropes and Vasopressors
- Preserve organ function
- Renal Perfusion
- Treat Underlying Cause
- Antibiotics or Relieve Tamponade
You will need to individualise treatment,
What is the mortality rates post cardiogenic shock?
>80% mortality!! In these people we use - intropes and vasopressors and the negative side effects far outweigh the rate of death!
What are the causes of cardiogenic shock? Characterised by?
- Ischaemia
- Valve Dysfunction
- Acute VSD
- High Systemic Resistance - Due to increased sympathetic activity.
- Low Cardiac Output.
What is the first phase of septic shock?
This is the warm/hyperdynamic phase which is characterised by high cardiac output and low peripheral resistance. This is to compensate for the diminished plasma volume.
What is the late stage of septic shock?
This is the cold/hypodynamic phase characterised by subnormal temperature, low white blood cell counts and profound hypotension and hypoperfusion. This is caused by a considerable decrease in the cardiac output.
How do inotropic agents act to treat the effects of shock?
They augment contractility after preload has been established, thus improving cardiac output. This increased cardiac output acts to improve global perfusion. However, it does risk the patient becoming tachycardiac and increases myocardial oxygen consumption.
What are the vasopressors/inotropic agents?
They are alpha- and beta-adrenoreceptors agonists such as norepinephrine, epinephrine, dobutamine and dopamine.
What are the functions of each adrenergic receptor?
What is the function of Beta-1 receptors? EG?
They mainly have effects on the heart
- increase contractility (positive inotrope)
- increase heart rate (positive chronotrope)
Dobutamine
What is the function of alpha-1 receptors? Eg?
These are mainly found in the blood vessels themselves
- increase tone
- increase vascular resistance
Norepinephrine
What is the relationship between vasoconstrictors and inotropes/chronotropes?
Inotropes/Chronotropes effects are mainly generated by the binding of drugs to beta-receptors whereas vasoconstrictors are those drugs that bind to alpha-receptors. As a result, a drugs ability to act as a vasoconstrictor/inotrope/chronotrope is affected by its’ affinity to alpha- or beta-receptors.
What is the relationship between alpha- and beta-receptors and pressure?
Alpha-Receptors act to generate high blood pressures as they function as vasoconstrictors. This is in comparison to Beta-Receptors which result in lower blood pressures being generated.