EMERGENCY - Management of Shock Flashcards
What is shock?
Shock describes a severe imbalance between oxygen supply and demand within the cells that leads to inadequate cellular energy production which can result in cell death and eventually multisystem organ failure
What are the three phases of shock?
Compensated shock
Decompensated shock
Terminal shock
What is compensated shock?
Compensated shock is the stage where compensatory mechanisms are activated to counteract the decrease in tissue perfusion
What are the two main compensatory mechanisms triggered by the body to counteract shock?
Activation of the sympathetic nervous system
Activation of the renin-angiotensin-aldosterone system (RAAS)
How does the activation of the sympathetic nervous system act as a compensatory mechanism for shock?
Activation of the sympathetic nervous system triggers the release of catecholamines which triggers peripheral vasoconstriction which decreases the intravascular space to optimise volaemia, and directs blood to the critical organs, tachycardia and increased cardiac contractility to increase tissue perfusion and oxygen delivery to the cells
How does the activation of the renin-angiotensin-aldosterone system act as a compensatory mechanism for shock?
Activation of the renin-angiotensin-aldosterone system triggers sodium and water retention increasing fluid retention and thus blood volume. Through a series of mechanisms the renin-angiotensin-aldosterone system also releases angiotensin II which is a potent vasoconstrictor which decreases the intravascular space to optimise volaemia and redirect blood to core organs, which also contributes to increased tissue perfusion and oxygen delivery to the cells
What is decompensated shock?
Decompensated shock is the stage where the body’s compensatory mechanisms are actively failing and are unable maintain adequate tissue perfusion and oxygen delivery to the cells due a decrease in cardiac output resulting in hypotension and overall decreased cardiac function. This also results in hyperlacteraemia as the cells have shifted from aerobic to anaerobic metabolism. The body will continue to release catecholamines however this will be ineffective
What is terminal shock?
Terminal shock is a critical state in which the body has exhausted all compensatory mechansisms and the body’s organs begin to fail due to prolonged inadequate tissue perfusion and oxygen delivery. This results in vasodilation, hypotension, bradycardia, cardiovascular collapse and death
What are the six types of shock?
Hypovolaemic shock
Distributive shock
Cardiogenic shock
Hypoxic shock
Obstructive shock
Metabolic shock
What is hypovolaemic shock?
Hypovolaemic shock is a form of shock caused by a deficit in intravascular volume resulting in tissue hypoperfusion and insufficient oxygen delivery to the cells
What is haemorrhagic shock?
Haemorrhagic shock is a subset of hypovolaemic shock, however, is specifically a deficit in intravascular volume caused by active bleeding and thus a loss of whole blood
What is distributive shock?
Distributive shock is a form of shock caused by a pathological maldistribution of blood flow throughout the body resulting in tissue hypoperfusion and insufficient oxygen delivery to the cells
List three examples of forms of distributive shock
Septic shock
Anaphylactic shock
Neurogenic shock
How does septic shock act as a form of distributive shock?
Septic shock acts as a form of distributive shock by causing sytemic inflammation and vasodilation, causing a pooling of blood in the peripheral tissues
How does anaphylactic shock act as a form of distributive shock?
Anaphylactic shock acts as a form of distributive shock by causing sytemic inflammation and vasodilation, causing a pooling of blood in the peripheral tissues
How does neurogenic shock act as a form of distributive shock?
Neurogenic shock acts as a form of distributive shock due to a sudden loss in sympathetic tone, resulting in vasodilation and pooling of blood in the peripheral tissues
What is cardiogenic shock?
Cardiogenic shock is a type of shock where there is systolic or diastolic dysfunction resulting in decreased cardiac output resulting in tissue hypoperfusion and insufficient oxygen delivery to the cells
What is hypoxic shock?
Hypoxic shock is a type of shock caused by decreased oxygen content within the arterial blood resulting in insufficient oxygen delivery to the cells
List three examples of diseases which can cause hypoxic shock
Anaemia
Severe pulmonary disease
Methaemaglobinaemia
What is obstructive shock?
Obstructive shock is a type of shock caused by an anatomical obstruction of the great vessels or the heart itself resulting in decreased cardiac output and thus tissue hypoperfusion and insufficient oxygen delivery to the tissues
List three examples of diseases which can cause obstructive shock
Cardiac tamponade
Tension pneumothorax
Gastric dilatation volvulus (GDV) resulting in compression of the great vessels
What is metabolic shock?
Metabolic shock is a type of shock causes by the inappropriate use of oxygen by the cells
What is a common cause of metabolic shock in puppies?
Hypoglycaemia - glucose is essential for cells to utilise oxygen and create energy so hypoglycaemia can result in shock
Which five things can be helpful for the diagnosis and monitoring of shock?
Assess clinical signs/pulse parameters
Shock index
Measuring blood lactate levels
Point of care ultrasound
Blood pressure
What is the most important tool for diagnosing shock?
Assessing clinical signs/perfusion parameters
What are the seven key clinical signs/perfusion parameters you need to evaluate while diagnosing and monitoring shock?
Heart rate
Respiratory rate
Mucous membrane colour
Capillary refill time (CRT)
Mentation
Pulses
Extremities
How do the clinical signs/perfusion parameters manifest in patients with compensated shock?
Tachycardia
Normal to tachypnoea
Pink to pale pink mucous membranes
CRT 2 seconds
Mildly obtunded mentation
Fair to good pulse strength
Normal temperature of extremeties
How do the clinical signs/perfusion parameters manifest in patients with decompensated shock?
Tachycardia (bradycardia in cats)
Tachypnoea
Pale pink mucous membranes
Capillary refill time (CRT) - 2-3 seconds
Obtunded mentation
Poor pulse strength
Cool extremities
How do the clinical signs/perfusion parameters manifest in patients with terminal shock?
Tachcardia or bradycardia (bradycardia most likely)
Increased or decreased respiratory rate
White to grey mucous membranes
Capillary refill time (CRT) - over 3 seconds
Stuporous/comatose
Non-palpable pulses
Cold extremities
How do you calculate the shock index?
Shock index = Heart rate ÷ Systolic blood pressure
If the value is more than 1 then the patient is likely in shock
What is an important consideration when using blood lactate levels to help diagnose shock?
Blood lactate levels are a non-specific marker of shock. While lactate levels will typically increase during shock, not all increases in lactate are solely due to shock, which can make this measure unreliable. Therefore, it is essential to also assess the clinical signs alongside measuring blood lactate levels before diagnosing shock
How can blood lactate levels be used to monitor a patient while treating them for shock?
Measuring shock using serial blood lactate measurements throughout treatment can track the patient’s progress and prognosis with an increased lactate clearance indicating a better prognosis
How can point of care ultrasound be used to assist in diagnosing and monitoring shock?
Point of care ultrasound can be useful for estimating a patient’s volaemia (the volume of blood within their circulatory system)
What should you be aware of when using blood pressure to assist in diagnosis and monitoring of shock?
Blood pressure readings can be inaccurate. Therefore, it is essential to also assess the clinical signs alongside measuring the blood pressure
What is the first line treatment method for shock?
Goal directed fluid therapy (also known as fluid challenge)
Which four methods can be used to establish vascular access for goal directed fluid therapy?
Peripheral venous catheterisation
Central venous catheterisation
Venous cut down procedure
Intraosseous catheterisation
What is a venous cut down procedure?
A venous cut down procedure is when an incision is made to expose the vein to allow for direct venous catheterisation
Why is goal directed fluid therapy used as the first line treatment for shock?
Goal directed fluid therapy is used as first line treatment for shock because it helps to restore circulating blood volume and improve tissue perfusion and thus oxygen delivery to the cells
Which route of fluid administration would you want to use to treat a patient in shock and why?
The intravenous route would be the most suitable in patients presenting with shock as the patient requires rapid vascular volume restoration
How do you carry out goal directed fluid therapy when treating shock?
Administer a bolus of intravenous fluid into the patient over 10 to 20 minutes. After the bolus has been administered, reassess the cardiovascular parameters. Repeat the boluses until the patient has reached cardiovascular stability. If you have administered three fluid boluses and the patient’s clinical signs have not improved, then you need to stop and look at an alternative treatment method
How much fluid per bolus should you administer to a dog undergoing goal directed fluid therapy to treat shock?
10 - 20ml/kg IV fluid per bolus over 10 to 20 mins in a dog
How much fluid per bolus should you administer to a cat undergoing goal directed fluid therapy to treat shock?
5 - 10ml/kg IV fluid per bolus over 10 to 20 mins in a cat
Why are isotonic crystalloid solutions often used as the inital resuscitative fluid for treatment of shock?
Isotonic crystalloids are effective replacement fluids as they have a similar osmolarity as plasma and thus when administered these fluids will rapidly redistribute into the intersititial and intracellular compartments leaving about 25% of the delivered volume in the intravascular space to allow for restoration of circulating blood volume. The redistribution of the fluid prevents fluid overload and increase the workload on the cardiovascular system which could potentially exacerbate the shock
How do hypertonic crystalloids treat shock?
Hypertonic crystalloids have a greater osmolarity than plasma and thus after rapid infusion, an osmotic gradient is created that draws water from the intracellular and interstitial space into the intravascular space resulting in a rapid expansion of intravascular volume
What are the indicators for using hypertonic crystalloids to treat shock?
Hypertonic crystalloids present as a good option for patients with traumatic brain injury as hypertonic crystalloids can reduce intracranial pressure (ICP), when rapid intravascular volume expansion is required and they are also anti-inflammatory
What is the dose rate for hypertonic crystalloids for shock treatment in small animals?
2 - 4ml/kg every 10 minutes
What are two of the adverse affects of hypertonic crystalloids?
Hypernatraemia (due to the high sodium concentration of hypertonic crystalloids)
Dehydration (due to the high volume of water drawn from the intracellular and interstitial space into the intravascular space)
Why are hypotonic crystalloids contraindicated in treating patients with shock?
Hypotonic crystalloids have a lower osmolarity than plasma and thus adminstration of hypotonic crystalloids would result in the formation of a osmotic gradient that would draw fluid out of the intravascular space, decreasing the blood volume and exacerbating the state of shock
Why should you be careful to avoid overzealous IV fluid therapy when treating haemorrhagic shock?
Intravenous fluid administration in patients in haemorrhagic shock can increase the risk of fluid overload and exacerbate active bleeding
Why should you be careful to avoid overzealous IV fluid therapy when treating cardiogenic shock?
Overzealous IV fluids administration in patients in cardiogenic shock can cause fluid overload which can worsen congestion and increase the workload on the heart which is already unable to pump effectively
Why would intravenous fluid therapy be contraindicated for hypoxic shock?
Intravenous fluid administration in patients in hypoxic shock could worsen the condition by diluting the concentration of oxygen-carrying erythrocytes in the circulation, leading to further tissue hypoxia
List three other methods that can be used to treat shock
Hypotensive resuscitation
Blood product administration
Drug administration
What is hypotensive resuscutation?
Hypotensive resuscitation is a resuscitation strategy that uses limited fluids and blood products during the early stages of treatment to deliberately allow the patient’s mean arterial pressure (MAP) to remain lower than normal physiological levels.
What mean arterial pressure (MAP) value are you aiming for when carrying out hypotensive resuscitation?
60 - 65mmHg
How can hypotensive resuscitation be useful as a temporary measure while treating haemorrhagic shock?
Hypotensive resuscitation uses limited fluids and blood products during the early stages of treatment which can be beneficial for treating haemorrhagic shock as excessive fluids can exacerbate bleeding
How can hypotensive resuscitation be useful as a temporary measure while treating obstructive shock secondary to gastric dilaltation volvulus (GDV)?
Hypotensive resuscitation uses limited fluids and blood products during the early stages of treatment which can be beneficial for treating obstructive shock secondary to gastric dilaltation volvulus (GDV) as after the GDV is corrected in surgery, the compressed vessels will return to normal and redistribute the blood around the body and potentially cause hypervolaemia
Which blood products can be beneficial to administer to patients in haemorrhagic shock?
Whole blood
Which blood products can be beneficial to administer to patients in hypoxic shock?
Packed red blood cells to replenish oxygen carriers
Which two drug classifications can be beneficial for the treatment of shock?
Vasopressors
Inotropes
How can the administration of vasopressors be beneficial when treating shock?
Vasopressors trigger vasoconstriction which decreases the intravascular space to optimise volaemia and redirects blood flow to core organs
Give an example of a vasopressor
Noradrenaline
How can the administration of inotropes be beneficial when treating shock?
Inotropes increase cardiac contractility which increases cardiac output to increase tissue perfusion and oxygen delivery to the cells
Give two examples of inotropes
Dobutamine
Pimobendan
What are the four possible consequences of shock?
Reperfusion injury
Systemic inflammatory respose syndrome (SIRS)
Multiorgan dysfunction syndrome (MODS)
Dilutional coagulopathy
How can shock cause reperfusion injury?
Shock can result in reperfusion injury as after a period of hypoperfusion the restoration of blood flow to the tissues can trigger an inflammatory response and the production of reactive oxygen species which can cause damage to the tissues
How can shock cause systemic inflammatory respose syndrome (SIRS)?
When there is insufficient oxygen delivery to the cells, the cells will shift from aerobic to anaerobic metabolism resulting in increased lactate and H+ in the blood causing metabolic acidosis. In response to this metabolic acidosis, the body will trigger a systemic inflammatory response as it perceives this acidosis as a threat - resulting in systemic inflammatory respose syndrome (SIRS)
How can shock cause multiorgan dysfunction syndrome (MODS)?
Shock can result in multiorgan dysfunction syndrome (MODS) by causing widespread tissue hypoperfusion leading to cellular damage and dysfunction. This can trigger a cascade of inflammatory responses and oxidative stress causing cell death resulting in multisystem organ dysfunction
What is dilutional coagulopathy?
Dilutional coagulopathy is the dilution of coagulation factors
