Critical Care Part 1

What is the primary survey made up of?

Airway

Breathing

Circulation

Inspiratory effort is usually associated with what?

Upper respiratory obstruction

Expiratory effort is usually associated with what?

Lower respiratory tract issues

What can cause a high respiratory rate?

Pain

Stress/fear

Decreased ability to ventilate

What can a decreased respiratory rate indicate?

Brain or cervical disease involving the respiratory centre or increased intracranial pressure

What are the causes of decreased breath sounds?

Air, fluid or herniated viscera

What options are available for oxygen administration?

Flow by, mask, nasal prongs, oxygen hood/tent, oxygen cage or incubator

Why do most patients in shock have an elevated pulse rate?

Because the body will try to maintain blood pressure via the baroreceptor reflex, which increases the heart rate in response to decreased cardiac output

Why do trauma patients in shock have weak and thready pulses?

Due to increased stroke volume and vasoconstriction throughout the body to make blood flow to the vital organs.

Cyanosis indicates that the patient’s haemoglobin saturation is less than what?

75%

What is the difference between paresis and plegia?

Paresis is weakness whereas plegia is an inability to move

What is it important to distinguish a deep pain reflex from?

A withdrawal reflex

What are the levels of consciousness?

Alert

Obtunded

Stuporous - semi-conscious and rousable by a painful stimulus only

Coma

If neurological disease is noted, what neurological features should also be noted?

• Pupil size and symmetry

• Palpebral reflex

• PLR

• Facial assymmetry and head tilt

• Nystagmus

• Presence of gag reflex (in stuporous or comatose patients)

• Anal tone

Define shock

Shock is decreased oxygen delivery, carrying capacity or utilisation by the tissues

Describe hypovolaemic shock

Tissue hypoperfusion occurs secondary to a lack of circulating volume.

List causes of hypovolaemic shock

• Secondary to haemorrhage (internal or external)

• Severe, acute loss into the GI tract (vomiting, diarrhoea), through the kidneys or into a third space eg peritoneal/pleural cavity

Describe distributive or maldistributive shock

This is when the body displays generalised inappropriate vasodilation leading to alteration in distribution of blood flow between the tissues. In the face of normal blood volume, tissue perfusion may be significantly reduced

What causes distributive shock?

Release of inflammatory mediatiors such as in sepsis, SIRS or rarely anaphylaxis

What is cardiogenic shock?

This is a failure of the heart as a pump, and occurs secondary to a number of cardiac diseases including cardiomyopathies, valvular disease and severe arrhythmias.

What is obstructive shock?

This is an obstruction to blood flow through an organ.

List examples of causes of obstructive shock

Pericardial effusion

Splenic torsion

PTE

What is hypoxic shock?

Where there is normal tissue perfusion, but abnormal oxygen content or oxygen unloading

Give examples of hypoxic shock

Hypoxaemia, anaemia, methaemaglobinaemia, carbon monoxide poisoning

What is metabolic shock?

When there is adequate perfusion but inadequate energy levels at the level of the cell. Eg) sepsis when glucose levels drop, heatstroke, cyanide

How does the body attempt to maintain cardiac output and tissue perfusion when the dog’s blood volume reduces?

Increasing heart rate and stroke volume

What are markers of shock in cats and dogs?

• Heart rate and rhythm (in cats, HR tends to go down)

• Pulse quality (including palpation of femoral and metatarsal pulse

• Correlation of pulse and cardiac auscultation (pulse deficits)

• MM colour

• CRT

Blood pressure & lactate

What is the shock index?

A ratio of heart rate to systolic arterial blood pressure. AN SI marker of >1 is a highly sensitive and specific indicator to distinguish dogs not in shock and healthy dogs from dogs with biochemical evidence of moderate to severe shock

What happens to the pulse amplitude in mild vs moderate-severe hypovolaemic shock?

In mild it is increased and in moderate to severe it is decreased

What happens to the pulse duration in mild vs moderate-severe hypovolaemic shock?

It is decreased in all

What is the hallmark of distributive shock?

Inappropriately red mucous membranes as they suggest inappropriate vasodilation and the presence of distributive shock

What other parameter is important to assess when suspicious of shock in a cat?

Temperature (hypothermia)

Heart rate greater than what values are unlikely to represent a physiological sinus tachycardia?

220-240

Pulse quality is a method of assessing pulse pressure which is what?

The difference between systolic and diastolic arterial pressure

Pulses can be bouncy (hyperdynamic pulses) in hypovolaemic patients. These feel big but are easy to what

Compress

How do you treat distributive shock?

• Underlying cause for inflammatory stimulus should be sought

• Fluid therapy

• Blood pressure support with inotropes or vasopressors

What should you be aware can happen in fluids with distributive shock?

Peripheral oedema

What drugs can be used if there is persistent hypotension?

• Dopamine

• Noradrenaline

• Dobutamine

• Vasopressin

• Adrenaline

How does dopamine work?

It is an alpha and beta agonist

How does noradrenaline work?

It is an alpha agonist

Define sepsis

Life-threatening organ dysfunction caused by dysregulated host response to infection

What is septic shock?

Sepsis with circulatory and cellular/metabolic dysfunction and is associated with a higher risk of mortality.

Based on Starling’s equation, what will increase fluid leaving the capillary?

• Increased capillary permeability

• Capillary hydrostatic pressure

• Decreased capillary oncotic pressure

What are the osmotically active particles in the interstitial fluid?

Sodium and chloride

What are the osmotically active particles in the intravascular space?

Sodium, chloride and large proteins (albumin)

What is the most common way of obtaining intra-osseous access in young patients?

Inserting a needle into the medulla of the greater trochanter of the femur, the lateral humeral tuberosity, sternum or iliac crest.

How does dehydration differ from hypovolaemia?

Hypovolaemia is a reduction in intravascular fluid volume whilst dehydration is a loss of pure water, usually over a prolonged period of time when different body compartments have had time to equilibriate in between them. ie) it is a loss of the intravascular, intracellular and interstitial fluid

What are some (non clinical exam marker) resuscitation end points?

Systolic arterial pressure

Mean arterial blood pressure

Lactate

Urine output

What is the resuscitation end point of systolic arterial pressure?

100-120mmHg

What is the resuscitation end point of mean arterial pressure?

80 - 100mmHg

What is the resuscitation end point of lactate?

<2mmol/l in dogs, < 1.4mmol/l in cats

What is the resuscitation end point of urine output?

0.5-1ml/kg/hr

What other markers can be used to judge response to treatment?

Urine output of 1-2ml/kg/hr

A decreasing USG

Normal serum Na K Cl and HCO3

List situations when you would use smaller and incremental boluses?

Any situation where the patient is higher risk for fluid overload

• Cats

• Concurrent chronic heart disease

• Renal failure, esp if oliguria/anuria

• Parenchymal lung disease

• Raised ICP

What are the signs of fluid overload?

Tachypnoea

Nasal discharge

Hypertension

Heart murmur

Third spacing: ascites, pleural effusion

Mentation changes

Hypothermia

What is a fluid challenge and how does it work?

It is a practical and reliable way to diagnose hypovolaemia. If after a bolus of fluid (5-20ml/kg over 20 minutes) there is a positive haemodynamic response (HR decreases, BP stays the same or increases) = patient is hypovolaemic and aggressive fluid therapy should be started

What is the normal blood volume of a dog?

80-90ml/kg

What is the normal blood volume of a cat?

60-70ml/kg

In acute haemorrhage, how much crystalloid should you give if replacing the circulating volume?

A volume of three times the volume lost

In acute haemorrhage, how much blood should be given to replace the circulating volume?

A volume equal to the volume loss

When is it usually sufficient to replace blood loss with crystalloid?

If the patient doesn’t drop to critical levels (PCV <25%) or 25% of blood volume.

When correcting dehydration, fluid therapy should be titrated over what time-scale in cats and dogs?

48h in cats

24h in dogs

What are crystalloid fluids?

Water solutions of salts/electrolytes that pass freely out of the intravascular space

How can you classify crystalloids?

Hypotonic

Isotonic

Hypertonic

How long does it take crystalloid fluids to equilibrate with the extravascular compartments?

1-2 hours.

Why is Hartmann’s considered the most physiological of fluids?

Because the Na, Cl, K, Ca resembles plasma

What does Hartmann’s contain as a bicarbonate precursor and what is this beneficial in?

Lactate

Because it is beneficial in patients with metabolic acidosis (which is common in cases of hypoperfusion)

Why can you use Hartmann’s in hyperkalaemia?

Because it helps reduce hyperkalaemia as exacerbation of an already present acidosis (eg NaCl) can worsen hyperkalaemia.

Why is it contraindicated to give blood products in the same cannula as Hartmann’s?

Because it contains calcium

What does normal saline contain more of than plasma?

Sodium and chloride

What type of solution is 0.9% NaCl?

An acidifying solution.

What is ringers solution?

It resembles normal saline but less Na and more Cl and also contains K+ and Ca+

What are hypertonic solutions more commonly used for?

To rapidly expand plasma volume, increase cardiac output and improve blood pressure

Hypertonic saline has also been shown to increase cardiac contractility and to improve microcirculation by what mechanism?

By decreasing blood viscosity and causing systemic and pulmonary vasodilation

At what rate should you administer hypertonic saline?

5-7ml/kg over 10 minutes for dogs and 3-5ml/kg over 10 minutes for cats

What can rapid administration of hypertonic saline result in?

Hypotension

Bradycardia

Ventricular dysrhythmias

Bronchoconstriction

What other potential side effects are there to hypertonic saline administration?

Hypernatraemia

Hypokalaemia

Haemolysis

Thrombosis

Potential to re-haemorrhage if hypertension occurs after its administration

When would you use hypertonic saline?

In large patients with severe shock

In patients with shock and head trauma

What are the contraindications of hypertonic saline?

Dehydration

CHF

Uncontrolled haemorrhage (particularly pulmonary contusions)

What is fresh frozen plasma?

Plasma derived from centrifugation of whole blood and frozen within 6 hours and is less than 12 months old.

What does fresh frozen plasma contain?

Coagulation factors

Albumin

Alpha 2 macroglobulin

Immunoglobulin

Other proteins

When should FFP be used?

For the provision of coagulation factors in rodenticide intoxication, systemic inflammatory response syndrome or sepsis

What does frozen plasma contain?

Non-labile clotting factors FII, FVII, FIX, FX, FXI, variable amounts of labile clotting facotrs, immunoglobulins, albumin, lipids and electrolytes

Human albumin solution is available as an isotonic or hypertonic solution. What are the pros and cons of its use?

Anti-oxidant and anti-inflammatory properties

It is very expensive and there is a high risk of anaphylaxis (usually to the second infusion)

In patients with capillary leakage, it is likely to leak into the interstitium = administration pointless.

When are blood and blood components indicated?

• Severe acute haemorrhage

• Severe anaemia

• Thrombocytopenia

• Coagulopathies

Dogs rarely have naturally occurring alloantibodies. After a first transfusion, antibodies will be produced in how many days?

4-14d. Therefore in a second transfusion is given more than 4 days after the first one, a cross match should be performed.

What can blood group doesn’t have naturally occurring antibodies?

Type AB cats

What rate should you start a blood transfusion at to check for reactions?

0.5ml/kg/hr (then increased. upto 20ml/kg/hr)

1ml/kg of PRBC will raise the PCV of the recipient by what percentage?

1%

List immunologic transfusion reactions

Agitation

Urticaria

Tachycardia

Tachypnoea

Pyrexia

Anaphylaxis

List non-immunologic transfusion reactions

Hypocalcaemia - due to citrate in the anti-coagulant

Embolism - from clots in the transfusion product

Infection - bacterial and viral (more likely in feline FIV/FeLV/mycoplasma haemfelis)

Haemolysis

Hypervolaemia

Hypothermia

Immunosuppression

What medications should be administered it here is a transfusion reaction?

Anti-histamines (chlorphenamine and ranitidine)

C’steroids

What does cryoprecipitate contain?

High concentrations of VWB factors and factors I, V, VIII, IX and XI

What are acute immunologically mediated transfusion reactions caused by?

Pre-formed antibodies that the patient has against the donor cells.

Animals that have an acute immunologically mediation transfusion reaction will progress to what?

DIC, multi-organ failure and death

What are delayed immunologic transfusion reactions caused by?

A patient developing antibodies to the transfused cells in the subsequent days to the transfusion

What does a delayed immunologic transfusion reaction result in?

Early destruction of the transfusion and haemoglobinuria

Potentially immunosuppression though this is not clear in the veterinary world

Upper airway obstruction or an inspiratory pattern is categorised by what on clinical examination?

Stertor or stridor

With dynamic obstruction = increased inspiratory effort

With fixed obstruction = increased inspiratory and expiratory effort

What are the differential diagnoses for upper airway obstruction?

Polyps in cats

Larygneal paralysis

Pharyngeal or laryngeal masses

Severe URI

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