CPR, Accidents and Emergencies Flashcards
Define respiratory arrest
‘Sudden or complete cessation of respiratory movement’
Define cardiac arrest
‘Sudden and often unexpected stoppage effective heart action’
There may be some electrical activity but it wont be effective at pumping blood round the body.
What is CPA?
Cardiopulmonary arrest when both spontaneous circulation and breathing cease.
What would indicate cardiac arrest?
- no palpable pulse
- no heart sounds
- ECG shows asystole or arrythmia
- Blood intraop stops flowing freely and is thick and dark
- MM colour change and drying of gums
- Prolonged CRT
- No cranial nerve reflexes.
- eye position
Why does respiratory arrest lead to cardiac arrest?
Starts as the brain an heart receive inadequate amounts of oxygen.
Could also be due to co2 accumulation and acidosis
What is the reason for cardiac arrest that has the best resucitation success? Why?
Drug overdose/associated with anaesthesia.
- often correctable
- no delay with placing IV/ETT as already there?
Describe the mechanism of spontaneous ventilation
-Diaphragm contracts, flattening
- Abdominal contents pushed caudally and abdomen moves outwards
- Intercostal muscles contract, pulling the ribs up and out creating negative pressure in the thoracic cavity.
- This causes air to be drawn into the trachea and to the lungs.
- muscles relax and normal positioning of muscles and ribs is restored, gas is exhaled.
What nerve supplies the diaphragm?
Phrenic
What indicated to the brain that a breath needs to be taken?
Chemoreceptors detecting a build up of carbon dioxide in the blood.
Where does the initial signal to start a breath come from
Brain stem
List the 5 groups of respiratory complications that can lead to respiratory arrest
- Ventilatory Drive
- Mechanical ability to breathe
- Obstruction
- Restriction
- Absorption of oxygen
What can affect ventilatory drive under GA?
- Hyperventilation , reduced CO2 reduces drive
- Overzealous IPPV causing hyperventilation
- Drugs affecting sensitivity of chemoreceptors allowing more co2 to build up than normal
- Hypothermia
What can affect the physical ability to breathe
- Interference to the nervous system or respiratory muscles
- cervical spine damage may affect teh phrenic nerve
- muscular or neuromuscular disease may affect the muscles controlling rib movement.
What are the causes of upper respiratory tract obstruction?
- breed disposition (brachys)
- phargeal tissue or tongue relaxation
- head position (increased risk if flexed head)
- Bandaging
- Congestion - can happen is head is positioned lower than body, gravity causes fluid to build up
- Inflammation of airway from trauma
- laryngeal paralysis (nerve controlling opening of glottis is damaged) No active opening of larynx on inspection.
- Tumours, blood clots etc
- ETT obstruction
What is the difference between a stertor and a stridor?
Stertor - a low pitched snore cause by pharyngeal/nasal obstruction.
Stridor - a high-pitched sound more likley to be cause by laryngeal obstruction
What is paradoxial ventilation ?
When there is a blockage stopping air being sucked into the lungs so when the negative pressure builds up the ribcage is sucked in on inspiration and the abdomen moves out.
How can we treat suspected airway obstruction
- pull tongue out
- straighten head and neck position
- Remove the cause if a bandage or FB
- Suction use to clear any liquid secretions
- Intubate or tracheostomy tube.
- drugs to reduce swelling e.g. steroids
- sedative if short sharp stressed breathing (creating a dynamic obstruction as soft tissues are sucked in) to slow respiration. CARE with sedation.
- ## check temp if able as usually hyperthermic
What can cause lower airway obstruction ?
Bronchoconstriction due to to manipulation of airways (bronchoscopy) or disease.
Narrowed lower airways as seen in feline asthma (would see as ‘resistance’ on a capno or feel less compliance when using reservoir bag, less movement of thorax between inspo and expiraion and could affect SPO2)
What would restrict tidal volume in an anaesthetised patient?
- restriction of thorax to expand from equipment or positioning, dilated abdomens, pneumothorax, diaphragmatic rupture.
What physiological effects would hypercapnia have under GA?
A small-mod increase in CO2 causes increased sympathetic stimulation, HR and BP. A large increase in CO2 will cause vasodilation, decreased BP, red MM and deeping anaesthesia due to depression of CNS.
Hypercapnia can increase the risk of cardiac dysrhythmias (VPCs), can alter blod pH and may even lead to seizures/arrest.
What can cause hypoventilation under GA
- Deep anaesthesia (depression of ventilatory centres)
- Drugs (decreased sensitivity centres to CO2 in the brain)
- Physical limitations on expansion of chest or lungs.
What is rebreathing
When there is a significant amount of inhalaed fraction of CO2 (anything over 3mmHg)
What are the formulas for BP and CO
BP = CO x systemic vascular resistance (SVR)
SVR is affected by vasodilation and vasoconstriction
CO = HR x SV
Stroke volume is affected by pre-load, afterload and contractility
What is normal MAP under GA
70-90mmHg
What parameters can we check to identify hypotension?
- BP
- pulse quality
- CRT
- ETCO2 (indicates problem with circualtion)
- Urine output
- Any H+?
What is the circulating blood volume of a dog and cat?
Dog 88mls/kg
Cat 56mls/kg
What compensating may a patient do for hypovoleamia?
vasocontriction and an increase in HR and reading a normal BP because of it.
Describe what crystalloids are and when they would be used?
0.9% saline, Ringers or Hartmanns solution
They are isotonic
Good choice to replace water or electrolytes.
They stay in circulationfor a short period then distribute to the tissues to replace losses.
When would colloids be more applicable to use and why
They contain larger molecules which stay in the circulation for longer so are good for hypovoleamia without dehydration affecting other fluid compartments. E.g. Gelofusin
Name common blood products
Whole Blood
Packed RBCs (PRBCs)
Fresh frozen Plasma (FFP)
Why would you use whole blood over PRBCs?
PRBCs lack the clotted factors in whole blood even though they will help with the oxygen carrying capacity
What percentage blood loss should be replaced by what fluid/product?
10% by crystalloids
10-20% by colloids
and over 20% with blood products
What can affect pre-load volume?
Poor flow of blood in vena cava - compression or occulsion.
What physiological measurements taken under GA would indicate vasodilation?
- Red MMs
- Low diastolic pressure
List the actions of adrenoreceptors alpha 1 & 2 and beta 1&2
alpha 1 - vasocontriction
alpha 2 - central vasodilation and peripheral vasoconstriction
beta 1 - positive inotropy and chronotropy
beta 2 - vasodilation and bronchodilation
What does an inotrope do?
Alters the strength of heart muscle contraction. A negative inotrope weakens the contraction; a positive strenghtens.
What does a chronotrope do?
Changes teh heart rate. Negative decreases and positive increases HR
What does a vasopressor do?
Causes vasoconstriction
When can atropine or glyco be used to treat hypotension?
Only if the hypotension is associated with a low HR
What class of drug are atropine and glyco and how do they work?
Parasympatholytics or Antimuscarinics or Anticholinergics
- block parasympathetic input (vagal input) to the heart (which usually slows the heart rate) at the SA node (pacemaker) and therefore these drugs will increase the HR.
What does ephedrine do?
Causes the release of endogenous stores of catecholamines. It can be used as a vasopressor (vasoconstrictor) and positive inotrope.
What type of drug is dopamine
Positive inotrope and chronotrope and a vasopressor.
Acts on cardiac beta adrenoreceptors to increase cardiac output. Care with lower doses and undesired effects.
What type of drug is dobutamine?
Positive inotrope
Acts on beta adrenoreceptors