Trouble shooting Flashcards
(29 cards)
Causes for hypercapnia
- Hypoventilation
- Increased production of CO2
- Rebreathing of exhaled gases
- Physiologic dead space ventilation
Minute volume =
tidal volume x RR
capnography findings consistent w/ hypoventilation
capnograph shows a slow increase in ETCO2 over time
when can rebreathing of exhaled gases cause hypercapnia?
inspiratory CO2 >2mmHg
causes of airway dead space ventilation?
shallow breathing/small TV
capnography findings consistent w/ airway dead space ventilation
the ETCO2 will be low whilst the PaCO2 builds up as animal not actually ventilating blood-gas exchange regions to remove CO2
possible cause of alveolar dead space ventilation
Pulmonary thromboembolism (ventilated but not perfused lung)
reasons for rebreathing in a non-rebreathing system
- inner limb disconnected at patient site
- fresh gas flow too low
- panting
- XS dead space
reasons for rebreathing expired gases in a rebreathing system
- XS equipment dead space
- unidirectional valves
- exhausted soda lime
Causes of hypoxaemia
- Low FiO2 <30%
- Hypovent: severe OR mild/mod and FiO2 <30%
- Diffusion impairment: thickening of alveolar-capillary wall causes impairment of gas diffusion
- Vent/perfusion mismatch + FiO2 <30%
- Shunt = full lung collapse/atelectasis
causes of diffusion impairment
interstitial/pulmonary oedema
Other: lung fibrosis, carcinomatosis, blood/pus in alveoli
Trouble shooting hypoxaemia
- O2 connected and on
- O2 flow >10ml/kg/min (metabolic requirement)
- FiO2 >30%
- Breathing system connected to common gas outlet
- Patient apnoeic
- Fresh gas cannot reach lung: obstructed ETT? - give manual breath to check patient chest rises
- Atelectasis
- Minimal vent. w/ normal perfusion
causes of atelectasis in GA
- direct compression of alveoli dt GDV, colic, obese, pleural effusion, horse…
- decreased FRC dt muscle relaxation of anaesthetics
timeframe of apnoea to hypoxaemia
hypoxaemia starts w/in 3-4mins of patient apnoea
once SpO2 <95 % –> rapidly life threatening
will rebreathing of expired gases cause hypoxaemia
no - rebreathing of expired gases will occur if fresh gas flow is <200ml/kg/min but since using 100% O2 as carrier gas the O2 content of rebreathed gas is still >90%
causes of minimal ventilation w/ normal perfusion
- interstitial oedema + pulmonary oedema
- pneumonia
- severe bronchoconstriction
actions if patient suddenly wakes up
- Propofol 1mg/kg IV bolus OR
2. Alfaxalone 0.5mg/kg IV bolus
trouble shooting sudden wakening
- Low fresh gas flow?
- Insufficient inhalant?
- Decrease inhalant delivery? ET cuff not inflated?
- No inhalant delivery? Oesophageal intubation?
- Apnoeic patient?
- Sudden stimulus increase
Hypotension investigations
- Depth?
- Hypovolaemic?
- Bradycardic? (Dog <60bpm, Cat <80bpm)
- Ventilation?
- Contractility?
- Vasodilation?
- Lytes? pH?
treatment of hypotension secondary to hypovolaemia
Fluid bolus @ 3ml/kg over 3 minutes
Can repeat 3 times - if responsive
Increase fluid rate to 10ml/kg/hr
Drugs to tx bradycardia
- Atropine
2. Glycopyrrolate
Drugs to treat contractility issues
- Dopamine (low dose)
2. Dobutamine
drugs to treat vasodilation
- Phenylephrine
2. High dose dopamine
mild hypothermia -
38.5-36.5
