• Ask the surgeons to stop. Gently re-inflate top lung and ventilate BOTH lungs with 100% O2*

THEN, to prevent recurrence:

• Deliver O2 to top lung: Low flow O2 catheter or CPAP circuit (see above)
• PEEP to bottom lung
• Propofol infusion
• Clamp the pulmonary artery

PS - *Sometimes the surgeon will be in the middle of something that cannot be stopped to allow re-inflation of the top lung. This is one of the reasons why it’s so important to communicate across the drapes in thoracics.

The trick here is to re-establish safe oxygenation first. Then you can fiddle around to try and prevent further episodes of hypoxia.

Don’t forget the usual system for working out the cause of hypoxia: It’s either the machine, the tube, or the patient. In thoracics it is usually the patient. Never the tube if you use a Robert Shaw, and always the tube if you use a Broncho-Cath

The reason to choose top lung CPAP before bottom lung PEEP is that PEEP on the bottom lung can actually worsen the shunt. PEEP on the bottom lung does 2 things: Increases FRC and raises PVR. The effect on PaO2 is variable and depends on the balance of the two variables. In diseased lung FRC is usually the predominant effect. In healthy lung it’s usually PVR. This is one of the reasons that good pre-op spirometry is a risk factor for hypoxia in one lung ventilation. 5cm CPAP rarely gets in the way of the surgical field.

Propofol does not inhibit hypoxic pulmonary vasoconstriction (HPV), so theoretically there may be some benefit in using propofol. But the evidence for this is not really there. Volatiles only inhibit HPV significantly over 1 MAC.

Thoracics is seriously the best fun to be had in the operating theatre!

Picture: CPAP circuit on top lung with pressure at about 5cmH2O. If you don’t have one of these, just use an airway suction catheter taped to oxygen tubing. You also have to tape over the proximal opening to stop the oxygen leaking out. Don’t pass the tip of the catheter beyond the lumen of the double lumen tube or you risk injuring the trachea/bronchus.

Unless you do a lot of paediatrics, you often don’t think about the dose of blood products by body weight, and they can sometimes be difficult to find.

• Red Cells: 4ml X kg X Hb g/dL rise required. (1 unit/bag ~ 300mL)  
• Fresh frozen plasma: 10 - 20 ml/kg (1 bag ~ 230mL) 
• Cryoprecipitate: 5-10 ml/kg (1 bag ~ 20mL) 
• Platelets: 10ml/kg (1 unit ~ 60mL. 1 pooled bag = 5 units)
• Tranexamic acid: 100mg/kg then 10mg/kg/hr
• Factor 7: 90mcg/kg
• Prothrombin (factor 9) complex: 1mL/kg (25units/kg)

In the exam and even in real life, if you don’t know, then ring someone! (ie: the haemotologist)

PS - To make it easier to remember: FFP, cryo and platelets are all about 10ml/kg.

When you’re in the operating theatre make sure you setup your end of the theatre like a cockpit. If you like, you can draw epaulettes onto your scrubs.

Make sure you can see ALL your equipment from the vantage point of the Chair of Anaesthesia. This includes urine bag, convection warmer, syringe drivers, fluid warmer, everything.

If you can’t see it, then it is bound to stop working and it may take some time for you to realise it. Scan from one side to the other at regular intervals to make sure it’s all functioning.

Label your volume lines with the cannula size. Label your infusion lines with the drug. Label your injection port with the deadspace.

This may all sound a bit over the top, but it’s important in complicated cases, and it can really help you, and the helpers you have called, in a crisis.

Picture: Liver transplant operating theatre. From left to right: Anaesthetic machine, continuous cardiac output monitor with mixed venous saturation, defibrillator, fluid warmer, patient, urine bag, NG bag, fluid management system with cell saver, infusion pumps, TOE.

XRay Guided Pulmonary Artery Catheter Placement

Swan-Ganz catheters can be difficult to float into the pulmonary artery in:

• Low cardiac output states - low forward flow does not push the balloon from the vena cava to the right atrium
• Dilated right hearts - the catheter tends to coil up in the enlarged right atrium

Using X-Ray guidance can help as you can see exactly where the tip of the catheter is, and you can steer accordingly. This can reduce the time to successful catheterisation, as well as reduce the risk of ventricular arrhythmias and knotting of the catheter within the heart. 

This video shows very quick placement of a continuous cardiac output/mixed venous saturation Swan-Ganz into the pulmonary artery of an 80 year old with both a dilated heart, and a low cardiac output state (ejection fraction of 30%). They were being anaesthetised for an aortic valve replacement and coronary artery bypass grafts.

Unless part of a kit, always test whether a guide wire actually passes down the cannula you want to use, as not all cannulas are made equal.

For example a 0.018” wire will pass down a 24G BD Insyte, but it will not pass through a 24G Venflon.

This is weird and annoying as the gauge of the needle refers to to internal diameter, which should be the same across the different brands.

• 100% oxygen
• Hyperventilate to low normal CO2
• Sedate and paralyse to drop metabolic demand
• Keep warm
• Noradrenaline to improve perfusion of right ventricle
• Nitric oxide

PS -The usual starting dose of nitric oxide is dose 20ppm, which is easy to remember as the usual starting dose of PGE1 is 20ng/kg/min. Neonates with pulmonary hypertension are often on both.

Features of a pulmonary hypertensive crisis:

• These are a nerve wracking emergency
• Patient looks terrible. Pale and blue
• High CVP
• PA pressures nearing systemic pressures
• Decreased lung compliance
• Systemic hypotension
• Hypoxia
• Hypercarbia. Note ET CO2 will be low due to reduced pulmonary blood flow. PaCO2 will be high due to reduced elimination via the lungs
• Acidosis: Metabolic and respiratory 

Other things you can do once the patient is a bit more stable:

• Introduce pulmonary vasodilators: sildenafil, bosantan, phenoxybenzamine, prostacyclin
• get a new echo to see if anything is changed or can be improved

Tranfuse blood products with a giving set that has a filter (170 to 230µm). This filters clot and aggregates.

Microaggregate filters (20-40 µm) were used at the bedside in the past to leukodeplete blood products. However, most Australian blood products are now pre-storage leukodepleted. 

• MEND
• Metabolic
• Endocrine
• Neurological
• Drugs

PS - I hate mnemonics. But during the exam, I hated being asked for failure to wake/unconscious differentials even more. It was always a jumble. Categorisation CAN make your life easier in the exam.

Metabolic = Hypoxia, hypercarbia, hyponatraemia, low glucose, hypotension

Endocrine = Hypothyroid, hypoadrenalism, encephalopathic

Neurological = Raised ICP, stroke

Drugs = Anaesthetic, analgesic, paralytic, antcholinergic

(Source: J Golshevsky)

• Blindness
• Hypotension - reduced venous return
• Access to airway
• Pressure sores and peripheral nerve injuries
• Difficulty performing CPR

PS - Incidence of blindness is about 1:1000! Way higher than I ever appreciated. And it’s a devastating complication.

Central retinal artery occlusion occurs with globe compression, which is preventable. Hence, check the eyes!

Ischaemic optic neuropathy is the tricky one. Etiology is unknown, but might have something to do with hypotension, anaemia or venous pressure. Some think it might be the globe ‘hanging’ with gravity by the optic nerve causing a neuropraxia. This last hypothesis actually sounds pretty good to me.

To minimise the risks:

• Avoid prone position in the first place
• Position the patient carefully - head in neutral position, with no flexion, extension or rotation of the neck.
• Make sure the eyes are free. I just tape with a transparent dressing to keep them closed
• Head higher than the heart and no neck ties
• Keep surgery short (95% cases of prone/blindness cases are >6 hours). Stage surgery if possible.
• Avoid blood loss and anaemia, and think twice about induced hypotension

• When using the McGrath video laryngoscope you usually need either a specially-shaped stylette or a bougie.
• To make your own McGrath stylette, bend a maleable aluminium stylette in the same shape as the plastic McGrath blade (see picture).
• When removing the stylette, do it slowly and and advance the tube carefully under vision. The shape of the stylette has a tendency to flick the tube out from the glottis if it is done too fast.
• The same principle applies to the GlideScope.

Some laryngoscope tips, mainly for beginners. 

• Check the light by looking at it. Also check that the light doesn’t switch off when a load is placed on the blade. Worn blades/handles may malfunction in this way.
• Hold the laryngoscope by the handle, not by the corner.
• Pull up and slightly forward to where the ceiling meets the wall.
• The MAC blade is at its thinnest profile when tilted to the right.

Low dose oral naloxone (3mcg/kg QID PO) reduces opioid associated constipation, both in acute pain (opioid infusion/PCA) and chronic pain.

Naloxone works locally on receptors in the gastrointestinal tract. Low bioavailability means that less than 5% acts centrally.

Care needs to be taken to avoid reversing analgesia, especially in patients taking long term, high dose opioids.

Liu M, J Pain Symptom Management 2002,23:48-53.

Simple device for spraying vocal cords. All you need is a bottle of local and a small needle. Make a hole in the bottle with the needle and aim the jet at the cords.

• Difficult airway - swollen/contractures
• Avoid suxamethonium
• IV access and monitoring difficulties
• Hypovolaemia and electrolyte abnormalities
• Pain
• Blood loss
• Temperature loss

PS - Avoid sux in major burns 24 hours after the injury and until fully healed. Major burns: > 10% paed or 20% adult.

What are the requirements for doing a block? ACIMPLE (pronounced a-simple)

• A - Assistance
• C - Consent
• I - IV access
• M - Monitoring
• P - Position
• L - Landmarks
• E - Endpoint

What are the possible complications of doing a block?

• Failure
• Needle related - bleeding, infection, neuropraxia, pneumothorax etc.
• Local related - allergy, toxicity etc.