CICM Second Part Exam Practice SAQs 17052017

As prepared by Chris Nickson, here are the practice written questions from this week’s CICM Second Part exam practice session at The Alfred ICU, with recommended reading from Lifeinthefastlane.com’s Critical Care Compendium and other FOAM sources:

Q1.

A 23-year-old man was the front-seat passenger in a motor vehicle crash. He was intubated for agitation with a GCS 13 in ED and the massive transfusion protocol was activated (total 10 x PRBC, 6 x FFP, 3 x platelets, and 5 x cryoprecipitate). “Pan-scan” CT revealed pelvic fractures with contrast extravasation and he was transferred to the angiography suite. There were other injuries identified on imaging. Following angioembolisation of bleeding pelvic vessels he was admitted to ICU while awaiting external fixation of his pelvis. You review him soon after admission, he is intubated and sedated with HR 120/min and decreasing BP of 85/50 mmHg.

Outline your approach to the initial assessment and management of this case.

Learn more here:

Initial Trauma Assessment

Pelvic Trauma

Shock

Haemostatic resuscitation

Angiography and Embolisation in Pelvic Trauma

Pre-peritoneal packing

Pelvic Arterial Injury

Q2.

Compare and contrast pressure-controlled ventilation with volume-controlled ventilation.

Include relevant flow/pressure/ volume versus time curves in your answer.

Learn more here:

http://www.derangedphysiology.com/main/core-topics-intensive-care/mechanical-ventilation-0/Chapter%203.1.1/control-variables-volume-and-pressure

Q3.

Discuss the issues regarding the timing of renal replacement therapy initiation in a patient with sepsis and acute kidney injury.

Learn more here:

Indications, timing and patient selection for RRT


You can access all the previous practice questions since 2014 here:
https://docs.google.com/document/d/1_Ta8IvVaVtc5Il7-kJwj6qKGu54OmifJGRUWCXud8dY/edit
See this link on INTENSIVE for exam resources:
http://intensiveblog.com/resources/#3

The post CICM Second Part Exam Practice SAQs 17052017 appeared first on INTENSIVE.

Go with the flow

Author: Jonah Powell-Tuck
Reviewers: Aidan Burrell, Chris Nickson

Everything ECMO 011

An obese 49-year-old man is being treated in the ICU for severe bilateral pneumonia. He has been on femoral-femoral VV ECMO for the past 24 hours. The pump blood flow is 5L/min and fresh gas flow is 8L/min. He is ventilated with SIMV PC 15 cmH20 PEEP 15 cmH20 with unchanged tidal volumes of 20ml. His observations are HR 125/min, BP 90/50 mmHg on 0.6mcg/kg/min noradrenaline with oxygen saturations (SpO2) of 82%.

Q1. What initial ECMO circuit checks should be made?

Ensure adequate ECMO circuit oxygenation:

  • Is the oxygen attached and running?
  • Is the ECMO gas flow FiO2 1.0?

Ensure pump flow calibrations are correct:

Ensure there is no recirculation:

  • Are the access and return cannula tips 10cm apart?
  • Is colour difference seen between access and return lines?
  • Is the pre-oxygenator oxygen saturation appropriate?

Ensure the oxygenator is functioning adequately:

  • Check post-oxygenator gases

Pre-oxygenator saturations are 50%. Post oxygenator pO2 is 450mmHg. An echocardiogram is performed revealing a hyperdynamic LV with mildly impaired RV. The estimated cardiac output is 10L/min. The return cannula is seen in the RA with the tip of the access cannula 10cm lower in the IVC.

Q2. Why is the patient still hypoxaemic?

The patient is hypoxaemic as too much of the patient’s deoxygenated blood is shunting past the ECMO circuit, rather than flowing through the ECMO circuit (see Figure 1)

  • The patient’s overall oxygenation results from contributions from both the ECMO circuit and the lungs. If the lungs are having a negligible effect on oxygenation the patient is almost entirely reliant upon the ECMO circuit for gas exchange.
  • 5L of blood per minute is passing through the ECMO circuit and is returned to the circulation fully saturated. However, the patient’s cardiac output is 10L/min, meaning 5L (50%) of blood bypasses the ECMO circuit. The lungs are failing and therefore have impaired ability to oxygenate blood, meaning 50% of cardiac output passes through to systemic circulation with minimal oxygenation.

Figure 1.

Figure 1. Schematic diagram describing the degree of blood oxygenation at different site’s of the patient’s circulation while on VV ECMO.

 

Q3. Increasing the pump speed leads to ‘kicking’ of the access line with no increase in pump flow. What are the options at this stage?

Increasing the pump speed is causing access insufficiency (see Everything ECMO 003). After decreasing the pump speed until the ‘kicking’ resolves, the options include:

  1. Improving the patient’s oxygenation by adjusting mechanical ventilation
    There appears to be little recruitability in this patient and little room to move whilst maintaining lung protective ventilation. More aggressive ventilation is likely to result in worsening ventilator-induced lung injury. Treatment should focus on the patient’s underlying condition. A negative fluid balance should be targeted however access insufficiency and high noradrenaline requirements may limit this. Consideration should be given to nitric oxide therapy, proning and alternative ventilation strategies such as APRV, however, none of these measures are likely to lead to rapid improvements in the patient’s condition.
  2. Reduce the patient’s oxygen demand
    Increasing sedation, paralysing and cooling the patient will help to reduce the patient’s oxygen demand. These interventions may also allow pump flow to be increased. However, they are associated with side effects such as weakness, delirium and increased risk of infection.
  3. Reduce the patient’s cardiac output
    β-blockade could be used to reduce the patient’s cardiac output thereby reducing the proportion of “shunted” non-oxygenated blood reaching the arterial system. However, this may not be advisable in this case as the patient is hypotensive on high dose vasopressors. The role of β -blockers in sepsis is controversial (see the LITFL CCC entry on Catecholamines, Beta-blockade and Critical Illness).
  4. Accept low oxygen saturations
    It is unclear what degree of hypoxia is acceptable in such patients, the ARDSnet trial targeted pO2 55-88mmHg and Sats 88-95%.  Subnormal oxygen saturation targets in ARDS patients is associated with long-term cognitive impairment (see LITFL CCC entry on Oxygen Saturation Targets in Critical Illness). Importantly, a high cardiac output with lower saturations may result in a higher DO2 than a lower cardiac output with improved oxygen saturations.
  5. Increase pump flow and give fluid for access insufficiency
    You are unlikely to achieve the circuit blood flows necessary to overcome the shunt physiology created by the high cardiac output using this approach. Very positive fluid balances lead to further lung injury impairment of gas exchange and they are also associated with higher mortality in severe ARDS (see LITFL CCC entry on De-resuscitation and Positive Fluid Balance)
  6. Switch to a high flow ECMO circuit configuration
    Inserting a second access cannula will allow high pump flows whilst avoiding the problem of access insufficiency. Oxygenation is improved without the need to decrease cardiac output.

Q4. What are indications for high flow ECMO circuit configurations?

Key indications are:

  • VV ECMO with access insufficiency
  • VV ECMO with refractory hypoxia
  • Peripheral VA ECMO with severe differential hypoxia

High flow ECMO configurations

Figure 2. VV ECMO High Flow Configuration (left) and VA ECMO High Flow Configuration (right)

 

Q5. How will switching to a high flow ECMO circuit configuration improve this patient’s oxygenation?

Two access cannulas at two different anatomical sites will allow higher flows to run through the ECMO circuit whilst avoiding the problem of access insufficiency

  • The higher flows will increase the proportion of the blood that is oxygenated via the ECMO circuit thereby reducing the “shunted” portion, consequently improving arterial oxygen saturation

Q6. How is the conversion to a high-flow configuration made?

These are the steps involved:

  • Exclude left internal jugular occlusion on ultrasound
  • Oxygenate the patient with 100% O2 using the ventilator
  • Insert a short “arterial” cannula into right internal jugular (RIJ) vein using aseptic technique
  • Drape and clean the femoral access cannula with iodine-based antiseptic
  • Prime a Y connector attached to long extension tubing with saline and attach the long extension to the RIJ cannula using the ‘underwater seal’ technique
  • Clamp the circuit and the femoral access cannula then remove the access tubing from the femoral cannula
  • Attach the femoral cannula to the short end of the y connector
  • Attach the access tubing to the y connector using the ‘underwater seal’ technique
  • After ensuring there is no air in the circuit remove clamps and re-establish pump flow

Figure 3. Photograph of y connector in high flow circuit. The patient is out of shot on the left and the ECMO circuit is on the right.

 

Q7. Explain the difference in colour between the blood from the IVC access cannula and the SVC access cannula in Figure 3.

The blood from the SVC access cannula appears lighter as the oxygen saturation is greater than the blood entering the IVC access cannula.

  • This is a result of recirculation of oxygenated blood from the return cannula.
  • The relative positions of the three cannulae seen in figure 4 demonstrate how the return cannula may direct oxygenated blood toward the SVC, leading to the SVC cannula having a greater degree of recirculation than the IVC cannula.

Figure 4. Position of Cannulae in High Flow VV ECMO

References and Links

  • Pellegrino V, Murphy D, Hockings L, Roberts L. Extracorporeal Membrane Oxygenation (ECMO). Alfred ICU, 2012

The post Go with the flow appeared first on INTENSIVE.

CICM Second Part Exam Practice SAQs 10052017

As prepared by Chris Nickson, here are the practice written questions from this week’s CICM Second Part exam practice session at The Alfred ICU, with recommended reading from Lifeinthefastlane.com’s Critical Care Compendium and other FOAM sources:

Q1.

  1. List the features which distinguish diabetic ketoacidosis (DKA) from the hyperosmolar hyperglycaemic state (HHS). (40%)
  2. Describe your specific treatment for a 62-year-old female presenting with a decreased conscious state secondary to HHS. (60%)

Learn more here:

CICM SAQ 2014.1 Q17

Diabetic Ketoacidosis

Hyperosmotic Hyperglycaemic Syndrome (HHS)

Q2.

Critically evaluate the role of early mobilisation in intensive care patients.

Learn more here:

Mobilisation in the ICU

Q3.

You are asked to review a 38-year-old woman in the emergency department who has presented with progressive dyspnea over 3 weeks. She arrived from the USA one month ago. She is alert and haemodynamically stable. She has a high anion-gap metabolic acidosis with pH 7.0, urea 50 mmol/L and creatinine 1,500 μmol/L.

Describe your approach to assessment and management over the first 24 hours.

Learn more here:

Acute Kidney Injury

End-Stage Renal Failure


You can access all the previous practice questions since 2014 here:
https://docs.google.com/document/d/1_Ta8IvVaVtc5Il7-kJwj6qKGu54OmifJGRUWCXud8dY/edit
See this link on INTENSIVE for exam resources:
http://intensiveblog.com/resources/#3

The post CICM Second Part Exam Practice SAQs 10052017 appeared first on INTENSIVE.

CICM Second Part Exam Practice SAQs 03052017

As prepared by Chris Nickson, here are the practice written questions from this week’s CICM Second Part exam practice session at The Alfred ICU, with recommended reading from Lifeinthefastlane.com’s Critical Care Compendium and other FOAM sources:

Q1.

You review a 60 year-old man who was involved in a motor vehicle crash. He sustained thoracic trauma and has a flail chest.

  1. Define flail chest and describe the pathophysiology (20%)
  2. Describe the clinical features of flail chest (20%)
  3. Outline your approach to the management of flail chest (60%)

Learn more here:

Thoracic Trauma

Q2.

Discuss endovascular coiling and surgical clipping as treatment options for aneurysmal subarachnoid haemorrhage. (100%)

Learn more here:

Coiling versus Clipping in aneursymal Subarachnoid Haemorrhage

Q3.

You are reviewing a 50-year-old woman in the emergency department who presented with frank haemetemesis and is actively vomiting.

She has a history of chronic liver disease due to Hepatitis C acquired from a blood transfusion 10 years ago and is known to have oesophageal and gastric varices.

She is alert and her vital signs are HR 130/min, BP 90/60 mmHg, SpO2 97% on air, RR 25/min, T 36.5C.

Outline your approach to management in the first 24 hours.

Learn more here:

Gastrointestinal haemorrhage

Intubation in Upper Gastrointestinal Haemorrhage


You can access all the previous practice questions since 2014 here:
https://docs.google.com/document/d/1_Ta8IvVaVtc5Il7-kJwj6qKGu54OmifJGRUWCXud8dY/edit
See this link on INTENSIVE for exam resources:
http://intensiveblog.com/resources/#3

The post CICM Second Part Exam Practice SAQs 03052017 appeared first on INTENSIVE.

Keep calm and cannulate!

Author: Aidan Burrell
Reviewers: Josh Ihle, Chris Nickson

Everything ECMO 010

A 45-year-old lady with ARDS remains hypoxic despite mechanical ventilation, proning, and nitrous oxide. She has a central venous catheter (CVC) in the left femoral vein, and an arterial line in the right femoral artery.

You prepare her for VV ECMO cannulation.

Q1. Describe the equipment you require to perform VV ECMO cannulation.

ECMO cannulas are long, wide, wire reinforced cannulas. The venous cannulas (figure 1) can be single-stage or multi-stage. Single stage cannulas only have holes at the distal tip (figure 1, bottom cannula) whereas multi-stage cannulas have multiple access points along the cannula that are designed to reduce suck down (figure 1, top cannula). They come in a variety of diameters and 19-27 Fr gauges are typically used. Lengths also vary and are chosen to accommodate different configurations – shorter cannula for the neck (15-25cms) and longer cannula (55cm) for the femoral vessels.

Figure 1. Distal tips of venous ECMO cannulas. Single-stage (bottom) and multi-stage (top).

 

Arterial cannulas (figure 2) are shorter, narrower (typically 15-23Fr), and often have a luer lock to connect to the distal perfusion cannula during VA ECMO. The arterial cannula can be also used in VV ECMO for the internal jugular vein. If this is chosen, the luer lock must be carefully closed. This prevents air embolism if used as an access cannula and prevents bleeding if used as a return cannula.

Figure 2. Arterial ECMO cannulas (top two with red caps)

 

Dilators come in a range of brands, such as Biomedicus, Cook and Avalon (figure 3). Different dilators have different characteristics.

Figure 3. Dilators for ECMO cannulation (Biomedicus, Cook, and Avalon, from top to bottom)

 

Wires are very long (1.8m or 2.4m) and have J looped tips. There are soft wires and stiffer wires. The soft wires are safer in terms of minimising vascular injury, however, they are more easily bent by poor cannulation technique (figure 4). The stiff wires (i.e. Amplatz, figure 5) can make dilation much easier but come with a higher risk of inadvertent vascular injury despite having a flexible tip.

Figure 4. Soft wire (in right hand)

Figure 5. Amplatz stiff wire.

Q2. Where will you place the cannulas for VV ECMO? What are the advantages and disadvantages of the commonest two configurations?

 

At the Alfred ICU, a femoral-femoral configuration is usually preferred initially.

Advantages Disadvantages
Femoral – femoral Rapid access

Easier to place and secure

Easier to transport

Potentially less flow
Femoral – internal jugular vein (IJV) Potentially higher flow More recirculation

Securing IJV line is more complex

Q3. Should you re-wire the existing lines?

No (in an ideal world!)

The risk of infection by re-wiring a cannula is high. The venous CVC should be removed and a new clean puncture performed. A new radial arterial line should be placed and the femoral arterial line also removed (arterial line placement can often be delayed until after the ECMO cannulation is completed).

ECMO cannulas have high rates of infection as they are large and often remain in situ for weeks. Thus insertion of new, clean lines using sterile technique is preferred. If an ECMO cannula does become infected it may be difficult to resite them depending on the access points available. Finally, ECMO cannulation requires a nice clean entry point into the vessel – an existing line may enter the vessel via a tortuous route. This may have been OK with a CVC, but will tend to cause problems with the stiffer ECMO dilators and cannulas. There have even been cases of CVCs that have transected an artery during insertion – this can be a catastrophic discovery to make when attempting a ‘rewiring’ for ECMO cannula insertion…

Q4. Your colleague says he has done many CVCs and can cannulate just fine using the landmark technique. What is the role of Ultrasound (US) during cannulation?

Ultrasound is essential for percutaneous cannulation.

Ultrasound:

  1. Increases first pass success
  2. Helps with vessel selection (e.g. left versus right)
  3. Identifies potential problems with the site (e.g DVT, calcification)
  4. Enables sizing of cannulas
  5. Enables confirmation of wire in the vein or artery
  6. Enables insertion in the correct part of a vessel (e.g. avoid bifurcation of the common femoral artery into superficial femoral artery and profunda)
  7. Identifies complications (thrombus, haematoma, pseudo aneurysm)

There is no role for a blind multiple passes technique of cannulation. This leads to delays, haematoma (so-called “porcupine injuries”), and later places the patient at higher risk of infection.

The bleeding risk from multiple failed passes increases once the patient is established on ECMO, and therapeutic heparinisation is commenced. Therefore, ensuring the femoral vessel is punctured on the first attempt, below the inguinal ligament is important. A retroperitoneal haemorrhage can be difficult to diagnosis and often presents very late – the use of ultrasound is important to minimise this risk!

Q5. Describe the key steps that you will take to place the needle into the vessel using the US?

It is important to maximise your first pass success rate to prevent hematoma or vasospasm formation

  1. Under full sterile conditions, identify a straight part of vessel
  2. Find the most superficial part of the vessel (without moving too high or low relative to other anatomical structures, e.g. the inguinal ligament, or vessel bifurcation)
  3. Aim for a flat entry into the vessel where possible (angle approx. 25-30 degrees)
  4. Avoid thrombosed or calcified vessels
  5. Enter the middle of vessel to ensure a clean entry
  6. Once in the vessel, advance the needle within the lumen a few more millimetres under vision to ensure the tip is well within lumen and wire will pass freely – maintain an acute (“flat”) angle to the vessel minimises the risk of inadvertent puncture of the posterior wall (“back-walling”).
  7. Hold the needle steady as you remove the syringe to prevent inadvertent removal of the needle. This is best done with an ‘underhand’ grip on the needle so that your hand rests on the patient and allows you to continuously visualise the needle entry point at the skin.
  8. Feed the wire. Do not advance if there is resistance — stop! When using an Amplatz stiff wire, be very careful as the distal end as it approaches the heart to avoid a penetrating injury.
  9. Confirm the wire course at the femoral vessel by visualising with ultrasound near the point of entry.
  10. Ideally have another ultrasonographer available to confirm the distal end of the wire is advanced to the IVC-RA junction when inserting a venous return cannula at the femoral site.

Q6. You bend the wire on insertion (doh!) – how does this occur and how can you prevent this from happening?

The wire is most commonly bent or ‘kinked’ during dilation, especially when using soft wires and larger French stiff dilators.

Kinking occurs when the dilators are advanced ‘off axis’ in a direction that does not follow the path of the wire (figure 6 – the dotted lines represent the direction of force during dilation). The dilator then moves past the point the wire enters the vessel and kinks the wire. In figure 7, the dilator was advanced in the incorrect direction, at a different angle to the original needle cannulation, and then the wire became twisted like a corkscrew during the sequential dilation and rotation process.

Figure 6. Mechanism of wire kinking during dilatation

 

Figure 7. Yikes!

 

To help prevent this, the cannulator should be conscious of the trajectory of the needle and wire during insertion. Ensure dilators are advanced along the same path during subsequent dilatation.

Q7. The left femoral vein is 12mm. The right is 9mm. What size cannulas will you use?

The cannula size that fits inside a vessel can be estimated using this formula:

Vessel mm x3 = French gauge of cannula

In practice, other factors come into play as well:

  1. Size of the patient
  2. VA vs VV ECMO
    — in general, VA ECMO requires lower blood flows, while sick VV ECMO patients with high cardiac outputs often require very high ECMO blood flows and bigger cannulas
  3. Site of cannulation
  4. Access vs return
    — As most problems occur on the access side, such as access insufficiency, a large cannula is important, although a small return cannula diameter will also increase resistance on the circuit and reduce ECMO blood flow.

As a general rule of thumb, try to use as large cannulas as possible that can be safely and quickly inserted. In this patient, a 25Fr multistage access cannula and a 19 Fr return cannula were used.

Q8. Describe the dilation technique you will perform to insert the cannulas?

Dilation can be done with one or two person techniques, and is influenced by time and staff availability, and whether or not you are using stiff wires.

The key principle is to sequentially dilate up the skin and tissues without causing tissue trauma. It is important to push the dilator along the direction of the wire (see question 6). Push the dilator in straight until there is resistance and then twist in one direction whilst maintaining forward pressure and torque, which will apply tension on the subcutaneous connective tissue fibres. When you withdraw the dilator, this loosens or tears the underlying connective tissue fibres making the next pass a little easier. Repeat the process, each time advancing the dilator further before twisting. Several ‘advance and twist’ attempts may be required with each dilator, be patient!

“It is like medical school, you go in straight and come out twisted!”
— Vin Pellegrino on sequential dilation for ECMO cannulation

If using a two person technique, the second person can jiggle (or “rack”) the wire in and out of the dilator to feel for “play” (free movement) and “hold up” (resistance to free movement). “Hold up” is the earliest signal that the wire is being bent or kinked when the dilator is moving NOT in line with the wire. If the second person feels any increase in resistance when jiggling the wire the cannulator must stop dilating and adjust the angle of dilator until the wire freely passes through the dilator again.

Q9. You are having difficulty passing the cannulas through the right skin. Do you cut the skin?

No (in an ideal world!)

This varies between centres – some do not cut the skin at all, while others routinely perform open incisions (particularly when done by surgical teams). In our centre’s experience is that meticulous sequential dilation usually allows the skin to stretch to accommodate the

Our centre’s experience is that meticulous sequential dilation usually allows the skin to stretch to accommodate the cannulas, while keeping a tight fit to prevent bleeding and haematoma formation. It is also often faster. The advantage of the open cannulation technique is it can give excellent visualisation and confirmation of the vessels and may decrease vessel wall damage.

Q10. Describe how you will advance the cannula into the patient.

Even after dilation, the lip between the obturator and cannula can get caught at the skin or at the point where the cannula enters the vessel. Twisting (rotating) the cannula upon reaching these points often helps the cannula pass more smoothly.

The cannula should be advanced until all the side holes are beneath the skin and within the vessel. At this point the obturator within the cannula is pulled back to the specified marking before advancing the cannula any further. This is important so that the leading tip of the cannula is the soft plastic at the end of the cannula, not the firm, sharp obturator which can lead to serious or fatal perforations of the right atrium.

The obturator does not need to be pulled back when advancing the shorter arterial cannula at the femoral site for VA ECMO.

Q11. You observe that during femoral-femoral cannulation, both cannulas are in the IVC. Describe how will you position them for VV ECMO?

The IVC is almost always able to accommodate both the access and return cannulas. The access cannula needs to be in more proximal IVC (ie closer to the skin), while the return needs to be distal – usually in the right atrium. In general, a separation of ≥10cm between the distal holes of the access and the return cannulas is needed to prevent recirculation.

We use ultrasound to guide their positioning, usually via a transthoracic subcostal view of the IVC, or a bicaval view during transoesophageal echocardiography (TOE).

Other methods include using an imaging intensifier in radiology or the cath lab, or by measuring the cannula depth at the skin (followed usually by an abdominal or chest X-ray).

Note the last 4cm of the Biomedius single stage cannula tip is plastic – this cannot be seen on X-ray and may appear much lower than it really is. This plastic tip can only be seen with good quality US imaging (e.g. TOE).

Q12. What is the role of the Avalon cannula? What are the pros and cons in this case?

The Avalon cannula combines both access and return cannulas into a single cannula. They are usually larger cannulas (up to 31 Fr), and are typically sited via the internal jugular vein in the neck.

Advantages include the need for only a single puncture and they may be better tolerated enabling mobilisation and rehabilitation.

Disadvantages are that they can be more challenging to position correctly and blood flows may be lower than other dual cannula techniques. Careful positioning is paramount as the returning jet of blood must be directed through the tricuspid valve. Any malposition will lead to recirculation.

Figure 8. Avalon ECMO cannula. From: Lazar DA, et al. (2012) Journal of Pediatric Surgery 47(2):430-4 (Click image for source)

 

References and Links

  • Pellegrino V, Ihle J, Hilton A, Murphy D. Guideline for Cannulation for Peripheral ECMO. Alfred ICU, 2012

If you want to learn ECMO cannulation come to the Alfred ICU ECMO Cannulation course. It is held twice yearly — details are available at the Alfred ICU Courses website.

The post Keep calm and cannulate! appeared first on INTENSIVE.