Brought to you by: Chris Schramm and Maninder Singh
Trauma Rounds:
- Neurogenic shock = distributive shock in patients with spinal cord injuries
- Patients with injuries at T4 or higher at more likely to be affected
- Loss of sympathetic tone to nervous system –> leading to unopposed vagal tone
- Spinal shock = loss of sensation/motor function immediately following spinal cord injury
- Can last hours to several weeks post injury
- When should I suspect neurogenic shock?
- Hypotension
- Bradycardia (not common in other forms of shock)
- In trauma patients, before thinking about neurogenic shock, always rule out hemorrhagic shock first!
- First line vasopressor in neurogenic shock = norepinephrine (alpha and some beta activity so will improve BP and HR)
Pearls and Pitfalls of Emergency Department Mechanical Ventilation (Dr. Aydin):
- Watch Entire Lecture
- Do not use the same vent settings for every patient you intubate!!
- You can cause worsening of the condition in the first hour if you set the ventilator and walk away.
- Physiological changes to the ventilated pt:
- Decreases venous return = decreased preload
- An already dehydrated/hypovolemic pt placed on a vent will tank.
- Increases transmural pressure = gradient that allows blood to flow outward from LV (decreased afterload)
- Increased intrathoracic pressure on capillaries –> can decrease gas exchange
- Decreases venous return = decreased preload
- Ventilator Vocabulary
- PEEP = The pressure at the end of normal expiration
- Analogy: the bit of air already in a balloon that makes it easier to then blow into the balloon.
- Helps w/the next breath by taking over some of the WOB required to inflate alveoli.
- Without PEEP, it’s more difficult to get that initial bit of air into the balloon/alveoli.
- Plateau pressure:
- when the balloon/alveolus is normally inflated, the pressure the alveoli actually see.
- Keep plateau pressure <30.
- Found on the vent by pressing the Inspiratory Hold button.
- Peak airway pressure:
- when the balloon/alveolus is nearly maximally inflated, tense, heading towards popping.
- Keep peak airway pressure <35.
- Airway pressure = the resistance of the system
- Peak Airway Pressure – Plateau pressure
- If elevated, indicates obstruction (biting tube, tube displaced, bronchospasm, mucus plugging)
- Stages of Mechanical Breathing
- Initiation Phase
- Notice pt generating negative deflection (if pt is overbreathing or breathing somewhat on their own).
- Inspiratory Phase = Air flowing in or pt breathing it
- Plateau Phase = When patient breaths in and hold your breath; No flow of air.
- Expiratory Phase
- Initiation Phase
- Stages of breathing, represented as Pressure, Flow and Volume
- Assist Control comes in 2 flavors:
- Volume controlled (VC)-
- eg “I want tidal volume to be 500”.
- This is generally the mode we’ll always be using.
- Pressure controlled (PC)-
- only if pt’s peak pressures are very high and you want to watch them
- But know that volumes will vary.
- Volume controlled (VC)-
- Assist patients to reach their targets
- E.g. a ventilator set on RR 10 and 500 mL is what the pt gets if they’re sedated and not breathing on their own.
- If pt wakes up and takes 5 extra breaths, they will get a total of 15 breaths, all at 500 mL each.
- This assumes the pt is in synchrony w/ the vent and isn’t fighting the vent.
- Tidal Volume
- Set vent TV based on IBW based on height (which correlates w/ lung size).
- Calculator at MDCalc (based on ARDSNET curves)
- Lower TV ventilation helps prevent barotrauma.
- Btw, when bagging a pt, know that the bag contains 1 liter…so we’re probably always over-bagging pts.
- Breath Stacking on a ventilator
- Notice the Flow wave (bottom wave) and how it never returns to the zero line.
- To tx hyperinflation/breath-stacking, either:
- Decrease respiratory rate
- Increasing the proportion of time devoted to expiration.
- OR Increase inspiratory flow rate
- Decreases inspiration time –> leaving more time for expiration.
- More dangerous since it increases the pressure in the chest more quickly
- Decrease respiratory rate
- Permissive hypercapnia = Correct hypoxemia before hypercapnia (except in Neurologic/brain pts or cardiac pts)
- BiLevel Positive Airway Pressure (BiPAP, BPAP)
- Use for COPD
- Ideal for Hypoxemic and hypercapnic pts
- If pt comes in SOB and you don’t yet know if it’s CHF or COPD, it’s ok to use BiPAP first and then switch to CPAP if appropriate
- Continuous Positive Airway Pressure (CPAP)
- Use for CHF
- Decreases preload and afterload, so augments forward cardiac flow
- Great for hypoxic pts because it decreases WOB.
Ultrasound Guided Nerve Blocks (Dr. Shannon):
- Watch Entire Lecture
- Why should you do them?
- No sedation needed
- Generally well-tolerated
- Shortened ED-Stay (decreased opiates/delirium)
- Increased patient satisfaction
- When shouldn’t you do them?
- Active Infection
- Allergy to anesthetic
- Risk for compartment syndrome
- Pre-existing neurologic deficit
- Extreme Obesity
- Anticoagulation
- Uncooperative patient
- Altered mental status
- How much Anesthesia is typically needed?
- Forearm nerve blocks: 3-7 cc each
- Femoral nerve blocks: 20-30cc
- Fascia iliaca blocks: 30-40cc (increased volume, decreased concentration)
- Tibial/“pop” block: 5-10cc
- Technique
- Preparation is key! Make yourself comfortable and set up an ergonomic workspace!
- Pre-scan area of intent
- Sterile technique
- Think of it as two procedures:
- “First procedure:” Enter skin
- “Second procedure:” Start aiming for nerve
- Needle tip orientation: either with bevel facing completely towards or completely away from transducer
- Pitfalls:
- Arterial puncture –> hematoma
- Multiple injections
- Circumferential spread usually not needed in smaller nerves w/o thick epineural tissues
- Injecting directly into nerve –> may contribute to residual paresthesias
- Failing to communicate to patient or consult for expectations regarding block (leading to someone thinking new neuro deficits!)