Morning Report: 5/2/2013

Here’s Dr. Kong with today’s Morning Report!

 

Intubation of the Asthmatic

 

Summary:

1. Exhaust all pharmacologic and non-invasive breathing therapies

2. The decision to intubate is usually clinical.

3. Remember good pre-intubation prep.

4. Predicted difficult intubation: hard to pre-oxygenate/ poor O2 reserve/ fast desat. because of hyperinflation, airway resistance.

4. RSI with Ketamine (1.5-2mg/ kg) method of choice.

5. Vent settings: chosen to avoid hyperinflation

Volume Assist Control

RR 8-10

Vt: 6-8ml/ kg pbw

PEEP: ≤ 5

I:E 1:4-5

IFR: 60-80 Lpm

FIO2: 100%

Adjust using ABG

6. These vent setting may lead to hypercapnia, that’s usually ok (Permissive Hypercapnia), but sometimes not (head injury, renal or heart disease)

7. Hyperinflation –> incrs risk barotrauma, hypotension, cardioresp arrest

8. Deep sedation/ paralysis + analgesia to avoid breathing asynchrony

9. Remember good post intubation care

 

What is the pathophysiologic problem?

Bronchoconstriction

Airway Inflammation

Mucous Impaction

 

Intubation does not solve these problems directly, and has its own attendant risks in the asthmatic

 

What is the initial management of Severe Asthma Exacerbation?

1. O2

2. Steroids (Prednisone, Dexamethasone,etc.)

3. Adrenergic Agonism (albuterol, terbutaline, epinephrine)

4. Anticholinergics (Ipratropium)

5. Magnesium (smooth mm relaxation)

 

Others:

1. NIPPV (BiPAP) – reduce work of breathing, limited good data, but seems to help

2. Heliox- (helium gas mixture) improved delivery of nebulized agents

 

What are some indications to intubate?

Despite Maximal pharmacologic and non-invasive breathing therapy:

Clinical Indications:

1. Cardiac Arrest

2. Respiratory Arrest

3. AMS

4. Progressive Exhaustion

5. Silent Chest

 

Lab Indications

1. Severe hypoxia w maximal O2 delivery

2. Failure to reverse severe respiratory acidosis despite intensive therapy

3. pH < 7.2, PCO2 > 55-70mm, or PO2 < 60mmHg

 

Wheezing does not correlate with degree of obstruction

O2 Sat can be misleading; does not reflect hypoventilation or breath stacking

 

RSI vs Awake or Partial Awake technique?

1. RSI preferred technique

– Fastest way to take control of airway and breathing mechanics

 

2. Do same prep as for any intubation, if possible:

– Beginning of shift equipment check

– Assess airway

– Pre-oxygenation

– Optimal position

– Back-up plans

 

3.Already predicted difficult intubation: increased difficulty to pre-oxygenate, lower O2 reserve, fast desat because of hyperinflation, increased airway resistance, increased residual volumes, decreased minute ventilation.

 

4. Intubator: should be most experienced person with whatever technique he/she is best at using.

 

5. Giving IVF may be useful for BP support.

 

Which Intubation Meds

Ketamine 1.5-2 mg /kg preferred induction agent

1. promotes bronchodilation 2 ways: directly on lung smooth mm, and by catecholamine surge

2. supports BP 2 ways: catecholamine surge, and is vagolytic

 

Propofol also has brochodilatory effect, but hypotension SE bigger concern in setting of lung hyperinflation and decreased venous return.

 

Succinylcholine vs Rocuronium?

Roc reportedly has same onset as Suc when dosed at 1.2mg/kg, duration of action 45-60min, and low SE profile

May be a good choice, esp since paralysis promotes synchrony with vent

 

What size ET tube should I use?

The biggest one that will fit (reduce airway resistance, improve subsequent pulmonary toilet)

 

What specific complications should I be worried about?

1. Breath stacking –> hyperinflation –>

– Barotrauma (PNX, pnemomediastinum, etc)

– Decrease venous return/ increase pulm art pressure (hypotension, arrest)

2. Correct placement

3. Hypoxia

 

What vent settings should I start with?

Chosen to avoid hyperinflation

Volume Assist Control

RR 8-10

Vt: 6-8ml/ kg pbw

PEEP: ≤ 5

I:E 1:4-5

IFR: 60-80 Lpm

FIO2: 100%

 

Post-intubation Meds?

Goal: Pt comfort, avoid breathing asynchrony

– Midazolam: 0.25-1.0 mcg/kg/min (Sedation)

– Propofol: 5-50 mcg/kg/min (Sedation, careful hypotension!)

– Fentanyl: 50-200 mcg/hr (Analgesia)

 

Role for push dose medications as needed (Ketofol- thanks Dr. Basile)

 

Other Post-intubation Care?

Don’t forget:

1. X-ray to confirm ET tube placement

2. Elevate HOB 30 degrees

3. ABG 15 min after intubation to adjust vent settings

 

Specific vent adjustments in the asthmatic?

1. Hypercapnia may result from above ventilation strategy

2. Hypercapnia is better than Hyperinflation (“Permissive Hypercapnia”)

3. Acceptable levels may be up to pH 7.15 and PaCO2 80mmHg

4. Permissive Hypercapnia should be used cautiously if concomitant head injury/ mass, renal or cardiac disease.

5. AutoPEEP and Plateau Pressure should be followed closely

 

How should I approach Trouble Shooting the Vent?

Start with “DOPES” (Disconnect, Obstruction, PNX, Equipment, Stacking breaths)

 

What about known myopathy associated with steroids and paralytics?

In the ED, major concern is ABC, so although real issue, it is secondary.

With careful vent management, pt can be weened from paralytic in 24-48hr, reducing risk.

 

What about possible histamine release with Fentanyl?

Some studies have shown that this is not the case.

Analgesia is important to reduce breathing asynchrony

 

Resources:

1. Bailey, H. Mechanical Ventilation. Roberts: Clinical Procedures in Emergency Medicine. 5th Ed. Chapter 8. 2009.

2. Hodder, R. Management of Acute Asthma in Adults in the Emergency Department: Assisted Ventilation. CMAJ Feb 23,2010, Vol 182 no.3

3. Lapinsky, S. Intubation in Acute Asthma. CMAJ April 6, 2010 vol. 182 no. 6

4. Meddoff, B. Invasive and Noninvasive Ventilation in Patients With Asthma. Respiratory Care. June 2008 Vol 53 No6

5. Melnick, E. EMPractice Guidelines Update. Current Guidelines For Management of Asthma in The Emergency Department. Feb 2010 Vol 2 No 2

6 . Near-Fatal Asthma. Circulation Nov 28, 2005

7. Parrillo, J. Mechanical Ventilation in Asthma Patients. Critical Care Medicine 2ed Principles of diagnosis and Management. 2002

8. Reid. C. Rocuronium vs Suxamethonium. Resus.me

9. Strayer, R. Awake Intubation. emupdates.com

10. Weingart S. Dominating the Vent: Part I. EMCRIT.org