The Physiologically Difficult Airway: Severe Metabolic Acidosis
Our conference reviewed the literature surrounding risk factors for cardiac arrest during intubation in both pediatric and adult patients, and discussed optimization of a pediatric patient requiring intubation who has a severe metabolic acidosis.
Why is this important?
- Rate of peri-intubation cardiac arrest during emergency tracheal intubation is 1.0-4.2% in adults and 0.8-1.7% in children
- Based on limited literature, factors associated with peri-intubation arrest in adults are hypoxemia, hypotension, and multiple attempts. In children, limited literature has found hypotension, cardiac disease, and hypoxemia as risk factors.
Key Points: Before the Attempt
THERE IS ALMOST ALWAYS TIME TO OPTIMIZE
The patient is high risk for deterioration from intubation due to the severe metabolic acidosis. The apneic time during intubation will worsen their acidosis by driving up their CO2, which can push them over the edge to cardiac arrest. Take what time you have to optimize your attempt.
LET YOUR DIFFERENTIAL GUIDE YOUR OPTIMIZATION
Ask yourself: Why is the patient so acidotic? Using your differential can help guide you on how to best address optimization.
THE GOLDILOCKS FLUIDS
Assess volume status and resuscitate until you feel you have maximized their preload. Unfortunately, knowing when you have maximized preload is difficult… certainly monitoring for signs of volume overload is important, but striking that balance is hard. Type of fluid to use? Theoretical though not strong evidence, to suggest that reaching for LR over NS to prevent worsening acidosis, but unclear here how significant this acidosis may or may not be.
PROBE TO THE CHEST
Complete a bedside cardiac POCUS to evaluate for function and a gross evaluation of possible myocarditis. Keep in mind that performing an ultrasound on a very tachycardic infant has its challenges.
USE YOUR MEDS WISELY
Check your electrolytes, and replete as needed (especially calcium). Though there is a lack of evidence, giving a dose of bicarbonate to attempt to buffer the pH is reasonable. Have a code dose of Epinephrine ready, but also consider maximizing the patient’s preload and contractility with a vasopressor infusion prior to intubation.
ARRHYTHMIAS CAUSE SHOCK TOO
Consider grabbing an EKG if there is an elevated HR, especially if it is noted to have minimal variability. An EKG to evaluate for SVT is important, as sustained SVT in an infant can cause them to present in uncompensated shock– which may look very similar to sepsis.
OPTIMIZE YOUR BVM
It is important to have clear communication with head of bed regarding bagging techniques including rate, pressure and i-time. Consider the patient’s underlying pathophysiology and degree of compensation needed. Use their current ability to compensate (if any) as a guide.
ETCO2: NOT JUST FOR SEDATIONS ANYMORE
EtCO2 can be used as a proxy measure of cardiac output and pulmonary perfusion. With a good mask seal and EtCO2 in line, watching the capnograph for a good waveform and appropriate CO2 values is another piece of information you can use to try and gauge your resuscitation. With the cardiac output improving, we should expect the ETCO2 to go up from its baseline as the perfusion the lungs increases. However, there are difficulties with EtCO2 in infants, including poor mask seal and increased RR which would influence the reliability of measurement. Pay close attention to the waveform to assess the quality of the number. If you have a blood gas to compare with the pCO2, even better.
Key Points: During the Attempt
OBVIOUSLY “_SI” IS THE BEST “SI” TO USE
To RSI or not to RSI?
Using RSI will increase the likelihood of first-pass success. Other literature supports the use of sedative only to keep the patient’s own high minute ventilation during intubation and avoid apnea time. Whatever approach is decided needs to be clearly communicated to the head of the bed/RT present!
Either way, the most experienced/most likely to succeed provider should perform this intubation to maximize first attempt success.
Key Points: After the Attempt
YOU’RE NOT DONE AFTER THE TUBE IS IN!
Don’t forget the ventilator and vasopressors for these patients in particular. It is very important to discuss the ventilator management with the RT. Remembering the significance of these patient’s high minute ventilation rate and avoiding hypoventilation that would worsen acidosis is important. A pressure support or pressure control mode may be best to allow the patient to maintain their own minute ventilation and volume received. Obtaining a new VBG soon after intubation can help guide your ventilator settings. Utilize your ICU for support. With the switch from negative to positive pressure ventilation, watch for hypotension and be ready to quickly intervene with fluids and vasopressor support.
References
Shiima Y, Berg RA, Bogner HR, et al. Cardiac Arrests Associated With Tracheal Intubations in PICUs: A Multicenter Cohort Study. Crit Care Med 2016;44:1675-82.
Gradidge EA, Bakar A, Tellez D, et al. Safety of tracheal intubation in the presence of cardiac disease in paediatric ICUs. Cardiol Young 2018;28:928-37.
Mort TC. The incidence and risk factors for cardiac arrest during emergency tracheal intubation: a justification for incorporating the ASA Guidelines in the remote location. J Clin Anesth 2004;16:508-16.
Heffner AC, Swords DS, Neale MN, Jones AE. Incidence and factors associated with cardiac arrest complicating emergency airway management. Resuscitation 2013;84:1500-4.
De Jong A, Rolle A, Molinari N, et al. Cardiac Arrest and Mortality Related to Intubation Procedure in Critically Ill Adult Patients: A Multicenter Cohort Study. Crit Care Med 2018;46:532-9
Mosier, J. M., Joshi, R., Hypes, C., Pacheco, G., Valenzuela, T., & Sakles, J. C. (2015). The physiologically difficult airway. Western Journal of Emergency Medicine 2015;16(7):1109.
