End-Tidal Carbon Dioxide Monitoring in the Resuscitation of Critically Ill & Injured

Case:

73 yo male with PMH of CAD s/p CABG, hypertension, other medical history unavailable. C/C sudden cardiac witnessed by his wife at approximately 10:55 am. CPR instructions given to his wife over the phone by the 911 operator. Police arrived minutes later to continue CPR with an AED. The BLS team arrived shortly after and assisted with the resuscitation using an AED, BVM, OPA and supplemental oxygen. ALS arrived 14 minutes after the 911; BLS reported 3 AED defibrillations prior to ALS arrival.

Initial ECG is coarse ventricular fibrillation and the patient was defibrillated at 360J by ALS. High-Quality CPR continued. Vascular access established with a right proximal humoral IO, 1mg of epinephrine given and repeated every 4 minutes during CPR. Paramedics intubated the patient without an interruption in chest compressions; initial EtCO₂ is 40 mmHg. 2 minutes later, the patient is noted to be in refractory VFIB despite serial defibrillations and anti-dysrhythmics. A total of 14 defibrillations, amiodarone, magnesium and lidocaine were required to convert the VFIB to an organized pulseless sinus ECG rhythm with a QRS width of 160 msec. The patient also received calcium and sodium bicarbonate. Return of spontaneous circulation (ROSC) was noted 38 minutes into the resuscitation. This patient received approximately 1200 cc of crystalloid IVF, atropine and push dose pressors (1:100k Epi) to maintain hemodynamics during transfer to the ED. Pulses were lost during transport for 8 minutes and required CPR and additional epinephrine. Below is a plot of his EtCO2 and respiratory rate versus time. ROSC#1 @ t=38 minutes and ROSC#2 at t=65 minutes.

Kodali and colleagues recently published an excellent review of the usefulness of capnography in Care of the Critically Ill and Injured. The literature search was quite extensive looking at peer review papers from 1960 to 2014, covering primary research, case reports and other review papers. Figure 2 is a summary of the different clinical applications. Conformation of endotracheal intubation is quoted in Kodali's paper as both 100% sensitive and specific, with 3 decades of data for detecting correct tube placement. This has been known for a while in EM and nice to repeat as often as possible because few tests have that level of certainty. Waveform Capnography is the most definitive evidence of correct endotracheal tube placement, thus eradicating the unrecognized esophageal intubation.

Capnography has been demonstrated to reflect the patient’s cardiac output (CO) during a resuscitation based on the height of the waveform. The greater the CO the more CO₂ is off loaded in the lungs and measured on exhalation. Current Evidence  demonstrate EtCO2 levels less than 10 mmHg during chest compression is not likely to generate ROSC, so every effort should be made to maximize the quality of CPR and treat reversible causes of arrest.

A certain level of prognostication or prediction is also gained by the routine use of capnography during CPR. Abrupt increases in EtCO₂,  generally a jump greater than 10-20 mmHg, is a marker of ROSC, and, conversely, refractory EtCO₂ values less than 10 mmHg has identified 100% of patients who were unsuccessfully resuscitated. Kodali found that the cumulative max EtCO₂ > 20 mmHg at all time points measured between 5 and 10 minutes post-intubation best predicted ROSC (sensitivity of 88%, specificity 77%). EtCO₂ is a valuable tool in real-time decision-making during resuscitation.

Other uses of capnography include monitoring of airway patency and respiratory rates. The waveform capnograph and the ability to set warning alarms will instantly alert providers to apneic conditions, such as obstruction or displacement. In clinical situations where a patient is sedated or obtunded, EtCO₂ will herald hypoventilation or apnea much sooner than traditional SpO₂ monitoring.

Back to our case, after reviewing figure #1, we can apply all the previously mentioned key points to capnography. EtCO₂ definitively confirmed ETT placement. ROSC was predicted at t=10 minutes by an EtCO₂ value greater than 20 mmHg. High-Quality CPR was performed while reversible causes of the arrest were managed. ETT patency was maintained throughout the encounter and transfer to the ED. This would have been a great case to use 720 J Double Sequential Defibrillation (DSD) for refractory ventricular fibrillation.

References:

1.     Goto, Y; etal. “Termination-of-resuscitation rule for emergency department physicians treating out-of-hospital cardiac arrest patients: an observational cohort study”. Critical Care. 2013;17:R235.

2.     Kodali, BS; etal. “Capnography during cardiopulmonary resuscitation: Current evidence and future directions”. J Emerg Trauma Shock. 2014;7(4):332-340.

3.     Meaney, PA; etal. “Cardiopulmonary Resuscitation Quality: Improving Cardiac Resuscitation Outcomes Both Inside and Outside the Hospital. A Consensus Statement From the American Heart Association Endorsed by the American College of Emergency Physicians and the Society of Critical Care Medicine”. Circulation. 2013;128:417-435.

4.     Neumar, RW; etal. “Part 8: Adult Advanced Cardiovascular Life Support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care”. Circulation. 2010;122[suppl 3]:S729–S767.