Letters to the Editor: Letter to the Editor
To the Editor
We were pleased to read Cardiac Arrest in the Operating Room: Resuscitation and Management for the Anesthesiologist: Part 11 but surprised to not see more mention of using end-tidal carbon dioxide (Etco2) in the operating room, the one place where it should be universally available to help manage cardiac arrests. Although Moitra et al1 acknowledge that difficult airway management is a well-recognized cause of cardiac arrest in the operating room, they do not address undetected esophageal intubation. Normally after intubation, if there is no Etco2 and a flat trace on the capnography, anesthetists would remove the endotracheal tube, reoxygenate the patient with a mask, and try again to intubate the trachea or insert a supraglottic airway device. Unfortunately, there seems to be a fairly common misinterpretation that when cardiac arrest occurs, and before cardiopulmonary resuscitation (CPR) starts, there will almost immediately be a flat capnograph trace similar to esophageal intubation, even when the tube is correctly in the trachea.
This misinterpretation that cardiac arrest immediately produces a flat trace at 0 mm Hg on the capnograph has resulted in failures to recognize esophageal intubations. This was reported in the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society (NAP4).2 There have been several recent patient deaths in the United Kingdom, where this misinterpretation has been a contributing factor in failure to recognize esophageal intubation.3 Consequently, National Health Service Improvement has issued a new “Never Event” on undetected esophageal intubation, defined as “ventilation of a patient following oesophageal intubation instead of the intended tracheal intubation which is not identified because capnography is not used or capnography readings indicating the need for tracheal intubation is not acted upon.”
The correct appearance of the capnograph during cardiac arrest without CPR is poorly covered in textbooks and guidelines. The moment cardiac output ceases, the pulmonary circulation is still full of blood containing high levels of CO2. Provided that ventilation continues, CO2 will diffuse normally, and an Etco2 will be detected on the capnograph, albeit at a low level (maybe 4 mm Hg), for some time. This is not the same as a completely flat 0 capnography trace seen with esophageal intubation. Clinicians must appreciate this difference.
In the description of the features of cardiac arrest, the expression by Moitra et al1 of a “loss of end-tidal CO2” is unhelpful because it suggests a rapid approach to 0, and may lead the anesthetist to not consider esophageal intubation. Perhaps “reduction to a low level of end-tidal CO2” would be a less confusing and more physiological description.
Also, in their Figure 3 algorithm, “Intubation during CPR,” the late mention of capnography to signal the return of spontaneous circulation completely misses the patient safety opportunity to exclude or detect esophageal intubation after endotracheal tube insertion. As the article says, “effective chest compression generates an Etco2 close to or >20 mm Hg.”
Waveform capnography is one of the most useful monitors during cardiac arrest because it can give early indications of problems (eg, reduced cardiac output, hypovolemia, tamponade, etc) and later be used to “capnomanage” the whole resuscitation process.
David K. Whitaker, FRCA
Department of Anaesthesia
Manchester Royal Infirmary
Manchester, United Kingdom
Ellen P. O’Sullivan, FCAI
St James’s Hospital
1. Moitra VK, Einav S, Thies KC, et al. Cardiac arrest in the operating room: resuscitation and management for the anesthesiologist: part 1. Anesth Analg. 2018;126:876–888.
2. Cook TM, Woodall N, Frerk C; Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth. 2011;106:617–631.