The Doctor’s Advocate | Fourth Quarter 2012
An Ounce of Prevention
End-Tidal CO2 Challenge in the Obstetric Operating Room
Robin Diamond, JD, RN
The consequences of a human error in misinterpreting monitoring equipment can be devastating. This article outlines straightforward strategies for enhancing safety.
—Robin Diamond, JD, RN; AHA Fellow–Patient Safety Leadership; Chief Patient Safety Officer, Department of Patient Safety
Today’s operating rooms house a multitude of machines and monitors designed for a variety of functions. In a study conducted earlier this year, The Doctors Company reviewed 460 closed anesthesia claims. The study identified potential technical problems and patient monitoring as top patient safety concerns.
For anesthesiologists, the use of end-tidal carbon dioxide (CO2) monitoring is required to observe the effectiveness and stability of ventilation and circulation. The ability to detect and continuously monitor end-tidal CO2 is a requirement for providers of general anesthesia. Sometimes, though, misinterpretation of a monitor’s information may create a problem. The following case illustrates these issues.
The Facts of the Case
The anesthesiologist was called for a 26-year-old female in need of an urgent abdominal delivery. The anesthesiologist’s preoperative assessment noted that the patient had a Mallampati class 3 airway, indicating that only the hard palate and upper uvula were visible on maximal mouth opening. In addition, the patient was an obese half-pack-per-day smoker with a recent upper respiratory infection. The anesthesiologist planned to provide general anesthesia with a rapid sequence intravenous induction and intubation.
The patient was taken to the obstetric operating room (OR). Ten minutes later, preoxygenation was begun for three to four minutes. A colorimetric CO2 device was placed in the facemask breathing circuit and flashed the tan color, indicating that CO2 was present during exhalation.
A rapid sequence intravenous induction of general anesthesia was begun with 200 mg propofol, 200 mg succinylcholine, and cricoid pressure. The vocal cords were visualized, and a size 7.0 mm internal diameter endotracheal tube (ETT) was placed. However, when the end-tidal CO2 color-change device was placed in the breathing circuit at the end of the ETT, there was no visible color change. The anesthesiologist described the positive pressure ventilation as difficult and assumed that the ETT was misplaced.
The anesthesiologist told the obstetrician to proceed with delivering the baby while attempts to improve the maternal airway and ventilation would continue. The neonate was delivered rapidly and achieved Apgar scores of 8 and 9.
The anesthesiologist again attempted to place the ETT using an Eschmann introducer. The Eschmann introducer was placed through the vocal cords, and the ETT was also observed passing through the vocal cords. However, the anesthesiologist was unable to confirm correct ETT placement either by CO2 color change or by auscultation of the chest. Positive pressure ventilation remained difficult. The ETT was removed. Another anesthesiologist arrived to assist, and attempted to place a laryngeal mask airway (LMA); however, LMA placement could not be established.
A general surgeon performed an emergency cricothyrotomy, which was technically difficult due to the patient’s thick neck. Again effective ventilation was not possible, and the CO2 device did not detect any expired CO2.
The patient became bradycardic and progressed to pulseless electrical activity (PEA). Thirty-two minutes after preoxygenation, the patient was given 1 mg each of epinephrine and atropine. Ventilations became easier after these drugs were given, and the CO2 monitor began to flash, indicating some expired CO2. It was at this time the anesthesiologist realized that the entire episode was likely caused by intense bronchospasms, and it was probable that the trachea was correctly intubated initially.
The patient was resuscitated and started on a dopamine drip, a propofol drip (to sedate and prevent seizure activity), and albuterol. Arterial blood gases showed uncorrected mixed metabolic and respiratory acidosis and severe hypoxemia (pH 7.16, PaCO2 55, PaO2 47, HCO3 19.4, BE 9, SaO2 69). The patient was transferred to ICU, where she was examined by multiple consultants and diagnosed with anoxic brain injury. Her condition continued to deteriorate, and she died the next day.
Patient Safety Lessons—The Human Factor
The human factors and error modes in this case should not be overlooked. Why did the obstetrician insist on a general anesthetic? Was the fetus so unstable that only general anesthesia could be considered by the obstetrician and the anesthesiologist? Time was taken for several minutes of preoxygenation. This time could have been used to induce a spinal anesthetic that probably would have been safer for the mother.
The initial decision to perform a rapid sequence induction and intubation was made without apparently considering an awake or flexible fiberoptic intubation. Once the ETT was placed, the anesthesiologist became fixated on the failure of the colorimetric CO2 device to change colors. The anesthesiologist gave too little weight to the conflicting evidence of directly visualizing correct ETT placement. The direct laryngoscopy and the visualization of the vocal cords should have provided assurances of a successful ETT placement.
After the subsequent visualization of the vocal cords for placement of the Eschmann introducer, the anesthesiologist remained anchored to the diagnosis of “incorrect intubation.” The colorimetric CO2 device was giving some correct information—that very little or no air exchange was taking place, so there was no visible color change. The anesthesiologist misinterpreted the lack of color change. A diagnosis “anchoring error” of incorrect ETT placement was made and then not reconsidered until after the patient’s arrest. The limitations and failure modes of the colorimetric CO2 device were not considered.
Even after other doctors arrived to help and the emergency cricothyrotomy was performed, the focus remained on the lack of color change of the colorimetric device. The team was distracted by the monitoring device’s failure to change colors. Only after the patient coded and the resuscitative medications caused the bronchospasm to resolve did the anesthesiologist realize the error.
Patient Safety Lessons—Equipment
One of the issues in this case was the inadequacy of the equipment used in the obstetric OR. Was a flexible fiberoptic laryngoscope readily available in the obstetric OR? It could have been used primarily for an awake intubation if the anesthesiologist thought the intubation was going to be problematic. More importantly in this case, a flexible scope could have been placed through the ETT and would have yielded a view of the carina. This action would have confirmed correct ETT placement after the first or the second ETT placement.
In today’s operating rooms, capnography waveforms and the quantitative display of end-tidal CO2 are common parts of basic monitoring for general anesthesia. Most operating rooms are equipped with monitors that provide a visual waveform and a quantitative digital display. Having this type of monitor would probably have alerted the anesthesiologist in this case to the bronchospasm by displaying the low level of CO2 that was actually being exhaled. Adult colorimetric CO2 devices will not change color below a certain level of CO2. Capnography is much more precise and would have displayed a low end-tidal CO2, probably with the typical pattern bronchospasm produces of delayed emptying, which is a prolonged upslope in the expiratory waveform.
The defense expert noted that the colorimetric end-tidal CO2 device used in this obstetric OR is suitable in emergency or prehospital settings but is no longer considered adequate for monitoring general anesthesia or deep sedation. To maintain consistent standards throughout a healthcare organization, the equipment in an obstetric OR, and in every other proper anesthetizing location, needs to be identical to the anesthesia equipment present in the main operating rooms.
The American Society of Anesthesiologists’ Standards for Basic Anesthetic Monitoring became effective July 1, 2011. A continually viewable quantitative end-tidal CO2 waveform and/or digital readout is currently the de facto standard for anesthetizing locations where general anesthesia is planned or in locations where deep sedation may be produced during sedation procedures.1
There may be extenuating circumstances when these basic monitoring standards might have to be waived by an anesthesiologist. In such cases, the anesthesiologist should state in the patient’s medical record the reasons for waiving any basic monitoring standards.
There are two main patient safety messages to learn from this unfortunate case:
- Do not fixate or “anchor” important treatment decisions based on information from only one source; always consider monitor failure as a possibility.
- Anesthesia and monitoring equipment should be of equal quality and meet current standards in every anesthetizing location.