I participated in volunteer plastic surgery missions to 5 continents over my 40 year career,. The incidence of anesthetic mortality during volunteer medical missions overseas is about 20 times higher than United States statistics. Volunteer anesthesia mishaps fall into several major categories:
- Inhalational anesthetic mishaps, some involving Halothane
- Airway disasters
- Patient issues
- Unfamiliar equipment
- Communication issues
In this series of blog articles I will discuss each of these categories, starting with inhalational anesthesia mishaps using the older agents such as Halothane (Fluothane). Cases described are a sampling of mishaps that I witnessed or heard of from other volunteers.
Most anesthesia providers from advanced countries are unfamiliar with the anesthetic agent Halothane. Halothane is a safe anesthetic. It has provided, and still provides, anesthesia for millions. However, Halothane has significant side effects not present in the newer agents. Lack of familiarity with these side effects can get your patient into trouble.
Lack of Training in Halothane Use
Halothane is no longer available in the United States. However, poorer countries around the world still use Halothane. It’s easy to acquire and it’s much less expensive than the more recent agents Sevoforane or Desflurane. Halothane is on the World Health Organization’s List of Essential Medications. If you do volunteer anesthesia, you will eventually use Halothane.
I used Halothane almost exclusively early in my career. As other agents were added, Halothane was still common in pediatric anesthesia until the 1990s. Its lack of airway irritation and potent bronchodilation made it a good choice for pediatric inhalational inductions. Newer agents such as Sevoforane, with a better side effect profile, replaced halothane use in developed countries. As a result, U.S. anesthesia students today have never used halothane.
An 18-month-old child underwent a cleft lip repair as the first case of the first day of the trip. The anesthesiologist had not used Halothane before, but had read about it. The anesthesiologist set up awkwardly, unable to reach his BP cuffs and anesthesia machine controls in the cramped and unfamiliar surroundings. He decided to wait until the next case to switch the equipment around. However, this meant that the original, and very high, induction dose of halothane could not be lowered as the case progressed. The anesthesiologist was also unable to monitor vital signs. After about 30 minutes the surgeon noticed cyanotic blood in the field and alerted the anesthesiologist. The child suffered a cardiac arrest from which he was quickly resuscitated. The most likely diagnosis was halothane overdose.
- inexperience with Halothane
- first case of the day;
- first case of the trip;
- unfamiliarity with the equipment and locale;
- poor set up of equipment;
- reticence to interrupt the surgeon once the problem was noticed;
We are all capable of poor judgement given the right circumstances. Inexperience with halothane led the anesthesiologist to underestimate the risk of continuing with a poor set up. He did not wish to appear incompetent to a surgeon he had just met on the first case of the mission.
Some Facts About Halothane
Halothane is a nonflammable, halogenated hydrocarbon used for inhalation anesthesia. Minimal airway irritation, relatively rapid induction with little or no excitement, and potent bronchodilation make it extremely useful for pediatric inhalational induction. Halothane is metabolized by the liver. The Minimum Alveolar Concentration to prevent movement in 50% of patients (MAC) equals 0.76% (age dependent range 0.5- 1.5%).
Side Effects of Halothane
- slower induction and slower emergence increases risk window for laryngospasm
- significant hypotension (due to myocardial depression plus vasodilation)
- bradycardia with deep anesthetic levels
- greater degree of respiratory depression during spontaneous ventilation (higher risk hypercapnia)
- sensitizes heart to catecholamines, especially during hypercapnia (dysrhythmias such as PVCs and potentially VTach)
- increased risk dysrhythmia with surgical use of epinephrine
- uterine relaxation, increased risk of postpartum hemorrhage
- potential halothane hepatitis with repeat dosing in 1/10,000 adult exposures (low risk in pediatrics)
Halothane overdose causes myocardial depression, hypotension, and bradycardia. Hypoventilation causes hypercapnia, which, in the presence of myocardial irritability, promotes PVCs and more dangerous rhythms. In the worst case scenario, cardiac arrest can occur.
Familiarize Yourself With All Potential Agents At the Site
In the 1990s, I took a week long course at Oxford, England on providing anesthesia in the developing world. It taught me, among other things, how to use Ether in an EMO vaporizer. While I have not used Ether since that course, it’s still in use in the world.
Your mission coordinator should know what agents and equipment are being used at the site. He/she will also know what the team is bringing with them. Some teams bring their own vaporizers and agents. Study the side effects of unfamiliar agents ahead of time. Serious mishaps can occur if you use an unfamiliar agent incautiously.
Tips For Using Halothane
- Halothane is less irritating than Sevoforane. Therefore you can increase concentrations faster during mask induction. However…
- Inhalational induction will still take a few more minutes than for Sevoforane. The results in a longer window when laryngospasm can occur. Don’t rush airway management.
- In frail or sick patients hypotension and bradycardia can develop as a result of vasodilation and myocardial depression.
- Inductions must of necessity use higher concentrations. Reduce those levels toward MAC (0.76%) once you secure the airway and achieve equilibrium, otherwise severe bradycardia, hypotension, or arrest can result.
- Avoid hypoventilation to minimize hypercapnia and the risk of dysrhythmia. Manually assist any patient breathing spontaneously. End-tidal CO2 monitoring will likely be unavailable.
- Work closely with your surgeon related to use of epinephrine. Epinephrine plus halothane, especially in the presence of hypercapnia, can promote PVCs and more dangerous rhythms. If PVCs develop, lowering CO2 by hyperventilating can often help. Consider lowering the concentration of Halothane if appropriate.
- Wake ups will be slower than Sevoforane, causing a longer Stage II window when laryngospasm can occur. Be patient.
Use of Uncalibrated Vaporizers
I once used a halothane vaporizer which was over 15 years old. It had never been cleaned, with the result that thymol preservative precipitated inside, making the top dial almost impossible to rotate to change concentration. As a result, the local engineers welded a pipe wrench to the top to provide leverage. Needless to say, I needed to find MAC for this uncalibrated vaporizer during the first few anesthetics. Since one finds MAC by determining what concentration keeps the patient from moving, those first few cases were interesting indeed.
Maintenance of anesthesia and OR equipment varies considerably from site to site in the developing world. Don’t take for granted that the dial is accurate. While most of the time the vaporizer will deliver far less that the dial setting, don’t assume this. Furthermore, be very mindful of what any potential unexpected movement might do to early portions of the case. Additionally, ask the local providers about any equipment issues or quirks.
Free Standing Vaporizers Can Tip Over
The 3 y.o. child was undergoing a cleft lip repair, intubated and breathing spontaneously with assistance. An unsecured freestanding halothane vaporizer sat on the tabletop, attached to an oxygen source and circuit. About 30 minutes into the case, as the anesthesiologist reached behind the machine to retrieve a fallen laryngoscope, he accidentally knocked over the vaporizer. Liquid Halothane entered the circuit. The child suffered immediate cardiac arrest. The anesthesiologist could not resuscitate the child.
Volunteer groups will sometimes encounter free-standing vaporizers, either at the site or brought by your own team. Regardless of agent, secure such free standing vaporizers to prevent spillage of liquid agent into the circuit, and from there into the patient. The resulting massive overdose, especially of an agent like Halothane, can instantly produce cardiac arrest.
Lack of Familiarity With Inhalational Inductions
One mission to Asia had a mixed anesthesia team composed of volunteer anesthesiologists from the United States and from Colombia. The group used Halothane. The first day, the 2 Colombians had 6 cases of laryngospasm during mask inductions prior to IV start between them. The anesthesia team leader (ATL) assisted with all rescues. The ATL then discovered that the Colombians were accustomed to starting awake IVs on all children followed by IV propofol, succinylcholine intubations. In contrast, the U.S. providers routinely used mask inhalational induction followed by asleep IV to minimize psychological trauma, and to ease IV insertion. As a result, the Colombians opted to switch to the unfamiliar inhalational induction technique instead of their routine. The ATI gave the Colombians tips on mask induction, and gave them permission to use the technique most comfortable to them. There were no further incidents.
- lack of familiarity with the induction technique chosen
- unfamiliarity with Halothane
- reticence to admit inexperience with a technique
- poor team communication regarding sharing of techniques and skill levels
The technique of mask inhalational induction requires practice, as well as patience to wait for the safe moment to stimulate the patient. It is a team approach.
Over-Dependence on Automated Monitors and End-Tidal Monitoring
As ATL, I went to assist one of my team mates during anesthesia on a young child for cleft lip repair. He wanted help troubleshooting his monitors. According to him, the pulse oximeter and EKG had stopped functioning a few minutes earlier and he couldn’t get them to work. The first thing I did was check the pulse. There was none. We turned off the Halothane and performed CPR. Fortunately we resuscitated the child, who thankfully woke up at the end of the case. Without doubt, the most likely cause was Halothane overdose. Never assume lack of pulse oximeter trace or EKG is a monitor failure before checking your patient.
When I began anesthesia training we used manual blood pressure cuffs and listened to heart tones continually through an ear piece. Pulse oximetry, capnography, or end-tidal mass spectrometer agent monitoring did not yet exist. We programmed ourselves to take blood pressures every 3-5 minutes. Strength of the pulse and how crisp and loud the heart tones sounded helped us determine depth of anesthesia. Subtle changes in tidal volume and breathing pattern alerted us to a patient too deep or too light.
Providers In Advanced Countries Are Spoiled
End-tidal monitoring of CO2 and anesthetic gases is now standard of care in the United States. Automatic blood pressure cuffs and pulse oximeters alert us to patient changes. Without doubt, gaining access to all those monitors was a game changer. It increased patient safety and allowed precise titration of inhalational anesthetic. Alarms quickly alerted us of problems.
Unfortunately, the unintended consequence is that most recently trained providers have no experience providing anesthesia without that information. I, as a resident, had to “fly blind”. I assessed all those things by directly evaluating the patient — and quite frankly sometimes guessing. Current anesthesia trainees train from day one to use the automated devices to guide their anesthetic.
Our new equipment and safer anesthetic agents thankfully make it harder to hurt someone. However, it unfortunately creates a situation where providers can go on autopilot during an anesthetic. Ironically, all this safety makes our newer providers generally less prepared for situations where such monitoring is unavailable.
Unfamiliar Vaporizer Types
Visiting developing world ORs is often like viewing a museum of anesthetic devices. Poorer hospitals can’t afford to purchase the newest equipment, or replace old equipment. Older discontinued models are cheaper. Hi-tech hospitals often donate older, out-of-date models as charity.
The challenge is that you often have to use older machines that you never trained on to give anesthesia — most of which lack safety features. Describing the use of the various models of vaporizers and circuits I’ve seen is beyond the scope of this article. However, some of the major types that you may see are listed here with some references.
The Copper Kettle and the Vernitrol are measured flow vaporizers. With a measured flow vaporizer, the total gas flow through the vaporizer determines the concentration delivered. This differs from a plenum flow modern vaporizer where concentration is independent of gas flow.
When using a measured flow vaporizer you change the concentration by changing total flow (oxygen/air/nitrous combined). For Halothane, 5L total flow equals roughly 1% at sea level. For Halothane, reducing flow to 2.5L will yield 2% and 1.25L would be 4%. Isoflurane (Forane) is also 5L flow equals 1%. For Ethrane, another older agent, total flow of 3L equals 1%.
Inhalational overdose is likely if the operator forgets the relationship of total flow to concentration delivered. Ambient temperature and local air pressure will also effect concentration. A device, known popularly as the Whiz Wheel, allows the operator to quickly calculate flow vs concentration.
The drawover vaporizer is robust, very portable and does not require a fresh gas supply, regulators or a flowmeter. Ventilation is via a self filling ventilation bag, or a hand pump bellows. Flow through the device is intermittent, as opposed to plenum flow modern vaporizers which have continuous flow.
The negative pressure generated by a patient taking a spontaneous breath pulls gas into the vaporizer, vaporizes the agent, which then enters the patient. With manual ventilation with a self-inflating bag or bellows, reinflation of the bag after a breath pulls gas into the vaporizer. From there into the bag it enters the refilling bag, allowing the next administered breath to deliver that gas to the patient. Some types (i.e. OMV) can use multiple agents. Supplemental oxygen, if available, is administered via a T-piece connection.
Caveats For Drawover Use:
- The negative pressure of a spontaneous breath or reinflating bag pulls gas through the vaporizer, evaporating agent. The system must be closed to generate this negative pressure. If a mask is used, the mask must fit tightly or room air will dilute the agent and lighten the anesthetic.
- Apply supplemental oxygen to the vaporizer T-piece, and NOT to the ventilation bag or bellows. Oxygen given into the bag or bellows dilutes the anesthetic.
- Assist or control ventilation when used with small children as the work of breathing moving the bag or bellows is high.
- Cannot be used with a scavenger system
A Bain circuit is a version of non-rebreathing Mapleson-D type of anesthesia gas delivery circuit connected to a vaporizer. The function of any breathing circuit is to deliver oxygen and anesthetic gases, and eliminate carbon dioxide.
The standard circle system contains a CO2 absorber and unidirectional valves. Therefore the circle system can be either:
- closed: fresh gas flow exactly equals uptake
- semi-closed: some rebreathing occurs
- semi-open: no rebreathing occurs
A non-rebreathing system, like the Bain Circuit, lacks unidirectional valves and a CO2 absorber. Therefore adequate elimination of CO2 must occur by gas inflow/outflow alone. Work of breathing is low, making this circuit useful for small children. To eliminate CO2, fresh gas flow must be at least 70-100ml/kg/min. Lower flows allow CO2 retention.
A major risk of Bain Circuits is unrecognized disconnection or kinking of the inner, fresh gas delivery hose. If this occurs, the entire corrugated limb becomes dead space. The resulting respiratory acidosis is unresponsive to increased minute ventilation. You must check for an intact circuit before use.
As Anesthesia Team Leader, I came to assist with a 50kg adult patient who had become markedly tachypneic to 50 breathes per minute. The patient was tachycardic to 180 with some PVCs, flushed, and diaphoretic while undergoing cleft palate repair under halothane and oxygen via a Mapleson-D (Bain) circuit. Malignant hyperthermia was suspected.
The anesthesiologist in charge was using 500 ml per minute oxygen flow through the Bain circuit to conserve his oxygen tank supply. Oxygen flow was roughly 7 times lower than required for this adult via such a circuit. Significant hypercapnia was likely present. We increased flows commensurate with the size of the patient (70ml/kg/min x 50 = 3.5L/min) and the symptoms resolved. The anesthesiologist had used Bain circuits on children, but never an adult before.
Be cautious when using an unfamiliar circuit. Ask if you don’t know. Most providers use 5 L flows as a minimum for adult patients using a Bain circuit.
Don’t Count On Alarms and Sophisticated Equipment Being Present
During a cleft palate repair on a young child, the boy was intubated, paralyzed, and ventilated on a portable Ohio ventilator brought from the U.S. The ventilator lacked monitoring alarms. No one noticed the accidental disconnect until too late. As a result, the child died of hypoxic injury. As the patient was on a ventilator, the anesthesiologist did not monitor respirations. No pulse oximeter was available.
Most mission sites will lack end-tidal monitoring. They may not have automatic blood pressure cuffs, EKG or pulse oximetry. Those providers who, like me, trained in the old days can rely on the old ingrained reflexes to run the anesthetic. Younger providers will need to learn those skills in the midst of distraction and austere conditions — unless they practice at home. I’m not suggesting that you turn off your monitors. I am suggesting that you perform anesthesia by actually looking at your patient, and use the monitors as your backup to check your assessment.
You must be more cautious and vigilant than you are at home because you will not have your routine alarms and safety backups. Consider using spontaneous ventilation as a safeguard to accidental disconnects and extubations which occur often with surgery near the airway.
Medical personnel trained in a high-tech environment often take for granted the complex monitoring devices, multiple drug choices, and plentiful support personnel which simplify our job. Medical volunteers are frequently unprepared for the potential hazards produced by outdated technology, unfamiliar equipment, poor sanitation, limited supplies, and a malnourished, often poorly educated patient population.
Be hypervigilant in such an environment. Ask questions and ask for advice or instruction. What you don’t know in such an environment, can hurt your patient.