Where there is fire, even some of the most severely injured victims might not be identifiable by burns. “Severe inhalation injuries can occur with just one breath,” says Jo-El Detzel, RRT, lead clinical specialist with the Arizona Burn Center, Phoenix.

That breath could blister the lungs or deliver toxins, such as carbon monoxide, which poison the body. For patients who also have suffered burn injuries, repeated trips to surgery and severe pain can complicate recovery. Each case is unique, and medical professionals approach each patient understanding this.

That is why respiratory therapists often have no protocol for weaning burn patients from ventilation. “It’s difficult to develop an algorithm that comprises all the variables,” says Detzel. But the Arizona Burn Center is working on it. Detzel credits the center’s associate medical director, Marc Matthews, MD, and the director of cardiopulmonary services, Mark Hibbert, RRT, CPFT, with leading the effort to create the algorithm and protocol. The guidelines will be intended to provide a starting point for physicians when they write their orders, according to Detzel.

In the meantime, informal protocols exist that guide professionals at their individual institutions. Many incorporate a multidisciplinary approach to the extubation process and monitor multiple variables. Their goal is to time the process to maximize recovery and limit complications.

Ready for Extubation?

Extubation often occurs as soon as the medical team determines the patient is ready. “As the conditions that warranted placing the patient on mechanical ventilation stabilize and begin to resolve, attention must be placed on removing the ventilator as quickly as possible,” says Ronald P. Mlcak, PhD, RRT, FAARC, director of respiratory care, Shriners Hospital for Children, Galveston Burn Hospital, and associate professor of respiratory care at the University of Texas Medical Branch in Galveston.

The Specifics of Extubation

When evaluating patients to determine whether they are ready for extubation, Ronald P. Mlcak, PhD, RRT, FAARC, director of respiratory care at the Shriners Hospital for Children, Galveston Burn Hospital, and associate professor of respiratory care at the University of Texas Medical Branch in Galveston, shared specifics from the evidence-based protocol the institution has developed.

To determine if patients are ready for extubation, they should exhibit:

  • a respiratory rate in children between 38 and 45 breaths per minute (BPM);
  • expired minute ventilation (VE) less than or equal to 15 L/min;
  • mean blood pressure that is greater than or equal to 60 and less than or equal to 120 mm Hg;
  • Pao2/Fio2 (P/F) ratio is greater than or equal to 250;
  • fraction of inspired oxygen (Fio2) is less than or equal to 0.4; and
  • positive end expiratory pressure (PEEP) is less than or equal to 8 mm Hg.

In addition, the patient should not be receiving a high dose of vasopressors;

Prior to an SBT (spontaneous breathing trial), the care team looks for:

  • a respiratory rate in children between 38 and 45 BPM;
  • spontaneous tidal volume measuring greater than or equal to 4 mL/kg;
  • spontaneous vital capacity greater than or equal to 8 mL/kg; and
  • a negative inspiratory force measuring greater than or equal to 60 cm H2O.

“There also should be an audible leak around the endotracheal tube during mechanical ventilation when the endotracheal tube balloon is deflated,” says Mlcak.

During the weaning and extubation process, the respiratory therapist or registered nurse on the team will monitor the patient for failure of an SBT using the following criteria:

  • respiratory rate greater than or equal to 50 BPM
  • dyspnea, diaphoresis, use of accessory muscles;
  • Spo2 less than or equal to 90%;
  • mean blood pressure less than or equal to 60 or greater than or equal to 120 mm Hg; and
  • heart rate increase of 20% or an absolute heart rate greater than or equal to 170.

Mlcak’s burn center team uses evidence-based guidelines for weaning and discontinuing ventilator support, which are modified to meet patients’ specific needs. “Our guidelines were based on an article that was published [by the AARC1]. Modifications to the guidelines were made to meet the clinical demands of our unique patient population,” Mlcak explains.

The protocol for assessment is very specific. Patients are assessed every morning using various criteria: some reversal of the underlying need for mechanical ventilation; an adequate cough that is cooperative and responsive with no excessive secretions; and other factors that include respiratory rates, mean blood pressure, vasopressor dosage, Pao2/Fio2, the fraction of inspired oxygen, and positive end expiratory pressure (PEEP).

Fluid imbalances, pain management, and future medical plans, such as additional surgeries, also will influence a decision to extubate. “Nurses monitor fluid in and out to determine if there is an imbalance. Too much fluid can result in pressure on the chest,” says Arizona’s Detzel. Similarly, high levels of sedation, often seen in burn patients because of their extreme levels of pain, may impair a patient’s sensation during extubation as well as the ability to comprehend directions or communicate problems clearly.

At the Boston Shriners Burn ICU, children are assessed in four areas prior to extubation, according to Rob Sheridan, MD, director of the burn surgery service. “These areas are airway patency, lung-chest wall mechanics, gas exchange, and sensorium. The airway is said to be patent if there is at least a 20 cm H2O around the deflated cuff of a properly sized endotracheal tube. Lung-chest wall mechanics are felt to be adequate if compliance is near the normal range, with, for example, 10 cc/kg tidal volumes on 10 cm H2O or less of positive pressure. Gas exchange is adequate for extubation if less than 40% Fio2 is required to maintain oxygen saturations in the mid-90% range. Finally, the sensorium must be clear enough for the patient to guard their airway, cough, and follow simple directions once the tube is out.”

Respiratory mechanics help to evaluate a patient’s ability to sustain spontaneous ventilation, but they do not assess a patient’s ability to protect the upper airway, says Mlcak. He suggests that a bronchoscopic examination will provide a more complete evaluation of whether the edema has decreased enough to allow clear breath.

Because of the many factors that need to be monitored, most centers take a multidisciplinary approach to care, including the extubation process. The entire team often makes daily rounds together, discussing individual cases; everyone has the chance to provide input.

Detzel notes her team includes the nurse manager and nurses, pharmacy, nutrition, physical therapy and occupational therapy, social workers, quality control, the attending physicians, the residents, and, of course, respiratory care. “Even pediatric ICU attendings will participate. We cover each patient’s issues and will take pictures to document improvement,” says Detzel.

The Protocol

By the time a decision to extubate has been made, many patients have been ventilated for an extended period of time and require a weaning period, according to Sheridan. “We use standard weaning protocols in terms of the pulmonary mechanics. Burn patients are unique in their requirement of large doses of opiates and benzodiazepines to maintain comfort. These also need to be weaned to ensure a sensorium compatible with extubation. In many cases, patients will require supplementation with propofol or other short-acting anesthetics to facilitate a safe and comfortable medication wean,” he says.

At the Arizona Burn Center, patients are weaned from ventilation over 6 days once conditions are right. “We primarily make sure the Fio2 is at 40% and the PEEP is at 5. Then we do trach trials, increasing the time the patients are breathing on their own every day. At night, the patient rests,” says Detzel.

Detzel notes that the airway pressure release ventilation (APRV) could be used to wean a patient from high settings to completely off the ventilator, but her team prefers to use trach trials as a more cautious approach.

Respiratory mechanics are usually monitored prior to, during, and post-extubation. At Shriners in Galveston, once the required conditions are met for a spontaneous breathing trial (SBT) (see sidebar above), the team may initiate either a tracheostomy-tube trial for 30 minutes or pressure support ventilation (PSV) with 5 cm H2O or continuous positive airway pressure (CPAP) of 5 cm H2O for 1 hour. Respiratory mechanics are monitored during this process and measurements are taken at the conclusion of the SBT, says Mlcak. The patient is then returned to the prior ventilator setting and reassessed. If patients fail any of the criteria during the test, they are returned to ventilation.

Postextubation Complications

In younger children, there is about an 8% extubation failure rate, estimates Sheridan. Of these failures, 80% are due to postextubation stridor, with airway swelling compromising patency enough that the work of breathing is unacceptable. The team uses steroids in such patients to try to prevent the swelling, starting the therapy about 12 hours before extubation.

Setting the World on Fire

The American Burn Association (ABA of Chicago) shares a number of related statistics on its Web site,1 which include:

  • an estimation of more than 1 million burn injuries per year: This number has fallen from 2 million since the first report of the National Health Interview Survey (NHIS), which used data from 1957 through 1961.1
  • an estimated 4,500 fire and burn deaths per year: This includes deaths resulting from burns as well as smoke poisoning.
  • roughly 45,000 burn-related hospitalizations annually: approximately one half of these are admitted at specialized burn treatment centers and one half at hospitals.
  • an average burn injury size of roughly 14% of total body surface area (% TBSA): Burns of 10% TBSA or less account for 54% of burn center admissions, while burns of 60% TBSA or more account for 4% of admissions.
  • approximately 6% of burn center admissions do not survive; most of these patients have suffered severe inhalation injury in fires.

Reference

1. American Burn Association. Burn Incidence and Treatment in the US: 2000 Fact Sheet. Available at: www.ameriburn.org/resources_factsheet.php. Accessed on December 8, 2006.

“Problems with postextubation edema can be managed with the use of heliox therapy. Our patients are usually out of bed and ambulating on postoperative day 5,” says Mlcak.

“Inhalation injury patients often have an early window of good pulmonary function that the burn team tries to utilize to perform early surgery. After several days, sloughing endobronchial epithelium can contribute to pulmonary dysfunction requiring good pulmonary toilet,” says Sheridan.

The change often is attributed to edema, which can complicate not only extubation but surgeries and other procedures as well. Mlcak estimates that acute upper airway obstruction occurs in approximately one fifth to one third of hospitalized burn victims with inhalation injury. “[It] is a major hazard because of the possibility of rapid progression of mild pharyngeal edema to complete upper airway obstruction with asphyxia,” says Mlcak.

Unplanned extubations, therefore, can become particularly serious. “An unplanned extubation is challenging in any setting but can mean death in the burn unit. With facial and upper airway edema, it can be extremely difficult to get the tube back in, so we are very careful and try to minimize the incidence of unplanned extubation,” Sheridan says.

Because there is no test to measure exactly how serious an inhalation injury is, the care team will not know the extent of the damage and potential complications right away. “It’s difficult to make an early diagnosis of the severity of an inhalation injury,” says Sheridan.

He suggests that this has implications for the decision to intubate. “We don’t like to intubate patients if we don’t have to because intubation brings requirements for sedation, vascular access, and other risks. Having said that, sometimes the patient is better managed intubated. Typically, the bigger the burn and the younger or older the patient, the more likely we are to intubate,” says Sheridan.

Once the patient is intubated, the goal is to extubate as soon as possible. “It is imperative to do an SBT daily on patients and to liberate patients from mechanical ventilation as soon as possible, especially children. Since many patients who require mechanical ventilation have a concomitant inhalation injury, we feel that early extubation will decrease VAP [ventilator-assisted pneumonia], tracheal stenosis, and tracheal malacia,” says Mlcak.

He adds, “It is imperative that a well-organized, protocol-driven approach to weaning burn patients from mechanical ventilation be utilized so that improvements can be made, and the morbidity and mortality associated with inhalation injury can be reduced.”

Renee Diiulio is a contributing writer for  RT. For more information contact rtmagazine@allied360.com.

Reference

  1. Evidence-based guidelines for weaning and discontinuing ventilatory support. A collective task force facilitated by the American College of Chest Physicians, the American Association for Respiratory Care, and the American College of Critical Care Medicine. Available at: [removed]www.rcjournal.com/online_resources/cpgs/ebgwdvscpg.asp[/removed]. Accessed December 20, 2006.