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Raising Awareness of Anesthesia Awareness
Here's a look at what you can do to prevent anesthesia awareness.
Dianne Taylor
Publish Date: October 10, 2007   |  Tags:   Anesthesia

Like being entombed in a corpse. That's how Carol Weihrer describes being aware for some potion of her five-hour enucleation/coral implant surgery in 1998. Nearly seven years later, Ms. Weihrer, 52, of Reston, Va., sleeps in two- to three-hour intervals in a recliner because she cannot lie supine. She often awakens with cuts and scratches on her face. At one point, she says she unconsciously dug out her punctum plugs.

Today, Ms. Weihrer suffers from post-traumatic stress disorder (PTSD) because, she says, she became aware during her surgery and cannot rid her mind of the memories. Memories like one surgeon delivering the instructions "cut deeper" and "pull harder" to the other surgeon. Intense tugging on her eye. A blinding white surgical light. Painful burning sensations scorching through her body after an injection of paralytic medication. Most of all, Ms. Weihrer remembers the horrifying feeling of being consciously "entombed" on the operating table with no means of escape.

She has since dedicated her life to warning of the dangers of anesthesia awareness and agitating for changes in how doctors monitor a patient's consciousness. "Shortly after I personally experienced anesthesia awareness - being awake but unable to move while supposedly under full general anesthesia - while having my eye removed, I vowed to make it my mission to prevent even one person from experiencing the same horror and long-lasting consequences," she writes on her Web site, www.anesthesiaawareness.com.

Ms. Weihrer's experience represents the worst that can happen when patients become aware during surgery. Nevertheless, it - along with the ensuing legal battle that Ms. Weihrer says ultimately ended in a "significant" settlement - demonstrates that patients, providers and facilities alike can suffer when a patient awakens during surgery.

Here's a look at what you can do to prevent anesthesia awareness. We also recap what's happened in the EEG-monitoring realm over the last year (see "Update on Consciousness Monitors" on page 43).

Update On Consciousness Monitors

Much has happened in the EEG-monitoring realm over the last year. Some highlights:

Datex-Ohmeda (now part of GE Medical) unveiled its M-Entropy monitor. Unlike competitive monitors, which generate a single display number, the M-Entropy monitor acquires and processes raw electroencephalography and frontalis electromyography information that differentiates intracranial (EEG) activity, from extracranial (muscle) activity. The company says that this reduces the risk of misinterpreting the information.

On the heels of several intraoperative awareness studies supporting the use of BIS monitoring to reduce the risk of surgical awareness, Aspect Medical received FDA clearance on a new 510(k) application indicating the monitor as a tool for reducing awareness risks as well as a tool for quantifying a patient's level of sedation.

Physiometrix and Baxter received FDA clearance for and introduced the PSArray2 sensor, which works with their PSA 4000 consciousness monitor. The sensor, which is applied to the patient's forehead, has new electrode positions that span the bilateral frontal and prefrontal regions. According to the company, the new sensors don't compromise sensitivity to anterior/posterior power shifts at the patient's loss and return of consciousness. Additionally, they are less likely to be distracted by outside signal artifacts and have an improved response to the loading bolus.

Nicolet Biomedical, a division of Viasys Healthcare, no longer offers the SNAP handheld EEG monitor. They do, however, sell the lightweight (21.2 oz), Vitaport 3 Ambulatory System, designed to allow configurations for both EEG monitoring and/or sleep studies. The system records data on a removable flash RAM card and runs on 4 AA batteries. The system is fully compatible with the manufacturer's other software applications, including EEG Vue and EEG to Go.

' Vancouver-based Bionova Technologies plans to enter the U.S. consciousness monitoring market. Bionova recently filed a U.S. patent application for an EEG monitor. The system uses a different analysis technique than monitors presently on the market - it conducts a wavelet decomposition and statistical analysis of the EEG observed by the clinician to baseline reference data, producing a numerical indicator. The company claims on its application that its algorithm reduces the current 15-second to 30-second lag time between the patient's real-time status and the number the clinician sees on the monitor.

- Bill Meltzer

What causes awareness?
Research shows that one or two of every 1,000 patients who receive general anesthesia experience awareness with recall. Researchers have defined five possible causes of awareness:

  • Light anesthesia. Anesthesia practitioners sometimes "go light" intentionally for reasons like cardiovascular comorbidity or emergent situations. Other times, they do so unintentionally. For example, Pete H. Spitellie, MD, and his colleagues at the University of Washington School of Medicine's Department of Anesthesiology have reported that practitioners sometimes neglect to administer a needed second induction dose when intubation is long and difficult. Finally, some believe the pressing need for surgical outpatients to recover quickly promotes an overly light light-anesthesia approach. At least one study that compared awareness with recall between inpatients and outpatients, however, found no significant difference.
  • Machine malfunction. Although technology and alarm systems have reduced machine malfunctions, problems still occur. In Ms. Weihrer's case, for example, the desflurane vaporizer developed a significant leak, and this caused her awareness.
  • Medication errors. Improper dosing or administration of the wrong medication can cause awareness. During pre-induction and induction, for example, a patient may inadvertently receive a muscle relaxant instead of a sedative or hypnotic. Sometimes, syringes can be improperly labeled.
  • Anesthetic approach. Some early research suggests that awareness may be more likely to occur during intravenous or nitrous-only anesthesia than with volatile anesthetics. Total intravenous anesthesia (TIVA), in particular, requires more vigilance and practitioner judgment than inhalational anesthesia, and Dr. Spitellie reports that there is more patient-to-patient pharmacokinetic variability with this approach. In one study of 56 elective surgical patients asked to squeeze the observer's hand during target-controlled deep sedation with propofol/alfentanil infusion, a full 16 percent recalled the incident after recovery.
  • Increased anesthetic requirements. Medications, chronic drug or alcohol use, and obesity may alter anesthetic requirements.

Anesthesia awareness can be very distressing for patients, especially when the patient is paralyzed. The majority of patients who experience awareness tend to suffer some sleep disturbances, nightmares, anxiety and/or flashbacks. Some-times, as in the case of Ms. Weihrer, chronic PTSD sets in.

There are consequences for practitioners and facilities, as well. A 1999 analysis of 4,183 closed malpractice claims from the database of the American Society of Anesthesiologists showed that 1.9 percent were awareness claims. Payments ranged from $1,000 to $23.2 million, although the median payments for patients inadvertently paralyzed while awake and for patients who experienced recall during general anesthesia were $10,250 and $105,000, respectively, according to Dr. Spitellie's report.

Tips for prevention
To prevent anesthesia awareness, experts recommend considering the following guidelines:

  • Administer amnestic premedications, especially if the patient requires light anesthesia.
  • Vigilantly monitor and maintain equipment.
  • Avoid complete neuromuscular blockade when possible. Muscle relaxants prevent patient movement (the best indicator of light anesthesia), and thereby prevent practitioners from assessing awareness with verbal commands. Research suggests that awareness is more common in general anesthesia patients who are paralyzed than in general anesthesia patients who are not.
  • Include an adequate concentration of volatile anesthetic when administering an inhalational general anesthetic regimen.
  • Use supplemental doses of an induction agent if induction is long and difficult.
  • Monitor depth of anesthesia. Hemodynamic changes can occur for many reasons, and they do not always occur during awareness. In addition, a prospective case study suggests that end-tidal monitoring of anesthetic gas concentration did not prevent awareness. Recent research suggests that monitoring of hypnosis with electroencephalogram-based monitors (bispectral index - BIS - monitors, for example) can reduce awareness by approximately two-thirds. However, while BIS levels are lower in non-responsive than responsive patients, levels can vary widely. Some have speculated that different anesthetics have different effects on BIS values.
  • Consider awareness education. Even though about half of all anesthesia practitioners have experienced awareness, research suggests that practitioners may not understand awareness or know how to manage it. By increasing provider awareness, you may decrease the incidence of anesthesia awareness.

When awareness does occur, the worst thing the healthcare team can do is disbelieve or ignore the patient. Intraoperatively, if a patient becomes aware, the practitioner should explain the situation and offer affirming comments until the patient loses consciousness, according to one expert. Post-operatively, Dr. Spitellie and his colleagues recommend compassionate consultation or debriefing to prevent a prolonged traumatic reaction. Frequent follow-up is important, as is a referral to a psychologist or psychiatrist if symptoms like anxiety, flashbacks and nightmares persist.

Some patients fail to report awareness experiences, however, and this can prevent or delay treatment. Although some practitioners may resist the idea of discussing the potential for awareness with patients before surgery, Dr. Spitellie and his colleagues suggest that this could prevent patient suffering and subsequent litigation because the patient will be more likely to report the incident early and receive appropriate treatment.

Overall protection
Research suggests that many patients worry about awakening during surgery, and growing media attention to this issue may increase these anxieties. By counseling appropriate patients, taking measures to prevent anesthesia awareness and initiating proper care when it does occur, you can address these fears head-on while better protecting your facility, your practitioners and your patients.