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Anesthesia Alert
A Better Way to Predict Operative Risk
Idrees Ahmad
Publish Date: October 27, 2008   |  Tags:   Anesthesia

The ASA's Physical Status Classification System is used for purposes for which it was never intended, most notably as a barometer of the patient's operative risk and as a scale to predict whether an operation should proceed. Some payors have even used the ASA PS classification as the determining factor to justify if a patient can be admitted for elective surgery.

Scoring the Risk

The scale Dr. Ahmad created to determine which patients are eligible for outpatient surgery.





Severity of systemic disease and corresponding ASA classification

Mild or none






Type of surgery and length of surgery


Less than 1 hour

Moderately invasive

1 to 2 hours


Longer than 2 hours

Type of anesthesia

Sedation with local anesthesia

General anesthesia with a mask or laryngeal mask airway or regional anesthesia

General anesthesia with endotracheal tube, positive pressure ventilation and muscle relaxants

Although some retrospective reviews have identified risk factors, we lack prospective studies that define real risk predictors. At the clinical level, we still need a way of appropriately putting patients into the right risk category based on their medical status, what anesthetic technique will be used and the surgical trauma from the planned procedure. From an anesthesiologist's point of view, this means doing whatever we can pre-operatively to avoid hospital transfers or emergency room visits post-operatively.

I developed my own system based on the existing data and my clinical experience. By quantifying three categories of information that any anesthesiologist can glean from the patient's chart, I created a scale to determine which patients should have no foreseeable problems, which ones we anesthesia providers should keep a close eye on and which should go to a hospital.

You apply this scale by giving the patient a score of 1 to 3 in each category, so she'd have a total score of 3 to 9. For example, a patient with no systemic condition undergoing a moderately invasive procedure under general anesthesia with an LMA would have a total score of 5, having scored a 1 in the first category and 2's in the second and third. At that point, the patient has few apparent risks, so she is a safe candidate for ambulatory surgery.

A patient with a score of 7 or 8 will require careful perioperative planning for a safe discharge to home. If the patient scores a 9, she is very likely to have a post-operative problem, so much so that it isn't safe to perform the procedure in an outpatient setting. We can objectively reject her and refer the case to an inpatient facility.

After developing this scale, I prospectively applied it to 5,604 patients at my facility throughout 2006. We recorded the data from our OR, PACU and step-down unit as well as what we learned from the 24- to 72-hour post-discharge phone call. During this period, our mortality rate was zero and our morbidity rate was less than 1 percent. Those patients who had complications all recovered quickly with the appropriate treatment or continued monitored observation. In total, we only had seven anesthesia complications for problems such as low oxygen saturation in the PACU and oropharyngeal injury during intubation. Only 14 patients needed hospitalization or a visit to an ER for a surgical or anesthesia complication. We used this scale on a number of patients outside the study period as well and, in more than 10,000 cases, the formula proved invariably accurate in predicting the total operative risk.

Anesthesia Notebook

It doesn't pay to be an anesthesia provider where many Medicare beneficiaries live. A Government Accountability Office report has found that Medicare payments for anesthesia services during such procedures as hernia repairs and laparoscopy were 67 percent lower than private insurers' average payments in 41 Medicare payment localities in 2004. Medicare pays about 87 percent of market rates for most services, but about 34 percent for anesthesia services - a level even lower than another government report found just five years ago, says Wanda Wilson, CRNA, PhD, president of the American Association of Nurse Anesthetists. When the GAO used this information to look at the number of anesthesiologists and CRNAs in an area, they found a distinct correlation between the patient population and the type of provider serving it. Regions with many Medicare beneficiaries tended to have more CRNAs and fewer anesthesiologists, and as the ratio of patients with private payment services rose so did the number of anesthesiologists.

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Don't be surprised if your patients who regularly take opioid-based pain medications begin to exhibit symptoms of obstructive sleep apnea or other sleep-related problems after a few months of therapy. According to an article published online in the journal Pain Medicine, a close relationship exists between apnea and opioid treatments - as well as methadone and benzodiazepines.

Researchers at the Lifetree Clinical Research and Pain Clinic in Salt Lake City studied sleep data on 140 chronic pain patients who were taking around-the-clock opioid therapy for at least six months with stable dosing for at least four weeks. They found a higher than expected prevalence of sleep disorders, with about 75 percent of the patients showing signs of obstructive and central sleep apnea syndromes. In contrast, the rate of apnea in the general population is estimated at 2 percent to 4 percent. The investigators noted that, in these patients, there was no crescendo-decrescendo breath size. This is commonly associated with the disorder in the general public, so the opioid-induced apnea may have a different mechanism than conventional apnea. Since apnea is associated with a higher risk of morbidity and mortality, the study's authors suggest considering this risk when monitoring and adjusting pain medications.

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The perioperative administration of celecoxib during outpatient ACL surgery decreases post-operative pain, opioid use, post-op nausea and vomiting and recovery room length of stay, according to a study in the July 2007 issue of the journal Anesthesia & Analgesia.

Two hundred consecutive patients were randomized to receive acetaminophen 1000mg and either celecoxib 400mg or placebo 1-2 hours before ACL surgery. All patients received intra-articular analgesics (bupivacaine, clonidine and morphine) and had an external cooling system applied to the operative knee. After discharge, patients were told to take acetaminophen 1000mg every 6 hours and celecoxib 200mg every 12 hours or matching placebo for the first 14 days post-op. Oxycodone 5-10mg was available for rescue analgesia.

Patients in the celecoxib group were less likely to experience pain in the recovery room (P < 0.01) and to require opioids (P < 0.001) for post-op analgesia. These patients reported a lower incidence of post-op nausea and vomiting (P < 0.05) and were discharged home earlier (P < 0.05). While at home, patients in the celecoxib group reported lower pain scores both at rest (P < 0.05) and with movement (P < 0.01), and used less oxycodone at all post-op time intervals. These results support the use of celecoxib as a component of a preventive multimodal analgesic technique for ACL surgery.

- Nathan Hall

The need to screen
More surgery is being done in the outpatient setting and we're pushing the envelope of invasive procedures. We need more selective criteria for judging what cases should raise red flags and make us think twice about the risks. At this point, the best we have is the physician's subjective opinions about how to handle each case.

Such a scale would also prove invaluable for those without a great deal of clinical experience. Residents and nurses, for example, could use this system to know when they should raise questions about a patient. It also helps to have defined criteria that are easy to understand when explaining the potential risks to patients and their families and why you've chosen either more intense monitoring or decided not to perform the procedure on an outpatient basis.

Anesthesia Coding Q & A

Question: Can our ASC bill for discontinued procedures that don't involve the use of anesthesia?
Answer: Yes. Under the revised ASC payment system, which takes effect on Jan. 1, surgical centers will be reimbursed 50 percent of the payment rate for discontinued procedures that don't involve the use of anesthesia, says coding and billing specialist Lolita Jones, RHIA, CCS. Under the existing ASC payment system, ASCs don't report modifier -52 (reduced services) for interrupted Medicare procedures because most interrupted covered surgical procedures paid in ASCs would be appropriately reported with modifier -73 or -74 because they generally require anesthesia. Modifier -52 is appended to a service under the Hospital Outpatient Prospective Payment System to signify that a service that didn't require anesthesia was partially reduced or discontinued at the physician's discretion. Modifier -52 is reported under the OPPS for a variety of types of interrupted services, such as radiology services, and CMS believes that there are considerable resource savings to the facility under the circumstances where it is reported. Therefore, under the OPPS, CMS applies a 50 percent reduction to the facility payment for interrupted procedures and services reported with modifier -52.

Question: Can our ASC bill for procedures requiring anesthesia that are discontinued before anesthesia is administered?
Answer: Yes. When a procedure is discontinued after the patient is prepared for the procedure and taken to the OR, but before the administration of anesthesia, ASCs should report modifier -73 (discontinued outpatient procedure before anesthesia administration) appended to the discontinued procedure and they will receive 50 percent of the ASC payment for the planned surgical procedure, says Ms. Jones.

Question: Can our ASC bill for procedures requiring anesthesia that are discontinued after anesthesia is administered?
Answer: Yes, report procedures that are interrupted after their initiation or the administration of anesthesia using modifier -74 (discontinued outpatient procedure after anesthesia administration) appended to the interrupted procedure and the full ASC payment for the covered surgical procedure will be made, says Ms. Jones. CMS says the costs incurred for discontinued procedures that were initiated to some degree are as significant as those for a completed procedure.