Scientific Papers on Patient Safety Presented at the 2008 Annual Meeting of the American Society of Anesthesiologists

Steven B. Greenberg, MD; Glenn S. Murphy, MD; Jeffery S. Vender, MD

Over 1,700 abstracts were presented at the 2008 American Society of Anesthesiologists annual meeting in Orlando, FL. As in previous years, a number of these abstracts examined issues directly related to patient safety. This brief review will highlight a few of the important abstracts discussed at the meeting.

Patient Databases and Anesthesia Morbidity & Mortality

Hospitals often seek information regarding risk factors for morbidity and mortality from their own patient databases. One study (A845) at Columbia University utilized the International Classification of Diseases (ICD) codes to report that anesthesia complications were documented as the underlying cause of death in 11% of cases. Forty-seven percent of deaths were related to anesthetic overdoses, and another 42% of adverse effects were noted when anesthetics were being utilized in the therapeutic range. Men were twice as likely to die when compared to women, and this mortality rate increased substantially after age 65 (A845). Another study (A378) analyzed national estimates of anesthetic complications in 2005 by utilizing the Healthcare Cost and Utilization Project’s (HCUP) Nationwide Inpatient Sample (NIS). A total of 39,506 hospitalizations had at least 1 anesthetic complication in 2005, resulting in an incidence of 1 case per 1000 admissions. Labor and delivery was associated with approximately half of all complications. Women and patients between 25-34 years of age were associated with a higher risk of anesthetic complications. Litz et al. (A428) from Dresden, Germany, reviewed a 10-year survey of 20,000 patients undergoing spinal anesthesia and discovered that 13 cardiac arrests occurred without warning signs in healthy patients undergoing elective surgery (incidence=0.6%). All patients underwent successful cardiopulmonary resuscitation and recovered without neurologic sequelae. Further analyses such as the ones above may allow for the creation of preventative measures to reduce morbidity and mortality rates.

One abstract reported predictors of impossible mask ventilation in a large patient sample size. Data from Kheterpal et al. (A1243) prospectively reported 70 cases of impossible mask ventilation (IMV) in a sample of approximately 47,000 over a 4-year period (incidence=0.15%). Independent risk factors for IMV included: male sex, history of sleep apnea, Mallampati III or IV, and a history of neck radiation. Twenty-six percent of these patients were difficult to intubate.

Abstract A803 retrospectively analyzed the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database to generate a list of potential predictors of post-operative acute renal failure (ARF). Acute renal failure developed in 1% of the 69,000 patients evaluated. A logistic regression full model fit revealed the following predictors of ARF: age ≥58, male sex, diabetes mellitus, congestive heart failure, myocardial infarction within the prior 6 months, ascites, hypertension, previous cardiac procedure, emergency surgery, preoperative renal insufficiency, and high-risk surgery. By revealing these predictors through large database analyses, risk reduction may be addressed.

Three other abstracts examined morbidity and mortality associated with the use of perioperative statins, beta blockers, and morphine patient controlled analgesia (PCA). Huffmyer et al. (A804) analyzed 2,657 patients undergoing CABG surgery from 1998-2007. Patients who received a preoperative statin had a reduction in perioperative mortality of 45%. In addition, preoperative statin use was associated with a reduction in the need for hemodialysis by 42%. Another study examined 5,000 patients undergoing non-cardiac surgery between 2004-2006 (A846). Multiple logistic regression revealed that both beta blockers and acute perioperative anemia were independent predictors for death and myocardial infarction (MI). For every 10% decrease in hemoglobin, the odds of death and MI were 1.33. The probability of mortality or MI was progressively more likely for patients who received beta blockers in the setting of a reduction of hemoglobin by <30%. In a large retrospective cohort (A31) of nearly 700,000 patients who received intravenous morphine PCA, 5.5% required naloxone for opioid overdose. Naloxone use was associated with an increased hospital length of stay, a higher rate of intensive care use, a higher total hospital cost, and a higher rate of in-hospital death. Further prospective data should address all of these associations.

Medical Errors

Iatrogenic errors continue to be an important issue facing hospitals worldwide. Sandnes et al. (A770) from the University of Washington reviewed the ASA Closed Claims Project to assess liability associated with medication errors during anesthesia. Medication errors accounted for 3% of claims between 1990-2001. Incorrect dosing accounted for 44% of claims made, while 30% of claims involved substituting one drug for an intended drug. A higher proportion of pediatric medication errors existed. These claims were often found to be preventable and contributed to a higher proportion of permanent brain damage when compared to other claims made. Another study (A765) from Fukuoka, Japan, retrospectively analyzed 64,285 in hospital anesthetics and discovered 50 cases associated with drug errors (incidence=0.078%). None of these led to serious sequelae. Giving the wrong medication and overdosing contributed to nearly 90% of all medication errors.

Several abstracts investigated tools to reduce medical errors. Wassef et al. (A758) observed practices of 18 anesthesiologists, nurses, and residents when drawing up and labeling medications at Penn State. The authors found that peel off labels were associated with fewer errors and improved time efficiency when compared to black and white labels. Levine et al. (A759) discussed their development of a new system that reliably reads vial barcodes and creates labels at the point of care. This system was developed to reduce drug errors and improve efficiency over time. Abstract (A767) discusses the development of a standard (IEC 62366) to assist manufacturers in improving the safety and usability of medical devices. This standard generates an engineering process for locating, assessing, and reducing risks. Further studies are required to validate the above technological processes to reduce medication errors.

Perioperative Glucose Control

Perioperative glycemic control continues to be an area of active investigation. Abstract (A233) examined whether blood glucoses of ≥140 mg/dl alter expression of HLA-DR and the function of monocytes that are integral in fighting infection. Among 152 ASA III and IV patients studied, those patients with a glucose ≥140 mg/dl had a significantly higher infection rate (26.4% vs. 11.1%) than those with a glucose <140 mg/dl. No significant difference was found in relation to HLA-DR expression of monocytes or
ex vivo secretion of TNF-alpha and IL-10 when comparing patients with glucoses ≥140 mg/dl versus patients with glucoses <140 mg/dl. Abdelmalak et al. (A234) examined the safety and feasibility of intensive insulin therapy (glucose goal= 80-100mg/dl) versus conventional therapy (glucose goal=180-200 mg/dl) in major non-cardiac surgery. Among the 54 patients studied, no hypoglycemic episodes occurred in either group. However, the conventional group was associated with both higher glucoses and greater glucose variability. Data (A473) from the University of Virginia, retrospectively reviewed 1,359 patients admitted with subarachnoid hemorrhage and the effects of an intensive insulin treatment protocol on outcomes. Survivors had a statistically lower mean admission and mean average glucose when compared to non-survivors. However, implementation of the protocol had no effect on overall mortality. In fact, a subgroup of patients maintained between 120-180 mg/dl per protocol had a statistically significant increase in mortality from 19.4% to 27.6%. Further prospective studies will need to validate these results.

Anesthetic Depth and Monitoring

The effect of the depth of anesthesia monitoring on outcomes remains controversial. Abstract A192 performed at Duke University enrolled 595 patients undergoing sedation primarily for colonoscopies monitored by bispectral analysis (BIS) outside the operating room. The average BIS value during the procedures was 49±17. Seventy-eight percent of patients had a BIS <60 for greater than 5 minutes. Adverse events occurred in 6% of the patients and included: oxygen desaturation, pain, hypertension, hypotension, restlessness, difficulty in arousal, and tachycardia. Deep sedation correlating with BIS values associated with general anesthesia may lead to adverse events. Sieber et al. (A445) prospectively observed 40 patients undergoing procedures with spinal anesthesia and propofol sedation with BIS monitoring. Patients were divided into a standard care group (usual clinical routine) and a targeted sedation group (sedation was adjusted based on response to verbal questions). Average BIS levels and time spent at BIS levels consistent with general anesthesia were less in the titration group. A third abstract (A1) evaluated 1,941 patients undergoing major surgery for the possible association between deep hypnotic time (DHT) (or time a patient spends below a BIS<45) and mortality. Cardiac surgery patients who died within a year of surgery had a median 50.7 minute longer DHT (p = 0.004), while non-cardiac surgery patients who died within a year of surgery had a median 5.7 minute longer DHT (p = 0.21). Therefore, the authors demonstrated an association between DHT and mortality in the subset of cardiac surgical patients.

While deep sedation may correlate with an increase in adverse events, lighter levels of general anesthesia may result in awareness. Divan and Mathews (A985) performed a systematic review of 25 studies that adopted awareness risk reduction strategies and noted that risk reduction strategies were associated with a significant decrease in anesthesia awareness when compared to historical controls (high-risk patients: 0.16% vs. 0.96%). Another study (A1347) from Beijing, China, analyzed nearly 11,000 patients and discovered 45 cases of awareness (incidence=0.41%). Factors associated with awareness included female sex, increased ASA status, anesthesia history, anesthesia methods, and type of operations.

Miscellaneous

An abstract (A30) from Dartmouth Medical Center, examined the institution of the Masimo Patient Safety Net system, which consists of a Radical 7 oximeter and radio transmitter per bed, a pager per nurse, and a central station for admission/discharge. This monitoring system was placed in a 36 bed surgical unit. At the end of 3 months, mortality and rescue activations were decreased when compared to the prior 11 months without this system. Another prospective observational study (A384) examined patients taking proton pump inhibitors (PPI) prior to surgery. Those on PPIs had increased levels of TNF-alpha perioperatively. In addition, patients who were taking PPIs had a higher rate of infection and a longer hospital length of stay. Further randomized studies need to validate these results.

Other abstracts investigated perioperative management techniques and associated adverse events. Abstract (A1589) reported a post-hoc analysis of data from the ECLIPSE trial comparing intravenous antihypertensives for cardiac surgical patients. The authors observed that increases in blood pressure lability were associated with increased rates of 30-day death, stroke, myocardial infarction, and renal dysfunction. Another study (A841) randomly assigned 49 patients with primary breast cancer to either propofol/paravertebral anesthesia or sevoflurane/opioid anesthesia. Propofol/paravertebral anesthesia was associated with a reduced level of IL-1B and IL-8 and an increase in IL-10 when compared to the sevoflurane/opioid group. The favorable response with propofol/paravertebral anesthesia may lead to resistance of tumor progression, metastasis, and recurrence. Larger studies need to investigate this further.

This brief review summarized only a small number of the important abstracts on patient safety presented at the 2007 Annual Meeting. The abstracts referenced do not necessarily reflect the opinions of the authors or the APSF. To view other abstracts on patient safety, or to obtain further information on the abstracts discussed in this review, please visit the Anesthesiology website at
www.anesthesiology.org.

Drs. Greenberg, Murphy, and Vender are affiliated with the Evanston Northwestern Healthcare Department of Anesthesiology. They also serve on the APSF Editorial Board.