Anesthesia Literature Review

J. Lance Lichtor, M.D., Editor 

Predicting the risk of postoperative complications may help to reduce costs, length of hospital stay, and patient suffering. A retrospective review of one physician's patients (N = 226) who underwent elective major operations was conducted to determine whether preoperative functional measures of patients' health status can predict postoperative complications. Patients with more comorbidities had increased frailty index (FI) scores (r = 0.61; P < 0.001). FI scores also showed significant correlations with all domains of the SF-36, a survey measuring a patient's physical and emotional health (P < 0.001). Multivariate analysis confirmed that higher FI scores were associated with an increased risk (OR = 2.71) of postoperative complications; however, bodily pain was associated with a decreased risk (OR = 0.45). Other independent risk factors included operation complexity, and the role-emotional domain of the SF-36.

This study used an FI score and the SF-36 together to model and predict postoperative complications. FI scores and subscores on the SF-36 were predictive of adverse events. Surprisingly, the role-emotional domain of the SF-36, along with the FI score, best predicted postoperative complications.

The rates of posttraumatic stress disorder (PTSD) and concussion or mild traumatic brain injury (MTBI) are high among veterans. This cohort study was conducted to assess the longitudinal associations between concussion or MTBI and PTSD in combat-deployed National Guard soldiers using a survey (N = 953). The rates of injury and psychiatric complications significantly increased from in-theater (1 month before returning home, time 1) to postdeployment (1 yr after returning home, time 2) assessments (see fig. ). PTSD symptoms were similar in soldiers who did or did not report concussion or MTBI at time 1. Similarly, those reporting concussion or MTBI at time 1 had similar rates of PTSD at time 2 compared with those who did not (30.2% vs.  30.4%). Reports of PTSD at time 1 predicted symptoms at time 2. Reports of concussion or MTBI at time 1 did not predict symptoms at time 2.

This report clearly establishes a strong association between combat-related PTSD and postconcussive symptoms and psychologic outcomes 1 yr after soldiers returned from Iraq. These results have important implications for screening and treatment.

Previous studies have demonstrated an association between patient mortality and in-hospital nurse staffing. However, because of the design and data selection used for the previous studies, the results may not be reliable. Therefore, data from a large tertiary academic medical center of 197,961 admissions and 176,696 nursing shifts were reviewed to examine the association between staffing levels and individual patient experiences. There was a significant association between mortality and exposure to either reduced staffing or high-turnover shifts (P < 0.001 for all) (see fig. at top of next page ) The risk of death significantly increased with increased exposure to below-target shifts (P < 0.001) and high-turnover shifts (P < 0.001).

The authors evaluated data from almost 200,000 patients with electronic data systems from a single hospital. Nurse staffing 8 h or more below the adjusted target and patient turnover greater than 1 SD above the mean dayshift turnover rate for that unit were each associated with an increased risk of death. Patient census at the beginning of the shift, target staffing, and number of shifts in an intensive care unit were significantly associated with mortality.

Although a history of myocardial infarction (MI) has been associated with increased risk for reinfarction or death after noncardiac surgery, the supporting data are not based on current clinical practice. This retrospective analysis of the California Patient Discharge Database analyzed 563,842 records of patients undergoing noncardiac surgeries between 1999 and 2004. Overall, 2.9% of patients had experienced an MI within the past year, and these patients had greater comorbidity scores (P < 0.001). The postoperative MI rate was higher in patients with an MI within 30 days of surgery compared with those without, regardless of surgery type or indication (32.8% vs.  1.4%; P < 0.001). Thirty-day (14.2% vs.  3.9%) and 1-yr mortality (41.2% vs.  13.3%) were also higher in patients with a recent history of MI compared with those without. Mortality decreased as time from recent MI increased.

This recent large study supports previous findings that surgery should be delayed for patients with recent MI. The risk of postoperative MI was significant even within 60 days of the previous MI.

Although new sensitive troponin assays may improve the early diagnosis of myocardial infarction (MI), it is unclear if a lower detection threshold improves clinical outcomes in patients with suspected acute coronary syndrome. Consecutive patient records from a single institution in Scotland were reviewed during the validation (n = 1,038) and implementation (n = 1,054) phases of this study to evaluate sensitive troponin assays and clinical outcomes. In the validation phase, patients with troponin concentrations of 0.05–0.19 ng/ml were older and more likely to have a history of ischemic heart disease and diabetes mellitus. Troponin concentrations of 0.05–0.19 ng/ml were significantly associated with 3-month and 1-yr complications. Decreasing the diagnostic threshold to 0.05 ng/ml, in the implementation phase, decreased the risk of death and recurrent MI (see fig. below ).

Given that troponin assays have become more sensitive, what concentration of troponin should be used to diagnose MI in patients with acute coronary syndrome? In one hospital in Scotland, when the diagnostic threshold was decreased, detection of MI was increased by 29%. Clinical management, including an increase in the use of evidence-based therapies, was improved, the death rate decreased, and admissions due to recurrent MI were reduced.

Jean Mantz, M.D., Ph.D., Editor 

Few studies have evaluated the long-term outcomes of survivors of acute respiratory distress syndrome. In this prospective, longitudinal cohort study, patients (N = 109) with acute respiratory distress syndrome were monitored for as long as 5 yr after intensive care unit discharge to evaluate physical, mental, and quality-of-life outcomes. Patients had a reduction in ability to exercise, as measured by a 24% reduction in the median distance walked compared with age- and sex-matched controls. There was also a significant correlation between the physical component on the SF-36 and the distance walked (P < 0.001). The SF-36 physical component score was lower than age- and sex-matched controls. Younger patients had a greater rate of recovery during the 5 yr. Only 77% of patients had returned to full-time work at the 5-yr follow-up. However, lung function was normal or near-normal at 5 yr.

The accompanying editorial based on this long-term follow-up study emphasizes that lung function was fully recovered 5 yr after acute respiratory distress syndrome, and that survivors of the syndrome have long-term physical and quality-of-life burdens. Persistent weakness and psychologic factors may contribute to exercise limitations and reduced quality of life. Healthcare costs for these patients were also increased.

Delirium can occur in as many as 80% of patients in intensive care units. Impaired cholinergic neurotransmission may contribute to delirium. Therefore, a multicenter, double-blind, placebo-controlled randomized trial was conducted to test the effects of rivastigmine, an acetylcholinesterase and butyrylcholinesterase inhibitor. Patients (N = 104) received either increasing doses of rivastigmine (1.5–6 mg) or placebo twice daily as an adjunct to usual care, based on haloperidol. Despite a planned enrollment of more than 400 patients, the study was terminated early after review by the data safety monitoring board. Mortality was 14% higher in the treated group compared with placebo (22% vs.  8%; P = 0.07). Furthermore, the median duration of delirium was 2 days longer in the rivastigmine group (5 vs.  3 days; P = 0.06), and delirium severity was significantly higher in the rivastigmine group.

The results indicate that addition of a cholinesterase inhibitor to haloperidol does not have a beneficial impact in terms of duration of delirium and even worsens outcome. Although it is possible that other drugs may be effective and safe to treat delirium, this article emphasizes that delirium results from a variety of causes (including organic causes) in critically ill patients and that uniform additional pharmacologic therapy may not attenuate the impact of delirium on patient outcome.

Several lines of evidence suggest that hydrocortisone may reduce complications (e.g. , pneumonia, mechanical ventilation, and death) after traumatic brain injury (TBI). In this multicenter, randomized, double-blind, placebo-controlled study, hydrocortisone-treated, polytraumatized patients (HYPOLYTE study; N = 150) with severe trauma received either hydrocortisone (200 mg/day for 5 days followed by 100 mg on day 6 and 50 mg on day 7) or placebo. Treatment with hydrocortisone reduced the incidence of hospital-acquired pneumonia at 28 days (see fig. below ). Treated patients also had significantly more mechanical ventilation-free days (16 vs.  12 days; P = 0.001) and a lower incidence of acute respiratory distress syndrome (4.1 vs.  14.5%; P = 0.04) than did patients in the placebo group. More patients (6 of 72 vs.  4 of 76) died in the hydrocortisone group than in the placebo group.

In this randomized, double-blind, placebo-controlled trial, a 7-day treatment with hydrocortisone markedly reduced the rate of ventilation-acquired pneumonia in this patient population. However, future trials are needed to clarify the efficacy and safety of hydrocortisone before any recommendation for clinical routine practice can be made. Unfortunately, this study was not powered to assess the impact of hydrocortisone on mortality. This is of particular interest, particularly in severe traumatic brain injury, because previous studies have shown an increase in mortality after such injury in patients administered methylprednisolone (CRASH trial).

Selective oropharyngeal decontamination (SOD) has been shown to improve clinical outcomes compared with standard of care or selective digestive tract decontamination (SDD) in patients in the intensive care unit. A large, multicenter, open-label, clustered group-randomized, crossover study was conducted to evaluate the effectiveness of SOD in comparison with SDD and standard of care in preventing respiratory tract colonization and bacteremia with intensive-care-unit-acquired resistant microorganisms. Patients who received SDD or SOD had higher acute physiology and chronic health evaluation (APACHE) II scores and were more often mechanically ventilated than were patients in the standard care group. Bacteremia was more common in standard care than it was in SDD or SOD (odds ratio [OR]= 0.44 and 0.66, respectively; see fig. below ). The incidence of bacteremia caused by highly resistant microorganisms was 59% less frequent with SDD than with standard care (OR = 0.41) and 63% less frequent with SDD than with SOD (OR = 0.37).

In an analysis of almost 6,000 patients in 13 Dutch medical centers, SDD was associated with a reduced incidence of acquired bacteremia and respiratory tract colonization caused by highly resistant microorganisms. SOD was also associated with lower rates of acquired respiratory tract colonization with highly resistant organisms. Extended use of the interventions described in institutions with low rates of antibiotic resistance is warranted; however, whether resistance develops after long-term use is unclear.

Timothy J. Brennan, Ph.D., M.D., Editor 

Prescriptions for long-acting, high-dose opioids are increasing. However, few large-scale studies have been conducted to assess the impact of opioid dose and opioid-related mortality. A population-based, nested, case-controlled study was conducted in Canada to evaluate patients (N = 607,156) who received an opioid for nonmalignant pain via  publicly funded prescription drug coverage from 1997 to 2006. Of 1,463 opioid-related deaths overall, 498 met the inclusion criteria and were matched to at least 1 control. There was a significant relationship between increasing daily opioid dose and opioid-related mortality. Average daily dose of at least 200 mg morphine (or equivalent) was associated with a threefold increase in the risk of opioid-related mortality. Patients with opioid-related deaths were more likely to have received antidepressants, benzodiazepines, methadone, or psychotropic drugs; have a history of alcoholism; or have obtained opioids from multiple physicians and pharmacies compared with matched controls.

This large population study identified a large number of opioid-related deaths and confirms the strong association between average daily dose of opioid prescribed and opioid-related mortality identified by smaller data set studies. The accompanying editorial emphasizes the importance of frequent and intense monitoring of patients receiving high-dose opioids.

The rate of unintentional opioid overdose death in the United States increased by 124% between 1999 and 2007. A case-cohort study was conducted by the Veterans Health Administration to examine the association between opioid prescribing (i.e. , dose and schedule) and the risk of opioid overdose deaths in patients with cancer, chronic pain, acute pain, or substance use disorders. The overall rate of overdose was estimated to be 0.04%. The risk of death increased with increasing daily dose prescribed (see fig. below ).

This Veterans Health Administration study found doses of opioids greater than 50 mg/day were associated with opioid overdose. Surprisingly, patients treated with as-needed opioids were not at greater risk for opioid overdose than were those treated with no additional as-needed medication. Opioid overdose-related death generally was rare.

Chronic widespread pain (CWP) is a high-incidence, disabling disease with an unknown etiology. The current study is the first to prospectively examine the relationship between the type of traumatic event and the onset of CWP. A case-control study, nested within a large prospective cohort, was conducted to follow up patients for 4 yr and determine the onset of CWP after physically traumatic events. Of 2,069 patients followed up for 4 yr, 11.6% reported CWP. Patients with new-onset CWP were one-third more likely to report a traumatic event between baseline and CWP onset (odds ratio [OR]= 1.34). However, this association was not significant after controlling for baseline psychologic variables and sleep problems (OR = 1.01). Patients who experienced a road traffic accident experienced an 84% increase in the likelihood of CWP, after adjusting for baseline variables.

In this prospective study, some patients with new-onset CWP reported a traumatic event initiating the syndrome. Road traffic accident had the strongest association with new CWP. These data suggest that certain patients may be susceptible to traumatic events and experience CWP.