Anesthesia Literature Review

J. Lance Lichtor, M.D., Editor 

Multiple groups have established guidelines for volume-based referrals for specific surgical procedures. This retrospective study of Medicare data from 1999 to 2008 is the first to examine the associations between mortality and high-volume hospitals since this change has occurred. Hospital volumes increased substantially for four cancer procedures and abdominal aortic aneurysm repair, but decreased sharply for coronary artery bypass grafting and carotid endarterectomy. Operative mortality declined for all eight procedures examined, with the largest decline being 36% for abdominal aortic aneurysm. For pancreatectomy (67% decline), cystectomy (37%), and esophagectomy (32%), higher hospital volumes contributed to the large portion of the decline in mortality.

Is operative mortality a function of hospital volume? In this retrospective analysis of national Medicare data of eight procedures, pancreatectomy, esophagectomy, and cystectomy procedures showed a strong relationship between volume and outcome. For cardiovascular procedures, e.g. , coronary artery bypass grafting, risk-adjusted mortality decreased although the role of hospital volume had little effect.

The mortality rate for colectomy can be as high as 6%. Multiple factors have been implicated in previous studies. This retrospective study of the Nationwide Inpatient Sample database evaluated individual predictors of increased mortality after laparoscopic and open colectomy using multivariate logistic regression analysis. Over a 5-yr period 1,314,696 patients underwent colectomy; 93% of these procedures were open. Age, sex, economic status, and procedure approach were significantly associated with increased mortality rates (P < 0.001; see fig. on this page ).

Using the Nationwide Inpatient Sample database between 2002 and 2007, multivariate analysis showed that mortality after colon resection was higher for older patients, males, those with lower socioeconomic status or different comorbidities, those undergoing emergency surgery, and those transferred from another facility. Those undergoing a laparoscopic rather than an open approach had reduced mortality.

The National Institute for Health and Clinical Evidence (NICE) in the United Kingdom recommended the cessation of antibiotic prophylaxis for all patients at risk for infective endocarditis undergoing dental or other procedures because of a dearth of scientific evidence supporting its use. The current study evaluated all patients between 2000 and 2010 admitted to a hospital in England with a diagnosis of subacute infective endocarditis before and after implementation of the NICE guidelines. There was a significant 78.6% reduction in the number of antibiotic prophylaxis proscribed (P < 0.001) in the absence of any change in incidence of infective endocarditis (P = 0.61).

Guidelines for antibiotic prophylaxis in patients at risk for infective endocarditis have been changing. In the United Kingdom, since March 2008, antibiotic prophylaxis is not recommended for at-risk patients undergoing many invasive procedures. In this study, the authors found that after the new guidelines were published a rapid decrease in the prescription for antibiotic prophylaxis occurred; more importantly, there was no significant increase in infectious endocarditis cases. This study supports the NICE guidelines.

Jean Mantz, M.D., Ph.D., Editor 

Sedation is commonly used in patients in the intensive care unit; however, the ideal sedative with minimum complications has not yet been determined. This randomized controlled trial compared the safety and efficacy of inhaled sevoflurane to intravenous sedation with propofol or midazolam in patients (n = 47) in the intensive care unit. Patients in the sevoflurane group (18.6 min) had significantly (P < 0.001) shorter wake-up times compared with patients in the propofol (91.3 min) or midazolam (260.2 min) groups. Extubation delay was also significantly shorter for patients in the sevoflurane group (33.6 min) (P < 0.001) compared with those in the propofol (326.11 min) or midazolam (599.6 min) groups.

This study tells us that sedation using low end-tidal concentrations of sevoflurane may represent a safe and effective procedure for patients in the intensive care unit undergoing mechanical ventilation for 24–96 h. Beyond decreasing ventilation time and increasing awakening quality, it also significantly reduced agitation, which may be beneficial for long-term cognitive function in these patients. These preliminary data obtained from a restricted sample need confirmation in larger prospective trials.

Fluid resuscitation in pediatric patients in shock is supported by multiple guidelines. However, limited data are available supporting the exact criteria and type of fluid interventions to be given. This two-stratum, multicenter, open, randomized controlled trial was conducted in Africa to compare the outcomes of children (n = 3,141) after early resuscitation with 20–40 ml bolus of saline (0.9%) or albumin bolus (5%), or no fluid bolus at all. Children who received any bolus had a significantly higher mortality rate compared with control subjects at both 48 h and 4 weeks (relative risk of 1.45 for any bolus vs.  control; P = 0.003; see fig. on this page ). Baseline status, including malaria status and clinical severity, was similar across groups.

This randomized controlled trial demonstrates that African children receiving a saline or 5% albumin bolus at the early stage of nonhypotensive septic shock exhibit a higher mortality rate than control subjects without fluid bolus resuscitation. Fluid bolus may inhibit the protective effects of splanchnic vessel constriction observed at the early stage of severe sepsis or contribute to reperfusion injury. Although the explanation of this phenomenon may be multifactorial, including specific features of this patient population (e.g. , a high rate of malaria), this article challenges the use of a fluid bolus as an early resuscitation maneuver in this context. These results may have an important impact on health care in children these resource-limited settings in Africa.

Despite the morbidity and mortality associated with acute respiratory distress syndrome, there are few known treatments and preventive therapies to reduce it. A cross-sectional prospective cohort study was conducted to determine whether prehospital statin use would improve outcomes of critically ill patients (n = 575). Multivariate analysis demonstrated that during the first 4 days in the intensive care unit, patients on statin therapy before hospitalization were less likely to develop severe sepsis (odds ratio = 0.62) or acute lung injury/acute respiratory distress syndrome (odds ratio = 0.60). Mortality rates, ventilator-free days, and length of intensive care unit and hospital stays were similar among groups. Aspirin use alone was not associated with improved clinical outcomes. However, patients taking statins and aspirin had the lowest rates of acute lung injury/acute respiratory distress syndrome, severe sepsis, and hospital mortality.

This prospective cohort study suggests that patients admitted to the intensive care unit treated with chronic statins developed fewer intensive care unit-acute respiratory distress syndrome episodes than those who were not. However, mortality was not affected by statin treatment. Interestingly, the association of aspirin plus statin use offered the largest protection against the development of acute lung injury and mortality.

Mechanical ventilation or organ dysfunction may contribute to worse outcomes for critically ill patients. A secondary analysis of a prospective, observational, multicenter study was conducted to assess the characteristics and outcomes of mechanically ventilated patients with various types of neurologic injuries (n = 362) and those without neurologic injuries (n = 4,030). Mortality was significantly higher in patients with stroke (45%) in comparison with those with brain trauma (29%) or nonneurologic disease (30%). Organ failure occurred significantly more frequently in the nonneurologic group compared with the neurologic group (respiratory and hematologic failures, P < 0.001; cardiovascular, renal, and hepatic, P < 0.05).

This prospective, international, multicenter cohort study emphasizes the severe prognosis of mechanically ventilated patients admitted to the intensive care unit for neurologic purposes. Stroke represents a particularly life-threatening condition. Mortality among neurologic patients was significantly higher than among patients without neurologic injuries, despite fewer organ failures. These data should encourage active therapy for secondary prevention and early management of stroke in the general population.

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

In patients with chronic low back pain, previous studies have demonstrated that rehabilitation may be as effective as spinal fusion, which in turn may be as effective as disc prosthesis. However, this prospective randomized multicenter study is the first to compare the efficacy of disc prosthesis versus  a rehabilitation program directly in patients (n = 173) with low back pain. There was a mean difference in the Oswestry Disability Index of −8.4 points in favor of surgery at 2-yr follow up; however, this score was below the clinically meaningful benefit level. Secondary outcomes also tended to favor surgery for low back pain, such as the patients' satisfaction (24% difference), Short Form-36 Health Survey physical component score (5.8 difference), self-efficacy for pain (1.0 difference), and the Prolo scale (0.9 difference).

Lumbar intervertebral disc replacement compared with rehabilitation slightly improved the disability score 2 yr later. However, the average reduction in Oswestry Disability Index was judged not to be clinically meaningful. A rehabilitation program may provide an effective nonsurgical option to patients with low back pain, but additional studies are warranted.

The efficacy of lumbar epidural steroid injections for patients with radiculopathy and herniated nucleus pulposus is still unclear. This single-center, prospective study was conducted to determine the predictive value of a novel complex of fibronectin and aggrecan in patients (n = 26) undergoing epidural steroid injection for radiculopathy from herniated nucleus pulposus. Lavage fluid taken immediately before epidural steroid injection was assayed for the fibronectin-aggrecan complex. There was a significantly greater improvement overall after epidural steroid injection and in the physical component summary score (PCS) of the Short Form-36 Health Survey in patients with the complex compared with those without (P < 0.001; see fig. on this page ). Age, sex, laterality, lumbar spinal level, and payer type did not contribute to the observed differences.

The current study demonstrates the fibronectin-aggrecan complex in epidural lavage fluid of patients with herniated nucleus pulposus and radiculopathy predicts a clinically significant response to the epidural steroid injection. The molecular fibronectin/aggrecan complex may serve as a biomarker for patients likely to respond epidural steroid injection.