Michelle Morris

Prevention of intraoperative awareness with explicit recall in an unselected surgical population: a randomized comparative effectiveness trial.

Background:Intraoperative awareness with explicit recall occurs in approximately 0.15% of all surgical cases. Efficacy trials based on the Bispectral Index® (BIS) monitor (Covidien, Boulder, CO) and anesthetic concentrations have focused on high-risk patients, but there are no effectiveness data applicable to an unselected surgical population. Methods:We conducted a randomized controlled trial of unselected surgical patients at three hospitals of a tertiary academic medical center. Surgical cases were randomized to alerting algorithms based on either BIS values or anesthetic concentrations. The primary outcome was the incidence of definite intraoperative awareness; prespecified secondary outcomes included postanesthetic recovery variables. Results:The study was terminated because of futility. At interim analysis the incidence of definite awareness was 0.12% (11/9,376) (95% CI: 0.07–0.21%) in the anesthetic concentration group and 0.08% (8/9,460) (95% CI: 0.04–0.16%) in the BIS group (P = 0.48). There was no significant difference between the two groups in terms of meeting criteria for recovery room discharge or incidence of nausea and vomiting. By post hoc secondary analysis, the BIS protocol was associated with a 4.7-fold reduction in definite or possible awareness events compared with a cohort receiving no intervention (P = 0.001; 95% CI: 1.7–13.1). Conclusion:This negative trial could not detect a difference in the incidence of definite awareness or recovery variables between monitoring protocols based on either BIS values or anesthetic concentration. By post hoc analysis, a protocol based on BIS monitoring reduced the incidence of definite or possible intraoperative awareness compared with routine care.

Survey Criteria for Fibromyalgia Independently Predict Increased Postoperative Opioid Consumption after Lower Extremity Joint Arthroplasty: A Prospective, Observational Cohort Study

Background:Variance in pain after total knee and hip arthroplasty may be due to a number of procedural and peripheral factors but also, in some individuals, to aberrant central pain processing as is described in conditions like fibromyalgia. To test this hypothesis, the authors conducted a prospective, observational cohort study of patients undergoing lower-extremity joint arthroplasty. Methods:Five hundred nineteen patients were preoperatively phenotyped using validated self-reported pain questionnaires, psychological measures, and health information. In addition to being assessed for factors previously found to be associated with poor outcomes in arthroplasty, participants also completed the American College of Rheumatology survey criteria for fibromyalgia. Previous studies have suggested that rather than being “present” or “absent,” features of fibromyalgia as measured by this instrument, occur over a wide continuum. Postoperative pain control was assessed by total postoperative opioid consumption. Results:Preoperatively, patients with higher fibromyalgia survey scores were younger, more likely to be female, taking more opioids, reported higher pain severity, and had a more negative psychological profile. In the multivariate analysis, the fibromyalgia survey score, younger age, preoperative opioid use, knee (vs. hip), pain severity at baseline, and the anesthetic technique were all predictive of increased postoperative opioid consumption. Conclusions:The use of the survey criteria for fibromyalgia led to the finding of distinct phenotypic differences, and the measure was independently predictive of opioid consumption. This self-report measure may provide an additional simple means of predicting postoperative pain outcomes and analgesic requirements. Future studies are needed to determine whether tailored therapies can improve postoperative pain control in this population.

Life-threatening critical respiratory events: a retrospective study of postoperative patients found unresponsive during analgesic therapy

STUDY OBJECTIVE To identify risk factors for life-threatening critical respiratory events occurring during parenteral analgesic therapy for acute postoperative pain. DESIGN Retrospective, observational, cohort study. SETTING University hospital. MEASUREMENTS The electronic records of patients with sudden-onset, life-threatening critical respiratory events during analgesic therapy for postoperative pain were studied. Critical respiratory event data were identified from the hospital risk management database between 8/1/2000 and 7/31//2007. Patients required rescue treatment with naloxone, endototracheal intubation, or cardiopulmonary resusucitation. Pediatric patients were excluded from the study. In addition to the event description (type of analgesia, opioid dose, patient monitoring data, time of day, and time from surgery), each patients record was reviewed to extract co-morbidities and outcome data. MAIN RESULTS Over the 6-year period, 32 patients experienced a postoperative critical respiratory event. Twenty-six events and three deaths occurred within the first 24 hours of opioid therapy. Four of 32 patients died. Congestive heart failure, postoperative acute renal failure, obstructive sleep apnea, cardiac dysrhythmia, diabetes mellitus, coronary artery disease, and hypertension were significant associations in adult patients. CONCLUSIONS The first 24 hours after commencing opioid-based analgesic therapy represents a high risk period. Obstructive sleep apnea, deep levels of sedation, nocturnal presentation, and postoperative acute renal failure were seen in patients who died as a result of these critical respiratory events.

Derivation and validation of a simple perioperative sleep apnea prediction score

BACKGROUND:Obstructive sleep apnea (OSA) is a largely underdiagnosed, common condition, which is important to diagnose preoperatively because it has implications for perioperative management. Our purpose in this study was to identify independent clinical predictors of a diagnosis of OSA in a general surgical population, develop a perioperative sleep apnea prediction (P-SAP) score based on these variables, and validate the P-SAP score against standard overnight polysomnography. METHODS:A retrospective, observational study was designed to identify patients with a known diagnosis of OSA. Independent predictors of a diagnosis of OSA were derived by logistic regression, based on which prediction tool (P-SAP score) was developed. The P-SAP score was then validated in patients undergoing overnight polysomnography. RESULTS:The P-SAP score was derived from 43,576 adult cases undergoing anesthesia. Of these, 3884 patients (7.17%) had a documented diagnosis of OSA. Three demographic variables: age >43 years, male gender, and obesity; 3 history variables: history of snoring, diabetes mellitus Type 2, and hypertension; and 3 airway measures: thick neck, modified Mallampati class 3 or 4, and reduced thyromental distance were identified as independent predictors of a diagnosis of OSA. A diagnostic threshold P-SAP score ≥2 showed excellent sensitivity (0.939) but poor specificity (0.323), whereas for a P-SAP score ≥6, sensitivity was poor (0.239) with excellent specificity (0.911). Validation of this P-SAP score was performed in 512 patients with similar accuracy. CONCLUSION:The P-SAP score predicts diagnosis of OSA with dependable accuracy across mild to severe disease. The elements of the P-SAP score are derived from a typical university hospital surgical population.

How do pediatric anesthesiologists define intraoperative hypotension

Introduction:  Although blood pressure (BP) monitoring is a recommended standard of care by the ASA, and pediatric anesthesiologists routinely monitor the BP of their patients and when appropriate treat deviations from ‘normal’, there is no robust definition of hypotension in any of the pediatric anesthesia texts or journals. Consequently, what constitutes hypotension in pediatric anesthesia is currently unknown. We designed a questionnaire‐based survey of pediatric anesthesiologists to determine the BP ranges and thresholds used to define intraoperative hypotension (IOH).

Obesity and risk of peri-operative complications in children presenting for adenotonsillectomy

BACKGROUND Adenotonsillectomy (T&A) is a very common surgical procedure in children. With the rising prevalence of childhood overweight and obesity, our goal was to describe the prevalence of overweight/obesity in children presenting for T&A in our institution. We also sought to compare the frequency of peri-operative complications and the likelihood of being admitted following T&A between overweight/obese and normal weight children. METHODS We examined our peri-operative database and extracted clinical, demographic and anthropometric information on 2170 children who underwent T&A between January 2005 and February 2008. Children were classified into normal weight, overweight and obese using published body mass index (BMI) criteria. The incidences of peri-operative complications were compared between the BMI categories. We also examined factors contributing to the likelihood of admission following T&A. RESULTS The overall prevalence of overweight and obese was 20.7%. Overweight/obese children were more likely to have intra-operative desaturation (p=0.004), multiple attempts at laryngoscopy (p<0.001), difficult mask ventilation (p=0.001), and post-induction and post-anesthesia care unit (PACU) upper airway obstruction (p<0.001). Additionally, overweight and obese children were more likely to be admitted following T&A. BMI showed a moderate positive correlation with post-operative length of stay (LOS). Multiple logistic regression analysis showed that BMI and presence of medical co-morbidities were independent predictors of LOS. CONCLUSION Overweight and obese children presenting for T&A have a higher incidence of peri-operative complications and are more likely to be admitted and stay for longer than their healthy weight peers.

Patient selection for day case-eligible surgery: identifying those at high risk for major complications.

Background:Due to economic pressures and improvements in perioperative care, outpatient surgical procedures have become commonplace. However, risk factors for outpatient surgical morbidity and mortality remain unclear. There are no multicenter clinical data guiding patient selection for outpatient surgery. The authors hypothesize that specific risk factors increase the likelihood of day case-eligible surgical morbidity or mortality. Methods:The authors analyzed adults undergoing common day case-eligible surgical procedures by using the American College of Surgeons’ National Surgical Quality Improvement Program database from 2005 to 2010. Common day case-eligible surgical procedures were identified as the most common outpatient surgical Current Procedural Terminology codes provided by Blue Cross Blue Shield of Michigan and Medicare publications. Study variables included anthropometric data and relevant medical comorbidities. The primary outcome was morbidity or mortality within 72 h. Intraoperative complications included adverse cardiovascular events; postoperative complications included surgical, anesthetic, and medical adverse events. Results:Of 244,397 surgeries studied, 232 (0.1%) experienced early perioperative morbidity or mortality. Seven independent risk factors were identified while controlling for surgical complexity: overweight body mass index, obese body mass index, chronic obstructive pulmonary disease, history of transient ischemic attack/stroke, hypertension, previous cardiac surgical intervention, and prolonged operative time. Conclusions:The demonstrated low rate of perioperative morbidity and mortality confirms the safety of current day case-eligible surgeries. The authors obtained the first prospectively collected data identifying risk factors for morbidity and mortality with day case-eligible surgery. The results of the study provide new data to advance patient-selection processes for outpatient surgery.

Incidence and risk factors for preincision hypotension in a noncardiac pediatric surgical population

Background:  Routine monitoring of blood pressure is an essential part of perioperative care in adults and children. It is however not known whether intraoperative hypotension (IOH) is clinically important in the ‘healthy’ pediatric patient. This may be partly due to the lack of data on the incidence and consequences of IOH in this group of patients. We utilized the Brain Trauma Foundation definition of hypotension to describe the incidence of preincision hypotension (PIH) in a large pediatric noncardiac surgical population and identified risk factors for the occurrence PIH.

A Description of Intraoperative Ventilator Management in Patients with Acute Lung Injury and the Use of Lung Protective Ventilation Strategies

Background:The incidence of acute lung injury (ALI) in hypoxic patients undergoing surgery is currently unknown. Previous studies have identified lung protective ventilation strategies that are beneficial in the treatment of ALI. The authors sought to determine the incidence and examine the use of lung protective ventilation strategies in patients receiving anesthetics with a known history of ALI. Methods:The ventilation parameters that were used in all patients were reviewed, with an average preoperative Paco2/Fio2 ratio of ≤ 300 between January 1, 2005 and July 1, 2009. This dataset was then merged with a dataset of patients screened for ALI. The median tidal volume, positive end-expiratory pressure, peak inspiratory pressures, fraction inhaled oxygen, oxygen saturation, and tidal volumes were compared between groups. Results:A total of 1,286 patients met criteria for inclusion; 242 had a diagnosis of ALI preoperatively. Comparison of patients with ALI versus those without ALI found statistically yet clinically insignificant differences between the ventilation strategies between the groups in peak inspiratory pressures and positive end-expiratory pressure but no other category. The tidal volumes in cc/kg predicted body weight were approximately 8.7 in both groups. Peak inspiratory pressures were found to be 27.87 cm H2O on average in the non-ALI group and 29.2 in the ALI group. Conclusion:Similar ventilation strategies are used between patients with ALI and those without ALI. These findings suggest that anesthesiologists are not using lung protective ventilation strategies when ventilating patients with low Paco2/Fio2 ratios and ALI, and instead are treating hypoxia and ALI with higher concentrations of oxygen and peak pressures.

A Description of Intraoperative Ventilator Management and Ventilation Strategies in Hypoxic Patients

BACKGROUND: Hypoxia is a common finding in the anesthetized patient. Although there are a variety of methods to address hypoxia, it is not well documented what strategies are used by anesthesiologists when faced with a hypoxic patient. Studies have identified that lung protective ventilation strategies have beneficial effects in both oxygenation and mortality in acute respiratory distress syndrome. We sought to describe the ventilation strategies in anesthetized patients with varying degrees of hypoxemia as defined by the PaO2 to fraction of inspired oxygen (FIO2) (P/F) ratio. METHODS: We conducted a review of all operations performed between January 1, 2005, and July 31, 2009, using a general anesthetic, excluding cardiac and thoracic procedures, to assess the ventilation settings that were used in patients with different P/F ratios. Patients older than 18 years who received a general anesthetic were included. Four cohorts of arterial blood gases (ABGs) were identified with P/F >300, 300 ≥ P/F > 200, 200 ≥ P/F > 100, 100 ≥ P/F. Using the standard predicted body weight (PBW) equation, we calculated the milliliters per kilogram (mL/kg PBW) with which the patients lungs were being ventilated. Positive end-expiratory pressure (PEEP), peak inspiratory pressures (PIPs), FIO2, oxygen saturation (SaO2), and tidal volume in mL/kg PBW were compared. RESULTS: A total of 28,706 ABGs from 11,445 operative cases met criteria for inclusion. There were 19,679 ABGs from the P/F >300 group, 5364 ABGs from the 300 ≥ P/F > 200 group, 3101 ABGs from the 200 ≥ P/F > 100 group, and 562 ABGs from the 100 ≥ P/F group identified. A comparison of ventilation strategies found statistical significance but clinically irrelevant differences. Tidal volumes ranged between 8.64 and 9.16 and the average PEEP varied from 2.5 to 5.5 cm H2O. There were substantial differences in the average FIO2 and PIP among the groups, 59% to 91% and 22 to 29 cm H2O, respectively. CONCLUSION: Similar ventilation strategies in mL/kg PBW and PEEP were used among patients regardless of P/F ratio. The results of this study suggest that anesthesiologists, in general, are treating hypoxemia with higher FIO2 and PIP. The average FIO2 and PIP were significantly escalated depending on the P/F ratio.