Francis X. Whalen

Identification of Patients at Risk for Postoperative Respiratory Complications Using a Preoperative Obstructive Sleep Apnea Screening Tool and Postanesthesia Care Assessment

Background:Patients with obstructive sleep apnea are at risk for perioperative morbidity. The authors used a screening prediction model for obstructive sleep apnea to generate a sleep apnea clinical score (SACS) that identified patients at high or low risk for obstructive sleep apnea. This was combined with postanesthesia care unit (PACU) monitoring with the aim of identifying patients at high risk of postoperative oxygen desaturation and respiratory complications. Methods:In this prospective cohort study, surgical patients with a hospital stay longer than 48 h who consented were enrolled. The SACS (high or low risk) was calculated; all patients were monitored in the PACU for recurrent episodes of bradypnea, apnea, desaturations, and pain–sedation mismatch. All patients underwent pulse oximetry postoperatively; complications were documented. Chi-square, two-sample t test, and logistic regression were used for analysis. The oxygen desaturation index (number of desaturations per hour) was calculated. Oxygen desaturation index and incidence of postoperative cardiorespiratory complications were primary endpoints. Results:Six hundred ninety-three patients were enrolled. From multivariable logistic regression analysis, the likelihood of a postoperative oxygen desaturation index greater than 10 was increased with a high SACS (odds ratio = 1.9, P < 0.001) and recurrent PACU events (odds ratio = 1.5, P = 0.036). Postoperative respiratory events were also associated with a high SACS (odds ratio = 3.5, P < 0.001) and recurrent PACU events (odds ratio = 21.0, P < 0.001). Conclusions:Combination of an obstructive sleep apnea screening tool preoperatively (SACS) and recurrent PACU respiratory events was associated with a higher oxygen desaturation index and postoperative respiratory complications. A two-phase process to identify patients at higher risk for perioperative respiratory desaturations and complications may be useful to stratify and manage surgical patients postoperatively.

The effects of the alveolar recruitment maneuver and positive end-expiratory pressure on arterial oxygenation during laparoscopic bariatric surgery.

Abnormalities in gas exchange that occur during anesthesia are mostly caused by atelectasis, and these alterations are more pronounced in morbidly obese than in normal weight subjects. Sustained lung insufflation is capable of recruiting the collapsed areas and improving oxygenation in healthy patients of normal weight. We tested the effect of this ventilatory strategy on arterial oxygenation (Pao2) in patients undergoing laparoscopic bariatric surgery. After pneumoperitoneum was accomplished, the recruitment group received up to 4 sustained lung inflations with peak inspiratory pressures up to 50 cm H2O, which was followed by ventilation with 12 cm H2O positive end-expiratory pressure (PEEP). The patients lungs in the control group were ventilated in a standard fashion with PEEP of 4 cm H2O. Variables related to gas exchange, respiratory mechanics, and hemodynamics were compared between recruitment and control groups. We found that alveolar recruitment effectively increased intraoperative Pao2 and temporarily increased respiratory system dynamic compliance (both P < 0.01). The effects of alveolar recruitment on oxygenation lasted as long as the trachea was intubated, and lungs were ventilated with high PEEP, but soon after tracheal extubation, all the beneficial effects on oxygenation disappeared. The mean number of vasopressor treatments given during surgery was larger in the recruitment group compared with the control group (3.0 versus 0.8; P = 0.04). In conclusion, our data suggest that the use of alveolar recruitment may be an effective mode of improving intraoperative oxygenation in morbidly obese patients. Our results showed the effect to be short lived and associated with more frequent intraoperative use of vasopressors.

Evidence-based red cell transfusion in the critically ill: Quality improvement using computerized physician order entry

Objective:The implementation of evidence-based practice poses a significant challenge in the intensive care unit. In this quality improvement intervention we assessed the effect of an institutional protocol and computerized decision support for red cell transfusion in the critically ill. Design:We compared processes of care and outcomes during the two 3-month periods before and after the introduction of a multidisciplinary quality improvement intervention. Setting:Multidisciplinary intensive care units—medical, surgical, and mixed—in a tertiary academic center. Patients:Consecutive critically ill patients with anemia (hemoglobin of <10 g/dL). Intervention:Using the computerized provider order entry, we developed an evidence-based decision algorithm for red cell transfusion in adult intensive care units. Measurements and Main Results:We collected information on demographics, diagnosis, severity of illness, transfusion complications, and laboratory values. The main outcome measures were number of transfusions, proportion of patients who were transfused outside evidence-based indications, transfusion complications, and adjusted hospital mortality. The mean number of red cell transfusions per intensive care unit admission decreased from 1.08 ± 2.3 units before to 0.86 ± 2.3 units after the protocol (p<.001). We observed a marked decrease in the percentage of patients receiving inappropriate transfusions (17.7% vs. 4.5%, p< .001). The rate of transfusion complications was also lower in the period after the protocol (6.1% vs. 2.7%, p = .015). In the multivariate analysis, protocol introduction was associated with decreased likelihood of red cell transfusion (odds ratio, 0.43; 95% confidence interval, 0.30 to 0.62). Adjusted hospital mortality did not differ before and after protocol implementation (odds ratio, 1.12; 95% confidence interval, 0.69 to 1.8). Conclusions:The implementation of an institutional protocol and decision support through a computerized provider order entry effectively decreased inappropriate red cell transfusions.

A prospective trial of elective extubation in brain injured patients meeting extubation criteria for ventilatory support: A feasibility study

IntroductionTo assess the safety and feasibility of recruiting mechanically ventilated patients with brain injury who are solely intubated for airway protection and randomising them into early or delayed extubation, and to obtain estimates to refine sample-size calculations for a larger study. The design is a single-blinded block randomised controlled trial. A single large academic medical centre is the setting.MethodsSixteen neurologically stable but severely brain injured patients with a Glasgow Coma Score (GCS) of 8 or less were randomised to early or delayed extubation until their neurological examination improved. Eligible patients met standard respiratory criteria for extubation and passed a modified Airway Care Score (ACS) to ensure adequate control of respiratory secretions. The primary outcome measured between groups was the functional status of the patient at hospital discharge as measured by a Modified Rankin Score (MRS) and Functional Independence Measure (FIM). Secondary measurements included the number of nosocomial pneumonias and re-intubations, and intensive care unit (ICU) and hospital length of stay. Standard statistical assessments were employed for analysis.ResultsFive female and eleven male patients ranging in age from 30 to 93 years were enrolled. Aetiologies responsible for the neurological injury included six head traumas, three brain tumours, two intracerebral haemorrhages, two subarachnoid haemorrhages and three ischaemic strokes. There were no demographic differences between the groups. There were no unexpected deaths and no significant differences in secondary measures. The difference in means between the MRS and FIM were small (0.25 and 5.62, respectively). These results suggest that between 64 and 110 patients are needed in each treatment arm to detect a treatment effect with 80% power.ConclusionsRecruitment and randomisation of severely brain injured patients appears to be safe and feasible. A large multicentre trial will be needed to determine if stable, severely brain injured patients who meet respiratory and airway control criteria for extubation need to remain intubated.

Perioperative Statin Therapy and Renal Outcomes After Major Vascular Surgery: A Propensity-Based Analysis

OBJECTIVE To evaluate how the presence and timing of statin therapy affect perioperative renal outcomes after major vascular surgery. DESIGN Retrospective cohort study. SETTING Surgical intensive care unit at a single academic medical center. PARTICIPANTS Patients undergoing major vascular surgery between July 2004 and October 2005. MEASUREMENTS AND MAIN RESULTS The presence and timing of perioperative statin administration and the propensity for receiving such therapy were noted. Renal outcomes, lengths of stay, and mortality were reviewed. One hundred fifty-one procedures were performed. Eighty-nine patients (59%) received statin therapy. There was no evidence for renal protection with perioperative statin therapy (Delta creatinine 0.2 mg/dL v 0.2 mg/dL, p = 0.41; acute renal injury/acute renal failure 8% v 6%, p = 1.00; renal replacement therapy 3% v 3%, p = 1.00; all statin v no statin, respectively). With the possible exception of early reinstitution of statin therapy in chronic statin users, subgroup analyses failed to confirm an association between statin timing and prevention of postoperative renal dysfunction. CONCLUSIONS In the present investigation, neither the presence nor timing of perioperative statin therapy was associated with improved renal outcomes in patients undergoing a range of major vascular procedures. A possible exception is early postoperative reinitiation of statin therapy in chronic statin users. The discrepant results of available literature preclude a definitive statement on the use of statin therapy as a means of preventing postoperative renal dysfunction. An adequately powered prospective trial is needed before advocating the routine use of statin therapy for perioperative renal protection.

Postoperative Emergency Response Team Activation at a Large Tertiary Medical Center

OBJECTIVE To study characteristics and outcomes associated with emergency response team (ERT) activation in postsurgical patients discharged to regular wards after anesthesia. PATIENTS AND METHODS We identified all ERT activations that occurred within 48 hours after surgery from June 1, 2008, through December 31, 2009, in patients discharged from the postanesthesia care unit to regular wards. For each ERT case, up to 2 controls matched for age (±10 years), sex, and type of procedure were identified. A chart review was performed to identify factors that may be associated with ERT activation. RESULTS We identified 181 postoperative ERT calls, 113 (62%) of which occurred within 12 hours of discharge from the postanesthesia care unit, for an incidence of 2 per 1000 anesthetic administrations (0.2%). Multiple logistic regression analysis revealed the following factors to be associated with increased odds for postoperative ERT activation: preoperative central nervous system comorbidity (odds ratio [OR], 2.53; 95% confidence interval [CI], 1.20-5.32; P=.01), preoperative opioid use (OR, 2.00; 95% CI, 1.30-3.10; P=.002), intraoperative use of phenylephrine infusion (OR, 3.05; 95% CI, 1.08-8.66; P=.04), and increased intraoperative fluid administration (per 500-mL increase, OR, 1.06; 95% CI, 1.01-1.12; P=.03). ERT patients had longer hospital stays, higher complication rates, and increased 30-day mortality compared with controls. CONCLUSION Preoperative opioid use, history of central neurologic disease, and intraoperative hemodynamic instability are associated with postoperative decompensation requiring ERT intervention. Patients with these clinical characteristics may benefit from discharge to progressive or intensive care units in the early postoperative period.

Alveolar recruitment and arterial desflurane concentration during bariatric surgery.

BACKGROUND: We investigated whether reversal of intraoperative atelectasis with the lung recruitment maneuver (RM) affects desflurane arterial concentrations during bariatric surgery. METHODS: After anesthetic induction and maintenance with propofol, patients were randomized to receive alveolar RM at intervals (RM group) or not (controls). Desflurane 6% was initiated, and rate of increase of alveolar desflurane concentration (ratio of end-expiratory to inspiratory concentrations, FA/FI) and desflurane blood concentrations were measured in both groups. Blood and end-tidal desflurane concentrations were also measured after the discontinuation of anesthesia. RESULTS: The RM group had higher intraoperative Pao2/Fio2 compared with the control group (both, P < 0.001). During induction, the rate of increase in blood desflurane concentrations was rapid in both groups. At comparable mechanical ventilation settings, median times to achieve 0.5 mM (approximately 3%) were 2.1 and 1.59 min (P = 0.09) in the control and RM group, respectively. The times to achieve 0.7 mM (approximately 4.2%) desflurane were 15.9 and 9.3 min in the control and RM group, respectively (P = 0.08). Desflurane blood concentrations tended to be higher during the first 30 min after induction in the RM group (P = 0.066). During maintenance or emergence, the blood desflurane concentrations were not different between control and RM groups. Consequently, the time to eye opening did not differ between groups. CONCLUSION: Although the RM during bariatric surgery represents an effective method for improving intraoperative oxygenation, it does not significantly affect the desflurane blood concentrations during anesthesia or its elimination during emergence.

Prolonged coma from refractory status epilepticus

ObjectiveStatus epilepticus is a life-threatening medical condition. In its most severe form, refractory status epilepticus (RSE) seizures may not respond to first and second-line anti-epileptic drugs. RSE is associated with a high mortality and significant medical complications in survivors with prolonged hospitalizations.MethodsWe describe the clinical course of RSE in the setting of new onset lupus in a 31-year-old male who required prolonged barbiturate coma.ResultsSeizure stopped on day 64 of treatment. Prior to the resolution of seizures, discussion around withdrawal of care took place between the physicians and patients family. Medical care was continued because of the patients age, normal serial MRI studies, and the patients reversible medical condition.ConclusionFew evidence-based data exist to guide management of RSE. Our case emphasizes the need for continuous aggressive therapy when neuroimaging remains normal.

Recent smoking behavior and postoperative nausea and vomiting

The risk of postoperative nausea and vomiting (PONV) is reduced in cigarette smokers by unknown mechanisms. If protection is related to an acute effect of smoke constituents, smokers with the most recent exposure to cigarette smoke would be most protected. We tested the hypothesis that in cigarette smokers, postoperative nausea is correlated with recent exposure to cigarette smoke as quantified by exhaled carbon monoxide (CO) concentrations. In this observational study, exhaled CO levels were measured in 140 female smokers preoperatively. PONV was assessed over the first 24 h after surgery. There was no correlation (assessed with Spearman rank correlation) between preoperative CO and nausea scores at recovery room discharge. Significant correlations were found between nausea assessed over the first 24 h postoperatively and a history of PONV or motion sickness, the use of intraoperative antiemetic prophylaxis, duration of anesthesia, and use of opioids in the postanesthesia care unit. However, there was no correlation between preoperative CO and nausea over the first 24 h. These preliminary data suggest that the effect of smoking in reduced PONV is not directly related to preoperative exhaled CO levels.

Propofol induction resulting in green urine discoloration.

A 54-YR-OLD woman with intractable leg pain secondary to lumbar stenosis elected to undergo L4–L5 decompressive laminectomy. General anesthesia was induced with fentanyl, lidocaine, and propofol (200 mg) and maintained with isoflurane and nitrous oxide. Tracheal intubation was facilitated with succinylcholine, and neuromuscular blockade was maintained with vecuronium. Within the first hour of the surgery, without any additional medications administered besides vancomycin, the urine color changed from yellow to green. The discoloration then resolved by the end of the 2.5-h operation. The patient was discharged home 2 days later without complication. An uncommon side effect of propofol is green urine discoloration, which is reported most frequently after prolonged infusions. The 4-sulfate and 1or 4-glucuronide conjugates of 2,6-diisopropyl-1,4-quinol are renally excreted and may rarely result in green urine discoloration, as seen in this case. Alkalinization of the urine favors the formation of these phenolic metabolites. In addition, several colors of urine have been reported with propofol use, including pink, white, red, and brown. Other causes of green urine discoloration include obstructive jaundice, Pseudomonas infection, Hartnup disease (abnormal amino acid transport), indicanuria, triamterene, amitriptyline, indomethacin, methocarbamol, promethazine, cimetidine, food coloring, Listerine mouthwash, Clorets mints, indigo dyes, and methylene blue. (Our patient was taking none of these medications). This case demonstrates the pronounced urine discoloration that may occur after a single induction dose of propofol in a patient undergoing elective surgery. The transient presence of green urine that resolves after propofol discontinuation is benign and self-limited. Unnecessary testing should be avoided.