Bhargavi Gali

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.

Anesthetic, patient, and surgical risk factors for neurologic complications after prolonged total tourniquet time during total knee arthroplasty

Nerve injury after prolonged tourniquet inflation results from the combined effects of ischemia and mechanical trauma. Tourniquet release, allowing a reperfusion interval of 10–30 min followed by re-inflation, has been recommended to extend the duration of total tourniquet time. However, this practice has not been confirmed clinically. We retrospectively reviewed the medical records of 1001 patients undergoing 1166 primary or revision knee replacements with tourniquet time more than 120 min during a 5-yr interval. Mean total tourniquet time was 145 ± 25 min (range, 120–308 min). In 759 patients, the tourniquet inflation was uninterrupted. Two tourniquet inflations, interrupted by a single deflation, were noted in 371 patients, and 3 tourniquet inflations interrupted by 2 deflation intervals were noted in 23 patients. A total of 129 neurologic complications (peroneal and/or tibial nerve palsies) were noted in 90 patients for an overall incidence of 7.7%. Eighty-five cases involved the peroneal nerve and 44 cases involved the tibial nerve. In 39 cases, both peroneal and tibial deficits were noted. Complete neurologic recovery occurred in 76 (89%) peroneal and 44 (100%) tibial palsies. Postoperative neurologic dysfunction was associated with younger age (P < 0.001; odds ratio = 0.7 per 10-yr increase), longer tourniquet time (P < 0.001; odds ratio = 2.8 per 30-min increase), and preoperative flexion contracture >20° (P = 0.002; odds ratio = 3.9). In a subset of 116 patients with tourniquet times ≥180 min, longer duration of deflation was associated with a decreased frequency of neurologic complications (P = 0.048). We conclude that the likelihood of neurologic dysfunction increases with total tourniquet time and that a reperfusion interval only modestly decreases the risk of nerve injury.

Society of Anesthesia and Sleep Medicine Guidelines on Preoperative Screening and Assessment of Adult Patients with Obstructive Sleep Apnea

The purpose of the Society of Anesthesia and Sleep Medicine guideline on preoperative screening and assessment of adult patients with obstructive sleep apnea (OSA) is to present recommendations based on the available clinical evidence on the topic where possible. As very few well-performed randomized studies in this field of perioperative care are available, most of the recommendations were developed by experts in the field through consensus processes involving utilization of evidence grading to indicate the level of evidence upon which recommendations were based. This guideline may not be appropriate for all clinical situations and all patients. The decision whether to follow these recommendations must be made by a responsible physician on an individual basis. Protocols should be developed by individual institutions taking into account the patients’ conditions, extent of interventions and available resources. This practice guideline is not intended to define standards of care or represent absolute requirements for patient care. The adherence to these guidelines cannot in any way guarantee successful outcomes and is rather meant to help individuals and institutions formulate plans to better deal with the challenges posed by perioperative patients with OSA. These recommendations reflect the current state of knowledge and its interpretation by a group of experts in the field at the time of publication. While these guidelines will be periodically updated, new information that becomes available between updates should be taken into account. Deviations in practice from guidelines may be justifiable and such deviations should not be interpreted as a basis for claims of negligence.

Predictors of Delayed Postoperative Respiratory Depression Assessed From Naloxone Administration

BACKGROUND:The aim of this study was to identify patient and procedural characteristics associated with postoperative respiratory depression or sedation requiring naloxone intervention. METHODS:We identified patients who received naloxone to reverse opioid-induced respiratory depression or sedation within 48 hours after discharge from anesthetic care (transfer from the postanesthesia care unit or transfer from the operating room to postoperative areas) between July 1, 2008, and June 30, 2010. Patients were matched to 2 control subjects based on age, sex, and exact type of procedure performed during the same year. A chart review was performed to identify patient, anesthetic, and surgical factors that may be associated with risk for intervention requiring naloxone. In addition, we identified all patients who developed adverse respiratory events (hypoventilation, apnea, oxyhemoglobin desaturation, pain/sedation mismatch) during phase 1 anesthesia recovery. We performed conditional logistic regression taking into account the 1:2 matched set case–control study design to assess patient and procedural characteristics associated with naloxone use. RESULTS:We identified 134 naloxone administrations, 58% within 12 hours of discharge from anesthesia care, with an incidence of 1.6 per 1000 (95% confidence interval [CI], 1.3–1.9) anesthetics. The presence of obstructive sleep apnea (odds ratio [OR] = 2.45; 95% CI, 1.27–4.66; P = 0.008) and diagnosis of an adverse respiratory event in the postanesthesia recovery room (OR = 5.11; 95% CI, 2.32–11.27; P < 0.001) were associated with an increased risk for requiring naloxone to treat respiratory depression or sedation after discharge from anesthesia care. After discharge from anesthesia care, patients administered naloxone used a greater median dose of opioids (10 [interquartile range, 0–47.1] vs 5 [0–24.8] IV morphine equivalents, P = 0.020) and more medications with sedating side effects (n = 41 [31%] vs 24 [9%]; P < 0.001). CONCLUSIONS:Obstructive sleep apnea and adverse respiratory events in the recovery room are harbingers of increased risk for respiratory depression or sedation requiring naloxone after discharge from anesthesia care. Also, patients administered naloxone received more opioids and other sedating medications after discharge from anesthetic care. Our findings suggest that these patients may benefit from more careful monitoring after being discharged from anesthesia care.

Vasotrac arterial blood pressure and direct arterial blood pressure monitoring during liver transplantation.

During liver transplantation two arterial catheters are often placed. The Vasotrac® is a noninvasive monitor that provides radial arterial blood pressures by a tonometric method. We investigated whether the Vasotrac® would be an accurate substitute for an arterial catheter by comparing Vasotrac® blood pressures with simultaneous direct radial blood pressures recorded from the contralateral arm in 14 patients undergoing liver transplantation. Correlation between the two methods was calculated and a Bland-Altman analysis performed to assess agreement. A total of 6468 simultaneous measurements were made over a duration of 1.5–7.5 h per case. For mean arterial blood pressure 57% of Vasotrac® measurements were within 10% of direct arterial measurement. Correlation (r) was 0.82. Vasotrac® bias was +5.4 mm Hg and limits of agreement were ±18.6 mm Hg. For systolic arterial blood pressure 65% of Vasotrac® measurements were within 10% of direct arterial measurement. Correlation was 0.78. Vasotrac® bias was +7.6 mm Hg and limits of agreement ±25 mm Hg. For diastolic arterial blood pressure 57% of Vasotrac® measurements were within 10% of direct arterial measurement. Correlation was 0.82. Vasotrac® bias was +3.3 mm Hg and limits of agreement ±15 mm Hg. We conclude that the Vasotrac® is not adequately accurate to substitute for direct arterial blood pressure monitoring in liver transplantation.

Positive pressure mechanical ventilation

There have been numerous advances in the application of positive pressure mechanical ventilation in the last two decades. As knowledge of pulmonary physiology expands, the application of modes and parameters to maximize the efficacy and minimize the complications of ventilatory support continues to advance. As the use of noninvasive ventilation becomes more widespread, its usefulness in certain clinical entities such as COPD exacerbations and acute cardiogenic pulmonary edema will become more prominent. The role of specific modes and parameters of these devices likely will be further refined to maximize outcomes.

Skin injury with the use of a water warming device.

HYPOTHERMIA is common during extensive and prolonged surgery such as a liver transplantation (OLT). Hypothermia can cause or exacerbate preexisting coagulation abnormalities and myocardial dysfunction. Efforts to prevent hypothermia during OLT and other major operations have largely employed active warming devices utilizing forced-air warming. A new device, the Allon System with the ThermoWrap garment (MTRE Advanced Technologies Ltd., Centerville, OH), circulates warmed water through a special garment to prevent hypothermia. We report the case of pressure/burn injury secondary to the use of this device.

Living Donor Liver Transplantation Selection, Perioperative Care, and Outcome

A perception that living donor liver transplantation can be accomplished with an acceptable donor complication rate and recipient survival rate has led to the acceptance of living donor liver transplantation as a viable alternative to decreased deceased donor transplantation. Careful candidate evaluation and selection has been crucial to the success of this procedure. Advancements in the understanding of the lobar nature of the liver and of liver regeneration have advanced the surgical technique. Initial attempts at adult-to-adult donation utilized the left hepatic lobe, but now have evolved into use of the right hepatic lobe. Size matching is very important to successful graft function in the recipient. There is great concern regarding morbidity and mortality in donors. Biliary complications and infections continue to be among the most highly reported complications, although rates vary among centers and countries. Reports of single center complications have ranged from 9% to 67%. A survey of centers in the United States in 2003 reported complications of 10%. A series from our institution reported complications arising in 13 (33%) of 39 patients. A review focused on documenting donor deaths found 33 living liver donor deaths worldwide. The much publicized immediate postoperative mishap of 2002 that resulted in a donor’s death resulted in a drop in the utilization of living donor liver transplantation in the United States, from which this procedure has never fully recovered. The future development and expansion of living donor liver transplantation depends on open communication regarding donor complications and deaths. Close immediate postoperative monitoring and meticulous management will remain an essential aspect in limiting donor complications and deaths.

Predicting postoperative pulmonary complications in high-risk populations

Purpose of review Our objective is to describe prediction models for surgical patients who have suspected obstructive sleep apnea (OSA) at risk for postoperative respiratory complications and for surgical patients at risk for postoperative acute respiratory distress syndrome (ARDS). Recent findings Because of the increased rate of severe perioperative respiratory complications in patients with OSA, the American Society of Anesthesiologists issued practice guidelines for perioperative management. When OSA is diagnosed preoperatively, the rate of postoperative pulmonary complications is low and not associated with OSA severity. However, OSA continues to be an important risk because a substantial proportion of patients in the contemporary surgical population have undiagnosed OSA. Strategies based on preoperative and immediate postoperative clinical signs and symptoms can help identify patients with a high likelihood of OSA, postoperative desaturations, and pulmonary complications. ARDS is another serious postoperative complication associated with high mortality rate and limited treatment options, and its prevention is critical. Practice changes have led to a dramatic reduction in ARDS incidence. A recently developed prediction model can help identify high-risk patients. Summary Evidence is emerging that early identification of modifiable risk factors and implementation of ‘protective’ management strategies may lead to reduction of severe postoperative pulmonary complications.

APACHE III outcome prediction in patients admitted to the intensive care unit after liver transplantation: a retrospective cohort study

BackgroundThe Acute Physiology and Chronic Health Evaluation (APACHE) III prognostic system has not been previously validated in patients admitted to the intensive care unit (ICU) after orthotopic liver transplantation (OLT). We hypothesized that APACHE III would perform satisfactorily in patients after OLTMethodsA retrospective cohort study was performed. Patients admitted to the ICU after OLT between July 1996 and May 2008 were identified. Data were abstracted from the institutional APACHE III and liver transplantation databases and individual patient medical records. Standardized mortality ratios (with 95% confidence intervals) were calculated by dividing the observed mortality rates by the rates predicted by APACHE III. The area under the receiver operating characteristic curve (AUC) and the Hosmer-Lemeshow C statistic were used to assess, respectively, discrimination and calibration of APACHE III.ResultsAPACHE III data were available for 918 admissions after OLT. Mean (standard deviation [SD]) APACHE III (APIII) and Acute Physiology (APS) scores on the day of transplant were 60.5 (25.8) and 50.8 (23.6), respectively. Mean (SD) predicted ICU and hospital mortality rates were 7.3% (15.4) and 10.6% (18.9), respectively. The observed ICU and hospital mortality rates were 1.1% and 3.4%, respectively. The standardized ICU and hospital mortality ratios with their 95% C.I. were 0.15 (0.07 to 0.27) and 0.32 (0.22 to 0.45), respectively.There were statistically significant differences in APS, APIII, predicted ICU and predicted hospital mortality between survivors and non-survivors. In predicting mortality, the AUC of APACHE III prediction of hospital death was 0.65 (95% CI, 0.62 to 0.68). The Hosmer-Lemeshow C statistic was 5.288 with a p value of 0.871 (10 degrees of freedom).ConclusionAPACHE III discriminates poorly between survivors and non-survivors of patients admitted to the ICU after OLT. Though APACHE III has been shown to be valid in heterogenous populations and in certain groups of patients with specific diagnoses, it should be used with caution – if used at all – in recipients of liver transplantation.