Exploring phenotype-based ventilator parameter optimization to mitigate postoperative pulmonary complications: a retrospective observational cohort study.

PURPOSE: To identify tidal volume (VT) and positive end-expiratory pressure (PEEP) associated with the lowest incidence and severity of postoperative pulmonary complications (PPCs) for each phenotype based on preoperative characteristics. METHODS: The subjects of this retrospective observational cohort study were 34,910 adults who underwent surgery, using general anesthesia with mechanical ventilation. Initially, the least absolute shrinkage and selection operator regression was employed to select relevant preoperative characteristics. Then, the classification and regression tree (CART) was built to identify phenotypes. Finally, we computed the area under the receiver operating characteristic curves from logistic regressions to identify VT and PEEP associated with the lowest incidence and severity of PPCs for each phenotype. RESULTS: CARTs classified seven phenotypes for each outcome. A probability of the development of PPCs ranged from the lowest (3.51%) to the highest (68.57%), whereas the probability of the development of the highest level of PPC severity ranged from 3.3% to 91.0%. Across all phenotypes, the VT and PEEP associated with the most desirable outcomes were within a small range of VT 7-8 ml/kg predicted body weight with PEEP of between 6 and 8 cmH2O. CONCLUSIONS: The ranges of optimal VT and PEEP were small, regardless of the phenotypes, which had a wide range of risk profiles.

Fast-Tracking Patients in an Academic Hospital to Increase Efficiency and Decrease Discharge Delays: A Process Improvement Plan.

PURPOSE: The purpose of this quality improvement project was to determine if implementing a Phase II postanesthesia care unit (PACU II) to fast-track patients following surgery in an academic hospital would decrease OR hold times and increase patient flow efficiency. DESIGN: An observational pre-post design was used to compare PACU bypass rates and recovery times for ambulatory surgery (AS) patients before and after implementation of a patient fast-tracking program. METHODS: A PACU II was instituted and a fast-tracking program using the White Fast-Track Scoring tool was adopted. Nursing staff as well as anesthesia providers were educated to assess patients using the tool as well as the appropriate patient population to be transferred to the new PACU II. FINDINGS: Following implementation of the new unit and the fast-tracking program, a PACU bypass rate of 30% was achieved and there was a significant decrease in PACU length of stay for AS patients. CONCLUSIONS: The results suggest that fast-tracking is a suitable intervention to decrease inefficiencies in an academic setting despite higher acuity patient populations.

Review of the Mechanisms of Ventilator Induced Lung Injury and the Principles of Intraoperative Lung Protective Ventilation.

Intraoperative ventilator induced lung injury is associated with development of postoperative pulmonary complications. Despite advances in modes and methods of mechanical ventilation, postoperative pulmonary complications remain as one of the leading causes of adverse outcomes following surgery and anesthesia. In an attempt to reduce the incidence of postoperative pulmonary complications, the use of an intraoperative ventilatory technique to minimize lung injury has been introduced. Lung protective ventilation typically entails the use of a physiologic tidal volume, positive end expiratory pressure, extended inspiratory time, and an alveolar recruitment maneuver. The goal of intraoperative lung protective ventilation is to prevent or at least minimize development of ventilator induced lung injury by maintaining a homogeneous lung and alveolar stability during and after a surgical procedure. To appreciate the value of the application of an intraoperative lung protective ventilation strategy, the pathophysiology and developmental processes of ventilator induced lung injury must first be understood. The primary purpose of this paper is to provide a basic understanding of the relationship between conventional intraoperative mechanical ventilation, pulmonary derangement and lung injury as well as a rationale for the use of individualized lung protective ventilation to optimize surgical patient pulmonary outcomes.

Optimizing Intraoperative Fluid Replacement for Patients Receiving Mannitol During Neurosurgical Procedures: A Quality Improvement Initiative.

Patients undergoing craniotomy are at increased risk of intravascular volume changes due to the use of mannitol. This quality improvement project was conducted to implement a standardized goal-directed fluid therapy (GDFT) protocol using a dynamic physiologic measure in an attempt to maintain euvolemia in patients undergoing craniotomy with mannitol administration. An evidence-based GDFT protocol was integrated into an existing neurosurgical protocol. Anesthesia providers were asked to implement the protocol in patients who met the screening criteria. A preimplementation and postimplementation record review was conducted to compare outcomes of the intervention with standard practice. Primary outcomes included intensive care unit (ICU) length of stay (LOS), hospital LOS, serum lactate levels, and the total amounts of intraoperative crystalloid and colloid administered between the preimplementation and postimplementation groups. Of 95 patients who met the screening criteria, 51 (54%) had full protocol compliance. There was no significant difference between groups in ICU LOS (P=.700), hospital LOS (P=.948), serum lactate levels (P=.484), or the total amount of intraoperative crystalloid administered (P=.122). The postimplementation group had significantly more colloid administered than the preimplementation group (P=.004). A lack of provider compliance with the protocol may have affected these results. Further refined quality improvement cycles are warranted.

Does Ultrasonographic Measurement of Gastric Content Influence Airway Management Decisions?

The presence of gastric content before induction of general anesthesia is the primary modifiable risk factor in the prevention of pulmonary aspiration. The purpose of this project was to determine if ultrasonography could be routinely used to measure gastric content and assign aspiration risk in patients undergoing general anesthesia. Preoperative gastric ultrasonography was performed in a convenience sample of 100 patients. A group of Certified Registered Nurse Anesthetists, anesthesia residents, and anesthesiologists were asked their plan for airway management before and after receiving the results of the patients' gastric ultrasonogram, to determine if the scan would alter the plan. In 14% of patients scanned, solid gastric content was observed, 7% had clear liquids present, and 79% had an empty stomach. Of the patients with clear liquids present, 3 had substantial (> 100 mL) gastric content despite following fasting guidelines. Overall, there was a 9% change in airway management from standard induction: 6% changed to modified rapid sequence intubation (no ventilation, no cricoid pressure), and 3% changed to rapid sequence intubation with cricoid pressure. The number of changes to the airway management plan and identification of several patients with substantial gastric content demonstrate the value of preoperative gastric ultrasonography in airway management decision making.

Use of Near-Infrared Spectroscopy to Measure Tissue Oxygen Saturation During Total Knee Arthroplasty With Use of a Tourniquet.

The primary purpose of this proof-of-concept quality improvement effort was to evaluate the practicality of using near-infrared spectroscopy (NIRS) to measure tissue oxygen saturation (Sto2) during total knee arthroplasty (TKA) with use of a tourniquet. NIRS sensors were applied to the biceps femoris (BF) and gastrocnemius (GS) muscles of both lower extremities of patients undergoing TKA procedures. For a convenience sample of 15 patients, measurement of Sto2 was attempted at baseline, following subarachnoid block administration, and after tourniquet inflation and deflation. Mean baseline Sto2 (SD) was 71% (6%) in the BF muscle and 66% (7%) in the GS muscle. Significant changes in Sto2 values were observed following subarachnoid block, tourniquet inflation, and tourniquet deflation. The Sto2 returned to or above baseline in the BF muscle but did not return to baseline in the GS muscle following tourniquet deflation. Changes in tissue oxygen saturation resulting from use of a tourniquet can be continuously monitored with the use of an NIRS device. Further evaluation of the use of NIRS should be undertaken to determine if it could be used to guide safe duration and pressure limits for tourniquet inflation.

Preparing for Total Power Failure in the Operating Room.

Total electrical power failure in the operating room is an uncommon event, but when it occurs, it poses a major threat to patient safety. Perhaps the most curable threat to patient safety is the lack of provider knowledge regarding what equipment capabilities will be lost and how long devices will function on battery power. The purpose of this project was to determine the internal battery-related capabilities and duration of function of site-specific anesthesia equipment during a total power failure and to develop a power failure protocol. Equipment capabilities and duration of function on internal battery power were assessed for several anesthesia gas machines (AGM), vital sign monitors, and intravenous infusion pumps. Testing revealed substantial differences in AGM battery life compared with the manufacturer's reference values. Vital sign monitors integral to the AGM failed immediately on simulation of a power failure, whereas portable vital sign monitors and infusion pumps functioned, on average, for 150 and 270 minutes, respectively. Because many devices relied on in the operating room do not operate or have reduced functional capability during a power failure, it is important to have a site-specific protocol to optimize patient care decision making in the event of a total power failure.

Lung-protective ventilation for the surgical patient: international expert panel-based consensus recommendations.

Postoperative pulmonary complications (PPCs) occur frequently and are associated with substantial morbidity and mortality. Evidence suggests that reduction of PPCs can be accomplished by using lung-protective ventilation strategies intraoperatively, but a consensus on perioperative management has not been established. We sought to determine recommendations for lung protection for the surgical patient at an international consensus development conference. Seven experts produced 24 questions concerning preoperative assessment and intraoperative mechanical ventilation for patients at risk of developing PPCs. Six researchers assessed the literature using questions as a framework for their review. The modified Delphi method was utilised by a team of experts to produce recommendations and statements from study questions. An expert consensus was reached for 22 recommendations and four statements. The following are the highlights: (i) a dedicated score should be used for preoperative pulmonary risk evaluation; and (ii) an individualised mechanical ventilation may improve the mechanics of breathing and respiratory function, and prevent PPCs. The ventilator should initially be set to a tidal volume of 6-8 ml kg-1 predicted body weight and positive end-expiratory pressure (PEEP) 5 cm H2O. PEEP should be individualised thereafter. When recruitment manoeuvres are performed, the lowest effective pressure and shortest effective time or fewest number of breaths should be used.

Evaluating a Quality Improvement Initiative to Increase Anesthesia Providers' Use of and Understanding of Quantitative Neuromuscular Monitors.

Improved understanding of the monitoring and dosing practices of anesthesia providers regarding neuromuscular blockade is necessary. The use of subjective methods such as peripheral nerve stimulation and clinical assessment tests can increase the risk of residual neuromuscular blockade and adverse postoperative outcomes. Quantitative monitoring of neuromuscular blockade is an alternative tool to peripheral nerve stimulation to guide neuromuscular blockade; however, it is rarely used by providers. We developed an initiative to improve anesthesia providers' knowledge of neuromuscular blockade pharmacology, physiology, monitoring, and management. After the initiative, an analysis assessed for practice change regarding the use of quantitative monitoring and dosing of neuromuscular blocking agents and neostigmine. The use of quantitative monitoring increased significantly from 14.0% in the preinitiative group to 48.0% after the initiative (P < .001). The least squares mean 95% effective dose (ED95) neuromuscular blocking agents dose was compared between pre-initiative and postinitiative groups, and case length was a significant predictor for patients receiving the highest neuromuscular blocking agents doses. Neostigmine doses were compared between preinitiative and postinitiative groups, and body mass index was a significant predictor of the least squares mean neostigmine dose (P = .002) and the likelihood of receiving a high neostigmine dose (odds ratio = 0.911, 95% CI = 0.870-0.955).

Nursing Perceptions and Workload Impact of a Standardized Emergence Delirium Assessment Scale in a Postanesthesia Care Unit.

PURPOSE: Emergence delirium (EDL) is a psychomotor behavioral phenomenon that occurs immediately after emergence from general anesthesia. EDL is nearly 1.5 times more common among military than nonmilitary patients. Indirect delirium scales have precluded understanding of EDL in military patients. This quality improvement project assesses the feasibility of adopting a population-specific scale, the Emergence Delirium in the Wounded Warrior (ED-WW) Tool. DESIGN: Pre-post implementation design. METHODS: Postanesthesia care unit (PACU) nurses were surveyed on the clinical utility of the ED-WW Tool and its impact on their workload. The incidence of EDL behaviors in a Veterans Administration PACU was also recorded using the ED-WW Tool. FINDINGS: PACU nurses agreed the ED-WW Tool was of clinical value to military patients and had a very low workload impact. Twenty-one percent of patients demonstrated at least one behavior associated with EDL. CONCLUSIONS: ED-WW Tool adoption is clinically feasible and recommended for practice.

Low-Flow Domiciliary Oxygen as a Mechanism of Ongoing Oxidative Stress.

BACKGROUND: Oxidative stress occurs when imbalances exist between the production of oxygen free radicals and endogenous antioxidants that neutralize their harmful effects, causing irreversible tissue damage. Oxygen free radicals readily interact with DNA, proteins, and lipids, instigating conformational changes to cellular structures and leading to derangement and dysfunction. Oxidative stress is a key feature in the pathology of COPD. As disease progression occurs, supplemental oxygen is often warranted to ameliorate dyspnea. It has been established that supplemental oxygen at > 0.60 FIO2 is an instigator of oxidative stress. We sought to determine whether chronic exposure to low-flow domiciliary oxygen served as a mechanism of ongoing oxidative stress in this patient population. This study serves to inform best practices for low-flow domiciliary oxygen therapy. METHODS: We utilized prospective data collection for this study. The exhaled-breath condensate (EBC) of 52 subjects with COPD (FEV1 < 70% of predicted normal for age and gender, height, weight, and smoking history) was evaluated for isofuran (IsoF), an oxidative stress biomarker synthesized in response to elevated tissue oxygen tension. The active control group (n = 26) was compared to the active treatment group receiving low-flow domiciliary oxygen for ≥ 6 h/d (n = 26). RESULTS: The active control group generated a mean ± SD EBC IsoF level of 35.81 ± 25.0 pg/mL compared to the active treatment group's level of 51.37 ± 42.2 pg/mL (P = .057). CONCLUSIONS: In subjects diagnosed with advanced COPD, chronic exposure to supplemental oxygen therapy at concentrations ≤ 36% did not appear to induce oxidative stress based on EBC IsoF levels. Our findings do not substantiate that chronic exposure to supplemental oxygen at concentrations < 36% instigates oxidative stress, and, therefore, changes to current domiciliary oxygen therapy prescription practices are not warranted.

Improving infection control practices of nurse anesthetists in the anesthesia workspace.

BACKGROUND: Anesthesia providers commonly cross-contaminate their workspace and subsequently put patients at risk for a health care-acquired infection. The primary objective of this project was to determine if education and implementation of standardized infection control guidelines that address evidence-based best practices would improve compliance with infection control procedures in the anesthesia workspace. METHODS: Patient care-related hand hygiene of nurse anesthetists was observed in 3 areas of anesthesia practice before and 3 weeks and 3 months after staff education, placement of visual reminders, and the implementation of infection control guidelines. After the observation periods, the percent compliance on the part of the providers was calculated for each of the 3 areas of anesthesia practice, and the results were compared using the Fisher exact test. RESULTS: There were a total of 95 observations performed during the 3 observation periods. When compared with preimplementation baseline data, there was a 26.2% increase in the number of providers compliant with hand hygiene practices after airway instrumentation (P = .029) and a 71.9% increase in the number of providers who separated clean from contaminated items in the workspace (P = .0001). CONCLUSIONS: Education, visual reminders, and standardized infection control guidelines were shown to improve compliance with infection control best practices in a group of nurse anesthetists.

Enhancing the Quality of the Anesthesia to Postanesthesia Care Unit Patient Transfer Through Use of an Electronic Medical Record-Based Handoff Tool.

PURPOSE: Anesthesia to postanesthesia care unit (PACU) handoffs are often incomplete, imprecise, and highly variable with respect to information transfer, and therefore can jeopardize patient safety. A standardized anesthesia to PACU electronic medical record (EMR)-based patient handoff checklist was implemented and evaluated for its effect on the information transfer. DESIGN: An observational preimplementation and postimplementation design was used. METHODS: Assessment of the completeness and accuracy of information transfer during the PACU handoff was performed for a convenience samples of 100 patients preimplementation, 3 weeks postimplementation, and 3 months postimplementation. FINDINGS: The mean percentage of total handoff checklist items addressed significantly increased 3 weeks and 3 months postimplementation compared with baseline. CONCLUSIONS: The use of a standardized anesthesia to PACU EMR-based handoff checklist significantly increased the percent of accurate information transferred without considerably affecting the duration of the PACU handoff process.

Characterization of bilateral frontal lobe cerebral oxygen saturation in patients with mild traumatic brain injury.

BACKGROUND: There is clear evidence of the potential for long-term neuro behavioral and cognitive sequelae following a mild traumatic brain injury (mTBI). Although the source of these persistent behavioral and cognitive issues is unclear, several studies have suggested a cerebral vascular disorder is a likely contributor. PURPOSE: Measure and compare cerebral blood oxygen saturation values in frontal brain lobes of subjects with and without a history of mTBI. METHODS: Bilateral frontal brain lobe blood oxygen saturation was measured using near-infrared spectroscopy in mTBI and non-brain injured subjects while alternately breathing room air and a mildly hypoxic gas mixture. RESULTS: Subjects with a history of mTBI displayed a significantly different trajectory of change in their cerebral oxygen saturation values during exposure to mild hypoxia compared to controls. DISCUSSION: The finding confirms and adds to previous research that indicates there is likely a vascular component to this mild form of brain injury.

Retinal oximetry measures systemic hypoxia in central nervous system vessels in chronic obstructive pulmonary disease.

BACKGROUND: Determination of the blood oxyhemoglobin saturation in the retinal vessels of the eye can be achieved through spectrophotometric retinal oximetry which provides access to the state of oxyhemoglobin saturation in the central nervous system circulation. The purpose of this study was to test the capability of the Oxymap T1 oximeter to detect systemic hypoxemia and the effect of supplemental oxygen on retinal vessel oxyhemoglobin saturation. METHODS: Oxygen saturation of hemoglobin in retinal arterioles and venules was measured in 11 subjects with severe chronic obstructive pulmonary disease (COPD) on long term oxygen therapy. Measurements were made with and without their daily supplemental oxygen. Eleven healthy age and gender matched subjects were measured during ambient air breathing for comparison of oxyhemoglobin saturation in retinal arterioles and venules. Retinal arteriolar oxyhemoglobin saturation in COPD subjects inspiring ambient air was compared with finger pulse oximetry and blood samples from radial artery. RESULTS: COPD subjects had significantly lower oxyhemoglobin saturation during ambient air breathing than healthy controls in both retinal arterioles (87.2%±4.9% vs. 93.4%±4.3%, p = 0.02; n = 11) and venules (45.0%±10.3% vs. 55.2%±5.5%, p = 0.01). Administration of their prescribed supplemental oxygen increased oxyhemoglobin saturation in retinal arterioles (87.2%±4.9% to 89.5%±6.0%, p = 0.02) but not in venules (45.0%±10.3% to 46.7%±12.8%, p = 0.3). Retinal oximetry values were slightly lower than radial artery blood values (mean percentage points difference = -5.0±5.4, 95% CI: -15.68 to 5.67) and finger pulse oximetry values (-3.1±5.5, 95% CI: -14.05 to 7.84). CONCLUSIONS: The noninvasive Oxymap T1 retinal oximetry detects hypoxemia in central nervous system vessels in patients with severe COPD compared with healthy controls. The instrument is sensitive to changes in oxygen breathing but displays slightly lower measures than finger pulse oximetry or radial artery measures. With further technological improvement, retinal oximetry may offer noninvasive "on-line" measurement of oxygen levels in central circulation in general anesthesia and critically ill patients.

Point-of-Contact Assessment of Nurse Anesthetists' Knowledge and Perceptions of Management of Anesthesia-Related Critical Incidents.

Most anesthesia providers will experience at least one perioperative critical incident during their career, potentially causing critical incident stress symptoms that may affect their ability to provide patient care. The purpose of this descriptive pilot investigation of Certified Registered Nurse Anesthetists (CRNAs) was to determine if their knowledge of the psychological and physical ramifications of critical incidents, coping strategies to deal with critical incident stress, and satisfaction with departmental handling of critical incidents improved when a formal, institutionally relevant critical incident stress management policy and protocol was developed and implemented. Knowledge of the effects of a critical incident, available coping strategies, and the perceived value of a stress management support protocol were assessed by surveys conducted before and after the implementation of a formal educational program. The results demonstrated that knowledge of critical incident stress and coping strategies improved with a staff educational program, with 25 of 26 respondents (96%) reporting that having a departmental critical incident stress management policy and protocol in place was valuable. This pilot investigation indicates that supportive protocols and education programs for critical incident stress management are beneficial and increase the CRNAs' confidence in their ability to cope with critical incidents.

Fast-tracking ambulatory surgery patients following anesthesia.

PURPOSE: The purpose of this process improvement project was to introduce and evaluate the efficacy of fast-tracking ambulatory surgical patients in a community hospital. DESIGN: An observational pre-post design was used, in which patient data from a reference period (pre-fast-tracking) was compared with patient data collected during an implementation period (post-fast-tracking). METHODS: Anesthesia providers were trained to use a tool to assess patients for eligibility to bypass the postanesthesia care unit (PACU). Fifty-nine patients met the fast-track criteria during the implementation period and were transferred directly to the ambulatory care unit from the operating room. FINDING: During the fast-track implementation period, a PACU-bypass rate of 79% was achieved, and a significant decrease in the total number of patients held in the operating room and in total length of stay was noted. CONCLUSIONS: Results suggest that fast-tracking is a suitable intervention to increase work flow efficiency and decrease both patient and hospital costs while promoting a more rapid discharge from the facility.

A Theoretical Mathematical Model to Estimate Blood Volume in Clinical Practice.

Perioperative intravenous (IV) fluid management is controversial. Fluid therapy is guided by inaccurate algorithms and changes in the patient's vital signs that are nonspecific for changes to the patient's blood volume (BV). Anesthetic agents, patient comorbidities, and surgical techniques interact and further confound clinical assessment of volume status. Through adaptation of existing acute normovolemic hemodilution algorithms, it may be possible to predict patient's BV by measuring hematocrit (HcT) before and after hemodilution. Our proposed mathematical model requires the following four data points to estimate a patient's total BV: ideal BV, baseline HcT, a known fluid bolus (FB), and a second HcT following the FB. To test our method, we obtained 10 ideal and 10 actual subject BV data measures from 9 unique subjects derived from a commercially used Food and Drug Administration-approved, semi-automated, BV analyzer. With these data, we calculated the theoretical BV change following a FB. Using the four required data points, we predicted BVs (BVp) and compared our predictions with the actual BV (BVa) measures provided by the data set. The BVp calculated using our model highly correlated with the BVa provided by the BV analyzer data set (df = 8, r = .99). Our calculations suggest that, with accurate HcT measurement, this method shows promise for the identification of abnormal BV states such as hyper- and hypovolemia and may prove to be a reliable method for titrating IV fluid.