Fundamental Electrophysiology Principles Related to Perioperative Management of Cardiovascular Implantable Electronic Devices.

An increasing number of patients undergoing elective or emergency surgery in the United States have a cardiovascular implantable electronic device. Practice advisories and consensus statements have been issued by the American Society of Anesthesiologists and the Heart Rhythm Society, advocating a multidisciplinary approach. Unfortunately, anesthesia providers often find themselves in a situation in which they are left to manage these devices independently. At the University of Washington Medical Center, an anesthesiology-based service to manage these devices has existed for more than a decade. Many problems with devices have been observed, including confusing rhythms, failure of magnets to provide the desired change in device function, and actual device malfunction. With these clinical case examples taken from the authors' collective experience, this article provides an in-depth understanding of some key electrophysiology principles relevant to cardiovascular implantable electronic device function and appropriate perioperative management.

Initial Experience of an Anesthesiology-based Service for Perioperative Management of Pacemakers and Implantable Cardioverter Defibrillators.

BACKGROUND: Management of cardiovascular implantable electronic devices (CIEDs), including pacemakers and implantable cardioverter defibrillators, for surgical procedures is challenging due to the increasing number of patients with CIEDs and limited availability of trained providers. At the authors' institution, a small group of anesthesiologists were trained to interrogate CIEDs, devise a management plan, and perform preoperative and postoperative programming and device testing whenever necessary. METHODS: Patients undergoing surgery between October 1, 2009 and June 30, 2013 at the University of Washington Medical Center were included in a retrospective chart review to determine the number of devices actively managed by the Electrophysiology/Cardiology Service (EPCS) versus the Anesthesiology Device Service (ADS), changes in workload over time, surgical case delays due to device management, and errors and problems encountered in device programming. RESULTS: The EPCS managed 254 CIEDs, the ADS managed 548, and 227 by neither service. Over time, the ADS providers managed an increasing percentage of devices with decreasing supervision from the EPCS. Only two CIEDs managed by the ADS required immediate assistance from the EPCS. Patients who were unstable postoperatively were referred to the EPCS. Although numerous issues in programming were encountered, primarily when restoring demand pacing after programming asynchronous pacing for surgery, no patient harm resulted from ADS or EPCS management of CIEDs. CONCLUSIONS: An ADS can provide safe CIED management for surgery, but it requires specialized provider training and strong support from the EPCS. Due to the complexity of CIED management, an ADS will likely only be feasible in high-volume settings.

Associations Between Age and Dosing of Volatile Anesthetics in 2 Academic Hospitals.

BACKGROUND: The inverse relationship between age and dose requirement for potent volatile anesthetics is well established, but the question of whether anesthetic providers consider this relationship in practice remains unanswered. We sought to determine whether there is an association between patient age and the mean dose of volatile anesthetic delivered during maintenance of anesthesia. METHODS: This was a retrospective cross-sectional study of patients receiving a single potent volatile anesthetic at 2 academic hospitals using data recorded in an anesthesia information management system. Multivariate linear models were constructed at each hospital to examine the relationship between age and mean minimum alveolar concentration (MAC) fraction delivered during the maintenance of anesthesia. RESULTS: A total of 7878 cases at the 2 hospitals were included for analysis. For patients aged <65 years, we observed decreasing doses of volatile anesthetics as age increased. Per decade, mean delivered MAC fraction decreased by an estimated 1.8% (95% confidence interval, 1.5-2.2, P < 0.0001), smaller than the 6.7% decrease suggested by previous studies of human anesthetic requirements. At age >65 years, the magnitude of the inverse association between age and MAC fraction was higher (3.8% decrease per decade; 95% confidence interval, 2.9-4.7). CONCLUSIONS: Increasing age is associated with decreased absolute doses of potent volatile anesthetics, an association that seems to strengthen as patients enter the geriatric age range. The observed decreases in absolute anesthetic dose were less than those predicted by previous research and therefore represent an overall increase in "age-adjusted dose" as patients grow older.

Pathomechanisms and complications related to patient positioning and anesthesia during shoulder arthroscopy.

The lateral decubitus and beach-chair positions each offer unique benefits to the shoulder surgeon with respect to visualization, efficiency, and ease during arthroscopic shoulder procedures. The purpose of this article was to comprehensively review the reports and studies documenting independent and dependent complications related to patient positioning and anesthesia during arthroscopic shoulder surgery. The lateral decubitus position has been associated with the potential for peripheral neurapraxia, brachial plexopathy, direct nerve injury, and airway compromise. The beach-chair position has been associated with cervical neurapraxia, pneumothorax, and the potential for end-organ hypoperfusion injuries (when deliberate hypotension is used). Potentially concerning are hypotensive bradycardic events, which may be relatively common in association with the use of epinephrine-containing interscalene anesthetics in beach chair-positioned patients. Irrigant complications (fluid spread, ventricular tachycardia) are avoidable risks not unique to either specific position. Although minor transient anesthetic- and position-related complications (neurapraxia, hypotension) may occur in as many 10% to 30% of patients, major complications such as end-organ damage or permanent impairments are exceedingly rare. Regardless of position, complications are almost uniformly avoidable if surgeon and anesthetist exercise care and prudent attention to position and anesthetic choices. The purpose of this article is to review the potential for position- and anesthesia-related complications and acquaint the shoulder surgeon with the proposed pathophysiologic mechanisms that can lead to them.

Adenine nucleotide control of coronary blood flow during exercise.

The adenine nucleotide hypothesis postulates that the ATP released from red blood cells is broken down to ADP and AMP in coronary capillaries and that ATP, ADP, and AMP act on purinergic receptors on the surface of capillary endothelial cells. Purinergic receptor activation initiates a retrograde conducted vasodilator signal to the upstream arteriole that controls coronary blood flow in a negative feedback manner. A previous study (M. Farias 3rd, M. W. Gorman, M. V. Savage, and E. O. Feigl, Am J Physiol Heart Circ Physiol 288: H1586-H1590, 2005) demonstrated that coronary venous plasma ATP concentration increased during exercise and correlated with coronary blood flow. The present experiments test the adenine nucleotide hypothesis by examining the balance between oxygen delivery (via coronary blood flow) and myocardial oxygen consumption during exercise before and after purinergic receptor blockade. Dogs (n = 7) were chronically instrumented with catheters in the aorta and coronary sinus and a flow transducer around the circumflex coronary artery. During control treadmill exercise, myocardial oxygen consumption increased and the balance between oxygen delivery and myocardial oxygen consumption fell as indicated by a declining coronary venous oxygen tension. Blockade of P1 and P2Y(1) purinergic receptors combined with inhibition of nitric oxide synthesis significantly decreased the balance between oxygen delivery and myocardial oxygen consumption compared with control. The results support the hypothesis that ATP and its breakdown products ADP and AMP are part of a negative feedback control mechanism that matches coronary blood flow to myocardial oxygen consumption at rest and during exercise.

Unexpected Shocks From a Subcutaneous Implantable Cardioverter-Defibrillator Despite Attempted Reprogramming and Magnet Use: A Case Report.

We present the case of a patient with a subcutaneous implantable cardioverter-defibrillator (S-ICD) in situ. Device interrogation and reprogramming were unsuccessful due to a software mismatch between the device and programmer. The device manufacturer recommended magnet application to suspend antitachycardia therapy. Despite using this strategy, the S-ICD discharged multiple times. The S-ICD has unique perioperative considerations for the anesthesiologist. This case provides an example of the complexity of electrophysiologic devices in current use and the necessity of the anesthesia provider to stay up to date with evolving device management strategies.

Self-reported functional status predicts post-operative outcomes in non-cardiac surgery patients with pulmonary hypertension.

BACKGROUND: Pulmonary hypertension (PHTN) is associated with increased post-procedure morbidity and mortality. Pre-procedure echocardiography (ECHO) is a widely used tool for evaluation of these patients, but its accuracy in predicting post-procedure outcomes is unproven. Self-reported exercise tolerance has not been evaluated for operative risk stratification of PHTN patients. OBJECTIVE: We analyzed whether self-reported exercise tolerance predicts outcomes (hospital length-of-stay [LOS], mortality and morbidity) in PHTN patients (WHO Class I-V) undergoing anesthesia and surgery. METHODS AND FINDINGS: We reviewed 550 non-cardiac, non-obstetric procedures performed on 370 PHTN patients at a single institution between 2007 and 2013. All patients had cardiac ECHO documented within 1 year prior to the procedure. Pre-procedure comorbidities and ECHO data were collected. Functional status (< or ≥ 4 metabolic equivalents of task [METs]) was assigned based on responses to standard patient interview questions during the pre-anesthesia clinic visit. Multiple logistic regression was used to develop a risk score model (Pulmonary Hypertension Outcome Risk Score; PHORS) and determine its value in predicting post-procedure outcomes. In an adjusted model, functional status <4 METs was independently associated with a LOS >7 days (p < .003), as were higher ASA class (p < .002), open surgical approach (p < .002), procedure duration > 2 hours (p < .001), and the absence of systemic hypertension (p = .012). PHORS Score ≥2 was associated with an increased 30-day major complication rate (28.7% vs. 19.2%; p < 0.001) and ICU admission rate (8.6% s 2.8%; p = .007), but no statistical difference in hospital readmissions rate (17.6% vs. 14.0%; p = .29), or mortality (3.5% vs. 1.4%; p = .75). Similar ECHO findings did not further improve outcome prediction. CONCLUSIONS: Poor functional status is associated with severe PHTN and predicts increased LOS and post-procedure complications in patients with moderate to severe pulmonary hypertension with different etiologies. A risk assessment model predicts increased LOS with fair accuracy. A thorough evaluation of underlying etiologies of PHTN should be undertaken in every patient.

Perioperative hypotension and discharge outcomes in non-critically injured trauma patients, a single centre retrospective cohort study.

BACKGROUND: There is a lack of information on the effect of age on perioperative care and outcomes after minor trauma in the elderly. We examined the association between perioperative hypotension and discharge outcome among non-critically injured adult patients. METHODS: We conducted a retrospective study of non-critically ill patients (ISS <9 or discharged within less than 24h) who received anaesthesia care for surgery and Recovery Room care at a level-1 trauma centre between 5/1/2012 and 11/30/2013. Perioperative hypotension was defined as systolic blood pressure (SBP) <90mmHg (traditional measure) for all patients, and SBP <110mmHg (strict measure) for patients ≥65years. Poor outcome was defined as death or discharge to skilled nursing facility/hospice. RESULTS: 1744 patients with mean ISS 4.4 across age groups were included; 169 (10%) were ≥65years. Among patients≥65years, intraoperative hypotension occurred in >75% (131/169, traditional measure) and in >95% (162/169, strict measure); recovery room hypotension occurred in 2% (4/169) and 29% (49/169), respectively. Mean age-adjusted anaesthetic agent concentration (MAC) was similar across age groups. Opioid use decreased from 9.3 (SD 5.7) mg/h morphine equivalents in patients <55years to 6.2 (SD 4.0) mg/h in patients over 85 years. Adjusted for gender, ASA score, anaesthesia duration, morphine equivalent/hr, fluid balance, MAC and surgery type, and using traditional definition, older patients were more likely than patients <55 to experience perioperative hypotension: aRR 1.21, 95% CI 1.11-1.30 for 55-64 and aRR 1.19, 95% CI 1.07-1.32 for ages 65-74. Perioperative hypotension was associated with poor discharge outcome (aRR 1.55; 95% CI 1.04-2.31 and aRR 1.87; 95% CI 1.17-2.98, respectively). CONCLUSION: Despite age related reduction in doses of volatile anaesthetic and opioids administered during anaesthesia care, and regardless of hypotension definition used, non-critically injured patients undergoing surgery experience a large perioperative hypotension burden. This burden is higher for patients 55-74 years and older and is a risk factor for poor discharge outcomes, independent of age and ASA status.

The History of Geriatric Anesthesia in the United States and the Society for the Advancement of Geriatric Anesthesia.

Creation of the American Society of Anesthesiologists Committee on Geriatric Anesthesia provided an opportunity for individuals to interact, strategize, and work with medical organizations outside of anesthesiology. These opportunities expanded with creation of the Society for the Advancement of Geriatric Anesthesia. The American Geriatrics Society provided a major boost when they realized it was important for surgical and related specialties to take an active role in the care of older patients. From this have come educational grants to improve residency training and establishment of a major research grant program now managed by the National Institutes of Health. Nevertheless, for improved care of the older patient, the level of involvement has to increase.

Evaluation of anesthesia residents using mannequin-based simulation: a multiinstitutional study.

BACKGROUND: Anesthesia simulators can generate reproducible, standardized clinical scenarios for instruction and evaluation purposes. Valid and reliable simulated scenarios and grading systems must be developed to use simulation for evaluation of anesthesia residents. METHODS: After obtaining Human Subjects approval at each of the 10 participating institutions, 99 anesthesia residents consented to be videotaped during their management of four simulated scenarios on MedSim or METI mannequin-based anesthesia simulators. Using two different grading forms, two evaluators at each department independently reviewed the videotapes of the subjects from their institution to score the residents' performance. A third evaluator, at an outside institution, reviewed the videotape again. Statistical analysis was performed for construct- and criterion-related validity, internal consistency, interrater reliability, and intersimulator reliability. A single evaluator reviewed all videotapes a fourth time to determine the frequency of certain management errors. RESULTS: Even advanced anesthesia residents nearing completion of their training made numerous management errors; however, construct-related validity of mannequin-based simulator assessment was supported by an overall improvement in simulator scores from CB and CA-1 to CA-2 and CA-3 levels of training. Subjects rated the simulator scenarios as realistic (3.47 out of possible 4), further supporting construct-related validity. Criterion-related validity was supported by moderate correlation of simulator scores with departmental faculty evaluations (0.37-0.41, P < 0.01), ABA written in-training scores (0.44-0.49, < 0.01), and departmental mock oral board scores (0.44-0.47, P < 0.01). Reliability of the simulator assessment was demonstrated by very good internal consistency (alpha = 0.71-0.76) and excellent interrater reliability (correlation = 0.94-0.96; P < 0.01; kappa = 0.81-0.90). There was no significant difference in METI versus MedSim scores for residents in the same year of training. CONCLUSIONS: Numerous management errors were identified in this study of anesthesia residents from 10 institutions. Further attention to these problems may benefit residency training since advanced residents continued to make these errors. Evaluation of anesthesia residents using mannequin-based simulators shows promise, adding a new dimension to current assessment methods. Further improvements are necessary in the simulation scenarios and grading criteria before mannequin-based simulation is used for accreditation purposes.

Low-flow sevoflurane compared with low-flow isoflurane anesthesia in patients with stable renal insufficiency.

BACKGROUND: Sevoflurane is degraded to compound A (CpA) by carbon dioxide absorbents containing strong base. CpA is nephrotoxic in rats. Patient exposure to CpA is increased with low fresh gas flow rates, use of Baralyme, and high sevoflurane concentrations. CpA formation during low-flow and closed circuit sevoflurane anesthesia had no significant renal effects in surgical patients with normal renal function. Preexisting renal insufficiency is a risk factor for postoperative renal dysfunction. Although preexisting renal insufficiency is not affected by high-flow sevoflurane, the effect of low-flow sevoflurane in patients with renal insufficiency is unknown. METHODS: After obtaining institutional review board approval, 116 patients with a stable preoperative serum creatinine concentration 1.5 mg/dl or greater were assessable. Patients were randomized to receive either sevoflurane (n = 59, 0.8-2.5 vol%) or isoflurane (n = 57, 0.5-1.4 vol%) at a fresh gas flow rate of 1 l/min or less. Use of opioids was restricted to a minimum, and Baralyme was used to increase CpA exposure. Inspiratory and expiratory CpA concentrations were measured during anesthesia. Renal function (serum creatinine and blood urea nitrogen, urine protein and glucose, creatinine clearance) was measured preoperatively and 24 and 72 h after induction. RESULTS: Demographic patient data did not differ between groups. Patients received 3.1 +/- 2.4 minimum alveolar concentration-hours sevoflurane or 3.8 +/- 2.6 minimum alveolar concentration-hours isoflurane (mean +/- SD). Durations of low flow were 201.3 +/- 98.0 and 213.6 +/- 83.4 min, respectively. Maximum inspiratory CpA with sevoflurane was 18.9 +/- 7.6 ppm (mean +/- SD), resulting in an average total CpA exposure of 44.0 +/- 30.6 ppm/h. There were no statistically significant changes from baseline to 24- and 72-h values for serum creatinine or blood urea nitrogen, creatinine clearance, urine protein, and glucose, nor were there significant differences between both anesthetics. CONCLUSION: There were no statistically significant differences in measured parameters of renal function after low-flow sevoflurane anesthesia compared with isoflurane. These results suggest that low-flow sevoflurane anesthesia is as safe as low-flow isoflurane and does not alter kidney function in patients with preexisting renal disease.