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.

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.

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.

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.