Vasoplegia Following Complex Spine Surgery: Incidence and Risk

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Vasoplegia is a life-threatening form of distributive or vasodilatory shock that is characterized by reduced systemic vascular resistance with resultant hypotension and normal to elevated cardiac output affecting morbidity and mortality. Vasoplegia in the context of Spine Surgery has not been described previously. The purpose of this case series is to determine incidence, risk factors, complications and postoperative outcome in patients with vasoplegia after complex multi-level thoraco-lumbar spine surgery.

METHODS

A retrospective review of the electronic medical records at our institution was conducted between January 2014 and June 2018. All patients undergoing multi-level spine surgery (>6 levels) were screened for intraoperative hypotension. Patient demographics, surgical characteristics, neurological status, blood loss, risk factors, medical treatment, complications, hospital course and mortality were collected. All patients included in this study had a minimum follow-up period of 3 months.

RESULTS

Out of 8521 surgically treated patients, 994 patients with multi-level thoraco-lumbar spine surgery were identified. A total of 41 patients had intraoperative hypotensive events. Of those, 5 patients with vasoplegia could be identified after elimination of all other potential contributing factors. Vasoplegia did not influence the neurological outcome. One major and three minor complications occurred. All patients showed full recovery. The risk factors identified for vasoplegia include prolonged surgery with osteotomies.

CONCLUSIONS

Vasoplegia is a rare condition with an incidence of .6%. Patients experiencing vasoplegia did not appear to experience worse surgical outcomes. The use of special intraoperative hemodynamic monitoring should be considered in selected cases.

Perioperative approach to precapillary pulmonary hypertension in non-cardiac non-obstetric surgery

Pulmonary hypertension (PH) confers a significant challenge in perioperative care. It is associated with substantial morbidity and mortality. A considerable amount of information about management of patients with PH has emerged over the past decade. However, there is still a paucity of information to guide perioperative evaluation and management of these patients. Yet, a satisfactory outcome is feasible by focusing on elaborate disease-adapted anaesthetic management of this complex disease with a multidisciplinary approach. The cornerstone of the peri-anaesthetic management of patients with PH is preservation of right ventricular (RV) function with attention on maintaining RV preload, contractility and limiting increase in RV afterload at each stage of the patient's perioperative care. Pre-anaesthetic evaluation, choice of anaesthetic agents, proper fluid management, appropriate ventilation, correction of hypoxia, hypercarbia, acid-base balance and pain control are paramount in this regard. Essentially, the perioperative management of PH patients is intricate and multifaceted. Unfortunately, a comprehensive evidence-based guideline is lacking to navigate us through this complex process. We conducted a literature review on patients with PH with a focus on the perioperative evaluation and suggest management algorithms for these patients during non-cardiac, non-obstetric surgery.

Impact of New-Onset Left Ventricular Dysfunction on Outcomes in Mechanically Ventilated Patients With Severe Sepsis and Septic Shock

BACKGROUND:

Left ventricular systolic dysfunction (LVSD) and LV diastolic dysfunction (LVDD) are commonly seen in severe sepsis and septic shock; however, their role in patients with concurrent invasive mechanical ventilation (IMV) is less well defined.

METHODS:

This was a prospective observational study on all patients admitted to all the intensive care units (ICUs) at Mayo Clinic, Rochester from August 2007 to January 2009. All adult patients with severe sepsis and septic shock and concurrent IMV without prior heart failure underwent transthoracic echocardiography within 24 hours. Patients with active pregnancy, prior congenital or valvular heart disease, and prosthetic cardiac valves were excluded. Left ventricular systolic dysfunction was defined as LV ejection fraction (LVEF) <50% and LVDD as E/e' >15. Primary outcome was hospital mortality, and secondary outcomes included IMV duration, ICU length of stay (LOS), and total LOS. Two-tailed P value of <.05 was considered statistically significant.

RESULTS:

In a total of 106 patients, 58 (54.7%) met our inclusion criteria, with 17 (29.3%), 11 (19.0%), and 5 (8.6%) having LVSD, LVDD, and both, respectively. The cohorts with and without LVSD and LVDD did not differ significantly in their baseline characteristics and laboratory and ventilatory parameters. Compared to those without LVSD, patients with LVSD had higher LV end-systolic diameters but were not different in their left atrial diameters or E/e' ratio. Patients with LVDD had a higher E velocity and E/e' ratio compared to those without LVDD. Hospital mortality was not different in patients with and without LVSD (8 [47%] vs 21 [51%], P = 1.00) and LVDD (8 [73%] vs 21 [45%], P = .18). Secondary outcomes were not different between the 2 groups.

CONCLUSION:

Left ventricular systolic or diastolic dysfunction did not influence in-hospital outcomes in patients with severe sepsis and septic shock and concurrent IMV.

Neuromonitoring, Cerebrospinal Fluid Drainage, and Selective Use of Iliofemoral Conduits to Minimize Risk of Spinal Cord Injury During Complex Endovascular Aortic Repair

Purpose: To review outcomes of continuous motor/somatosensory-evoked potential (MEP/SSEP) monitoring, cerebrospinal fluid drainage, and selective use of iliofemoral conduits in patients undergoing endovascular repair of descending thoracic aneurysm (DTA) and thoracoabdominal aortic aneurysms (TAAAs). Methods: The clinical data of 49 patients (mean age 75±8 years; 38 men) who underwent endovascular repair of DTA and TAAAs (2011–2014) were reviewed. All patients had cerebrospinal fluid drainage, permissive hypertension (mean arterial pressure ≥80 mm Hg), and MEP/SSEP monitoring. There were 44 (90%) patients with TAAAs and 5 (10%) with DTA. Types I and II TAAAs were repaired in staged procedures. Iliofemoral conduits were used for small iliac arteries and to minimize time of lower extremity ischemia in patients with difficult anatomy. In patients with changes in MEP/SSEPs, a standardized protocol was employed to optimize spinal cord perfusion and restore lower extremity blood flow. Endpoints were mortality, spinal cord injury (SCI), and lower extremity ischemic complications. Results: Sixteen (33%) patients had staged TAAA repair. A total of 163 visceral arteries were targeted by fenestrations and branches (mean 3.7±1.0 vessels/patient). Temporary iliofemoral conduits were used in 16 limbs/14 patients. A stable MEP/SSEP was achieved in all patients. Thirty-one (63%) patients had a ≥75% decrease in MEP/SSEP amplitude in 50 limbs starting on average 75±28 minutes after obtaining vascular access. MEP/SSEP amplitude improved with maneuvers in 12 (39%) patients and returned to baseline with restoration of lower extremity flow in all except 1 patient who developed immediate SCI. Thirty-day mortality was 4%. Three (6%) patients had SCI, 2 permanent and 1 temporary at 14 days. There were no lower extremity ischemic complications. Conclusion: Neuromonitoring predicted immediate SCI and allowed use of a protocol to optimize spinal cord and lower extremity perfusion during complex endovascular aortic repair. Larger clinical experience is needed to evaluate the efficacy of neuromonitoring to prevent SCI.

Frequency and outcomes of severe hyperlactatemia after elective cardiac surgery

BACKGROUND

Hyperlactatemia is relatively common in the cardiac surgical patient and is usually considered a marker of illness severity. The frequency and impact of severe hyperlactatemia after elective cardiac surgery has not been described, and prognosis may be different compared with that for other surgical or medical critically ill patient populations.

METHODS

We conducted a retrospective study to evaluate the hospital course and outcomes of patients who developed severe postoperative hyperlactatemia (SPHL; lactate >10 mmol/L) after elective cardiac surgery, from January 1, 2008 to December 31, 2012, at a large, academic, tertiary referral center.

RESULTS

Of 9580 cardiac surgical patients who met inclusion criteria, 121 (1.26%) developed SPHL. The most common cause was cardiogenic shock (53.8%). In-hospital mortality was 40.5% but varied widely based on the cause of the SPHL. All patients with definite mesenteric ischemia (n = 5) or extremity compartment syndrome (n = 6) at the time of SPHL died in the hospital. Forty patients (33.1%) were discharged to home, whereas 32 (26.4%) were discharge to a skilled-care facility.

CONCLUSIONS

Severe postoperative hyperlactatemia is rare after elective cardiac surgery. Although this phenomenon continues to be associated with mortality, >50% of patients survived to hospital discharge, a more favorable prognosis, compared with other patient populations based on lactate levels alone. Important exceptions were patients who had extremity compartment syndrome or mesenteric ischemia, which were associated with in-hospital death in all cases. In all other etiologic groups, a substantial proportion of patients were discharged to home.

Diastolic function and new-onset atrial fibrillation following cardiac surgery

Background:

Numerous studies have reported predictors of new-onset postoperative atrial fibrillation (POAF) following cardiac surgery, which is associated with increased length of stay, cost of care, morbidity, and mortality. The purpose of this study was to examine the association between preoperative diastolic function and occurrence of new-onset POAF in patients undergoing a variety of cardiac surgeries at a single institution.

Methods:

Using data from a prospective study from November 2007 to January 2010, a retrospective review was conducted. The diastolic function of each patient was determined from preoperative transthoracic echocardiograms. Occurrence of new-onset POAF was prospectively noted for each patient in the original study. Demographic and operative characteristics of the study population were analyzed to determine predictors of POAF.

Results:

Of 223 patients, 91 (40.8%) experienced new-onset POAF. Univariate predictors of POAF included increasing age, male gender, operations involving mitral valve repair/replacement, nonsmoking, hypertension, increased intraoperative pulmonary artery pressure, grade I diastolic dysfunction, abnormal diastolic function of any grade, decreased medial e’, elevated medial E/e’, and increased left atrial volume. Multivariate predictors of POAF included increasing age, increased left atrial volume, and elevated initial intraoperative pulmonary artery pressure. Even after exclusion of patients with hypertrophic obstructive cardiomyopathy or those undergoing mitral valve operations, diastolic dysfunction was not a multivariate predictor of POAF.

Conclusions:

In the patient population studied here, preoperative diastolic dysfunction was not predictive of POAF. In addition to increasing age, initial intraoperative pulmonary artery systolic pressure and left atrial volume were both significant multivariate predictors of POAF.

Diastolic Mitral Regurgitation in a Patient With Complex Native Mitral and Aortic Valve Endocarditis: A Rare Phenomenon With Potential Catastrophic Consequences

Diastolic mitral valve regurgitation is a rare phenomenon described in patients with atrioventricular conduction abnormalities, severe left ventricular systolic or diastolic dysfunction with regional wall motion dyssynchrony, or severe acute aortic valve regurgitation. The presence of diastolic mitral valve regurgitation in acute aortic regurgitation due to endocarditis suggests critical severity requiring urgent surgical valve replacement. We describe a case of diastolic mitral regurgitation in the setting of complex native mitral-aortic valve endocarditis in a patient in normal sinus rhythm and review the etiologic mechanisms of this phenomenon, echocardiographic assessment, and therapeutic implications for hemodynamic management.

Outcome prediction in sepsis: speckle tracking echocardiography based assessment of myocardial function

Introduction

Speckle tracking echocardiography (STE) is a relatively novel and sensitive method for assessing ventricular function and may unmask myocardial dysfunction not appreciated with conventional echocardiography. The association of ventricular dysfunction and prognosis in sepsis is unclear. We sought to evaluate frequency and prognostic value of biventricular function, assessed by STE in patients with severe sepsis or septic shock.

Methods

Over an eighteen-month period, sixty patients were prospectively imaged by transthoracic echocardiography within 24 hours of meeting severe sepsis criteria. Myocardial function assessment included conventional measures and STE. Association with mortality was assessed over 12 months.

Results

Mortality was 33% at 30 days (n = 20) and 48% at 6 months (n = 29). 32% of patients had right ventricle (RV) dysfunction based on conventional assessment compared to 72% assessed with STE. 33% of patients had left ventricle (LV) dysfunction based on ejection fraction compared to 69% assessed with STE. RV free wall longitudinal strain was moderately associated with six-month mortality (OR 1.1, 95% confidence interval, CI, 1.02-1.26, p = 0.02, area under the curve, AUC, 0.68). No other conventional echocardiography or STE method was associated with survival. After adjustment (for example, for mechanical ventilation) severe RV free wall longitudinal strain impairment remained associated with six-month mortality.

Conclusion

STE may unmask systolic dysfunction not seen with conventional echocardiography. RV dysfunction unmasked by STE, especially when severe, was associated with high mortality in patients with severe sepsis or septic shock. LV dysfunction was not associated with survival outcomes.

Correlation of left ventricular systolic dysfunction determined by low ejection fraction and 30-day mortality in patients with severe sepsis and septic shock: a systematic review and meta-analysis

INTRODUCTION

The prognostic implications of myocardial dysfunction in patients with sepsis and its association with mortality are controversial. Several tools have been proposed to evaluate cardiac function in these patients, but their usefulness beyond guiding therapy is unclear. We review the value of echocardiographic estimate of left ventricular ejection fraction (LVEF) in the setting of severe sepsis and/or septic shock and its correlation with 30-day mortality.

METHODS

We conducted a systematic review and meta-analysis to evaluate the prognostic functionality of newly diagnosed LV systolic dysfunction by transthoracic echocardiography on critical ill patients admitted to the intensive care unit with severe sepsis or septic shock.

RESULTS

A search of EMBASE and PubMed, Ovide MEDLINE, and Cochrane CENTRAL medical databases yielded 7 studies meeting inclusion criteria reporting on a total of 585 patients. The pooled sensitivity of depressed LVEF for mortality was 52% (95% confidence interval [CI], 29%-73%), and pooled specificity was 63% (95% CI, 53%-71%). Summary receiver operating characteristic curve showed an area under the curve of 0.62 (95% CI, 0.58-0.67). The overall mortality diagnostic odd ratio for septic patients with LV systolic dysfunction was 1.92 (95% CI, 1.27-2.899). Statistical heterogeneity of studies was moderate.

CONCLUSION

The presence of new LV systolic dysfunction associated with sepsis and defined as low LVEF is neither a sensitive nor a specific predictor of mortality. These findings are limited because of the heterogeneity and underpower of the studies. Further research into this method is warranted.

Posterior reversible encephalopathy syndrome from induced hypertension during endovascular thoracoabdominal aortic aneurysm repair

Endovascular repair of thoracoabdominal aortic aneurysm has been increasingly performed using fenestrated and branched endografts. Spinal cord injury is a complication of complex endovascular aortic repair, especially in patients with extensive aortic involvement. Maneuvers commonly used to avoid spinal cord injury include cerebrospinal fluid drainage and induced hypertension. Posterior reversible encephalopathy syndrome is associated with abnormal cerebral autoregulation through endothelial and blood-brain barrier dysfunction; the pathophysiology involves vasogenic edema, and severe hypertension is a recognized trigger. We report on a patient who developed posterior reversible encephalopathy syndrome associated with induced hypertension used to prevent spinal cord injury during endovascular repair of a type II thoracoabdominal aortic aneurysm using fenestrated and branched stent grafts.

The perioperative management of patients with left ventricular assist devices undergoing noncardiac surgery

OBJECTIVE

To describe the perioperative management of patients with left ventricular assist devices (LVADs) who require general anesthesia while undergoing noncardiac surgery (NCS) at a single, large tertiary referral center.

PATIENTS AND METHODS

Electronic medical records from September 2, 2005, through May 31, 2012, were retrospectively reviewed to evaluate the perioperative management and outcomes in LVAD patients undergoing NCS. Patients were included only if they required a general anesthetic and had previously been discharged from the hospital after initial LVAD implantation.

RESULTS

Thirty-three patients with LVADs underwent general anesthesia for 67 noncardiac operations. The mean ± SD time from LVAD implantation to NCS was 317 ± 349 days. All but 1 patient had axial flow LVADs. Anticoagulation or antiplatelet agents were present within 7 days before NCS in 49 procedures (73%) and reversed in 32 of 49 (65%). No perioperative thrombotic complications related to anticoagulation or antiplatelet reversal were noted. Red blood cell, fresh frozen plasma, and platelet transfusions were administered during 10, 6, and 4 operations, respectively. The only intraoperative complication was surgical bleeding. Postoperative complications were present in 12 patients after NCS and were mainly composed of bleeding. Three patients died within 30 days of NCS, with the causes of death not attributed to NCS.

CONCLUSION

Patients with LVAD safely underwent NCS in a multidisciplinary setting that included preoperative optimization by cardiologists familiar with LVADs when feasible. Anticoagulation or antiplatelet agents were present preoperatively in most patients with LVADs and were safely reversed when necessary for NCS. The relatively high occurrence of postoperative bleeding is consistent with previous series.

Clinical spectrum, frequency, and significance of myocardial dysfunction in severe sepsis and septic shock

OBJECTIVE

To determine the frequency and spectrum of myocardial dysfunction in patients with severe sepsis and septic shock using transthoracic echocardiography and to evaluate the impact of the myocardial dysfunction types on mortality.

PATIENTS AND METHODS

A prospective study of 106 patients with severe sepsis or septic shock was conducted from August 1, 2007, to January 31, 2009. All patients underwent transthoracic echocardiography within 24 hours of admission to the intensive care unit. Myocardial dysfunction was classified as left ventricular (LV) diastolic, LV systolic, and right ventricular (RV) dysfunction. Frequency of myocardial dysfunction was calculated, and demographic, hemodynamic, and physiologic variables and mortality were compared between the myocardial dysfunction types and patients without cardiac dysfunction.

RESULTS

The frequency of myocardial dysfunction in patients with severe sepsis or septic shock was 64% (n=68). Left ventricular diastolic dysfunction was present in 39 patients (37%), LV systolic dysfunction in 29 (27%), and RV dysfunction in 33 (31%). There was significant overlap. The 30-day and 1-year mortality rates were 36% and 57%, respectively. There was no difference in mortality between patients with normal myocardial function and those with left, right, or any ventricular dysfunction.

CONCLUSION

Myocardial dysfunction is frequent in patients with severe sepsis or septic shock and has a wide spectrum including LV diastolic, LV systolic, and RV dysfunction types. Although evaluation for the presence and type of myocardial dysfunction is important for tailoring specific therapy, its presence in patients with severe sepsis and septic shock was not associated with increased 30-day or 1-year mortality.

A novel approach using pulmonary artery catheter-directed rapid right ventricular pacing to facilitate precise deployment of endografts in the thoracic aorta

OBJECTIVE

Controlled hypotension is critical for precise deployment of endografts in the thoracic aorta and for safe balloon dilation after deployment. We describe a novel approach to rapid right ventricular pacing using a pulmonary artery catheter (PAC) that is placed during the procedure for hemodynamic monitoring.

METHODS

The study included 27 patients (20 men and seven women), with a mean age of 74 years, who underwent endograft placement in the thoracic aorta with PAC-directed rapid right ventricular pacing. Hemodynamic parameters, accuracy of deployment, complications related to rapid right ventricular pacing and PAC placement, presence of endoleaks, and postoperative complications were evaluated.

RESULTS

PAC-directed rapid right ventricular pacing was performed during endograft deployment and balloon dilation after deployment without technical difficulty. Each patient underwent a median of two pacing episodes (range, 1-4). The length of each pacing episode was a mean of 11 seconds (range, 8-14 seconds). Mean pacing rate was 170 ± 15 beats/min, which achieved an average mean arterial pressure (MAP) of 42 ± 8 mm Hg. After pacing cessation, the recovery time of MAP to prepacing levels was <5 seconds (mean, 2 seconds) in all but one patient. All endografts were precisely deployed at a mean of 2 mm from the intended placement site, and there was no unintentional branch vessel coverage. One patient with severe valvular heart disease died. There were nine endoleaks, one postoperative stroke (4%), and one access wound hematoma (4%).

CONCLUSIONS

PAC-directed rapid right ventricular pacing is an effective method of inducing hypotension, enabling precise thoracic endograft deployment and safe balloon dilation after deployment. However, despite these advantages, the technique may be contraindicated in patients with severe valvular or ischemic heart disease.

Inhaled carbon monoxide attenuates myocardial inflammatory cytokine expression in a rat model of cardiopulmonary bypass

Carbon monoxide (CO), a by-product of Heme metabolism, is a potent modulator of inflammation. Low dose inhaled CO has demonstrated reduced lung and kidney injury in animal models of cardiopulmonary bypass (CPB). We evaluated the impact of low dose inhaled CO on systemic, pulmonary, and myocardial inflammatory response to CPB in rats. Sixteen male Sprague-Dawley rats underwent CPB for 1 hour. The CO (n = 8) group received inhaled CO at 250 ppm for 3 hours before CPB. The Air (n = 8) group served as the control. Pulmonary mechanics were assessed pre and post CPB. The animals were recovered for 30 minutes post CPB and subsequently sacrificed. Pre CPB and post CPB serum Tumor Necrosis Factor-alpha (TNF-alpha) and Interleukin-10 (IL-10) were analyzed by enzyme-linked immunosorbent assay. Gene expression array and real time quantitative polymerase chain reaction (PCR) analysis was performed on the extracted heart tissue. Baseline characteristics were similar between the groups with the expected exception of carboxyhemoglobin levels (p < or = .001) and oxyhemoglobin saturation (p < or = .01) in Air versus CO treated groups, respectively. Serum TNF-alpha (363 +/- 278 vs. 287 +/- 195;p = .13) and IL-10 (237 +/- 26 vs. 302 +/- 137; p = Not Significant) in Air versus CO groups respectively were not statistically different after CPB, despite showing a trend of inflammatory attenuation. Gene expression array of the myocardial tissue suggested a pattern of inflammatory modulation, which was confirmed by real time quantitative PCR demonstrating IL-10 expression 3.13 times higher (p = .02) in the CO treated group compared to the Air group. These data demonstrate that pretreatment with CO at 250 ppm may have a modulatory effect on the inflammatory response to CPB without compromising hemodynamics or oxygen delivery. Further investigation in a survival model of CPB is warranted.

Preoperative gabapentin for acute post-thoracotomy analgesia: a randomized, double-blinded, active placebo-controlled study

BACKGROUND

The role of preoperative gabapentin in postoperative pain management is not clear, particularly in patients receiving regional blockade. Patients undergoing thoracotomy benefit from epidural analgesia but still may experience significant postoperative pain. We examined the effect of preoperative gabapentin in thoracotomy patients.

METHODS

Adults undergoing elective thoracotomy were enrolled in this prospective, randomized, double-blinded, placebo-controlled study, and randomly assigned to receive 600 mg gabapentin or active placebo (12.5 mg diphenhydramine) orally within 2 hours preoperatively. Standardized management included thoracic epidural infusion, intravenous patient-controlled opioid analgesia, acetaminophen and ketorolac. Pain scores, opioid use and side effects were recorded for 48 hours. Pain was also assessed at 3 months.

RESULTS

One hundred twenty patients (63 placebo and 57 gabapentin) were studied. Pain scores did not significantly differ at any time point (P = 0.53). Parenteral and oral opioid consumption was not significantly different between groups on postoperative day 1 or 2 (P > 0.05 in both cases). The frequency of side effects such as nausea and vomiting or respiratory depression was not significantly different between groups, but gabapentin was associated with decreased frequency of pruritus requiring nalbuphine (14% gabapentin vs. 43% control group, P < 0.001). The frequency of patients experiencing pain at 3 months post-thoracotomy was also comparable between groups (70% gabapentin vs. 66% placebo group, P = 0.72).

CONCLUSIONS

A single preoperative oral dose of gabapentin (600 mg) did not reduce pain scores or opioid consumption following elective thoracotomy, and did not confer any analgesic benefit in the setting of effective multimodal analgesia that included thoracic epidural infusion.

WITHDRAWN: A novel approach using pulmonary artery catheter-directed rapid right ventricular pacing to facilitate precise deployment of endografts in the thoracic aorta

The Publisher regrets that this article is an accidental duplication of an article that has already been published, doi: 10.1016/j.jvs.2011.10.003. The duplicate article has therefore been withdrawn.

Use of paravertebral blockade to facilitate early extubation after minimally invasive cardiac surgery

We retrospectively reviewed the first 14 patients who received preoperative paravertebral blockade prior to minimally invasive cardiac surgical procedures. The use of paravertebral blockade along with an anesthetic technique designed to facilitate rapid recovery allowed early extubation in the operating room or intensive care unit in all but one patient. Extubated patients leaving the operating room were comfortable. No postoperative respiratory complications occurred.

Impairment of diaphragm muscle force and neuromuscular transmission after normothermic cardiopulmonary bypass: effect of low-dose inhaled CO

Cardiopulmonary bypass (CPB) is associated with significant postoperative morbidity, but its effects on the neuromuscular system are unclear. Recent studies indicate that even relatively short periods of mechanical ventilation result in significant neuromuscular effects. Carbon monoxide (CO) has gained recent attention as therapy to reduce the deleterious effects of CPB. We hypothesized that 1) CPB results in impaired neuromuscular transmission and reduced diaphragm force generation; and 2) CO treatment during CPB will mitigate these effects. In adult male Sprague-Dawley rats, diaphragm muscle-specific force and neuromuscular transmission properties were measured 90 min after weaning from normothermic CPB (1 h). During CPB, either low-dose inhaled CO (250 ppm) or air was administered. The short period of mechanical ventilation used in the present study ( approximately 3 h) did not adversely affect diaphragm muscle contractile properties or neuromuscular transmission. CPB elicited a significant decrease in isometric diaphragm muscle-specific force compared with time-matched, mechanically ventilated rats ( approximately 25% decline in both twitch and tetanic force). Diaphragm muscle fatigability to 40-Hz repetitive stimulation did not change significantly. Neuromuscular transmission failure during repetitive activation was 60 +/- 2% in CPB animals compared with 76 +/- 4% in mechanically ventilated rats (P < 0.05). CO treatment during CPB abrogated the neuromuscular effects of CPB, such that diaphragm isometric twitch force and neuromuscular transmission were no longer significantly different from mechanically ventilated rats. Thus, CPB has important detrimental effects on diaphragm muscle contractility and neuromuscular transmission that are largely mitigated by CO treatment. Further studies are needed to ascertain the underlying mechanisms of CPB-induced neuromuscular dysfunction and to establish the potential role of CO therapy.

A population-based study of mortality among patients with atrial fibrillation or flutter

PURPOSE

To determine the mortality associated with atrial flutter and atrial fibrillation in the general population.

SUBJECTS AND METHODS

Using the Marshfield Epidemiologic Study Area, a database that captures nearly all medical care and deaths among its 58,820 residents, we identified patients diagnosed with atrial flutter or atrial fibrillation from July 1, 1991, through June 30, 1995. Patients were followed prospectively and compared with a group of controls without these arrhythmias.

RESULTS

A total of 4775 person-years of follow-up were completed in 577 patients and 577 controls. Compared with controls, mortality among patients with atrial fibrillation or flutter was nearly 7.8-fold higher at 6 months (95% confidence interval [CI]: 4.1 to 15) and 2.5-fold higher (95% CI: 2.0 to 3.1; P < 0.0001) at the last follow-up (mean [+/- SD] of 3.6 +/- 2.3 years; range, 1 day to 7.3 years). At 6 months, mortality among patients with atrial flutter alone was somewhat greater than in controls and less than one third that of those with atrial fibrillation (with or without atrial flutter) (P = 0.02). At the last follow-up, however, mortality was greater among patients with atrial flutter (hazard ratio [HR] = 1.7; 95% CI: 1.2 to 2.6; P = 0.007), atrial fibrillation (HR = 2.4; 95% CI: 1.9 to 3.1; P < 0.0001), or both atrial arrhythmias (HR = 2.5; 95% CI: 1.9 to 3.3; P < 0.0001) when compared with controls in models that adjusted for cardiovascular risk factors.

CONCLUSION

In the general population, both atrial flutter and atrial fibrillation are independent predictors of increased late mortality. The relatively benign course during the 6-month period after the initial diagnosis of atrial flutter suggests that early diagnosis and treatment of these patients may improve their long-term survival.