Diastolic Function and Peripheral Venous Pressure as Indices for Fluid Responsiveness in Cardiac Surgical Patients.

OBJECTIVE: Identifying fluid responsiveness is critical to optimizing perfusion while preventing fluid overload. An experimental study of hypovolemic shock resuscitation showed the importance of ventricular compliance and peripheral venous pressure (PVP) on fluid responsiveness. The authors tested the hypothesis that reduced ventricular compliance measured using transesophageal echocardiography results in decreased fluid responsiveness after a fluid bolus. DESIGN: Prospective observational study. SETTING: Two-center, university hospital study. PARTICIPANTS: The study comprised 29 patients undergoing elective coronary revascularization. INTERVENTION: Albumin 5%, 7 mL/kg, was infused over 10 minutes to characterize fluid responders (>15% increase in stroke volume) from nonresponders. MEASUREMENTS AND MAIN RESULTS: Invasive hemodynamics and the ratio of mitral inflow velocity (E-wave)/annular relaxation (e'), or E/e' ratio, were measured using transesophageal echocardiography to assess left ventricular (LV) compliance at baseline and after albumin infusion. Fifteen patients were classified as responders and 14 as nonresponders. The E/e' ratio in responders was 7.4 ± 1.9 at baseline and 7.1 ± 1.8 after bolus. In contrast, E/e' was significantly higher in nonresponders at baseline (10.7 ± 4.6; p = 0.04) and further increased after bolus (12.6 ± 5.5; p = 0.002). PVP was significantly greater in the nonresponders at baseline (14 ± 4 mmHg v 11 ± 3 mmHg; p = 0.02) and increased in both groups after albumin infusion. Fluid responsiveness was tested using the area under the receiver operating characteristic curve and was 0.74 for the E/e' ratio (95% confidence interval 0.55-0.93; p = 0.029) and 0.72 for the PVP (95% confidence interval 0.52-0.92; p = 0.058). CONCLUSION: Fluid responders had normal LV compliance and lower PVP at baseline. In contrast, nonresponders had reduced LV compliance, which worsened after fluid bolus. E/e,' more than PVP, may be a useful clinical index to predict fluid responsiveness.

Peripheral Venous Pressure as an Indicator of Preload Responsiveness During Volume Resuscitation from Hemorrhage.

BACKGROUND: Fluid resuscitation of hypovolemia presumes that peripheral venous pressure (PVP) increases more than right atrial pressure (RAP), so the net pressure gradient for venous return (PVP-RAP) rises. However, the heart and peripheral venous system function under different compliances that could affect their respective pressures during fluid infusion. In a porcine model of hemorrhage resuscitation, we examined whether RAP increases more than PVP, thereby reducing the venous return pressure gradient and blood flow. METHODS: Anesthetized pigs (n = 8) were bled to a mean arterial blood pressure of 40 mm Hg and resuscitated with stored blood and albumin for pulmonary artery occlusion pressures (PAOPs) of 5, 10, 15, and 20 mm Hg. Venous pressures, inferior vena cava blood flow (ultrasonic flowprobe), and left ventricular diastolic compliance (Doppler echocardiography) were measured. Stroke volume variability was calculated. RESULTS: With volume resuscitation, the slope of RAP exceeded PVP (P ≤ 0.0001) when PAOP is 10 to 20 mm Hg, causing the pressure gradient for venous return to progressively decrease. Inferior vena cava blood flow did not further increase after PAOP > 10 mm Hg. The E/e' ratio increased (P = 0.001) during resuscitation indicating reduced diastolic compliance. A significant curvilinear relationship was found between PVP and stroke volume variability (R = 0.62; P < 0.001), where fluid responders had PVP < 15 mm Hg. CONCLUSIONS: Fluid resuscitation above a PAOP 10 mm Hg reduces myocardial compliance and reduces the venous return pressure gradient. The hemodynamic response to fluid resuscitation becomes limited by diastolic properties of the heart. PVP measurement during hemorrhage resuscitation may predict fluid responsiveness and nonresponsiveness.

Effect of increasing heart rate and tidal volume on stroke volume variability in vascular surgery patients.

OBJECTIVE: Because heart rate affects ventricular filling, the aim of the present study was to assess the effects of increasing heart rate and tidal volume on stroke volume variability to determine whether this dynamic index is heart-rate dependent. DESIGN: Prospective, randomized study. SETTING: Single university hospital. PARTICIPANTS: Eighteen vascular surgery patients having general anesthesia and endotracheal intubation with an arterial catheter connected to the Vigileo FloTrac system (Edwards Lifesciences, Irvine, CA) and a transesophageal atrial pacemaker (CardioComman Inc, Tampa, FL). INTERVENTION: A 2 × 2 factorial study of changes in heart rate (80 bpm and 110 bpm) and tidal volume (6 mL/kg and 10 mL/kg). MEASUREMENTS AND MAIN RESULTS: With tidal volume at 6 mL/kg, increasing heart rate from 80 mL/kg to 110 bpm caused stroke volume variability to increase from 12.2% ± 5.7% to 13.2% ± 5.3% (p<0.05), and with tidal volume at 10 mL/kg, increasing heart rate from 80 mL/kg to 110 bpm caused stroke volume variability to increase from 19.7% ± 7.9% to 22.0% ± 8.6% (p<0.05). In comparison, increasing tidal volume from 6 mL/kg to 10 mL/kg produced a significantly greater effect on stroke volume variability than increasing heart rate. CONCLUSIONS: Stroke volume variability is sensitive to increases in heart rate in addition to tidal volume. Increasing heart rate caused stroke volume variability to increase significantly, although not to the same magnitude as increasing tidal volume. When using dynamic volume indices, clinicians should be aware of increases in heart rate, although its clinical impact may be relatively minor compared with changes in tidal volume.

Biventricular pacing in conjunction with epicardial atrial pacing adversely affects timing of intra-aortic balloon pump.

A case of accidental triggering of an intra-aortic balloon pump during systole is presented. The patient had a cardiac resynchronization therapy device in place preoperatively for heart failure. A temporary epicardial atrial pacing wire was used during separation from cardiopulmonary bypass for rate control. An intra-aortic balloon pump was necessary for separation from bypass. Although the pacemaker functioned properly, the intra-aortic balloon triggered from the atrial pacing spike and was inflated during systole. Pacemaker and intra-aortic balloon electronics and timing settings that caused this are discussed in detail. Suggestions for prevention are presented.

Age-dependent differences of interleukin-6 activity in cardiac function after burn complicated by sepsis.

Interleukin (IL)-6 is a pleiotropic cytokine that is activated after acute injuries, and plays an important role during aging. We aim to define the role of IL-6 on myocardial dysfunction following a 40% total body surface area burn followed by late (7 days) Streptococcus pneumoniae sepsis (burn plus sepsis) in 2- and 14-month-old wild type and IL-6(-/-) mice. We measured global hemodynamic and cardiac contractile function with left ventricular pressure-volume analysis 24h after sepsis induction, and measured phosphorylated signal transducer and activator of transcription 3 (p-STAT-3), tumor necrosis factor (TNF)-alpha, and IL-1beta in the heart with Western blot analysis. We also measured mRNA expression of IL-6, TNF-alpha, and IL-1beta. Sham injured mice did not manifest any appreciable level of p-STAT-3 or functional deficiencies regardless of age or presence of the IL-6 gene. Burn plus sepsis injury was associated with a significant deterioration of global hemodynamic and cardiac contractile function in WT mice in both age groups. This dysfunction was attenuated by IL-6 deficiency at age 2 months, but accentuated at age 14 months. Aging was associated with an increase in mRNA expression of IL-6 (WT mice), TNF-alpha, and IL-1beta (all mice). At age 14 months, IL-6 deficient mice exhibited a greater TNF-alpha mRNA expression than the wild type mice. We conclude aging is associated with changed cytokine gene transcription, and burn plus sepsis injury further intensifies such gene responses. IL-6 deficiency does not abrogate STAT-3 phosphorylation and it may enhance expression of other inflammatory cytokines. The differential effects of IL-6 deficiency on the cardiac function in young and aging mice cannot be explained by cytokine gene expression alone, and require further studies.

Intraoperative fluid restriction predicts improved outcomes in major vascular surgery.

BACKGROUND: Traditional fluid resuscitation during general anesthesia has been questioned in recent studies. One study of patients undergoing abdominal surgery showed decreased postoperative weight gain, earlier return of bowel function, and shorter intensive care unit (ICU) and hospital length of stay (LOS) when intraoperative crystalloid infusion was restricted. The authors conducted a retrospective study of major vascular surgery patients (neo-aorto iliac system surgery) to correlate clinical outcomes with intraoperative crystalloid fluid administration. METHODS: The charts of 41 patients who underwent major vascular surgery at our institution were reviewed. Patients were grouped according to the crystalloid volume infused intraoperatively into <3 L (group 1) and >3 L (group 2). Preoperative and postoperative weights, intraoperative crystalloid administration, intraoperative vasopressor use, preoperative and postoperative creatinine, number of days to clear liquid diet, and the time to discharge from the ICU (ICU LOS) and hospital (hospital LOS) were collected. RESULTS: There were statistically significant differences in duration of mechanical ventilation (0.55 +/- 0.934 vs 2.03 +/- 2.735 days, P = .013) and ICU LOS (3.0 +/- 1.48 vs 5.79 +/- 3.938, P = .029) in favor of the fluid restriction group. Major postoperative complications, such as sepsis, acute myocardial infarction, and graft thrombosis, were less frequent in the fluid restriction group but not statistically significant (5 vs 9, P = .742). Intraoperative crystalloid volume was found to be an independent predictor of ICU LOS after adjusting for estimated blood loss and duration of surgery. There was no statistically significant difference in preoperative serum albumin in both groups. CONCLUSIONS: Restricted intraoperative administration of crystalloid fluids (<3 L) may be beneficial in major vascular surgery patients. These benefits are similar to those previously described in patients undergoing abdominal surgery.

Role of interleukin-6 in cardiac inflammation and dysfunction after burn complicated by sepsis.

To examine the role of myocardial interleukin-6 (IL-6) in myocardial inflammation and dysfunction after burn complicated by sepsis, we performed 40% total body surface area contact burn followed by late (7 days) Streptococcus pneumoniae pneumonia sepsis in wild-type (WT) mice, IL-6 knockout (IL-6 KO) mice, and transgenic mice overexpressing IL-6 in the myocardium (TG). Twenty-four hours after sepsis was induced, isolated cardiomyocytes were harvested and cultured in vitro, and supernatant concentrations of IL-6 and tumor necrosis factor (TNF)-alpha were measured. Cardiomyocyte intracellular calcium ([Ca(2+)](i)) and sodium ([Na(+)](i)) concentrations were also determined. Separate mice in each group underwent in vivo global hemodynamic and cardiac function assessment by cannulation of the carotid artery and insertion of a left ventricular pressure volume conductance catheter. Hearts from these mice were collected for histopathological assessment of inflammatory response, fibrosis, and apoptosis. In the WT group, there was an increase in cardiomyocyte TNF-alpha, [Ca(2+)](i), and [Na(+)](i) after burn plus sepsis, along with cardiac contractile dysfunction, inflammation, and apoptosis. These changes were attenuated in the IL-6 KO group but accentuated in the TG group. We conclude myocardial IL-6 mediates cardiac inflammation and contractile dysfunction after burn plus sepsis.

Independent study and performance on the anesthesiology in-training examination.

Intuitively, independent study by residents would be expected to improve performance on the in-training examination (ITE). So far, however, studies that have examined this issue have used historical controls and have not evaluated the amount of personal study and its impact on performance. We therefore examined the relationship between the amount of self-reported time devoted to personal study by 36 clinical anesthesia year 1 and 2 residents at the University of Texas Southwestern Medical Center, and their scores on the ITE administered in July 2003. The average time spent in self-study was 8 +/- 3.6 hours per week, and the average scaled score was 28.7 +/- 7.3. Linear regression analysis revealed a positive correlation between hours spent in self-study per week and scaled score performance on the ITE (correlation coefficient = 0.64, P < 0.0001), where the ITE scaled score = (1.3) (hours of self-study per week) + 18.4. Our findings emphasize the importance of personal study by residents. In conjunction with our diverse clinical and didactic experience, these findings indicate that anesthesiology residents who invest a minimum of 10.5 hours of personal study per week are well positioned to achieve a passing score on the ITE.

Murine in vivo myocardial contractile dysfunction after burn injury is exacerbated by pneumonia sepsis.

We evaluated hemodynamic and cardiac contractile dysfunction in a murine model of 40% contact burn complicated by Streptococcus pneumoniae (1 x 10(5) CFU) sepsis. Male, 9- to 10-week-old C57/BL6 mice were divided into the following groups: sham burn, sham sepsis; 24 h after burn alone; 24 h after sepsis alone; 7 days after burn alone; and 7 days after burn followed by pneumonia sepsis. Hemodynamic and cardiac contractile function was assessed with carotid artery cannulation and left ventricular pressure-volume analysis. At 24 h after burn, there were significant decreases in all load-insensitive contractility variables including the end-systolic pressure volume relationship, preload-recruitable stroke work, and maximum elastance, but there were no changes in global hemodynamics. Twenty-four hours after sepsis, there was similar cardiac contractile dysfunction, along with a decrease in cardiac output, but mean arterial pressure was maintained with an increase in systemic vascular resistance. Late burn (7 days) was associated with a recovery of all contractility variables except the end-systolic pressure volume relationship. However, sepsis induced during the late burn period was associated with a significant decrease in heart rate and cardiac output, but mean arterial pressure was still maintained with increased systemic vascular resistance. With burn complicated by sepsis, all cardiac contractility variables showed profound contractile dysfunction. Our data indicate that burn complicated by sepsis is associated with more pronounced cardiac contractile dysfunction than burn alone or sepsis alone.

Cardiovascular dysfunction caused by cecal ligation and puncture is attenuated in CD8 knockout mice treated with anti-asialoGM1.

The present study was designed to assess hemodynamics and myocardial function at 18 h after injury caused by cecal ligation and puncture (CLP) in CD8-knockout mice treated with anti-asialoGM1 (CD8KO/alphaAsGM1 mice). Arterial pressure was measured by carotid artery cannulation, and left ventricular pressure-volume measurements were obtained by use of a 1.4-Fr conductance catheter. Blood acid-base balance and indexes of hepatic, renal, and pulmonary injury were also measured. CD8KO/alphaAsGM1 mice exhibited higher mean arterial pressure and increased systemic vascular resistance compared with wild-type mice. Cardiac output was significantly decreased in wild-type, but not CD8KO/alphaAsGM1, mice compared with sham controls. Myocardial function was better preserved in CD8KO/alphaAsGM1 mice as indicated by less impairment of left ventricular pressure development over time, time varying maximum elastance, end-systolic pressure-volume relationship, and preload recruitable stroke work. The impairment in myocardial function was associated with induction of proinflammatory cytokine mRNAs in the hearts of wild-type mice. The hemodynamic derangements in wild-type mice were coupled with significant metabolic acidosis and elevated serum creatinine levels. Overall, this study shows that cardiovascular collapse and shock characterized by hypotension, myocardial depression, low systemic vascular resistance, and metabolic acidosis occurs after CLP in wild-type mice but is attenuated in CD8KO/alphaAsGM1 mice. These observations likely explain, in part, the previously observed survival advantage of CD8KO/alphaAsGM1 mice following CLP.

The prevalence and characteristics of incentive plans for clinical productivity among academic anesthesiology programs.

Performance-based compensation is encouraged in medical schools to improve faculty productivity. Medical specialties other than anesthesiology have used financial incentives for clinical work. The goal of this study was to determine the prevalence and the types of clinical incentive plans among academic anesthesiology departments. We performed an electronic survey of the members of the Society of Academic Anesthesiology Chairs and the Association of Anesthesiology Program Directors in the spring of 2003. The survey included questions about departmental size, presence of a clinical incentive plan, characteristics of existing incentive plans, primary quantifiers of productivity, and factors used to modify productivity measurements. An incentive plan was considered to be present if the department measured clinical productivity and varied compensation according to the measurements. The plans were grouped by the primary measure used into the following categories: None, Charges, Time, Shift, Late/Call (only late rooms and call), and Other. Eighty-eight (64%) of 138 programs responded to the survey, and 5 were excluded for incomplete data. Of the responding programs, 29% had no system, 30% used a Late/Call system, 20% used a Shift system, 11% used a Charges system, 6% used a Time system, and 3% fit in the Other category. Larger groups (>40 faculty members) had a significantly more frequent prevalence of incentive plans compared with smaller groups (<20 faculty members). Incentives were paid monthly or quarterly in 85% of the groups. In 90% of groups, incentive payments accounted for <25% of total compensation. Adjustments for operating room schedule supervisors, personally performed cases, day surgery preoperative clinics, pain-management services, and critical care services were included in less than half of the programs that reported incentive plans. Call and late room compensation was based on varied formulas. Sixty-nine percent of academic anesthesiology departments did not vary compensation according to clinical activity during regular hours. Most did vary payments on the basis of call and/or late rooms worked. Larger departments were more likely to use clinical incentive plans.

Hemodynamic and cardiac contractile function during sepsis caused by cecal ligation and puncture in mice.

Sepsis is among the leading causes of death in the critically ill, yet the pathophysiology of sepsis is incompletely understood. Genetically engineered mice offer a unique opportunity to explore the cellular and molecular pathogenesis of sepsis. However, the hemodynamic responses of mice during sepsis are not completely understood because of the difficulty in performing cardiovascular measurements in mice. We used a 1.4-F pressure and conductance catheter to measure hemodynamics in wild-type C57BL/6J mice during sepsis caused by cecal ligation and puncture. Septic mice exhibited significant hypothermia compared with the sham group. In addition, there was a progressive decrease in mean arterial blood pressure and systemic vascular resistance in septic mice as well as an increase in stroke volume and cardiac output. Sepsis also caused a significant time-dependent impairment of left ventricular function as indicated by decreased dp/dtmax and dp/dtmin. The slope of end systolic pressure volume relationship also decreased over time, as did the time varying maximum elastance and preload-recruitable stroke work of the left ventricle. In conclusion, septic mice exhibit hemodynamic alterations during sepsis that are similar to those observed in humans. The miniaturized conductance catheter allows for effective measurements of hemodynamic function in septic mice and provides measurements that cannot be obtained using other cardiovascular monitoring techniques.

Hemodynamic benefit of positive end-expiratory pressure during acute descending aortic occlusion.

BACKGROUND: Acute aortic occlusion in vascular surgery patients abruptly increases arterial resistance and blood pressure, which, in turn, makes subsequent volume expansion during cross-clamp application difficult. The use of vasodilatory drugs or volatile anesthetic agents to attenuate this response may have persistent detrimental effects after clamp removal. Another potential therapy that produces rapid effects on myocardial loading conditions is positive end-expiratory pressure (PEEP). In a porcine model of acute aortic clamping, the hemodynamic consequences of 15 cm H(2)O PEEP with and without plasma volume expansion were studied.(2) METHODS: Forty anesthetized pigs underwent 30-min occlusion of the abdominal aorta 1 cm above the origin of the celiac artery. Animals were randomly divided into four treatment groups (n = 10 each) to receive 15 cm H(2)O PEEP or zero end-expiratory pressure (ZEEP) with or without plasma volume expansion using 6% hetastarch (10 ml/kg) during cross-clamp application. Mean aortic pressure was measured with a transducer-tipped catheter placed in the ascending aorta; stroke volume was calculated using thermodilution cardiac output. End-expiratory pressure was discontinued upon aortic declamping, and animals were studied over the ensuing 30-min period. RESULTS: Aortic occlusion doubled systemic vascular resistance in all groups. Mean aortic blood pressure increased significantly in both ZEEP groups at 1 and 5 min but not in animals treated with 15 cm H(2)O PEEP. The application of PEEP with aortic cross-clamping reduced cardiac output and stroke volume by nearly 50%. Cardiac output and stroke volume increased after volume expansion regardless of end-expiratory pressure. After aortic declamping, aortic blood pressure decreased in all groups but was significantly greater in the PEEP + volume group than in either ZEEP group. Similarly, 5 min after declamping, stroke volume was greatest in the PEEP + volume animals. CONCLUSIONS: Fifteen cm H(2)O PEEP reduces the hypertensive response to acute aortic occlusion and allows concomitant volume expansion. Consequently, stroke volume and blood pressure are better maintained after clamp removal in PEEP + volume animals. The use of PEEP during acute aortic occlusion in patients may allow rapid control of loading conditions to attenuate systemic hypertension while permitting simultaneous volume expansion.