Increased plasma concentrations of serum amyloid A: an indicator of the acute-phase response after cardiopulmonary bypass

The gut microbiome and cardiac surgery an unusual symphony

The relationship between the gut microbiome and various organ systems has gained interest throughout the scientific community in recent times. The understanding of these complex relationships has greatly improved with clinical benefits now being seen. Cardiopulmonary bypass (CPB) is a form of extracorporeal circulation that provides circulatory and respiratory support during cardiac surgery. This physiological support facilitates a still and bloodless field facilitating operations on the heart to be performed. Through various mechanisms CPB results in a systemic inflammatory response syndrome (SIRS). This response can vary from mild hypotension to multiple organ failure. It remains difficult to predict the degree to which a patient will experience SIRS post-operatively. The relationship between the composition of the gut microbiome and inflammatory processes associated with disease has been seen across several fields including gastroenterology, neurology, psychiatry and cardiology. To date, minimal research has been undertaken to examine the impact the gut microbiome has on outcomes following cardiac surgery. This review paper explores the pathophysiology behind the SIRS response associated with CPB for cardiac surgery and the hypothesis that a correlation exists between a patients gut microbiome composition and the degree of inflammatory response experienced following cardiac surgery.

Endotoxin Activity in Neonates Undergoing Cardiac Surgery: Cohort Study

BACKGROUND

Endotoxemia in pediatric cardiac surgical patients is poorly understood. The endotoxin activity assay (EAA) levels were examined in neonates undergoing cardiac surgery in order to assess their reference levels and their association with other pre-, intra-, and postoperative risk factors for gut hypoperfusion. We finally observed if refeeding was associated with modification of endotoxin levels.

METHODS

In a prospective cohort study, neonates undergoing surgery for correction or palliation were enrolled. Preterm birth, weight below 1.5 kg, the need for extracorporeal membrane oxygenation, and urgent surgery were exclusion criteria.

RESULTS

Among the 26 enrolled neonates, 12 underwent on-pump and 14 off-pump surgery, 22 received a preoperative infusion of prostaglandin E2. Overall, 11 patients were surgically corrected and 15 received a palliation. Endotoxin activity assay baseline levels were inversely correlated with age at surgery ( r = -.50, P = .006) and they increased to postoperative day2 ( P = .002). On-pump versus off-pump surgery ( P =.36) and surgical palliation with a Blalock-Taussig shunt versus correction ( P = .45) did not predict increase in EAA levels. Aortic clamping for coarctation repair was associated with the lowest levels ( P = .04). Systolic, mean, and diastolic pressures were associated with EAA levels ( r = -.55, P = .01; r = -.45, P = .02; r = -.37, P = .04, respectively). Endotoxin activity assay levels after refeeding were similar to baseline levels. Patients with abdominal distension and feeding intolerance showed higher median peak EAA levels (0.7, 0.66-1.11) than asymptomatic patients (0.53, 0.35-0.64; P = .01).

CONCLUSIONS

Endotoxin activity assay levels increase after elective neonatal surgery and are not modified by refeeding. High postoperative levels may predict feeding intolerance.

Periodontitis in humans and non-human primates: oral-systemic linkage inducing acute phase proteins

BACKGROUND

The acute phase response (APR) represents a systemic counterpart to the localized inflammatory response. This report describes patient-oriented and non-human primate model studies to determine the effect of periodontal disease on systemic acute phase proteins (APP).

METHODS

Patient-oriented studies included comparison of the levels of APP, using enzyme-linked immunosorbent assay (ELISA), with the presence and severity of periodontitis in localized chronic periodontitis (LCP), generalized aggressive periodontitis (GAP), and Sjogren's syndrome (SS) patients. The non-human primate experiments evaluated the serum level of APPs under natural conditions, following mechanical hygiene, experimental gingivitis, and during ligature-induced periodontitis.

RESULTS

Analysis of the LCP population showed what appeared to be a threshold of periodontal disease severity required for elevating the C-reactive protein (CRP) and haptoglobin (HG). The results demonstrated a significant elevation in CRP in the GAP versus the control groups, as well as lower levels of all mediators in healthy non-smokers (HNS) versus smokers (HS), suggesting that these systemic inflammatory markers were altered in response to challenge by noxious materials from smoking. Significantly different levels of CRP, HG, and alpha1-antiproteinase were noted in the SS patients suggesting that the autoimmune aspects of Sjögren's syndrome may impact upon oral health and systemic responses. Parallel evidence was also obtained from the primate studies. Providing mechanical oral hygiene, which significantly lowered clinical inflammation and bleeding of the gingiva, decreased the serum APP levels. Both CRP and fibrinogen were significantly elevated during progressing periodontitis, which also appeared to have an impact on serum lipids and lipoproteins.

CONCLUSIONS

These findings supported results relating chronic oral infections and the inflammation of periodontitis as contributors to and/or triggers for systemic inflammatory responses. Finally, similarities in the clinical and microbiological parameters of gingival inflammation and periodontitis between humans and non-human primates was extended to identification of changes in serum APP in the non-human primates that appeared to be in direct response to the induction of progressing periodontitis. These systemic changes provide additional evidence for the biological plausibility of periodontal infections contributing to various systemic diseases.

Proinflammatory cytokines are increased in type 2 diabetic women with cardiovascular disease

Diabetics have a much greater morbidity and mortality due to cardiovascular disease (CVD) than nondiabetics. Furthermore, diabetic women have a 3.8-fold greater risk for CVD compared to diabetic men. Inflammation is now considered a risk factor for CVD and it has been demonstrated that inflammation also plays a role in diabetes. One component of inflammation that has reported to be increased in patients with diabetes only and CVD only are proinflammatory cytokines, particularly interleukin-6 (IL-6), tumor necrosis factor (TNF-alpha), and interleukin-1 (IL-1beta). This study was performed to test the hypothesis that these proinflammatory cytokines were increased in women with CVD and further increased in diabetic women with CVD compared to nondiabetic women with CVD and healthy age-matched controls. We found that IL-6 was increased in diabetic women with CVD compared to healthy age-matched controls (1.41 = 0.48 to 0.33 +/- 0.06 pg/ml, P < .05). IL-6 was also increased in diabetic women without CVD compared to healthy age-matched controls, but not significantly (0.96 +/- 0.27 to 0.33 +/- 0.06 pg/ml). We found that TNF-alpha was increased in diabetic women with and without CVD compared to healthy age-matched controls, but not significantly (4.53 +/- 1.38 to 3.93 +/ -0.53 to 2.33 +/- 0.89 pg/ml). IL-1beta was not significantly different among any of the four groups of women. These results indicate that both IL-6 and TNF-alpha are chronically increased in diabetic women with and without CVD compared to nondiabetic women. The additive concentration of cytokines in diabetes and CVD suggests a common inflammatory state in both diabetes and CVD.

Procalcitonin and C-reactive protein kinetics in postoperative pediatric cardiac surgical patients

OBJECTIVE

To determine the kinetics of procalcitonin (PCT) and C-reactive protein (CRP) concentration after pediatric cardiac surgery with cardiopulmonary bypass.

DESIGN

Prospective, clinical cohort study.

SETTING

A fifteen-bed tertiary-care pediatric intensive care unit.

PATIENTS

Fourteen pediatric patients admitted for cardiac surgery.

MEASUREMENTS AND MAIN RESULTS

Serum PCT and CRP were measured before cardiopulmonary bypass (CPB); after CPB; and on the first, second, and third days after surgery by means of immunoluminometry and nephelometry, respectively. Reference values for systemic inflammatory response syndrome are 0.5 to 2.0 ng/mL for PCT and <5 mg/L for CRP. Baseline serum PCT and CRP concentrations were 0.24 +/- 0.13 ng/mL and 4.06 +/- 3.60 mg/L (median 25th percentile-75th percentile), respectively. PCT concentrations increased progressively from the end of CPB (0.62 +/- 0.30 ng/mL), peaked at 24 hours postoperatively (POD1) (0.77 +/- 0.49 ng/mL), and began to decrease at 48 hours or POD2 (0.35 +/- 0.21 ng/mL). CRP increased just after CPB (58.82 +/- 42.23 mg/L) and decreased after 72 hours (7.09 +/- 9.81 mg/L).

CONCLUSION

An increment of both PCT and CRP was observed just after CPB. However, PCT values remained within reference values, whereas CRP concentrations increased significantly after CPB until the third day. These preliminary results suggest that PCT was more effective than CRP to monitor patients with SIRS and a favorable outcome.

Endogenous glycosides in critically ill patients

OBJECTIVE

To determine the incidence of critically ill patients displaying endogenous digitalis-like-immunoreactive substances (DLIS) and to examine the relationship of these hormones to routine laboratory variables, the underlying disease, myocardial function, hemodynamic status, severity of illness, systemic inflammation, and mortality rate.

DESIGN

Sera of 401 consecutive critically ill patients, not treated with cardiac glycosides, were analyzed for DLIS (digitoxin and digoxin, TDx; Abbott Diagnostics, North Chicago, IL) and endogenous ouabain. Normal values of endogenous ouabain were determined in 62 healthy volunteers. We measured pro- and anti-inflammatory mediators (L-selectin, tumor necrosis factor-alpha, interleukin-1beta, interleukin-2, interleukin-6, interleukin-10), C-reactive protein, and serum amyloid A protein as well as patients' Acute Physiology and Chronic Health Evaluation II and Goris scores. In a subgroup of patients with a pulmonary artery catheter (n = 95), we determined cardiac output, pulmonary artery occlusion pressure, systemic and pulmonary vascular resistance, left ventricular stroke volume, and right and left stroke work.

SETTING

Two surgical intensive care units of an university hospital.

SUBJECTS

Sera of 401 consecutive critically ill patients.

INTERVENTIONS

Blood sampling.

MEASUREMENTS AND MAIN RESULTS

Of the 401 patients tested, 343 had nonmeasurable DLIS concentrations (DLIS-negative), and 58 (14.5%) had positive digoxin (n = 18) or digitoxin (n = 34) concentrations (DLIS-positive) or were positive in both tests (n = 6). Mean endogenous ouabain concentrations were nine-fold increased in DLIS-positive (3.59 +/- 1.43 nmol/L) and three-fold increased in DLIS-negative (1.34 +/-.81 nmol/L) patients compared with controls (0.38 +/- 0.31 nmol/L). DLIS and ouabain concentrations closely correlated with the Acute Physiology and Chronic Health Evaluation II and Goris score and were associated with increased concentrations of transaminases, bilirubin, aldosterone, cortisol, serum creatinine, fractional sodium excretion, proinflammatory mediators, C-reactive protein, and serum amyloid A (p <or=.009). The hospital mortality rates of DLIS-positive and DLIS-negative patients were 12% and 3.2%, respectively, and for patients with ouabain concentrations above and below 2 nmol/L 38.6% and 0.6%, respectively. In DLIS-positive patients with pulmonary artery catheter (n = 23), cardiac output, stroke volume, and left ventricular stroke work were decreased, and pulmonary artery occlusion pressure and central venous pressure were increased (p <or=.009).

CONCLUSIONS

Different types of endogenous glycosides including endogenous ouabain are elevated in a significant proportion of critically ill patients. The occurrence of these substances is associated with increased morbidity and hospital mortality rates, possibly due to systemic inflammatory processes. DLIS but not endogenous ouabain concentrations were found to be related to left ventricular function.

Serum amyloid A and high-density lipoprotein cholesterol: serum markers of inflammation in sarcoidosis and other systemic disorders

Hypocholesterolemia has been observed in several inflammatory diseases such as rheumatoid arthritis, myeloproliferative disorders, systemic lupus erythematosus and sarcoidosis. Serum amyloid A is an acute-phase reactant that is related to the high-density lipoprotein cholesterol. This review discusses the relationship between the activation of the cells of the monocyte-macrophage system, determined by the serum amyloid A levels, and the lipid metabolism, measured as alterations in plasma lipoprotein concentrations. The mechanisms of this association during acute inflammation are also discussed in this review.

Jejunal mucosal perfusion is well maintained during mild hypothermic cardiopulmonary bypass in humans

In the present study, the effects of mild hypothermic (34 degrees C) cardiopulmonary bypass (CPB) on jejunal mucosal perfusion (JMP), gastric tonometry, splanchnic lactate, and oxygen extraction were studied in low-risk cardiac surgical patients (n = 10), anesthetized and managed according to clinical routine. JMP was assessed by endoluminal laser Doppler flowmetry. Patients were studied during seven 10-min measurement periods before, during, and 1 h after the end of CPB. Splanchnic oxygen extraction increased during hypothermia and particularly during rewarming and warm CPB. JMP increased during hypothermia (26%), rewarming (31%), and warm CPB (38%) and was higher 1 h after CPB (42%), compared with pre-CPB control. The gastric-arterial PCO(2) difference was slightly increased (range 0.04-2.26 kPa) during rewarming and warm CPB as well as 1 h after CPB, indicating a mismatch between gastric mucosal oxygen delivery and demand. None of the patients produced lactate during CPB. We conclude that jejunal mucosal perfusion appears well preserved during CPB and moderate (34 degrees C) hypothermia; this finding is in contrast to previous studies showing gastric mucosal hypoperfusion during CPB.

IMPLICATIONS

Jejunal mucosal perfusion increases during mild hypothermic cardiopulmonary bypass (CPB). Intestinal laser Doppler flowmetry, gastric tonometry, and measurements of splanchnic lactate extraction could not reveal a local or global splanchnic ischemia during or after CPB. A mismatch between splanchnic oxygen delivery and demand was seen, particularly during rewarming and warm CPB.

Plasma endotoxin concentrations during cardiac surgery may be related to atherosclerosis

Systemic endotoxemia develops during cardiopulmonary bypass, probably due to intestinal ischaemia. Differences in endotoxaemia among various cardiac operations and the relationship between endotoxemia and postoperative complications were studied in high-risk patients. Blood samples were obtained at termination of bypass in 136 adults undergoing elective cardiac surgery. Postoperative complications were registered prospectively. Plasma endotoxin was quantified by a kinetic limulus amebocyte lysate assay. Mean endotoxin concentrations were significantly lower in patients undergoing isolated valve replacement (89 ng/l) than in patients undergoing coronary artery bypass grafting alone (234 ng/l), or combined with valve replacement (278 ng/l) or carotid artery surgery (321 ng/l) (p < 0.05). In multivariate linear regression, only the number of grafts (0, 1-3, 4-5) was significantly correlated to endotoxin concentrations (p < 0.0005). Endotoxin concentrations were related to development of gastrointestinal dysfunction (p = 0.03), but not to mortality (p = 0.24) or other complications (p = 0.62).

High thoracic epidural anesthesia, but not clonidine, attenuates the perioperative stress response via sympatholysis and reduces the release of troponin T in patients undergoing coronary artery bypass grafting

In this prospective study, we evaluated whether high thoracic epidural anesthesia (TEA) or i.v. clonidine, in addition to general anesthesia, affects the cardiopulmonary bypass- and surgery-associated stress response and incidence of myocardial ischemia by their sympatholytic properties. Seventy patients scheduled for elective coronary artery bypass graft (CABG) received general anesthesia with sufentanil and propofol. TEA was randomly induced before general anesthesia and continued during the study period in 25 (anesthetized dermatomes C6-T10). Another 24 patients received i.v. clonidine as a bolus of 4 microg/kg before the induction of general anesthesia. Clonidine was then infused at a rate of 1 microg x kg(-1) x h(-1) during surgery and at 0.2-0.5 microg x kg(-1) x h(-1) postoperatively. The remaining 21 patients underwent general anesthesia as performed routinely (control). Hemodynamics, plasma epinephrine and norepinephrine, cortisol, the myocardial-specific contractile protein troponin T, and other cardiac enzymes were measured pre- and postoperatively. During the preoperative night and a follow-up of 48 h after surgery, five-lead electrocardiogram monitoring was used for ischemia detection. Both TEA and clonidine reduced the postoperative heart rate compared with the control group without jeopardizing cardiac output or perfusion pressure. Plasma epinephrine increased perioperatively in all groups but was significantly lower in the TEA group. Neither TEA nor clonidine affected the increase in plasma cortisol. The release of troponin T was attenuated by TEA. New ST elevations > or = 0.2 mV or new ST depression > or = 0.1 mV occurred in > 70% of the control patients but only in 40% of the clonidine group and in 50% of the TEA group. We conclude that TEA (but not i.v. clonidine) combined with general anesthesia for CABG demonstrates a beneficial effect on the perioperative stress response and postoperative myocardial ischemia.

IMPLICATIONS

Thoracic epidural anesthesia combined with general anesthesia attenuates the myocardial sympathetic response to cardiopulmonary bypass and cardiac surgery. This is associated with decreased myocardial ischemia as determined by less release of troponin T. These findings may have an impact on the anesthetic management for coronary artery bypass grafting.