Fever and infection after cardiac operation

Clinical Predictors of Positive Postoperative Blood Cultures

OBJECTIVE

To define clinical features of surgical patients in whom postoperative blood cultures are likely to identify pathogens.

BACKGROUND

Bacteremia is a worrisome postoperative complication and blood cultures (BCx) are routinely used for evaluation of postoperative bacteremia, but are costly and not always diagnostic. Better methods are needed to select patients in whom BCx identify pathogens.

METHODS

We reviewed records of patients ≥18 years old with BCx drawn ≤10 days after surgery in 2013 seeking independent predictors of positive cultures by simple and multiple logistic regression models with statistical significance at α = 0.05.

RESULTS

Of 1804 BCx, excluding contaminants yielded 1780 cultures among 746 patients for analysis. The yield was low, with only 4% identifying potential pathogens. Positive BCx were most common after cardiac, ear/nose/throat, obstetric, and urologic procedures [odds ratio (OR) =10.3, P < 0.001 vs low-yield procedures: eg, gynecologic, neurosurgical, plastic surgical, podiatric, transplant]. Cultures more often grew pathogens when drawn in association with higher peak temperature (Tmax, P = 0.001) and longer interval from procedure to Tmax (P = 0.001). Antibiotic therapy at time of culture reduced yield (2.9% with vs 5.5% without antibiotics, P = 0.007). Multivariable logistic regression analysis found antibiotics at culture, procedure specialty, Tmax, and postoperative timing of Tmax were associated with blood culture results.

CONCLUSIONS

Ordering blood cultures based on fever or another single predictor inconsistently identifies pathogens. Our dataset, the largest available, identify clinical predictors in the first 10 postoperative days to guide identification of patients with bacteremia.

Evaluation of fever and infections in cardiac surgery patients

Fever following cardiac surgery is common and may be infectious or noninfectious in etiology. In this article, we review the major causes of postoperative fever while highlighting special considerations in cardiac surgery patients. We also outline a structured approach to evaluation and present an overview of diagnostic and management considerations for mediastinitis, postpericardiotomy syndrome, prosthetic valve endocarditis, aortic vascular graft infections, and ventricular assist device infections.

Approach to postoperative fever in pediatric cardiac patients

Fever in the postoperative period in children undergoing surgery for congenital heart disease is fairly common and tends to cause anxiety to both the surgeon and the patient. Such fever is associated with the metabolic response to trauma, systemic response to the cardiopulmonary bypass, hypothermia, presence of drainage tubes, drugs, blood transfusion as well as infections. Establishing the diagnosis requires proper assessment of the patient with focused history, targeted physical examination and judicious use of investigations with the knowledge of the common causes.

The Efficacy of Blood Culture in Postoperative Patients

Blood cultures are often obtained in postoperative patients to rule out bloodstream infections. Our study objectives were to determine the efficacy of blood cultures in postoperative patients with suspected sepsis and to determine variables predisposing patients to positive cultures. This was a retrospective study including patients with blood cultures drawn from January to March 2009 at our institution. We recorded demographics, presence of fever (temperature 101.5°F or higher), elevated white blood cell count (12,000/μL or greater), central line, diabetes, intensive care unit admission, postoperative day of blood draw, National Research Council surgical wound classification, and pre- or postoperative antibiotics. Blood cultures were drawn from 150 patients undergoing surgery within 30 days prior. Sixteen had positive cultures and nine were true-positives (6.3%). There was no statistical difference ( P > 0.05) between patients with positive and negative cultures except that those with negative cultures were more likely to have received preoperative antibiotics ( P = 0.0186). Blood cultures are invasive, expensive tests with low yield. We recommend that blood cultures be drawn in patients not receiving preoperative antibiotics who have undergone surgery more than 4 days before culture.

Hepcidin, interleukin-6 and hematological iron markers in males before and after heart surgery

Anemia of inflammation in patients with acute or chronic acute-phase activation is a common clinical problem. Hepcidin is a peptide shown to be the principal regulator of the absorption and systemic distribution of iron. Main inducers of hepcidin are iron overload, hypoxia and inflammation, where the latter has been linked to hepcidin via increased interleukin-6 (IL-6). This article addresses the impact and time course of postoperative acute-phase reaction in humans following heart surgery on prohepcidin, hepcidin, hematological markers and IL-6 concentrations. Serum concentrations of prohepcidin, hepcidin, IL-6 and hematological iron parameters were studied in five male patients without infection before and after heart surgery. This study, which is the first to report the impact on serum hepcidin and serum prohepcidin concentrations in patients following surgery, clearly demonstrates the induction of hypoferremia due to the postoperative acute-phase reaction. Significant changes were seen for serum iron concentration, transferrin saturation, total iron binding capacity and hemoglobin concentration. A significant increase in ferritin concentration was seen 96-144 h postoperatively. Additionally, there were significant alterations in both serum hepcidin after 96-144 h and serum prohepcidin after 48 h compared with preoperative values. Serum prohepcidin decreased, whereas serum hepcidin increased. In conclusion, changes in serum prohepcidin were followed by an increase in serum hepcidin. This speaks in favor of a chain of action where proteolytic trimming of serum prohepcidin results in increased serum hepcidin. However, hypoferremia appeared prior to the changes in serum prohepcidin and serum hepcidin.

Surgical infections in patients with chronic renal failure

Patients with chronic renal failure and uremia have impaired host defenses and wound healing that can lead to an increased risk of infection in addition to a frequent need for surgical procedures with synthetic grafts and catheters. Antibiotic therapy plus timely surgical intervention in removal of infected grafts and catheters is crucial for infection control and patient survival. Other surgical infections, such as wound problems, intraabdominal infections, fungal infections, diabetic foot ulcers, and necrotizing soft tissue infections must be attended to promptly.

Endotoxemia and mediator release during cardiac surgery

Endotoxemia in man is a controversial issue. However, endotoxin is a potent trigger of the inflammatory response. Therefore, endotoxin translocation and mediator release was investigated in patients undergoing cardiac surgery. In 40 patients (13 women and 27 men, ages ranging from 30 to 73 years with a median of 60 years), plasma concentrations of endotoxin, interleukin-6 (IL-6), and C-reactive protein (CRP) were determined during and after cardiovascular bypass. In a subgroup of 10 patients, myeloid-related proteins: MRP8, MRP14, and the soluble heterocomplex (MRP8/MRP14) levels were additionally studied. A significant increase (p < 0.01) of plasma endotoxin concentrations was found during surgery, culminating in a peak (median value of 0.82 EU/mL) during reperfusion. Plasma levels of endotoxin continued to be slightly raised until the 5th postoperative day, whereas those of interleukin-6 rose at the end of the operation and were at their highest level 6 hours postoperatively (median value of 218 pg/mL). CRP levels were increased 24 hours postoperatively with a median value of 114 mg/L and peaked on day 2 (191 mg/L). A statistically significant correlation between the intraoperative endotoxin plasma concentrations and IL-6 concentrations was established (p < 0.05). The MRP8/MRP14 heterocomplex increased until day 2 after surgery, except MRP14, which showed the highest level at day 1 (55 ng/mL). Cardiac surgery is associated with endotoxemia and a marked acute-phase response. Therefore, endotoxin must be regarded as a pathophysiologic mediator. The role of the gut as a source of endotoxemia following cardiac surgery deserves further attention.

Contemporary issues with bacterial infection in the intensive care unit

Nosocomial infection in the critically ill results from defects in the intrinsic barriers to microbial invasion. The diagnosis is complicated by an inability to perform an adequate physical examination in a patient with several compounding findings, usually necessitating sophisticated technologies to aid in the diagnosis. Pneumonia, line sepsis, urosepsis, sinusitis, endocarditis, peritonitis, and acalculous cholecystitis are the more common infections that challenge the care of the critically ill. Antibiotic therapy is adjunctive to efforts to preserve the barrier, but should be started early, should be targeted as specifically as possible to the offending organisms, and should be dosed adequately to ensure an effective concentration in the infected tissue.

Early bloodstream infection after cardiopulmonary bypass: frequency rate, risk factors, and implications

OBJECTIVE

To determine the incidence, predisposing factors, and outcome of early bloodstream infection after cardiopulmonary bypass.

DESIGN

A case control study.

SETTING

A 54-bed cardiac surgical intensive care in a tertiary referral center.

PATIENTS

Patients from a 30-month period with preoperative hospital stay of <48 hrs and subsequent bloodstream infection within 96 hrs of cardiopulmonary bypass were included in a case group. The control group consisted of patients who had cardiac surgery on the same day as the case group.

MEASUREMENTS AND MAIN RESULTS

Patient demographics, history of comorbidity, preoperative laboratory testing, details of surgery, transfusion requirement, inotropic infusions, hemodynamics, and arterial blood gases on admission to intensive care were compared in the two groups. Measures of outcome were duration of mechanical ventilation and intensive care stay, serum creatinine on the first postoperative day, highest creatinine and bilirubin concentrations, and hospital mortality. During the study period, 7,928 patients had cardiac surgery. Sixteen (0.2%) patients had early bloodstream infection; the control group consisted of 95 patients. Thirteen of the patients with bloodstream infection had Gram-negative bacilli on blood culture, two had Candida species, and two had Gram-positive bacteria. On multivariate logistic regression analysis, greater prevalence of preoperative pulmonary hypertension (odds ratio 9; 95% confidence interval 2 to 41.8; p = .004), diabetes (odds ratio 4.6; 95% confidence interval 1.4 to 15.8; p = .01), number of blood products transfused (odds ratio 1.09; 95% confidence interval 1.04 to 1.17; p = .005), and infusion of inotropes (odds ratio 4.7; 95% confidence interval 1.3 to 16.4; p = .02) or vasopressors (odds ratio 4.1; 95% confidence interval 1.3 to 15.6; p = .02) were associated with postoperative bloodstream infection. Early bloodstream infection was associated with significantly prolonged duration of mechanical ventilation (117.2 +/- 21.5 vs. 18 +/- 8.8 hrs; p = .0001), intensive care stay (213 +/- 27.5 vs. 53 +/- 11.3 hrs; p < .0001), greater creatinine concentrations on the first postoperative day (1.6 +/- 0.1 vs. 1.2 +/- 0.04 mg/dL; p = .0002), greater maximum creatinine concentration (2.4 +/- 0.2 vs. 1.3 +/- 0.1 mg/dL; p < .0001), and greater maximum bilirubin concentration (4.7 +/- 0.6 vs. 1.3 +/- 0.2 mg/dL; p < .0001) when compared with the control group. Five (32%) of 16 bacteremic patients died vs. none of the 95 control patients (p < .0001).

CONCLUSIONS

Early bloodstream infection after cardiac surgery is uncommon and involves predominantly Gram-negative bacteria. The risk factors associated with bloodstream infection were preoperative morbidity and more complex surgery. Bloodstream infection was associated with a significantly adverse impact on outcome after cardiac surgery.

Frequency, manifestations, and correlates of impaired healing of saphenous vein harvest incisions

OBJECTIVE

To describe the frequency, manifestations, and correlates of impaired healing of saphenous vein (SV) harvest incisions in hospitalized patients who had undergone coronary artery bypass grafting (CABG).

DESIGN

Prospective, descriptive, correlational.

SETTING

West Coast university-affiliated medical center.

PATIENTS

Thirty-two English-speaking adults who had undergone CABG.

OUTCOME MEASURES

Impaired wound healing of SV-harvest incisions.

RESULTS

The overall incidence of impaired healing was 43.8%. The most frequent manifestations of impaired wound healing at discharge were prolonged erythema (8/32), prolonged drainage (8/32), and both prolonged erythema and drainage (2/32). Correlates of impaired healing of SV-harvest incisions were body mass index (product-moment correlation = 0.39, p = 0.026) and preoperative use of diuretics (point biserial correlation = 0.42, p = 0.016).

CONCLUSIONS

Impaired healing of SV-harvest incisions in this sample occurred more frequently than previously indicated in the literature. Although severe wound infections were infrequent, a high degree of impaired healing occurred (43.8% of patients who had undergone CABG). Future studies need to explore the long-term effects of impaired healing and test interventions to mitigate impaired healing in this population.

Efficacy of breathing and coughing exercises in the prevention of pulmonary complications after coronary artery surgery

One hundred twenty patients undergoing coronary artery surgery completed a randomized controlled study designed to investigate whether prophylactic chest physiotherapy affected the incidence of postoperative pulmonary complications. Group 1 patients received no preoperative or postoperative chest physiotherapy. Group 2 patients received preoperative education and instruction in breathing and coughing exercises and postoperative supervision and assistance in performing the same. These exercises were supervised by a physiotherapist twice per day on the first 2 postoperative days and once per day on the 3rd and 4th postoperative days. Physiotherapy for group 3 patients was the same as for group 2 patients except that patients were seen by a physiotherapist 4 times per day on the first 2 postoperative days and twice per day on the 3rd and 4th postoperative days. Group 2 and 3 patients were instructed to practice breathing and coughing exercises every hour. Overall, an incidence of clinically significant postoperative pulmonary complications of 7.5 percent was demonstrated. In general, these patients demonstrated lower levels of preoperative pulmonary function and very low early postoperative oxygenation compared with those who did not develop pulmonary complications. There was no indication that the incidence or severity of fever, hypoxemia, chest roentgenologic abnormalities or clinically significant postoperative pulmonary complications was different between groups. These results suggest that the necessity for prophylactic chest physiotherapy after routine coronary artery surgery should be reviewed.

Paranasal sinusitis: cryptic sepsis after coronary artery bypass operations

Infections occurred in 52 of 400 patients (13%) undergoing coronary artery bypass operations from January 1987 to December 1990. The hospital courses of 5 patients (1.3%) in whom occult infections of the paranasal sinuses developed were reviewed. Only 1 patient had specific clinical findings of acute sinusitis (purulent nasal discharge). Computed tomography showed wall thickening, opacification, or air-fluid levels in one or more paranasal sinuses in each patient. All patients were successfully treated with surgical drainage and antibiotics. Risk factors for development of postoperative acute sinusitis include: prolonged tracheal intubation, airway colonization with nosocomial bacteria, inability to clear nasal secretions, sinus ostial obstruction, and critical organ system dysfunction. Physical examination and roentgenographic evaluation of the paranasal sinuses should be considered when postoperative sepsis of obscure etiology occurs.

Caring for patients after coronary bypass surgery. Follow-up tips for primary care physicians

Primary care physicians are often faced with follow-up care of patients who have had coronary artery bypass graft surgery. Familiarity with possible cardiac, pulmonary, neurologic, and infectious complications is important, and an open line of communication with the consulting cardiologist and the cardiac surgeon is essential. Modification of coronary risk factors is one of the greatest challenges after bypass surgery. The primary care physician plays the major role in directing and monitoring life-style changes that reduce the risk of progressive coronary atherosclerosis. Recurrent myocardial ischemia after bypass surgery should be evaluated fully and is often responsive to nonsurgical therapies, including percutaneous transluminal coronary angioplasty.

Predictors for infection following open-heart surgery

A large open-heart surgery unit dealing with approximately 1000 elective patients per annum and housed in a dedicated suite, including a specialized intensive therapy unit, has provided a unique model for the study of predictors of infections and related phenomena. Over more than 10 years a series of studies has shown: the powerful effect of antibiotic usage on the colonization/infection rates with Gram-negative bacilli; the predictive relationships between preoperative chest status and the development of postoperative chest problems; an important correlation between preoperative peak urine flow rates and susceptibility to postoperative urinary tract infections; and the predictive significance of preoperative antibodies to enteric Gram-negative bacilli in relation to postoperative pyrexia and Gram-negative infection. The lessons learned from this easily studied group of patients may have important applications in other surgical settings.

A comparative study of cefamandole and ceftriaxone as prophylaxis in cardiac surgery

We compared the prophylactic use of cefamandole and ceftriaxone in 40 patients undergoing elective cardiac surgery. Postoperative wound infection occurred in one and two patients, respectively, in each group (n.s.), and bronchial superinfection in one patient in each group. In 12 additional patients drug concentrations in plasma and pericardial fluid were measured at different times following the administration of ceftriaxone. Plasma and pericardial fluid concentrations of ceftriaxone were above the minimal inhibitory concentration of susceptible microorganisms for up to 24 h after intravenous administration. We conclude, firstly, that the incidence of infection after cardiac surgery is low with both cefamandole and ceftriaxone prophylaxis. Secondly, efficient plasma and pericardial fluid levels of ceftriaxone last for up to 24 h after intravenous administration.

Postoperative temperature and infection in patients undergoing general surgery

During a study concerned with postoperative hypothermia, Closs (1985) noted an association between patients' core temperatures in the immediate postoperative period and respiratory infection. In this paper, a small follow-up study is reported in which the relationship between postoperative temperature and the development of infection (respiratory, wound or urinary tract) was investigated in 41 patients who underwent general surgery. Aural and oral core temperatures were monitored at 270, 300 and 330 minutes following return to the ward postoperatively. In the week following surgery, patients were monitored daily for any sign or symptom of infection. Reference was made to the patient, nursing notes, medical notes and physiotherapist (when available). Seven of the 16 patients (44%) exhibiting an aural core temperature of greater than or equal to 37.8 degrees C between 270 and 330 minutes post-return to ward developed infection while five of the 25 patients (20%) exhibiting an aural core temperature of less than 37.8 degrees C developed infection. Oral temperature measurements (using ward mercury-in-glass thermometers) showed a very similar pattern. Overall, infection was detected in 12 of the 41 patients (29%) in the 6 days following surgery, 11 having a respiratory infection and one a wound infection.

Drug-induced fever

Humans maintain body temperature within a narrow range. Drug administration can upset the usual balance and cause a fever. The drug may interfere with heat dissipation peripherally, increase the rate of metabolism, evoke a cellular or humoral immune response, mimic endogenous pyrogen, or damage tissues. The fever may be a result of the pharmacological action of the drug or some other unrelated effect. Drug-induced fever is most commonly the result of a hypersensitivity reaction and its characteristics resemble those of an allergic reaction. The fever most commonly occurs after 7 to 10 days of drug administration, persists as long as the drug is continued, disappears soon after stopping the drug, and will rapidly reappear if the drug is restarted. The agents most commonly associated with causing fever include the penicillins, cephalosporins, antituberculars, quinidine, procainamide, methyldopa, and phenytoin.

Families in which two or more cot deaths have occurred

A survey of twelve families with 2 or more cot deaths showed that in two families the deaths were completely unexplained; in three the babies had a probably familial developmental disorder; in two the care of the infants was seriously at fault and could have contributed to death; and in five filicide was probable. 3 of the mothers in the last group were psychologically ill. Detailed pathological and psychosocial investigations are needed in dealing with these deaths and in planning the care of future children.