Nosocomial infections after cardiac surgery in infants and children: incidence and risk factors

This prospective study was undertaken to determine the spectrum, sites and main risk factors for hospital-acquired infections (HAI) in our paediatric cardiothoracic intensive care unit (PCICU), and to determine the main organisms causing bloodstream infection in this setting. All patients admitted between January and December 1999 were prospectively followed for the development of HAI. To define risk factors, patients were grouped by age, complexity score, length of stay in PCICU, and whether the patient's chest was open or closed postoperatively. Three hundred and thirty-five patients underwent cardiac surgery. Fifty-five patients acquired 69 HAIs (HAI patient rate 16.4%). The most common HAI were bloodstream and surgical wound infection in 10 and 8%, respectively. The main causative organisms were Klebsiella spp.,Enterobacter spp. and Pseudomonas spp. in 22, 17 and 16% of episodes, respectively. Staphylococcus spp. accounted for 16% of episodes. The main risk factors for developing HAI were: neonatal age [P < 0.05, odds ratio (OR): 5.89, 95% confidence interval (CI): 2.96-11.58] prolonged PCICU stay (P < 0.05, OR: 6.82, 95% CI: 3.37-14.48), open chest postoperatively (P < 0.05, OR: 3.44, 95% CI: 1.31-8.52) and high complexity score (P < 0.05, OR: 4.03 95% CI: 1.87-8.43). The main causative organisms of bloodstream infections in children hospitalized in the PCICU differ from those in adult and pediatric general intensive care units (ICUs) and include mainly Gram-negative bacilli. High complexity score, neonatal age, prolonged ICU stay, and open chest postoperatively are risk factors of HAI in this patient population.

How intramembrane proteases bury hydrolytic reactions in the membrane

Intramembrane proteolysis is increasingly seen as a regulatory step in a range of diverse processes, including development, organelle shaping, metabolism, pathogenicity and degenerative disease. Initial scepticism over the existence of intramembrane proteases was soon replaced by intense exploration of their catalytic mechanisms, substrate specificities, regulation and structures. Crystal structures of metal-dependent and serine intramembrane proteases have revealed active sites embedded in the plane of the membrane but accessible by water, a requirement for hydrolytic reactions. Efforts to understand how these membrane-bound proteases carry out their reactions have started to yield results.

Pectoralis major muscle flap for deep sternal wound infection in neonates

BACKGROUND

Deep sternotomy wound infections during the neonatal period, their management utilizing the pectoralis major muscle flap (PMF), and their follow-up are reported.

METHODS

Seven hundred-twenty consecutive pediatric cardiac operations performed from 1995 to mid 1998 in 108 neonates and 612 infants are reviewed. Nine children (1.25%), 6 neonates and 3 infants, developed deep sternotomy wound infections and underwent PMF reconstruction. The 6 neonates are reviewed. Their follow-up includes growth and development reports, physical examination, and computerized tomographic scans of the chest.

RESULTS

The incidence of sternal wound complications in our neonatal patients (5.5%, 6 of 108) was significantly higher than in the infantile group (0.5%, 3 of 612), (p = 0.0001, odds ratio = 11.94). Five neonates were treated with a unilateral, turnover PMF reconstruction. One patient was treated by a bilateral rotational PMF. All sternal wounds healed successfully, and all patients survived. In a follow-up period, ranging from 6 to 31 months (mean 16.5 months), the growth and development of all operated neonates was as expected for their age. There were no signs of chronic sternal infection in any of them.

CONCLUSIONS

Early recognition of sternal wound complications should facilitate surgical treatment. Utilizing the PMF promotes rapid wound healing and preservation of life in these severely ill neonates, with minimal developmental problems.

Extra-anatomic aortic bypass via sternotomy for complex aortic arch stenosis in children

OBJECTIVE

Recurrent aortic narrowing after repair of aortic coarctation or interrupted aortic arch, as well as diffuse, long-segment aortic hypoplasia, can be difficult to manage. Extra-anatomic ascending aorta-descending aorta bypass grafting through a sternotomy is an alternative approach for this problem.

METHODS

Since 1985, 19 patients aged 2 months to 18 years (mean 10.7 years) underwent extra-anatomic bypass with 10- to 30-mm Dacron grafts. The initial diagnosis was coarctation with hypoplastic arch in 15, interrupted aortic arch in 3, and diffuse long-segment aortic hypoplasia in 1. Seventeen of the children had a total of 22 previous operations: transthoracic interposition or bypass graft (n = 7), end-to-end anastomosis (n = 7), subclavian arterioplasty (n = 6), and synthetic patch (n = 2). The mean time from initial repair was 8.0 years (range 0.6-18 years). Three children had previous sternotomies. Cardiopulmonary bypass was avoided in all but 6 patients (5 with simultaneous intracardiac repairs).

RESULTS

No hospital or late deaths occurred. On follow-up from 4 months to 14.7 years (mean 7.9 years), no reoperations for recurrent stenosis were performed. Two patients have arm-to-leg pressure gradients: 20 mm Hg at rest in 1 patient and a 60-mm Hg systolic exercise gradient with no resting gradient in the other. One patient required exclusion of an aortic aneurysm at the old coarctation repair site 13 years after extra-anatomic bypass. Three children had subsequent successful cardiac operations.

CONCLUSIONS

Extra-anatomic bypass is an effective and relatively easy approach for selected cases of complex or reoperative aortic arch obstruction. It should be considered as an alternative operative technique for complex aortic arch reconstruction.

Cleavage of a multispanning membrane protein by an intramembrane serine protease

All intramembrane proteases are known to cleave membrane proteins with a single transmembrane helix. Such cleavages often release anchored soluble domains, which play a role in physiologically important inter- and intracellular processes. However, in many cases the physiological roles/substrates of intramembrane proteases are not known. It is interesting that no multispanning substrates were identified so far, despite the fact that intramembrane proteases have promiscuous substrate recognition and cleavage capabilities. Here we determined whether, in a synthetic experimental system, intramembrane proteases have the capability to interact with and cleave multispanning membrane proteins. We utilized the Escherichia coli rhomboid GlpG, an intramembrane serine protease, and truncated versions of the E. coli multidrug transporter MdfA as model multispanning membrane proteins. On the basis of in vivo and in vitro studies on the association of GlpG with various MdfA constructs and their cleavage, we conclude that GlpG is able to recognize and cleave truncated forms of MdfA but not the intact protein. We propose that GlpG has the capacity to act on unfolded multispanning membrane proteins, thus providing an incentive for investigating possible physiological consequences.

Successful biventricular repair after initial Norwood operation for interrupted aortic arch with severe left ventricular outflow tract obstruction

BACKGROUND

Management of newborns with interrupted aortic arch (IAA) remains challenging. Associated severe left ventricular outflow tract obstruction (LVOTO) have often led to increased mortality with neonatal biventricular repair. We review our experience with an alternative approach for this complex surgical problem.

METHODS

From May 1991 to June 1999, 28 neonates were treated for IAA. Thirteen of 28 neonates (46%) had type B IAA, ventricular septal defect (VSD) and severe LVOTO (Z value -2 to -7; mean -5 +/- 1.7). Mean age was 8 days (3 to 23 days old) with average weight of 3.3 kg (2.4 to 4.2 kg). Eight of 13 (62%) had anomalous right subclavian artery. Ten of 13 (77%) had thymic aplasia and chromosome 22 region qll deletion. All 13 patients were treated initially with a modified Norwood procedure.

RESULTS

There were no perioperative deaths. Complications included 2 patients with recurrent arch stenosis treated with balloon dilatation. Two patients had systemic arterial shunt revision. Follow-up ranged from 2 to 99 months old (mean 39 months). There were 2 late deaths unrelated to any operation. Nine of 12 patients had a second stage palliation consisting of a bidirectional Glenn shunt. Six patients went on to have biventricular repairs (3 Ross-Konno, 2 Rastelli, 1 VSD closure with LVOT resection). One patient had a modified Fontan operation and 5 patients are awaiting potential biventricular repair.

CONCLUSIONS

Children with IAA and severe LVOTO may be managed by initial Norwood palliation with an excellent outcome likely. This initial "univentricular" approach has enabled eventual successful biventricular repair despite severe LVOTO.

Physostigmine antagonizes morphine-induced respiratory depression but not analgesia in dogs and rabbits

The ability of physostigmine to antagonize the respiratory depressant effect of morphine was studied in conscious rabbits and ketamine-anaesthetized dogs pretreated with atropine methyl nitrate. Morphine 4 mg kg-1 increased PaCO2 in the rabbit from 3.43 +/- 0.16 to 4.95 +/- 0.28 kPa, decreased arterial pH from 7.45 +/- 0.01 to 7.31 +/- 0.01 and decreased respiratory frequency by 36%. Physostigmine 0.1 mg kg-1 reduced PaCO2 to control values within 10 min and significantly increased arterial pH and respiratory frequency. There was no antagonism of the analgesic effect of morphine. Neostigmine 0.1 mg kg-1 did not reverse the respiratory depressant effect of morphine. In dogs anaesthetized with ketamine, morphine 15 mg kg-1 caused loss of consciousness and marked analgesia, decreased the respiratory frequency by 47%, and increased PaCO2 by 47%. Physostigmine 0.1 mg kg-1 antagonized the effect of morphine on respiration and restored consciousness in the dogs, but did not impair analgesia. It is concluded that physostigmine reverses morphine-induced respiratory depression by prolonging the effect of acetylcholine released from brain-stem neurones. The possibility should be considered of replacing opiate antagonists by physostigmine to reverse postoperative respiratory depression and drowsiness induced by opiates.

Chest reconstruction in asphyxiating thoracic dystrophy

Asphyxiating thoracic dystrophy is a rare, complex malformation with a broad spectrum of clinical expression. Surgery is indicated only in severe cases in which failure to intervene will result in progressive pulmonary damage and eventual death. Conventional surgical techniques for expanding the thoracic cage diameter by sternotomy and the insertion of a metal prosthesis for anterior chest wall stability usually provide these patients with the time needed for thoracic cage growth. However, some of the most severe cases may require a two-stage approach. Hence, management should be directed toward resolving immediate ventilatory problems and minimizing secondary damage to the lungs caused by prolonged ventilatory support.

Genetic evidence for functional interaction of the Escherichia coli signal recognition particle receptor with acidic lipids in vivo

The mechanism underlying the interaction of the Escherichia coli signal recognition particle receptor FtsY with the cytoplasmic membrane has been studied in detail. Recently, we proposed that FtsY requires functional interaction with inner membrane lipids at a late stage of the signal recognition particle pathway. In addition, an essential lipid-binding α-helix was identified in FtsY of various origins. Theoretical considerations and in vitro studies have suggested that it interacts with acidic lipids, but this notion is not yet fully supported by in vivo experimental evidence. Here, we present an unbiased genetic clue, obtained by serendipity, supporting the involvement of acidic lipids. Utilizing a dominant negative mutant of FtsY (termed NG), which is defective in its functional interaction with lipids, we screened for E. coli genes that suppress the negative dominant phenotype. In addition to several unrelated phenotype-suppressor genes, we identified pgsA, which encodes the enzyme phosphatidylglycerophosphate synthase (PgsA). PgsA is an integral membrane protein that catalyzes the committed step to acidic phospholipid synthesis, and we show that its overexpression increases the contents of cardiolipin and phosphatidylglycerol. Remarkably, expression of PgsA also stabilizes NG and restores its biological function. Collectively, our results strongly support the notion that FtsY functionally interacts with acidic lipids.

Thromboxane production in human lung during cardiopulmonary bypass: beneficial effect of aspirin?

BACKGROUND

Increased systemic levels of thromboxane (Tx) during cardiopulmonary bypass (CPB) in humans have been reported. It is not known whether this reflects a general systemic response to the surgical procedure or an increased pulmonary production of Tx in response to ischemia and reperfusion.

METHODS

Thromboxane B2 levels were measured in the right atrium and left atrium of 14 patients undergoing coronary artery bypass grafting for angina. Eight patients (group 1) were without aspirin for at least 15 days before operation, and 6 patients (group 2) were treated with aspirin (100 mg/day) for at least 1 month before operation. Levels of TxB2 were determined by enzyme immunoassay after lipid extraction and separation.

RESULTS

Thromboxane B2 levels were elevated throughout CPB. In group 1, left atrial TxB2 levels were significantly higher (p < 0.05) than right atrial levels at all study points during CPB. After pulmonary reperfusion, TxB2 levels in both atria increased significantly (p < 0.02) compared with the levels before cross-clamping of the aorta, and there was an increasing gradient between the two atria (p < 0.05). Mean plasma TxB2 levels during CPB in group 2 were significantly reduced (p < 0.0001) in the right atrium (by 73%) and in the left atrium (by 69%) compared with levels in group 1.

CONCLUSIONS

The rise in TxB2 levels in the left atrium after CPB in humans reflects production of Tx mainly in the lungs, most probably by ischemic pulmonary tissue and intravascular hematologic components. Aspirin markedly reduces Tx production during CPB, and it might play a major role in preventing pulmonary injury after operations with CPB in humans.

Plasma vascular endothelial growth factor level is a predictor of the severity of postoperative capillary leak syndrome in neonates undergoing cardiopulmonary bypass

Capillary leak syndrome (CLS), characterized by extravascular fluid accumulation and significant organ dysfunction, is a serious complication in children undergoing cardiopulmonary bypass (CPB). We examined the relationship between plasma vascular endothelial growth factor (VEGF) levels and severity of CLS. The kinetics of VEGF in the plasma of 11 neonates and 7 older children undergoing CPB were investigated, correlating plasma VEGF levels and CLS clinical presentation. The degree of postoperative CLS was quantified by measuring parameters of extracellular volume and end-organ dysfunction. A chest-wall soft-tissue-width index (CSTWI) was designed in order to standardize the extracellular fluid accumulation. Most CLS parameters were significantly more prominent in the neonatal patients. Low plasma VEFG levels (>35 pg/ml) were found in 3 neonatal control patients and all but, sample from the older group patient. The neonates had significantly higher preoperative VEGF plasma levels (684.4 +/- 559.1 pg/ml, P = 0.02), which decreased during the operation to levels below 35 pg/ml and increased again 24 h postoperatively to levels significantly higher than in the older patients (484 +/- 270.3 pg/ml, P = 0.001). Multilinear regression analysis found preoperative VEGF levels to independently correlate with CLS as represented by CSTWI (P < 0.01, r = 0.726). Both the occurrence of post-CPB CLS and plasma VEGF levels pre- and postoperatively were thus higher in neonates than in children. Plasma VEGF level is a predictor of the severity of postoperative CLS.

The Konno aortoventriculoplasty for repeat aortic valve replacement

OBJECTIVE

To evaluate the outcome of aortic root augmentation by the Konno-aortoventriculoplasty technique as part of reoperative aortic valve replacement.

METHODS

Since 1983, 15 patients, 12 males and three females, had repeat aortic valve replacement (AVR) with concomitant Konno aortoventriculoplasty. Age ranged from 1.2 to 18 years (mean 12.5 years). The underlying anatomic diagnoses were valve and subvalvar aortic stenosis in 11, truncal valve insufficiency in one, endocarditis in one, Shone's complex in one and severe aortic insufficiency associated with a ventricular septal defect in one patient. All patients had had previous AVR. The causes for reoperation were prosthetic valve stenosis due to growth in ten and paravalvular leak in one, homograft failure in two, xenograft failure in one, and left ventricular outflow tract obstruction (LVOTO) after mitral valve replacement in one patient. The mean size of explanted prostheses was 19.2 mm (13-23 mm) while the mean size of the implanted prostheses was 24.3 mm (19-27 mm) (P<0.01). Previous aortic root enlargement had been performed in 11 patients in conjunction with AVR. The Manougian technique was used previously in two, Konno aortoventriculoplasty in eight, and both techniques in one patient. The newly implanted aortic valves were a homograft in one patient and mechanical prostheses in 14 patients.

RESULTS

There was one operative death (1 of 15 or 6.6%) in a 17.5 year old patient with previous AVR and posterior root enlargement, due to low cardiac output state. Follow-up ranged from 6 months to 17 years (mean 7.2 years). The only late death occurred in an 11.6-year-old patient due to prosthetic valve endocarditis. Two patients had complete heart block and had permanent pacemaker insertion (2 of 15 or 13.3%). One patient had pulmonary valve replacement because of combined stenosis and insufficiency 5 years after operation. All 13-surviving patients are asymptomatic at latest follow up.

CONCLUSION

Konno aortoventriculoplasty with repeat AVR may be safely performed. Excellent results may be achieved despite previous aortic root enlargement. It is a good surgical option for complex LVOTO and may even reduce reoperation in children by allowing placement of a larger prosthesis.

Superior vena cava syndrome following neonatal cardiac surgery

OBJECTIVE: To review the incidence, diagnosis, and management of superior vena cava syndrome (SVCS) after surgery for congenital heart disease. DESIGN: Retrospective clinical review. All patients were computer registered. Our database includes daily follow-up. SETTING: Pediatric cardiac surgery intensive care unit in a university hospital. PATIENTS: A total of 1853 consecutive pediatric cardiac operations performed in 285 neonates and 1568 older children from 1993 to 1999 are reviewed. MEASUREMENTS AND MAIN RESULTS: The diagnosis of SVCS was suspected clinically: Color changes and swelling of the upper part of the body, confirmed by echo-Doppler, showed no or minimal flow in the superior vena cava at the beginning and collateral flow later on. Nine patients developed SVCS (0.5%). All the study patients were neonates. The prevalence of SVCS in our neonatal patients was 3.15% (nine of 285), with no SVCS in older children. Accompanying complications included chylothorax (five), hydrocephalous (four)-three of whom required ventriculoperitoneal shunt during follow-up. Thrombolytic therapy was used in five patients, and thrombectomy was used in one patient. The ventilation period ranged from 4 to 46 days (mean 20.1 days), and the length of hospital stay ranged from 37 to 120 days (mean 61.3 days). No mortality was observed during follow-up. CONCLUSIONS: SVCS is an uncommon, severe complication following neonatal cardiac surgery. It may cause chylothorax, hydrocephalus, and severe respiratory complications leading to high morbidity. Early diagnosis and thrombolytic therapy may prevent the progression of this syndrome to its subsequent sequels.

Balance retraining in a hemiparetic patient using center of gravity biofeedback: a single-case study

A single-subject experimental design was used to evaluate the effects of center of gravity biofeedback on retraining balance control in a 72-yr.-old male hemiparetic patient. For both assessment and training the subject stood on dual force-plates enclosed on three sides by a visual surround. A 4-wk. training period consisted of subject-initiated shifts in body weight to control movement of a real-time computer display of the subject's center of gravity. A Sensory Organization Test and evaluation of weight distribution indicated that biofeedback retraining positively affected balance control during dynamic conditions and when the ground support moved forward.

Is the heart a source for elevated circulating endothelin levels during aorta-coronary artery bypass grafting surgery in human beings?

Reports have shown increased systemic levels of endothelins during coronary artery bypass grafting in human beings. It was not known whether increased endothelin levels during coronary artery bypass grafting reflect a general systemic response to the surgical procedure or increased myocardial production of endothelins in response to ischemia and reperfusion. We therefore measured endothelin levels in the right atrium and proximal aorta of 15 patients undergoing coronary artery bypass grafting for anginal syndrome immediately before aortic crossclamping and again after cessation of cardiopulmonary bypass. In five patients, we also measured coronary sinus levels of endothelins during cardiopulmonary bypass circulation. We found that endothelin levels were elevated throughout the surgical procedure. Right atrial endothelin levels were significantly elevated after cessation of cardiopulmonary bypass circulation with respect to values immediately before aortic crossclamping (11.1 +/- 3.1 vs 14.2 +/- 3.7 pg/ml, p = 0.008), whereas endothelin levels in the proximal aorta did not rise significantly (10.5 +/- 2.3 vs 11.6 +/- 2.4 pg/ml, p > 0.5). Coronary sinus endothelin levels tended to decline temporarily during cardiopulmonary bypass circulation (11.1 +/- 2.1 pg/ml before aortic crossclamping, 7.9 +/- 1.9 1 minute after release of aortic crossclamp, and 9.9 +/- 2.1 pg/ml after release of partial aortic crossclamping, p = 0.06). We conclude that the rise in right atrial endothelin levels during coronary artery bypass grafting reflects systemic production and secretion of endothelins, probably by vasculature or organs distal to the proximal aorta, and is not the result of increased myocardial production and secretion of endothelins.

Coronary artery operation in patients after breast cancer therapy

OBJECTIVE

The purpose of this investigation was to retrospectively study the outcome of patients undergoing coronary artery operation who were previously treated for breast cancer.

METHODS

Between July 1992 and December 1996, 28 patients with a history of breast cancer underwent coronary artery bypass graft operation and were randomly matched against a noncancer group of similar size (n = 36) to allow for comparison of their preoperative characteristics, operative course, and postoperative outcome.

RESULTS

The incidence of sternal wound infection was significantly higher in the cancer group than in the control group (25% versus 6%; p = 0.027). Postoperative noncardiac chest pain occurred more frequently in the cancer group than in the control group (52% versus 31%; not significant). In the study group, radiotherapy and recent myocardial infarction were the only two independent factors associated with sternal wound complications. Patients with a less than 17-year interval between the breast cancer therapy and the coronary artery operation had a higher incidence of sternal wound infection (46%) as opposed to patients with a longer time interval (7%; p = 0.028; odds ratio = 12). Sternal wound complications were more frequent in patients with a history of right-sided breast cancer (50%) compared with left-sided lesions (12.5%; p = 0.068; odds ratio = 7).

CONCLUSIONS

Coronary artery operation in patients after breast cancer therapy may be associated with an increased sternal wound infection rate. To decrease this risk of infection, an approach through a right thoracotomy, minimally invasive techniques, the use of skeletonized internal mammary artery, and broad spectrum antibiotic therapy may be considered.

Septic emboli caused by vascular catheters after surgery for congenital heart disease

OBJECTIVE

To review the incidence, diagnosis, and management of septic emboli caused by vascular catheters after surgery for congenital heart disease.

DESIGN

Retrospective clinical review. All patients were computer registered. Our database includes daily follow-up and every sign of infection registered.

SETTING

Pediatric cardiac surgery intensive care unit in a university hospital.

PATIENTS

A total of 720 consecutive pediatric cardiac operations performed in 108 neonates and 612 older children from 1995 to 1997 are reviewed.

MEASUREMENTS AND MAIN RESULTS

Septic emboli were defined as erythematous non-tender papulonodular hemorrhagic lesions restricted to the limb and distal to the monitoring catheter. Four patients (0.55%) with catheter-related septic emboli after congenital heart surgery were identified, three neonates (0.41%) and one older infant (0.14%). The incidence of catheter-related septic emboli in our patients was significantly higher in the neonatal group compared with older infants (p = .0076; odds ratio=17.45). All infants with catheter-associated septic emboli were severely ill and required prolonged intensive care management postoperatively for periods ranging from 27 to 90 days (mean, 50 days). The catheters involved were in place for periods ranging from 5 to 7 days. All patients were treated by catheter removal and intravenous antibiotics without surgical intervention in the vascular access area. The affected limbs healed well without residual damage.

CONCLUSIONS

Septic emboli are a rare complication of infected vascular catheters in neonates and small infants undergoing prolonged postoperative intensive care management (0.55%). They may indicate the source of unexplained sepsis involving mainly Gram-negative bacilli. Generally, treatment consists of removal of the offending catheter and antibiotic administration with no need for surgical intervention.