Morgan P.G. Jamieson

Acute-phase responses to cardiopulmonary bypass in children weighing less than 10 kilograms

BACKGROUND Cardiopulmonary bypass induces a systemic inflammatory response. This study investigated, in a pediatric population, cytokine-induced responses and their potential modification by intraoperative steroid administration. METHODS Markers of the acute-phase response were measured perioperatively in 24 children weighing less than 10 kg undergoing cardiac operations. Those having operations with cardiopulmonary bypass were randomized to receive either no steroid (group I, n = 8) or 10 mg/kg methylprednisolone in the pump prime (group II, n = 10); patients undergoing nonbypass procedures were controls (group III, n = 6). RESULTS In all groups, plasma interleukin-6 level was elevated (p < 0.01) above baseline throughout the post-operative period, peaking earlier in group I. Levels of C-reactive protein peaked at 48 hours, and postoperative core temperature was raised in all groups. Levels of interleukin-6 from 2 to 6 hours and C-reactive protein at 24 hours postoperatively were greater (p < 0.05) in group I than in group II. Maximum interleukin-6 level, C-reactive protein level, and temperature were all significantly greater in group I than in group III. Maximum interleukin-6 level correlated with maximum C-reactive protein level in group I only (rs = 0.76; p < 0.05) and showed no association with temperature. Duration of bypass did not correlate with levels of interleukin-6. CONCLUSIONS This study demonstrated a marked acute-phase response to operation; the greater response to procedures with cardiopulmonary bypass was abrogated by intraoperative steroid administration. The importance of interleukin-6 as an inducer of acute phase proteins after bypass is supported by its association with C-reactive protein levels, but other factors must be important in the induction of pyrexia.

Energy expenditure in children with congenital heart disease, before and after cardiac surgery

Failure to thrive is a common feature of children with congenital heart disease. Whether this is the result of poor nutrition or an abnormally high basal metabolic rate is unknown, yet the state of nutrition has a profound effect on the metabolic response to injury and strongly influences the outcome of surgical treatment. The aim of this study was therefore to measure the preoperative and postoperative energy requirements of children with congenital heart disease. Eighteen children (aged 4 to 33 months) were given two oral doses of doubly labeled water (H2(18)O and 2H2O), the first 1 week before operation and the second 6 hours after the end of cardiac surgery. By measuring the relative loss of each isotope from the body water pool, we were able to calculate the rate of carbon dioxide production and therefore total energy expenditure. In five patients, energy expenditure was clearly elevated, suggesting that a raised basal metabolic rate is an important factor in the observed failure to thrive in at least a proportion of such children. Postoperatively, energy expenditure fell to values below normal for healthy children (not having an operation), which suggests that the stress of surgery leads to smaller energy requirements than have previously been thought.

Transcutaneous iodine absorption in infants undergoing cardiac operation

Povidone-iodine is an effective antiseptic, but its topical use has been associated with a number of adverse reactions in burn patients and in neonates as a result of transcutaneous absorption. In particular, high plasma iodine concentrations are known to cause renal failure, metabolic acidosis, and thyroid suppression. Because of the permeable nature of the skin in small infants and the large areas cleaned before cardiac operations, it is possible that significant transcutaneous iodine absorption might occur in this situation. We have studied 17 infants, less than 3 months of age, who were undergoing closed cardiac or thoracic procedures. After povidone-iodine skin preparation in 15 (covering 20% to 30% of body surface area), plasma total iodine concentrations rose fourfold (range, 160% to 1,440%). This increase was significantly different from the preoperative level at 6, 12, 18, and 24 hours. There was no increase in plasma iodine concentration in 2 patients who were not exposed to povidone-iodine or any other iodine-containing compound. We discuss the implications for a topical antisepsis policy in infants.

Somatosensory Evoked Potentials in the Detection of Spinal Cord Ischemia in Aortic Coarctation Repair

Cortical somatosensory evoked potential (SEP) monitoring was used in 15 patients 2 to 50 years old undergoing repair of aortic coarctation to detect the onset of spinal cord ischemia during the cross-clamp period. Three different response patterns were observed. In 8 patients (53%), the SEP remained unchanged throughout the cross-clamping. This was designated a type 1 response. Six patients (40%) showed a gradual deterioration in the SEP after 15 minutes of cross-clamping (type 2 response). All SEPs returned to normal levels within 5 minutes of release of the clamp. One patient (7%) demonstrated a decline in SEP commencing prior to the application of the cross-clamp when an intercostal vessel was controlled with slings. The SEP completely disappeared within 5 minutes of cross-clamping, but after 19 minutes the repair was completed and the SEP returned within 3 minutes of reperfusion (type 3 response). No patient sustained neurological sequelae of repair. We believe that SEP monitoring offers the potential to identify the patient at risk of developing spinal cord ischemia intraoperatively before irreversible damage occurs. However, it is susceptible to deep halothane anesthesia, which abolishes all cortical responses and requires expert monitoring.

Sinus venosus defect: Single-patch repair with caval enlargement

We present a single pericardial patch repair of the sinus venosus defect with anomalously connected pulmonary veins, incorporating enlargement of the superior vena cava. In our small series to date this procedure has been carried out without morbidity or mortality. Noninvasive follow-up by echocardiography and electrocardiography, over the short term, has not detected any stenosis of the venous pathways or sinus node dysfunction.

The effects of congenital heart disease and cardiac surgery on I iver blood flow in children

Children with congenital heart disease may have some degree of hepatic impairment, with further impairment developing shortly after surgical correction of the cardiac defect. The redistribution of organ blood flow that occurs during cardiopulmonary bypass implicates ischaemia as one of the principal causes of injury. The aim of this study was to measure liver blood flow in children with congenital heart disease and to determine both the effects of cardiopulmonary bypass and the consequences of corrective surgery. Indocyanine green clearance and auricular densitometry, were used in 31 children. In 83% we demonstrated a reduced liver blood flow, with a mean percentage disappearance rate (PDR) of 12.9% (SEM ± 1.2). This finding was unrelated to the patients age, the type of congenital heart defect or the presence or absence of cyanosis. During cardiopulmonary bypass, hepatic perfusion was further reduced in 77% of children, by an average of 67%, out of proportion with the iatrogenic reduction in total body flow. Six hours after surgery, liver blood flow had increased significantly above preoperative levels (p< 0.001; t-test) to approximately normal values with a mean PDR of 20.4% (SEM ± 1.5).

Transoesophageal echocardiographic assessment of primum, secundum and sinus venosus atrial septal defects

We compared the ability of transthoracic and transoesophageal echocardiography to determine the presence and site of an atrial septal defect and associated anomalous pulmonary venous connexions in 13 school age children (aged 5 to 15 years) and 12 adults (aged 25 to 68 years). Transthoracic echocardiography detected atrial septal defects in 12 children and 6 adults. Transoesophageal echocardiography confirmed the position of 16 (13 secundum, 3 primum) of these 18 defects but altered the diagnosis from a secundum defect to a sinus venosus defect in one and from a sinus venosus defect to a high secundum defect in another. In addition to these 18, transoesophageal echocardiography diagnosed a defect in 5 adults (3 secundum and 2 sinus venosus defects) and 1 child (secundum defect). In an adult with inconclusive transthoracic findings, transoesophageal echocardiography enabled clear visualisation of the atrial septum and excluded an atrial septal defect. Transoesophageal echocardiography showed anomalous attachment of a pulmonary vein into the region of a sinus venosus defect (n = 3) but did not show anomalous connexions to the superior caval vein (n = 3) or the inferior caval vein (n = 1). Transoesophageal echocardiography provides a reliable method of diagnosing or excluding an atrial septal defect in patients with inconclusive transthoracic findings and is of particular diagnostic value in sinus venosus defects.

Aortic Origin of Right Pulmonary Artery: Successful Surgical Correction in Three Consecutive Patients

Over a period of four years (1981 through 1984), 3 infants with aortic origin of the right pulmonary artery were seen in our surgical unit. Two infants had a persistent ductus arteriosus, which arose from the left subclavian artery in 1 of them who also had a right-sided aortic arch. There were no other associated abnormalities. Preoperative diagnosis was established by echocardiography in 2 infants. Anatomical surgical correction was undertaken in all 3 infants under cardiopulmonary bypass. There were no operative deaths. One child required reoperation at 15 months for anastomotic stenosis. All 3 children were well two to five years postoperatively with scintillographic evidence of normal ventilation and perfusion. Our experience indicates that this rare but severe congenital cardiac anomaly is easily diagnosed by echocardiography, and confirms that it is eminently amenable to surgical correction.

The validation of auricular densitometry for indocyanine green clearance measurement of hepatic blood flow during and after cardiopulmonary bypass in children

The clinical measurement of hepatic perfusion is complicated by a dual blood supply and the invasive nature of the majority of techniques available. The aim of this study was to validate indocyanine green clearance and noninvasive auricular densitometry as a measure of hepatic perfusion in the context of paediatric cardiac surgery. The effects of different dye concentrations on densitometer recording were assessed in vitro and found to have a linear relationship. Similarly, variations in haematocrit, within the range 21-47%, also had little effect on accuracy. Comparison of densitometry and direct blood sampling with plasma spectrophotometry in six postoperative, normothermic children showed no significant difference between the noninvasive and invasive techniques (r = 0.968; p > 0.05, t-test). Comparison in 10 hypothermic children during cardiopulmonary bypass also showed no significant difference between the two methods, provided that no further cooling or rewarming took place (r = 0.83; p > 0.05, Wilcoxon test). Noninvasive auricular densitometry can, therefore, provide a reliable assessment of hepatic perfusion in children undergoing cardiac surgery.

Effects of dopamine on liver blood flow in children with congenital heart disease

BACKGROUND A reduction in liver function is common after cardiac operations, particularly in children with preexisting cardiac failure. The etiology is multifactorial, but the redistribution of organ blood flow that occurs during cardiopulmonary bypass implicates ischemia as one of the principal causes of injury. Dopamine hydrochloride is known to have specific effects on the renal circulation, and the aim of this study was to investigate its effects on hepatic perfusion. METHODS Eight children with congenital heart disease were studied 6 hours after the end of cardiopulmonary bypass when they were fully rewarmed and hemodynamically stable. Using noninvasive auricular densitometry, we determined the percent disappearance rate of indocyanine green as an index of liver blood flow both before and 1 hour after commencing an infusion of dopamine at 4 micrograms.kg-1.min-1. RESULTS Results showed an increase of approximately 31% in the percent disappearance rate of indocyanine green with the addition of low-dose dopamine (4 micrograms.kg-1.min-1) (p < 0.01). CONCLUSIONS Dopamine may have a therapeutic role in increasing hepatic perfusion and minimizing any loss in liver function.