Retained common-duct stones after open cholecystectomy and duct exploration in children.

A retrospective study was performed of 250 patients with cholelithiasis treated at the Royal Children's Hospital, (RCH) Melbourne, over 25 years by open operation; 32 (12.8%) had proven choledocholithiasis on either preoperative imaging, operative cholangiography (OpCG), or postoperative investigation. A further 3 had underlying congenital biliary abnormalities and were excluded from further study. Thirty-one of the 32 were explored at open operation, 27 after OpCG and 4 on clinical grounds. One retained common-bile-duct (CBD) stone was undetected until the postoperative period (1/250, 0.25%). Seven ducts were not cleared, giving a duct exploration failure rate of 22.6% (7/31). All 8 retained CBD stones were identified in the early postoperative period and managed with a variety of techniques, including endoscopic retrograde cholangio-pancreatography (ERCP). The incidence of retained stones after open CBD exploration was high (22.6%), and can be attributed to difficulties in operative technique dealing with the smaller paediatric CBD. In addition, haemolytic disease seems to induce a propensity for choledocholithiasis. Given the small numbers presenting with cholelithiasis to RCH (10 per year), it is suggested that a selective approach to CBD exploration is appropriate in children. With the increasing use of laparoscopic cholecystectomy in children and the inherent technical difficulties of laparoscopic operative cholangiography, ERCP may offer an alternative solution in dealing with CBD stones rather than open or laparoscopic CBD exploration.

Left-lung-collapse bronchial deformation in giant omphalocele.

Five infants with giant omphalocele had persistent collapse of the left lung and required prolonged respiratory support. Narrowing of the left main bronchus, reversible with positive end-expiratory pressure, was identified radiographically in 3 infants, and we postulate that this relates to distortion of the bronchus within the constraints of the elongated, narrow thoracic cavity characteristic of these patients. The lung collapse may be precipitated by manipulation (reduction or attempted reduction) of the omphalocele. J Pediatr Surg 36:846-850.

Case report: Colonic duplication: a rare cause of obstruction.

Complete duplication of the entire large bowel with partial ileal involvement is very rare and diagnosis can often be difficult as illustrated by this case report. We also review the other clinical associations of this rare condition and briefly discuss the embryology of duplications of the gastrointestinal tract.

Totally implantable venous access devices in children with cystic fibrosis: incidence and type of complications.

BACKGROUND: Totally implantable vascular access devices (TIVADs) are accepted as a safe and effective method of facilitating long term intravenous therapy. We report our experience of the use of these devices in children with cystic fibrosis with a particular focus on the incidence and type of complications. METHODS: The medical records of patients with cystic fibrosis who underwent placement of a TIVAD at the Royal Children's Hospital, Melbourne, Australia from January 1987 to October 1996 were reviewed. Venous ultrasonography with Doppler was performed in surviving patients with a TIVAD in situ from November 1996 to April 1997 to detect occult thrombotic complications. RESULTS: A total of 57 TIVADs were implanted in 44 children with a median functional duration of 700 days (range 27-3347 days). Twenty one children had devices inserted without complications. Forty eight complications (30 mechanical, 18 infectious) occurred in 36 devices in 23 children during a total functional duration of 53,057 catheter days. Mechanical complications occurred in 53% of devices (one per 1712 catheter days). Symptomatic venous thrombosis occurred five times in four patients (9%). Infectious complications occurred in 32% (one per 2948 catheter days) while sepsis occurred in five devices (9%). Doppler ultrasonography detected unsuspected thrombosis in two of 10 patients examined. CONCLUSIONS: While TIVADs provided effective long term intravenous access, septic and thrombotic complications caused significant morbidity in this population. Careful patient selection, adherence to aseptic technique for access and blood sampling, and periodic ultrasonography with Doppler to detect early thrombosis may help reduce these risks.

Prognosis of congenital diaphragmatic hernia.

Congenital diaphragmatic hernia (CDH) contributes significantly to perinatal morbidity and mortality. This retrospective study examines the experience of a major teaching hospital to establish survival rates and factors influencing outcome. Survival rates were found to relate closely to the stage at which the diagnosis was made and the presence of associated anomalies. Ultrasound diagnosis early in pregnancy is associated with a higher mortality rate than diagnosis made late in pregnancy or after delivery. Logistic regression analysis and chi-squared analysis did not establish to a significant degree that any factor, alone or in combination, was a reliable prognostic indicator. It is acknowledged, however, that figures in this series are small. Survival figures are presented to facilitate reliable parental counselling. In particular, the presence of associated major anomalies and the gestational age at which diagnosis is made are of critical importance in accurately counselling parents regarding the prognosis for survival. In this study, excluding terminations, the mortality rate for isolated CDH diagnosis before the 21st week was 45.5%, with a corresponding survival rate of 54.5%. Once the infant was liveborn, however, the survival rate rose to 68.0%, and if the infant survived transfer to a paediatric surgical unit, the survival rate in this study was 73.9 %.

"In-line" bipolar, steroid-eluting, high impedance, epimyocardial pacing lead.

Recent advances in electrode surface designs have eliminated traditional threshold differences between endo- and epicardial pacing leads. Since the epicardial approach offers the potential of direct left ventricular pacing and the transvenous approach may not be feasible or warranted in all instances, more advanced leads are being designed to optimize epicardial pacing capabilities. This study was conducted to evaluate a bipolar epimyocardial lead. Six immature canines (age 3 months) were instrumented. The lead (Medtronic model 10389) is a single-pass, "in-line" bipolar electrode with low current drain and high impedance, with an intramyocardial steroid-eluting cathode and nonsteroid epicardial anode. Twelve ventricular leads were implanted (two per animal) and the animals followed for 6 months with weekly analysis of pacing and sensing capabilities. Results at explant were compared with implant values and showed no significant differences between sensed R waves or in R wave slew rates in unipolar or bipolar modes. Explant lead impedances remained high in both modes: bipolar, 1658 +/- 331; and unipolar, 1327 +/- 308 omega (P < 0.05). Chronic voltage (V) threshold at 0.5 ms showed no significant change from implant values during the study: unipolar, 0.3 +/- 0.06 versus 1.0 +/- 0.8; and bipolar, 0.4 +/- 0.06 versus 1.6 +/- 1.2. Histologic review showed negligible fibrous reaction at the electrode-tissue interface. This study introduces a high impedance, low threshold, "in-line" bipolar pacing lead design capable of stable chronic pacing with implant facilitated by a single suture technique.

The steroid-eluting electrode: a 10-year experience.

The benefits of steroid-eluting electrodes in reducing stimulation thresholds are well established. A question frequently asked, however, is how long does such an electrode maintain its effect on reducing stimulation threshold? Two studies were designed to answer this question by reporting a long-term prospective human implant review as well as an analytical examination of explanted leads from both humans and animals to determine the amount of remaining steroid in the silicone plug. A previously reported double-blind human study using 20 implanted unipolar ventricular leads, 10 with and 10 without steroid, was followed for 10 years. Pulse width stimulation thresholds were determined at regular intervals using a customized VVIC pulse generator programmed to 1.5-V output. Throughout the study period, the mean stimulation thresholds for the steroid-eluting leads remained almost constant, with a narrow standard deviation, whereas the leads without steroid showed an unpredictable rise and a wide standard deviation. All patients with the steroid-eluting electrodes were paced at 1.5 V, and the four surviving patients still have their original pulse generators. In the second study, the remaining steroid from 25 explanted leads (18 canine and 7 human), were analyzed and graphed against implant times that ranged from 1-350 weeks. Extrapolation of the line of best fit suggests that about 20% of the steroid is still present at 10 years and 18% at 20 years. Only small quantities of steroid are required for its stimulation threshold lowering effect, which continues clinically to at least 10 years. Sufficient quantity of steroid may well be present at 20 years.

Improved epimyocardial pacing: initial experience with a new bipolar, steroid-eluting, high impedance lead design.

Epicardial pacing typically is associated with decreased pacing and sensing capabilities compared with the endocardial approach. Since endocardial pacing is neither appropriate nor possible in all instances, this study was conducted to evaluate a new concept in a chronic epimyocardial lead design in six 3-month-old growing dogs. The new bifurcated lead (Medtronic model 10401) is a low current drain, high impedance, steroid-eluting, bipolar design. The implant is facilitated by a suture attached with an atraumatic needle. Twelve ventricular leads were implanted (2 per animal) and followed for 6 months with weekly analysis of pacing and sensing capabilities. Results at explant were compared with implant values. There were no significant differences between implant and explant in sensed R waves, or in the slew rate of the R wave in unipolar or bipolar modes. Lead impedances at explant remained high in both modes: bipolar, 1550 +/- 223; unipolar, 1234 +/- 262 omega (P < 0.05). Chronic voltage (v) threshold at 0.5 msec showed no significant change from implant values during the study: unipolar, 0.4 +/- 0.2 vs 0.7 +/- 0.3; bipolar, 0.5 +/- 0.4 vs 1 +/- 0.5. Histologic evaluations of the electrode tissue interface demonstrated negligible fibrotic capsule formation. This study introduces a new, easily implanted, high impedance, low threshold, bipolar epimyocardial pacing lead design with excellent chronic pacing and sensing characteristics.

Septal His-Purkinje ventricular pacing in canines: a new endocardial electrode approach.

Ventricular activation sequences and cardiac performance are influenced by pacing sites. Stimulation of or close to the specialized atrioventricular (AV) conduction system optimizes paced ventricular function compared to alternative epi- or endocardial muscle conduction sites. This study reports a new endocardial electrode implant approach to approximate septal His-Purkinje ventricular pacing. Five 6-month-old beagles were used. A custom, platinum-iridium, exposed helical screw electrode (Medtronic, Inc.), 4.5-mm long, with a 17.8-mm2 surface area, was designed with a polyurethane covered 4 filar MP35N nickle conductor lead. An 8 French sheath (USCI, Inc.) was modified as introducer to permit simultaneous implant intracardiac pressure and electrogram recordings. Following a thoracotomy, the introducer was inserted through the right atrial appendage and advanced to record optimal His-bundle electrogram while maintaining atrial pressure along the septal tricuspid valve annulus. After electrode implant, ECG demonstrated narrow paced QRS morphology. Mean implant values showed sensed R wave 6.3 mV, slew rate 0.65 V/sec, pacing impedance 319 ohms, and threshold 0.9 V/3.3 mA at 0.5-msec output. Necropsy showed implant above the tricuspid annulus with electrode extension into and contained within the proximal ventricular septum. This study demonstrates that an endocardial septal approach to His-Purkinje ventricular pacing to optimize paced ventricular function is feasible with a new electrode design and precise septal implant technique. Alternative introducer designs may permit transvenous application of this approach.

The mythology of threshold variations as a function of electrode surface area.

It has been established that the chronic thresholds of cardiac pacing leads vary as a function of the (spherical) electrode's radius or (geometric) surface area and the thickness of fibrotic encapsulation. Where the radius of the electrode is equal to the thickness of the fibrous capsule (about 0.7 to 1 mm for polished surfaces), threshold should be at a minimum. Where the radius of the electrode is larger or smaller than the thickness of the fibrous capsule, then thresholds should increase since the electric field strength required to stimulate decreases as the square of the distance between the electrode's surface and stimulatable tissue. In addition, it has become (incorrectly) accepted that small electrodes do not sense well. About 8-mm electrodes, therefore, became the "standard" surface area, providing the best tradeoffs between pacing and sensing. Analysis of 18 years of canine data in our laboratory, however, suggest that these relationships may be overemphasized for the surface areas of clinical interest. In fact, new small porous and steroid-eluting electrodes do not have high thresholds, are efficient, and their sensing is excellent.

Unusual varieties of diaphragmatic herniae.

Unusual varieties of diaphragmatic herniae can be classified into two major groups, congenital and acquired. The late-presenting Bochdalek herniae often present difficulties in diagnosis which may lead to inappropriate treatment. The prime example is the herniated stomach, which is mistaken for a tension pneumothorax. Strangulation is a rare, but an important, complication of Bochdalek herniae. A number of techniques for closure of large diaphragmatic defects are described with recommendation of those procedures which can be performed rapidly and effectively in a critically ill infant. The literature concerning eventration is confusing due to different definitions of the condition by different authors. It may be difficult to distinguish preoperatively between this condition and congenital diaphragmatic hernia with a sac. Such distinction is often not important as the decision for intervention is based on evaluation of clinical and radiological considerations. The majority of Morgagni herniae are asymptomatic and only rarely does strangulation supervene. There is a small group of infants with Morgagni hernias who present in early infancy with respiratory symptoms. Paralysis of the diaphragm due to phrenic nerve palsy recovers spontaneously in the majority of patients. The selective use of diaphragmatic plication for this condition is widely accepted, but the decision and appropriate timing for surgical intervention is often difficult. The results of surgery are very good both in the early postoperative period and also on long-term follow-up. The diagnosis of traumatic diaphragmatic hernia is often overlooked in the presence of other major injuries. The danger of strangulation of contents of this hernia is ever present and repair should be undertaken without delay once the diagnosis is made.

Growth after gut resection for Crohn's disease.

Seventeen children underwent 19 bowel resections as part of their management of Crohn's disease. Thirteen children had evidence of retardation of linear growth preoperatively, of whom 12 exhibited catch up growth, crossing at least one centile band, after resection. Seven of the 12 showed early signs of puberty at the time of resection and one child was regarded as being fully pubertal. All children were symptomatic before their surgery; at one year 11 were asymptomatic and three others were substantially improved. Surgical resection of localised Crohn's disease, followed by adequate nutritional support has lead to catch up growth and a prolonged symptom free period in most of our patients and this was not limited by their age or stage of puberty.

Preliminary studies on a new steroid eluting epicardial electrode.

Acute and chronic canine atrial and ventricular thresholds and sensing were compared for a steroid eluting epicardial plaque electrode, a similar steroid free plaque electrode and two standard leads. The steroid eluting electrode had low, stable thresbolds in atrium and ventricle compared to the steroid free plaque and standard leads. This new electrode also provided improved atrial sensing. Thus, the concept of a steroid eluting epicardial electrode shows promise for further evaluation.

Polyether polyurethanes: biostable or not?

Certain polyether polyurethanes have been shown to be biostable in long-term implant studies. Others retain good bulk properties, but have been shown to develop cracks on their tissue contacting surfaces. Two cracking mechanisms have been identified, in vivo stress cracking and metal ion oxidation. Stress cracking is the result of an interaction between the in vivo mammalian environment and residual stress (strain) in the implanted polymer. Mild autooxidation can be initiated by stress cracking. More extensive autooxidation can be initiated and propagated by corrosion of metallic device components, especially the corrosion products of cobalt. Both mechanisms are controllable, thus, do not necessarily preclude the use of polyether polyurethanes in implantable devices.

Factors and interactions affecting the performance of polyurethane elastomers in medical devices.

Polyurethanes offer the greatest versatility in compositions and properties of any family of polymers. For implantable medical devices, a few specific elastomeric polyurethane compositions have demonstrated a combination of toughness, durability, biocompatibility and biostability not achieved by any other available material. Because of the complex behavior of implantable polyurethanes in the body environment, designers and fabricators of polyurethane-containing devices must pay particular attention to the choice of composition and design of components. Subsequent treatment during qualification, fabrication, sterilization, storage, implantation, in vivo operation and explantation also determine the performance and provide the means for assessing the efficacy of the polyurethane in the implanted device.

A new low threshold platinized epicardial pacing electrode: comparative evaluation in immature canines.

A prospective comparison of pacing and sensing capabilities between the conventional Medtronic Model 4951 platinum-iridium epicardial pacing electrode and a new modified "platinized" version of the same electrode was performed in immature canines to determine if the new electrode design improves pacing in the immature myocardium. The conventional electrode was modified by electroplating platinum black particles onto the surface to increase the effective or true microscopic surface area, yet essentially maintain the same overall geometric electrode size. Both epicardial electrodes were inserted into the right ventricular myocardium with the lead pad sutured to the epicardium, and externalized to the scruff in five puppies (age 3 months). An additional left ventricular lead was implanted to permit chronic pacing following epicardially-induced atrioventricular block. Acute and chronic sensing and pacing capabilities of each externalized electrode were performed at implant and weekly up to 4 months. Histologic examination of each electrode implant site was performed at the end of the study period. At implant, both electrodes exhibited comparable values for sensed R waves, lead impedances, and pacing thresholds. During the study, the platinized electrode exhibited lower pacing thresholds. Analysis of all postimplant data demonstrated this threshold difference to be significantly lower (P less than .01) for the platinized version. Lead impedance and sensing capabilities remained comparable between the two designs. Histologic study demonstrated less fibrotic infiltration at the platinized electrode site. This preliminary evaluation indicates that for the duration of the postimplant study period, the platinized epicardial electrode design was associated with significantly lower thresholds and less fibrosis as a function of time compared to the conventional smooth electrode surface design. The new platinized electrode limits exit block in the developing immature myocardium and permits safe pacing at lower pulse widths and voltages to increase battery life.

Paired comparisons of steroid-eluting and nonsteroid endocardial pacemaker leads in dogs: electrical performance and morphologic alterations.

The effects of steroid elution from endocardial pacemaker electrodes on electrical performance and the thickness and cellularity of the reactive fibrous connective tissue formed around the stimulating electrode (peri-electrode tissue) were determined. Comparison was made with a nonsteroid electrode implanted in the same cardiac chamber (right ventricle) in each of six dogs for 6 weeks. Paired Students' t-tests showed that steroid-eluting leads had significantly (P less than .05): (1) lower voltage stimulation thresholds (as determined in sequential measurements made on the conscious animals during the experiment and on the anesthetized dogs at termination of the study); (2) less fibrous connective tissue formation around the electrode surfaces; and (3) fewer cells per unit area of peri-electrode fibrous connective tissue. There were also fewer (P less than .10) mast cells in the reactive connective tissue surrounding steroid-eluting leads. The thinner reactive connective tissue surrounding the steroid-eluting electrodes was correlated with lower voltage stimulation thresholds (r = 0.7, P less than .01). This is consistent with the hypothesis that the effect of the peri-electrode connective tissue is to increase the virtual surface area of the electrode, decreasing current density in adjacent stimulatable tissue. The relatively fewer total cells and mast cells in the peri-electrode connective tissue of the steroid-eluting electrodes suggest that the observed differences in fibrous connective tissue thickness, and therefore voltage stimulation threshold, may be related to a relatively decreased population of inflammatory cells due to the anti-inflammatory properties of the steroid.

Infantile myofibromatosis causing biliary and pancreatic obstruction: a case report.

A case of obstructive jaundice caused by a solitary myofibroma in an 18-week-old infant is presented. Preoperative investigations demonstrated total biliary and partial pancreatic obstruction, although no obstructing lesion was identified radiologically. At operation a 3-cm solitary myofibroma was found in the head of the pancreas. Because of the morbidity associated with resection at this site, a bypass procedure was performed in the hope that the lesion will regress.