Severe left ventricular failure after double lung transplantation: pathophysiology and management

Patients undergoing bilateral lung transplantation for end-stage pulmonary hypertension may experience various complications. We describe a patient who underwent transplantation for chronic pigeon breeder's disease, who had secondary pulmonary hypertension and deteriorated right heart function, and who developed severe left heart failure during the weaning phase after successful double lung transplantation. The patient was stabilized with catecholamines and an intra-aortic balloon pump. Left heart function increased within 7 days and normalized at Day 18. Otherwise, the post-operative course was uneventful.

[A "late" scimitar syndrome. Diagnostic contribution of cardiac computed tomography]

A 51-year-old female hospitalized with a non-specific colitis, presented a crescent-like shadow in the right lower lung accompanied by a reduced right lung volume on a routine chest x-ray. There was no family history of congenital heart disease. The initially performed, noninvasive, contrast enhanced cardiac CT (electron-beam tomography [EBT]) proved the suspected diagnosis of a partial, anomalous pulmonary, transdiaphragmatic vein drainage (APVD) in combination with a hypoplastic right lower lobe and dextrocardia. These findings are in accordance with scimitar syndrome. Regarding to the clinical situation with symptoms like slowly progressive dyspnea on exertion and low exercise tolerance for the last 2 years and an invasively documented left-to-right shunt ratio >50% (Qp:Qs = 2.6 : 1) surgical repair was recommended. The anomalous vein was connected to the left atrium creating a "neo-septum". On a postoperative checkup after 9 months the patient is without any medication, symptoms during moderate activity are relieved, exercise tolerance was substantially better and noninvasive imaging visualized the corrected drainage of the anomalous vein to the left atrium.

[Echocardiographic detection of tricuspid valve endocarditis and right atrial and ventricular masses in a patient with acute myeloid leukaemia]

In a patient with acute leukaemia, tricuspid valve vegetations and both right atrial and ventricular masses formed within a few weeks were detected by echocardiography. In addition to endocarditis which is a very rare condition in patients with acute leukaemia, the diagnostic efforts including cardiac surgery resulted in the unusual finding of right-sided cardiac thrombi which had formed autochthonously. The most likely cause was thought to be a very severe systemic infection with staphylococci characterised by repeated episodes of bacteraemia during profound and prolonged neutropenia as well as a paraneoplastic coagulopathy. Surgery performed on the grounds of the echocardiography findings and differential-diagnostic considerations resulted in the relapse-free removal of the infectious focus. The maintenance therapy for leukaemia could thus be continued and led to a distinctly improved outcome. This case report confirms the great importance of sonography in the management of fever of unknown origin in immunocompromised patients.

Intraoperative flow measurement of native coronary artery can help decision making before CABG

We report the case of a patient with three-vessel coronary artery disease whose right coronary artery had been stented at the time of the diagnostic procedure. He had recurrent angina 12 days later and was transferred for urgent coronary artery bypass grafting. No repeat coronary angiography was performed. In the operating room, the flow on the native right coronary artery was determined with an ultrasonic flow probe.

Near-fatal hemoptysis and emergency surgical repair after aortic patch-plasty

A 38-year-old man presented with massive hemoptysis followed by hemorrhage shock. The patient's history revealed a Dacron patch repair for aortic coarctation and recoarctation carried out twice, once 23 and once 10 years ago. Diagnosis of a ruptured descending aortic aneurysm with an aortobronchial fistula into the left lower lobe was established using CT scan. Emergency surgery consisted of left pneumonectomy and descending aortic graft replacement during deep hypothermic circulatory arrest. The patient was discharged 12 days later.

[Surgical treatment of infective endocarditis: the Essen experiences]

BACKGROUND

Instead of immediate diagnosis and effective antibiotic treatment morbidity and mortality in infective endocarditis remains high. If the infection cannot be controlled or the disease progresses irreversible destruction of cardiac structures results.

SURGICAL THERAPY

In this case surgical therapy should be considered immediately. The outcome of surgical repair is not depending on the implanted prosthesis, but solely on timing of the operation.

Hirudin protects from leukocyte/endothelial cell interaction induced by extracorporeal circulation

BACKGROUND

The clinical complications of Extracorporeal Circulation (ECC) have been linked to disturbances in the microcirculation. In order to prevent these deleterious effects, a biodegradeable agent to coat the extracorporeal circuit was tested.

METHODS

Intravital fluorescence microscopy was used on the hamster skinfold chamber model in permanently instrumented, awake animals. ECC was introduced via a micro-roller-pump and a silicon tube shunted between the carotid artery and the jugular vein. The ECC-tube system was coated with PEG-Hirudin-Iloprost, two additional groups received either Iloprost i.v. (0.8 mg/kg/h) or Hirudin i.v. (1 mg/kg b.w.).

RESULTS

ECC for 20 minutes resulted in an increase in rolling and adherent leukocytes in postcapillary venules (Roller 9 to 36 [%]; Sticker 24 to 330 [n/mm2]). Use of the coated tube system reduced L/E cell interaction (Roller 9 to 24* [%], Sticker 28 to 194* [n/mm2]; *p<0.05), whereas Hirudin i.v. nearly abolished it.

CONCLUSIONS

The protective effects of the coating and of Hirudin i.v are probably a result of an attenuated activation of the coagulation-fibrinolytic system.

Disruption of the silver and non-silver coated sewing cuff of a new generation bileaflet valve prosthesis during aortic valve replacement: report on four cases

OBJECTIVES

New generation bileaflet valve prostheses with a silver-coated sewing cuff like the St Jude Medical (SJM((R)) Regent) model are designed to offer a larger valvular orifice as well as a better resistance to postoperative prosthetic endocarditis, at the expense of a smaller sewing cuff.

METHODS AND RESULTS

We report on four cases of aortic valve replacement where during the implantation procedure the fixation cuff disrupted, leading to the exchange of all four valve prostheses. This happened three times with silver- coated sewing cuffs and after withdrawal of the silver- coated cuff prostheses from the market, once with a non silver- coated sewing cuff. This was due to the arbitrary cutting of the cuff fixation suture at the ventricular side of the prosthesis, although the implantation was performed according to the recommendations of the company. This problem didn't occur previously, using other models of the same manufacturer, although the sewing cuff had been fixed in the same technique.

CONCLUSION

Fixation of smaller sewing cuffs of mechanical valve prostheses with a critically exposed fixation suture at the ventricular side of the prosthesis represents a significant risk for disruption during the implantation process through cut off by chance. We recommend meticulous inspection of the sewing cuff for signs of disruption before seating the valve into position. During follow-up particular attention should be paid to valve dislodgement and leakage. The company was informed and advised by us to modify the fixation of the prosthetic annulus of the SJM((R)) Regent valve, which has led to an alternative cuff design, called the SJM Flex cuff.

Sepsis and catecholamine support are the major risk factors for critical illness polyneuropathy after open heart surgery'

BACKGROUND

Critical illness polyneuropathy (CIP) remains a problem after open heart surgery. Recently, we reported about a retrospectively performed study pointing out that sepsis, the application of higher amounts of catecholamines and intervention such as chronic venovenous hemodiafiltration may be involved in the onset of CIP. A prospectively performed study is presented in order to evaluate the significance of risk factors initially after open heart surgery.

METHODS

From June 1997 until September 1998, patients undergoing open heart surgery and being ventilated beyond 3 days were prospectively enrolled in the study and underwent a standard protocol of electromyographic investigation in order to determine CIP. Several items were recorded: amount of catecholamines, serum levels of urea, creatinine, albumin, and glucose. The duration of sepsis and chronic venovenous hemodiafiltration were reevaluated. Additionally the age, the left ventricular end-diastolic pressure prior to the operation, the time of ICU stay and the time of ventilatory support were compared.

RESULTS

Within the observation period, 37 adult patients could be enrolled in the study, whereas 12 patients did develop CIP and 7 patients did not. Patients developing CIP required significantly different amounts of epinephrine (0.17 +/- 0.02 vs. 0.09 +/- 0.01 mg/kg/day, p < 0.05, t-test) higher amounts of norepinephrine (0.06 +/- 0.02 vs. 0.02 +/- 0.01 mg/kg/day, p<0.05, t-test), and lesser dosages of dobutamine (2.2 +/- 0.5 vs. 4.9 +/- 0.7, p<0.05, t-test). After cardiac surgery, the plasma levels of urea was initially significantly elevated in patients developing CIP (127.4 +/- 10.5 vs 97.3 +/- 18.5, p<0.05, t-test) Patients suffering from CIP stayed significantly longer in the ICU (40.3 +/- 11.7 vs. 19.6 +/- 11.3 days, p < 0.05 t-test) with an extended time of ventilator support. (769.6 +/- 05.0 vs 295.0 +/- 134.0 hours, p<0.05, t-test). Patients of the CIP group were suffering significant longer from sepsis than patients without CIP.

CONCLUSIONS

Sepsis and catecholamine support and an increased level of urea were associated with the development of CIP. The prevention of sepsis and a modulation of the catecholamine support in order to improve microcirculatory flow may reduce the onset of CIP in patients undergoing open heart surgery.

Vascular tracheobronchial compression syndromes-- experience in surgical treatment and literature review

Between January 1988 and December 1997 a total of 22 patients (age: 8 days-46 years) were operated for vascular airway compression syndromes with respiratory insufficiency. Vascular anomalies in tracheal compression were double aortic arch in 7 patients, (2 previously operated elsewhere), right aortic arch + left ligamentum arteriosum in 1, and pulmonary artery sling in 3. Three of these patients had secondary long-segment tracheomalacia. Compression of trachea and a main bronchus existed in 2 patients with right aortic arch + left ligamentum. Isolated main bronchus obstruction was present in 9 patients (abnormal insertion of ligamentum arteriosum in 1, status post (s.p.) previous operation for PDA in 4, s. p. surgery for coarctation in 1, right aortic arch + left ligamentum arteriosum in 2, and right lung aplasia + left ligamentum in 1). 3 of these cases had secondary long-segment bronchomalacia. All patients had a complex respiratory anamnesis [long-term intubation in 7, s.p. tracheostomy in 2 (over 3 months - 3 years), and progressive respiratory insufficiency in 13). In tracheal compression, surgical correction included transsection of the underlying ring or sling components (with additional anterior aortic arch translocation in 5 patients resection-reimplantation of left pulmonary artery in 3, segmental tracheal resection in 1, and external tracheal suspension in 2). In the 2 cases with compression of the trachea and a main bronchus, aortic "extension" by a prosthetic tube was necessary. In isolated main bronchus obstruction, surgical decompression basically consisted of transsection of the ligamentum arteriosum or resection of its scarry remnant forming the "corner point" of a compression between aorta and pulmonary artery. In 3 patients with secondary long-segment malacia, additional external bronchus suspension was performed. Effective decompression and re-expansion of the airway segment concerned was achieved, and was demonstrated by intraoperative endoscopy in all patients. There were 3 postoperative deaths (sepsis 2; massive, irreversible edema of the tracheal mucosa 1). Of the 19 surviving patients 16 could be extubated between the 1st and 17th (mean = 7.5) postoperative day. In 1 case the preoperative long-term tracheostomy had to be left in place for inoperable additional laryngeal stricture. 2 patients had to be reoperated (segmental cervical tracheal resection after 5 months for primary long-term intubation-related subglottic stenosis in 1, esophageal decompression for residual dysphagia after 57 months related to a traction phenomenon at the right descending aorta in the other), both with gratifying results. In all other patients clinical, endoscopic, and radiographic examinations (follow-up = 2 months - 6 years) demonstrate good results.

Selective vasodilation by nitric oxide inhalation during sustained pulmonary hypertension following recurrent microembolism in pigs

PURPOSE

This study establishes a new model of sustained pulmonary hypertension induced by recurrent microembolism in pigs and evaluates the effects of nitric oxide (NO) inhalation in this model.

MATERIALS AND METHODS

Fourteen pigs were embolized under general anesthesia with 300-microm microspheres intravenously three times over a period of 7 weeks. Four pigs served as untreated controls. Hemodynamic and gas exchange measurements were performed on days 1 and 7 after the last embolization.

RESULTS

Recurrent microembolism caused sustained pulmonary hypertension (mean pulmonary artery pressure [MPAP] 26 +/- 2 and 18 +/- 1 mm Hg on days 1 and 7, respectively) compared with the control group (MPAP 13 +/- 1 mm Hg each for days 1 and 7; P < .05, respectively). Right heart hypertrophy was present at autopsy as indicated by an increase in minimal myocyte diameter. Inhaled NO (5 and 40 parts per million [ppm]) was administered on days 1 and 7. On both days, inhaled NO significantly reduced MPAP and pulmonary vascular resistance without affecting systemic hemodynamics. There were no differences in responses to 5 and 40 ppm inhaled NO.

CONCLUSION

We conclude that recurrent microembolization in pigs provides a reliable model of sustained pulmonary hypertension. In this model inhaled NO is a selective pulmonary vasodilator, indicating that active vasoconstriction significantly contributes to sustained pulmonary hypertension after recurrent microembolism.

Circulating interleukin-1 receptor antagonist (IL-1RA) serum levels in patients undergoing orthotopic heart transplantation

In a pilot study we determined the serum levels of circulating interleukin-1 receptor antagonist (IL-1ra) in patients undergoing orthotopic heart transplantation and in control patients scheduled for open heart surgery without allograft transplantation. Blood samples were obtained from 12 transplant recipients and 7 controls prior to the operative procedures to determine baseline values. Serum levels of IL-1ra were measured within 12 h of decrossclamping of the aorta and every 24 h for the following 14 days. Endomyocardial biopsies were obtained weekly for the 1st month after transplantation. Compared to baseline values, IL-1ra serum levels 12 h after decrossclamping of the aorta were significantly higher both in the control group (507 +/- 165 vs 3980 +/- 452 pg/ml, P < 0.01) and among the transplant recipients (413 +/- 180 vs 4117 +/- 459 pg/ml, P < 0.01) IL-1ra levels remained significantly elevated for 2 and 5 days, respectively. There were no significant differences in the IL-1ra serum levels between the two groups throughout the observation period. Endomyocardial biopsies of two patients showed acute allograft rejection, Billingham grade IIIa and IIIb, respectively. In both cases, the rejection episodes were accompanied by a renewed and more pronounced elevation in the IL-1ra serum levels beyond 4000 pg/ml for at least 2 days. These preliminary results indicate that IL-1ra may be a nonspecific immune marker during the first few days after orthotopic heart transplantation and cardiopulmonary bypass. Moreover, renewed, prolonged increases in IL-1ra appear to be associated with rejection. Further studies are needed to confirm the predictive value of IL-1ra in the detection of acute allograft rejection.

Interruption of bronchial circulation leads to a severe decrease in peribronchial oxygen tension in standard lung transplantation technique

OBJECTIVE

In clinical practice lung transplantation is the only procedure where the transplanted organ is left without its own arterial perfusion. With the interruption of the bronchial arteries the nutritive support is dependent on collateral flow by the pulmonary artery and the oxygen tension of desaturated central venous blood, representing an abnormal physiology.

METHODS

To analyze this problem systematically, we used a standard single left lung transplantation model in the pig (n = 12). In accordance with the clinical standard, lung preservation was performed with modified Euro-Collins solution with addition of prostacycline. The duration of ischemia was set to 4 h. Before and after single left lung transplantation tissue oxygen tension in the peribronchial tissue was measured with Licox tissue pO2 microprobes. For validation, the myocardial tissue oxygen tension was recorded simultaneously. The hemodynamic assessment included continuous flow measurement of the left and right pulmonary artery using Transsonic ultrasound flow probes. After transplantation the animals were observed for 4 h. For hypothetic augmentation of collateral blood flow to the peribronchial tissue we administered Nitric oxide (10 ppm) to the ventilation in six pigs (group B). Six pigs (group A) served as a control without the addition of nitric oxide (NO). All pigs were ventilated with a FiO2 of 0.5 resulting in paO2 values between 160 and 200 mmHg.

RESULTS

In both groups single lung transplantation led to a significant decrease in peribronchial tissue oxygen tension throughout the observation period. Pre-Tx values of peribronchial tissue oxygen tension (38.31 +/- 6.56 mmHg) decreased to 9.72 +/- 2.55 mmHg in group A and 10.3 +/- 3.61 mmHg in group B after 4 h, which could not be altered by a FiO2 of 1.0 (P < 0.0001). The addition of NO in group B led to a significantly augmented flow in the left pulmonary artery (0.63 +/- 0.31 l/min in group B vs. 0.46 +/- 0.26 l/min group A, P < 0.001) representing 67 vs. 49% of the pre-Tx flow in groups B and A, respectively, but the peribronchial tissue oxygen tension was not influenced (P > 0.05). In both groups A and B, the central venous pO2 did not differ in the postoperative period (41.83 +/- 3.27 mmHg group A vs. 43.26 +/- 2.98 mmHg group B) and was kept in a comparable range to the pretransplantation values (45.23 +/- 3.41 mmHg pre-Tx).

CONCLUSIONS

The persistence of a very low peribronchial tissue oxygen tension in the early phase after lung transplantation cannot be influenced by improved pulmonary artery flow and solely relates to the central venous pO2, which cannot be augmented by the addition of NO. This mechanism might be a trigger for anastomotic healing problems, infectious complications and later development of obliterative bronchiolitis (OB).

Critical illness polyneuropathy: a new iatrogenically induced syndrome after cardiac surgery?

OBJECTIVE

Critical illness polyneuropathy (CIP) is a newly described severe complication after open heart surgery leading to tetraplegia for weeks to months. The purpose of the study was to gather further information on critical illness polyneuropathy developing in patients after cardiac surgery and to evaluate the hypothetical risk factors possibly related to the onset of this neurological disorder.

METHODS

From July 1994 to October 1995, 7 out of 1511 patients undergoing open heart surgery developed critical illness polyneuropathy, which was diagnosed on the basis of electromyographic and nerve conduction features. The only common clinical finding was an intensive care unit (ICU) stay beyond seven days, therefore a similar group of 37 patients staying longer than seven days in the intensive care unit during the same period of time was evaluated and retrospectively compared to the 7 patients developing critical illness polyneuropathy. Univariate analysis of several traits was performed to evaluate possible risk factors.

RESULTS

4 Out of 7 patients in the CIP group died, all due to multiple organ failure, in contrast to 3/37 patients in the control group, again due to multiple organ failure. Patients developing CIP were staying significantly longer in the ICU (62+/-3 versus 14+/-8 days, P < 0.01) and had a significantly longer time on ventilator support (50+/-28 versus 7+/-13 days, P < 0.01) The incidence of sepsis was significantly higher in the CIP group than in the control group (85.7 versus 10.8%, P < 0.01). Compared to the control group the proportion of patients receiving corticosteroids (100 versus 10.8%, P < 0.01) and increased dosages of epinephrine and norepinephrine was higher in the CIP group (85.7 versus 35.1%, P < 0.05). Furthermore, the proportion of patients requiring chronic venovenous hemodiafiltration was significantly elevated in the CIP group (85.7 versus 5.4%, P < 0.01).

CONCLUSIONS

CIP, despite it's benign nature due to it's spontaneous remission in patients who survive, is a disturbing complication following cardiac surgery which is associated with high mortality, a prolonged stay in the ICU, as well as an extended time on ventilator support. Interventions like chronic hemodiafiltration, the application of corticosteroids and the administration of high doses of catecholamines are more frequent in patients with CIP. Whether this indicates a causal relationship remains to be elucidated.

External stabilization of long-segment tracheobronchomalacia guided by intraoperative bronchoscopy

BACKGROUND

Symptomatic obstruction of long-segment tracheal or bronchial portions either related to congenital instability or secondary to vascular compression are rare malformations, which remain difficult to manage. A method of external tracheal or bronchial stabilization is described.

METHODS

From July 1992 to April 1995, 7 children (age range, 4 months to 4 years; mean age, 19 months) and 1 adult (age, 46 years) were operated on for severe respiratory insufficiency. In 4 cases of congenital tracheal instability, 2 children had associated type IIIb esophageal atresia. Both children with esophageal atresia had previous operations (two and three times, respectively): 1 child had aortopexy and division of a patent ductus arteriosus and another child had distal tracheal resection elsewhere, both without relief of malacia. All children were intubated and ventilated since birth for 11 to 15 months. Secondary tracheobronchomalacia due to vascular compression was seen in 4 patients caused by double aortic arch (n = 2) and persisting ligamentum arteriosum after previous ligation of a patent ductus arteriosus (n = 2), with 1 child ventilated thereafter for 5 months. Operation was performed with the aid of extracorporeal circulation in all patients but 1, and consisted of transection of vascular rings and persistent ligamentum Botalli (n = 5), closure of multiple ventricular septal defects (n = 1) and extensive mobilization of the tracheobronchial tree as well as the great arteries. External stabilization of the severely dysplastic distal trachea (n = 6) or left main bronchus (n = 2) was achieved by suspending the malacic segment within an oversized and longitudinally opened ring-reinforced polytetrafluoroethylene prosthesis. Multiple plegeted sutures were placed extramucosally to the dysplastic tracheal wall and the dyskinetic pars membranacea, as well as to the polytetrafluoroethylene prosthesis in a radial orientation. Guided by simultaneous video-assisted bronchoscopy, reexpansion of the collapsed segments was achieved by gentle traction on the sutures while tying.

RESULTS

Stenosis-free tracheobronchial reexpansion was achieved in all patients, as seen on repeated bronchoscopies during hospitalization and thereafter. All patients were extubated within 1 to 12 days after the operation. There was one late death, unrelated to the procedure, in a 31-month-old child 20 months after the operation. All other patients are free of stridor and in excellent clinical condition 21 to 54 months (mean, 38 months) thereafter.

CONCLUSIONS

The presented method of bronchoscopically guided external tracheobronchial suspension within a ring-reinforced polytetrafluoroethylene prosthesis immediately relieves severe malacia of the trachea or main bronchi in infants as well as adults without necessitating resection. Midterm preliminary data suggest that growth potential of the affected segment exists within the oversized polytetrafluoroethylene prosthesis.

Doubly angled pleural drain circumventing the transcostal route relieves pain after cardiac surgery

Standard pleural drainage after cardiac surgery is accomplished through the intercostal space and the divided parietal pleural, often causing severe additional chest pain. To circumvent this route of insertion a doubly angled polyvinyl chloride drain was developed which can be placed via the median approach through the rectus abdominis muscle just beside the anterior mediastinal drains without irritation of the heart and parietal pleura into the phrenico-costal sinus.

Direct visualization of leukocyte/endothelial cell interaction during extracorporeal circulation (ECC) in a new animal model

OBJECTIVE

The clinical complications of extracorporeal circulation (ECC) have been linked to a systemic activation of cellular and humoral components and to a dysregulation of the microcirculatory compartment. Since to date only in vitro methods exist for evaluation, we developed an animal model to study the effects of ECC on the microcirculation. To establish the model, we assessed whether these effects are dependent on the duration of ECC.

METHODS

Intravital fluorescence microscopy was used on the dorsal skinfold chamber preparation in chronically instrumented, awake Syrian golden hamsters. ECC was realized using a micro-rollerpump and a silicon tube shunting blood between the carotid artery and the jugular vein. ECC was performed in three groups for various times (2, 10 and 20 min) after application of heparin at 300 IU/kg body wt. In hamsters, the application of high-dose heparin releases endothelial bound superoxide dismutase (SOD), a natural scavenger of oxygen-derived free radicals. Protocol II assigned two groups receiving heparin at different doses of 50 and 2000 IU/kg body wt.

RESULTS

ECC for 2 min served as control to exclude effects from hemodilution and resulted in a minimal induction of leukocyte/endothelial cell interaction. Isovolemic ECC for 20 min resulted in an increase in rolling (from 11 +/- 3 to 38 +/- 20%, mean +/- S.D., P < 0.05) and adherent leukocytes (from 19 +/- 16 to 215 +/- 145 cells/mm2, mean +/- S.D., P < 0.05) in postcapillary venules. Microhemodynamic parameters and functional capillary density were not significantly affected. Arterial blood pressure and heart rate were stable. Heparin at 2000 IU/kg inhibited post-ECC leukocyte adhesion following ECC, whereas 50 IU/kg showed no protective effects.

CONCLUSIONS

Leukocyte/endothelial cell interaction, induced by blood contact with synthetic surfaces, was directly visualized in vivo. The number of adherent leukocytes was dependent on the duration of ECC. The application of high-dose heparin followed by release of SOD almost prevented leukocyte activation, suggesting a formation of oxygen free radicals during ECC. The new application of the hamster model may allow to study the underlying pathomechanisms and to develop therapeutic/prophylactic strategies to avert problems associated with ECC.

Spinal cord protection using hypothermic cardiocirculatory arrest in extended repair of recoarctation and persistent hypoplastic aortic arch

OBJECTIVE

In recurrent coarctation collateral circulation may not be sufficient to maintain adequate perfusion of the lower body during the period of surgical repair. Different techniques such as interposition of a Gott-shunt, use of left heart bypass or hypothermic cardiocirculatory arrest are used to prevent spinal cord injury.

METHODS

Twenty-eight operations for recurrent coarctation were performed in 26 patients following end-to-end anastomosis (58%), patch plasty (21%), subclavian flap aortoplasty (14%) and graft interposition (7%). Associated cardiac defects were present in 77% of the patients. Eleven patients who had adequate (> 50 mmHg) distal perfusion pressure during a test occlusion were operated on using simple cross-clamping (group I, mean age 8.5 +/- 3.8 years). In group I, end-to-end anastomosis was performed in nine patients and graft interposition in two patients. In 17 cases (including two patients from group I) with insufficient collateral circulation and with persistent hypoplasia of the arch, hypothermic cardiocirculatory arrest was used (group II, mean age 12.8 +/- 9.6 years). In group II end-to-end anastomosis was performed in three patients and graft interposition in 14 patients. Mean bypass-time was 116 +/- 36 min and arrest-time 33 +/- 16 min. Hypothermic cardiocirculatory arrest was begun when nasopharyngeal temperature was below 20 degrees C, corresponding to a rectal temperature of 24 +/- 3 degrees C.

RESULTS

Hypothermic cardiocirculatory arrest allowed open reconstruction of the arch and/or complete or partial replacement of the arch and the coarctation segment. In-hospital mortality was 0 and 5.9% in group I and II, respectively. The one patient who died in group II had simultaneous correction of an anomalous pulmonary venous connection and death was unrelated to the method of coarctation repair. Reversible laryngeal nerve paresis was observed in two patients in group II, no other neurologic complications were observed in either group. Postoperative gradients over the repair site were less than 20 mmHg by Doppler-echocardiography. Two patients of group I had to have a second, early reoperation because of stenosis at the anastomotic site. Reconstruction of the distal aortic arch was then performed during hypothermic cardiocirculatory arrest.

CONCLUSIONS

The use of hypothermic cardiocirculatory arrest in this special indication is a safe method which allows open reconstruction of the coarctation site and the aortic arch and protection of the spinal cord. The need for early reoperation because of inadequate repair may be reduced.

Predominant involvement of motor fibres in patients with critical illness polyneuropathy

Critical illness polyneuropathy (CIP) is a recognized cause of muscle weakness and failure of weaning from a ventilator. In order to characterize the features of CIP, we have examined 28 consecutive surgical patients with severe sepsis using bedside electrophysiology. Of the 28 patients (median APACHE II score 31), 20 developed moderate to severe CIP, as shown by the presence of moderate to severe denervation activity on resting EMG. The median nerve compound muscle action potential (CMAP) amplitudes were reduced to 3.24 (SEM 0.48) mV, while sensory nerve action potential (SNAP) amplitudes obtained from the same nerve were normal (13.1 (1.9) microV). In approximately 50% of these patients, the reduction in CMAP exceeded 50% of the lower limit of normal. Similar results were obtained from stimulation of the ulnar nerve. We conclude that CIP is a major complication in patients with severe sepsis and prolonged artificial ventilation. It predominantly involves motor fibres and thus markedly interferes with weaning from the ventilator.

Effects of metoprolol on myocardial beta-adrenoceptors and Gi alpha-proteins in patients with congestive heart failure

OBJECTIVE

In human heart failure downregulation of beta-adrenoceptors and upregulation of Gi-protein alpha-subunits (Gi alpha) results desensitization of the myocardial beta-adrenergic signal transduction pathway and reduced positive inotropic effects of catecholamines. Metoprolol treatment has been shown to restore the reduced beta-adrenoceptor density in dilated cardiomyopathy. The main objective of the present study was to investigate whether metoprolol also decreases the elevated inhibitory Gi alpha levels in patients suffering from congestive heart failure.

METHODS

Total Gi alpha was determined by pertussis toxin-catalysed ADP ribosylation and beta 1- and beta 2-adrenoceptor densities by radioligand binding in right ventricular myocardial biopsies of 18 patients with dilated or ischaemic cardiomyopathy (NYHA II-IV) before and after 3 months of therapy. Nine controls were treated with conventional therapy only [diuretics, digitalis, nitrates, angiotensin-converting enzyme (ACE) inhibitors], and nine received the beta 1-selective blocker metoprolol in addition (mean 98 +/- 12 mg daily).

RESULTS

In biopsies from patients treated with metoprolol, Gi alpha significantly decreased to 74% of predrug value and total beta-adrenoceptor increased by a selective increase in beta 1-adrenoceptors (44.7 vs 34.0 fmol mg-1 protein). These effects were accompanied by significantly increased oxygen uptake at the anaerobic threshold (8.65 vs 6.95 ml . kg-1 . min-1). In the control group no significant changes in biochemical and clinical parameters occurred.

CONCLUSION

Metoprolol partly reverses Gi alpha-upregulation and beta-adrenoceptor downregulation in heart failure, which might contribute to the clinical improvement of patients treated with beta-blockers.