Influence of the use of a bypass on the results of thoracoabdominal aortic aneurysm surgery

OBJECTIVES

To evaluate the influence of the use of a bypass on the results of thoracoabdominal aortic aneurysm surgery.

METHODS

The results of the repair of 224 thoracoabdominal aortic aneurysms operated upon between 1981 and the end of 1996 were evaluated retrospectively. In 122 cases we used simple cross-clamping (clamp and sew technique) and in 102 cases a left heart bypass (atrio-femoral or aorto-femoral) was the preferred method. Except for the use of cerebrospinal fluid drainage over the last years, the methods of spinal protection were the same in both groups. Renal protection was also identical in both groups. All aneurysms were repaired using the inlay technique.

RESULTS

Hospital mortality was 11.2%: 14.7% in cross-clamp group versus 6.8% in the bypass group (p = 0.04). Postoperative dialysis was necessary in 9.8%: 12.7% in the cross-clamp group versus 6.8% in the bypass group (p = 0.108). Paraplegia occurred in 8.4%: 7.4% in the cross-clamp group versus 9.8% in the bypass group (p = 0.517). Using the highly predictive model of Acher, there would have been 33% spinal cord lesions in the bypass group.

CONCLUSIONS

Hospital mortality, postoperative dialysis and postoperative spinal cord problems are lowered by the use of a bypass during the repair of thoracoabdominal aortic aneurysms. These results evidence that the use of a bypass is indicated in this complex operation.

Predictors of hospital mortality in type A aortic dissections: a retrospective analysis of 148 consecutive surgical patients

Reports in the literature frequently concern miscellaneous types of dissections. This makes correct interpretation of data difficult. In order to assess the determinants of hospital mortality, the results of 148 consecutive patients over a 23-year period, all operated on for a type A dissection, were reviewed. Mean(s.d.) age was 56(13.1) years, 64% were male. An acute dissection (surgery within 14 days after onset of symptoms) was performed in 139 patients. Stigmata of the Marfan syndrome were present in 6.1% (n = 9). Peripheral vascular ischaemic complications were observed in 27.7%. Nowadays, diagnosis is primarily confirmed using transoesophageal echocardiography (75 correct diagnoses among 76 performed). Operation consisted of repair or replacement of the ascending aorta. Resuspension of the aortic valve was performed in 74 patients, and arch replacement in 25. In 74 patients, distal repair was done under deep hypothermic circulatory arrest. Hospital mortality rate was 23.6% (35 patients), though mortality rate calculated over the period 1990-1993 was 17.4% (P = n.s.). Univariate analysis revealed the following variables to be statistically significant predictors of hospital mortality (P < 0.05): preoperative ischaemic complications, preoperative resuscitation, haemopericardium, postoperative neurological complications, rethoracotomy, renal insufficiency and intestinal ischaemia. Multivariate stepwise logistic regression indicated preoperative resuscitation, postoperative haemodialysis and postoperative neurological complications as the only independent predictors of hospital death. Dissections arising from a primary intimal tear in the descending aorta had a more favourable outcome (P = 0.06, odds ratio 0.1). Although hospital mortality has declined over the past few years, no decline was seen in operative mortality since gelatine-resourcine-formol (GRF) glue is used as a routine. Transoesophageal echocardiography is the first choice in confirming diagnosis. Early operation is advocated, with careful haemostasis, before the development of cardiac tamponade or end-organ ischaemia, as the cornerstone of a successful treatment of a type A dissection. Reduction of neurological complications will further improve the results.

Pulmonary vascular resistance in dogs and minipigs--effects of hypoxia and inhaled nitric oxide

The pig has been reported to present with a stronger hypoxic pulmonary vasoconstriction than many other species, including the dog, but it is not known whether this is associated with a different longitudinal partitioning of pulmonary vascular resistance (PVR). We investigated the relationships between cardiac output (Q) and mean pulmonary artery pressure (Ppa) minus occluded Ppa (Ppao), and effective pulmonary capillary pressure (Pc') minus Ppao, in seven minipigs and in seven dogs in hyperoxia (FI(O2) 0.4) and hypoxia (FI(O2) 0.1), first without, then with the inhalation of 80 ppm nitric oxide (NO) to inhibit any reversible component of PVR. Pc' was estimated from the Ppa decay curve following pulmonary artery balloon occlusion. In hyperoxia, minipigs compared to dogs had (Ppa - Ppao)/Q and (Pc' - Ppao)/Q plots shifted to higher pressures. Hypoxia at each level of Q increased Ppa - Ppao in minipigs more than in dogs, and Pc' - Ppao in minipigs only. Inhaled NO reversed hypoxia-induced changes in (Ppa - Ppao)/(Q and (Pc' - Ppao)/Q plots. We conclude that the minipig, compared to the dog, presents with higher PVR and reactivity including vessels downstream to the site of Pc' as determined by the arterial occlusion technique.

[The focus in neonatology]

During the last years, neonatology has greatly improved. In the last decade, mortality and morbidity have decreased: mortality from respiratory failure of prematurity has decreased from 22% to 12%, mortality of the very low birthweight infants under 1000 g fell from 56% to 35% and mortalities related to asphyxia have diminished from 21% to 12% and to malformations from 33% to 28%. Prematurity is now the first cause of neonatal mortality. During this period, the number of babies under 1000 g has increased 4-fold and the number of multiple births increased more than 2-fold from 3% to 7% of the live births of our hospital. Attitudes towards the premature infant have changed, especially towards the extremely small (called the micropremies). The number of disabled children has increased in parallel with the better survival of the very immature newborns who till recently were not resuscitated.

Site of pulmonary vasodilation by inhaled nitric oxide in microembolic lung injury

We investigated the site of pulmonary vasodilation and associated effects on gas exchange in response to inhaled NO in acute microembolic lung injury. Pulmonary arterial (Ppa) and effective capillary (Pc') pressures versus cardiac output (Q) plots were generated in anesthetized dogs before and after, successively, (1) embolization with 100 microns glass beads, (2) administration of either a placebo (n = 5) or 80 ppm inhaled NO followed by cyclooxygenase inhibition by aspirin 1 g given intravenously and again 80 ppm inhaled NO (n = 8). Pc' was estimated from the pressure decay curve after pulmonary artery balloon occlusion. Embolism increased pulmonary vascular resistance, with a slight decrease in its precapillary component, from 77 to 66%. NO decreased Ppa at the highest levels of Q, and aspirin increased Ppa at all levels of Q. Neither NO nor aspirin affected Pc'/Q plots or pulmonary shunt. We conclude that pulmonary vascular resistance in microembolic lung injury increases at the periphery of the pulmonary arterial tree, with partial reversibility by inhaled NO and by endogenous products of the cyclooxygenase pathway upstream from the site of effective capillary resistance. Reduced pulmonary vascular tone does not improve gas exchange in this model of acute lung injury.

Reoperative aortic root surgery late after use of histo-acryl

Cardiovascular reoperations after the use of histo-acryl are extremely rare. A patient is described, who underwent an aortic root replacement according to Bentall's technique, for a postdissectional aneurysm. At that time, to achieve hemostasis, histo-acryl adhesive was applied and a Cabrol's fistula was created. Fourteen years later, a recurrent 'false', aneurysm had developed and the fistula had a hemodynamically significant left-right shunt. At reoperation, the composite graft was replaced by a cryopreserved aortic root allograft with long coronary arteries. To our knowledge, this is the first report of a cardiovascular reoperation after previous use of histo-acryl. This patient also merits attention as to the fact that it illustrates a failure of a modified Cabrol's procedure.

'In vivo' size of knitted Dacron prostheses (Gelseal) used in the thoracic aorta: a computed tomography study

When replacing the thoracic aorta, gelatin-sealed triaxial knitted Dacron prostheses are used as they have zero porosity and are easy to handle. It is known that knitted prostheses (not triaxially constructed), when implanted in the abdominal aorta or in the peripheral vessels, show a dilatation of 10-20%. The initial in vivo expansion of this prosthesis in the thoracic aorta was assessed using computed tomography scanning in 18 patients. The graft sizes used were 18mm (n = 4). 20mm (n = 5). 22mm (n = 4), 26mm (n = 1), 28mm (n = 2) and 30mm (n = 2). All patients were kept normotensive postoperatively. Computed tomography scan measurement was performed within 4 weeks of operation. using standard computed tomography equipment and no contrast. Two radiologists checked and agreed upon the slice levels and measurements compared with the manufacturer's stated size referring to internal diameter of the crimped prosthesis. The mean(s.d.) 'in vivo' size was 16.2(6)% larger. This 'true size' should be taken as the reference measurement when considering further dilatation over the period of follow-up.

Hypoxic pulmonary vasoconstriction and gas exchange in acute canine pulmonary embolism

Hypoxic pulmonary vasoconstriction (HPV) is inhibited in several models of acute lung injury. Whether HPV is preserved in pulmonary embolism is unknown. We investigated the effects of a reduction in the fraction of inspired O2 (FIO2) on pulmonary hemodynamics and gas exchange in anesthetized dogs before and after autologous blood clot pulmonary embolism. In a first group of 14 dogs, stimulus-response curves for HPV were constructed as pulmonary arterial pressure (Ppa) vs. FIO2 varied between 1.0 and 0.06 at a cardiac output (Q) kept constant at 3.5 l.min-1.m-2. Gas exchange was evaluated by using the multiple inert-gas elimination technique at FIO2 of 1.0, 0.4, and 0.1. Embolism decreased the relative magnitude of HPV, expressed as the gradient between Ppa and pulmonary arterial occluded pressure in hypoxia divided by (Ppa-pulmonary arterial occluded pressure) at FIO2 of 1.0, from 1.8 to 1.2 (P < 0.05). Retention minus excretion gradients for sulfur hexafluoride and ethane were increased by decreased FIO2 (P < 0.005 and P < 0.05, respectively) before but not after embolism. Hypoxia-induced deterioration in gas exchange before embolism was related to the amount of baseline very low ventilation-perfusion (VA/Q) ratios. Similar results were obtained in a second group of seven dogs with Q decreased to maintain Ppa at the same average value as before embolism. However, gas exchange was not affected by inspiratory hypoxia before as well as after embolism in this group, which presented with a lesser amount of baseline very low VA/Q. In both groups of dogs, increase in the FIO2 from 0.4 to 1.0 did not affect gas exchange. We conclude that 1) pulmonary embolism is associated with a partial inhibition of HPV, 2) HPV does not contribute to preserve gas exchange in pulmonary embolism, and 3) a strong HPV may deteriorate gas exchange in severe hypoxia in the presence of minor very low VA/Q inequality.

Combined carotid and coronary revascularization

A series of 295 patients with combined extracranial and coronary revascularization procedures is analyzed. Operations were combined in patients with symptomatic or severe carotid lesions. Hospital mortality was 3.5%; hospital morbidity was mainly neurological with 5% reversible neurological deficits or strokes. The independent risk factors for hospital mortality and morbidity as well as for long-term survival and morbidity were statistically analyzed. The 10-year survival was 47% and predominantly determined by the cardiac 10-year survival (61%).

Intraoperative transesophageal color-coded Doppler echocardiography for evaluation of residual regurgitation after mitral valve repair

Because mitral valve competence after mitral valve reconstruction is awkward to assess during this procedure, we evaluated in this respect transesophageal color-coded Doppler echocardiography in 23 patients undergoing mitral valve reconstruction for severe mitral regurgitation. Transesophageal echocardiographic examinations were performed after induction of anesthesia but before sternotomy (baseline), after mitral valve repair before decannulation, and at sternal closure, all at similar mean aortic pressure and echocardiographic instrument settings. The degree of mitral regurgitation by transesophageal color Doppler flow mapping was visually quantified on a 5-point scale (0 to 4), pending the left atrial extent of the regurgitant jet. This was compared with the degree of mitral regurgitation by left ventricular cineangiography performed within several weeks after operation and also visually quantified on a 5-point scale (0 to 4), with use of the right anterior oblique projection. There was good correlation between the two methods (r = 0.83; p less than 0.001). We conclude that residual mitral regurgitation, as assessed by transesophageal color flow mapping in the operating room, highly correlates with the ultimate mitral regurgitation by cineangiography. Therefore transesophageal echocardiography can be helpful for evaluation of mitral valve competence during mitral valve reconstruction, and hence, in case of repair failure, allow valve replacement in the same surgical session, thus avoiding reoperation.

Successful reoperation in a fractured convexo-concavo 70 degrees aortic Bjørk-Shiley valve

A female patient was transferred to our unit with the suspicion of fracture of her 70 degrees Bjørk-Shiley valve. A successful replacement of the broken device confirmed the diagnosis. In steep Trendelenburg position, using femoral arterial inflow, the disc could be returned into the operative field by temporarily declamping the aorta.

Surgical correction of descending thoracic aortic aneurysms with shunt or bypass techniques versus simple aortic cross-clamping

Between June, 1972, and January, 1986, 57 patients underwent resection of a descending thoracic aortic aneurysm using a shunt or bypass for distal aortic perfusion (group I, n = 29) or simple aortic cross-clamping, routinely used since mid-1983 (group II, n = 28). There was a statistically significant difference in the mean age of the patients: in group II it was 14 years higher than in group I (group I: 52.8 years, group II: 66.5 years). Of these 57 patients, 8 died in hospital (group I: 6 patients, group II: 2 patients). Hospital mortality was strongly related to preoperative rupture and the incidence of intraoperative complications. Postoperative paraplegia occurred in 3 patients, all in group I, and could be related to ligation of four or more intercostal arteries between T8 and T12. Postoperative renal failure, necessitating dialysis in 5 patients, was strongly related to intraoperative hypotension, and also to emergency procedures and pre-existing renal dysfunction. Intraoperative haemorrhage occurred more often using shunting or bypass techniques. Mortality, paraplegia and renal failure showed a decreasing trend after abandoning the use of adjunctive perfusion.

Surgical treatment of infected pseudoaneurysms after replacement of the ascending aorta

The best management of infected pseudoaneurysms after prosthetic graft replacement of the ascending aorta has not yet been established. The successful surgical treatment of three patients with this complication following replacement of the aortic valve and ascending aorta is reported. Because of the poor preoperative clinical condition of these patients, an effort was made to carry out the operative repair as expeditiously as possible. The prosthetic material was never entirely removed and replaced, but less radical operations were performed in combination with extensive and accurate debridement of the mediastinum and local antiseptic irrigation.

[Presence of extracranial cerebral arterial lesions in patients undergoing open heart surgery: a planned approach to a single stage operation (author's transl)]

The combined approach of extracranial arterial lesions in patients undergoing open heart surgery decreases the high cardiac and neurological morbidity and mortality presented by patients operated sequentially. Besides the anatomically sound simultaneous approach of arch lesions and heart surgery, both to be operated by median sternotomy, the authors present their criteria used in the selection of neurologically symptomatic and asymptomatic patients with carotid and vertebral disease to be operated simultaneously. Results in 17 personal cases are presented.