1/11. The heart-pump interaction: effects of a microaxial blood pump.BACKGROUND: When we use rotary blood pumps as an assist device, an interaction takes place between the pump performance and the native heart function (native heart influences pump performance and vice versa). The interaction between native heart and rotary blood pump can be useful to predict recovery of the failing heart. methods: The rotary blood pumps used were microaxial catheter-mounted pumps with an external diameter of 6.4 mm (Impella, Aachen, germany). The pump-heart interaction was studied in five juvenile sheep with a mean body weight of 68.5 /- 8.7 kg. The pumps were introduced via the left carotid artery and placed in transvalvular aortic position. Recorded parameters were pump speed (rpm), generated flow (L/min) and differential pressure (mm Hg) obtained at high frequency rate of data recordings (25 sets of data per second). This allowed continuous analysis of the pump performance during cardiac cycle. Under clinical conditions the interaction was studied in a 60-year-old male, in whom the device was applied due to postcardiotomy heart failure after myocardial infarction. RESULTS: Heart-pump interaction was analyzed based on pump flow differential pressure. This relationship, analyzed continuously during cardiac cycle, presents as a loop. The dynamic contribution of the heart to the flow generated by the pump leads to continuous fluctuation in the pressure head and the creation of hysteresis. The improved function of the failing heart under clinical conditions after seven days of mechanical support was expressed by: increased hysteresis of the loop caused by increased gradient of flow generated during cardiac cycle, a more pronounced venticular ejection phase that indicates more dynamic heart contribution to the generated flow, and finally increased gradient of the differential pressure during cardiac cycle, caused predominantly by increased aortic pressure and decreased left ventricle pressure during diastolic phase. CONCLUSIONS: The heart-pump interaction based on the pump flow-differential pressure relationship can be useful in predicting the possibility to wean the patient from the device.- - - - - - - - - - ranking = 1keywords = pressure (Clic here for more details about this article) |
2/11. diagnosis and treatment of negative pressure pulmonary edema in a pediatric patient: a case report.This article includes a case study of a pediatric patient who presented for elective correction of a speech impediment via a frenuloplasty. The patient's history and anesthetic course will be discussed prior to the deveopment of the episode of negative pressure pulmonary edema (NPPE). The events surrounding the development and diagnosis of NPPE will be presented, and the treatment modalities will be discussed.- - - - - - - - - - ranking = 0.71428571428571keywords = pressure (Clic here for more details about this article) |
3/11. First human case of retrograde transcatheter implantation of an aortic valve prosthesis.The transcatheter route is an emerging approach to treating valvular disease in high-risk patients. The 1st clinical antegrade transcatheter placement of an aortic valve prosthesis was reported in 2002. We describe the first retrograde transcatheter implantation of a new aortic valve prosthesis, in a 62-year-old man with inoperable calcific aortic stenosis and multiple severe comorbidities. Via the right femoral artery, a Cook introducer was advanced into the abdominal aorta. The aortic valve was crossed with a straight wire, and a pigtail catheter was advanced into the left ventricle to obtain pressure-gradient and anatomic measurements. An 18-mm valvuloplasty balloon was then used to predilate the aortic valve. Initial attempts to position the prosthetic valve caused a transient cardiac arrest. Implantation was achieved by superimposing the right coronary angiogram onto fluoroscopic landmarks in the same radiographic plane. A balloon-expandable frame was used to deliver the valve. After device implantation, the transvalvular gradient was <5 mmHg. The cardiac output increased from 1 to 5 L/min, and urine production increased to 200 mL/h. The patient was extubated on the 2nd postimplant day. Twelve hours later, he had to be reintubated because of respiratory distress and high pulmonary pressures. His condition deteriorated, and he died of biventricular failure and refractory hypotension on day 5. Despite the severe hypotension, valve function was satisfactory on echo-Doppler evaluation. In our patient, retrograde transcatheter implantation of a prosthetic aortic valve yielded excellent hemodynamic results and paved the way for further use of this technique in selected high-risk patients.- - - - - - - - - - ranking = 0.28571428571429keywords = pressure (Clic here for more details about this article) |
4/11. Cardiopulmonary effects of severe thoracic subcutaneous emphysema.Isolated subcutaneous emphysema appeared to cause significant pulmonary dysfunction in a traumatized child with no demonstrable intrinsic pulmonary injury or disease. We developed an animal model of severe thoracic subcutaneous emphysema to determine whether it alters pulmonary-thoracic compliance such that ventilation-perfusion relationships or cardiac performance are affected adversely. Twelve anesthetized, mechanically ventilated swine were studied. Baseline measurements and calculations included intrapulmonary shunt fraction (Qsp/Qt), total static pulmonary-thoracic compliance, thermodilution cardiac output, systemic and pulmonary arterial pressures, and mean pulmonary arterial occlusion pressure. Measurements and calculations were repeated after each of three consecutive injections of 400 cc of air into the tissue over the sternum. Comparison of the baseline values with those after the injections showed no increase in Qsp/Qt and no change in any other variable (p less than 0.05). We conclude that, in this model, isolated thoracic subcutaneous emphysema does not adversely affect cardiopulmonary function during positive pressure ventilation.- - - - - - - - - - ranking = 0.42857142857143keywords = pressure (Clic here for more details about this article) |
5/11. Opiate-antagonist reversal of neurological deficits--experimental and clinical studies.The proximal left M1 and the common trunk of A2 were clipped in 12 adult dogs. naloxone was injected after placing the clips onto 6 dogs. Neither the systemic blood pressure nor the local cerebral blood flow were influenced by naloxone. In another group of 6 dogs with chronic right hemiplegia, naloxone proved passably effective in improving the hemiplegia. Eight patients with neurological deficits of various etiologies were administered levallorphan. The improvement in motor performance and/or elevation of mental activity was observed more or less in all but 2 of the patients. It was considered that the effect of opiate antagonists is based partially on the facilitation of synaptic transmission exaggerated by the arousal response.- - - - - - - - - - ranking = 0.14285714285714keywords = pressure (Clic here for more details about this article) |
6/11. Tension pneumoperitoneum. A cause of acute aortic occlusion.Massive accumulation of intraperitoneal air may result in an entity known as tension pneumoperitoneum. The patient usually complains only of abdominal fullness, and the abdomen becomes ballooned, barrel-shaped, and tympanic in all quadrants. Upward displacement of the diaphragm may cause respiratory embarrassment. There may also be diminished venous return due to compression of the inferior vena cava. Abdominal paracentesis may be necessary to improve respiratory exchange before laparotomy. In one patient with a perforated peptic ulcer and tension pneumoperitoneum, an enormous increase in intra-abdominal pressure apparently led to acute aortic occlusion. This particular complication of tension pneumoperitoneum has not previously been reported, to our knowledge. The clinical findings of aortic occlusion were reproduced in a canine model by insufflation of air into the abdomen. An intra-abdominal pressure of 100 mm Hg resulted in loss of the femoral pulse wave measured by an indwelling arterial catheter.- - - - - - - - - - ranking = 0.28571428571429keywords = pressure (Clic here for more details about this article) |
7/11. External stent for repair of secondary tracheomalacia.tracheomalacia was created in anesthetized piglets by submucosal resection of 3 to 5 tracheal cartilages. Measurements of airway pressure and flow showed that expiratory airway resistance is maximal at low lung volumes and is significantly increased by creation of the malacic segment. Cervical flexion increases expiratory airway resistance, whereas hyperextension of the neck reduces resistance toward normal. External stenting of the malacic segment reduces expiratory airway resistance, and the combination of external stenting and hyperextension restores airway resistance to normal except at low lung volume. Two patients with secondary tracheomalacia required tracheostomy and could not be decannulated after the indication for the tracheostomy was corrected. Both were successfully decannulated after external stenting of the malacic segment with rib grafts. Postoperative measurements of expiratory pulmonary resistance show a marked decrease from preoperative measurements. External stenting of symptomatic tracheomalacia reduces expiratory airway resistance by supporting and stretching the malacic segment and is preferable to prolonged internal stenting or tracheal resection.- - - - - - - - - - ranking = 0.14285714285714keywords = pressure (Clic here for more details about this article) |
8/11. Pancreatic duct obstruction with an acrylate glue: a new method for producing pancreatic exocrine atrophy.Ten dogs have been used in a study which demonstrates the feasibility of producing total pancreatic duct obstruction with alkyl-alpha-cyanoacrylate glue. Low pressure injection of glue into the pancreatic duct has led to a reproducible pancreatic atrophy with preservation of the islets. A sharp rise in serum amylase was noted in each dog, but at autopsy examination at monthly intervals after the operation, no evidence of chronic pancreatitis was observed. None of the dogs was rendered diabetic. The success of the experimental technique raises the possibility that such a technique might be useful in the management of human chronic pancreatitis as an alternative to pancreatic resection, and the operation has been performed on three patients so far.- - - - - - - - - - ranking = 0.14285714285714keywords = pressure (Clic here for more details about this article) |
9/11. The multipoint contact plate in fracture treatment of the atrophied mandible: animal study and clinical application.Rapid consolidation of osseous fractures requires stable immobilization of the fragments. In the atrophied mandible, the nutrient supply should be ensured by protecting the periosseous soft tissue, i.e., the periosteum. In the conventional placement of osteosynthesis plates, however, the subimplant nutrition is restricted because of the high surface pressure between the osteosynthesis plate and bone. In order to improve the subimplant nutrient supply, we designed a new osteosynthesis plate with a "knobbed" underside enabling multipoint contact. Histomorphologic comparative studies were conducted on 16 Gottingen minipigs with an average weight of 47.5 /- 8 kg. In each minipig, one side of the mandible was fractured and one side was left intact. One side of each mandible was plated with a six-hole dynamic multipoint contact plate and the other side with a conventional plate. The plates were applied, either epiosseous or epiperiosteal, with bicortical screws under defined torque. The results demonstrate the advantages of multipoint contact plates over the conventional ones and create the clinical basis for a "bio-logical" plate design that allows callus to grow between the knobs and therefore provide adequate nutritional and vascular supply. The plate's knobbed profile also promotes extraosseous venous drainage without impeding intraosseous fluid flow. This plate is the logical choice for rapid fracture consolidation in the high-grade atrophied mandible.- - - - - - - - - - ranking = 0.14285714285714keywords = pressure (Clic here for more details about this article) |
10/11. Transvitreal endocyclophotocoagulation.PURPOSE: Transvitreal endophotocoagulation of the ciliary processes is a little-used option for eyes with refractory glaucoma. No histopathologic studies of animals or humans have described its effects. We sought to characterize this cilioablative procedure in an animal model, examine its effects in human eyes histopathologically, and evaluate its clinical safety and efficacy in a large series of patients with long-term follow-up. methods: ANIMAL MODEL: Rabbit eyes were treated with lensectomy, vitrectomy, and transvitreal photocoagulation of the ciliary processes. Eyes were enucleated immediately after surgery and at weekly intervals up to 1 month. light and electron microscopic evaluation of histopathologic changes was performed. Human Eyes: The pathology laboratory files were searched for cases with a history of endocyclophotocoagulation prior to enucleation, and three eyes were identified. Histopathologic sections were retrieved and examined. Clinical Series: A retrospective clinical review was performed of a single surgeon's experience with endolaser to the ciliary processes, including all cases with adequate data on ocular history, preoperative and postoperative visual acuity, intraocular pressure (IOP), and glaucoma medications, and details of surgery. Only eyes with at least 6 months' follow-up were included. RESULTS: ANIMAL MODEL: Histopathologic examination of rabbit eyes treated with endocyclophotocoagulation demonstrated acute changes of ciliary process destruction, proteinaceous exudate, stromal edema, nuclear pyknosis, and pigment dispersion. Vascular congestion was seen with some hemorrhage. Later, replacement by fibrous or fibrovascular scar developed with loss of the pigmented and nonpigmented ciliary epithelia, absence of ciliary architectural elements, and pigment rounding and clumping. Human Eyes: Histopathologic examination of enucleated human eyes revealed total ablation of the ciliary processes with fibrosis and pigment clumping in areas of treatment. Abrupt transitions between treated and untreated regions could be identified. In some areas fibrocellular membrane proliferation was found extending over the scars that replaced the ciliary processes. Clinical series: Seventy-three patients were identified ranging in age from 2 to 85 years (mean, 57.7), with follow-up of 6 to 130 months (mean, 28.6). Mean number of previous operations was 3.5; mean number of previous glaucoma operations was 1.3. Preoperative mean IOP was 38 mmHg (range, 19 to 75), postoperative mean IOP was 16 mmHg (range, 1 to 50). At 6 months, 58 of 72 eyes (81%) with available IOP data had IOP greater than 5 mmHg and less than 22. At 12 months 48 of 55 (87.3%) were successfully controlled by these criteria, and at last follow-up 50 of 73 (68%). Fifty-six of 73 eyes (77%) were considered clinically stable at the last follow-up in terms of visual acuity, anatomic integrity, and IOP < or = 23 off all glaucoma medications. visual acuity was stable or improved in 53 of 73 eyes (73%). Complications developed in 9 eyes (12%), including IOP < or = 6 mmHg in 6 eyes (8.2%), peripheral choroidal effusion in 4 (5.5%), fibrinous anterior chamber reaction in 3 (4.1%), phthisis in 2 (2.7%), and choroidal hemorrhage in 1. Thirty-five eyes had penetrating keratoplasty performed before or at the same time as endolaser (an average of 2.14 grafts each), graft rejection occurred in 4 eyes (11%), and long-term failure of grafts occurred in 11 of 35 (31%). In 31 eyes, additional surgical procedures were performed at the time of endocyclophotocoagulation. CONCLUSIONS: Endocyclophotocoagulation successfully ablates the ciliary processes, which are replaced with fibrous scar. Surgical results compare favorably with other methods of glaucoma therapy in complicated eyes in terms of IOP control, visual preservation, and complication rate. Endolaser to the ciliary body was especially successful in glaucomatous eyes after keratoplasty, although corneal graft prognosis- - - - - - - - - - ranking = 0.14285714285714keywords = pressure (Clic here for more details about this article) |
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