Biomedical subjects

M P Haw

Publications and source records attributed to M P Haw.

29 records · Page 2Linked to original sources

PubMed2000

Mid-term results with 1,503 CarboMedics mechanical valve implants.

BACKGROUND AND AIM OF THE STUDY: The CarboMedics bileaflet prosthetic heart valve was introduced in 1986, and first implanted by the authors in March 1991. The aim of this study was to analyze the authors' clinical experience with this valve. METHODS: Between March 1991 and October 1998, 1,503 valves were implanted in 1,350 patients (758 males, 592 female; mean age 62 +/- 13 years). Follow up was 99% complete and totaled 4,342 patient-years (pt-yr). RESULTS: The hospital mortality rate was 4.3% (59/1,350). Preoperative NYHA class (p = 0.012), emergency surgery (p = 0.03) and cardiopulmonary bypass time (p = 0.01) were significantly associated with increased risk of operative death (multiple logistic regression). Mean (+/- SEM) survival rates at one and five years were 92.0 +/- 0.7% (n = 1,109) and 80.0 +/- 1.3% (n = 335). Freedom from valve-related complications (linearized rate 5.6%/pt-yr) at one and five years was 89.5 +/- 0.8% (n = 1,031) and 76.3 +/- 1.4% (n = 284). Linearized rates for bleeding events were 2.19%/pt-yr, thromboembolic events 2%/pt-yr, operated valvular endocarditis 0.18%/pt-yr, valve thrombosis 0.14%/pt-yr and non-structural dysfunction 1.22%/pt-yr. Freedom from reoperation at one and five years was 98.5 +/- 0.3% (n = 1,107) and 97.3 +/- 0.5% (n = 334). CONCLUSION: Mid-term results demonstrate that the CarboMedics prosthetic heart valve exhibits a low incidence of valve-related complications.

Aged↗

PubMed2000

Aortic valve replacement for endocarditis: determinants of early and late outcome.

BACKGROUND AND AIM OF THE STUDY: The study aim was to determine risk factors for operative mortality, recurrent infection, reoperation and long-term survival following aortic valve replacement (AVR) for infective endocarditis. METHODS: Between 1973 and 1997, 109 patients (91 male, 18 female, mean age 52.6 years) underwent isolated AVR for infective endocarditis in our unit. Native valve endocarditis was present in 89 (81.6%) and prosthetic valve endocarditis in 20 (18.4%). Active culture-positive endocarditis was present in 53 (48.6%). Preoperatively, 99 patients (90.8%) were in NYHA classes III and IV. Indications for surgery included cardiac failure in 41 patients, valvular dysfunction in 38, vegetations in 18, sepsis in seven, abscess in six and embolism in four. Mechanical valves were implanted in 69 patients (63.3%) and bioprostheses in 40 (36.7%), including a homograft in 19 (17.4%). Follow up was complete (mean 5.8 years; range: 0-23.8 years; total 633.5 patient-years). RESULTS: The operative mortality was 10.1% (11 deaths). At ten years, freedom from recurrent infection was 94.2%, and freedom from reoperation 83.6%. Biological valve and younger age were significant adverse parameters for freedom from reoperation (p = 0.01 and p = 0.01). There have been 21 late deaths, 15 due to cardiac causes. Kaplan-Meier survival, including operative mortality, at five and ten years was 77.4% and 68.0%, respectively. On Cox proportional hazards regression, Staphylococcus aureus infection (p = 0.008) and older age (p = 0.04) were independent adverse predictors of survival. CONCLUSION: AVR for endocarditis carries a relatively high operative mortality, but can result in a satisfactory freedom from recurrent infection, reoperation and long-term survival. Analysis of our series demonstrates that implantation of a biological valve limits the freedom from reoperation and that infection by Staph. aureus reduces the probability of long-term survival.

Adolescent↗

PubMed1999

Autotransfusion of washed shed mediastinal fluid decreases the requirement for autologous blood transfusion following cardiac surgery: a prospective randomized trial.

OBJECTIVES: The National Blood Service issues 2.2 million units of blood per year, 10% of these (220000) are utilized in cardiac procedures. Transfusion reactions, infection risk and cost should stimulate us to decrease this transfusion rate. We test the efficacy of autotransfusion following surgery in a prospective randomized trial. METHODS: One hundred and twelve patients undergoing CABG, valve or CABG + valve procedures were randomized into two groups. Group A received washed postoperative drainage fluid and group C were controls. The indication for transfusion was a postoperative haemoglobin (Hb) < 10 g/l or a PCV < 30. There was no significant difference in preoperative and operative variables between the groups. RESULTS: Twenty-eight patients in group A and 46 in group C required homologous transfusion (P = 0.0008). Group A patients required 298+/-49 ml of banked blood per patient, group C 508+/-49 ml (P = 0.003). There was no difference in total blood required (volume autotransfused + volume banked blood transfused) between the groups (group A 404+/-50 ml, group C 508+/-50 ml) or in mean total mediastinal fluid drainage (group A 652+/-51 ml, group C 686+/-50ml). The mean Hb concentration was significantly higher in group A on day 1 (11.2 g/dl+/-51 vs. 10.6 g/dl+/-13 (P = 0.002)). No morbidity was associated with autotransfusion. CONCLUSION: Autotransfusion can decrease the amount of homologous blood transfused following cardiac surgery. This represents a benefit to the patient and a decrease in cost to the health service.

Aged↗

PubMed1999

Tricuspid valve replacement: bioprostheses are preferable.

BACKGROUND AND AIM OF THE STUDY: Tricuspid valve replacement (TVR) is rarely undertaken, most surgeons preferring to use conservative tricuspid valve procedures. Thus, limited data are available in patients following TVR. The purpose of this study was to analyze the early and late results in 87 patients (52 tissue valves, 35 mechanical prostheses) who underwent TVR between January 1973 and September 1996. METHODS: The patient group comprised 74 (85%) females and 13 (15%) males; mean (+/- SD) age was 59.4 +/- 12.8 years; range: 15 to 81 years). Forty-four patients (51%) had undergone at least one previous cardiac operation. There were 19 (23%) isolated TVRs, 43 (49%) triple valve replacements, and 25 (29%) double valve replacements. Total cumulative follow up was 707 patient-years (pt-yr) (tissue valves 393 pt-yr, mechanical valves 314 pt-yr); mean follow up was 8.1 years (range: 0 to 23.6 years). RESULTS: The early (30-day) mortality rate was 10.3% (n = 9; tissue 7, mechanical 2, p = 0.28). Logistic regression identified prolonged cardiopulmonary bypass time (p <0.03) and advanced NYHA functional class (p <0.007) as risk factors for operative death. No risk factors were significant on multiple logistic regression analysis. Mean (+/- SEM) survival rate was 68 +/-5.3% (n = 50) at 5 years, 52 +/- 5.9% (n = 36) at 10 years, 35 +/- 6% (n = 20) at 15 years, and 16 +/- 5.3% (n = 7) at 20 years. Freedom from tricuspid valve reoperation at 5, 10 and 15 years was 93 +/- 3.3% (n = 46), 83 +/- 5.8% (n = 33) and 71 +/- 2.8% (n = 17) respectively. Eleven patients required tricuspid valve reoperation: six mechanical valves (five for prosthetic valve thrombosis and one for mechanical failure secondary to pannus ingrowth), and five tissue valves (two for prosthetic valve endocarditis and three for prosthetic valve degeneration). Freedom from reoperation at 5, 10 and 15 years for tissue prostheses was 97 +/- 2.5%, 89 +/- 6.3% and it was 70 +/- 12%, and 86 +/- 7.4%, 74 +/- 9.9% and 68 +/-11% for mechanical prostheses. The mechanical prostheses required reoperation earlier after the initial surgery. CONCLUSIONS: We recommend the use of a bioprosthesis in the tricuspid position because of its initial durability and low reoperation rate.

Adolescent↗

PubMed1996

Successful complete tracheal resection in a three-month-old infant.

We report an infant with severe long-segment tracheal stenosis in whom the posterior trachea was formed by complete cartilage rings and the anterior trachea was almost totally formed by a solid cartilage plate. The child was successfully treated initially by complete resection of the trachea and primary end-to-end repair and subsequently with tracheal homograft transplantation for secondary stenosis.

Anastomosis, Surgical↗

PubMed1996

Pediatric tracheal homograft reconstruction: a novel approach to complex tracheal stenoses in children.

PURPOSE: Tracheal stenosis can be a life-threatening problem in children. Long-segment tracheal stenosis and recurrent tracheal stenosis are especially problematic. Tracheal homograft reconstruction represents a novel therapeutic modality for these patients. METHODS: Cadaveric trachea is harvested, fixed in formalin, washed in thimerosal (Methiolate), and stored in acetone. The stenosed tracheal segment is opened to widely patent segments proximally and distally. The anterior cartilage is excised and the posterior trachealis muscle or tracheal wall remains. A temporary silicone rubber intraluminal stent is placed and absorbable sutures secure the homograft. Regular postoperative bronchoscopic treatment clears granulation tissue. The stent is removed endoscopically after epithelialization over the homograft. Twenty-four children with severe tracheal stenosis (age 5 months to 18 years, mean +/- standard error of the mean = 8.18 +/- 1.21 years) underwent tracheal homograft reconstruction. All but one had had previous unsuccessful reconstructive attempts. Ten lesions were congenital, nine were posttraumatic, and five were due to prolonged intubation. RESULTS: Follow-up ranged from 5 months to 10 years (3.79 +/- 0.70 years). Twenty patients survive (20/24 = 83%), 16 without any airway problems. Four patients are still undergoing treatment. One patient requiring emergency extracorporeal membrane oxygenator support before the operation died 10 days after tracheal homograft reconstruction. Another patient with severe preoperative mediastinal sepsis died 3.5 months after tracheal homograft reconstruction. Two patients with functional airways died late of unrelated problems. CONCLUSIONS: Tracheal homograft reconstruction demonstrates encouraging short-term to medium-term results for children with severe recurrent tracheal stenosis. Postoperative bronchoscopic and histologic studies provide evidence of epithelialization and support the expectation of good long-term results.

Adolescent↗

PubMed1996

Tracheal reconstruction in children using cadaveric homograft trachea.

OBJECTIVE: We report the use of cadaveric human tracheal homograft in the treatment of severe long segment congenital tracheal stenosis in children. METHODS: Five children (aged 5 months-8 years) with severe life-threatening airway obstruction due to long segment congenital tracheal stenosis had failed conventional management. All were ventilator dependent or rapidly deteriorating at the time of surgery, two were on extracorporeal membrane oxygenation, and no alternative therapy was available. The stenosed trachea was removed and the posterior trachealis muscle left in situ when possible. Surgical technique involved the use of cardiopulmonary bypass in four of five cases. Stored cadaveric tracheal homograft tissue was shaped and inserted over a silastic intra-luminal stent which was kept in place for up to 3 months. Regular bronchoscopy was necessary postoperatively to clear granulation tissue, which resolved on removal of the stent. RESULTS: Four patients are all now without stents, intubation or tracheostomy. Three are without airway problems 16, 14, and 9 months after surgery and one attends for occasional dilatation of a distal tracheal stenosis, but is now at home despite other severe multiple congenital problems. One patient presented with complete disruption of the trachea and mediastinal sepsis and was supported on extracorporeal membrane oxygenation prior to surgery; this patient eventually died of airway failure and sepsis. CONCLUSIONS: The application of cadaveric human tracheal homograft to congenital tracheal stenosis is novel. Its use in five children who would otherwise have died has provided an extra therapy in an extremely difficult group of patients.

Airway Obstruction↗

PubMed1995

The effect of dietary polyunsaturated fatty acids (PUFA) on acute rejection and cardiac allograft blood flow in rats.

For six weeks, recipient (Lewis RT11) and donor rats (LBNF11/n) were fed three diets that varied only in their lipid content. Diet A (MO) contained 19.5% menhaden oil and 0.5% safflower oil and was rich in omega 3 PUFA; diet B (SO) was 20% safflower oil rich in omega 6 PUFA; and diet C (BT) was 20% beef tallow rich in omega 9 monounsaturated fatty acids and saturated fat. In the first set of graft survival studies a group fed laboratory chow was included (CHOW). Heterotopic cardiac transplantation from donor to recipient animals was performed after the six-week feeding period. The effect of these diets on cardiac allograft survival, mixed lymphocyte response, and blood flow in the rejecting grafts was investigated. The median graft survival in days was significantly prolonged in the rats maintained on either MO (12 days) or SO (14.5 days) compared with the BT (8 days)-or lab chow (7.5 days)-fed animals (P < 0.05). Cyclosporine (CsA) administered at subtherapeutic levels further increased the differences between the PUFA-fed animals and the BT-fed group. The myocardial blood flow of the rejecting allografts was measured using an 85Sr-labeled microsphere technique on the fifth posttransplant day. Flow was greatest in the MO-fed group, and both MO and SO groups had significantly higher myocardial blood flow than BT-fed rats (P < 0.05) or those bearing isografts. The allogenic mixed lymphocyte responses of peripheral blood mononuclear cells (PBMC) and splenic lymphocytes were suppressed in MO- and SO-fed groups compared with BT-fed animals. The immunosuppressive effect of dietary PUFA warrants further investigation, and their use as a possible adjunctive treatment in organ transplantation should be considered.

Acute Disease↗

PubMed1992

Dietary enrichment with omega-3 fatty acids partially protects against lipopolysaccharide-induced atrial depression in rats.

We tested the hypothesis that pretreatment with a diet enriched with omega-3 fatty acids can prevent lipopolysaccharide (LPS)-induced atrial dysfunction. Sprague-Dawley rats were fed a diet containing 20% safflower oil (control diet; CD) or 19.5% menhaden/0.5% safflower oil (experimental diet; ED). After 28 days, the animals were injected I.V. with LPS (20 mg/kg) or normal saline (S). Two hours later, the atria were harvested, connected to a force displacement transducer-amplifier-recorder system and maintained in vitro in oxygenated 37.5 degrees C Krebs-Henseleit buffer. Force of contraction indexed to body weight (FOCI; g/kg) and maximal rate of rise of contraction (dF/dt, g/sec) and relaxation (-dF/dt, g/sec) were similar in the CD-S (n = 6) and ED-S (n = 6) groups. FOCI, dF/dt, and -dF/dt were lower (P less than 0.05) in rats injected with LPS compared with rats injected with S irrespective of diet, but were significantly higher (P less than 0.05) in LPS-ED rats (n = 11) compared with LPS-CD rats (n = 11). Chronotropic and inotropic responses to graded doses (0.1, 0.5, 1.0, and 5.0 microM) of isoproterenol were not significantly different among groups. LPS-induced production of thromboxane B2 but not 6-keto-prostaglandin F1 alpha, was inhibited in ED fed rats. The ED did not enhance survival when rats were challenged with a 20 mg/kg I.V. dose of LPS. These results indicate that dietary enrichment with omega-3 fatty acids in rats partially protects against LPS-induced alterations in atrial function but does not change mortality after an LD100 dose of LPS.

6-Ketoprostaglandin F1 alpha↗

PubMed1991

Potential of parenteral and enteral nutrition in inflammation and immune dysfunction: a new challenge for dietitians.

Advances in the understanding of the interrelationship between immunology and nutrition indicate that immune dysfunction in critically ill patients is linked with nutrient deficiency and abnormal acute-phase response to illness. Immune dysfunction requires special nutrition therapy and metabolic support; immunoregulation by nutrition manipulation may lead to specific immunotherapies for defined groups of patients. The success of dietary strategies must be measured not only by metabolic indexes but also by effects on immune function. The health profession must combat immune dysfunction and inflammation for the sick and frail patients under its care.

Enteral Nutrition↗

PubMed1989

Nutrition, immune function, and inflammation: an overview.

The collective evidence suggests that nutritional insult to both cell-mediated and humoral immunity in the presence of protein-energy malnutrition contributes to abnormalities of inflammation. The primary goal of nutritional support in inflammatory disease is to provide adequate energy and protein to meet endogenous requirements for tissue repair, IL-1 production, and restored cellular function, thus preventing secondary infection. Substrate provision should aim at improving the acute phase of injury while avoiding immune dysfunction. This goal may be achieved by altering the eicosanoid pathway toward a more regulated inflammatory state. In the context of allograft response, macrophages are central to the initiation of allosensitization by virtue of their ability to present antigen to T-cells. Activated T-cells may further modulate macrophage function by the secretion of lymphokines. Manipulation of macrophage eicosanoid production by dietary omega-3 PUFA may reduce cellular immune response. (table; see text) Nutritional support should also focus on providing essential micronutrients, with their potentially immunomodulating role, as adjunctive therapy in order to protect the host from toxic effects of free-radicals and chemicals released during inflammatory events. (Feeding regimens currently under investigation and development are presented in Table 4.) By integrating dietary immunotherapy with the use of recombinant hormones, monoclonal antibodies, and various available monokines, an optimal outcome for each patient may be achieved. However, effective application of immunotherapy to nutritional supplementation will require accurate monitoring of immune function in individual patients in order to avoid inappropriate treatment.

Animals↗