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Biomedical subjects

John W Hammon

Publications and source records attributed to John W Hammon.

14 recordsLinked to original sources
PubMed2005

Single crossclamp improves 6-month cognitive outcome in high-risk coronary bypass patients: the effect of reduced aortic manipulation.

OBJECTIVE: We hypothesized that a strategy that reduced aortic manipulation would reduce the incidence of cognitive deficits in patients undergoing coronary artery bypass grafting compared with the "traditional" approach and that neurobehavioral outcomes with the reduced aortic manipulation strategy would approach those obtained with off-pump coronary artery bypass surgery. METHODS: Consenting high-risk patients (those with older age, diabetes, or hypertension) scheduled for coronary artery bypass grafting and cardiopulmonary bypass were randomly assigned to 1 of 2 aortic management protocols: (1) a traditional approach in which distal anastomoses were accomplished while the aorta was crossclamped but in which proximal anastomoses were sewn while a partial occlusion clamp was applied to the aorta (multiple aortic clamping group) or (2) a reduced aortic manipulation approach in which the aorta was clamped a single time with a reduced-pressure clamp (single aortic clamping group) and the partial occlusion clamp was not used. A contemporaneous group of patients undergoing off-pump coronary artery bypass surgery without cardiopulmonary bypass was also enrolled. Subjects in all 3 groups underwent neurologic and neuropsychological testing before and after surgery. After randomization, patients assigned to either approach could be changed to another strategy if the attending surgeon determined that patient safety demanded this change. The study design anticipated that surgical techniques would evolve over the course of patient enrollment and anticipated that some patients would have intraoperative echocardiographic findings that would demand that the traditional approach (eg, severe aortic atherosclerosis) or the reduced manipulation protocol (eg, severe ischemia or poor left ventricular function) be abandoned. Thus, an unequal distribution of patients was expected. By surgeon decision, 20 of 84 multiple aortic clamping patients crossed over to single aortic clamping, and 3 of 85 single aortic clamping patients switched to multiple aortic clamping. Eligible patients had a battery of neuropsychological tests before surgery and at 6 months after surgery. A 20% decrement in 2 or more tests was defined as a neuropsychological deficit. RESULTS: [table: see text]. CONCLUSIONS: A surgical strategy designed to minimize aortic manipulation can significantly reduce the incidence of cognitive deficits in coronary artery bypass grafting patients compared with traditional techniques. In this series, the results of the reduced aortic manipulation strategy were not significantly different from those in patients having off-pump coronary artery bypass surgery, thus emphasizing surgical technique as the primary cause of brain damage in coronary artery bypass grafting patients.

Aged↗
PubMed2005

Does the combination of aprotinin and angiotensin-converting enzyme inhibitor cause renal failure after cardiac surgery?

BACKGROUND: Aprotinin use in cardiac surgery has been associated with mild elevations in serum creatinine but generally has not been associated with an increase in the risk of acute renal failure. In the presence of angiotensin-converting enzyme (ACE) inhibitors, however, aprotinin may contribute to significant reductions in glomerular perfusion pressure. The purpose of this study was to test the hypothesis that the combination of ACE inhibitors and aprotinin cause renal failure after cardiac surgery. METHODS: The study consisted of a retrospective investigation of all adult patients undergoing coronary artery bypass graft, valve, or combined procedures during the years 2000 to 2002 at a single institution. Aprotinin was administered selectively for reoperations, combined procedures, and other operations deemed to be at higher risk for bleeding. Excluded from analysis were patients with preoperative serum creatinine greater than 1.5 mg/dL, a history of renal failure, emergent or salvage procedures, preoperative use of intraaortic balloon pump, and off-pump procedures. Perioperative renal failure was defined as creatinine greater than 2.0 mg/dL within 72 hours of surgery. Preoperative demographic and intraoperative variables were analyzed with univariate and logistic regression analysis with odds ratio (OR) and bootstrap validation. RESULTS: A total of 1,209 patients were included. The incidence of perioperative renal failure was 3.5%, and mortality in this group was 48%. Controlling for other demographic and intraoperative variables that may affect renal function (age, sex, diabetes mellitus, hypertension, New York Heart Association class, prior cardiac surgery, valve procedures, cardiopulmonary bypass time, aortic cross-clamp time, lowest hematocrit during cardiopulmonary bypass, transfusions) the preoperative use of ACE inhibitors along with intraoperative use of aprotinin was significantly associated with acute renal failure (OR 2.9, 95% confidence interval [CI]: 1.4 to 5.8, p < 0.0001). The effect of either drug alone was not significant. Other identified risk factors included age (OR 1.2 per year, CI: 1.01 to 1.5, p = 0.035), valve procedure (OR 2.7, CI: 1.3 to 5.7, p = 0.016), lowest hematocrit on cardiopulmonary bypass (OR 2.2, CI: 1.6 to 3.2, p < 0.0001), and transfusions of red blood cells (OR 1.04 per unit, CI: 1.02 to 1.06, p < 0.0001) and platelets (OR 1.7 per unit, CI: 1.2 to 2.4, p = 0.001). CONCLUSIONS: The combination of preoperative use of ACE inhibitors and intraoperative use of aprotinin should be avoided in cardiac surgery.

Acute Kidney Injury↗
PubMed2005

Attempted control of hyperglycemia during cardiopulmonary bypass fails to improve neurologic or neurobehavioral outcomes in patients without diabetes mellitus undergoing coronary artery bypass grafting.

OBJECTIVE: Hyperglycemia worsens outcomes in critical illness. This randomized, double-blind, placebo-controlled clinical trial tested whether insulin treatment of hyperglycemia during cardiopulmonary bypass would reduce neurologic, neuro-ophthalmologic, and neurobehavioral outcomes after coronary artery bypass grafting. METHODS: Three hundred eighty-one nondiabetic patients undergoing isolated coronary artery bypass grafting were given infusions of insulin or placebo when their blood glucose concentration exceeded 100 mg/dL during cardiopulmonary bypass. The primary outcome measure was the combined incidence of new neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death observed at 4 to 8 days postoperatively. This same measure was assessed secondarily at 6 weeks and 6 months. Length of hospital stay was also compared as a secondary assessment. RESULTS: The 2 groups were well matched at baseline. The insulin-treated group had significantly lower blood glucose concentrations during bypass. Sixty-six percent of subjects in the insulin-treated group and 67% of subjects in the control group demonstrated a new or worsening neurologic, neuro-ophthalmologic, or neurobehavioral deficit or neurologic death at the 4- to 8-day assessment. Outcomes were also similar in the 2 groups at 6 weeks (37% and 39% incidence, respectively) and 6 months (30% and 25%, respectively). Median lengths of stay were 7 and 6 days, respectively, in the treatment and control groups. None of these outcome differences was statistically significant. CONCLUSION: Attempted control of hyperglycemia during cardiopulmonary bypass had no significant effect on the combined incidence of neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death and failed to shorten the length of hospital stay. These results do not contradict those of other studies showing that aggressive control of hyperglycemia in the postoperative period will improve outcome.

Aged↗
PubMed2004

Anterior leaflet augmentation for ischemic mitral regurgitation.

BACKGROUND: Mitral valve repair improves survival and quality of life in patients with ischemic mitral regurgitation (MR). Although many repair methods exist for this condition, the ideal approach remains unknown. The purpose of this study is to describe a simple technique for repair of ischemic MR that addresses the pathophysiology of tethered leaflets and to report its early results. METHODS: The technique consists of pericardial patch enlargement of the anterior mitral leaflet and placement of a flexible annuloplasty band. Candidates for the repair had ischemic cardiomyopathy and echocardiographic evidence of moderate or severe Carpentier type IIIb MR. Patients were followed with serial echocardiography. RESULTS: Between January 2002 and November 2003, 25 adult patients underwent anterior leaflet augmentation for ischemic MR. Mean age was 64.8 +/- 10.6 years, and mean left ventricular ejection fraction was 0.36 +/- 0.14. Preoperative MR by transesophageal echocardiography was severe in 84% of patients and moderate in 16%. Annuloplasty band sizes were 27 mm to 31 mm (mean, 28.4 +/- 1.1 mm). Concomitant coronary artery bypass grafting was performed in all patients. Transesophageal echocardiography immediately after repair revealed MR to be none or trace in 80% of patients and mild in 20%. No intraoperative conversion to valve replacement was performed. In follow-up, 2 patients have experienced moderate MR and are being treated medically, and no patients have mitral stenosis. At 2 years, actuarial freedom from moderate or greater MR is 81%. CONCLUSIONS: For patients with ischemic MR, anterior leaflet augmentation is a simple and reproducible method of valve repair that addresses the pathophysiology of tethered leaflets. Early results in a small number of patients have been encouraging.

Adult↗
PubMed2004

St. Jude Medical Toronto biologic aortic root prosthesis: early FDA phase II IDE study results.

BACKGROUND: Several biological aortic root replacement techniques have distinct advantages over mechanical composite root replacement including better valvular hemodynamic characteristics and the lack of need for anticoagulation. Current biological root replacement options lack proven long-term durability or are limited by technical or practical concerns. We report the early results from a phase II multicenter clinical trial of the porcine St. Jude Toronto Bioprosthesis with BiLinx (Toronto root). METHODS: 176 Toronto roots were implanted as total aortic root replacement from August 2001 through August 2003. Concomitant cardiac procedures including coronary artery bypass grafting (31%) and ascending aortic replacement (55%) were performed in 74%. Patients were followed clinically and were examined with an echocardiogram at discharge, 6 months, 12 months, and yearly thereafter. Root sizes implanted included 29 mm in 38%, 27 mm in 30%, 25 mm in 20%, 23 mm in 10%, and 21 mm in 2.2%. RESULTS: There are 205 patient years of follow-up through October 2003. Operative mortality was 3.9% (none were valve related) and late mortality was 4%. Operative stroke rate was 1.1% and late stroke rate was 0.6%. Endocarditis developed in 1 patient. Freedom from aortic regurgitation is to date 100% at discharge, 6 months, and 1 year postimplant. Reoperation of the aortic valve/root was not required in any patient. Six-month mean transvalvular gradients for 21-29 mm valves were 12.8, 8.8, 5.3, 4.9, and 4.7 mm Hg, respectively. CONCLUSIONS: Aortic root replacement with the Toronto root is safe and provides superb transvalvular hemodynamics with freedom from anticoagulation. The Toronto root seems widely applicable for all types of aortic root pathology and these early data offer very encouraging results. Long-term follow-up is required.

Adult↗
PubMed2004

Risk factors for cardiac surgery: the high-risk patient.

The demographics of cardiac surgical patients are changing. The average age at operation has risen 10 years since 1980, and the risk of surgery related to severe atherosclerosis of the aorta and its branches is increasing. Although cardiac risk is increasing, operative techniques to minimize cardiac risk have placed the emphasis on comorbid conditions. Patients with preexisting unstable cerebral, vascular, renal, and hepatic disease are at a markedly increased risk and should be carefully evaluated preoperatively.

Acute Kidney Injury↗
PubMed2004

Initial experience with the Toronto Root bioprosthesis.

BACKGROUND AND AIM OF THE STUDY: The study aim was to assess the safety and efficacy of the Toronto Root bioprosthesis for aortic root or valve replacement during the early postoperative stages. METHODS: Between November 2000 and December 2002, the Toronto Root was implanted in 191 patients in 17 institutions. The patients' mean age was 65 years (range: 25 to 87 years) and 70% were males. The bioprosthesis was implanted as a full aortic root in 76% of patients, as a root inclusion in 9%, and in the subcoronary position in 15%. The sizes used in decreasing frequency were 27, 29, 25, 23 and 21 mm. Coronary artery bypass was performed in 25% of patients. Echocardiography was performed before hospital discharge and at six months postoperatively. Serum aluminum levels were monitored pre- and postoperatively as this metal is used in anticalcification treatment of the arterial wall of the porcine root. For the purpose of this study, follow up was closed at six months in all patients, and was complete. RESULTS: Eight patients died, though none of the deaths was valve-related. Two patients required reoperation because of technical errors during implantation. Two patients developed endocarditis, one patient required surgical intervention, and two patients suffered cerebral transient ischemic attacks. All survivors experienced symptomatic improvement, and 97% were in NYHA functional classes I and II at six months postoperatively. Blood levels of aluminum were unchanged at follow up. The mean effective orifice area of all valves studied was 2.0 +/- 0.8 cm2, and the mean systolic gradient 7.0 +/- 3.9 mmHg at six months postoperatively. No patient had more than trace aortic insufficiency. CONCLUSION: Early experience with the Toronto Root bioprosthesis has shown it to be a safe and effective valve for aortic valve or aortic root replacement, with excellent hemodynamic characteristics, a low transvalvular gradient and a large effective orifice area.

Adult↗
PubMed2002

Results of valve replacement with Omniscience mechanical prostheses.

BACKGROUND: The Omniscience mechanical valve has been the subject of multiple clinical investigations with variable results, including reports of high complication and reoperation rates. METHODS: Records of all patients who received Omniscience valves were reviewed, and follow-up interviews were conducted to determine the incidence of valve-related morbidity, mortality, and functional results. Incidence of complications was expressed as events per 100 patient-years follow-up. Survival and freedom from valve-related complications and mortality were calculated using a product limit method. RESULTS: Between 1984 and 1988, 192 patients received 213 Omniscience valves [93 mitral (M), 79 aortic (A), and 20 multiple (D) valve replacements]. Perioperative mortality was 9%. The incidence of major valve-related morbidity was as follows: thrombosis, 1.30 M, 0.17 A, 0.72 D; endocarditis, 0.48 M, 0.18 A, 0 D; hemorrhagic, 4.67 M, 2.84 A, 5.00 D; embolic, 2.90 M, 2.27 A, 1.57 D; nonstructural dysfunction, 1.66 M, 1.08 A, 2.27 D; reoperation, 4.02 M, 1.99 A, 6.48 D. All explanted valves (n = 43) were examined, and 40% (n = 17) were found to have limited disc excursion in the absence of thrombus. Freedom from valve-related morbidity, mortality, or reoperation at 10 years was 22% for mitral, 39% for aortic, and 17% for multivalve replacements. At follow-up, only 73% of patients were New York Heart Association class I or II. Five- and 10-year estimated survivals were 72% and 55% for M, 80% and 51% for A, and 65% and 50% for D replacements. CONCLUSIONS: Use of the Omniscience valve provided poor functional improvement and a significant incidence of valve-related complications, including the need for reoperation.

Adolescent↗
PubMed2002

Rapid disappearance of protamine in adults undergoing cardiac operation with cardiopulmonary bypass.

BACKGROUND: Despite long use of protamine in cardiac operations, neither protamine concentrations nor pharmacokinetics have been reported in patients. METHODS: Twenty-eight patients (age, 26 to 80 years) undergoing various cardiac surgical procedures gave their consent to receive 250 mg of protamine sulfate administered intravenously by an infusion pump during 5 minutes. Protamine was administered at the usual intraoperative time after separation from cardiopulmonary bypass for reversal of heparin. Timed arterial blood samples were obtained after protamine infusion. Blood plasma was subjected to solid-phase extraction and high-performance liquid chromatography. Total (free + heparin-bound) protamine concentration versus time data were subjected to pharmacokinetic modeling. RESULTS: Twenty-six patients completed the study. Total plasma protamine concentrations declined rapidly. Model-independent pharmacokinetic analysis revealed median (range) values as follows: volume of distribution, 5.4 L (0.82 to 34 L); clearance, 1.4 L/min (0.61 to 3.8 L/min); and half-life, 4.5 min (1.9 to 18 min). Schwarz-Bayesian criterion identified a two-compartment exponential model with adjustment for weight in the central compartment volume of distribution as performing better than other compartmental or Michaelis-Menten models. CONCLUSIONS: Protamine has a very short (approximately 5 minutes) half-life after a single 250-mg dose in adult patients. This short half-life could underlie recurrent anticoagulation after initial apparent reversal of heparin.

Aged↗
PubMed2002

Intraoperative insulin therapy does not reduce the need for inotropic or antiarrhythmic therapy after cardiopulmonary bypass.

OBJECTIVE: To determine whether attempted glucose control through intraoperative insulin therapy reduces the need for inotropic or antiarrhythmic therapy after cardiopulmonary bypass (CPB). DESIGN: Post hoc analysis of a randomized, masked clinical trial of insulin therapy for prevention of neurobehavioral deficits. SETTING: Single university hospital. PARTICIPANTS: Nondiabetic patients undergoing elective coronary artery bypass graft surgery (n = 381). INTERVENTIONS: Patients received either insulin infusions in an attempt to maintain blood glucose at 80 to 120 mg/dL (n = 188) or placebo (saline; n = 193). Inotropic therapy was defined as the initiation of vasoactive support with epinephrine or amrinone infusions or mechanical support with the initiation of an intra-aortic balloon pump in the operating room or within 12 hours postoperatively. Antiarrhythmic therapy was defined as cardioversion, antiarrhythmic medications, or pacing. MEASUREMENTS AND MAIN RESULTS: Of patients, 64 in the placebo group and 71 in the insulin group required inotropic support after CPB (p = not significant). The use of cardioversion (55 in placebo group v 61 in insulin group), antiarrhythmic medications (64 in placebo group v 76 in insulin group), and pacing (118 in placebo group v 117 in insulin group) was similar between groups. Inotropic drug support was associated with age >60 years, female gender, reduced preoperative ejection fraction, history of angina, and increased duration of CPB. CONCLUSION: Intraoperative insulin therapy did not reduce the use of inotropic or antiarrhythmic support after cardiac surgery with CPB. The lack of benefit may be due to the inability to prevent hyperglycemia during the physiologic stress of CPB or a tribute to the effectiveness of modern myocardial preservation techniques.

Aged↗