Predicting surgical outcome using Bayesian analysis.

Surgical outcome analysis is best performed using Bayesian statistics. The ability of this type of analysis to take into consideration multiple parameters affecting surgical outcome is a marked improvement over single-condition probabilities that ignore the many degrees of freedom in the dynamics of a surgical intervention. To illustrate the power of a Bayesian analysis a surgical population of 1017 patients undergoing cholecystectomy, colon resection, and appendectomy was developed. Each patient was assigned to a mutually exclusive outcome group (D1, survival; D2, survival with complications; D3, nonsurvival). A priori outcome probabilities for the population were D1 = 0.917, D2 = 0.066, and D3 = 0.017. A conditional probability matrix (CPM) was then developed for 59 patient parameters (Sj) that may have affected outcome. The CPM contained the conditional probability that a parameter was present given the known outcome P(Sj/Di). Once the CPM was matured Bayesian analysis allowed one to predict the surgical outcome given any set or combination of patient parameters P(Di/Sj). Posterior probabilities generated by the Bayes analysis allowed one to investigate the effect of a single parameter or any group of parameters on outcome. Criterion based validity testing based on comparison of Bayesian outcomes versus the surgeons perception of outcomes for computer simulated surgery on 15 artificial patients suggests that this type of analysis provides insightful and educational data to the operating surgeons (V-mortality = 0.547, SEE = 24.46; V-morbidity = 0.319, SEE = 25.86). Objective outcome analysis or surgical peer review cannot be fairly accomplished unless the statistical methodology takes into consideration all of the parameters affecting outcome. This study concludes that Bayes Theorem provides the ideal statistical framework for performing an outcome analysis that considers the many parameters affecting the results of a surgical intervention.

Pyruvate improves myocardial tolerance to reperfusion injury by acting as an antioxidant: a chemiluminescence study.

BACKGROUND: There is indirect evidence that pyruvate improves myocardial tolerance to ischemia by scavenging oxygen radicals during reperfusion. The objectives of this study were to evaluate (1) lucigenin-enhanced chemiluminescence (LEC) as a method to measure oxygen radical (OR) production in vitro and in vivo and (2) the antioxidant effect of pyruvate during myocardial reperfusion. METHODS: LEC was measured in vitro by adding to lucigenin (1) increasing concentrations of H2O2, (2) H2O2 and different concentrations of catalase, and (3) H2O2 plus pyruvate. Isolated rat hearts perfused with Krebs Henseleit-Lucigenin inside a chemiluminescence chamber were subjected to equilibration, ischemia, and reperfusion without (control) or with pyruvate. Developed pressure, contractility, compliance, and chemiluminescence were recorded. RESULTS: In vitro, LEC directly correlated with H2O2 concentrations (r2 = 0.997) and decreased in the presence of catalase or pyruvate. During myocardial reperfusion there was a surge of chemiluminescence that peaked at 4 minutes. Pyruvate decreased the initial reperfusion peak (9.8 +/- 0.3 x 10(3) cpm in pyruvate group vs 12.4 +/- 0.9 x 10(3) cpm in control; p < 0.05) and the total amount of chemiluminescence generated during reperfusion (65.7 +/- 12 x 10(3) in pyruvate group vs 117.1 +/- 8.2 x 10(3) counts in control; p < 0.05). Pyruvate improved recovery of function after ischemia reperfusion. CONCLUSIONS: LEC is a sensitive indicator of H2O2 concentrations and can evaluate the effect of antioxidants in vitro. It is a continuous, sensitive, and direct measurement of OR production in vivo. LEC is ideal for the evaluation of antioxidant interventions and provides direct evidence that pyruvate acts as an antioxidant while improving myocardial function during reperfusion.

Ischemic preconditioning decreases oxidative stress during reperfusion: a chemiluminescence study.

The mechanism responsible for ischemic preconditioning (IPC) is still unknown but may involve the induction of antioxidant enzymes decreasing oxidative stress during subsequent periods of ischemia (I) and reperfusion (RP). The purpose of this study was to determine whether, in fact, an antioxidant mechanism is involved in the protection afforded by IPC. Lucigenin-enhanced chemiluminescence (LEC), a direct, continuous, nondestructive, on-line method was used to monitor the net amount of free oxygen radicals (FOR) produced during perfusion of rat hearts. Isolated rat hearts were perfused inside a chemiluminescence chamber with lucigenin (1 x 10(-5) M) and subjected to either: (a) 80 min of equilibration (EQ80 group, n = 6), (b) 15 min of EQ, 2 min of IPC, 10 min of reequilibration (REQ), 25 min of I, and 28 min of RP (IPC group, n = 8), or (c) 27 min of EQ, 25 min of I, and 28 min of RP (CTRL, n = 7). Chemiluminescence was measured as counts per minute (cpm) and expressed as %EQ15 (mean +/- SEM). Paired and nonpaired t tests were used for statistical evaluation. EQ80 showed no changes in oxidative stress throughout perfusion (4.5 +/- 0.2 x 10(3) cpm at EQ15 vs 5.1 +/- 0.5 x 10(3) cpm at EQ80, P = NS). During REQ (after IPC) there was a surge of chemiluminescence in IPC hearts compared with CTRL (130 +/- 8% vs 108 +/- 4%, P < 0.05). During reperfusion there was a surge of chemiluminescence in CTRL hearts that was diminished in the IPC hearts (550 +/- 50% vs 380 +/- 50% in IPC, P < 0.05). We conclude that: (1) IPC induces an oxidative stress generating FOR during REQ, (2) IPC decreases the initial FOR burst during RP. We speculate that IPC increases cellular antioxidant defenses which result in decreased oxidative stress during early RP.

Coenzyme Q10 protects coronary endothelial function from ischemia reperfusion injury via an antioxidant effect.

BACKGROUND: Cardiac ischemia reperfusion (I/R) injury causes coronary vascular dysfunction. Coenzyme Q10 (CoQ), which preserves cardiac mechanical function after I/R, recently has been recognized as a free radical scavenger. We hypothesized that CoQ protects coronary vascular reactivity after I/R via an antioxidant mechanism. METHODS: Rats were pretreated with either CoQ (20 mg/kg intramuscular and 10 mg/kg intraperitoneal [CoQ group]) or a vehicle (Control) before the experiment. Isolated perfused rat hearts were subjected to 25 minutes of global normothermic ischemia and 40 minutes of reperfusion. The reperfusion-induced oxidative burst was directly assessed by lucigenin enhanced chemiluminescence. Coronary flow was measured at equilibration and after reperfusion with or without bradykinin, an endothelium-dependent vasodilator, and sodium nitroprusside (SNP), an endothelium-independent vasodilator. The effect of intracoronary infusion of hydrogen peroxide (H2O2 0.1 mumol/gm body weight given over 5 minutes), simulating the free radical burst after I/R, also was evaluated. RESULTS: I/R decreased the bradykinin-induced change in coronary flow (-5% +/- 4% versus 26% +/- 3% at equilibration; p < 0.05) and the SNP-induced change (+20% +/- 6% versus +56% +/- 5% at equilibration; p < 0.05). The coronary vasculature after H2O2 infusion revealed a similar loss in vasodilatory responsiveness (+4% +/- 4% in response to bradykinin, +35% +/- 8% in response to SNP; p < 0.05 versus equilibration). Pretreatment with CoQ improved BK-induced vasorelaxation after I/R (+12% +/- 2%; p < 0.05 versus control I/R) or H2O2 infusion (18% +/- 4%; p < 0.05 versus control I/R) but failed to improve SNP-induced vasorelaxation. The CoQ pretreatment decreased the I/R-induced maximal free radical burst (9.3 +/- 0.8 x 10(3) cpm versus 11.5 +/- 1.1 x 10(3) cpm; p < 0.05) during the early period of reperfusion. CONCLUSIONS: Endothelium-dependent vasorelaxation is more sensitive than endothelium-independent relaxation to I/R injury. Via a direct antioxidant effect, CoQ preserved endothelium-dependent vasorelaxation by improving tolerance to I/R injury.

The mean performance regression, a method of objective surgical peer review.

Outcome data were studied for 1,078 surgical cases over a six-month period. A method of presentation of that data, the mean performance regression, is presented. Mean performance regression is a powerful tool in stimulating discussion about surgical performance.

Management of acute postoperative thrombosis following carotid endarterectomy.

We reviewed 326 carotid endarterectomies performed from 1960 through 1981 and encountered five instances of acute postoperative thrombosis. Clinical decompensation occurs with the acute onset of severe neurologic deficits, most characteristically dense hemiplegias contralateral to the side that has been operated on. These deficits developed between two and 72 hours postoperatively. Prompt reoperation with thrombectomy and reestablishment of carotid flow within two hours from the onset of the neurologic deficit was performed on four patients with complete resolution of the deficits in three patients. The fourth patient recovered from a severe hemiplegia but retained a slight residual weakness of the hand. The one patient whose condition did not improve underwent thrombectomy more than 24 hours after the onset of her deficit. Time-consuming diagnostic procedures are not warranted as the success of reoperation depends on rapid reestablishment of cerebral flow.

Leiomyosarcoma of the abdominal aorta: a case report.

A case report of a leiomyosarcoma of the abdominal aorta is presented. The patient was referred to our institution because of symptoms of an acute occlusion of the infrarenal aorta. En bloc resection of the tumor and reconstruction of distal arterial flow were performed.

A study of anastomotic aneurysms following aortofemoral prosthetic bypass.

Between 1960--1979, 19 patients with aortofemoral prosthetic bypass for aneurysmal and/or occlusive disease subsequently developed 36 false aneurysms at the suture line, for an incidence of 4.5% (19/426 patients). The two major aneurysm sites were the femoral anastomosis 4.5% (33/727) patients), and the aortic anastomosis 0.7% (3/430 patients). Additionally, one patient with bilateral false aneurysms of the groin subsequently developed an aortoduodenal fistula. The initial operation was for aortoiliac occlusive disease in 14 and for abdominal aortic aneurysms plus severe occlusive disease in five. The false aneurysm(s) appeared three months to 17 years after the aortofemoral procedure. Eleven of 19 patients (57.9%) had multiple aneurysms (two to five) and developed both right and left groin aneurysms concomitantly or at different times. Suture failure was the major finding at operation. However, a common alternative finding was partial or near complete separation of the prosthesis from the host vessel and an intact suture line, thus indicating a structural weakness in the host vessel and/or severe mechanical stress, as the causative factor. One experience leads us to favor an aggressive surgical approach to these lesions. All false aneurysms were corrected as they were detected with good surgical results.