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Biomedical subjects

M F Newman

Publications and source records attributed to M F Newman.

At least 55 records · Page 3Linked to original sources
PubMed1998

Cardiopulmonary bypass time does not affect cerebral blood flow.

BACKGROUND: A time-dependent decline in cerebral blood flow (CBF) has been reported in cardiac surgical patients despite stable pump flows and arterial carbon dioxide tension. Other studies have failed to support these hypothermic cardiopulmonary bypass (CPB) results, showing preservation of CBF during CPB. The purpose of the study was to define the influence of mildly hypothermic CPB duration on CBF. METHODS: Cerebral blood flow was measured using xenon-133 washout and alpha-stat blood gas management during nonpulsatile CPB. Cerebral blood flow measurements were made after the initiation of CPB and near the end of bypass during pump flows of 2.4 L.min-1.m-2. RESULTS: Fifty-two coronary artery bypass patients were studied. The average time between CBF measurements was 54 +/- 20 minutes (mean +/- standard deviation), with a range of 10 to 100 minutes. Temperature and arterial carbon dioxide tension were controlled: after the initiation of CPB, temperature was 35.5 degrees +/- 0.4 degree C and carbon dioxide tension was 37 +/- 2.8 mm Hg; whereas near the end of bypass temperature was 35.6 degrees +/- 0.5 degree C and carbon dioxide tension was 36 +/- 2.3 mm Hg. We found no correlation between CBF and time on CPB (p = 0.47; r = 0.101), in contrast to other studies suggesting that CPB duration may intrinsically affect CBF. CONCLUSIONS: Our experimental results include the following: (1) during mildly hypothermic bypass, CBF does not decrease in relation to time and (2) cerebral flow-metabolism coupling is intact at 35 degrees C.

Blood Pressure↗
PubMed1998

Cerebral emboli and serum S100beta during cardiac operations.

BACKGROUND: The glial protein S100beta has been used to estimate cerebral damage in a number of clinical settings. The purpose of this investigation was to determine the correlation between cerebral microemboli and S100beta levels during cardiac operations. METHODS: Transcranial Doppler ultrasonography was used to measure emboli in the right middle cerebral artery. Emboli counts (n = 111) were divided into five time periods: (1) incision to aortic cannulation; (2) aortic cannulation to cross-clamp onset; (3) cross-clamp onset to cross-clamp release; (4) cross-clamp release to decannulation; and (5) decannulation to chest closure. The level of S100beta (n = 156) was measured at baseline, at the end of cardiopulmonary bypass, then 150 and 270 minutes after cross-clamp release. RESULTS: The level of S100beta correlated with age, cardiopulmonary bypass time, cross-clamp time, and number of emboli at time period 2. Although cardiopulmonary bypass time was univariately associated with S100beta level, it became nonsignificant in a multivariable model that included age and cross-clamp time. CONCLUSIONS: The correlation of S100beta level with emboli measured during cannulation (time period 2) supports the hypothesis that cannulation is a high-risk time period for cerebral injury.

Age Factors↗
PubMed1998

Balance of proinflammatory and antiinflammatory cytokines at thoracic cancer operation.

BACKGROUND: A homeostatic balance of proinflammatory and antiinflammatory cytokines is thought to be important for the maintenance of health. Cytokine baseline levels and response patterns to cardiac and nonmalignant abdominal operations have been investigated. The purpose of this study was to investigate the cytokine patterns at operation for thoracic cancer; the hypothesis tested was that cytokine baseline levels and response patterns would be unique for patients with malignant disease undergoing thoracic operation. METHODS: Ten patients undergoing pulmonary tumor resections were studied. Blood samples were collected at six perioperative time points. RESULTS: The cytokine response of these patients differed from patients undergoing cardiac operations: baseline tumor necrosis factor-alpha (39.1 pg/mL) and interleukin-10 (76.76 pg/mL) were elevated without significant changes. Interleukin-1 receptor antagonist became elevated postoperatively (871.6 pg/mL) compared with baseline (332.8 pg/mL) (p < 0.01). The level of tumor necrosis factor soluble receptor-2 was elevated at baseline (4,823.3 pg/mL) and remained elevated postoperatively (7,293.4 pg/mL) (p < 0.01). CONCLUSIONS: Our hypothesis was supported; a separate pattern of proinflammatory and antiinflammatory cytokine levels and responses to thoracic operation was determined. This pattern may be indicative of tumor burden or detrimental to tumor surveillance; it merits further evaluation.

Aged↗
PubMed1998

Transcranial Doppler blood flow velocity versus 133Xe clearance cerebral blood flow during mild hypothermic cardiopulmonary bypass.

OBJECTIVE: Transcranial doppler (TCD) is used during cardiopulmonary bypass (CPB) to assess cerebral emboli and to estimate cerebral perfusion. We sought to compare TCD middle cerebral artery blood flow velocity (Vmca) to 133Xe clearance cerebral blood flow (CBF) measurements during mild hypothermic CPB thus determining its utility in cerebral perfusion assessment. METHODS: Thirty-four patients undergoing mild hypothermic CPB (35 degrees C) were studied and had comparisons of Vmca and 133Xe CBF at three time intervals, 10, 30 and 60 min after the institution of CPB. Linear regression analysis was performed on data from each of the 3 intervals as well as for pooled data from all 3 periods. RESULTS: The correlation coefficients for the 3 time periods were, r = 0.32 (p = 0.12), r = 0.32 (p = 0.11), r = 0.48 (p = (0.02), respectively. The pooled data correlation had a coefficient of 0.34 (p = 0.003). CONCLUSION: These findings suggest that TCD Vmca is a relatively poor correlate of CBF during mild hypothermic CPB.

Analysis of Variance↗
PubMed1998

Pharmacologic electroencephalographic suppression during cardiopulmonary bypass: a comparison of thiopental and isoflurane.

UNLABELLED: In this study, we examined the cerebral oxygenation effects of two methods of pharmacologic burst suppression during cardiopulmonary bypass (CPB) in valvular heart surgery patients. Patients were randomly entered into one of three groups: control (n = 13, fentanyl and midazolam), control plus burst suppression doses of thiopental (n = 15), or control plus burst suppression doses of isoflurane (n = 16). Burst suppression (80% suppression) was accomplished in the thiopental and isoflurane groups 15 min before aortic cannulation and was maintained through aortic decannulation. Cerebral physiologic measurements were made during hypothermia (27-28 degrees C) and on rewarming to 36 degrees C. During hypothermia, burst suppression produced significant (P < 0.005) differences with regard to cerebral vascular resistance (P = 0.003), cerebral arterial venous oxygen difference [C(a-v)O2] (P = 0.032), cerebral blood flow (CBF) (P = 0.009), and cerebral oxygen delivery (P = 0.027). There was a similar pattern on rewarming, with groups differing significantly (P < 0.05) with respect to CBF (P = 0.016), cerebral vascular resistance (P = 0.008), oxygen delivery (P = 0.004), C(a-v)O2 (P = 0.043), and cerebral oxygen extraction (P = 0.046). Rewarming rates were similar among groups. There was no difference in neurologic outcome or requirement for inotropic support among groups. The time to awakening was increased (P = 0.0005) in the thiopental group. The thiopental group had lower cerebral oxygen delivery, but not lower cerebral metabolic rate of oxygen consumption, compared with the control group, resulting in widening C(a-v)O2 during CPB. This lack of coupling of oxygen delivery and consumption suggests that pharmacologic neuroprotective mechanisms are complex and involve more than an improvement in the ratio of global cerebral oxygen supply to demand. IMPLICATIONS: This study demonstrates that the balance of cerebral oxygen delivery to consumption during cardiopulmonary bypass is altered differently by thiopental and isoflurane. As others have noted, it seems that cerebral protection is more complex than a simple improvement in the balance of oxygen delivery and consumption.

Adult↗
PubMed1997

Cognitive function 5 years after randomization to coronary angioplasty or coronary artery bypass graft surgery.

BACKGROUND: Coronary bypass surgery often leads to short-term cognitive dysfunction, whereas coronary angioplasty does not. Perioperative cognitive dysfunction usually resolves, although a subgroup of surgical patients may continue to exhibit long-term cognitive dysfunction. The purpose of this study was to compare cognitive function 5 years after randomization to a strategy of either initial coronary surgery or initial angioplasty. METHODS AND RESULTS: Five centers in the Bypass Angioplasty Revascularization Investigation participated in this ancillary study. Patients with multivessel coronary disease randomized to angioplasty or surgery were eligible at the time of their 5-year clinic visit. A battery of five measures previously shown to be sensitive to perioperative changes in cognitive function was administered, including the Logical and Figural Memory Scales from the Wechsler Memory Scale, the Digit Symbol and Digit Span subtests from the Wechsler Adult Intelligence Scale, and Part B of the Reitan Trail Making Test. The 125 study patients were generally similar to the 133 patients who were eligible but did not participate, although study participants were significantly younger (P=.003). The 64 patients randomly assigned to angioplasty had baseline characteristics similar to those of 61 patients randomly assigned to surgery. Cognitive function scores were not significantly different between angioplasty or surgery patients in an intention-to-treat analysis (P=.57). There also was no difference in cognitive function scores when the data were analyzed according to whether the patient had ever undergone bypass surgery (P=.59). CONCLUSIONS: Long-term cognitive function is similar after coronary bypass surgery and coronary angioplasty in the majority of patients.

Adult↗
PubMed1997

Relationship of preoperative antiendotoxin core antibodies and adverse outcomes following cardiac surgery.

OBJECTIVE: To test the hypothesis that low serum antiendotoxin core antibody (EndoCAb) level is an independent predictor of adverse outcome following cardiac surgery. DESIGN: Prospective, blinded, cohort study. SETTING: Tertiary care medical center. SUBJECTS: A total of 301 patients undergoing coronary artery bypass graft surgery and/or valvular heart surgery. DESIGN: Preoperative serum was assayed for IgM EndoCAb, IgG EndoCAb, total IgM, and total IgG levels. Known preoperative risk factors were assessed, and patients were assigned a risk score using a validated method. MAIN OUTCOME MEASURE: A major complication, defined as either in-hospital death or postoperative length of stay greater than 10 days. RESULTS: Overall, a major complication occurred in 34 patients (11.3%). Lower IgM EndoCAb level independently predicted (P=.002) increased risk of major complication over and above the effects of preoperative risk score (P=.02), total IgG level (P=.07), and all other known perioperative risk factors. In contrast, IgG Endo-CAb and total IgM concentrations did not predict outcome. No association existed between risk score and level of IgM EndoCAb. CONCLUSION: There is marked preoperative variability in humoral immunity against endotoxin core, which is not accounted for by differences in known preoperative risk factors. In this study, low levels of IgMEndoCAb were an important independent predictor of adverse postoperative outcome, which supports the theory that endotoxemia is a cause of postoperative morbidity.

Aged↗
PubMed1997

Preliminary report of a genetic basis for cognitive decline after cardiac operations. The Neurologic Outcome Research Group of the Duke Heart Center.

BACKGROUND: Changes in memory and cognition frequently follow cardiac operations. We hypothesized that patients with the apolipoprotein E-epsilon 4 allele are genetically predisposed to cognitive dysfunction after cardiac operations. METHODS: The apolipoprotein E-epsilon 4 allele was evaluated as a predictor variable for postoperative cognitive dysfunction in 65 patients undergoing cardiac bypass grafting at Duke University Medical Center. The primary outcome measure was performance on a cognitive battery administered preoperatively and at 6 weeks postoperatively. RESULTS: In a multivariable logistic regression analysis including apolipoprotein E-epsilon 4, preoperative score, age, and years of education, a significant association was found between apolipoprotein E-epsilon 4 and change in cognitive test score in measures of short-term memory at 6 weeks postoperatively. Patients with lower educational levels were more likely to show a decline in cognitive function associated with the apolipoprotein E-epsilon 4 allele. CONCLUSIONS: This study suggests that apolipoprotein E genotype is related to cognitive dysfunction after cardiopulmonary bypass. Cardiac surgical patients may be susceptible to deterioration after physiologic stress as a result of impaired genetically determined neuronal mechanisms of maintenance and repair.

Age Factors↗
PubMed1997

Continuous jugular venous versus nasopharyngeal temperature monitoring during hypothermic cardiopulmonary bypass for cardiac surgery.

STUDY OBJECTIVE: To compare jugular venous to nasopharyngeal temperature during hypothermic cardiopulmonary bypass (CPB). DESIGN: Prospective observational study. SETTING: Tertiary care teaching hospital. PATIENTS: 5 ASA physical status IV patients (40 to 65 years of age) having cardiac surgery with hypothermic CPB. INTERVENTIONS, MEASUREMENTS AND MAIN RESULTS: Jugular venous and nasopharyngeal temperatures were recorded throughout the procedure with comparisons made during four time periods: pre-CPB, during CPB, during rewarming, and post-CPB. The patients underwent 85.8 +/- 45.8 minutes (mean +/- SD) of hypothermic CPB, cooling to 26.3 +/- 7.6 degrees C (nasopharyngeal) followed by rewarming at 0.35 +/- 0.1 degree C (nasopharyngeal)/min. There was a high degree of precision between the two temperature sites, but marked differences in bias. In particular, temperature bias was more pronounced during rewarming from CPB compared with other time periods (p < 0.05) where jugular venous temperature was greater than nasopharyngeal temperature by 3.4 degrees C. CONCLUSION: Nasopharyngeal temperature underestimates jugular venous temperature during rewarming from hypothermic CPB. As a result, the brain may be exposed to periods of hyperthermia, possibly increasing the risk of neurologic injury associated with CPB.

Adult↗
PubMed1997

Feeling the heat.

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Cardiopulmonary Bypass↗
PubMed1997

Effect of temperature during cardiopulmonary bypass on gastric mucosal perfusion.

The purpose of our study was to prospectively study the splanchnic response to hypothermic and tepid cardiopulmonary bypass (CPB) using alphastat management of arterial blood-gas tensions. Twenty-four patients for elective CABG surgery were allocated randomly to tepid (35-36 degrees C) or hypothermic (30 degrees C) bypass groups. Measurements were made at four times: (1) baseline, (2) stable during CPB (inflow temperature = nasopharyngeal temperature) 30 degrees C for hypothermic patients, bypass +20 min for tepid patients, (3) 10 min before the end of bypass, (4) after bypass, skin closure. Both groups demonstrated a significant reduction in gastric intramucosal pH (pHim) from time 1 to time 4 and there was no difference in the incidence of a low pHim between the tepid and cold groups (4/12 vs 3/12; ns) at time 4. pHim was significantly lower in the tepid groups at time 3 (P = 0.03) but this discrepancy may have been because of an artefactually high pHim in the cold group. There was a significantly higher incidence of postoperative non-cardiac complications in patients who had a low pHim at time 4 (P = 0.0008). Therefore, we conclude that although the temperature during CPB had a transient effect on pHim it is unlikely to be a major determinant in the pathogenesis of gut mucosal hypoperfusion after bypass.

Adult↗
PubMed1997

epsilon-Aminocaproic acid plasma levels during cardiopulmonary bypass.

epsilon-Aminocaproic acid (EACA) concentrations achieved during cardiopulmonary bypass (CPB) have not been previously reported. It is unknown whether plasma concentrations reported to inhibit fibrinolysis in vitro (130 microg/mL) are achieved or whether differences in these levels relate to variability in postoperative bleeding. EACA (total intraoperative dose 270 mg/kg) was administered to 27 patients undergoing cardiac reoperation. The plasma EACA concentration was measured by using high-pressure liquid chromatography: 1) 30 min after initiation of drug administration (baseline); 2) 30 min (CPB + 30) after initiation of CPB; 3) 90 min after initiation of CPB. (CPB + 90); and 4) at cardiopulmonary bypass termination (end CPB). Plasma EACA concentrations (microg/mL, min - max, mean +/- SD) were 276-998, 593 +/- 154 at baseline; 147-527, 302 +/- 95 at CPB + 30; 112-500, 314 +/- 100 at CPB + 90; and 84-537, 317 +/- 100 at end CPB. Twenty-four-hour postoperative thoracic drainage and allogeneic red blood cell transfusions were not associated with plasma levels at any time. Although plasma EACA concentrations greater than 130 microg/mL were consistently achieved, we observed a marked variability (more than sixfold) in plasma concentrations and bleeding outcomes despite the use of a weight-based dosing regimen. This variability in drug levels appears to have little relevance to bleeding outcomes, possibly since mean plasma levels exceeded 130 microg/mL during CPB, and nearly all patients (26 of 27) achieved that target level.

Aged↗
PubMed1997

Cost-benefit and efficacy of aprotinin compared with epsilon-aminocaproic acid in patients having repeated cardiac operations: a randomized, blinded clinical trial.

BACKGROUND: Aprotinin and epsilon-aminocaproic acid are routinely used to reduce bleeding during cardiac surgery. The marked difference in average wholesale cost between these two drug therapies (aprotinin, $1,080 vs. epsilon-aminocaproic acid, $11) has generated significant controversy regarding their relative efficacies and costs. METHODS: In a multicenter, randomized, prospective, blinded trial, patients having repeated cardiac surgery received either a high-dose regimen of aprotinin (total dose, 6 x 10(6) kallikrein inactivator units) or epsilon-aminocaproic acid (total dose, 270 mg/kg). RESULTS: Two hundred four patients were studied. Overall (data are median [25th-75th percentiles]), aprotinin-treated patients had less postoperative thoracic drainage (511 ml [383-805 ml] vs. 655 ml [464-1,045 ml]; P = 0.016) and received fewer platelet transfusions (0 [range, 0-1] vs. 1 [range, 0-2]; P = 0.036). The surgical field was more likely to be considered free of bleeding in aprotinin-treated patients (44% vs. 26%; P = 0.012). No differences, however, were seen in allogeneic erythrocyte transfusions or in the time required for chest closure. Overall, direct and indirect bleeding-related costs were greater in aprotinin- than in epsilon-aminocaproic acid-treated patients ($1,813 [$1,476-2,605] vs. $1,088 [range, $511-2,057]; P = 0.0001). This difference in cost per case varied in magnitude among sites but not in direction. CONCLUSIONS: Aprotinin was more effective than epsilon-aminocaproic acid at decreasing bleeding and platelet transfusions. Epsilon-aminocaproic acid, however, was the more cost-effective therapy over a broad range of estimates for bleeding-related costs in patients undergoing repeated cardiac surgery. A cost-benefit analysis using the lower cost of half-dose aprotinin ($540) still resulted in a significant cost advantage using epsilon-aminocaproic therapy (P = 0.022).

Adult↗