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Biomedical subjects

C D Mazer

Publications and source records attributed to C D Mazer.

At least 37 records · Page 2Linked to original sources
PubMed1995

Choice of anaesthetic regimen influences haemodynamic response to cemented arthroplasty.

Haemodynamic changes during bilateral cemented arthroplasty (BCA) were compared in dogs anaesthetized with isoflurane/N2O (ISOF) or diazepam/fentanyl (100 microg x kg(-1))N2O(FENT). Eight animals were anaesthetized with each regimen. After establishing monitoring and recording baseline values, BCA was performed. Haemodynamic measurements included aortic blood pressure (ABP), pulmonary artery pressure (PAP), right and left atrial pressures, and cardiac output. These were recorded at 30, 60, 180 and 300 sec after BCA. Lungs were removed and examined postmortem using quantitative morphometry. Groups demonstrated similar increases in PAP (ISOF 15 +/- 2 to 32 +/- 7, FENT 19 +/- 4 to 38 +/- 13; P> 0.05 between groups, P< 0.05 vs baseline). The proportion of lung vasculature occluded by fat was not different between groups (ISOF 9.63 +/- 3.38%, FENT 8.85 +/- 2.20%). Stroke volume decreased similarly in both groups (P> 0,05 between groups, P< 0.05 vs baseline). However, ABP decreased within one minute of BCA in ISOF (111 +/- 17 to 55 +/- mmHg, P< 0.05 and two of eight dogs died. All FENT dogs survived and hypotension (118 +/- 20 to 102 +/- 24 mmHg) was transient and less severe (P< 0.05 vs ISOF). Increased heart rate (HR) was noted in FENT following BCA (73 +/- 8 to 108 +/- 25 beats x min(-1); P< 0.05). Baseline HR was higher in ISOF (P< 0.05) and no increase in HR was noted. Systemic vascular resistance decreased in ISOF (P< 0.05), but not FENT (P> 0.05 vs baseline, P< 0.05 vs ISOF). To assess the role of slower baseline HR in FENT (73 +/-8) versus ISOF (131 +/- 5), six FENT dogs were paced (130 beats x min(-1)) with epicardial leads and an AV sequential pulse generator to simulate the ISOF group's baseline HR. Haemodynamic stability was maintained in this group in spite of a more rapid baseline HR. The choice of anaesthetic regimen strongly influenced acute haemodynamic changes in response to BCA.

Anesthetics, Inhalation↗
PubMed1995

Cerebral microemboli during coronary artery bypass using different cardioplegia techniques.

Larger numbers of microemboli detected by transcranial Doppler echocardiography have been linked to adverse neuropsychological outcome after coronary artery bypass grafting. Differences in neurologic outcome have been attributed to different cardioplegia techniques. Transcranial Doppler-detected microembolic events were recorded during coronary artery bypass grafting using different cardioplegia techniques. Patients received cold antegrade (n = 20), warm antegrade (n = 17), or warm retrograde (n = 20) cardioplegia. Continuous monitoring was divided into stages: aortic cannulation, initiation of cardiopulmonary bypass, aortic cross-clamping, aortic declamping and decannulation until chest closure. Rate of embolic events and number of total and immediate embolic events were tabulated. Total embolic events ranged from 22 to 2,072 per patient and were similar among groups. The rate and total at each stage were similar. Total embolic events were highest during aortic clamping; the rate was highest at initiation of bypass. The immediate embolic events were higher in the warm retrograde group than both antegrade groups at aortic declamping. In summary, a high total and rate of embolic events were detected and differences between cardioplegia techniques were detected.

Coronary Artery Bypass↗
PubMed1995

Platelet activation in warm and cold heart surgery.

Recent studies suggest that patients undergoing warm heart surgical procedures have reduced postoperative bleeding. To determine if this is due to differences in platelet activation, we measured platelet membrane glycoproteins (GPIb, GPIIb/IIIa, GMP 140), platelet fragments, and platelet counts before, during, and after normothermic (37 degrees C) or hypothermic (28 degrees to 30 degrees C) cardiopulmonary bypass. Cardiopulmonary bypass was associated with a significant decrease in platelet count, platelet membrane GPIb, and platelet fragments, and an increase in GMP 140 (p < 0.05). Normothermic cardiopulmonary bypass induced an early significant increase in granulocytes, whereas this was delayed until after rewarming in the hypothermic group. Mean 24-hour postoperative blood loss was 786 +/- 226 mL in the cold group versus 547 +/- 56 mL in the warm group (p = not significant). We conclude that cardiopulmonary bypass affects platelet activation and integrity and that these changes are similar in direction and magnitude for hypothermic and normothermic techniques.

Aged↗
PubMed1995

Determinants of postoperative hypothermia after normothermic cardiopulmonary bypass.

Inadvertent postoperative hypothermia in the cardiac surgical patient can have various adverse physiologic effects. Previous studies have investigated the relationship of patient, surgical, and anesthetic factors with postoperative hypothermia in patients undergoing noncardiac surgery. This study was designed to assess the relationship between postoperative hypothermia after normothermic cardiopulmonary bypass (CPB) for cardiac surgery and a variety of perioperative and patient factors. Fifty-six patients undergoing daytime elective or urgent cardiac surgery with warm (37 degrees C) CPB were studied. The following patient variables were included: age, weight, height, sex, history of previous cardiac surgery, and prebypass temperature. The following treatment factors were recorded: type of surgery, type and dose of anesthetic, use of airway humidifier, use of an intravenous (i.v.) fluid warmer, total volume of i.v. fluid administered during surgery, net fluid volume administered via CPB, total time spent on CPB, use of nitroglycerin, use of alpha-agonists during surgery, and elapsed time from end of CPB to end of surgery. Core temperature readings, as measured by a pulmonary artery catheter thermistor, were noted as follows: (1) on insertion of the pulmonary artery catheter; (2) after the patient was weaned from CPB; (3) within 30 minutes of intensive care unit (ICU) arrival; (4) 3 to 5 hours after ICU arrival; (5) 7 to 9 hours after ICU arrival; and (6) 11 to 13 hours after ICU arrival. Multiple linear regression and logistic regression for categorical variables with backward elimination were employed to determine the impact of all variables on lowest postoperative temperature. The lowest mean temperature occurred during CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1995

Dichloroacetate stimulates carbohydrate metabolism but does not improve systolic function in ischemic pig heart.

Increased carbohydrate utilization may protect the heart during ischemia and reperfusion. Dichloroacetate (DCA) stimulates pyruvate dehydrogenase, which is the rate-limiting step in oxidation of lactate and pyruvate. The purpose of this study was to determine if the myocardial metabolic changes induced by intracoronary DCA during myocardial ischemia were accompanied by improvement in systolic function. A perfusion circuit was created from the carotid to left anterior descending coronary artery (LAD) in 11 anesthetized Yorkshire swine. Data were obtained under strict hemodynamic control at baseline, after 15 min of moderate (30%) LAD flow reduction, and after an additional 15 min of ischemia with either intracoronary DCA (3 mM, n = 6) or saline (n = 5) infusion. DCA decreased lactate release and increased lactate uptake during ischemia as measured by glucose and lactate carbon-labeled tracers. Despite these metabolic changes, no improvement in systolic shortening, microsphere blood flow, or oxygen consumption occurred. Thus, although DCA stimulated carbohydrate metabolism during myocardial ischemia, it did not directly improve systolic function.

Animals↗
PubMed1994

A predictive index for length of stay in the intensive care unit following cardiac surgery.

OBJECTIVE: To develop a predictive index for length of stay in the intensive care unit (ICU) following cardiac surgery. DESIGN: Univariate and multivariate logistic regression analysis of a cohort of 1404 patients divided into a derivation set of 713 patients and a validation set of 691 patients. SETTING: St. Michael's Hospital, Toronto, a tertiary care cardiovascular centre. PATIENTS: A consecutive sample of all patients undergoing cardiac surgery between Jan. 1 and Dec. 31, 1990 (derivation set), and Jan. 1 and Dec. 31, 1991 (validation set). MAIN OUTCOME MEASURE: A long ICU stay (more than 2 days). Other outcomes analysed were ICU stays over 4, 7 and 10 days, and death. RESULTS: In the derivation set increasing age, female sex, left ventricular function, type of surgery, and urgency of surgery were found to be independent risk factors for a long ICU stay in a multivariate logistic regression analysis. A predictive index was created by assigning risk scores based on the odds ratios of the significant variables in the logistic regression analysis. The predictive index was found to predict lengths of ICU stay greater than 2, 4, 7 and 10 days, and patient death in the validation set. CONCLUSIONS: Length of ICU stay and death following cardiac surgery can be predicted with a multivariate predictive index. The index has potential application as a means of stratifying cardiac surgical risk as well as in optimizing ICU resource planning when resources are limited.

Age Factors↗
PubMed1994

Intracoronary propofol does not decrease myocardial contractile function in the dog.

The intravenous administration of propofol is associated with a considerable decrease in arterial blood pressure. The present study was undertaken to test the hypothesis that myocardial function is not affected by propofol and therefore does not contribute to the hypotensive effect of this anaesthetic agent. Propofol was administered in anaesthetized, open-chest dogs by direct arterial infusion into the left anterior descending coronary artery (LAD). Mean arterial blood pressure, heart rate, left ventricular pressure, dP/dt, regional lactate and oxygen extraction, as well as coronary blood flow were measured. Diastolic function was determined by calculation of the time constant of isovolumetric relaxation from the left ventricular pressure measurement and dP/dt. Contractility was evaluated by measuring regional systolic shortening in an area of the myocardium supplied by the LAD. This was compared with systolic shortening in the distribution of the circumflex (CIRC) artery and with the effects obtained with the intracoronary administration of thiopentone. Intracoronary infusions of propofol and thiopentone did not produce any change in systemic arterial blood pressure, heart rate, or left ventricular end diastolic pressure. Propofol, at a concentration of 5 or 10 micrograms.ml-1 did not decrease systolic shortening in the area perfused by the LAD while thiopentone (40 micrograms.ml-1) reduced systolic shortening by 33% (P < or = 0.05). Neither drug had an effect on systolic shortening in the CIRC area, LAD blood flow or diastolic function. The results of this study suggest that propofol does not have an effect on myocardial contractility. The hypotension associated with the intravascular administration of propofol is more likely due to either a direct vascular or a central effect.

Animals↗
PubMed1994

The CAS Residents' Competition: a 25 year review.

The popularity of the Residents' Competition at the annual meeting of the Canadian Anaesthetists' Society inspired this 25 yr review of the competitors and their presentations. Data were collected from a questionnaire survey of all participants and all current Anaesthesia programme directors, review of the Canadian Anaesthetists' Society records, and a Medline data-base search. Over the 25 yr review period, 226 presentations have been given by 211 different participants, with the annual number of participants ranging from 6 to 13. The majority of participants have been male (85.3% vs 14.2% female, P < 0.001), and the majority of presentations have been clinical in nature (74% vs 26% laboratory, P < 0.01). Over half of all the presentations (53.1%) subsequently were published as scientific papers, and 71.7% of all participants practised anaesthesia in an academic environment at some point in their career. The Residents' Competition appears to have been successful in encouraging scientific excellence in physician's training in anaesthesia in Canada.

Anesthesiology↗
PubMed1994

Stunned myocardium in warm and cold cardiac surgery.

Stunned myocardium is known to occur after cardiac surgery. Although clinical data to date suggest that continuous normothermic blood cardioplegia does not result in more postoperative ventricular dysfunction, its superiority over hypothermic techniques remains controversial.

Animals↗
PubMed1994

Transpulmonary systemic fat embolism. Studies in mongrel dogs after cemented arthroplasty.

We investigated the source of intravascular fat in systemic organs (brain, heart, and kidney) after massive pulmonary fat embolism during cemented arthroplasty. We used a bilateral cemented arthroplasty (BCA) in anesthetized mongrel dogs that simulates a cemented total-hip replacement procedure. We hypothesized that deformable fat globules could pass through the lung vasculature under high pulmonary artery pressure (Ppa). Using quantitative morphometry, we showed that the size of pulmonary vessel occluded by fat decreased from 12.8 +/- 15.2 microns 1 min after BCA to 4.9 +/- 5.1 microns at 120 min after BCA (p < 0.01). Ultrastructural studies demonstrated no evidence of acute inflammation around fat-occluded pulmonary vessels 3 h after BCA. Intravascular fat was found in all brain, heart, and kidney specimens examined 3 h after BCA (n = 6). No anesthetized animal in the "sham" (no BCA) group (n = 3) had intravascular fat at the same time period. Radiolabeled microspheres (15 microns diameter) did not reach the systemic circulation (< 1% nonentrapment) under the high Ppa after BCA. No patent foramen ovale was found in any dog at postmortem examination. We conclude that fat globules can traverse the pulmonary circulation within 3 h of orthopedic surgery. The difference between solid microspheres and fat in transpulmonary passage suggests that the composition, perhaps the deformability, of embolic material influences the lung's filtering capacity.

Animals↗
PubMed1993

Postoperative utilization of critical care services by cardiac surgery: a multicenter study in the Canadian healthcare system.

OBJECTIVES: To describe patterns of critical care services used after cardiac surgery and to evaluate whether variations in the process of care influence outcome. DESIGN: Multicenter, prospective study. SETTING: A convenience sample of four cardiac surgical units: three in university-affiliated (teaching) hospitals and one in a nonteaching regional referral center. PATIENTS: A "consecutive sample" of 335 patients after cardiac surgery in four hospitals. INTERVENTIONS: Data were collected regarding all cardiac surgery patients admitted to the critical care units in the four test hospitals. MEASUREMENTS AND MAIN RESULTS: The critical care unit and hospital lengths of stay and survival were followed. The Therapeutic Intervention Scoring System (TISS) was used to assess the intensive care unit (ICU) interventions used during the first 24 hrs in the ICU and for the final 24 hrs before discharge from the ICU. The severity of illness on admission was assessed using the Acute Physiology and Chronic Health Evaluation (APACHE) scoring system. For patients having similar procedures (e.g., aortocoronary bypass and nonaortocoronary bypass procedures) and with similar outcome (mortality/total hospital length of stay), we found significant differences in the pattern of ICU resource utilization among hospitals. Significant (p < .05) differences in unit length of stay were related to varying factors in different hospitals. In hospital unit A, the type of procedure and preoperative chronic health status influenced unit length of stay (aortocoronary bypass 2.8 +/- 1.7 days; nonaortocoronary bypass 8.7 +/- 8.9 days) because length of stay was different for differing procedure groups. In hospital unit B, the critical care management system and lack of step-down (intermediate care) unit availability resulted in an increased unit length of stay for aortocoronary bypass patients (5.1 +/- 4.5 days) as compared with the other units (mean ICU lengths of stay of 2.8, 2.3, and 3.0 days, respectively). Unit B kept patients for monitoring purposes and had a reduced need for critical care nursing on the day of discharge (TISS = 7.5 +/- 5.5) as compared with the other units (mean TISS scores of 27.4, 23.2, and 21.5). CONCLUSIONS: Significant differences exist among hospitals in the same healthcare system in the utilization of critical care services for cardiac surgery. In spite of these differences, for similar patient "input," the outcome (mortality and hospital lengths of stay) appeared similar. Assessments of utilization of critical care must focus on more detailed specific issues than unit length of stay, and must include factors such as availability of intermediate care areas, the unit management system, chronic health status, and the operative procedures performed, if a utilization management process is to effect improved resource use in critical care.

Canada↗
PubMed1993

Calcium and stunned myocardium.

Calcium administration during ischemia or at the onset of reperfusion is generally considered to be deleterious because cytosolic calcium is elevated at this time. In contrast, the administration of calcium antagonists before or during ischemia is protective. While calcium antagonists may not be beneficial when given after reperfusion, calcium administration during this period has been found to enhance the recovery of systolic and diastolic function of stunned myocardium.

Animals↗
PubMed1993

Closure of an intermediate care unit. Impact on critical care utilization.

We studied the effect of closing a six-bed intermediate care area (ICA) on utilization of a multidisciplinary critical care unit (CCU). Data were collected on all admissions to the 7-bed CCU for 9 months prior to ICA closure (n = 217) and compared with 9 months after CCU expansion (7 to 9 beds) and ICA closure (n = 407). Nonemergency CCU admissions increased from 41 to 112 after ICA closure (p < 0.03). Mean APACHE II score within 24 h of admission decreased from 21.9 +/- 7.4 to 18.6 +/- 7.4 (p < 0.0001). The proportion of patients with APACHE II score < 15, increased from 30/217 to 136/407 accounting for an increase from 5.4 percent to 12.7 percent of CCU days (p < 0.0001). Nursing workload at the time of discharge from CCU decreased (p < 0.0001). The ICA closure altered CCU admission and discharge decision-making. "Low-risk" admissions increased and patients remained in the CCU until they required less nursing care. One factor determining utilization of a CCU is the facilities available outside the unit. A CCU management system is especially important when a wide range of illness severity is present.

Female↗
PubMed1992

Effect of warm heart surgery on perioperative management of patients undergoing urgent cardiac surgery.

The anesthetic management and outcome data were examined in a retrospective case-controlled study that compared a conventional hypothermic cardioplegic technique with the recently described method of warm heart surgery, in patients undergoing urgent cardiac surgery. Hypothermic continuous oxygenated blood crystalloid cardioplegia with systemic hypothermia was used for 37 patients who underwent cardiac surgery by the same surgeon over a 16-month period from July 1986 (group 1), whereas normothermic continuous oxygenated blood crystalloid cardioplegia with systemic normothermia was used on 56 patients over the following 16-month period until March 1990 (group 2). The groups were similar in terms of age, sex, ASA status, NYHA classification, and preoperative left ventricular function. Defibrillation following cardiopulmonary bypass was required in only 3.6% of the warm heart surgery patients (group 2) compared with 83.8% in group 1 (P less than 0.0001), and use of warm heart surgery (group 2) eliminated the need for rewarming. There was a trend towards a reduced incidence of myocardial infarction (19% in group 1 vs 9% in group 2), low cardiac output syndrome (40% vs 29%), and use of the intraaortic balloon pump (16% vs 9%) in warm heart surgery patients, but these differences did not reach statistical significance. There were no differences between the two groups in terms of anesthetic drug usage, total heparin or protamine doses, blood loss, transfusion requirements, or duration of ICU stay.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗