Biomedical subjects

R C Nair

Publications and source records attributed to R C Nair.

At least 37 records · Page 2Linked to original sources

PubMed1991

Importance of timing of treadmill predictors for risk stratification after myocardial infarction: a five year follow-up study.

The prognostic value of information derived from clinical characteristics and exercise treadmill tests performed before discharge and repeated at three months was evaluated in 205 consecutive patients followed for five years. Recurrent myocardial infarction, unstable angina and mortality were tabulated. Survival was analyzed by the Kaplan-Meier life-table method and the Cox regression model. The major difference between the predischarge and three month intervals was the failure of exercise-induced ST depression to predict mortality from the predischarge test. However, it was predictive of mortality at three months when 76% survived five years with a positive ischemic response compared to 94% with a negative response (P less than 0.0005). In contrast, resting ST depression of at least 1 mm was associated with a very poor five year survival rate of 58.3% and 50% when assessed at both predischarge and three months (P less than 0.0005 and P less than 0.004, respectively). Selected univariately at the predischarge interval, the following characteristics were ranked in descending order of predictive power for five year mortality by discriminant analysis: history of previous infarction; exercise capacity; and ST depression on resting ECG greater than 1 mm. At three months, the same characteristics were selected. However, recurrent infarction and unstable angina were not predictable at either interval by any clinical or treadmill variable. Characteristics tending to reflect poor exercise capacity are stronger predictors of five year outcome than exercise-induced ischemia. While predischarge exercise testing for ST segment response failed to predict survival, this variable showed improved predictive power with repeat testing at three months.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise Test↗

PubMed1990

Iridium-192 curietherapy for T1 and T2 epidermoid carcinomas of the floor of mouth.

From 1970 to 1986, 117 patients with T1 (47) or T2 (70) epidermoid carcinomas of the floor of the mouth (SCC) were treated by iridium-192 implantation (192 Ir). The dose was prescribed according to the Paris System and varied over those years. Follow-up information was available on 116 patients. There were 46 T1N0, 47 T2N0, and 23 T2N1-3. Neck management varied for the 93 N0 patients consisting of surveillance (24 T1, 17 T2) or elective neck dissection (22 T1:all pN-, 30 T2: 20 pN-, 10 pN+). Cause specific survival rates were 94% for T1N0, 61.5% for T2N0, and 28% for T2N1-3 at 5 years. Primary local control was 93.5%, 74.5%, and 65%, respectively, and 98%, 79%, and 65% after salvage. Patients with gingival extension or a tumor size over 3 cm (T2b) had a local control of 50% (9/18) and 58% (15/26), respectively. Nodal control was 93.5% for Stage I, 85% for Stage II, and 48% for T2N1-3 patients. There was no difference in nodal control with regard to treatment policy for Stage I-II patients. There were few complications including three deaths: two from surgery and one from 192 Ir. Nodal status, tumor size defined as T1, T2a (less than or equal to 3 cm), T2b (greater than 3 cm), and gingival extension were the only independent prognostic factors. The management of T1N0 and T2N0 SCC by 192 Ir to a dose of 65 or 70 Gy, using the Paris System, is recommended for lesions 3 cm or less and without gingival extension.

Adult↗

PubMed1990

A randomized phase II study of cisplatin alone versus cisplatin plus disulfiram.

Preclinical evidence has suggested that disulfiram (DS) and related compounds can decrease the toxicity and enhance the therapeutic index of cisplatin (CP). To study this further, we have performed a prospective randomized study wherein 53 patients with CP-sensitive malignancies were assigned to therapy with CP 100 mg/m2 alone (group I) or CP 100 mg/m2 and oral DS 2,000 mg/m2 (group II). Both groups were comparable with regard to sex distribution, age, performance status, prior chemotherapy, and radiotherapy. Twenty-three patients were not evaluable for response (3 refused follow-up, 18 had less than two courses, one had an early death, and one had excessive toxicity during the first cycle of treatment). Of the 30 evaluable patients (16 in group I, 14 in group II), only one in group II achieved a complete response. There was no statistically significant difference in response rate, time to progression, or median survival between the two groups. Fifty-two patients (98.1%) were evaluable for toxicity. Significant differences in toxicities were observed between the two groups: patients in group I encountered lower [Eastern Cooperative Oncology Group (ECOG) 0-1)] grades of nausea, vomiting, and ototoxicity, and patients in group II experienced higher grades (ECOG 2-3) of toxicity in general. In addition, there was no difference in nephrotoxicity between the two groups, as measured by the change in serum creatine or 24-h urine creatinine clearance over the first course of treatment. We conclude that, contrary to previously published reports, DS does not afford significant nephroprotection against CP and, in fact, enhances gastrointestinal and ototoxicities.

Aged↗

PubMed1989

Complications of plasma exchange.

For the past few years, the Canadian Apheresis Study Group has collected data on most apheresis procedures carried out throughout the country. The information accumulated during calendar year 1985 has been reviewed, and the complications that occurred as a result of therapeutic plasma exchange (PE) have been assessed. There were side effects during 612 (12%) of the 5235 procedures done, involving 252 (40%) of the 627 patients treated. The most common reactions were fever, chills, urticaria, muscle cramps, or paresthesias; these reactions were encountered more frequently when plasma was used in the replacement fluid. Most reactions had little or no clinical significance. However, there were 28 severe complications, including one cardiac arrest and two respiratory arrests. Five late deaths occurred, but these were not related directly to PE. Although PE is relatively safe, life-threatening reactions do occur, and patients require careful observation during the procedure.

Adolescent↗

PubMed1988

Prognostic significance of endometrial extension in carcinoma of the cervix.

A retrospective analysis of 343 consecutive patients with histologically proven carcinoma of the cervix, treated at the Ottawa General Hospital, was undertaken to evaluate the prognostic significance of endometrial extension. All these patient had a D + C as part of their work-up. Sixty-seven patients had a (+) D + C: 34/150 (23%) in Stage IB, 21/106 (20%) in Stage II, and 12/87 (14%) in Stage III. Survival was closely related to the D + C findings in early stages. In Stage IB, the 5-year survival of D + C (-) patients was 90% vs 50% in D + C (+) patients (P less than 0.003) and in Stage II, the 5-year survival was 77% and 55%, respectively (P = 0.089). There was, however, no difference in survival in Stage III patients (35% vs 29%). Pelvic failures were similar in both groups, stage for stage, but those with a (+) D + C had a higher incidence of distant metastasis. In Stage IB, distant metastases were found in 8.5% (10/116) of D + C (-) patients compared to 38% (13/34) in D + C (+) patients (P less than 0.001) and in Stage II, in 18.5% (16/85 and 33% (7/21) of the patients (P = 0.126), respectively. There was no difference in Stage III patients (28% vs 25%). This study suggests that endometrial extension is a significant prognostic factor in early stages and is associated with a higher risk of distant metastases. Management of these high risk patients is discussed.

Dilatation and Curettage↗

PubMed1988

Platinum concentrations in human autopsy tumor samples.

Platinum concentrations were determined in autopsy tumor samples obtained from 27 patients who had received cisplatin 40-1,029 mg/m2 from 0 to 240 days antemortem. Liver metastases had significantly higher platinum concentrations than did tumors in other sites (p less than 0.005). Platinum concentrations in liver metastases were similar to platinum concentrations in normal liver. Platinum concentrations in gliomas and brain metastases were similar to platinum concentrations in other extrahepatic tumors. Platinum concentration generally decreased with increasing distance into brain from tumor. By multiple stepwise linear regression analysis, the factors that were independently most closely associated with tumor platinum concentration were time from last cisplatin treatment, cumulative lifetime dose of cisplatin, route of cisplatin administration (intraarterial vs. other), and site of tumor deposit (liver vs. other) (r = 0.69, p less than 0.001). Patients whose tumors had responded to cisplatin-containing regimens had mean tumor platinum concentrations that were higher than the mean tumor platinum concentrations in patients whose tumors had not responded to cisplatin (p less than 0.05).

Autopsy↗

PubMed1988

Urgent surgical reperfusion in acute evolving myocardial infarction. A randomized controlled study.

To assess the benefit of immediate surgical reperfusion over conventional medical treatment during the first acute evolving transmural myocardial infarction, 68 patients presenting within 4 hours of onset of chest pain were randomized into a medical group and a surgical group. Both groups were comparable for age, sex, coronary risk factors, location of infarct, and coronary anatomy. Radionuclide global ejection fraction at 48 hours after admission was 45 +/- 15% for the medical group versus 50 +/- 15% for the surgical group; at 3 months, ejection fraction values were 51 +/- 13% and 51 +/- 13%, respectively (p = NS). The average radionuclide wall-motion scores (normal, 3) at 3 months were 2 +/- 0.6 for the medical group and 2 +/- 0.7 for the surgical group. There were three (8.8%) early and four (11.7%) late deaths in the medical group and only one (2.9%) early death in the surgical group. Urgent surgical reperfusion in acute evolving myocardial infarction is a safe and effective procedure that appears to reduce early and late mortality but does not appear to improve left ventricular function.

Clinical Trials as Topic↗

PubMed1987

Lung cancer mortality (1950-80) in relation to radon daughter exposure in a cohort of workers at the Eldorado Port Radium uranium mine: possible modification of risk by exposure rate.

A cohort study of 2,103 workers employed between 1942 and 1960 at a uranium mine in the Northwest Territories, Canada, was conducted. A total of 57 lung cancer deaths was observed (expected = 24.73, P less than .0001). There was a highly significant linear relationship between exposure and increased risk of lung cancer, giving estimates for the relative and attributable risk coefficients of 0.27 per working level month (WLM) and 3.10 per WLM per 10(6) person-years. These risk coefficients were substantially less than those estimated from the experience of miners in the Beaverlodge mine, which have previously been reported. Any biases in the present estimates are likely to have been upward, and therefore they probably represent an upper limit. The major difference between the two mine cohorts is in the exposure rate, since the Port Radium miners were exposed to much greater concentrations of radon daughters than the Beaverlodge miners. It is postulated that risk of lung cancer from radon daughter exposure may be modified by exposure rate, for which hypothesis there is some support from other epidemiologic data.

Humans↗

PubMed1987

Do symptoms reflect a change in left ventricular function after aortocoronary bypass grafting in patients with depressed left ventricular function?

Seventy-nine patients with moderate to severe left ventricular dysfunction who underwent aortocoronary bypass grafting between 1971 and 1977 had follow-up heart catheterization at a mean interval of 3 years. Thirty-three patients (42%) had angiographic improvement in left ventricular function at follow-up and 18 (25%) had a decrease in left ventricular end-diastolic pressure. Fifty-eight patients (73%) had improvement in angina of at least one New York Heart Association class at follow-up. There was no correlation between late improvement in left ventricular function and improvement in angina. Improvement in left ventricular function did not correlate with preoperative indices of severity of coronary disease or with indices of completeness of surgical repair.

Adult↗

PubMed1986

Institutional outbreaks of rotavirus diarrhoea: potential role of fomites and environmental surfaces as vehicles for virus transmission.

To assess the potential of fomites and environmental surfaces as vehicles in the transmission of rotaviral diarrhoea, disks (1 cm diameter) of various porous and non-porous materials were contaminated with about 10(5) plaque-forming units of the Wa strain of human rotavirus (HRV) suspended in faecal matter. The contaminated disks were then held for 10 days at either room temperature (22 +/- 2 degrees C) or 4 degrees C with the relative humidity (RH) at the high (85 +/- 5%), medium (50 +/- 5%) or low (25 +/- 5%) level. Survival was longer on non-porous surfaces at the lower temperature and at lower humidity. In contrast, survival on porous surfaces was very variable; better on cotton-polyester than on poster card or paper currency on which HRV survived very poorly. These results suggest that under the right environmental conditions, HRV-contaminated objects could play a role in the transmission of rotavirus infections in hospitals, nursing homes and day-care centres.

Animals↗

PubMed1986

Lung cancer mortality (1950-80) in relation to radon daughter exposure in a cohort of workers at the Eldorado Beaverlodge uranium mine.

A cohort study of 8,487 workers employed between 1948 and 1980 at a uranium mine in Saskatchewan, Canada, has been conducted. A total of 65 lung cancer deaths was observed (34.24 expected, P less than 10(-5)). There was a highly significant linear relationship between dose and increased risk of lung cancer giving estimates for the relative and attributable risk coefficients of 3.28% per working level month (WLM) and 20.8 per WLM per 10(6) person-years. Age at first exposure had a significant modifying effect on risk. The interaction of exposure with age at observation fits a relative risk model well. The similarity of these results to a recent study of Swedish iron miners with similar levels of relatively low exposure suggests that exposure to radon daughter products may be a major contributory factor to lung cancer occurring among nonsmokers in the general population. The results also reinforce concerns as to the appropriateness of present occupational exposure standards.

Age Factors↗

PubMed1985

Survival characteristics of airborne human coronavirus 229E.

The survival of airborne human coronavirus 229E (HCV/229E) was studied under different conditions of temperature (20 +/- 1 degree C and 6 +/- 1 degree C) and low (30 +/- 5%), medium (50 +/- 5%) or high (80 +/- 5%) relative humidities (RH). At 20 +/- 1 degree C, aerosolized HCV/229E was found to survive best at 50% RH with a half-life of 67.33 +/- 8.24 h while at 30% RH the virus half-life was 26.76 +/- 6.21 h. At 50% RH nearly 20% infectious virus was still detectable at 6 days. High RH at 20 +/- 1 degree C, on the other hand, was found to be the least favourable to the survival of aerosolized virus and under these conditions the virus half-life was only about 3 h; no virus could be detected after 24 h in aerosol. At 6 +/- 1 degree C, in either 50% or 30% RH conditions, the survival of HCV/229E was significantly enhanced, with the decay pattern essentially similar to that seen at 20 +/- 1 degree C. At low temperature and high RH (80%), however, the survival pattern was completely reversed, with the HCV/229E half-life increasing to 86.01 +/- 5.28 h, nearly 30 times that found at 20 +/- 1 degree C and high RH. Although optimal survival at 6 degree C still occurred at 50% RH, the pronounced stabilizing effect of low temperature on the survival of HCV/229E at high RH indicates that the role of the environment on the survival of viruses in air may be more complex and significant than previously thought.

Aerosols↗

PubMed1985

Effect of relative humidity, atmospheric temperature, and suspending medium on the airborne survival of human rotavirus.

The Wa strain of human rotavirus, grown in MA-104 cells, was suspended either in tryptose phosphate broth or feces from a case of rotaviral diarrhea. It was then aerosolized into a rotating drum using a Collison nebulizer. The drum air was sampled using an all-glass impinger containing tryptose phosphate broth as collecting fluid. At 20 +/- 1 degree C, the virus aerosolized from tryptose phosphate broth was found to survive best at 50 +/- 5% relative humidity, where its half-life was 44.2 +/- 6.3 h. At 30 +/- 5% and 80 +/- 5% relative humidity, the half-life of the virus was 24.5 +/- 3.5 and 3.8 +/- 1.0 h, respectively. At 6 +/- 1 degree C, the airborne survival of the virus at the mid and low relative humidity levels was further enhanced, but at the high relative humidity it remained very similar to that seen at 20 +/- 1 degree C. When aerosols of fecally suspended human rotavirus were held at 20 +/- 1 degree C with 50 +/- 5% relative humidity, nearly 80% of the airborne virus particles remained infectious even at the aerosol age of 24 h. These findings may help in our understanding of the epidemiology of rotaviral infections.

Aerosols↗

PubMed1985

Renal and hepatic concentrations of platinum: relationship to cisplatin time, dose, and nephrotoxicity.

Autopsy tissues were obtained from 30 patients who had received cisplatin antemortem; the tissues were assayed for platinum by flameless atomic absorption spectrometry. Patients with antemortem evidence of renal toxicity had higher renal cortical platinum concentrations than did patients without evidence of kidney damage. In addition, patients with nephrotoxicity were more likely than patients without toxicity to have renal cortical platinum concentrations that were higher than renal medullary platinum concentrations. Overall, the two variables most closely associated with an increase in serum creatinine with treatment were renal cortical platinum concentration (P less than .02) and cumulative dose of cisplatin (P less than .05). These two variables were important independently of one another. Renal cortex platinum concentrations correlated inversely with time from last treatment until death, whereas hepatic platinum concentrations did not. In contrast, hepatic platinum concentrations correlated with dose of cisplatin while renal platinum concentrations did not. Our results suggest the following: (1) cisplatin-induced renal toxicity is tissue-platinum-concentration dependent and cisplatin-dose dependent; and (2) cisplatin may be handled differently at the molecular level in liver and kidney.

Adult↗

PubMed1984

Comparison of clinical and treadmill variables for the prediction of outcome after myocardial infarction.

To assess the relative prognostic merits of 15 clinical and 10 predischarge exercise test variables, 226 patients who had sustained an acute myocardial infarction were studied. A submaximal treadmill test was performed on 205 patients to a mean work load of 5.7 +/- 2.9 METS. Testing was performed an average of 11.7 (range 6 to 33) days after myocardial infarction. During the first year of observation, major cardiac events were noted in 33 patients (16%), unstable angina in 7 (3.4%), recurrent myocardial infarction in 14 (6.8%) and death in 12 patients (5.9%). Cardiac mortality correlated with mean peak serum creatine kinase (CK) (p less than 0.05), history of previous myocardial infarction (p less than 0.01) and ST segment depression at rest (p less than 0.01). The only exercise variable that correlated with cardiac mortality was poor exercise endurance (p less than 0.05). Multivariate risk stratification of clinical and treadmill variables from these 205 patients using linear discriminant analysis produced a function that correctly classified 95% of those who were event-free and 80% of those who died. The first four discriminant variables that contributed independent information for the prediction of cardiac mortality were: 1) ST segment depression at rest; 2) CK greater than 1,280 IU/liter; 3) exercise duration less than 3 minutes; and 4) a history of previous myocardial infarction. ST segment depression on the predischarge treadmill test did not predict any event, nor did it improve the predictive accuracy of the clinical variables. It is concluded that a history of previous myocardial infarction and ST segment depression on the rest electrocardiogram indicate a poor prognosis after acute myocardial infarction. Poor endurance is the only exercise variable that suggests a future cardiac event. Prognosis after acute myocardial infarction is more accurately predicted by these clinical data than by variables derived from the predischarge treadmill test.

Adult↗

PubMed1984

Magnesium therapy in acute myocardial infarction--a double-blind study.

Various methods have been proposed and tried to limit the extent of myocardial damage at the time of infarction. We chose to assess the usefulness of intravenous magnesium in this regard because of its important role in myocardial metabolism and function and the suggestion of its deficiency in ischemic hearts. A double-blind randomized trial was carried out and results analyzed in 76 patients. At the end of the infusion period the mean serum Mg++ level for the treated group was 3.6 versus 1.9 mg/dl for the control group. The estimated size of infarction (as measured by MB-CK release) was not significantly smaller overall in the treated group (37.4 +/- 4.3 vs. 45.6 +/- 4.6 MB-CK g/Eq), but was significantly smaller in the treated subgroup without heart failure (31.6 +/- 5.8 vs. 44.7 +/- 4.8 MB-CK g/Eq). A trend toward less ventricular ectopy was seen in the group treated with magnesium. There was significantly less lidocaine used for the treatment of ventricular dysrhythmias in this group. Magnesium supplementation in patients undergoing acute coronary events is promising and deserves further study.

Clinical Enzyme Tests↗

PubMed1984

Statistical problems associated with cohort studies of workers in an industry.

Risk factors in a working environment are studied mainly by case control studies or cohort studies of workers in several occupational settings. While the cohort studies are by far more powerful in detecting risk factors there are many problems associated with these studies, apart from the high cost and long duration. Some of these problems include the large number of variables involved, the evaluation of missing observations and the resulting bias, problems in selecting appropriate statistical models and analyses as well as identifying the disease subgroup (including loss to follow up). The problems are considered under four groupings: (1) identifying outcome, (ii) missing data, (iii) estimation of work exposure and (iv) statistical analysis. The apparent advantages of retrospective cohort study should be weighed against these problems when deciding on a study design. More appropriate statistical methods, other than SMR and PMR analysis, should be considered while analysing data from such studies.

Epidemiologic Methods↗

PubMed1983

The time course and characterization of myocardial hemorrhage after coronary reperfusion in the anesthetized dog.

We quantitated hemorrhage associated with reperfusion after varying periods of myocardial ischemia and examined the flow characteristics that accompany reperfusion hemorrhage. Anesthetized dogs were reperfused after 2, 6 or 24 hours of circumflex occlusion. A control group underwent coronary occlusion without reperfusion. Radioactive microspheres were injected before and 5 minutes and 24 hours after reperfusion. The papillary muscles were analyzed for hemoglobin content, flow during myocardial ischemia and flow early and 24 hours after reperfusion. Myocardial creatine kinase activity was assayed to determine the severity of myocardial necrosis in the papillary muscles. Hemorrhage into the posterior papillary muscle was dependent upon the duration of coronary artery occlusion. Posterior papillary hemoglobin averaged 14 mg/g in the 2-hour group, 28 mg/g in the 6-hour group and 36 mg/g in the group reperfused 24 hours after occlusion, compared with 8.7 mg/g in the control group. Myocardial hemorrhage was associated with severe depression in myocardial CK and marked depression in flow to the ischemic area (i.e., collateral flow) during the occlusion. Early reflow averaged 112 ml/min/100 g in the 2-hour group, 61 ml/min/100 g in the 6-hour group and only 5.8 ml/min/100 g in the 24-hour group. Therefore, myocardial hemorrhage induced by reperfusion of the acutely ischemic myocardium is associated with severe ischemia during occlusion and severe myocardial necrosis, but does not depend upon the magnitude of early reflow. Myocardial hemorrhage may occur even though initial reflow values are markedly decreased.

Animals↗