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Biomedical subjects

B Bharadwaj

Publications and source records attributed to B Bharadwaj.

At least 19 recordsLinked to original sources
PubMed1998

Pulmonary vagal innervation is required to establish adequate alveolar ventilation in the newborn lamb.

To investigate the effects of bilateral intrathoracic vagotomy on the establishment of continuous breathing and effective gas exchange at birth, we studied 8 chronically instrumented, unanesthetized, sham-operated and 14 vagotomized newborn lambs after a spontaneous, unassisted vaginal delivery. Fetal lambs were instrumented in utero to record sleep states, diaphragmatic electromyogram, blood pressure, arterial pH, and blood-gas tensions. Six of eight sham-operated lambs established effective gas exchange within 10 min of birth, whereas 12 of 14 vagotomized animals developed respiratory acidosis and hypoxemia (P = 0.008). Breathing frequency in vagotomized newborns was significantly lower during the entire postnatal period compared with sham-operated newborns. Vagotomized subjects also remained hypothermic during the entire postnatal period (P < 0.05). Bronchoalveolar lavage indicated an increased minimum surface tension, whereas lung histology showed perivascular edema and partial atelectasis in the vagotomized group. We conclude that stimulation of breathing and effective gas exchange are critically dependent on intact vagal nerves during the transition from fetal to neonatal life.

Animals↗
PubMed1997

Somatosensory evoked potential monitoring during cardiac surgery: an examination of brachial plexus dysfunction.

OBJECTIVE: To observe the effects of the Favoloro and sternal retractors on the ulnar and median nerve somatosensory evoked potentials (SSEPs) and to identify any relationship with postoperative brachial plexus injury. DESIGN: Prospective study. SETTING: University hospital. PARTICIPANTS: Twenty cardiac patients. INTERVENTIONS: SSEPs were studied in patients undergoing cardiac surgery using normothermic cardiopulmonary bypass. Evoked potentials were obtained from bilateral median and ulnar nerves. MEASUREMENTS: The incidence of nerve-specific SSEP changes and their temporal relationship to retractor usage were determined. The overall incidence of SSEP changes was 75%. There were no differences (p > 0.05) between the group showing changes (n = 15) and the group with no changes (n = 5) with respect to age, body surface area, weight, cross-clamp or cardiopulmonary bypass times. There also were no differences (p > 0.05) between the frequencies of left- and right-sided changes, or in nerve-specific SSEP changes. Seventy-four percent of SSEP changes correlated with retractor usage. No SSEP changes were associated with the Favoloro retractor. Significant SSEP depression, assessed by either percentage reduction in amplitude or persistent amplitude reduction, occurred in the absence of postoperative neurological deficits. There were no detected postoperative brachial plexus injuries. CONCLUSIONS: SSEP changes correlate with the use of the sternal retractor but not the Favoloro retractor. It was not possible to replicate the results of previous investigators in predicting postoperative neurological deficits based on the SSEP changes, and therefore the routine application of SSEP as a monitor cannot be recommended on the basis on these data.

Aged↗
PubMed1996

Oxidative stress as a mechanism of cardiac failure in chronic volume overload in canine model.

We investigated the effects of chronic volume overload in the absence or presence of vitamin E supplements on the cardiac function and contractility, cardiac malondialdehyde (MDA)--a lipid peroxidation product--cardiac antioxidant enzyme activity and antioxidant reserve in canine model. The dogs were divided into three groups of seven dogs each: group I, control; group II, mitral regurgitation (MR) of 4 months duration; and group III, MR of 4 months duration receiving vitamin E (40 U/kg/daily) orally. MR was created by detaching two or more chordae tendinae to raise left atrial pressure to 2.5 to three times normal. MR produced a decrease in the index of myocardial contractility with little change in myocardial function. Decrease in myocardial (left and right ventricles) contractility was associated with an increase in cardiac MDA, and a decrease in cardiac antioxidant reserve and antioxidant enzyme activity. Prevention of volume overload-induced decrease in myocardial contractility by vitamin E was associated with a decrease in cardiac MDA and an increase in cardiac antioxidant reserve and glutathione peroxidase activity towards control levels. Superoxide dismutase and catalase activity remained depressed in vitamin E-treated group. The results indicate that chronic volume overload decreases the contractility of both right and left ventricles and is associated with oxidative stress in both ventricles. These results support the hypothesis that oxygen free radicals are involved in the chronic volume overload-induced cardiac depression.

Animals↗
PubMed1996

Superoxide dismutase and catalase in protection of cardiopulmonary bypass-induced cardiac dysfunction and cellular injury.

BACKGROUND: Cardiac dysfunction following cardiopulmonary bypass (CPB) is well known. Various possible sources for increased levels of oxygen free radicals (OFRs) exist during CPB and OFRs depress cardiac function. Postpump (following CPB) cardiac dysfunction may be due to increased levels of OFRs. METHODS: This study investigated the effects of cold crystalloid cardioplegia with and without superoxide dismutase (SOD) and catalase (CAT) on cardiac function (cardiac index [CI], left ventricular work index [LVWI]), cardiac contractility (+dp/dt, +dp/dt/PAW [pulmonary arterial wedge pressure], +dp/dt/LVEDP [left ventricular end-diastolic pressure]), diastolic compliance (-dp/dt), OFR-producing activity of polymorphonuclear leukocytes (PMNL-CL); creatine kinase (CK) and MB isoenzyme of CK (MBCK), malondialdehyde (MDA), and white blood cells (WBC) and PMNLs from coronary sinus blood; and lactate levels in arterial blood in anesthetized dogs at various times (up to 90 mins) of reperfusion following 90 mins of hypothermic ischemic cardiac arrest. The dogs were divided into three groups: group I, sham bypass; group II, cold crystalloid cardioplegic cardiac arrest; group III, similar to group II but received SOD and catalase treatment. RESULTS: Postpump decreases in cardiac function, contractility and diastolic compliance were associated with increases in PMNL-CL activity, blood MDA, plasma CK and MBCK, and plasma lactate, and decreases in WBC and PMNLs. Prevention of postpump cardiac dysfunction (function and contractility) by SOD and CAT was associated with restoration in PMNL-CL activity, plasma CK and MBCK activity, and blood MDA towards control values although not complete. The levels of plasma lactate, total WBC and PMNLs were similar in group II and group III. CONCLUSIONS: These results suggest that postpump depression of cardiac function and contractility could be due to increased levels of OFRs and that SOD and CAT scavengers of superoxide anion and hydrogen peroxide respectively may be effective in preventing postpump cardiac dysfunction.

Animals↗
PubMed1994

Anaesthesia for coronary artery bypass surgery supplemented with subarachnoid bupivacaine and morphine: a report of 18 cases.

We report our experience with general anaesthesia (GA) supplemented with subarachnoid bupivacaine and morphine for coronary artery bypass surgery (CABG) in 18 patients. Fifteen patients were male, and mean age was 62 yr. Anaesthesia (GA) was induced with alfentanil 97 +/- 22 micrograms.kg-1 and midazolam 0.04 +/- 0.02 mg.kg-1 supplemented with a muscle relaxant, and maintained with isoflurane (0.25-0.5%) in oxygen throughout surgery. Spinal anaesthesia (SA) was then performed at a lumber level using hyperbaric bupivacaine (23-30 mg) and/or lidocaine (150 mg) with morphine (0.5-1 mg). Pooled data showed the following haemodynamic results (P < 0.05). Induction of GA produced a decrease in mean arterial pressure (MAP). Addition of SA produced a decrease in heart rate. Heart rate and MAP did not change with sternotomy. Phenylephrine support of arterial blood pressure was used at some time during operation in 17 patients. Supplementation of GA was minimal. Patients received 2.7 +/- 0.7 coronary grafts. Operating room time was 3.9 +/- 0.6 hr. Postoperative analgesic requirements were minimal, and in half of the patients tracheal extubation occurred on the day of surgery. Complications included one myocardial infarction, one resternotomy, a metabolic encephalopathy in a dialysis-dependent patient, and one case of herpes labialis. No patient recalled intraoperative events. Combined GA with SA may be an effective technique for CABG surgery. Further study of the cardiovascular, neurological and metabolic effects of the technique is required.

Adult↗
PubMed1994

Very brief transient ischemic attack.

TIA is an important risk factor for ischemic stroke. Early diagnosis and management can result in a significant reduction in the risk of subsequent stroke. We report the case of a 54-year-old man who developed a 5-second episode of leg weakness and in whom a tight stenosis of the appropriate carotid artery was found. TIAs can sometimes be brief and have an atypical presentation, requiring a high level of suspicion for early diagnosis.

Carotid Artery, Internal↗
PubMed1992

Oxygen free radicals in volume overload heart failure.

It has been suggested that oxygen free radicals (OFR) depress the excitation-contraction coupling in cardiac muscle. It is possible that a decrease in the cardiac contractility in the failing heart may be due to an increased OFR producing activity of polymorphonuclear (PMN) leukocytes. We studied the OFR producing activity (chemiluminescence) of PMN leukocytes from blood in dogs with heart failure due to chronic volume overload. The animals were divided into two groups: I) normal, (n = 10): II) dogs with mitral insufficiency (MI) of 6 to 9 months duration, (n = 10). Hemodynamic studies were done to establish the presence of heart failure. Blood samples were collected to measure PMN leukocyte chemiluminescence. There was a decrease in the cardiac index and index of myocardial contractility (dp/dt/IIP) and an increase in the left ventricular end-diastolic pressure in dogs with MI indicating left ventricular failure. The peak chemiluminescent activity of the PMN leukocytes in blood of dogs with failure was about four folds greater than that in the blood from normal dogs. These results suggest that there may be an increased OFR generation in dogs with volume overload heart failure. The decrease in the myocardial contractility in the failing heart might be due to an increase in the OFR produced by the PMN leukocytes.

Animals↗
PubMed1992

Increased oxygen free radical activity in patients on cardiopulmonary bypass undergoing aortocoronary bypass surgery.

Cardiac dysfunction after cardiopulmonary bypass (CPB) has been reported by various investigators. Oxygen free radicals have been shown to depress cardiac function and contractility. To evaluate the possible role of oxygen free radicals (OFR) in post-pump cardiac dysfunction, measurements of cardiac function, OFR producing activity of polymorphonuclear (PMN) leukocytes (PMN chemiluminescence) and malondialdehyde (MDA), a lipid peroxidation product, in blood were made at induction of anesthesia (T1), before cross clamping of the aorta (T2), after closure of the chest (T3), and 24 hours postoperatively (T4) in 21 patients undergoing aortocoronary bypass surgery. The total OFR-derived chemiluminescence at T1, T2, T3, and T4 was 1590 +/- 156, 3169 +/- 338, 1972 +/- 214, and 2614 +/- 366 mv.min.10(6) PMN-1, respectively. Superoxide dismutase (SOD)-inhibitable chemiluminescence at T1, T2, T3, and T4 was 1214 +/- 129, 2674 +/- 328, 1752 +/- 215, and 2139 +/- 292 mv.min.10(6) PMN-1, respectively. Superoxide anion at T1, T2, T3, and T4 was 0.99 +/- 0.14, 1.30 +/- 0.17, 1.07 +/- 0.14, and 1.19 +/- 0.12 nmol.10(6) PMN-1.30 min-1, respectively. Blood MDA at T1, T2, T3, and T4 was 0.17 +/- 0.02, 0.25 +/- 0.03, 0.20 +/- 0.03, and 0.23 +/- 0.02 nmol/ml, respectively. OFR-derived and SOD inhibitable chemiluminescence, superoxide anion, and blood MDA increased significantly during CPB and postoperatively. There were decreases in the blood pressure and stroke volume, and increases in the central venous pressure, capillary wedge pressure, and heart rate during CPB and postoperatively. Cardiac output remained unchanged during this procedure. There was leukopenia during CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Use of a nasal continuous positive airway pressure mask in the treatment of postoperative atelectasis in aortocoronary bypass surgery.

Pulmonary oxygen transfer, defined by PaO2/FIO2, and radiologic presence of atelectasis were measured pre-, intra-, and postoperatively to postoperative day 9 in elective cardiac aortocoronary bypass surgical patients, who were randomly allocated either to receive 18 h PEEP while on the ventilator followed by 12 h of nasal continuous positive airway pressure (nasal CPAP) or to be control subjects. The two groups were comparable in age, sex, forced expiratory volume in 1 sec (FEV1), the ratio of FEV1 over forced vital capacity (FVC), time on pump, units of blood transfused, New York Heart Association grading, and cardiac performance indices. The PaO2/FIO2 was significantly (p less than .05) better from half an hour after extubation until 24 h postextubation in the nasal CPAP group, but was decreased for the remainder of the study in both groups. Incidence of atelectasis/consolidation was not different in both groups during the study period. We conclude that nasal CPAP is well tolerated as a treatment of hypoxemia in the immediate postoperative period of aortocoronary bypass patients. CPAP does not change the course of postoperative atelectasis.

Aged↗
PubMed1990

Effects of diltiazem on the functional recovery of the myocardium at organ and cellular level during prolonged hypothermic ischemic cardiac arrest.

The effectiveness of diltiazem on the functional recovery of the heart, calcium (Ca++) uptake and binding, Ca++ ATPase of cardiac sarcoplasmic reticulum (SR), and MB fraction of creatine kinase (MBCK) of coronary sinus blood was investigated after one and a half hours of reperfusion following three hours of ischemic cardiac arrest. The dogs were divided into three groups: group I, sham bypass; group II, cold crystalloid cardioplegia; and group III, cold crystalloid cardioplegia with diltiazem. There was a decrease in aortic pressures left ventricular pressure development (dp/dt), left ventricular work index (LVWI), total systemic vascular resistance (TSVR), and left ventricular systolic pressure (LVSP) in the sham bypass group. There was a decrease in cardiac index (CI), LVWI, and mean right atrial pressure (mRAP) and an increase in TSVR and pulmonary vascular resistance (PVR) in group II as compared with group I. Although there was a tendency for a decrease in the indices of myocardial contractility in group II, they were not significantly different from those in group I. The indices of myocardial contractility, CI, and LVWI in group III were slightly higher than in group II, but they were not significantly different from each other. The values for calcium uptake by SR in groups II and III were similar but significantly lower than those in group I. Calcium binding in group III was significantly lower than that in group I. Calcium ATPase of SR in the three groups were similar. Although MBCK increased in all the groups, the increases were not significantly different among the three groups. The results of this study indicate that cold crystalloid cardioplegia with diltiazem was not better than cold crystalloid alone in preserving the cardiac contractility and cellular function during prolonged ischemic cardiac arrest. However, the cardiac function in terms of cardiac index was better preserved with diltiazem.

Adenosine Triphosphatases↗
PubMed1989

Increased production of oxygen free radicals by polymorphonuclear leukocytes in heart failure due to aortic stenosis.

Oxygen free radicals have been linked to a wide variety of cellular damage in biological systems. Polymorphonuclear (PMN) leukocytes stimulation is one of the known sources for oxygen free radicals. It has been suggested that oxygen free radicals depress the excitation-contraction coupling in cardiac muscle. It is possible that a decrease in the myocardial contractility in heart failure might be due to an increased oxygen-free-radical-producing activity of PMN leukocytes. The authors studied, therefore, the release of oxygen free radicals, as measured by luminol-dependent chemiluminescence activity, from the PMN leukocytes in dogs with heart failure due to aortic stenosis. Hemodynamics and phagocytic activity of PMN leukocytes were studied in 6 control dogs and 6 dogs with aortic stenosis of six to nine months' duration. There was a significant decrease in the index of myocardial contractility and an increase in the left ventricular end-diastolic pressure in dogs with aortic stenosis, suggesting left ventricular failure in these dogs. Although there was a tendency for a decrease in the cardiac index in dogs with aortic stenosis, the decrease was not significant. Phagocytic activity of PMN leukocytes in blood was studied in control dogs and dogs with aortic stenosis. Phagocytosis was initiated by addition of opsonized zymosan and chemiluminescence was monitored by use of a luminometer. The peak chemiluminescence activity of the PMN leukocytes in blood of dogs with heart failure was about threefold greater than that in the blood from control dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Increased chemiluminescence of polymorphonuclear leucocytes in dogs with volume overload heart failure.

Polymorphonuclear leucocyte (PMN) stimulation is known to generate oxygen free radicals. Exogenous oxygen free radicals, generated by xanthine and xanthine oxidase, have been implicated in the decrease of cardiac contractility. It is possible that PMN have increased capacity to release oxygen free radicals in failing heart. It was, therefore, decided to investigate PMN chemiluminescence (oxygen free radicals) from blood in dogs with heart failure due to chronic volume overload. The dogs were divided into two groups: (A) normal, six dogs; (B) dogs with mitral insufficiency (MI) of 6-9 months' duration, six dogs. Haemodynamic parameters were recorded to assess cardiac failure. Mixed venous blood was collected to measure PMN chemiluminescence. Stimulation of PMN was initiated by addition of opsonized zymosan and chemiluminescence was monitored using a luminometer. The haemodynamic parameters in dogs with MI showed that these dogs had left ventricular failure. The peak chemiluminescent activity of PMN in blood of dogs with left ventricular failure was approximately four times that in the blood from normal dogs. This increase in chemiluminescence reflects an increase in the generation of oxygen free radicals from PMN in dogs with chronic heart failure. The decrease in the myocardial contractility in cardiac failure might be due to an increase in the oxygen free radicals produced by the PMN.

Animals↗
PubMed1988

The resting surface electrocardiogram as a predictor of future hypertension.

Resting supine and post-provocation (dynamic exercise, isometric exercise and cold pressor) levels of blood pressure were measured in 80 normotensive offspring of normotensive parents (control) and 55 normotensive offspring of parents with essential hypertension. The surface electrocardiogram (including conventional twelve leads, posterior chest leads, right-sided chest leads and bipolar precordial leads) was also recorded in all subjects. Twenty-eight offspring of parents with essential hypertension had their resting and/or post-provocation blood pressure above the upper limit of standard deviation in age- and sex-matched control group. Flat or upright T waves, with either S waves less than 0.2 mV, or S/R ratio less than 2, or T waves equal to or higher than the accompanying R waves in lead V4R, could identify these potential hypertensives with nearly 90% specificity and nearly 75% sensitivity. The criterion had been derived, however, by analysis of the data achieved retrospectively. Therefore, the exact discriminating value of this criterion can be assessed only by a long-term prospective study.

Adolescent↗
PubMed1988

Effects of blood and crystalloid cardioplegia on cardiac function at organ and cellular levels during hypothermic cardiac arrest.

The present investigation was undertaken to compare the effects of cold crystalloid and blood cardioplegia on the functional recovery of the heart; on Ca++ binding and uptake, Ca++-ATPase of the sarcoplasmic reticulum (SR), and sarcolemmal (SL) ATPase; and on serum MB fraction of creatine kinase (MBCK) after one and half hours of reperfusion following one hour of ischemic cardiac arrest in dog. This study was made also to determine if the functional changes are related to the changes in biochemistry at the molecular level. The dogs were divided into three groups: sham bypass (SB), cold crystalloid cardioplegia (CC), and pump blood cardioplegia (PB). There was a decrease in the cardiac index (CI), left ventricular work index (LVWI), and mean aortic pressure (MAP) in all three groups. The index of myocardial contractility [dp/dt)/IIP) and CI were lower in the CC group as compared with the SB and PB groups. All the hemodynamic values for the PB group were similar to those of the SB group except total systemic vascular resistance (TSVR) and left ventricular end-diastolic pressure (LVEDP) which were lower in the PB group. The index of myocardial contractility and cardiac index appeared to be greater in the PB group than in the CC group. There was a decrease in the Ca++ uptake by SR from both the CC and PB groups. Ca++ binding and Ca++,-ATPase of SR from the PB group were depressed. The sarcolemmal ATPase was unaffected in both groups. The serum MBCK increased in both PB and CC groups, though the increase was smaller in the PB group. These results indicate that the functional recovery of the heart was slightly better with pump blood cardioplegia than with cold crystalloid cardioplegia. The depressed myocardial contractility and cardiac function in the CC group were associated with a decrease in the Ca++ uptake by SR. However, the decreases in the Ca++ binding, Ca++ uptake, and Ca++ ATPase by SR from the pump blood cardioplegic group were not accompanied by decreases in the cardiac contractility and cardiac function. Myocardial damage as assessed by serum MBCK was smaller in the PB group than in the CC group.

Animals↗
PubMed1988

High 2,3-DPG blood cardioplegia and myocardial preservation during cardiopulmonary bypass.

Blood may provide superior cardioplegia compared with crystalloid cardioplegic solution. However, the results are controversial. This may be due to a leftward shift of the hemoglobin (Hb)-O2 dissociation curve induced by hypothermia, increasing the oxygen affinity for Hb. This effect may negate the potential benefit of blood cardioplegia. The oxygen affinity for Hb can be decreased by increasing the red cell 2,3-diphosphoglycerate (2,3-DPG), and hence, more oxygen can be delivered to the myocardium. The present investigation was undertaken to study the effects of 2,3-DPG-enriched blood cardioplegia on the functional recovery of the myocardium and changes in the coronary sinus red blood cell (RBC) adenosine-triphosphate (ATP), lactate, and RBC DPG after one and a half hours of reperfusion following one hour of ischemic cardiac arrest in dogs. The dogs were divided into three groups: crystalloid (CR); stored blood (SB), and high 2,3-DPG blood (HDPG) cardioplegic groups. Incubation of canine RBC in phosphoenal pyruvate (PEP) led to a 36% increase in DPG and a rightward shift in the Hb-O2 dissociation curve. There was a 4 mm Hg shift in the P50. When compared with the CR group, there was a significant decrease in the cardiac index (CI) and left ventricular work index (LVWI) and a significant increase in the total systemic vascular resistance (TSVR) in the SB group. The CI and LVWI of the HDPG group were similar to those of the CR group, but the TSVR was significantly greater in the former group. The LVWI was significantly greater and the TSVR smaller in the HDPG group as compared with those in the SB group.(ABSTRACT TRUNCATED AT 250 WORDS)

2,3-Diphosphoglycerate↗