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Biomedical subjects

T D Ivey

Publications and source records attributed to T D Ivey.

At least 19 recordsLinked to original sources
PubMed2001

Serum concentrations of cefuroxime after continuous infusion in coronary bypass graft patients.

OBJECTIVE: To describe the serum concentrations of continuous infusion of cefuroxime for postsurgical prophylaxis of sternal wound infection in patients undergoing coronary artery bypass graft (CABG), and to assess the incidence of sternal wound infection in this population. METHODS: This was a prospective, noncomparative trial involving 54 patients undergoing elective CABG surgery. All patients enrolled in the study received cefuroxime 1.5 g as a single intravenous dose 30 minutes preoperatively, followed by a continuous infusion of 3 g every 24 hours until removal of all central venous catheters. RESULTS: Of the 53 evaluable patients, the mean steady-state cefuroxime serum concentration was 21.6 +/- 14.2 microg/mL (range 6.56-59.5). No patient developed a sternal wound infection. The mean treatment duration was 2.58 +/- 2.13 days (range 1-13). The median hospital and intensive care unit lengths of stay were six days and 46 hours, respectively. The average antibiotic cost per day was $32.76. CONCLUSIONS: These preliminary results of continuous infusion of cefuroxime 3 g/d for prophylaxis of sternal wound infections in CABG patients indicate that serum concentrations are highly variable, but reliably above the minimum inhibitory concentration for the common anticipated pathogens in this setting. Further comparative trials in a larger number of patients are necessary before this mode of administration can be routinely advocated for prophylaxis.

Adult↗
PubMed1996

Giant organized pericardial hematoma producing constrictive pericarditis: a case report and review of the literature.

Massive organized pericardial hematoma secondary to blunt trauma is extremely rare. We report a case of a 69-year-old man referred with refractory ascites who was found to have a 10 x 6 x 8 cm organized pericardial hematoma with hemodynamic characteristics consistent with constrictive pericarditis. The cause was attributed to blunt chest trauma associated with a fall 3 years previously. Excision of the mass and removal of the constricting epicardium relieved his symptomatology. A review of the literature is included.

Accidental Falls↗
PubMed1995

Skin temperature and limb blood flow as predictors of cardiac index.

Thermodilution cardiac output and cardiac index (CI) require inserting a pulmonary artery catheter, an invasive device associated with many iatrogenic complications. The purpose of this study was to establish the concurrent validity of two noninvasive measures of CI (skin temperature and limb blood flow) by determining their correlation with invasive CI. Twenty-one subjects undergoing coronary artery bypass grafting (CABG) were studied every 2 hours for 8 hours in the immediate postoperative period. Neither limb blood flow (LBF) nor skin temperature at five sites correlated significantly (p < .05) with CI at all five data collection times. Ankle temperature and LBF were significantly correlated with CI at one data collection time. On the basis of the findings of this study, neither skin temperature nor LBF can be used as a noninvasive predictor of CI in the immediate postoperative period following CABG.

Adult↗
PubMed1990

Transvenous defibrillation in humans via the coronary sinus.

A consistently effective transvenous defibrillation system for use in automatic defibrillators could significantly alter the approach to patients at risk of sudden death. Transvenous defibrillation systems that use a right ventricular (RV) electrode only or an RV electrode in combination with a chest patch are relatively inefficient at applying current to the posterolateral left ventricle. An RV electrode combined with a coronary sinus (CS) electrode, however, may improve current distribution to the posterolateral left ventricle. The purpose of this investigation, therefore, was to evaluate the effectiveness and safety of a specially designed transvenous lead system with a CS electrode capable of current delivery to this relatively inaccessible region of the heart. In 20 survivors of cardiac arrest, we determined defibrillation efficacy immediately before defibrillator surgery for monophasic pulses delivered between an RV catheter electrode and a CS catheter electrode system and compared these findings with an RV catheter electrode-thoracic patch defibrillation system. Subsequently, we referenced the efficacy of both transvenous systems to an epicardial patch electrode system at the time of defibrillator implantation. The mean delivered-energy defibrillation threshold for the CS-RV electrode system was 17.5 +/- 7.9 J, which was substantially lower than the RV electrode-thoracic patch system (25.6 +/- 11.4 J, p = 0.0016 [46% more]). Defibrillation threshold voltage was 529 +/- 123 V for the CS-RV electrode system and 647 +/- 164 V (22% more) for the RV electrode-thoracic patch system (p = 0.0013).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Vessels↗
PubMed1990

Myocardial preservation: a comparison of oxygenated crystalloid and blood cardioplegia.

The purpose of this experiment was to compare myocardial protective effect after global ischemia using oxygenated crystalloid (CCcO2) and an oxygenated blood (BCcO2) cardioplegic solutions. Post-ischemic ventricular performance was studied in 2 equal (n = 7) groups of dogs subjected to 120 min of global ischemia induced at average myocardial temperatures of 8 degrees C in the CCcO2 group and 18 degrees C in the BCcO2 group. Left ventricular (LV) function included analysis of LV systolic function (global and regional function), LV diastolic function (chamber and myocardial stiffness) and LV relaxation was measured by sonomicrometry and Millar micrometers. Data were processed with a Dec PDP-11/23 computer. In vitro oxygen content (Vol%) measured 3.2 +/- 1.0 (CCcO2) and 9.5 +/- 0.3 (BCcO2). Percent recoveries of LV global function (LVSP, loop area, % shortening, LV dp/dt, mean VCF and E max) in the CCcO2 group were approximately the same as those in the BCcO2 group. There were no significant differences in LV regional function (loop area and % shortening) after ischemia between the two groups. The chamber and myocardial stiffness after ischemia in the CCcO2 group were almost the same as the baseline values. Values in the BCcO2 group were reduced significantly compared to the baseline level. There were significant differences in post-ischemic chamber and myocardial stiffness between the two groups. Post-ischemic maximum negative LV dp/dt in both groups decreased significantly compared to the baseline values. However, the time constant and diastolic interval after ischemia in both groups were approximately the same as the baseline values. We conclude that there were no significant differences in myocardial protective effect between the CCcO2 and BCcO2 groups, and both methods preserved the ischemic myocardium well.

Animals↗
PubMed1990

Short-term morbidity and mortality of implantation of automatic implantable cardioverter-defibrillator.

Over the 3-year period from Jan. 1, 1986, through Dec. 31, 1988, we have implanted 101 automatic implantable cardioverter-defibrillators into patients with life-threatening ventricular arrhythmias. There were 82 male patients and 19 female patients. The mean age was 58 years with a range of 25 to 82 years. The indication for implantation was ventricular fibrillation in 89 patients and recurrent ventricular tachycardia in 12 patients. Seventy-seven patients had a history of prior myocardial infarction or coronary artery disease, or both. Eighteen patients had nonischemic cardiomyopathy. One patient had a prolonged QT syndrome and five patients had no evidence of preexisting structural heart disease. The mean injection fraction was 37% +/- 17%. Forty-one of the automatic implantable cardioverter-defibrillator implantations were associated with procedures necessitating cardiopulmonary bypass. The hospital mortality rate was 4% and the morbidity rate was 15%. The only statistical difference between those patients who did and did not have postoperative complications was a history of a prior myocardial infarction (90% versus 54%, p less than 0.05). Twenty percent of patients had new-onset postoperative atrial fibrillation after implantation of the device. Eleven percent of patients had sustained ventricular tachycardia postoperatively. Although there was a trend toward a higher complication/death rate in the patients whose automatic implantable cardioverter-defibrillator was inserted in association with cardiopulmonary bypass (24% versus 15%) and the occurrence of new-onset postoperative atrial fibrillation (27% versus 15%), these findings were not statistically significant. Automatic implantable cardioverter-defibrillator implantation with and without concomitant cardiopulmonary bypass is associated with a clinically important morbidity and mortality rate and development of postoperative arrhythmias.

Adult↗
PubMed1989

Evaluation of electrode polarity on defibrillation efficacy.

The effect of electrode polarity on defibrillation thresholds in humans is unknown. This prospective, randomized evaluation of electrode polarity on defibrillation thresholds was performed in 21 survivors of ventricular fibrillation (VF) undergoing cardiac surgery. Defibrillation was always performed with 2 identical large rectangular, wire mesh electrodes positioned over the anterior wall of the right ventricle and the posterolateral wall of the left ventricle. The initial electrode polarity for the left ventricular (LV) electrode was chosen randomly for determination of the defibrillation threshold. Subsequently, electrode polarity was reversed. The defibrillation threshold was defined as the lowest pulse amplitude that would effectively terminate VF with a single discharge delivered 10 seconds after initiation of an episode of VF with alternating current. For each defibrillation pulse, voltage, current, resistance and delivered energy were recorded. Of the 21 patients, 15 (71%) had a lower defibrillation threshold when the LV electrode was positive, 2 patients (10%) had a lower defibrillation threshold when the LV electrode was negative and 4 patients (19%) had equal defibrillation thresholds (within 0.5 J) regardless of polarity. The mean leading edge defibrillation threshold voltage was 370 +/- 88 volts when the LV electrode was negative and 320 +/- 109 volts (14% less) when the LV electrode was positive (p = 0.014). Mean leading edge defibrillation threshold current was 9.3 +/- 3.1 amps when the LV electrode was negative compared to 7.7 +/- 3.1 amps (17% less) when the LV electrode was positive (p = 0.0033). There were no differences in resistance with the 2 configurations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Prospective comparison of sequential pulse and single pulse defibrillation with use of two different clinically available systems.

Sixteen out-of-hospital survivors of ventricular fibrillation underwent a prospective, randomized, intraoperative comparison of sequential pulse and single pulse defibrillation with use of two distinct electrode systems and waveform shapes currently available for clinical use. Defibrillation was tested alternately with either the single pulse or the sequential pulse system 10 s into an episode of ventricular fibrillation. Sequential pulse defibrillation was performed with two 4 ms truncated exponential pulses of constant duration delivered to three equally spaced oval epicardial patch electrodes composed of concentric coils. The posterior left ventricular electrode served as the common cathode. The first anode was over the anterior right ventricle and the second anode was over the anterior left ventricle. Single pulse defibrillation was performed with the standard intracardiac defibrillation system with use of a single truncated exponential pulse with a fixed 65% tilt delivered across two rectangular, wire mesh epicardial patch electrodes positioned over the anterior right ventricle and posterolateral left ventricle. During defibrillation threshold determination, voltage and current waveforms were recorded and used to determine pulsing resistance and delivered and stored energy. Average defibrillation threshold leading edge voltage for the single pulse technique was 273 +/- 101 V compared with 246 +/- 67 V (11% less) for the sequential pulse technique (p = 0.136). Defibrillation threshold leading edge current for the single pulse technique was 6.7 +/- 2.5 A compared with 5.2 +/- 1.7 A (29% less) for the sequential pulse method (p = 0.005). The defibrillation threshold delivered energy was 5.6 +/- 4.0 J for the single pulse technique and 3.5 +/- 1.8 J (38% less) for the sequential pulse technique (p = 0.021).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

A prospective randomized evaluation of biphasic versus monophasic waveform pulses on defibrillation efficacy in humans.

Biphasic waveforms have been suggested as a superior waveform for ventricular defibrillation. To test this premise, a prospective randomized intraoperative evaluation of defibrillation efficacy of monophasic and biphasic waveform pulses was performed in 22 survivors of out of hospital ventricular fibrillation who were undergoing cardiac surgery for implantation of an automatic defibrillator. The initial waveform used in a patient for defibrillation testing, either monophasic or biphasic, was randomly selected. Subsequently, each patient served as his or her own control for defibrillation testing of the other waveform. The defibrillation threshold was defined as the lowest pulse amplitude that would effectively terminate ventricular fibrillation with a single discharge delivered 10 s after initiation of an episode of ventricular fibrillation induced with alternating current. Each defibrillation pulse was recorded oscilloscopically, and defibrillation pulse voltage, current, resistance and stored energy were measured. Fifteen (68%) of the 22 patients had a lower defibrillation threshold with the biphasic pulse, 3 (14%) had a lower threshold with the monophasic pulse and 4 (18%) had equal defibrillation thresholds (within 1.0 J) regardless of waveform. The mean leading edge defibrillation threshold voltage was 317 +/- 105 V when the monophasic pulse was used and 267 +/- 102 V (16% less) when the biphasic pulse was used (p = 0.008). Mean leading edge defibrillation threshold current was 7.9 +/- 3.7 A when the monophasic pulse was used and 6.8 +/- 3.8 A (14% less) when the biphasic pulse was used (p = 0.051).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

A prospective, randomized evaluation of effect of ventricular fibrillation duration on defibrillation thresholds in humans.

The effect of ventricular fibrillation duration in humans on defibrillation efficacy as it pertains to the time of intervention of an automatic implantable defibrillator is unknown. If a difference in defibrillation efficacy exists in the early period after ventricular fibrillation onset, it may affect algorithms used by antiarrhythmic devices for arrhythmia detection and therapy. Therefore, a prospective, randomized evaluation was performed of the effect of ventricular fibrillation durations of 10 s and 20 s on defibrillation thresholds in 10 survivors of sudden cardiac arrest undergoing implantation of an automatic cardioverter defibrillator. The initial duration of ventricular fibrillation was chosen randomly. Subsequently, each patient served as his or her own control for the alternate duration of ventricular fibrillation to that chosen initially. The mean leading edge defibrillation threshold voltage was 411 +/- 114 V when ventricular fibrillation persisted for 10 s and 419 +/- 125 V when it persisted for 20 s (p = 0.73). The mean defibrillation threshold current was 11.4 +/- 2.8 A when ventricular fibrillation persisted for 10 s and 11.4 +/- 3.2 A when it persisted for 20 s (p = 0.97). The delivered energy defibrillation threshold was 11.5 +/- 5.9 J when ventricular fibrillation persisted for 10 s and 12.0 +/- 6.9 J when it persisted for 20 s (p = 0.67). These findings show that the defibrillation threshold does not change between 10 and 20 s of ventricular fibrillation in out-of-hospital survivors of cardiac arrest at the time of surgical implantation of an automatic defibrillator. The data may have influence on the programming of defibrillator detection algorithms.

Algorithms↗
PubMed1989

Effect of voltage and charge of electrical ablation pulses on canine myocardium.

Multiple paired lesions produced by a train of high-voltage low-charge rectangular pulses (20 A, 30 microsecond) and a train of low-voltage high-charge rectangular pulses (2 A, 300 microsecond) were made to the left ventricular epicardium of 23 dogs to determine the relative influence of voltage and charge delivery on injury of canine myocardium. Both pulsing methods contained equal amounts of energy (15 J) delivered over equal periods of time (100 ms), and both pulsing methods were nonarcing and therefore nonbarotraumatic. The volume of cardiac tissue injury resulting from both types of pulses was then evaluated from planimetered serial histological sections after 1, 10, and 30 days. Over the 30-day period, lesion size progressively decreased to 56% of its original value for the high-voltage low-charge pulse. In contrast, lesion size from the low-voltage high-charge pulse remained relatively constant, decreasing only 12% of its original value. These results indicate that when energy delivery is held constant, voltage, not charge, is the dominant mediator of cell injury. Also, cells subjected to high voltages appear to recover partially over time with significantly less constancy of tissue injury than that seen with low-voltage high-charge pulses.

Animals↗
PubMed1989

Direct surgical treatment of atrioventricular node reentrant tachycardia.

Atrioventricular node reentry tachycardia is a common type of supraventricular tachycardia. Rarely is it incapacitating and refractory to drug therapy, but when it is, the only option in therapy until recently has been atrioventricular node ablation or antitachycardia pacemaker insertion. The purpose of this paper is to review the case histories of four patients in whom we have surgically abolished atrioventricular node reentrant tachycardia while intentionally preserving atrioventricular node conduction. All four patients had atrioventricular node reentrant tachycardia confirmed by electrophysiologic study as diagnosed by established criteria. One patient had a left posterior atrioventricular accessory pathway, in addition to atrioventricular node reentrant tachycardia. All patients underwent intraoperative epicardial and endocardial mapping. Direct surgical dissection of the atrioventricular node node was performed in all four patients during normothermic cardiopulmonary bypass. Early and late postoperative electrophysiologic studies were used to evaluate the success of the surgical dissection. None of the patients had any evidence of dual atrioventricular node pathways or spontaneous or inducible atrioventricular node reentrant tachycardia postoperatively. At last follow-up (15 weeks to 21 months postoperatively), all patients were free from arrhythmias and cardiac medications, all were in normal sinus rhythm, and all had a subjectively improved life-style. This technique of direct surgical dissection of the atrioventricular node during normothermic cardiopulmonary bypass has allowed for complete cure of atrioventricular node reentrant tachycardia, while maintaining normal atrioventricular node function in these four patients.

Adult↗
PubMed1989

Coronary artery bypass graft surgery early after acute myocardial infarction.

Seven hundred ninety-three patients had coronary artery bypass graft (CABG) surgery within 30 days after acute myocardial infarction (AMI) between August 1982 and July 1987. Hospital mortality was 5.7%. Age, surgical priority, prior CABG surgery, congestive heart failure (CHF), and type of AMI were associated with increased hospital mortality by logistic regression analysis of nine independent variables. When the analysis was carried out separately for men and women, the same predictive variables were identified for men, but only surgical priority and age were predictive of operative mortality for women. Elective CABG surgery can be carried out at low risk following AMI in stable patients regardless of the interval between AMI and surgery. Patients who undergo urgent or emergency surgery and those who have CHF, Q wave infarction, or a history of prior AMI are at increased risk.

Adult↗
PubMed1989

Neurobehavioral outcomes in cardiac operations. A prospective controlled study.

To assess the severity and duration of new organic brain dysfunction after cardiac operations, we used an extensive battery of neuropsychologic tests to evaluate 65 patients undergoing coronary artery bypass grafting and 25 patients undergoing intracardiac operations with cardiopulmonary bypass. Patients were tested the day before the operation, before discharge from the hospital, and approximately 7 months later. Compared to 47 nonsurgical control subjects tested at comparable time intervals, surgical subjects showed generalized impairment of neuropsychologic abilities near the time of discharge from the hospital. At follow-up testing, there was no evidence of residual impairment among the surgically treated patients as a whole. In fact, they showed greater improvement compared to initial test scores than did control subjects. However, performance of 10 patients (11%) declined on half of the neuropsychologic variables between preoperative and follow-up testing. Neurobehavioral outcome was not related to the type of operation (coronary bypass versus intracardiac), to factors of cardiopulmonary bypass (duration, aortic occlusion time, hypotension, arterial carbon dioxide tension, minimum hematocrit value, minimum temperature). The only predictor of negative outcome was advanced age. We conclude that, although neurobehavioral impairment is common during hospitalization after cardiac operations, the prognosis for eventual full recovery is favorable, although less so among the elderly.

Anxiety↗
PubMed1988

Prospective evaluation of initially ineffective defibrillation pulses on subsequent defibrillation success during ventricular fibrillation in survivors of cardiac arrest.

The effect of initially ineffective defibrillation pulses on subsequent defibrillation success is not known. Therefore, the voltage, current and energy at the defibrillation threshold were compared with the defibrillation rescue pulse voltage, current and energy that terminated ventricular fibrillation when an ineffective pulse just below the defibrillation threshold had been used initially. This lower amplitude ineffective pulse was termed a "subdefibrillation threshold" pulse. The pulse that restored sinus rhythm after the subdefibrillation threshold pulse was delivered was termed the "subdefibrillation threshold rescue pulse." This comparison was undertaken, intraoperatively, in 14 out-of-hospital cardiac arrest survivors using a sequential-pulse catheter-patch defibrillation system. Each of the 14 patients required higher voltage, current, delivered energy and stored energy for defibrillation with the subdefibrillation threshold rescue pulse than with the defibrillation threshold pulse. The defibrillation threshold voltage was 451 +/- 127 volts compared with a subdefibrillation threshold rescue voltage of 585 +/- 147 volts (p less than 0.00002). The defibrillation threshold current was 5.5 +/- 2.4 amps compared with a subdefibrillation threshold rescue current of 7.2 +/- 2.7 amps (p less than 0.00001). Delivered and stored energies were 10.9 +/- 7.4 and 12.3 +/- 7.2J, respectively, for the defibrillation threshold pulse and were 17.6 +/- 9.4 J (p less than 0.00002) and 20.5 +/- 9.3 J (p less than 0.00005), respectively, for the subdefibrillation threshold rescue pulse. It is concluded that the risk of requiring considerably higher energies than anticipated for defibrillation must be incurred, should defibrillation fail because of an initially insufficient defibrillation pulse.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Developments, complications and limitations of catheter-mediated electrical ablation of posterior accessory atrioventricular pathways.

Nineteen patients with posterior accessory pathways and disabling, refractory arrhythmias, underwent catheter ablation using standard defibrillator pulses at energy settings of 150 to 400 J. Accessory pathway ablation was successful in 13 of 19 (68%). Effective catheter ablation correlated with local ventriculoatrial (VA) intervals determined from the coronary sinus catheter at the site of earliest retrograde atrial activation during orthodromic reciprocating tachycardia. In 12 of the 13 successfully ablated patients, the local VA interval was less than 80 ms. In 4 of the 6 unsuccessfully treated patients, the local VA interval was greater than or equal to 80 ms, p less than 0.01. Transient abnormalities noted with the procedure included sinus bradycardia (3 patients), atrioventricular block (5), accelerated junctional rhythm (3), ectopic atrial tachycardia (2), myocardial depression (1), "ischemic" appearing T-wave inversions (10) and hemodynamically insignificant small pericardial effusions (5) Creatine kinase-MB increased from 3 +/- 2 U/liter to 26 +/- 18 U/liter (p less than 0.001), 4 to 8 hours after ablation. In addition, electrical shorts occurring during the ablation procedure in 2 patients were identified and corrected only with oscilloscopic monitoring of voltage and current waveforms. Significant adverse sequelae were seen in 4 patients. Three patients required sternotomy for control of cardiac tamponade secondary to a ruptured coronary sinus and 1 patient had a small posterior left ventricular infarction related to spasm of a right coronary artery extension branch. Coronary sinus rupture correlated with the ratio of catheter diameter to coronary sinus diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Clinical assessment of a flow-through fluorometric blood gas monitor.

We performed an observational study to evaluate a flow-through fluorometric instrument (Gas-STAT) that continuously measures the carbon dioxide tension (PCO2), oxygen tension (PO2), and pH of blood in the cardiopulmonary bypass circuit. Setup and calibration of the instrument typically required 20 minutes. During bypass, 129 blood samples were drawn from 16 patients for comparison with conventional measurements obtained with a blood gas machine. Data for each variable, within each sensor, were analyzed by linear regression. The ranges of the standard errors of the estimate were 0.7 to 4.2 mm Hg for PCO2, 18.3 to 78.7 mm Hg for the high PO2 range, 1.4 to 7.1 mm Hg for the low PO2 range, and 0.008 to 0.049 for pH. The regression lines differed from the identity line (P less than 0.05) in at least one variable in most patients, and large deviations from the line of identity in both slope and intercept were common. Among 58 sensors evaluated, failures occurred in 5 (2.9%) of the 174 optodes, and minor leakage occurred in 2 (3.4%) of the flow-through cells. We conclude that although this flow-through fluorometric instrument is an adequate monitor of trends in blood gases during cardiopulmonary bypass, it is not accurate enough to supplant conventional laboratory measurements.

Blood Gas Analysis↗