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Biomedical subjects

B H Dorman

Publications and source records attributed to B H Dorman.

At least 37 records · Page 2Linked to original sources
PubMed1996

Preservation of myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest with 2, 3-butanedione monoxime.

One proposed contributory mechanism for depressed ventricular performance after hypothermic, hyperkalemic cardioplegic arrest is a reduction in myocyte contractile function caused by alterations in intracellular calcium homeostasis. Because 2,3-butanedione monoxime decreases intracellular calcium transients, this study tested the hypothesis that 2,3-butanedione monoxime supplementation of the hyperkalemic cardioplegic solution could preserve isolated myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest. Myocytes were isolated from the left ventricles of six pigs. Magnitude and velocity of myocyte shortening were measured after 2 hours of incubation under normothermic conditions (37 degrees C, standard medium), hypothermic, hyperkalemic cardioplegic arrest (4 degrees C in Ringer's solution with 20 mEq potassium chloride and 20 mmol/L 2,3-butanedione monoxime). Because beta-adrenergic agonists are commonly employed after cardioplegic arrest, myocyte contractile function was examined in the presence of the beta-agonist isoproterenol (25 nmol/L). Hypothermic, hyperkalemic cardioplegic arrest and rewarming reduced the velocity (32%) and percentage of myocyte shortening (27%, p < 0.05). Supplementation with 2,3 butanedione monoxime normalized myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest. Although beta-adrenergic stimulation significantly increased myocyte contractile function under normothermic conditions and after hypothermic, hyperkalemic cardioplegic arrest, contractile function of myocytes exposed to beta-agonist after hypothermic, hyperkalemic cardioplegic arrest remained significantly reduced relative to the normothermic control group. Supplementation with 2,3-butanedione monoxime restored beta-adrenergic responsiveness of myocytes after hypothermic, hyperkalemic cardioplegic arrest. Thus, supplementation of a hyperkalemic cardioplegic solution with 2,3-butanedione monoxime had direct and beneficial effects on myocyte contractile function and beta-adrenergic responsiveness after cardioplegic arrest. A potential mechanism for the effects of 2,3-butanedione monoxime includes modulation of intracellular calcium transients or alterations in sensitivity to calcium. Supplementation with 2,3-butanedione monoxime may have clinical utility in improving myocardial contractile function after hypothermic, hyperkalemic cardioplegic arrest.

Animals↗
PubMed1996

Intravenous sedation for placement of automatic implantable cardioverter-defibrillators.

OBJECTIVE: To evaluate a change in anesthetic technique for transvenous placement of the automatic implantable cardioverter-defibrillator (ICD). DESIGN: Retrospective study. SETTING: A university hospital. PARTICIPANTS: Twenty-eight patients who underwent placement of ICDs. INTERVENTIONS: Thirteen patients had the ICD placed via the transvenous approach with general anesthesia (group GA). Fifteen patients had the ICD placed via the transvenous approach with intravenous sedation (group IV). MEASUREMENTS AND MAIN RESULTS: Intraoperative systolic and diastolic blood pressures were significantly higher in group IV compared with group GA. The ICD was successfully placed in all patients in both groups. There were no intraoperative complications noted in either group during induction of fibrillation and defibrillation, and there was no recall by any patient in either group. The average hospital stay was significantly less in group IV (1.8 days) compared with group GA (3.4 days). CONCLUSIONS: Intravenous sedation for the placement of ICDs is a safe and effective technique. Patients who had their ICD placed while receiving intravenous sedation experienced higher intraoperative blood pressures and were discharged from the hospital earlier than those patients who received general anesthesia.

Aged↗
PubMed1996

The direct effects of propofol on myocyte contractile function after hypothermic cardioplegic arrest.

Propofol is being used more often in cardiac surgery, particularly after hypothermic, hyperkalemic cardioplegic arrest (HHCA). The purpose of this study was to examine the effects of propofol on isolated myocyte contractile function under both normothermic conditions and after simulated HHCA and rewarming. Myocytes were isolated from the left ventricle of eight pigs. Myocyte contractile function was measured under both normothermic conditions and after simulated HHCA (incubation at 4 degrees C for 2 h in crystalloid cardioplegia; K+ = 24 mEq/L) using computer-assisted videomicroscopy in the presence of 2, 4, and 6 micrograms/mL propofol (11.2, 22.4, and 33.6 microM/L, respectively). Isoproterenol (25 nM) was then added and contractile function measurements repeated. Propofol caused significant dose-dependent reductions in myocyte velocity of shortening (baseline = 67 +/- 2 microns/s; propofol = 2 micrograms/mL, 45 +/- 4 microns/s; and propofol = 6 micrograms/mL, 27 +/- 3 microns/s; P < 0.05). HHCA and rewarming caused a significant reduction in myocyte velocity of shortening (29 +/- 0.9 microns/s, P < 0.05), with further significant dose-dependent reductions in contractile function after the addition of propofol. Propofol caused a decrease in beta-adrenergic responsiveness under normothermic conditions, but not after simulated HHCA. Results from the present study demonstrated for the first time that the reduction in isolated myocyte contractile function after simulated HHCA is further decreased by propofol administration.

Adrenergic beta-Agonists↗
PubMed1996

The effect of bupivacaine skull block on the hemodynamic response to craniotomy.

The placement of pointed cranial pins into the periosteum is a recognized acute noxious stimulation during intracranial surgery which can result in sudden increases in blood pressure and heart rate, causing increases in intracranial pressure. A skull block (blockade of the nerves that innervate the scalp, including the greater and lesser occipital nerves, the supraorbital and supratrochlear nerves, the auriculotemporal nerves, and the greater auricular nerves) may be effective in reducing hypertension and tachycardia. Twenty-one patients were allocated in a prospective, double-blind fashion to a control group or a bupivacaine group. After a standardized induction and 5 min prior to head pinning, a skull block was performed. Patients in the control group received a skull block of normal saline, while the bupivacaine group received a skull block with 0.5% bupivacaine. Systolic (SAP), diastolic (DAP), mean arterial pressure (MAP), heart rate (HR), and end-tidal isoflurane were recorded at the following times: 5 min after the induction of anesthesia, during performance of the skull block, during head pinning, and 5 min after head pinning. Significant increases in SAP of 40 +/- 6 mm Hg, DAP of 30 +/- 5 mm Hg, MAP of 32 +/- 6 mm Hg, and HR of 22 +/- 5 bpm occurred during head pinning in the control group, while remaining unchanged in the bupivacaine group. These results demonstrate that a skull block using 0.5% bupivacaine successfully blunts the hemodynamic response to head pinning.

Adolescent↗
PubMed1995

Protamine use during peripheral vascular surgery: a prospective randomized trial.

PURPOSE: One hundred twenty patients undergoing aortic reconstruction (40), infrainguinal bypass (49), and carotid endarterectomy (31) were prospectively enrolled into a double-blind randomized trial to investigate the utility of routine heparin reversal with protamine. METHODS: All patients underwent systemic heparinization with 90 U/kg body weight during operation and after revascularization were randomized to receive either protamine or saline solution for heparin reversal. Blood loss was measured throughout the surgical procedure, and indexes of coagulation and the requirement for blood and blood products were documented during operation and the first 24 hours after operation. RESULTS: Plasma heparin concentration, partial thromboplastin time, and activated clotting time were significantly higher (p < 0.05) in those receiving saline solution at 20 minutes and 1 hour after administration. Total surgical blood loss was not significantly different between study groups. No significant differences were found in blood product requirement, intravenous fluid administered, hematocrit, or wound hematomas between groups at 24 hours. In addition, no difference was seen in the surgeon's subjective intraoperative assessment of hemostasis after administration of either study drug. Furthermore, after study drug administration protamine was associated with a deleterious effect on subsequent intraoperative blood loss (318 +/- 33 ml vs 195 +/- 18 ml, p < 0.05). CONCLUSIONS: Although protamine effectively reverses heparin anticoagulation, its routine use after elective peripheral vascular surgical reconstruction does not appear to provide any clinical benefit.

Aged↗
PubMed1995

The direct and interactive effects of phosphodiesterase inhibition and beta-adrenergic stimulation on myocyte contractile function after hypothermic cardioplegic arrest.

The direct and interactive effects of phosphodiesterase inhibition (PDEI) and beta-adrenergic receptor (beta AR) stimulation on isolated myocyte contractile function were examined after hypothermic, hyperkalemic, cardioplegic arrest (HHCA) and under normothermic conditions. Left ventricular (LV) myocytes were isolated from porcine hearts and myocyte contractile function was measured under normothermic conditions (37 degrees C in standard media) and after HHCA (2 h at 4 degrees C in Ringer's solution with 24 mEq KCl) with subsequent rewarming. Myocytes were then randomly assigned to treatment with the beta AR agonist isoproterenol (25 nM), the phosphodiesterase inhibitor amrinone (50 microM), or a combination of these compounds and contractile function measurements repeated. Baseline myocyte contractile function was reduced by 32% after HHCA. Isoproternol alone increased myocyte contractile function more than 100% under both normothermic conditions and after HHCA, whereas amrinone alone significantly (60%) improved myocyte contractile function only after HHCA. Amrinone preincubation followed by isoproterenol improved contractile function after HHCA to a greater extent than all other treatment protocols. In contrast, combination treatment under normothermic conditions did not augment myocyte contractile function relative to isoproterenol alone. These findings suggest that amrinone has differential effects on contractile processes. Moreover, the marked improvement of contractile function after HHCA with PDEI pretreatment followed by beta AR stimulation may have implications in treatment strategies for improving myocardial function after cardiopulmonary bypass and provide insight into contractile dysfunction after HHCA.

Adrenergic beta-Agonists↗
PubMed1995

Myocyte contractile responsiveness after hypothermic, hyperkalemic cardioplegic arrest. Disparity between exogenous calcium and beta-adrenergic stimulation.

BACKGROUND: Acute left ventricular dysfunction is commonly encountered after hypothermic, hyperkalemic cardioplegic arrest (HHCA) and often requires inotropic intervention for successful separation from cardiopulmonary bypass. However, the basic mechanisms involved in depressed left ventricular function and the cellular basis for the differential effects of inotropic drugs after HHCA are unknown. Accordingly, the goal of this study was to determine the effects of calcium (Ca2+) and beta-adrenergic receptor agonists (beta AR) stimulation on isolated myocyte contractile function after HHCA. METHODS: Myocytes were isolated from the left ventricle of nine pigs and randomly assigned to one of the following treatment groups: (1) normothermic, control: incubation in oxygenated cell culture media for 2 h at 37 degrees C; and (2) cardioplegia: incubation in 4 degrees C crystalloid cardioplegia for 2 h, followed by rewarming. Steady-state myocyte contractile function was measured after pulse stimulation at baseline, in the presence of extracellular Ca2+ (3-10 mM), and in the presence of the beta AR agonist isoproterenol (2-100 nM). Myocyte profile surface area was measured for both normothermic myocytes and myocytes after HHCA. In a separate set of experiments, myocyte contractile function also was documented after 2 h of hypoxic conditions with both normothermic incubation and HHCA, in the presence and absence of beta AR stimulation. RESULTS: Baseline myocyte contractile function was significantly less in the cardioplegia group compared to control. Extracellular Ca2+ produced a dose-dependent significant increase in myocyte contractile function in the normothermic control group, whereas increased extracellular Ca2+ only minimally increased myocyte contractile function in the cardioplegia group. A dose-dependent, significant increase in myocyte contractile function was observed in both groups after beta AR stimulation by isoproterenol; however, myocyte contractile function in the cardioplegia group was decreased compared to the control group. Hypoxia under normothermic conditions significantly reduced myocyte contractile function, myocyte relaxation, and beta-adrenergic responsiveness. Hypoxia in combination with cardioplegic arrest compounded the negative effects on contractile processes but did not further impair beta-adrenergic responsiveness. Myocyte profile surface area was significantly increased after HHCA. CONCLUSIONS: The minimal improvement in myocyte contractile function after HHCA with increased extracellular Ca2+ suggests that Ca2+ depletion is not the primary mechanism for depressed myocyte contractility after HHCA. On the other hand, because beta AR administration improved myocyte contractile function after HHCA, the cellular basis for the effects of beta AR stimulation after HHCA is probably not increased myocyte Ca2+ but rather alternative mechanisms, such as changes in myofilament sensitivity to Ca2+. These results also suggest that the abnormalities in left ventricular function after HHCA result from the direct effects of hyperkalemic induced electromechanical uncoupling as well as relative hypoxic conditions.

Adrenergic beta-Agonists↗
PubMed1994

Postoperative hyperthermia in a patient having cortical brain resection.

When a profound fever occurs in a surgical patient, clinicians usually start thinking about the malignant hyperthermia syndrome. Simple consideration of the clinical situation, the patient's medical history, and a few rapid laboratory assessments are enough to direct appropriate treatment.

Adolescent↗
PubMed1994

Postoperative analgesia after major shoulder surgery with interscalene brachial plexus blockade: etidocaine versus bupivacaine.

Postoperative pain is commonly treated with significant doses of narcotics, occasionally resulting in side effects including nausea, pruritus, and respiratory depression. One potential advantage of regional anesthesia is profound postoperative analgesia that reduces exposure to potent narcotics. To evaluate the efficacy of two long-acting local anesthetics, bupivacaine and etidocaine, in providing pain relief after major shoulder surgery, we randomized 20 patients to receive either bupivacaine or etidocaine for brachial plexus block as the primary anesthetic for shoulder surgery. Surgeons, patients, and the acute pain service were blinded as to drug selection. After the patient was sedated, an interscalene block was placed with the use of a nerve stimulator to facilitate proper needle placement. Forty milliliters of either 0.5% bupivacaine or 0.75% etidocaine containing 5 micrograms/mL epinephrine was injected into the brachial plexus sheath. An additional 8 mL of local anesthetic was administered for superficial cervical plexus blockade. Intraoperative sedation was accomplished with an intravenous infusion of methohexital as needed. After surgery, patients received a standard patient-controlled analgesia protocol providing incremental doses of morphine. The degree of postoperative analgesia resulting from residual local anesthetic effect was expressed as the time until first morphine requirement and the total dose of morphine required during the first 24 hours postoperatively. We found no statistically significant intergroup differences either in time of initial use of morphine or in the total dose of morphine required in the first 24 hours. Both etidocaine and bupivacaine provide prolonged analgesia after major shoulder surgery when injected into the brachial plexus. Bupivacaine, however, possesses significant cardiotoxicity and has a relatively delayed onset in peripheral neural blockade. Etidocaine is less cardiotoxic and also has a more rapid onset of effect. Thus etidocaine may be a preferable agent for interscalene block for major shoulder surgery.

Aged↗
PubMed1993

Assessment of right ventricular contractile performance after pulmonary resection.

Right ventricular (RV) performance deteriorates after pulmonary resection. The mechanism remains unclear and could be related to changes in loading conditions or contractility. To assess the role of alteration in RV contractility, we developed a simple and reliable means to measure RV contractile performance in adult patients. Using thermodilution methods and rapid volume infusion in the preoperative setting, the relationship between RV stroke work (RVSWI) and end-diastolic volume (RVEDVI), termed the preload recruitable stroke work relation, was plotted using linear regression. Experimental studies have demonstrated that the preload recruitable stroke work relation is a linear and load-insensitive index of RV contractile performance. Our study confirms this finding in adult patients: RVSWI = 0.33 (RVEDVI) - 20.4 (n = 108; r = 0.94; p < 0.01). Examination of RV pump function and hemodynamic parameters in the early postresection period (up to 24 hours postoperatively) revealed significant changes in loading conditions, but isochronal RVEDVI and RVSWI values were within the confidence limits of the preload recruitable stroke work relation. Thus, depressed RV contractility does not appear to play a predominant role in this early postoperative period. Further study in a larger patient population will be required to verify this observation and to assess RV performance beyond 24 hours after resection.

Female↗
PubMed1993

A comparison of wound instillation and caudal block for analgesia following pediatric inguinal herniorrhaphy.

Regional analgesia, in a variety of forms, has been shown to afford effective postoperative pain relief after pediatric inguinal hernia repair. This study compares the efficacy of wound instillation with 0.25% bupivacaine (n = 20), caudal block with 0.25% bupivacaine (n = 35), and a control group (n = 15). Outcome parameters examined include total operating room time, time to extubation, postoperative objective pain scales, and requirement for supplemental analgesics. Patients who received caudal blocks had significantly decreased emergence times (P < .002), exhibited fewer pain-related behaviors postoperatively (P < .0025), and required less narcotic to maintain normal hemodynamics (P < .05). Operating room time was not statistically different between the three groups. The use of perioperative analgesic blocks resulted in quicker awakening, a more comfortable postoperative course, and potentially earlier discharge from same-day surgery.

Anesthesia, Local↗
PubMed1993

Clonidine improves perioperative myocardial ischemia, reduces anesthetic requirement, and alters hemodynamic parameters in patients undergoing coronary artery bypass surgery.

The purpose of this study was to determine if clonidine reduces myocardial ischemia or alters anesthetic requirement and perioperative hemodynamic parameters during coronary artery bypass grafting (CABG) surgery. Forty-three patients were randomized in a prospective, double-blind fashion to receive either clonidine (5 micrograms/kg) or placebo. Anesthetic induction and maintenance was accomplished with intravenous sufentanil-midazolam (S-M) in a 1:20 ratio; up to 1.0% enflurane was added during surgery when repeated boluses of S-M failed to maintain the blood pressure within 20% of preinduction values. Continuous ST segment analysis of leads II and V5 was performed throughout surgery with maximal ST segment deflection from baseline recorded every 5 minutes. Catecholamine levels were measured intermittently throughout the perioperative period and myocardial lactate use or excretion was determined just prior to cardiopulmonary bypass (CPB) and at 1, 5, 10, 30, and 60 minutes after release of the aortic cross-clamp. Patients who received clonidine required significantly less sufentanil for their surgical procedure (11.82 +/- 0.66 micrograms/kg v 14.55 +/- 0.90 micrograms/kg, P < 0.05) and also needed less enflurane for blood pressure control, particularly during CPB (P < 0.05). Baseline hemodynamic parameters were similar for both groups prior to induction. In the period between anesthetic induction and the initiation of CPB, patients treated with clonidine had a significantly slower heart rate (HR) (P < 0.01), a lower cardiac output (CO) (P < 0.05), and transiently higher systemic vascular resistance (SVR) (P < 0.05) than placebo-treated patients. Immediately after CPB, patients receiving clonidine continued to have a significantly lower CO (P < 0.01) and a higher SVR (P < 0.01) than placebo-treated patients. Clonidine treatment significantly increased the percentage of patients who required pacing after CPB (P < 0.05). In the intensive care unit, clonidine-treated patients displayed a persistently increased requirement for pacing (P < 0.01), decreased systolic blood pressures, and reduced sodium nitroprusside requirements relative to patients treated with placebo. Epinephrine and norepinephrine levels were lower in clonidine-treated patients throughout the perioperative procedure with significant differences noted immediately following sternotomy and release of the aortic cross-clamp (P < 0.05). Critical ST segment depression was significantly less in clonidine-treated patients for the period from sternotomy until application of the aortic cross-clamp (P < 0.01). Following CPB, absolute deviation of ST segments from isoelectric baseline was significantly less in the clonidine-treated group (P < 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia, Intravenous↗
PubMed1993

Selection of anesthesiology residents.

BACKGROUND: CARCS (computer-assisted resident candidate selection) is a database application developed in 1983 at the Department of Anesthesiology of the Medical University of South Carolina to deal with the greatly increased quantity of applicant information. This article relates a representative sample of CARCS data to the process of selecting residents in general. METHOD AND RESULTS: CARCS files were analyzed for 1985-86, 1986-87, 1990-91, and 1991-92, and data for each year were derived as simple averages and percentages for two groups: (1) the entire pool of residency applicants (approximately 200 per year) and (2) the eight residency candidates per year who actually matched with the program through the National Resident Matching Program, Analyses showed that the standardized test scores, grades, and class ranks of the matched candidates were not significantly higher than those of the applicants; however, the matched candidates' scores for letters of reference and for interviews were consistently higher than those for the applicant pool. CONCLUSIONS: The results support the view of medical educators that the traditional academic criteria are not sufficiently predictive of clinical performance or interpersonal skills. Research relating residents' performances to personality, learning style, and other neuropsychological factors may provide needed alternatives to knowledge testing by developing combined cognitive-noncognitive profiles. The anesthesiology clerkship experience is now almost universal among applicants and could be structured to provide pertinent information about potential residents through direct observation as well as behavioral testing.

Anesthesiology↗
PubMed1993

Cerebral monitoring during implantation of automatic internal cardiac defibrillators.

Implantation of automatic internal cardiac defibrillators (AICD) for management of arrhythmias necessitates the induction of ventricular fibrillation (VF) to test the device adequately. The profound hypotension associated with induced arrhythmia and subsequent circulatory arrest may result in cerebral ischemia. To characterize cerebral ischemia, we used a five-lead Lifescan brain activity monitor to examine changes in cerebral activity in 10 patients having AICD placement. The duration of hypotension, as defined by a mean arterial pressure (MAP) < 50 mm Hg, was recorded, and the corresponding changes in brain activity were evaluated during 51 episodes of circulatory arrest. The number of episodes for each patient ranged from 2 to 14. The average duration of hypotension per episode was 26.2 seconds, with a range of 8 to 67 seconds. Brain activity changes characteristic of cerebral ischemia occurred in 46 of the 51 events (90%). Cerebral ischemia did not occur when the duration of hypotension was less than 16 seconds (5 episodes). The duration of cerebral ischemia ranged from 50 to 279 seconds (average 84.9 seconds) and did not correlate with the duration of hypotension or the order of the episodes in the testing sequence. These findings suggest that reevaluation of standard monitoring practice for AICD implantation may be warranted.

Brain Ischemia↗
PubMed1993

Acquired methemoglobinemia from multiple oxidants.

Phenazopyridine has been associated with methemoglobinemia in patients who have received an overdose, have decreased renal function, or are discovered to be unusually susceptible to the drug (ie, they may have an undetected NADH methemoglobin reductase deficiency). The case we have presented is unusual in that normal doses of phenazopyridine were given, no renal dysfunction was evident, and our patient had previously been given this drug without complication. Methemoglobinemia appeared to be the result of metabolic overload by multiple oxidants (phenazopyridine and lidocaine) of the normal reductase pathways in the erythrocytes. We saw no evidence to indicate that bupivacaine contributed to its development. Enzyme pathway changes induced by chemotherapy should be considered, though few studies have linked alterations of enzyme levels and pathways with chemotherapy and malignancy.

Administration, Topical↗
PubMed1993

Identification of patients at risk for excessive blood loss during coronary artery bypass surgery: thromboelastography versus coagulation screen.

In light of the potential morbidity associated with transfusion of blood products, a reliable preoperative screening test to identify cardiothoracic surgical patients who are at potential risk for increased intraoperative blood loss would be useful. Accordingly, we examined the efficacy of a variety of coagulation tests to predict intraoperative blood loss in 60 patients presenting for coronary artery bypass surgery (CABG). A complete coagulation screen, activated clotting time (ACT), and thromboelastograph (TEG) were performed before surgery. Intraoperative blood loss was determined by weighing sponges and measuring the quantity of blood in suction canisters. The duration of cardiopulmonary bypass was 100 +/- 4 min, and total surgery time was 5.0 +/- 0.1 h. Total crystalloid and colloid requirements were 5.5 +/- 0.2 and 1.4 +/- 0.1 L. Forty-eight percent of the patients required blood with an average requirement of 2.5 +/- 0.5 units. Total intraoperative blood loss averaged 1590 +/- 95 mL with a range from 640 to 3928 mL. Using multiple linear regression, all coagulation and TEG variables were used to model perioperative blood loss. Results showed that all components of the TEG failed to predict blood loss (r < 0.25, P > 0.78). However, three components of the routine coagulation assay, including bleeding time, prothrombin time, and platelet count could be modeled to predict perioperative blood loss (r = 0.75, P < 0.05). Although TEG has been shown to have potential in identifying postcardiopulmonary bypass coagulopathies, these results suggest that it does not appear to be useful in determining the coagulation status of CABG patients preoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗