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Biomedical subjects

D Garner

Publications and source records attributed to D Garner.

At least 19 recordsLinked to original sources
PubMed1995

Accurate coronary calcium phosphate mass measurements from electron beam computed tomograms.

Precipitates of calcium phosphate in coronary arteries always indicate the presence of atherosclerosis. The mass of these precipitates is related to the severity of atherosclerosis. To determine the accuracy of electron beam computed tomographic (CT) mass estimates, we imaged 21 human hearts inside an anthropomorphic chest phantom using an Imatron C-100 electron beam CT scanner (Imatron, San Francisco, CA). We then incinerated the 63 imaged coronary arteries and weighed the mineral ash. We calculated the mass estimates from the images using an algorithm derived from a model that assumes simple radiographic properties of the coronary arteries. We also calculated the currently used coronary calcium score for each artery. Although both the mass estimates and the scores correlated with the actual mass of the incinerated specimens (r = .97 and r = .93), the correlation with the mass estimates was better (P = .02; William's test). The regression equation relating the actual mass to the mass estimates was y = 1.37 x + 14, indicating that the CT mass estimates consistently underestimate actual coronary calcium phosphate mass. We conclude that relative mass estimates using electron beam CT scanning are accurate and that both these and the currently employed calcium scores reflect the actual mass of precipitated calcium phosphate in diseased coronary arteries.

Algorithms↗
PubMed1992

Functional significance of post-myocardial infarction left ventricular hypertrophy: a beneficial response.

Hypertrophy of noninfarcted myocardium occurs as a chronic response to myocardial infarction, but no previous study has related the changes in wall thickness to serial changes in left ventricular function. Thus the functional significance of postinfarction hypertrophy is unknown. The purpose of this study was to determine the relationship between the development of postinfarction hypertrophy and the resting left ventricular ejection fraction measured by two-dimensional echocardiography. After occlusion of the proximal left anterior descending coronary artery in 11 dogs, the ejection fraction fell acutely (0.63 +/- 0.08 to 0.33 +/- 0.10, p less than 0.001) and rose at 3.5 months to 0.62 +/- 0.12. End-diastolic thickness of the noninfarcted left ventricle increased (11 +/- 1.0 mm to 13 +/- 1.4 mm, p less than 0.01) as did left ventricular mass (101 +/- 18 gm to 134 +/- 21 gm, p less than 0.0001). Restoration of the ejection fraction toward the baseline value correlated with the increases in left ventricular mass (r = 0.79, p = 0.007) and wall thickness (r = 0.71, p = 0.025). Hypertrophy of the noninfarcted myocardium correlated with the magnitude and approximately paralleled the time course of the improvement in the ejection fraction and therefore may have had a beneficial effect on resting left ventricular function as a chronic adaptation to myocardial infarction.

Animals↗
PubMed1991

Pharmacologic interventions after an LD50 cocaine insult in a chronically instrumented rat model: are beta-blockers contraindicated?

STUDY PURPOSE: To evaluate drug management of acute cocaine toxicity in a new animal model. The study null hypothesis was that no drug would affect outcome compared with a placebo control. MODEL: Chronically instrumented, conscious, unrestrained rats subjected to an LD50 dose (1.4 mg/100 g body wt) of IV cocaine. METHODS: Rapid injection of IV cocaine by IV vascular access port followed by injection of therapeutic study drugs. Outcome (survival vs death) with drug treatment was compared with a placebo group. PHARMACOLOGIC INTERVENTIONS: Normal saline placebo (0.2 mL/100 g), diazepam (0.5 mg/100 g), chlorpromazine (0.2 mg/100 g), propranolol (1.0 mg/100 g), labetalol (3.0 mg/100 g), or verapamil (0.1 mg/100 g) was given. There were ten rats in each treatment group. Allocation to treatment groups was nonrandomized. STATISTICAL METHODS: Fisher's exact test. RESULTS: IV injection of cocaine was followed by tonic-clonic seizure activity in all treatment groups. No study drug significantly improved survival compared with the placebo group. However, no animal treated with propranolol survived (P less than .05 vs saline control), and only one of ten animals treated with labetalol survived (P = .14 vs placebo group). CONCLUSION: In this conscious animal model subjected to an LD50 IV cocaine insult, chlorpromazine and diazepam, previously shown to be of value in other animal models, had no effect on survival. Verapamil also did not affect outcome. Outcome was adversely affected by treatment with beta-blocking agents.

Adrenergic beta-Antagonists↗
PubMed1991

An innovative program for multihandicapped deaf students using the FSSI.

Teachers in public schools now have more students with more severe disabilities than they did in the past. Unfortunately, efforts to provide them with a quality education have been hampered by a lack of focused instructional planning. This article describes an innovative program developed for deaf multihandicapped students that has created an integrated focus for instruction. The organizing framework for the program incorporates the Functional Skills Screening Inventory, a domain referenced assessment of living and working skills. This structured approach enables teachers to identify current functional levels, develop meaningful short- and long-term objectives, and monitor student progress throughout their educational programs. It also facilitates long-range planning and evaluation of the instructional program on an ongoing basis.

Adolescent↗
PubMed1989

Verapamil induced ventricular hypertrophy in conscious dogs.

Verapamil is used clinically in the treatment of various cardiac diseases including hypertrophic cardiomyopathy. Its long term effects on ventricular mass are not well known. In 11 conscious dogs heart rate, aortic and left ventricular pressures, cardiac output, a methoxamine induced stress ventricular function test and left ventriculography were performed. These variables were measured prior to and following a mean 7.2 month infusion of verapamil at 0.005 or 0.01 mg.kg-1.min-1 using a subcutaneously implanted pump. Resting haemodynamic variables and left ventricular ejection fraction [60(SD 6) v 55(6)%] were unchanged between baseline and chronic verapamil studies, but the slope of the methoxamine induced stress ventricular function test decreased from 3.9(0.8) to 2.1 (1.3). After verapamil was discontinued the mean slope of the stress ventricular function test returned to the baseline 4.0(1.7). Total ventricular weight increased 22% from 176.1(17.5) g.m-2 in controls to 215.6(29.5) g.m-2 (p less than 0.01) in the verapamil animals. The right ventricular weight increased 25% from 46(5.9) to 57.6(9.1) g.m-2 (p less than 0.01); the septum weight increased 26% from 42.5(4.1) to 53.7(7.2) g.m-2 (p less than 0.001); and the left ventricular free wall weight increased 19% from 87.4(9.8) to 103.9(15.7) g.m-2 (p less than 0.01). The increase in ventricular weights was not due to fibrosis or oedema since hydroxyproline contents and wet/dry ratios were not increased. In conclusion, a chronic infusion of verapamil in conscious dogs caused no change in resting haemodynamic variables but produced reversible depression of stress ventricular function and biventricular and septal hypertrophy.

Animals↗
PubMed1988

Identification of inflammatory cells in bovine milk by flow cytometry.

Cells recovered from normal or mastitic bovine milk were examined by flow cytometry. All milk samples contained particulate material that was heterogeneous in size and that produced a right-angle light-scatter signal equal to or greater than that produced by human or bovine neutrophils. Although this material labeled with Hoechst 33342, it produced fluorescence intensities below that of intact bovine cells, suggesting that it consisted of cell fragments. Mastitic milk additionally contained other populations of cells that were poorly resolved from the normal particulate material by size (electronic volume sensor) and right-angle light scatter. In order to improve this resolution, the milk cells were incubated with carboxydimethylfluorescein diacetate (CMFDA) to label intact cells. When milk samples labeled with CMFDA were examined by dual-parameter analysis using green fluorescence and right-angle light scatter, five or more populations of cells could be identified in mastitic milk. These populations included intact and degenerate neutrophils, lymphocytes, including both small and activated cells, monocytes, and large activated macrophages containing many vacuoles and phagocytosed particles. Using this procedure, all the animals in the University of Nevada-Reno Holstein dairy herd were tested once a month for 6 months. In addition, individual animals with mastitis were examined one or more times each day during the course of the inflammatory process. In the routine screening, the flow cytometric examination detected mastitis before overt symptoms developed. In cows identified to have mastitis, the flow cytometric examination provided prognostic information regarding the success of treatments.

Animals↗
PubMed1988

Predictive value of the ECG in determining cardiac resuscitation outcome in a canine model of postcountershock electromechanical dissociation after prolonged ventricular fibrillation.

The purpose of our study was to determine if the surface ECG in postcountershock electromechanical dissociation (EMD) is of value in predicting return of effective myocardial contractile function during CPR. Nine dogs were subjected to five minutes of ventricular fibrillation (VF) without CPR followed by countershock and closed-chest CPR. Intravascular pressures, coronary perfusion pressure, and coronary sinus flow were measured during conventional CPR. After countershock, and before CPR, the frequencies of the following ECG variables were assessed: the presence or absence of P waves, an abnormal QRS duration (greater than 100 ms), a prolonged QTc (greater than 430 ms), and a bradyarrhythmia (QRS rate less than 60/min). Twenty-three episodes of postcountershock EMD were studied. Countershock after prolonged VF without CPR was always followed by EMD. The mean values of ECG variables were not significantly different (P greater than .05) between animals successfully resuscitated and those that were not. The sensitivity, specificity, and predictive values of individual ECG variables in estimating successful cardiac resuscitation exhibited a wide range of values. The QTc had the highest sensitivity (1.00), but the lowest specificity (0.08). The presence or absence of P waves had the highest specificity (0.62), but a sensitivity of only 0.40. QRS rate had the greatest positive predictive value (0.48) but a negative predictive value of 0.46 for successful cardiac resuscitation. The QTc had the greatest negative predictive value (1.00) but a positive predictive value of only 0.45. Multiple regression analysis using the study ECG variables as independent variables demonstrated that ECG variables were not related to outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

A new technique for producing myocardial infarction using coronary artery balloon occlusion.

Many techniques for producing myocardial infarction have required the potential physiological altering effects of a thoracotomy. Previous techniques have used the variable and therefore unpredictable effects of coronary artery injection of occlusive agents, intravascular plugs, and externalized coronary balloon catheters. Previous investigators have reported a survival rate of 50-70%. In the present study a new closed chest dog technique was used in which a catheter with an inflatable detachable balloon was placed in the aorta via the carotid artery. The catheter could be readily lodged into any portion of the right, left anterior, or circumflex coronary artery. The proximal left anterior descending and circumflex arteries were occluded in 15 dogs. This new coronary artery balloon occlusion technique may be used to produce a chronic myocardial infarction with a high survival rate of 90% through the use of short acting anaesthesia and rapid reversal of the effect of morphine with naloxone hydrochloride. The rapid recovery of the dog permits earlier study of haemodynamic variables and arrhythmia due to myocardial infarction in the best physiological state.

Animals↗
PubMed1987

Living with cystic fibrosis: patient, family, and physician realities.

The challenge for patient, family, and healthcare professionals alike is to separate the disease's insidiousness from the potential the patient and family have to enjoy life within the patient's abbreviated life span. We must emphasize that most patients with CF and their families do make a successful psychological adjustment. Simultaneously, parents must fulfill the varied physical and psychological needs of the child. A young adult patient with CF summarizes the patient's task: "Projecting a life goal, living it, having the goal altered by luck and by fate, accomplishing that goal, and then reflecting on what has been done. That is life. That is a life compressed for us; CF is myopic. We cannot look through the long vista of life. That is disappointing, frustrating, and cursed at. We can live now. We can do the best we can. Set goals that fit on our playing field and accomplish them." An emotionally adjusted family makes the patient's task possible. Achieving the goal of adequate adjustment also depends on the physician's having the medical expertise to manage this complex multisystem illness and the ability to make the medical knowledge comprehensible for patient and family.

Age Factors↗
PubMed1987

Postcountershock pulseless rhythms: hemodynamic effects of glucagon in a canine model.

Defibrillation after prolonged ventricular fibrillation (VF) is frequently followed by asystole or electromechanical dissociation (EMD) which are usually fatal. We studied the effects of glucagon, a known inotropic and chronotropic agent, during 19 episodes of postcountershock asystole/EMD in nine dogs. Systolic and diastolic aortic (Ao), left ventricular, pulmonary arterial, and right atrial (RA) pressures were recorded as was the instantaneous Ao-RA difference (coronary perfusion pressure) and coronary sinus blood flow (CSF) during closed-chest CPR. VF was induced electrically; 2 min later, a 400-J transthoracic shock was given. Countershock was always followed by asystole (n = 12) or EMD (n = 7). Conventional closed-chest CPR with a mechanical device was begun 30 to 60 sec after countershock and continued for 2 to 3 min. If a perfusing rhythm did not occur, glucagon (1 mg) was given iv and CPR continued for 2 to 3 min more. Glucagon had no significant effect on intravascular pressures, the coronary perfusion gradient, or CSF when compared to CPR alone. However, in 14 or 19 postcountershock episodes unresponsive to CPR alone, glucagon restored effective spontaneous circulation, i.e., successful cardiac resuscitation, due to its effects on the intrinsic pacemaker discharge rate. Glucagon has been previously shown to stimulate myocardial adenyl cyclase via nonadrenergic mechanisms. We conclude that when postcountershock asystole/EMD occurs, glucagon has a direct and favorable effect on cardiac resuscitation outcome due to its effects on pacemaker discharge rate which is not mediated by changes in myocardial blood flow or coronary perfusion pressure.

Animals↗
PubMed1986

Euthanasia of rabbits by intravenous administration of ketamine.

Six New Zealand White rabbits (5 females and 1 male) were anesthetized with a combination of xylazine (4.3 mg/kg of body weight) and ketamine (29.1 mg/kg) administered IM. The rabbits were then attached to instruments that continuously monitored blood pressure and electrocardiographic and electroencephalographic values. Each rabbit was then administered a lethal dose of ketamine (600 mg, IV). Within 90 seconds after injection of the ketamine, brain death developed and the heart rate and blood pressure decreased greatly. Circulatory activity persisted for a maximum of 240 seconds. This method of euthanasia did not result in histopathologic changes in tissue specimens evaluated. Although death occurred rapidly, extensive muscle contractions made euthanasia of rabbits with ketamine aesthetically unacceptable. Therefore, this method would not be a suitable means of euthanasia for routine use in rabbits.

Animals↗
PubMed1986

Postcountershock pulseless rhythms: response to CPR, artificial cardiac pacing, and adrenergic agonists.

Clinically, countershock of ventricular fibrillation (VF) may result in asystole or a pulseless rhythm in more than 50% of attempts. We conducted a study to assess the effects of immediate artificial pacing, CPR, and adrenergic drug therapy in the management of postcountershock pulseless rhythms. Thirty-four episodes of VF followed by countershock were studied in eight anesthetized dogs. Transducer-tipped catheters were positioned in the ascending aorta (Ao) and right atrium (RA). A bipolar pacing catheter was advanced to the apex of the right ventricle and a catheter for measurement of coronary sinus blood flow (CSQ) (continuous thermodilution technique) was positioned in the coronary sinus. VF was induced electrically and a countershock at 400 J was given two minutes later; CPR was not performed during VF episodes. Countershock was followed by asystole or a pulseless rhythm in all animals. Immediate endocardial pacing (0.1 to 5 mA) of bradyarrhythmias produced electrical capture but did not result in arterial pressure pulses in any animal. After pacing, CPR was performed for two minutes or until restoration of spontaneous circulation (ROSC). During CPR, the diastolic coronary perfusion gradient (Ao-RA) was 20 +/- 7 mm Hg (mean +/- SD) and CSQ was 14 +/- 7 mL/min/100 g (53% +/- 43% of control). ROSC followed CPR of less than two minutes duration in 24% of VF study episodes. If ROSC did not follow two minutes of CPR, 1 mg epinephrine, or 50 micrograms or 100 micrograms isoproterenol was given IV.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Endocardial and transcutaneous cardiac pacing, calcium chloride, and epinephrine in postcountershock asystole and bradycardias.

Clinically, asystole or a bradyarrhythmia may follow countershock of ventricular fibrillation (VF) in up to 40% of attempts. This study evaluated the effects of artificial cardiac pacing, calcium chloride (CaCl2), and epinephrine in postcountershock asystole/bradycardia. Micromanometer catheters were positioned in the aorta (Ao) and right atrium (RA) of ten dogs and VF induced by right ventricular (RV) stimulation. After 2 min of VF, a 400-J countershock was given. In six animals, asystole or a pulseless bradyarrhythmia followed one countershock. In four animals, up to three countershocks were needed to terminate VF and resulted in asystole or a pulseless bradyarrhythmia. Thirty seconds after termination of VF, cardiac pacing was begun in all animals using conventional RV endocardial pacing (RVEP) or a transcutaneous transthoracic pacing (TTP) technique. RVEP and TTP produced ventricular depolarizations, but electrical capture was never associated with Ao pressure fluctuations. After 2 min of pacing, CaCl2 was given and chest compressions and artificial ventilations (CPR) initiated. CaCl2 had no effect on CPR pressures. After 2 min of CPR, RVEP and TTP were again studied; capture without Ao pressure fluctuations was seen in all animals. Epinephrine was then given and CPR reinstituted. Epinephrine produced a significant increase in CPR Ao systolic pressure (58 +/- 13 to 84 +/- 24 mm Hg, p less than .001) and end-diastolic coronary perfusion pressure (Ao-RA) (9 +/- 4 to 34 +/- 8 mm Hg, p less than .001). Within 94 +/- 53 sec after epinephrine, spontaneous circulation was restored in eight animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

New implanted chronic catheter device for determining blood pressure and cardiac output in conscious dog.

The Vascular-Access-Port (VAP) is a subcutaneous implantable device designed for repeated venous blood sampling in humans. With slight modifications the device has been used in the arterial and venous systems of dogs. This device allows for chronic repeated arterial blood pressure monitoring, monitoring of cardiac outputs, and blood sampling in conscious dogs. Infection, vascular thrombosis, and catheter extraction have not occurred. This modified VAP has been used for 6 mo and in 25 dogs to date without any failure to determine arterial blood pressure and cardiac output.

Animals↗
PubMed1984

External non-invasive cardiac pacing: a comparative hemodynamic study of two techniques with conventional endocardial pacing.

Out-of-hospital therapy for cardiac arrest due to bradyarrhythmias or asystole is pharmacologic and the outcome is uniformly dismal. Optimal therapy for the latter disturbances may be artificial cardiac pacing, but conventional invasive pacing techniques are not employed or are of limited value in the out-of-hospital and emergency department setting. This investigation compared the hemodynamic effects of two techniques of non-invasive external pacing: 1) transcutaneous transthoracic pacing (TTP) and 2) tongue-to-epigastrium pacing (TEP), with conventional transvenous right ventricular endocardial pacing (RVEP) in a closed-chest, chronic heart block canine model. All techniques significantly increased (p less than .001) cardiac output (CO). However, CO and mean arterial pressure (MAP) measured during external pacing with either non-invasive technique were significantly greater than that during RVEP (p less than .001). TEP produced vigorous skeletal muscle stimulation and, in the canine model, it produced contraction resulting in impaired ventilation, hypoxemia, and a decrease in systemic vascular resistance. TTP in this model resulted in improved MAP and CO when compared with control and RVEP values and did not affect arterial or mixed venous blood gas values. Thus, this study demonstrates that noninvasive TTP is comparable to RVEP in its hemodynamic effects. TTP may offer definitive non-invasive therapy for a subset of victims of out-of-hospital cardiac arrest.

Animals↗