Distribution of left ventricular coronary blood flow in the fibrillating, empty beating, and diastolic arrested heart.
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Animals↗
Biomedical subjects
D D Buss
Publications and source records attributed to D D Buss.
Hypoventilation in ponies after carotid body denervation.
Seven ponies were subjected to carotid body denervation (CD) and two ponies were sham operated (S). Measurement of arterial blood gases and arterial blood and cerebrospinal fluid (CSF) acid-base balance were made prior to and 1,2,4,9, and 17 wks after surgery in unanesthetized animals. Resting ventilation and ventilatory responsiveness to hypoxia and NaCN infusion were assessed prior to and 2,9, and 17 wks after surgery. Alveolar hypoventilation in the CD ponies was marked 1-2 wk after surgery when VE and VA were reduced 40% and 10%, respectively, from control and PaCO2 was 12-15 mmHg above control. However, the effect was not nearly as great 4, 9, and 17 wk after surgery when the PaCO2 stabilized at approximately 6 mmHg above control PaCO2. Arterial blood pH was normal in the hypercapnic CD ponies, but CSF pH remained acid relative to normal throughout the 17-wk period. Changes in ventilatory responsiveness to hypoxia and NaCN tended to parallel changes in resting ventilation. These findings suggest: 1) the carotid bodies are essential in ponies to maintain normal ventilation: 2) in CD ponies peripheral chemosensitivity is partially regained at some unestablished locus; and 3) pH compensating mechanisms in chronically hypercapnic ponies function relatively better in blood than in CSF.
Acid-Base Equilibrium↗
Ventilatory control in peripheral chemoreceptor-denervated ponies during chronic hypoxemia.
The present study was designed to provide further insight into the role of the carotid and aortic chemoreceptors in ventilatory (VE) acclimatization during sojourn at altitude. Measurements were made: 1) on 10 ponies near sea level (SL, 740 Torr) under normal conditions, 2) on 6 of these at SL following chemoreceptor denervation (CD), and 3) subsequently on all 10 during 4 days of hypobaric hypoxia (PaO2 = 40-47 Torr). CD resulteo in hypoventilation at SL (deltaPaCO2 = d8 Torr, P less than 0.05), and it prevented hyperventilation normally observed with injection of NaCN and acute exposure to hypoxia (less than 1 h). In contrast, hyperventilation was evident in normal ponies during acute hypoxia (deltaPaCO2 = -6.7 Torr). Ventilation increased in both groups between the 2nd and 8th h of hypoxia (deltaPaCO2 from 1 h = -4 Torr, P less than 0.05). This change, a common characteristic of acclimatization, persisted throughout 4 days of hypoxia in the normal ponies. However, in the CD ponies this change was evident consistently only through the 12th h and after the 44 h hyperventilation was no longer evident. We conclude that the peripheral chemoreceptors are essential in ponies for normal VE acclimatization to this degree of hypoxemia. Two additional findings in CD ponies suggest the presence of a CNS inhibitory influence on the VE control center during chronic hypoxemia. First, acute hyperoxygenation on the 4th day of hypoxemia induced hyperventilation (deltaPaCO2 = -5 Torr, P less than 0.05). Second, again on the 4th day and during hyperoxygenation, VE responsiveness to CO2 and doxapram HCl was greater than at sea level.
Acclimatization↗
Cerebrospinal fluid alkalosis during high-altitude sojourn in unanesthetized ponies.
Unanesthetized adult female ponies were studied near sea level (250 m) and during sojourns to 3400 m (N=6) and 4300 m (N=7) altitude. The pH, PCO2, and PO2 of arterial blood and pH and PCO2 of cerebrospinal fluid (CSF) were measured under conditions of acute (1 hr) and chronic (1-45 days) hypoxia. Cerebrospinal fluid was sampled from the cisterna magna of the awake pony and arterial blood withdrawn from an indwelling arterial catheter. In both groups of animals, PaCO2 decreased slightly after 1 hr of hypoxia (delta PaCO2= - 0.6 mm Hg at 3400 m; - 3.9 mm Hg at 4300 m), decreased further after 1-5 days at high altitude (delta PaCO2= - 7.2 mm Hg at 3400 m; - 12.3 mm Hg at 4300 m) and then increased significantly after 6 days of chronic hypoxia (delta PaCO2= + 4.1 mm Hg at 3400 m; + 4.7 mm Hg at 4300 m). Although PaO2 decreased markedly during acute hypoxia, subsequent changes in PaCO2 at high altitude did not alter PaO2 from that observed during acute hypoxia (PaO2=52 mm Hg at 3400 m; 41 mm Hg at 4300 m). The pH of CSF increased during acute hypoxia (delta pH= + 0.013 unit at 3400 m; + 0.033 unit at 4300 m) and became more alkaline after 1-2 days at high altitude (delta pH= + 0.031 unit at 3400 m; + 0.064 unit at 4300 m). At 4300 m, CSF pH remained alkaline to control values throughout sojourn. Under these conditions of chronic hypocapnic hypoxia, CSF pH was imperfectly regulated and regulated in a magnitude equal to (3400 m) or less than (4300 m) arterial blood. Furthermore, the similarity of relative changes in CSF [HCO3-] and arterial [HCO3-] during chronic hypoxia may indicate a passive regulation of CSF [HCO3-] rather than local 'CSF-specific' mechanisms as previously proposed.
Acclimatization↗
The normal electrocardiogram of the domestic pony.
Twelve-lead electrocardiograms (ECGs) were recorded from 52 resting mature female domestic grade ponies. Evaluation of the 50 ECG's ultimately selected for analysis revealed numerous differences from accepted normal values of horses. Among these differences are shorter durations of the P and QRS complexes as well as P-R and Q-T intervals and a lower amplitude of the P wave. Pony ECG's displayed a lower incidence of wandering pacemaker and complete absence of second degree atrioventricular block, in contrast to the relatively routine occurrence of these phenomena in the horse. The existence of significant differences between the ECG of the pony and horse must be recognized and considered in future clinical and research applications of electrocardiography in the domestic pony.
Animals↗
Uteroplacental blood flow during alkalosis in the sheep.
Uteroplacental blood flow was measured by the radioactive-microsphere technique in eight near-term pregnant ewes during a normal control period and during maternal metabolic alkalosis. All measurements were made on awake, unanesthetized animals. Alkalosis, defined for this study as an arterial pH of 7.60 or greater, was produced by the oral administration of sodium bicarbonate, 3 g/kg body wt. The rise in pH thus produced was unaccompanied by significant changes in systemic arterial blood pressure and cardiac output, while maternal arterial Pco2 rose slightly from control levels. Cotyledonary blood flow declined from a control value of 1,177 ml/min to 1,025 ml/min during alkalosis. This decline of 13 percent in cotyledonary blood flow is significant (P smaller than 0.002). Blood flow to the remaining uterine tissue, or noncotyledonary uterus, did not change with alkalosis, being maintained at approximately 195 ml/min. It is concluded that maternal alkalosis, unaccompained by major changes in Pco2 and systemic arterial pressure, causes a small increase in the resistance of the uteroplacental circulation.
Alkalosis↗
Prolonged perfusion with a membrane oxygenator in awake ponies.
Prolonged extracorporeal membrane oxygenation (PEMO) was performed in 6 adult ponies with the membrane oxygenator in vein-to-artery bypass circuit. A flow rate equal to 46 per cent of control cardiac output was diverted through the PEMO circuit of 10 to 24 hours. Three of the 6 ponies were perfused for at least 20 hours and developed no complications. Immediately following initiation of PEMO, left ventricular output decreased; however, in the interval between 6 and 24 hours, left ventricular output was increased above control levels. Aortic pressure and left ventricular work were markedly elevated during PEMO. Pulmonary ventilation and oxygen uptake also decreased initially but were elevated during later stages of bypass. Pulmonary compliance did not change, except in those studies in which problems were encountered with perfusion techniques. Hepatic glycolysis and hyperglycemia occurred and were more severe in ponies with catheter-produced thrombi. Marked diuresis, which could be attributed only partially to the hyperglycemia, was present throughout PEMO. Based on the minimal morphologic changes observed in the ponies, extracorporeal circulation diverting one half of the cardiac output through a membrane oxygenator can be safely performed for up to 24 hours.
Animals↗
Cardiopulmonary measurements in nonanesthetized, resting normal ponies.
Cardiopulmonary measurements were determined in 19 nonanesthetized, normal ponies. Mean values for arterial pressure, pulmonary arterial pressure, cardiac output, heart rate, packed cell volume, and hemoglobin are reported, as well as acid-base determinations of arterial blood and cerebrospinal fluid. Respiratory function test data include total ventilation, respiratory rate, alveolar ventilation, oxygen uptake, and carbon dioxide output. The data compare favorably with the available data from previous reports on ponies. Because of large day-to-day variations in total ventilation, alveolar ventilation should be measured if ponies are used in the study of pulmonary function.
Animals↗
Coronary collateral development in the rhesus monkey (Macaca mulatta).
The ability of the rhesus monkey to form coronary collaterals was tested in ten animals. Ameroid constrictors were implanted on the left circumflex coronary artery and allowed to remain for 12 weeks. One animal died of an acute myocardial infarction nine days after surgery; the remaining animals survived without clinical signs referable to myocardial ischemia. The hearts were excised at 12 weeks postsurgery for perfusion fixation and coronary vascular injection with barium-gelatin. All hearts exhibited infarction scars in the circumflex-perfused regions, with infarcts varying from a transmural scar to cases with a thin margin of surviving myocardium at the epicardial surface. Coronary collaterals were infrequent and small in size, and particularly evident in the atria. We conclude that the rhesus monkey is unable to develop sufficient coronary collateral blood flow to prevent myocardial infarction after gradual, total coronary occlusion with ameroid constrictors.
Animals↗
Maturation of coronary responsiveness to exogenous adenosine in the rabbit.
Previous studies have indicated that some cardiac control systems, such as autonomic innervation, are incomplete in the newborn and undergo postnatal maturation. However, relatively little is known of maturational changes which will affect the ability of the coronary circulation to regulate blood flow during various interventions. We tested the hypothesis that the coronary circulation of the rabbit develops a progressive, age related increase in responsiveness to exogenous adenosine during the first 16 weeks of life. We examined the response of coronary circulation to exogenous adenosine in four age groups (6-10 days, 3-4 weeks, 7-8 weeks, 16 weeks) of rabbits by using an isolated heart preparation. Coronary flow was measured during an control period, during reactive hyperemia (following release of a 2 min coronary flow interruption), and during infusions of exogenous adenosine. All age groups had similar levels of control coronary blood flow, with a large increase in flow observed during reactive hyperemia. The volume of coronary flow was higher during reactive hyperemia (P less than 0.001) in the 6-10-day-old animals than in the other age groups. However, the 6-10-day-old age group showed a smaller (P less than 0.01) flow response to exogenous adenosine than the other age groups. In addition, the 6-10-day-old animals required higher adenosine concentrations to produce an initial detectable coronary flow increase and to produce the maximal flow response. Additional studies demonstrated a significant reduction in percentage flow debt repayment after theophylline administration in adult rabbit hearts. However, neonatal rabbit hearts showed no change in flow debt repayment following theophylline.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenosine↗
Dilatory capacity of the coronary circulation and its correlation to the arterial vasculature in the canine left ventricle.
The functional capacity of flow limiting myocardial conductance vessels was evaluated in canine hearts. In an isolated heart preparation transmural coronary flow distribution during maximal vasodilation was measured in the unloaded diastolic arrested left ventricle with tracer microspheres. The ratio of subendocardial versus subepicardial (ENDO/EPI) flow in the left ventricular free wall was 1.6. Measurements in 8 different wall layers showed a successive increase in maximal coronary flow from the subepicardium towards the deeper layers. A decreased subendocardial vascular resistance due to a better vascularization is forwarded as a mechanism to compensate for the extravascular compression during cardiac contraction. This statement contradicts the commonly accepted hypothesis that a diminished vascular tone with a reduction of the dilatory reserve in the subendocardium accounts for a homogeneous flow distribution in the normal beating heart. An augmentation of subendocardial supplying vessel capacity could be established from the angiographic determination of the coronary arterial volume of intramural small arteries and arterioles. From a strict parallelity in maximal coronary flow and coronary arterial volume within the wall, it becomes probable that these vascular structures are the flow-limiting factors which determine regional coronary flow reserve in the absence of extravascular compressive forces.
Animals↗
Application of stereology to coronary microcirculation.
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Animals↗
Myocardial function during acute hypoxia in the calf.
Hemodynamics and myocardial contractility were evaluated in five unanesthetized calves during acute hypocapnic and isocapnic hypoxia and during acute hypocapnic hypoxia with beta-adrenergic blockade. Both hypocapnic and isocapnic hypoxia, with mean PaO2 levels of 33.1 and 39.1 mm Hg respectively, produced a decline in stroke volume and index, while cardiac output and index were maintained at normoxic control levels by an increase in heart rate. Evaluation of myocardial contractility indices suggested an augmentation of left ventricular contractility during both hypocapnic and isocapnic hypoxia. Beta-adrenergic blockade effectively eliminated the increase in left ventricular contractility during hypocapnic hypoxia, suggesting an important role of the adrenergic nervous system in the genesis of the cardiovascular response of the calf to acute hypoxia. Right ventricular contractility indices failed to demonstrate a clear-cut augmentation of contractility during hypocapnic and isocapnic hypoxia when the concurrent increase in afterload was considered. Mean pulmonary arterial blood pressure rose significantly during hypocapnic and isocapnic hypoxia. The pulmonary pressor response to hypocapnic hypoxia was significantly augmented by beta blockade, indicating that the autonomic nervous system is capable of modifying the hypoxic pulmonary pressor response in this species.
Acute Disease↗
Inhaled gases affect the ultrasound contrast produced by Albunex in anesthetized dogs.
In anesthetized animals maintained with isoflurane using 100% oxygen as a carrier gas, Albunex (Molecular Biosystems, Inc., San Diego, Calif.) produced no ultrasound contrast in the left ventricle after intravenous administration. The current study tested the hypothesis that the inhalation of gas mixtures with increased concentrations of oxygen decreased the quality and duration of Albunex-induced contrast. Albunex (0.22 mL/kg) was injected intravenously into anesthetized dogs (n = 9) breathing compressed air, oxygen, mixtures of oxygen and nitrogen, or combinations of oxygen and nitrous oxide. Albunex produced ultrasound contrast of shorter duration and decreased quality during the inhalation of gas mixtures containing increased amounts of oxygen. In the presence of inhaled gas mixtures containing nitrous oxide, Albunex produced no contrast in the left ventricle, regardless of the oxygen content. These data indicate that the inhalation of gas mixtures containing smaller amounts of nitrogen, compared with air, decreased the ability of Albunex to cause ultrasound contrast in the heart after intravenous administration.
Air↗
Suprascapular nerve entrapment caused by supraglenoid cyst compression.
Twenty-two cases of suprascapular nerve entrapment caused by supraglenoid cyst compression were reviewed. Pain and weakness were the presenting symptoms in 14 shoulders and pain alone in 8. Twenty of the cysts were diagnosed by magnetic resonance imaging, and two were confirmed at surgical exploration. Electromyography of 20 shoulders was positive for neurologic involvement for both the infraspinatus and supraspinatus in 4 cases, for the infraspinatus only in 12, and negative in 4. Sixteen shoulders were treated by open excision, arthroscopy, or both. Superior labral lesions were diagnosed in 11 of 12 patients who underwent arthroscopy. At follow-up 10 of the patients who underwent surgery had complete resolution of symptoms, 5 had occasional pain or weakness, and 1 recurrence required a second surgery. Of six patients treated without surgery, two improved and four had no change. Supraglenoid ganglion cysts are common and can easily be diagnosed by magnetic resonance imaging. For patients with symptoms arthroscopy with repair of the superior labral lesion and either arthroscopic debridement or direct open decompression and excision of the cyst is recommended.
Adolescent↗
Cost-benefit comparison: holmium laser versus electrocautery in arthroscopic acromioplasty.
This prospective study was designed to measure the costs and benefits of using a laser rather than electrocautery for soft tissue resection during arthroscopic shoulder decompression. Forty-nine shoulders with refractory Neer stage II impingement (persistent fibrosis and tendinitis) were divided into 2 groups. The composition of the 2 groups was similar with regard to sex, worker's compensation status, dominant arm involvement, duration of symptoms, and length of conservative treatment. In one group, electrocautery was used to ablate the bursa and periosteum, release the coracoacromial ligament, and maintain hemostasis. In the other group, a laser was used in place of electrocautery. Patients had been evaluated preoperatively with 2 functional scoring systems. The patients were reexamined at 1 week and at 1, 2, 3, 6, and 12 months after surgery. There were no differences between the groups with regard to functional outcome or satisfaction. There was also no difference in terms of estimated blood loss or operative time. However, there was a statistically significant difference in total hospital charges between groups, with the laser group having a 23% higher hospital bill. On the basis of these results, it is concluded that there was no medical benefit to laser-assisted arthroscopic subacromial decompression but there was an increased monetary cost.
Adult↗
Nonoperative treatment of acute anterior cruciate ligament injuries in a selected group of patients.
Conservative treatment of acute anterior cruciate ligament injuries was recommended to selected patients, including those with sedentary occupations, low athletic demands, or ages greater than 30 years. Patients with generalized hyperligamentous laxity were excluded. Fifty-five of 61 patients were available at an average followup of 46 months from the time of initial injury. At followup, giving-way symptoms had not occurred in 23 patients (42%); in 22 (40%) giving way occurred occasionally. Of the 44 patients involved in high- or moderate-demand athletics, 33 (70%) were able to continue with moderate-demand sports. Presence of a medial collateral ligament sprain did not affect the longterm function. Forty-eight percent of the patients scored excellent or good (9 and 18 patients, respectively) on the Hospital for Special Surgery ligament scoring system; 8 (15%) later chose surgical reconstruction. The remaining 47 patients did not believe that their symptoms were severe enough to warrant any further intervention. In a group of individuals who are older and relatively inactive, nonoperative management of anterior cruciate ligament injuries can yield satisfactory results, provided the patients are willing to accept a modest amount of instability and a slight risk of meniscal injury.
Acute Disease↗
Arthroscopic versus open reconstruction of the shoulder in patients with isolated Bankart lesions.
We compared open and arthroscopic stabilizations of true Bankart lesions in patients with traumatic, unidirectional anterior glenohumeral dislocations. The 27 patients were men (age range, 18 to 56 years) who were involved in recreational sports. One group (15 patients) had elected an arthroscopic Bankart repair; the other group (12 patients) had chosen open stabilization with a standard deltopectoral approach. Patients were followed up 17 to 42 months after surgery by examination, radiographs, and interviews. In the open repair group, 1 of the 12 patients experienced a subluxation in the follow-up period, but no patients had dislocations or reoperations. In the arthroscopic group, 5 of 15 patients had experienced subluxation or dislocation; of these 5 patients, 2 underwent reoperation. The arthroscopic group had significantly worse results in satisfaction, stability, apprehension, and loss of forward flexion in the operated limb. In summary, the arthroscopic procedure did not significantly improve function; instead, it produced an increased failure rate compared with the open procedure. Therefore, we believe that open stabilization remains the procedure of choice for patients with true Bankart lesions.
Adolescent↗