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Biomedical subjects

B D Butler

Publications and source records attributed to B D Butler.

At least 55 records · Page 3Linked to original sources
PubMed1988

A comparison of different methods of lubrication of glass syringes used to identify the epidural space.

Measurement of loss of resistance in glass syringes is a method widely used to locate the epidural space in epidural anaesthesia. Static and dynamic forces were measured under four experimental conditions in new glass syringes: unpolished, dry; polished, dry; unpolished, saline lubricated; and polished, saline lubricated. The unpolished saline lubricated syringes had a mean (SD) static force of 53.18 (15.0) g and dynamic force of 40.88 (15.2) g. These values were significantly greater than for polished dry syringes where the values were 5.27 (2.1) g and 4.38 (0.94) g, respectively. The results show that the least amount of resistance to plunger movement is obtained by dry polishing glass syringes.

Anesthesia, Epidural↗
PubMed1988

Vascular pressures and passage of gas emboli through the pulmonary circulation.

Anesthetized dogs received venous air infusions at 0.35 ml.kg-1.min-1. In 60% of a group of 15 dogs, venous bubbles spilled over into the arterial circulation and were detected with the ultrasound Doppler technique. The pulmonary vascular pressure gradient (pulmonary artery pressure-pulmonary venous pressure or left atrial pressure) measured at the instant that spillover occurred was 34.7 +/- 4.7 mmHg. In a 2nd group of dogs we raised the pulmonary vascular pressure gradient before the venous air infusions to achieve spillover of bubbles 100% of the time. The resultant pressure gradient at the time of spillover of venous bubbles was 52.0 +/- 2.0 mmHg (P less than 0.05). It is concluded that venous bubbles can cross the lungs of anesthetized dogs when the driving pressures are sufficient to overcome the normal filtering function.

Animals↗
PubMed1987

Arterial air embolism of venous origin in dogs: effect of nitrous oxide in combination with halothane and pentobarbitone.

The effects of using nitrous oxide (N2O) with halothane or pentobarbitone anaesthesia on the filtration of venous air emboli (VAE) by the pulmonary circulation were studied in dogs. Dogs anaesthetized with either pentobarbitone, pentobarbitone/N2O, halothane, or halothane/N2O were embolized with venous air into the right atrium at 0.25 to 0.35 ml.kg-1.min-1 for 30 min. The animals were in a supine, head down position. A Doppler ultrasonic probe located over the suprarenal aorta detected arterial bubbles that escaped filtration by the lungs. No bubbles were detected at 0.25 ml.kg-1.min-1, but at 0.30 ml.kg-1.min-1 the incidence was 11 per cent (pentobarbitone), 0 per cent (pentobarbitone/N2O), 33 per cent (halothane), and 63 per cent (halothane/N2O) and at 0.35 ml.kg-1.min-1, 44 per cent (pentobarbitone), 14 per cent (pentobarbitone/N2O), and 56 per cent (halothane). Half of the dogs receiving VAE with halothane/N2O at 0.30 ml.kg-1.min-1 died within the first 10 min of the air infusion. Thus, no animals were studied at the next higher dose (0.35 ml.kg-1.min-1). The results suggest that the occurrence of VAE with nitrous oxide anaesthesia may result in greater haemodynamic consequence and increased likelihood for spillover of the venous bubbles into the arteries if used with halothane as compared to pentobarbitone.

Anesthesia, Inhalation↗
PubMed1987

Removal of tracheal secretions in anesthetized dogs: balloon catheters versus suction.

Artificial secretions were removed by suction (using 12- or 18-French suction catheters) or by means of a balloon-tipped catheter (6-French Fogarty arterial embolectomy catheter) in 20 experiments performed on five dogs anesthetized with halothane. Each dog had 5 ml of mucin injected 10 cm down the endotracheal tube prior to a 30-sec period of intermittent positive pressure ventilation. After this procedure, the ventilator was disconnected and the secretions were removed by suction with the 12- or 18-French catheters or by the Fogarty catheter. Each dog had balloon removal performed twice and suction performed once with the 12-French and once with the 18-French catheter. The endotracheal tube was cleaned and a 15-min stabilization period was allowed between each experiment. Arterial blood pressure (MAP) and pulmonary artery pressure (PAP) did not change after either technique. There were no ECG changes, arrhythmias, or alterations in PaCO2. The PaO2 was significantly lower in the two suction catheter groups [520 +/- 33 mm Hg (12 French) and 451 +/- 31 mm Hg (18 French)] than in the balloon removal group (564 +/- 10 mm Hg) (P less than 0.05). The balloon technique removed more secretions (4.52 +/- 0.06 ml) than did suction (12 French, 1.32 +/- 0.17 ml; 18 French, 2.11 +/- 0.44 ml). Balloon removal of tracheal secretions has two advantages over conventional suction techniques: it removes more secretions, and it has less detrimental effect on arterial oxygenation.

Anesthesia, Endotracheal↗
PubMed1987

Mechanisms of succinylcholine-induced arrhythmias in hypoxic or hypoxic:hypercarbic dogs.

To evaluate the effects of succinylcholine on cardiac arrhythmias and serum levels of potassium and catecholamines, dogs with hypoxia alone and with hypoxia and hypercarbia were studied during anesthesia with halothane or enflurane. After the injection of succinylcholine (0.3 mg/kg), cardiac arrhythmias occurred in all halothane:hypoxia dogs and in 70% of dogs given halothane during hypoxia:hypercarbia. No dogs given enflurane anesthesia developed arrhythmias. Serum potassium levels increased significantly 3 and 5 min after succinylcholine in all groups. Serum epinephrine levels increased in the halothane-hypoxia:hypercarbia and enflurane:hypoxia groups and, after the injection of succinylcholine, epinephrine levels increased further in dogs in the halothane:control, halothane:hypoxia, halothane-hypoxia:hypercarbia, enflurane:hypoxia, and enflurane-hypoxia:hypercarbia groups. Norepinephrine levels increased with enflurane-hypoxia:hypercarbia and after the succinylcholine in the halothane:hypoxia, halothane-hypoxia:hypercarbia, and enflurane-hypoxia:hypercarbia groups. The results suggest that succinylcholine induces arrhythmias by sympathetic stimulation and that halothane sensitizes the myocardium to arrhythmias at the same levels of serum catecholamines and potassium in the presence of hypoxia or hypoxia:hypercarbia more than does enflurane.

Anesthesia, Inhalation↗
PubMed1986

Production of microbubbles for use as echo contrast agents.

A variety of agents have been proposed for use as contrast for ultrasound studies. Several reports suggest the use of microbubbles because of their superior sonographic resolution. We describe a method of producing calibrated microbubbles utilizing differential absorption and gas injection techniques. Gas injection methods are described using a Plexiglas microbubbler apparatus with a fine needle orifice. The bubbles originally produced by this device are in a size range of 40-100 microns and consist of nitrogen (10%) and carbon dioxide (90%). The differential absorption technique uses THAM [tris(hydroxymethyl)aminomethane hydrochloride] to absorb the carbon dioxide (diluent gas) from the bubbles selectively, leaving smaller microbubbles. The microbubbles can be calibrated using the electric gating principle of the Coulter Counter.

Bicarbonates↗
PubMed1986

Effect of bronchial blood flow on pulmonary artery wedge pressure with pulmonary embolism.

Discrepancies between pulmonary artery wedge pressure (WP) and left atrial pressure (LAP) occur with pulmonary embolism. Theoretically, this discrepancy could be affected by the bronchial circulation or by the type of embolus. To test this in dogs, we determined the effects of embolism induced by glass beads and by air upon the WP with intact vs. ligated bronchial blood flow to the left lower lobe. For those animals receiving pulmonary air infusions, the pulmonary artery pressure, WP, and pulmonary vascular resistance showed significant (p less than .05) elevations with no change in LAP. There were no changes in these values when the bronchial blood flow was interrupted. When glass beads (120 mu) were injected into the left lower lobe, the pulmonary artery pressure and pulmonary vascular resistance rose as in the air emboli groups (p less than .05); however, WP remained at control values and approximated LAP. Obstructing the bronchial blood flow did not change this response. We conclude that the discrepancy between WP and LAP depends upon the type of embolus and is not affected by bronchial blood flow.

Animals↗
PubMed1985

Phospholipids identified on the pericardium and their ability to impart boundary lubrication.

Phospholipids have been identified by thin-layer chromatography in appreciable quantities in pericardial fluid taken from 12 dogs and found to include sphingomyelin and phosphatidylcholines, -ethanolamines, -inositols and -serines--the cholines predominating. The extracts, the synthetic surfactants and a mixture of synthetics simulating the extracts were all found to be good lubricants when tested by a standard method. The phosphatidylcholines were capable of reducing friction between two otherwise hydrophilic surfaces by as much as 100- to 200-fold when deposited as an oriented monolayer. A goniometer was used to measure an average contact angle of 33 degrees for a drop of saline placed upon the internal wall of the pericardium, indicating an appreciably hydrophobic surface anticipated if surfactant were directly adsorbed. The results are consistent with the classical theory of "boundary" lubrication (17) as modified (21) to reflect the almost ideal molecular structure of the identified surfactants for adsorption, film cohesion and interaction of fatty-acid chains during sliding. This model is proposed as an alternative to hydrodynamic lubrication in the pericardium and one compatible with several practical aspects such as pericardial rub and the maintenance of normal heart action after pericardectomy.

Animals↗
PubMed1985

Surfactants identified in lung lymph and their ability to act as abhesives.

Phospholipid has been extracted from pulmonary lymph collected from 10 dogs. Thin-layer chromatography was used to identify phosphatidylcholine (PC) 55.6 +/- 2.9%, sphingomyelin 21.3 +/- 1.7%, phosphatidylethanolamine 11.2 +/- 4.9%, and lysophosphatidylcholine 5.9 +/- 0.8%. All extracts proved highly surface active, reducing the surface tension of saline to 27.7 +/- 0.7 dyn/cm upon 80% film compression and increasing the maximum contact angle on glass (theta) from 7 +/- 1 to 47.4 +/- 1.4 degrees. The hydrophobic properties induced on glass were further demonstrated by the ability to cause saline to withdraw and expose a dry surface. A standard adhesion test was used to measure the "tack" produced by the major proteins in lymph. However, when the surface energy of the hydrophilic glass surfaces was reduced by a monolayer of lymph phospholipid extract or an equivalent mixture of synthetic surfactants, the adhesive force was reduced by 79 +/- 4% for albumin and 55 +/- 4% for globulin. As a 0.1% liposomal suspension, PC gave 55% release with albumin. Reversible bonding of the lumen of lymph vessels by the "tacky" proteins present is discussed as a possible factor contributing to the large changes in flow resistance known to occur in the pulmonary lymphatic system.

Adhesives↗
PubMed1985

Transpulmonary passage of venous air emboli.

Twenty-seven paralyzed anesthetized dogs were embolized with venous air to determine the effectiveness of the pulmonary vasculature for bubble filtration or trapping. Air doses ranged from 0.05 to 0.40 ml X kg-1 X min-1 in 0.05-ml increments with ultrasonic Doppler monitors placed over arterial vessels to detect any microbubbles that crossed the lungs. Pulmonary vascular filtration of the venous air infusions was complete for the lower air doses ranging from 0.05 to 0.30 ml X kg-1 X min-1. When the air doses were increased to 0.35 ml X kg-1 X min-1, the filtration threshold was exceeded with arterial spillover of bubbles occurring in 50% of the animals and reaching 71% for 0.40 ml X kg-1 X min-1. Significant elevations were observed in pulmonary arterial pressure and pulmonary vascular resistance. Systemic blood pressure and cardiac output decreased, whereas left ventricular end-diastolic pressure remained unchanged. The results indicate that the filtration of venous bubbles by the pulmonary vasculature was complete when the air infusion rates were kept below a threshold value of 0.30 ml X kg-1 X min-1.

Animals↗
PubMed1984

Surfactants identified in synovial fluid and their ability to act as boundary lubricants.

Thin-layer chromatography has been used to identify phospholipids extracted from canine synovial fluid, the major component (45%) being phosphatidyl choline (PC). The extracts and their components have been shown to be surface active in reducing the surface tension of water and to be readily adsorbed to hydrophilic solids, whose surfaces then become hydrophobic. These adsorbed monolayers of synovial surfactant were then found to be excellent boundary lubricants in vitro, reducing the coefficient of kinetic friction (mu) in the dry state and under physiological loading by up to 97% for extracts and 99% for PC alone, reaching mu = 0.01. Surface-active phospholipid is put forward as the possible active ingredient in joint lubrication and shown to be consistent with previous biochemical studies to elucidate its identity. The model essentially follows the classical Hardy model for boundary lubrication imparted by surfactants. It is discussed in relation to a new approach in providing artificial lubrication and facilitating tissue release in patients with arthritis.

Animals↗
PubMed1983

Role of surface-active phospholipids in gastric cytoprotection.

Intragastric administration of a liposomal surfactant suspension markedly reduced acid-induced gastric ulcerogenesis and bleeding in rats. The concentration of surface-active molecules intrinsically present in the gastric mucosa was increased two to six times by administration of 16,16-dimethyl prostaglandin E2. Thus, local accumulation of surface-active phospholipids may be an integral component of the cytoprotective mechanism activated by prostaglandin treatment.

Animals↗
PubMed1983

Gastric mucosal barrier: hydrophobic lining to the lumen of the stomach.

The contact angle subtended between a droplet of aqueous fluid and nonwettable surfaces provides a direct estimation of their degree of hydrophobicity. The mean contact angle recorded in dogs at the oxyntic mucosal surface was 85.2 degrees, a value characteristic of acid-resistant substances such as polyethylene. This indicates that the mucosal surface of the stomach has a hydrophobic lining that may be attributed to the surface-active phospholipids known to be present in both the gastric mucosa and juice. Barrier breakers such as bile and aspirin were found virtually to eliminate the hydrophobicity. Hydrophobicity was found to be different in the esophagus, antrum, proximal and distal duodenum, and the colon but consistent with their resistance to acid attack. Endogenous surfactants are discussed for their capability to provide a cohesive and strongly adsorbed protective monolayer--a physical model for the gastric mucosal barrier compatible with the major properties of the gastric lining and many features of ulcerogenesis, including the protection afforded by prostaglandins.

Animals↗
PubMed1983

Distribution of surfactants in the canine gastrointestinal tract and their ability to lubricate.

Surface-active phospholipids, chemically similar to pulmonary surfactants, have been identified by thin-layer chromatography in gastric juice and on the mucosal lining of five tissues along the canine gastrointestinal tract. These included esophagus, oxyntic tissue, midduodenum, midjenunum, and midcolon. The mucosal phospholipid composition did not change appreciably along the length of the gastrointestinal tract, with the most prominent species being phosphatidylcholine (PC) (34-45%) and phosphatidylethanolamine (PE) (18-32%). The gastrointestinal mucosal surface also contained lesser amounts (5-10% each) of sphingomyelin (Sp), lysophosphatidylcholine, phosphatidylinositol (PI), and phosphatidylserine (PS) and small but detectable quantities of phosphatidylglycerol (PG) and phosphatidic acid. Both the lipid extracts of all six gastrointestinal sources as well as commercially available phospholipids identified in these samples (PC, Sp, PE, PI, PS, and PG) proved to be good boundary lubricants. Each reduced the coefficient of friction by greater than 75% between glass and carboxylated yarn when tested by a standard method for evaluating textile "sizes." The results are discussed in relation to the possible role of the surface-active molecules in imparting properties conducive to lubrication and acid protection onto the gastrointestinal epithelium.

Animals↗
PubMed1983

Pulmonary microvascular permeability after coronary arterial ligation in dogs.

Recent studies have indicated that pulmonary microvascular permeability may be increased after coronary arterial ligation. We tested this by estimating the pulmonary microvascular reflection coefficient (delta) in six anesthetized control dogs and in six dogs in which we ligated the left anterior descending coronary artery. We cannulated lung lymph vessels and measured the lymph and plasma protein concentrations (CL and CP, respectively). The left atrial pressure was increased to decrease CL to a minimum. We used the minimum CL to estimate delta as 1 -CL/CP. delta for the control [0.70 +/- 0.03 (SD)] and coronary artery ligated groups (0.70 +/- 0.04) were almost identical. This data indicates that coronary artery ligation does not increase pulmonary microvascular permeability.

Animals↗