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Biomedical subjects

N B Ackerman

Publications and source records attributed to N B Ackerman.

At least 19 recordsLinked to original sources
PubMed1990

High-frequency oscillation during simulated altitude exposure.

Ventilatory requirements using high-frequency oscillation (HFO) during simulated altitude exposure were investigated in control dogs and animals with oleic acid-induced lung injury. FIO2 values of 0.21 and 1.0 were supplied by bias flow to the normal and injured dogs, respectively. After a control period, animals were exposed to a simulated altitude of 8,000 ft (barometric pressure 564 torr), followed by a second control period at ground level. Both experimental groups had similar values of PaCO2 at ground level and during exposure to reduced barometric pressure. The tidal volume necessary to maintain eucapnia was higher in oleic acid-injured animals compared with the control group; cardiac output and functional residual capacity were lower. The alveolar-arterial oxygen difference was substantially larger in the oleic acid group. Adequate gas exchange can be maintained with HFO during exposure to altitude provided that ventilation and inspired PO2 are not reduced below normobaric levels.

Altitude↗
PubMed1989

Endoscopic management of gastric outlet obstruction following surgery for morbid obesity.

Surgery of morbid obesity is associated with significant morbidity, which is considerably increased for reoperative surgery. Over the past two and a half years endoscopic balloon dilation was performed in eight patients for stenosis of gastrojejunostomy following gastric bypass. The technique of dilation, indications, and pitfalls are discussed. The procedure was safe and effective. Patients who had dilation performed successfully avoided surgery entirely in seven of eight cases. Therapy was modified in two other patients based on endoscopy findings. Endoscopy was found to be more reliable and superior to upper gastrointestinal (UGI) series for evaluation of symptoms following gastric bypass procedures. Based on our experience and literature review we propose that endoscopy is the preferred alternative to major reoperative surgery and urge its wider use.

Catheterization↗
PubMed1989

Evidence that epinephrine acutely redistributes blood flow to experimental intrahepatic tumors.

Tumor microcirculation was studied in Sprague-Dawley rats with solitary intrahepatic implants of Walker carcinosarcoma tumors. Thioflavine S (TS), a fluorescent dye that stains capillary endothelium acutely, was injected intraportally or intra-arterially in order to demonstrate patterns of blood flow through normal liver tissue and through tumor. The dye was given immediately after intraportal injection of 10 micrograms of epinephrine in some animals and 3 minutes after the epinephrine in others. Control animals received TS alone. Additional animals were given TS immediately after intra-arterial epinephrine. The degree of resulting fluorescence in tumor and liver was graded subjectively from 0 to 3+. In the controls and in animals receiving TS 3 minutes after epinephrine, fluorescence in the centers of tumors was absent or, at most, faintly present. In contrast, all animals given epinephrine either intraportally or intra-arterially immediately before the dye showed intense fluorescent staining within the centers of the tumors. Subjective grading averaged 0.6 +/- 0.1 in the controls, 2.2 +/- 0.1 in those receiving intraportal epinephrine immediately before TS, and 1.0 +/- 0.3 in those receiving TS 3 minutes after epinephrine. Results were significantly higher in the latter group (p less than 0.01). Subjective grading in animals receiving intra-arterial epinephrine immediately before TS averaged 2.5 +/- 0.3. These experiments confirm previous studies in this laboratory that demonstrated an acute short-lived redistribution of blood flow into the centers of intrahepatic tumors after administration of epinephrine.

Animals↗
PubMed1988

Increased capillary flow in intrahepatic tumors due to alpha-adrenergic effects of catecholamines.

Chemotherapy of liver metastases is dependent on adequacy of tumor microcirculation. Attempts have been made, experimentally, to improve tumor blood flow with appropriate vasoactive agents. Capillary blood flow within intrahepatic Walker carcinosarcomas and normal liver were measured with a laser doppler needle probe. Tumor capillary blood flow increased briefly but significantly with intraportally administered epinephrine. This effect was blocked by phenoxybenzamine but not by propranolol. The response of capillary flow in normal liver to epinephrine was dose related, with decreased flow with higher doses, and slight increase with lower doses. Norepinephrine and phenylephrine produced brief increases in capillary flow in tumor and liver, and isoproterenol caused a decreased flow. In studies with injected silicone rubber (Microfil, Canton Bio-Medical Products, Boulder, CO) performed previously, and on electron microscopic examination, there was evidence of increased vascular filling within central areas of tumors after epinephrine. These studies suggest that the brief but potent effect of epinephrine on tumor capillary flow could be useful in improving delivery of chemotherapeutic agents to liver tumors.

Animals↗
PubMed1988

The effects of steroidal and nonsteroidal anti-inflammatory agents on uptake of Evans blue in experimental metastasis.

The effects of anti-inflammatory drugs on uptake of Evans blue were studied in solitary Walker carcinosarcomas implanted in the livers of Sprague-Dawley rats. Animals were sacrificed at 5 min, 30 min, and 6 hr after administration of the anti-inflammatory drugs and Evans blue, and spectrophotometric measurements of the Evans blue in tumor and normal liver tissue were carried out. Uptake of Evans blue in the tumors was significantly decreased at all time periods after the injection of the following, as compared to controls: steroids (cortisol, methylprednisolone, and triamcinolone), the antihistamine diphenhydramine, and nonsteroidal anti-inflammatory agents (naproxen, ibuprofen, indomethacin, and phenylbutazone). The effects of these drugs on uptake of Evans blue in the normal liver were more variable.

Animals↗
PubMed1988

High-frequency ventilation: its various techniques and clinical applications.

High-frequency ventilation can be considered to be ventilation with a tidal volume close to or less than the anatomical dead space. The various techniques of high-frequency ventilation will be discussed including high-frequency positive pressure ventilation, high-frequency jet ventilation or high-frequency flow interruption, and high-frequency oscillatory ventilation. The clinical application of the various types of high-frequency ventilation will be discussed including their use during surgical procedures, their use for various kinds of barotrauma, their usefulness in respiratory failure, their use in newborns with hyaline membrane disease, and their usefulness for respiratory support in emergency situations involving cardiopulmonary resuscitation. The potential use for high-frequency ventilation in the management of battlefield casualties and air evacuation of critically ill patients will also be discussed.

Barotrauma↗
PubMed1987

Enhancement of tumor blood flow and tumoricidal effect of doxorubicin by intraportal epinephrine in experimental liver metastasis.

Laser Doppler capillary perfusion monitoring was performed in 25 Sprague-Dawley rats with solitary intrahepatic implants of Walker carcinosarcomas. Doses of intraportal epinephrine from 1 to 10 micrograms produced an immediate rise in capillary blood flow, reaching peak levels by 16 s. The increased flow lasted an average of 57 s. Because epinephrine selectively increased tumor blood flow, studies were performed to determine if enhancement of the chemotherapeutic effect of doxorubicin could be achieved. Forty-two rats with seven-day hepatic implants were treated sequentially with intraportal epinephrine (10 micrograms) and doxorubicin hydrochloride (10 mg/kg) or doxorubicin alone. After only two courses of chemotherapy, a significant difference in necrosis and cell viability was obtained in those animals treated with epinephrine intraportally prior to doxorubicin infusion. Enhancement of the tumoricidal effect of chemotherapy can be achieved by manipulating the blood flow to developing tumors pharmacologically.

Animals↗
PubMed1987

Hyperbiliverdinemia in the bronze baby syndrome.

The bronze baby syndrome is an unusual complication of phototherapy for hyperbilirubinemia in the neonate. The pigment or pigments responsible for the discoloration in this syndrome have not yet been identified. Suspected pigments include photodegradation products of bilirubin and copper-porphyrins. We present here the case of a neonate with bronze baby syndrome whose serum had increased spectral absorbance in the region of maximum absorbance for biliverdin. We suggest that biliverdin pigments may also contribute to the "bronze" color associated with this syndrome.

Adult↗
PubMed1987

Patent ductus arteriosus during high-frequency ventilation for hyaline membrane disease.

The cardiovascular effects of a patent ductus arteriosus (PDA) in a premature baboon model of hyaline membrane disease treated with conventional positive-pressure ventilation (CPPV) or high-frequency ventilation (HFV) were studied. Twenty-seven (84%) of 32 infant baboons delivered at 75% gestation had positive retrograde aortograms at one hour of life. Eleven (34%) of these infant baboons had persisting evidence for retrograde flow over the first 24 h by Doppler examination. Significantly higher fluid requirements and bicarbonate requirements were present in the animals with a persisting PDA. Mean aortic BP values were significantly lower in these same animals. No significant differences were found between groups when mean airway pressure, heart rate, urine output, or form of ventilation were compared. The only significant differences found between the conventional and high-frequency ventilated animals with PDA were higher peak airway pressures and lower PEEP levels in the conventionally ventilated infants. The premature baboons can be a useful primate model to study the PDA. There appears to be no significant difference regarding the clinical effects of HFV and CPPV on PDA.

Acidosis↗
PubMed1987

Ventilatory management of infant baboons with hyaline membrane disease: the use of high frequency ventilation.

We tested the hypothesis that high frequency oscillatory ventilation (HFOV) would result in decreased pulmonary barotrauma in infants with hyaline membrane disease by comparing HFOV at 10 Hz to conventional positive pressure ventilation with continual distending airway pressure (PPV/PEEP) in premature baboons with hyaline membrane disease. Nineteen baboon fetuses were randomized to one of two treatment groups, delivered at 140 +/- 2 days, and, after stabilization and instrumentation of PPV/PEEP, placed in their respective ventilator group. Animals on conventional ventilation were managed by adjustment of tidal volume and frequency (to 1 Hz) to keep PaCO2 below 55 and by adjustment of the mean airway pressure. One of the "HFOV" group died of cardiovascular complications before going on HFOV and was eliminated from data analysis. The remaining HFOV baboons survived the 11-day experimental period without evidence of airleak. Six of the 11 prematures treated with PPV/PEEP developed pulmonary interstitial emphysema and/or pneumothorax and five of the animals died within 48 h. The intergroup differences in airleak were significant (p less than 0.05). Mean airway pressure (measured at the proximal airway) was higher initially with HFOV but then was lowered more rapidly than in the PPV/PEEP animals. The arterial to alveolar oxygen ratio rose and the FIO2 could be lowered more rapidly with HFOV than with conventional ventilation. These differences reached significance by 20 h. After 60 h there were no significant differences between HFOV and the PPV/PEEP survivors. HFOV resulted in more uniform saccular expansion, higher arterial to alveolar oxygen ratio, less oxygen exposure, and decreased acute barotrauma when compared to PPV/PEEP.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1987

Ventilatory criteria for aeromedical evacuation.

Ventilatory requirements during simulated aeromedical transportation were investigated in normal dogs and animals with oleic acid-induced lung injury. Inspired oxygen fractions of 0.21 and 1.0 were used to ventilate the normal and injured dogs, respectively. Both groups were ventilated with a constant-volume piston ventilator. After a control period, animals were exposed to a simulated altitude of 8,000 ft (barometric pressure 564 mm Hg), followed by a second control period at ground level. Both groups of animals had no change in carbon dioxide production, arterial PCO2 or ventilation during exposure to reduced barometric pressure. Systemic blood pressure, heart rate, cardiac output, and lung volume were all lower in oleic acid-injured animals than controls; the alveolar-arterial oxygen difference was larger in the oleic acid group. With altitude exposure, arterial and mixed venous oxygen tensions were decreased in both groups. Adequate gas exchange can be maintained during exposure to altitude even in animals with abnormal function provided that ventilation is constant and the inspired oxygen fraction is increased to compensate for the reduced barometric pressure.

Aerospace Medicine↗
PubMed1986

Experimental studies on the role of the portal circulation in hepatic tumor vascularity.

Whereas the predominance of arterial circulation in the nourishment of liver tumors has been well established, the portal circulation also appears to play a significant role under some circumstances. Studies were performed on Sprague-Dawley rats with Walker carcinosarcomas implanted in the liver, and vascularity was identified by portal and arterial injection of pigmented silicone rubber (Microfil, Canton Bio-Medical Products, Boulder, CO). Experimental groups consisted of animals with hepatic artery ligation at time of tumor implant with Microfil injection 3 or 7 days later, and animals with hepatic artery ligation 3 or 7 days after tumor implantation with immediate Microfil injection. In all groups, portal filling of tumor microcirculation was identified. Histologic examination of tumors in control animals randomly demonstrated portally injected Microfil in vessels within the substance of the tumors. These studies confirm earlier experiments demonstrating a portal component in the microcirculation of liver tumors, and justify attempts to use the portal circulation in anticancer therapy.

Animals↗
PubMed1986

Second hepatoma developing 13 years after resection of first tumor.

A patient underwent a left-sided hepatic lobectomy for primary hepatocellular carcinoma 13 years ago and remained symptom free. He then presented with spontaneous rupture of a large tumor in the right lobe of the liver. Although this tumor proved to be primary hepatocellular carcinoma, there were significant histological differences between the two lesions, suggesting that this was a second primary liver tumor. Bleeding from the tumor was controlled by selectively ligating the branches supplying the area of hemorrhage.

Aged↗