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Biomedical subjects

N B Ackerman

Publications and source records attributed to N B Ackerman.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1986

A nonpulmonary complication of high-frequency oscillation.

High-frequency ventilation (HFV) has been suggested as an alternative to standard positive-pressure ventilation with positive end-expiratory pressure (PPV/PEEP) in the treatment of infants with hyaline membrane disease. To assess the relative safety and efficacy of HFV, we compared standard PPV to HFV delivered by oscillation (HFO) and HFV delivered by a flow interrupter (HFFI) in a previously validated preterm baboon model of hyaline membrane disease. At necropsy, the livers of several animals were unexpectedly found to have severe fatty change and/or cytoplasmic vacuolization and edema. There was a strong correlation between use of HFO and the development of liver lesions. The hepatic lesion may reflect decreased cardiac output with a concomitant fall in splenic perfusion and/or alterations in normal intrathoracic pressure that increase resistance in the hepatic vasculature. Although the etiology cannot be determined precisely, these data suggest the potential for nonpulmonary complications of HFV in the immature newborn and mandate further investigation before its widespread clinical application.

Animals↗
PubMed1986

Pulmonary interstitial emphysema treated by high-frequency oscillatory ventilation.

Twenty-seven low birth weight infants who developed pulmonary interstitial emphysema (PIE) and respiratory failure while on conventional ventilation were treated with high-frequency oscillatory ventilation (HFOV). The mean birth weight was 1.2 kg (range 0.55 to 2) with gestational age of 28 wk (range 25 to 34). Ten patients died, six of whom had documented sepsis with shock and were therefore excluded from analysis. All patients showed initial improvement on HFOV. Surviving patients showed continued improvement in oxygenation and ventilation at increasingly lower fraction of inspired oxygen and proximal airway pressure with resolution of PIE, while nonsurvivors progressively developed chronic respiratory insufficiency with continued PIE from which recovery was not possible. Overall survival in nonseptic patients was 80% (16 of 20). We found HFOV to be effective in the treatment of PIE and hypothesize that interstitial airleak is decreased during HFOV because adequate ventilation is provided at lower peak distal airway pressures.

Critical Care↗
PubMed1986

Wound closure in obese patients.

A five year randomized prospective study was carried out to compare subcutaneous drains versus a type of stay suture closure in morbidly obese patients. While acceptable wound infection rates were found, no statistical superiority was established between these types of closures.

Adult↗
PubMed1985

Cholecystectomy in patients with mild cirrhosis. A more favorable situation.

A conservative approach toward elective cholecystectomy in the patient with cirrhosis has been suggested because of the strong likelihood of excessive bleeding, sepsis, and multiple organ failure. We reviewed this problem in two medical centers, studying 27 patients with cirrhosis who had undergone nonemergency biliary tract surgery. Most patients had adequate liver function preoperatively. Most operations were cholecystectomies without duct exploration. Among factors analyzed were liver function tests, coagulation tests, and Child's classification. Prothrombin time was less than 2.5 s above control in 18 patients, more than 2.5 s above control in four patients, and not recorded in five patients. All survived the operation with benign postoperative courses. Only one patient had excessive bleeding; this patient had an elevated prothrombin time preoperatively. We conclude that elective cholecystectomy can be performed safely in patients with cirrhosis who have relatively normal liver function.

Biliary Tract Diseases↗
PubMed1985

The effects of hyperthermia on vascular permeability in experimental liver metastasis.

The effects of hyperthermia on vascular permeability in Walker carcinosarcomas and host liver tissue were studied in Sprague-Dawley rats. A quantitative Evans blue technique was used to measure permeability. With tumors heated to 40 degrees C, a nontherapeutic level, no changes in tumor vascular permeability as compared to control levels were noted. However, with tumors heated to 43 degrees C, within the therapeutic range of hyperthermia, significant rises in tumor vascular permeability occurred. Permeability was increased at both time periods studied, 30 minutes and 6 hours after hyperthermia and injection of Evans blue. These changes are similar to those seen after physical damage from freeze-thaw. It is likely that alterations in tumor microcirculation play a role in the therapeutic effect of intense hyperthermia.

Animals↗
PubMed1985

Consequences of intraperitoneal bile: bile ascites versus bile peritonitis.

Recent experience with patients with bile ascites and bile peritonitis prompted a review of other case histories in the medical literature of these conditions. The clinical courses of 24 patients with bile ascites and 34 with bile peritonitis were reviewed. Bile ascites occurred most often as a postoperative complication of biliary tract operations and also occasionally after trauma. Clinical signs were minimal except for abdominal distention, and operations were delayed for an average of 30 days. Peritoneal fluid was sterile in the 11 patients studied. In contrast, bile peritonitis occurred most commonly after spontaneous perforation of the gallbladder or hepatic ducts but also after trauma. All patients had severe signs of peritoneal irritation, and operation was performed earlier, at a mean of 4 days after onset of symptoms. Of 11 patients with specimens of their peritoneal fluid cultured, 6 had sterile fluid and 5 had bacteria. Although both bile salt concentration and bacteria have been implicated in the development of bile peritonitis rather than bile ascites, our understanding of the mechanisms involved is still incomplete.

Adolescent↗
PubMed1985

The blood supply of experimental liver metastases. VIII. Increased capillary blood flow within liver tumors with administration of epinephrine.

Capillary blood flow has been studied with a laser doppler probe in normal liver tissue and within Walker carcinosarcoma tumors implanted in the livers of rats. Epinephrine, in doses from 1 to 100 micrograms injected as a bolus into the portal system caused immediate significant rises in tumor capillary blood flow. These effects lasted approximately 1 minute and were followed by secondary decreases in flow. Aortic blood pressures rose with epinephrine administration and remained elevated for periods longer than the increase in tumor capillary flow. The effects of epinephrine on liver capillary flow were dose related; doses of 5-10 micrograms caused a decreased flow, 3 micrograms produced a biphasic response, and 1 microgram resulted in an increase in flow. It is concluded that epinephrine produces a short but significant increase in capillary blood flow within the central parts of these tumors, in areas previously considered "avascular".

Animals↗
PubMed1985

Survival and short-term morbidity of the premature neonate.

Obstetric decisions regarding premature (23 to 32 weeks' gestation) infants must be based on gestational age. However, most reports of the survival of premature infants are based on birth weight. The present report relates the perinatal survival and morbidity of 105 newborns to the obstetric gestational dating criteria between 23 and 32 weeks' gestation. Gestational age was determined from at least four obstetric criteria including the first day of the last menstrual period, early pelvic examination, the earliest auscultation of fetal heart tones with a fetoscope, fundal height measurements in centimeters between 20 and 30 weeks' gestation, and sonographic gestational age measurements. At 23 to 26 weeks' gestational age, nine (39%) of 23 neonates survived. Five of nine survivors had moderate to severe intracranial hemorrhage, three had moderate to severe bronchopulmonary dysplasia, and three had moderate to severe retrolental fibroplasia. At 27 to 29 weeks' gestational age, 25 (93%) of 27 neonates survived. Of the 25 survivors, three had moderate to severe intracranial hemorrhage, one had moderate to severe bronchopulmonary dysplasia, and one had severe retrolental fibroplasia. At 30 to 32 weeks' gestational age, 52 (95%) of 55 neonates survived. Three of the 52 (6%) survivors had serious neonatal morbidity consisting of moderate to severe intracranial hemorrhage (three neonates) and moderate to severe bronchopulmonary dysplasia (one neonate). Thus, ten of 34 (29%) survivors between gestational ages of 24 to 29 weeks had a serious morbidity versus only three of 52 (6%) survivors between 30 to 32 weeks' gestation (P less than .01).

Bronchopulmonary Dysplasia↗
PubMed1984

Pulmonary interstitial emphysema in the premature baboon with hyaline membrane disease.

During experiments designed to develop an appropriate ventilatory strategy for high-frequency ventilation (HFV) in the premature baboon with hyaline membrane disease (HMD), we observed the development of pulmonary interstitial emphysema (PIE). Four study groups of 5 animals each received positive-pressure ventilation and positive end-expiratory pressure (PPV/PEEP) or HFV and 1 of 3 sighing techniques. Pathologically, all animals ventilated with PPV/PEEP or HFV with a carefully controlled intermittent sigh developed dilatation of the distal conducting airway and alveolar duct, with poorly expanded pulmonary saccules. The imposition of a sigh with inappropriate timing or excessive volume ruptured the dilated airway walls and caused interstitial air to accumulate. This was evident from the location of striking dilation of the distal airways and pseudocysts in areas of atelectasis. Thus, early in the course of HMD when saccular aeration is minimal, the pathogenesis of PIE is related to airway rather than alveolar rupture.

Animals↗
PubMed1984

High-frequency ventilation compared to conventional positive-pressure ventilation in the treatment of hyaline membrane disease in primates.

High-frequency ventilation (HFV) has been suggested as an alternative to conventional positive-pressure ventilation (PPV) in the treatment of infants with hyaline membrane disease (HMD). Using a previously validated primate model of HMD, 15 baboon fetuses were delivered at 75% of gestation and randomly assigned to 1 of 3 ventilator treatment groups: PPV, HFV delivered by an oscillator (HFO), or HFV delivered by a flow interrupter (HFFI). All animals had clinical and radiographic evidence of HMD. At 96 h of life, all animals were sacrificed and clinical and pathologic findings were analyzed. During the first 10 h of the experiment, the HFO animals required higher mean proximal airway pressures than either the HFFI or PPV groups. However, both the HFFI and HFO animals had higher PaO2/PAO2 ratios than the PPV controls, suggesting earlier saccular recruitment. Thus, HFV is as effective as PPV in the treatment of HMD in baboons. Whether it will decrease the risk of bronchopulmonary dysplasia is not known.

Animals↗
PubMed1984

The blood supply of experimental liver metastases. VII. Further studies on increased tumor vascularity caused by epinephrine.

The effects of epinephrine on the vascularity of tumors within the liver of rats were studied by simultaneous injection of Microfil into the arterial and portal systems. A marked increase in perfusion of capillary-sized vessels within the central portions of the tumor was observed in both induced hepatomas and implanted Walker carcinosarcoma tumors. In studies with implanted tumors, the effect of epinephrine on enhancing vascularity internally was eliminated by the alpha adrenergic block agent phenoxybenzamine, but was not affected by the beta adrenergic blocking agent propranolol.

Animals↗