Comparison of Maxon suture with Vicryl, chromic catgut, and PDS sutures in fascial closure in rats.

Two hundred ten rats were randomized into one of five study groups to compare standard absorbable sutures with a new synthetic absorbable suture. We evaluated Maxon (polyglyconate), Vicryl (polyglactin), chromic catgut (catgut), and PDS (polydioxanone) with respect to tissue inflammatory reaction, knot security, suture tensile strength, and suture absorption. The results indicate that Maxon and PDS elicited a lower degree of chronic inflammation when compared with Vicryl and chromic catgut. The tensile strengths of Maxon and Vicryl significantly exceeded those of PDS and chromic catgut during the critical period of wound healing. Maxon and PDS retained a larger percentage of tensile strength during the long postoperative period, whereas Vicryl and chromic catgut were mostly absorbed. Maxon is an excellent addition to the armamentarium of the gynecologic surgeon.

Evaporation versus iced gastric lavage treatment of heatstroke: comparative efficacy in a canine model.

We compared the speed of cooling and treatment efficacy for evaporative cooling vs. iced gastric lavage in a canine heatstroke model. Nine random-source, mongrel dogs were anesthetized, shaved, and internally heated until the core temperature reached 43.0 degrees C. The animals were then randomly assigned to be cooled to 37 degrees C either by iced (1 degree C) tap water gastric lavage (n = 5200 ml/min) through a large (32-Fr) orogastric tube, or by spraying with tap water (n = 4, 15 degrees C, 12 L/min) before a large fan blowing room temperature air (23 degrees C) across the dog at 0.5 m/sec from a height of 50 cm. Temperatures were monitored by thermocouples in both tympanic membranes and the pulmonary artery. BP, pulse, and cardiac output were measured every 5 min. Evaporative cooling was twice as fast as iced gastric lavage (0.16 +/- .05 degree vs. 0.08 +/- .01 degree C/min X m2, p less than .01). Animals in the evaporatively cooled group also experienced a quicker and more complete return to baseline cardiac indices than the lavage-treated group. Moreover, all animals treated with evaporation survived and were neurologically intact 48 h later, while only one lavage-treated dog was neurologically intact over the same period. The others in the lavage group died one hour after cooling (n = 1), were grossly ataxic (n = 1), or were persistently comatose (n = 2). A simple evaporative cooling technique, readily available in the emergency department, appears to be the most rapid and effective means for cooling and treating heatstroke in the dog.

Rewarming in accidental hypothermia: radio wave versus inhalation therapy.

Anesthetized random-source dogs were cooled by refrigeration (3 C) to a stable core temperature of 25 C, and subsequently were rewarmed with warm, humidified inhalation (43 C, 450 mL of minute ventilation per kilogram) or radio frequency induction hyperthermia (4 to 6 watts/kg). The mean time required for core rewarming to 30 C was 231 +/- 3 minutes for warm, humidified ventilation and 106 +/- 32 minutes for radio wave therapy (P less than .01). These data suggest that radio wave heating is a more rapid noninvasive therapy for core rewarming of accidental hypothermia.

Rewarming in immersion hypothermia: radio-wave and inhalation therapy.

Anesthetized random source dogs were cooled by ice water immersion (1 degree C) to a stable core temperature of 25 degrees C, and subsequently rewarmed with warm humidified inhalation (43 degrees C, 450 cc of min ventilation/kg), radio wave induction hyperthermia (4-6 W/kg) or both therapies simultaneously. The mean time required for core rewarming to 30 degrees C was 262 +/- 29 min for humidified ventilation, 68.5 +/- 6 min for radio wave therapy (P less than 0.01), and 74.8 +/- 12 for both therapies combined (P less than 0.3 vs. radio wave). There was no tissue damage with these protocols. These data suggest radio wave heating alone is the most rapid non-invasive method for core rewarming in immersion hypothermia.

Effect of induced oligohydramnios on fetal lung development.

To investigate the impact of oligohydramnios on fetal growth, development, and lung function, amniotic fluid was shunted from alternate gestational sacs into the maternal peritoneal cavity at 23 days' gestation in the fetal rabbit. Uninstrumented fetuses served as controls. Oligohydramnios was confirmed at the time of planned cesarean delivery on either day 26 or 28. Fetuses subjected to prolonged oligohydramnios had significantly decreased body weight at 26 (p = 0.002) and 28 days (p = 0.007). Similarly, lung weight was decreased at 26 (p = 0.02) and 28 days (p = 0.005). There was a trend toward decreased maximum lung volume for instrumented fetuses at 28 days (p = 0.07). Deflation limbs of the pressure-volume curves revealed significantly increased air trapping for instrumented fetuses at 28 days. These studies suggest not only a detrimental effect of oligohydramnios on fetal body and lung weight but also a beneficial effect of premature rupture of membranes on fetal lung function. Analysis of phospholipid and histologic changes is currently under way.

Combined high-frequency jet ventilation in a meconium aspiration model.

To evaluate the effectiveness of high-frequency jet ventilation (HFJV) in the treatment of meconium aspiration, 28 puppies were assigned randomly to one of three ventilator techniques. After aspiration of 4 ml/kg of 20% meconium and baseline measurements on conventional ventilation (CV), the animals were ventilated for 6 h with either CV, HFJV, or HFJV combined with slow conventional ventilation (combined HFJV). Arterial and mixed venous blood gases, systemic and pulmonary arterial pressures, pulmonary capillary wedge pressure, and cardiac output were measured. Combined HFJV proved superior to the other two techniques, resulting in significantly better oxygenation and ventilation at a lower mean airway pressure (Paw). Oxygenation with standard HFJV was comparable to CV, producing Paw and PCO2 values intermediate between those of CV and combined HFJV. There were no significant intergroup differences in cardiac output or the incidence of pneumothorax. Improved gas exchange was attributed to alveolar recruitment and prevention of atelectasis. Alteration of the distribution and/or clearance of meconium may also be important.

Controlled comparison of radio wave regional hyperthermia and peritoneal lavage rewarming after immersion hypothermia.

Anesthetized random source dogs were cooled by ice-water immersion to a stable core temperature of 25 degrees C and subsequently rewarmed with normal saline peritoneal lavage (43 degrees C, 175 ml/kg/hr) or radio frequency electromagnetic-induced regional hyperthermia (4-6 watts/kg). The mean time required for core rewarming to 30 degrees C was 183 +/- 79 minutes for lavage and 58 +/- 13 minutes for radio wave therapy (p less than 0.01). There was no evidence of tissue damage with either modality. These data suggest radio wave regional hyperthermia is superior to peritoneal lavage for core rewarming of rapidly induced immersion hypothermia.

Button battery ingestion: assessment of therapeutic modalities and battery discharge state.

Button batteries immersed in a simulated gastric environment (0.1N hydrochloric acid) demonstrated less crimp dissolution (corrosion of the metal can) after the addition of neutralizing doses of eight of nine antacids tested. Of 64 ingestion episodes in dogs, clinical manifestations of button battery-induced injury were limited to a single animal developing guaiac-positive stools. Endoscopic lesions included only mild gastritis, occurring with a frequency comparable to that observed in dogs prior to battery ingestion. After ingestion blood mercury levels were not significantly elevated. Crimp dissolution was absent in discharged cells, implying a decreased risk of electrolyte leakage or subsequent tissue injury in patients who ingest spent cells. No protective effect of metoclopramide, cimetidine, or magnesium citrate could be demonstrated in the canine model.

Comparison of rewarming by radio wave regional hyperthermia and warm humidified inhalation.

Anesthetized random source dogs were cooled by ice water immersion to a stable core temperature of 25 degrees C and subsequently rewarmed with warm humidified inhalation (43 degrees C, 450 cc of min ventilation X kg-1) or radio-frequency induction hyperthermia (4-6 watts X kg-1). The mean time required for core rewarming to 30 degrees C was 280 +/- 114 min for ventilation and 58 +/- 13 min for radio wave therapy (p less than 0.001). There was no evidence of tissue damage with either modality. These data suggest radio wave heating is superior to warm humidified inhalation therapy for core rewarming of rapidly induced immersion hypothermia.

Controlled comparison of humidified inhalation and peritoneal lavage in rewarming of immersion hypothermia.

Random source dogs were anesthetized and cooled by immersion in ice water to a stable core temperature of 25 degrees C and subsequently rewarmed with either normal saline peritoneal lavage (43 degrees C, 175 ml/kg/h) or warmed humidified inhalation (43 degrees C, 450 ml/kg/min ventilation). The time required for core rewarming to 30 degrees C was 192 +/- 61 minutes for lavage and 331 +/- 96 minutes for inhalation therapy (P less than 0.03). These data suggest that peritoneal lavage is superior to inhalation therapy for core rewarming of rapidly induced immersion hypothermia.

Measure of blood flow by the multiple radioactive microsphere technique in radiated gastrointestinal tissue.

In this study, two different radioactive microspheres were used to measure blood flow of an irradiated segment of small intestine in four dogs before, and 12 days after, irradiation with 2000 rad. The technique and implications are discussed. Using multiple radioactive microspheres, the study demonstrated an increased blood flow in irradiated tissues twelve days after a single dose of 2000 rad. There was also an increase in blood flow to adjoining nonradiated segments of intestine in the same animal. These observations may be of significance in clinical applications of radiation therapy and surgery. A major surgical concern is the impaired healing of irradiated tissue in the immediate postradiation period. The mechanism of this has generally implicated decreases in the perfusion of irradiated tissue. No decrease in blood flow was shown in this study, suggesting that other mechanisms, e.g., stem cell depletion, should be considered. Further studies of this type are recommended to increase understanding of the blood flow in irradiated tissue.

Acquired peripheral arteriovenous fistula in a dog.

A pulsating mass with a continuous bruit was discovered in a dog's flank during routine examination. Based on a history of trauma and clinical signs, an acquired arteriovenous (AV) fistula and a false aneurysm were included in the differential diagnosis. Arteriography confirmed the presence of an AV fistula and outlined the lesion for successful surgical extirpation. Hsitopathologic characteristics of the AV fistula were similar to those in man.

En bloc thoracotomy in miniature swine.

A radical thoractomy technique was developed and used in 4 miniature swine. It provided excellent exposure no postoperative complications.

Inverse effect of chronically elevated blood flow on atherogenesis in miniature swine.

The effect of chronically elevated blood flow on the development of atherosclerosis in miniature swine was studied. Fistulas connecting the right external iliac artery and vein were surgically created in four swine, while three were not fistulated. Pulsed Doppler velocity detection cuffs placed around the abdominal aorta and both iliac arteries of all pigs permitted chronic measurements of blood velocity, blood velocity distributions, and blood flow. All swine were fed an atherogenic diet consisting of 20% beef tallow, 3% cholesterol, and 5% cholic acid for 6 months. This diet elevated the serum cholesterol to values exceeding 500 mg/100 ml. Creation of the arteriovenous fistula (AVF) markedly elevated blood velocity and flow in the abdominal aorta and in the shunted iliac artery. In the shunted animals the aortic blood flow was 42.1 +/- 2.0 ml/sec compared with 17.3 +/- 1.4 ml/sec in the unshunted swine. The velocity distribution pattern across the vessel was also indicative of an elevated wall shear stress. After 6 months, the animals were killed and the arterial vessels examined macroscopically and microscopically for the presence of atherosclerotic lesions. In the shunted pigs, 17 +/- 15% of the lumenal surface was occupied by sudanophilic lesions, whereas 80 +/- 8% of the surface was covered by lesions in the unshunted (control) pigs. From these studies, it is apparent that mechanical factors related to blood flow rates can influence the development of atherosclerotic lesions in swine.

Surgical preparation of miniature swine for atherosclerosis research.

A 2-stage surgical procedure for chronic intestinal, vascular, and lymphatic sampling in miniature swine is described. Cannulas were placed in the jejunum and ileum, followed by a 2nd implantation of indwelling catheters in the portal and hepatic veins, caudal vena cava, abdominal aorta, and cisterna chyli. The techniques used proved that miniature swine can be surgically adapted to meet experimental requirements.

A vascular catheter-implanting device.

A catheter-implanting device (CID) was developed to aid in the placement of vascular catheters in blood vessels located deep in the body cavities, with minimal vascular damage or blood loss.