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Biomedical subjects

S R Petersen

Publications and source records attributed to S R Petersen.

At least 55 records · Page 3Linked to original sources
PubMed1989

The effect of velocity-specific strength training on peak torque and anaerobic rowing power.

This study investigated the effect of low- and high-velocity resistance training on isokinetic peak torque and anaerobic power output. Eighteen male varsity oarsmen were blocked on peak knee extension torque at 3.14 rad s-1 and assigned to a high-velocity resistance training group (HVR), a low-velocity resistance training group (LVR) or a control group. Subjects trained four times a week for 5 weeks. Each training session included three circuits of 12 stations using variable-resistance hydraulic equipment. The HVR training significantly improved peak torque (P less than 0.05) in knee extension and flexion at 2.61, 3.14, 3.66 and 4.19 rad s-1. The LVR training produced significant improvements (P less than 0.05) in peak torque for knee extension and flexion at 0.52, 1.05, 1.57 and 2.61 rad s-1. High positive correlations were found between peak torque and anaerobic power outputs for all groups. However, no significant changes occurred in 15 s power output, average 90 s power output or peak blood lactate in either training group. These results indicate that velocity-specific strength training does not necessarily improve anaerobic power output in a different exercise mode despite the high positive correlation between isokinetic strength and anaerobic power output.

Adult↗
PubMed1989

The influence of high-velocity circuit resistance training on VO2max and cardiac output.

In order to investigate the influence of high-velocity circuit resistance training on maximal aerobic power, maximal stroke volume and cardiac output, and blood lactate removal during recovery, 16 habitually active males were blocked on initial VO2max into either training or control groups. The training group completed two (weeks 1 and 2) or three (weeks 3-6) circuits of 10 variable-resistance hydraulic exercise stations at an exercise: relief ratio of 1:2 on alternate days over six weeks. Angular velocities of movement were maintained at approximately 3.1 rad.s-1. Following training, the VO2max was increased (p less than .01) from 4.32 to 4.68 1.min-1. Maximal stroke volume was increased (p less than .05) from 120 to 129 mL and heart rate response to an absolute submaximal exercise load was decreased (p less than .05) from 153 to 146 beats.min-1. As well, enhanced (p less than .01) removal of lactate from the blood was observed during recovery from exhausting exercise. No changes were observed for control subjects. These results indicate that positive alterations in aerobic and cardiovascular function may be achieved consequent to high-velocity circuit resistance training.

Cardiac Output↗
PubMed1988

Sequencing of endurance and high-velocity strength training.

To compare two sequences of endurance (E) and high-velocity resistance (HVR) training, sixteen male oarsmen were separated into Group ES which trained endurance prior to strength and Group SE which trained strength prior to endurance. The endurance program consisted of up to 60 min a session, five days a week for five weeks. HVR exercise was conducted on 12 stations of variable resistance hydraulic equipment, four sessions per week for five weeks. Endurance training significantly improved VO2max and submaximal heart rate and blood lactate responses in both groups regardless of the sequence followed. HVR training improved VO2max in group SE only and had no effect on submaximal response to exercise. Peak torque increases for knee extension and flexion with HVR training were greater in group SE than group ES. These results show that organizing strength and endurance training into sequential programs can influence the physiological adaptation to training.

Adult↗
PubMed1987

Effects of enteral vs parenteral nutrition on reticuloendothelial function.

Previous investigations have shown that animals maintained with enteral nutrition are better able to survive an intraperitoneal bacterial challenge than animals receiving parenteral nutrition. The aim of this study was to assess the effects of enteral and parenteral nutrition on reticuloendothelial function. Eighteen enteral-fed male Sprague-Dawley rats had access to a standard hyperalimentation solution via a sipper tube ad libitum. Seventeen parenteral-fed animals received the same solution at an infusion rate determined by the volume ingested by the pair-fed enteral animals. All animals had central venous catheters. After 12 days, reticuloendothelial function was assessed by measuring the clearance rate (K) and the organ distribution of intravenous 51Cr-labeled sheep red blood cells and by plasma fibronectin levels. Nutritional status was assessed by body weight and nitrogen balance. K values in enteral and parenteral animals were similar (0.110 +/- 0.011 and 0.140 +/- 0.012, respectively, mean +/- SEM) as were plasma fibronectin levels (196 +/- 22 and 228 +/- 15 micrograms, respectively). Organ distribution of the 51Cr-labeled sheep red blood cells was the same in both groups. Nitrogen balance and body weights were also similar in both groups. These data demonstrate that in this experimental model enteral nutrition and parenteral nutrition were equally effective at maintaining reticuloendothelial function and nutritional status.

Animals↗
PubMed1985

Management of injuries to the porta hepatis.

The management of injuries to the porta hepatis is challenging and controversial. Although definitive, anatomic reconstruction of injured ductal or vascular structures is optimal, porta hepatis injuries are universally accompanied by injuries to other organs (3.6 in this series), which often precludes initial repair. Moreover, frequent injury to the inferior vena cava, aorta, or other major blood vessels in addition to the structures of the porta hepatis results in these injuries being treated in conjunction with exsanguinating hemorrhage. For that reason, control of hemorrhage is the initial management priority, with the initial operation requiring expeditious, if less than anatomically exact, operations. Eighteen of 31 patients survived porta hepatis injury. Hepatic artery injuries were treated by ligation. Complex injuries to bile ducts frequently required enteric-ductal anastomoses as secondary procedures. Of 29 patients with portal vein injuries, six were treated by ligation, 22 by lateral repair, and one with splenic vein interposition graft. As in earlier reports, the structure of the porta hepatis associated with the highest morbidity and mortality rates when injured was the portal vein.

Abdominal Injuries↗
PubMed1984

The acquisition of muscular strength: the influence of training velocity and initial VO2 max.

To examine velocity specific training and to determine if VO2 max is related to the increase in muscular strength and power, 12 elite male swimmers (means age = 18.8 years) were blocked on VO2 max and assigned high intensity, high velocity training. Subjects performed 2 or 3 circuits of two 20s sets at each of six variable resistance stations at a work relief ratio of 1:3. Subjects trained four times weekly, for five weeks. Loads were set to achieve limb velocities of approximately 180 degrees X s-1. Increases (p less than 0.001) in all knee peak torques at 180 degrees X s-1 were observed. A decrease (p less than 0.02) was noted in right knee extension at 30 degrees X s-1, while other peak torques at that velocity remained constant. Anaerobic power increased (p less than 0.001) across the training programme. No differences in the magnitude of training effects were observed between High or Low Aerobic groups with the exception of right knee extension at 180 degrees X s-1, where the Low Aerobic group demonstrated the greater improvement (p less than 0.009). In conclusion, this type of velocity specific training can elicit improvements in peak muscular torques at or near the training velocity. Apparently, initial VO2 max did not limit the attainment of muscular strength and power.

Adolescent↗
PubMed1984

Duodenal trauma: experience of a trauma center.

In the past decade 93 patients with duodenal injury were treated at a trauma center. By chart review, the age, sex, mechanism of injury, time to initial exploration (and the reason for delay), laboratory results, associated injury, extent of duodenal injury, operative repair, use of drains and tube decompression, morbidity, and cause of death were tabulated in order to improve management of these injuries. Of 87 patients surviving until the time of operative repair 73% required no repair (four) or primary closure (59). The remainder had either resection with primary anastomosis (ten), diverticulization (12), or pancreaticoduodenectomy (two). All patients with penetrating trauma were immediately explored. Patients with blunt trauma were explored on the basis of the judgment of house staff and faculty. Overall mortality was 18%. Significant morbidity occurred in 49% of survivors. This urban experience was heavily weighted toward penetrating injury. In this group early death usually resulted from associated vascular injuries. Blunt duodenal injury was less frequently associated with immediate exsanguination. Mortality associated with blunt duodenal injury was usually the result of delayed diagnosis. In blunt duodenal trauma peritoneal lavage is not diagnostic and may often be misleading; in this series 50% of lavages were false negatives. Blunt duodenal trauma, particularly when combined with pancreatic injury or delayed repair, was a lethal combination. A high index of suspicion and aggressive diagnostic evaluation (CT contrast study/amylase) in the emergency department is required in equivocal cases to avoid morbidity and mortality.

Adolescent↗
PubMed1981

Splenectomy for immune thrombocytopenic purpura.

Of 481 splenectomies performed at the University of Utah, Salt Lake City, 78 (16.2%) were for immune (idiopathic) thrombocytopenic purpura (ITP). The mean platelet count prior to therapy was 13,800/cu mm (range, 500 to 80,000/cu mm). All but two patients were initially treated with corticosteroids, and 58.2% responded with an increase in platelets (mean, 77,900/cu mm). The indications for splenectomy included (1) failure to respond to steroids (33.8%); (2) inability to taper steroids (52.1%); (3) recurrent ITP (5.6%); and (4) miscellaneous (8.5%). There was one death following splenectomy, and the postoperative morbidity was 14.1%. Complete remission occurred in 77.3%, and 84.8% were judged to have benefited from the procedure. The remission rate following splenectomy in patients who responded to preoperative steroids was 93.2%, whereas improvement fell to 68.3% in patients who failed to respond to steroids. This study confirms the benefit of splenectomy for ITP and demonstrates a predictive correlation with response to preoperative preparation with corticosteroids in these patients.

Adolescent↗
PubMed1981

Malnutrition and immunocompetence: increased mortality following an infectious challenge during hyperalimentation.

Malnutrition is associated with an increased susceptibility to infection by altering host defense mechanisms. A number of investigators have demonstrated restoration of in vitro immunocompetence following nutritional repletion with intravenous hyperalimentation. This study was designed to assess in vivo host defense mechanisms following protein depletion and repletion using a septic challenge. Female Fischer rats (150 gm) were fed a regular diet or a 2% agar protein depletion (DEP) diet for 14 days. The rats were then administered an infectious challenge with intraperitoneal injections of 7 ml/kg of a solution of 10(9) organisms/ml of E. coli with 4 gm% hemoglobin as red cells. Two additional organisms were repleted by regular diet (DEP-Oral) or by an intravenous solution (DEP-TPN) of dextrose-amino acid-lipid (D25 3.75% Aminosyn, 10% Intralipid) for an additional 2-week period, and given the experimental peritonitis challenge. Normal rats challenged with E. coli-hemoglobin adjuvant peritonitis had 66% survival as opposed to 15% survival of protein depleted rats. Protein-depleted (DEP-oral) rats refed with regular diets had a 60% survival which was comparable to normal controls. Rats repleted with intravenous hyperalimentation had a mortality comparable to protein-depleted controls. The data confirm that protein depletion is associated with loss of host defense mechanisms. Although refeeding by regular diet resulted in restoration of host defense, repletion by parenteral nutrition, in this model, did not improve survival.

Adjuvants, Immunologic↗
PubMed1980

The current role of thymectomy for myasthenia gravis.

Myasthenia gravis is an autoimmune disease characterized by muscle weakness and fatigability due to a reduction in available acetylcholine receptors at the neuromuscular junction. Treatment with anticholinesterase drugs and corticosteroids has improved the prognosis for patients with this disease. However, controversy continues concerning the indications for thymectomy. During a 9 year period, 27 patients who underwent thymectomy by median sternotomy were reviewed. Eighty-one percent of these patients benefited from the procedure. Clinical improvement did not correlate with age, sex, duration of symptoms, severity of disease or thymic histology, This suggests that the indications for thymectomy should be liberalized to include most patients with generalized myasthenia who fail to respond readily to conventional medical therapy. The importance of immunosuppression nd plasmapheresis in the therapy of myasthenia gravis awaits further delineation of the immune defect associated with the disease.

Adolescent↗
PubMed1980

Autoregulation of erythropoiesis by 2,3 diphosphoglycerate during hyperalimentation.

Protein depletion in rats is associated with hemoconcentration, diminution of red cell mass, and suppression of erythropoiesis. In a rat model, repletion with standard diets or total parenteral nutrition was associated with gain in body weight and regeneration of red cell mass. Hematocrit values did not reflect the degree of red cell mass diminution associated with protein depletion. Intravenous repletion of normal and protein-depleted rats, unlike oral refed cohorts, was associated with elevated 2,3 diphosphoglycerate (DPG) values and a 'relative anemia.' It is postulated that elevated red cell 2,3 DPG lowers the hypoxic stimulus for erythropoietin production by enhancing oxygen unloading to the tissues, thus partially compensating for the anemia associated with total parenteral nutrition.

Anemia↗
PubMed1979

Septic phlebitis: a neglected disease.

A review of 100 patients with peripheral septic phlebitis revealed that 54 per cent of the cases were due to intravenous catheters and 46 per cent were secondary to drug abuse. Eighty per cent of the involved veins were in the arm or neck. Pain was the most common symptom (83 per cent), with erythema and edema the most common physical signs (63 per cent). Eighty per cent of the causative organisms were gram-positive bacteria, usually Staphylococcus aureus (41 per cent) or Group A streptococcus (20 per cent). Complications were more common if septic phlebitis was due to intravenous therapy than drug abuse. No deaths were directly attributed to septic phlebitis. However, hospital stay after development of septic phlebitis was 14 days with a 56 per cent complication rate. The initial treatment of septic phlebitis should include prompt removal of the intravenous device, antibiotics, heat, and elevation. Because serious complications occur in a significant number of patients, operative excision of the involved vein should be performed if clinical deterioration occurs or if septicemia persists after 24 hours despite conservative therapy.

Arm↗
PubMed1979

Acute acalculous cholecystitis: a complication of hyperalimentation.

In a 5 year period, eight patients in whom acute acalculous cholecystitis developed during intravenous hyperalimentation are reviewed with emphasis on factors contributing to pathogenesis. Gallbladder distention, biliary stasis, and bile inspissation, thought to be important in the pathogenesis of this disease, are enhanced with the use of hyperalimentation, and this potential complication is being seen with increasing frequency in seriously ill or injured patients who are being fed parenterally. In addition to hyperalimentation, sepsis, hypotension, multiple transfusions (more than 10 units), prolonged fasting, and ventilatory support were frequent common denominators. Typical findings of pain, tenderness, and a mass in the right upper abdominal quadrant are infrequent, and the diagnosis rests on a high index of suspicion and ultrasonography. This syndrome may be preventable by the stimulation of gallbladder emptying with intermittent fat ingestion or parenteral infusion of cholecystokinin.

Abdominal Injuries↗
PubMed1979

Management of portal vein injuries.

Injuries to the portal vein are associated with a high mortality because of a high incidence of concomitant injury to surrounding structures and refractory shock. Repair of the portal vein injury is often difficult or impossible because of massive hemorrhage. The key to successful management of a portal vein injury is rapid blood volume resuscitation and obtaining rapid and adequate exposure. The optimal exposure for repair consists of reflection of the hepatic flexure of the colon with mobilization of the root of the mesentery, pancreas, and duodenum. Lateral venorrhaphy is the preferred method of management, but in hemodynamically unstable patients, ligation of the portal vein is an acceptable method of treatment.

Arteriovenous Shunt, Surgical↗
PubMed1979

Morbidity of a negative finding at laparotomy in abdominal trauma.

Although it is undesirable to perform an unneeded laparotomy in patients with abdominal trauma, it is more serious to delay exploration and incur morbidity or mortality. Because a negative finding at laparotomy has a low incidence of complications, early exploration is justified in instances in which intra-abdominal injury is suspected. Although peritoneal lavage for blunt trauma and selective exploration for some stab wounds may reduce the incidence of unnecessary laparotomies, the high incidence of major injury associated with gunshot wounds precludes use of selective exploration as a reasonable policy.

Abdominal Injuries↗
PubMedDate not supplied

Integrated nutritional, hormonal, and metabolic effects of recombinant human growth hormone (rhGH) supplementation in trauma patients.

An anabolic stimulus is needed in addition to conventional nutritional support in the catabolic "flow" phase of severe trauma. One promising therapy appears to be rhGH infusion which has direct as well as hormonal mediated substrate effects. We investigated on a whole-body level, the basic metabolic effects of trauma within 48-60 h after injury in 20 severely injured (injury severity score [ISS] = 31 +/- 2), highly catabolic (N loss = 19 +/- 2 g/d), hypermetabolic (resting energy expenditure [REE] = 141 +/- 5% basal energy expenditure [BEE]), adult (age 46 +/- 5 y) multiple-trauma victims, before starting nutrition therapy and its modification after 1 wk of rhGH supplementation with TPN (1.1 x REE calories, 250 mg N.kg-1.d-1). Group H (n = 10) randomly received at 8:00 a.m. on a daily basis rhGH (0.15 mg.kg-1.d-1) and Group C (n = 10) received the vehicle of infusion. Protein metabolism (turnover, synthesis and breakdown rates, and N balance); glucose kinetics (production, oxidation, and recycling); lipid metabolism, (lipolysis and fat oxidation rates), daily metabolic and fuel substrate oxidation rate (indirect calorimetry); and plasma levels of hormones, substrates, and amino acids were quantified. In group H compared to group C: N balance is less negative (-41 +/- 18 vs -121 +/- 19 mg N.kg-1.d-1, P = 0.001); whole body protein synthesis rate is 28 +/- 2% (P = 0.05) higher; protein synthesis efficiency is higher (62 +/- 2% vs 48 +/- 3%, P = 0.010); plasma glucose level is significantly elevated (256 +/- 25 vs 202 +/- 17 mg/dL, P = 0.05) without affecting hepatic glucose output (1.51 +/- 0.20 vs 1.56 +/- 0.6 mg N.kg-1.min-1), glucose oxidation and recycling rates; significantly enhanced rate of lipolysis (P = 0.006) and free fatty acid reesterification (P = 0.05); significantly elevated plasma levels of anabolic GH, IGF-1, IGFBP-3, and insulin; trauma induced counter-regulatory hormone (cortisol, glucagon, catecholamines) levels are not altered; trauma induced hypoaminoacidemia is normalized (P < 0.05) and 3-methylhistidine excretion is significantly low (P < 0.001). Improved plasma IGF-1 levels in Group H compared with Group C account for protein anabolic effects of adjuvant rhGH and may be helpful in promoting tissue repair and early recovery. Skeletal muscle protein is spared by rhGH resulting in the stimulation of visceral protein breakdown. The hyperglycemic, hyperinsulinemia observed during rhGH supplementation may be due to defective nonoxidative glucose disposal, as well as inhibition of glucose transport activity into tissue cells. The simultaneous operation of increased lipolytic and reesterification processes may allow the adipocyte to respond rapidly to changes in peripheral metabolic fuel requirements during injury. This integral approach helps us to better understand the mechanism of the metabolic effects of rhGH.

Adult↗