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Biomedical subjects

M M Knudson

Publications and source records attributed to M M Knudson.

35 records · Page 2Linked to original sources
PubMed1997

Use of tissue oxygen tension measurements during resuscitation from hemorrhagic shock.

BACKGROUND: Tissue oxygen tension can be measured directly in selected organ beds, and these measurements may be more sensitive in assessing the adequacy of resuscitation than global physiologic parameters. We hypothesized that heart tissue oxygen tension would be an important marker for the severity of ischemic insult to the heart during hemorrhagic shock. We further hypothesized that gut oxygen tension measured in the jejunum would prove to be a better measure of splanchnic hypoperfusion than intramucosal pH (pHi). METHODS: Tissue oxygen probes were inserted directly into the myocardium of the left ventricle and into the lumen of the proximal jejunum in 10 anesthetized swine. A pHi catheter was introduced into the stomach. The animals were subjected to a controlled hemorrhage of 50% of estimated blood volume. Gut and cardiac oxygen were monitored continuously during hemorrhage and resuscitation, which was performed with shed blood and crystalloid. RESULTS: While gut O2 and pHi trended together, we were unable to establish a correlation between changes in these two variables during hemorrhage and resuscitation. Heart PO2 decreased significantly during hemorrhage, but surpassed baseline values after resuscitation, a finding not seen in gut PO2. No standard physiologic variables reliably predicted changes in heart PO2 during these experiments. CONCLUSIONS: Tissue oxygen tensions measurements are highly responsive to changes induced during graded hemorrhagic shock and resuscitation. Gut PO2 and pHi appear to be measuring different physiologic processes in the gastrointestinal tract. The compensatory ability of the heart far exceeds that of the gut after ischemic insult. This hemorrhagic shock model appears feasible for the study of various methods of resuscitation.

Animals↗
PubMed1996

Infant survival after cesarean section for trauma.

HYPOTHESIS: Emergency cesarean sections in trauma patients are not justified and should be abandoned. SETTING AND DESIGN: A multi-institutional, retrospective cohort study was conducted of level 1 trauma centers. METHODS: Trauma admissions from nine level 1 trauma centers from January 1986 through December 1994 were reviewed. Pregnant women who underwent emergency cesarean sections were identified. Demographic and clinical data were obtained on all patients undergoing a cesarean section. Fetal distress was defined by bradycardia, deceleration, or lack of fetal heart tones (FHTs). Maternal distress was defined by shock (systolic blood pressure < 90) or acute decompensation. Statistical analyses were performed. RESULTS: Of the 114,952 consecutive trauma admissions, more than 441 pregnant women required 32 emergency cesarean sections. All were performed for fetal distress, maternal distress, or both. Overall, 15 (45%) of the fetuses and 23 (72%) of the mothers survived. Of 33 fetuses delivered, 13 had no FHTs and none survived. Twenty infants (potential survivors) had FHTs and an estimated gestational age (EGA) of greater than or equal to 26 weeks, and 75% survived. Infant survival was independent of maternal distress or maternal Injury Severity Score. The five infant deaths in the group of potential survivors resulted from delayed recognition of fetal distress, and 60% of these deaths were in mothers with mild to moderate injuries (Injury Severity Score < 16). CONCLUSIONS: In pregnant trauma patients, infant viability is defined by the presence of FHTs, estimated gestational age greater than or equal to 26 weeks. In viable infants, survival after emergency cesarean section is acceptable (75%). Infant survival is independent of maternal distress or Injury Severity Score. Sixty percent of infant deaths resulted from delay in recognition of fetal distress and cesarean section. These were potentially preventable. Given the definition of fetal viability, our initial hypothesis is invalid.

Adolescent↗
PubMed1996

Status of nonoperative management of blunt hepatic injuries in 1995: a multicenter experience with 404 patients.

INTRODUCTION: Nonoperative management is presently considered the treatment modality of choice in over 50% of adult patients sustaining blunt hepatic trauma who meet inclusion criteria. A multicenter study was retrospectively undertaken to assess whether the combined experiences at level I trauma centers could validate the currently reported high success rate, low morbidity, and virtually nonexistent mortality associated with this approach. Thirteen level I trauma centers accrued 404 adult patients sustaining blunt hepatic injuries managed nonoperatively over the last 5 years. Seventy-two percent of the injuries resulted from motor vehicle crashes. The mean injury severity score for the entire group was 20.2 (range, 4-75), and the American Association for the Surgery of Trauma-computerized axial tomography scan grading was as follows: grade I, 19% (n = 76); grade II, 31% (n = 124); grade III, 36% (n = 146); grade IV, 10% (n = 42); and grade V, 4% (n = 16). There were 27 deaths (7%) in the series, with 59% directly related to head trauma. Only two deaths (0.4%) could be attributed to hepatic injury. Twenty-one (5%) complications were documented, with the most common being hemorrhage, occurring in 14 (3.5%). Only 3 (0.7%) of these 14 patients required surgical intervention, 6 were treated by transfusions alone (0.5 to 5 U), 4 underwent angio-embolization, and 1 was further observed. Other complications included 2 bilomas and 3 perihepatic abscesses (all drained percutaneously). Two small bowel injuries were initially missed (0.5%), and diagnosed 2 and 3 days after admission. Overall, 6 patients required operative intervention: 3 for hemorrhage, 2 for missed enteric injuries, and 1 for persistent sepsis after unsuccessful percutaneous drainage. Average length of stay was 13 days. Nonoperative management of blunt hepatic injuries is clearly the treatment modality of choice in hemodynamically stable patients, irrespective of grade of injury or degree of hemoperitoneum. Current data would suggest that 50 to 80% (47% in this series) of all adult patients with blunt hepatic injuries are candidates for this form of therapy. Exactly 98.5% of patients analyzed in this study successfully avoided operative intervention. Bleeding complications are infrequently encountered (3.5%) and can often be managed nonoperatively. Although grades IV and V injuries composed 14% of the series, they represented 66.6% of the patients requiring operative intervention and thus merit constant re-evaluation and close observation in critical care units. The optimal time for follow-up computerized axial tomography scanning seems to be within 7 to 10 days after injury.

Adolescent↗
PubMed1996

Use of low molecular weight heparin in preventing thromboembolism in trauma patients.

OBJECTIVE: To investigate the safety and effectiveness of low molecular weight heparin (LMWH) in preventing deep venous thrombosis (DVT) in high-risk trauma patients, compared with mechanical methods of prophylaxis. DESIGN: A prospective randomized trial conducted over a 19-month period in an urban, academic trauma center. METHODS: All trauma patients with the following risk factors for the development of DVT were considered for enrollment in this study: any injury with an Abbreviated Injury Scale score > or = 3; major head injury (Glasgow Coma Scale score < or = 8); spine, pelvic, or lower extremity fractures; acute venous injury; or age > 50 years. After a screening venous duplex examination, the patients were assigned to a Heparin versus No-Heparin group, depending upon the presence of injuries precluding the use of heparin. In the Heparin group, the patients were then randomized to receive either LMWH or optimal mechanical compression (defined as bilateral sequential gradient pneumatic compression (SCD) or, in the presence of lower extremity injuries precluding the use of the SCD, the arteriovenous impulse (AVI) compression system). All the patients in the No-Heparin group received optimal compression. Enrolled patients underwent sequential duplex examinations every 5 to 7 days until discharge. RESULTS: Of the 487 consecutive patients initially enrolled in this study, 372 were available for at least the first two duplex examinations and comprise the study population. Only nine (2.4%) patients developed DVT, compared with the predicted 9.1% rate in high-risk trauma patients receiving no prophylaxis (p = 0.037). Of the 120 patients who were randomized to receive LMWH, only one (0.8%) developed DVT. In the SCD group, there were 5 of 199 patients (2.5%) with DVT, and 3 of 53 (5.7%) in the AVI group. One patient with DVT also had clinical symptoms of pulmonary embolism, but there were no deaths secondary to pulmonary embolism. There was one major bleeding complication potentially associated with the use of LMWH. CONCLUSIONS: The administration of LMWH is a safe and extremely effective method of preventing DVT in high-risk trauma patients. When heparin is contraindicated, aggressive attempts at mechanical compression are warranted.

Adult↗
PubMed1995

Extraluminal, transluminal, and observational treatment for vertebral artery injuries.

Injury to the vertebral artery following penetrating trauma is rare and treatment is usually surgical ligation. Recent liberal use of angiography in the evaluation of penetrating neck trauma has identified increasing numbers of patients with this challenging injury. This report describes our recent experience in treating patients with vertebral artery injuries. The purposes of this study were (1) to review the outcome of our patients with vertebral artery injuries, and (2) to develop an approach for managing these patients. Sixteen patients were treated over a 9-year period. Three patients underwent emergent operative exploration for bleeding, three underwent transcatheter embolization alone, and ten were managed conservatively by close clinical observation. No deaths occurred. Ligation was performed for injuries discovered during neck exploration, however, bleeding was sometimes persistent despite proximal control. In our center, where radiological support is readily available, temporary control of bleeding by packing with hemostatic agents allowed subsequent transcatheter embolization of the injured artery. Pseudoaneurysms, arteriovenous fistulae, and extravasations discovered angiographically were usually managed by transcatheter embolization. Patients with vertebral artery narrowings or occlusions were managed by close clinical observation.

Adolescent↗
PubMed1994

Morbidity and mortality following major penetrating liver injuries.

OBJECTIVE: To establish the mortality and morbidity associated with major penetrating liver injuries and to describe the nature and treatment of complications related to these injuries. We postulated that there had been a trend toward less radical initial surgery, as well as an increased utilization of modern imaging techniques in both diagnosing and treating postoperative complications following penetrating liver trauma. DESIGN: A retrospective survey of medical records and radiology files. SETTING: A university trauma center in an urban setting. PATIENTS: Of the 188 patients admitted to our trauma center with penetrating liver trauma between April 1988 and December 1991, 36 had major liver trauma (grades 3 through 5) and are described in this report. MAIN OUTCOME MEASURES: The mortality rate, type of operative treatment, and the nature and treatment of complications for each grade of major liver injury. RESULTS: The mortality rate from major liver injuries was 17%. Surgical techniques employed primarily consisted of the use of hemostatic agents and cautery, simple suturing, direct vessel ligation, and packing. Fifty-two percent of the survivors had major complications related to the liver injury itself, but only two required operative therapy. The remaining patients were successfully treated with interventional radiologic techniques. CONCLUSIONS: The morbidity and mortality following major penetrating liver injuries remain significant. The majority of hepatobiliary complications can be successfully managed without further surgery but require the combined efforts of the surgeon and interventional radiologist.

Abdomen↗
PubMed1994

Mortality factors in geriatric blunt trauma patients.

OBJECTIVE: To examine various clinical factors for their ability to predict mortality in geriatric patients following blunt trauma. DESIGN: In this retrospective study, trauma registries and medical records from three trauma centers were reviewed for patients 65 years and older who had sustained blunt trauma. The following variables were extracted and examined independently and in combination for their ability to predict death: age, gender, mechanism of injury, admission blood pressure, and Glasgow Coma Scale score, respiratory status, Trauma Score, Revised Trauma Score, and Injury Severity Score. SETTING: Three urban trauma centers. PATIENTS: Geriatric trauma patients entering three trauma centers (Stanford [Calif] University Hospital, Vanderbilt University Medical Center, Nashville, Tenn, and Maryland Institute for Emergency Medical Services Systems, Baltimore) following blunt trauma during a 7-year period (1982 to 1989). RESULTS: The Injury Severity Score was the single variable that correlated most significantly with mortality. Mortality rates were higher for men than for women and were significantly higher in patients 75 years and older. Admission variables associated with the highest relative risks of death included a Trauma Score less than 7; hypotension (systolic blood pressure, < 90 mm Hg); hypoventilation (respiratory rate, < 10 breaths per minute); or a Glasgow Coma Scale score equal to 3. CONCLUSIONS: Admission variables in geriatric trauma patients can be used to predict outcome and may also be useful in making decisions about triage, quality assurance, and use of intensive care unit beds.

Abbreviated Injury Scale↗
PubMed1994

Prevention of venous thromboembolism in trauma patients.

Trauma patients are at risk for thromboembolic complications, but effective methods of prophylaxis have not been established for this heterogenous population. In this prospective trial, 400 trauma patients were assigned to one of three groups, depending upon their injuries, and randomized within each group to a treatment mode: Group I: sequential gradient pneumatic leg compression (SCD), low-dose subcutaneous heparin (H), or control (C); Group II: H or C; Group III: SCD or C. Venous duplex ultrasound examinations were performed on admission and weekly thereafter. Of the 251 patients who completed the study, 15 (6%) developed lower extremity venous thrombosis and two additional patients developed pulmonary embolism (one fatal). Significant risk factors associated with the development of thromboembolism included immobilization > 3 days, age 30 years or older, and the presence of pelvic or lower extremity fractures. In patients with neurotrauma who cannot receive heparin (Group III), the SCD was more effective than control in preventing DVT (p = 0.057). Neither H nor SCD appeared to offer protection for the other groups of trauma patients, but surveillance with ultrasound examinations allowed for prompt recognition and treatment of occult deep vein thrombosis.

Adolescent↗
PubMed1994

Death in the operating room: an analysis of a multi-center experience.

To characterize causes of death in the operating room (OR) following major trauma, a retrospective review of admissions to eight academic trauma centers was conducted to define the etiology of death and challenges for improvement in outcome. Five hundred thirty seven OR deaths of 72,151 admissions were reviewed for mechanism of injury, physiologic findings, resuscitation, patterns of injury, surgical procedures, cause of death, and preventability. Blunt injuries accounted for 61% of all injuries, gunshot wounds (GSW) accounted for 74% of penetrating injuries. Sixty two percent of all patients arrived in shock. Average blood pressure (BP) was 52 mm Hg at the scene and 60 mm Hg on admission, with the period of shock > 10 minutes in 74%. Only 56% were resuscitated to a BP > 90 mm Hg before surgery. Average time to the OR was 30.1 minutes and mean best postresuscitation pH was 7.18. Mean best OR temperature was 32.2 degrees C. Recurrent injury patterns judged as the primary cause of patient death included head/neck injury (16.4%), chest injury (27.4%), and abdominal injury (53.4%). Actual cause of death was bleeding (82%), cerebral herniation (14.5%), and air emboli (2.2%). A different strategy for improved outcome was identified in 54 patients with the following conclusions: (1) delayed transfer to the OR remains a problem with significant BP deterioration during delay, particularly following interfacility transfer; (2) staged injury isolation and repair to allow better resuscitation and warming may lead to improved results; (3) combined thoraco-abdominal injuries, particularly with thoracic aortic disruption, often require a different sequence of management; (4) aggressive evaluation of retroperitoneal hematomas is essential; (5) OR management of severe liver injuries remains a technical challenge with better endpoints for packing needed; and (6) resuscitative thoracotomy applied to OR patients in extremis from exsanguination offers little.

Adult↗
PubMed1993

The role of duplex ultrasound arterial imaging in patients with penetrating extremity trauma.

OBJECTIVE: To investigate the role of color-flow duplex ultrasound vascular imaging in screening patients for potential arterial injuries following penetrating trauma of the extremities. DESIGN: In this prospective study, patients with penetrating trauma in proximity to major peripheral vessels but without signs of arterial injury underwent color-flow duplex imaging. Patients with abnormal color-flow duplex examination results were then studied with angiography, and the results of the two studies were compared. In patients who presented with signs of arterial injury, immediate operative exploration and/or angiography was performed. SETTING: An urban trauma center. PATIENTS: Patients entering the trauma center with penetrating trauma between April 1991 and December 1992. RESULTS: Seventy-seven patients with 86 extremity injuries were initially screened with color-flow duplex imaging. Four patients had positive study results, and all injuries were confirmed with angiography (100% true positive). No missed arterial injuries were detected in clinical follow-up. CONCLUSIONS: Color-flow duplex imaging reliably detects occult arterial injuries and may also have a role in following up minor injuries treated without surgery.

Adolescent↗
PubMed1992

Hematuria as a predictor of abdominal injury after blunt trauma.

Among the 1,484 patients included in the Renal Trauma Project with evidence of blunt trauma and hematuria, 160 patients were found to have both hematuria and a significant intra-abdominal injury not related to the genitourinary system. The incidence of abdominal injury generally increased with the degree of hematuria, approaching 24% in patients with gross hematuria. For each category of degree of hematuria, patients with shock had a significantly higher incidence of abdominal injury (p < 0.05) than patients without shock. The incidence of abdominal injury in patients with microscopic hematuria and shock was 29%, and it was 65% for patients with both gross hematuria and shock. All patients with gross hematuria after blunt abdominal trauma and all patients with microscopic hematuria and a history of shock should be evaluated for both urologic and extra-renal abdominal injuries.

Abdominal Injuries↗
PubMed1992

Thromboembolism following multiple trauma.

The true incidence of thromboembolic complications following multiple trauma is unknown, and no method of prophylaxis has been shown to be both safe and effective in managing seriously injured patients. In this prospective study, 113 trauma patients were assigned on admission to receive either low-dose heparin (LDH), (5,000 U subcutaneously every 12 hours) or to wear sequential compression devices (SCDs) as prophylaxis against the development of deep venous thrombosis (DVT). Both groups of patients were serially studied with duplex venous ultrasound imaging to detect thrombus in the veins of the thigh. Ventilation-perfusion lung scans and pulmonary angiograms were performed when pulmonary embolism (PE) was suspected clinically. There were 12 patients who had thromboembolic complications, including 9 of 76 in the SCD group (12%) and 3 of 37 in the LDH group (8%). Five patients had DVT only, four had PE without detectable DVT, and three had both DVT and PE. None of the patients with PE died, and there were no major complications associated with either method of prophylaxis. Compared with the patients who did not develop DVT/PE, those with thromboembolic complications were older (49 +/- 23 vs. 36 +/- 17 years, p less than 0.02), spent more hospital days immobilized (24 +/- 15 vs. 10 +/- 13 days, p less than 0.001), received more transfusions (11 +/- 12 vs. 3 +/- 5 U, p less than 0.001) and had clotting abnormalities on admission, as demonstrated by prolonged PTT values (39 +/- 28 vs. 26 +/- 5 seconds, p less than 0.001). It appears that there is an identifiable subgroup of injured patients at highest risk for PE who warrant both prophylaxis and close surveillance for DVT.

Adolescent↗
PubMed1992

Can adult trauma surgeons care for injured children?

Large urban trauma centers care for injured children as well as adults in many areas of the country, but the quality of care in these hospitals has not been evaluated versus that available at pediatric trauma centers. The recent validation of TRISS methodology in pediatric populations allowed us to evaluate the quality of pediatric trauma care being provided in a level I trauma center treating injured patients of all ages. We reviewed the records of 353 injured children (aged 0-17 years) who were admitted to our trauma center over a 30-month period for the following data: demographics, mechanism of injury, initial physiologic status (RTS), surgical procedures required, need for intensive care, nature and severity of the injuries (ISS), and outcome. TRISS analysis allowed us to compare our population with the Major Trauma Outcome Study. Only two of the 21 total deaths (overall mortality, 6%) were unexpected, and there were seven unexpected survivors. One hundred twenty-one patients underwent emergency surgical procedures and 63 required admission to the intensive care unit. The Z scores ranged from +0.32 for the children aged less than 2 years to +3.98 for the older age group (14-17 years). We conclude that the quality of care for pediatric trauma patients admitted to trauma centers that care for patients of all ages compares favorably with national standards. In most areas of the country, improvements in pediatric trauma care will likely come from addressing the special needs of injured children in general trauma centers rather than from developing separate pediatric facilities.

Adolescent↗
PubMed1991

Trauma in pregnancy. Predicting pregnancy outcome.

A multicenter study involving three American College of Surgeons Level 1 trauma centers was undertaken to assess parameters that may predict fetal outcome. The records of 93 injured pregnant patients admitted from April 1, 1985, to March 31, 1990, were reviewed. There were three maternal deaths (3%) (mean Injury Severity Score, 43). Fourteen fetal/neonatal deaths (15%) occurred during the acute care admission period. Of these, eight were fetal deaths (two associated with maternal death), four were cases of elective abortions, and two were neonatal deaths. In general, the maternal physiologic and laboratory parameters assessed failed to accurately predict pregnancy outcome, while Injury Severity Score did differ significantly between patients whose pregnancies were viable (Injury Severity Score = 6.2) and those whose pregnancies were nonviable (Injury Severity Score = 21.6). Unique to this study were the findings that the Glasgow Coma Score also differed significantly in patients with viable (Glasgow Coma Score, 14.5) and nonviable (Glasgow Coma Score, 12.0) pregnancies, while fetal heart rate at admission to the emergency department did not. In this study, the incidence of fetal death was increased following direct uteroplacental fetal injury (100% of cases), maternal shock (67%), pelvic fracture (57%), severe head injury (56%), and hypoxia (33%). The adequacy of noninvasive maternal monitoring in assessing fetal well-being is challenged, and a discussion of diagnostic modalities for assessment for the injured gravida is set forth.

Accidents, Traffic↗
PubMed1990

Nonoperative management of blunt liver injuries in adults: the need for continued surveillance.

Computed tomography (CT) scanning after blunt abdominal trauma has allowed nonoperative management of selected patients with liver injuries. This report describes 52 adult patients with liver injuries who were treated without immediate surgery. Thirty-four of these hepatic injuries were relatively minor (Grade I-II), and 18 were considered major (Grade III-V). Free intraperitoneal blood in small to large amounts was evident on CT in 37 patients. There were no deaths in this series, no major complications, no known missed intra-abdominal injuries, and no delayed hemorrhage. While most liver injuries appear to heal rapidly by serial CT scans, a small percentage of these patients have residual liver defects persisting for several months and may be at risk for future complications.

Adolescent↗
PubMed1976

Progesterone metabolism by the ovary of the pregnant rat: discrepancies in the catabolic regulation model.

The intraovarian site of 20 alpha-hydroxysteroid dehydrogenase activity (20 alpha-OH-SDH) was determined biochemically by measuring enzyme activity in homogenates of the whole ovary, or of isolated ovarian compartments, during the last third segment of pregnancy in the rat. In agreement, with previously reported histochemical evidence, an increase in 20 alpha-OH-SDH activity was observed in isolated corpora lutea, but not in the non-luteal compartment of the ovary. Enzyme activity in corpora lutea was low between days 16 and 22 of pregnancy, but increased markedly (4-6 fold) on day 23. Between days 17 and 20 of pregnancy, serum concentrations of progesterone declined from 130 +/- 3 to 80 +/- 3 ng/ml, while 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OH-P) concentrations declined from 34 +/- 3 to 18.5 +/- 3 ng/ml. Only later, between days 20 and 22 of pregnancy, was a significant decline in serum progesterone concentrations associated with an increase in serum 20 alpha-OH-P concentrations (50 +/- 15 ng/ml at 0800 h and 128.5 +/- 15 ng/ml at 1400 h on day 22). Thus the decline in progesterone concentration late in pregnancy can be explained only partially by conversion of progesterone to 20 alpha-OH-P. Further, a dissociation between changes in enzyme activity and in serum concentrations of 20 alpha-OH-P was also observed. A marked increase in serum levels of 20 alpha-OH-P on day 22 preceded any increase in enzyme activity by at least 10 h, and continued increases in enzyme activity on day 23 were not associated with any steady increase in peripheral 20 alpha-OH-P levels. We conclude from these observations that luteal regression is a more complex phenomenon than the regulation of a single enzyme, 20 alpha-hydroxysteroid dehydrogenase, and may involve regulation of both the synthesis and degradation of progesterone.

20-alpha-Dihydroprogesterone↗