Plasma fibronectin synthesis in normal and injured humans as determined by stable isotope incorporation.

In humans, plasma fibronectin decreases early after operative injury, burn, or trauma, followed by a rapid restoration with a secondary decline typically observed if such patients become septic. We determined the rate of plasma fibronectin and plasma fibrinogen synthesis in normal subjects and injured patients using a stable isotope incorporation technique with [15N]glycine. During a constant 14-h infusion of [15N]glycine, the enrichment of [15N]glycine in both the free plasma glycine precursor pool as well as the urinary hippurate pool was determined; the latter used as an estimate of intracellular hepatic precursor enrichment. [15N]Glycine enrichment in both plasma fibronectin and fibrinogen was also quantified. The synthesis rate (Js/V) expressed in micrograms per milliliter of plasma per hour and the fractional synthesis rate (FSR) expressed as percentage of the plasma pool produced per day were determined. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into urinary hippurate was 35.35 +/- 1.46%/d, whereas the Js/V was 4.45 +/- 0.19 micrograms/ml plasma per h. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into free plasma glycine was 14.73 +/- 0.63%/d, whereas the Js/V was 1.98 +/- 0.09 micrograms/ml plasma per h. Early (2-3 d) after burn injury, fibronectin synthesis was increased (Js/V = 5.74 +/- 0.36; P less than 0.05), whereas later after injury, fibronectin synthesis began to decline (Js/V = 3.52 +/- 0.24; P less than 0.05) based on 15N enrichment of urinary hippurate. In contrast, the Js/V and FSR of plasma fibrinogen, a well-documented acute-phase plasma protein, revealed a sustained elevation (P less than 0.05) after injury in both the trauma and burn patients. Thus, plasma fibronectin synthesis is elevated early postinjury, which may contribute to the rapid restoration of its blood level. However, once fibronectin levels have normalized, the synthesis of plasma fibronectin appears to decline.

Gas exchange after pulmonary fat embolism in dogs.

Gas exchange following moderately severe experimental pulmonary fat embolism was studied in nine dogs. A new method designed to describe the distribution of ventilation-perfusion ratios in the lung was applied before and after intravenous injection of homologous neutral fat. The dose of fat (0.75 ml/kg) was low enough to produce a small but significant decrease in arterial PO2 (mean change of 10 mm Hg) in the first 15 minutes after the embolism but high enough to result in the death of two of the four dogs that were allowed to survive the initial postembolism period. Pulmonary artery pressure and pulmonary vascular resistance both rose significantly within 5 minutes of the fat injection and remained elevated for the 2 hour experimental period. Immediately after the embolism there was an increase in the percentage of the total ventilation going to areas of the lung with ventilation-perfusion ratios between 10 and 100, which usually appeared as a discrete mode in the ventilation distribution. This mismatching of ventilation and perfusion partially resolved within 2 hours after the embolism, as indicated by the gradual disappearance of this population of gas exchanging units with relatively decreased blood flow. At no time within 2 hours after the embolism was there a significant increase in shunt or in ventilation to totally unperfused lung. The gas exchange pattern in the two dogs that subsequently died was indistinguishable from that of the other seven in the immediate postembolism period.

Benefits of intra-abdominal pack placement for the management of nonmechanical hemorrhage.

Massive nonmechanical bleeding following severe liver injury is a difficult problem. Placement of intra-abdominal packs tamponades this nonmechanical bleeding and allows time for correction of various metabolic disturbances (ie, hypothermia, hypotension, acidosis, and coagulopathy). The purpose of this retrospective study was to evaluate the severity of these metabolic disturbances at the time of pack placement and the sequential improvement. It was found that most life-threatening disturbances that developed during the initial operative procedure could be corrected within 18 hours after pack placement and aggressive resuscitation. We concluded that the onset of nonmechanical bleeding and a coagulopathy marks a grave prognosis for the patient, and consideration should be given at this time for pack placement. Patients can then be aggressively resuscitated and returned to the operating room within 24 hours for pack removal if stability is achieved.

Emergency intravenous pyelography in the trauma patient. A reexamination of the indications.

Because of the high incidence of abnormal intravenous pyelograms (IVPs) in victims of blunt trauma undergoing resuscitation, a retrospective review of the Trauma Registry at the University of California, San Diego Medical Center, was undertaken to evaluate the indications for ordering this test. The charts of 216 patients were reviewed, all of whom had formal IVPs (four films) done as an emergency procedure at the time of admission. In this study, special attention was directed toward comparing both the degree of hematuria and the anatomic site of injury with the results of the IVP. A total of 20 renal injuries was detected by IVP. Of these injuries, all but one had hematuria that was greater than 50 red blood cells per high-power field. All but one of the abnormal IVPs were associated with obvious abdominal injuries. The results of the IVP influenced the clinical course of only one patient in the entire series. We conclude that the use of the formal IVP (four films) in the resuscitation phase of treating the multiply traumatized patient be reserved for those patients with penetrating abdominal injury or with hematuria consisting of greater than 50 red blood cells per high-power field. For any major blunt abdominal trauma without significant hematuria, a more simple and rapid study (one-shot IVP) to demonstrate bilateral nephrograms is probably adequate to rule out occult renal artery thrombosis.

Pulmonary and cardiovascular consequences of immediate fixation or conservative management of long-bone fractures.

We randomly assigned patients with multiple trauma who had tibial or femoral fractures to one of two groups--one group received immediate fixation of all fractures, and the second group received conservative orthopedic management, consisting of traction or plaster casts. Studies were conducted twice each day for four days following injury. Mean cardiac index was 1.3 L/min/m2 higher and mean shunt was 5.2% lower in the immediate fixation group compared with the group receiving conservative treatment. Other pulmonary and systemic hemodynamic variables did not differ between the groups. The incidence of fat macroglobules in blood aspirated from the pulmonary capillaries was higher when compared with that in pulmonary arterial blood but was not significantly different between the two treatment groups. Platelet count was significantly lower and fibrinogen concentration was significantly higher in the group receiving immediate fixation. We found no diagnostic significance of the incidence of fat macroglobules in samples of blood aspirated from the pulmonary circulation. We conclude that patients receiving immediate fixation had less pulmonary dysfunction following multiple trauma and long-bone fractures.

Continuous measurement of jugular venous oxygen saturation in response to transient elevations of blood pressure in head-injured patients.

Following traumatic brain injury, continuous jugular venous oxygen saturation (SjvO2) measurements have been made and used to assess cerebral oxygenation. Transients of SjvO2 may reflect cerebral blood flow (CBF) changes if measurements are made over a short period of time during which cerebral metabolic rate for oxygen is assumed unchanged. In response to alterations in perfusion pressure, transients of SjvO2 may indicate the extent to which autoregulation has been preserved after injury. The effect of arterial pressure changes on SjvO2 was measured in 14 severely head-injured patients (Glasgow Coma Scale score < 8) within 36 hours of injury. Mean arterial blood pressure (MABP), arterial oxygen saturation, and intracranial pressure (ICP) data were also continuously recorded by a computer at the patients' bedside. The reliability of the SjvO2 oximetry measurements varied among patients, and an average 38% of SjvO2 measurements were off by more than 6% saturation, necessitating recalibration. During periods of satisfactory catheter performance, 120 instances were found in which MABP was elevated more than 8 torr (mean +/- standard deviation: 32 +/- 13 torr) due to endotracheal suctioning. In 94 of these measurements, there was an associated increase in the ICP of 5 torr or more, averaging 16.6 +/- 10.2 torr. The SjvO2 was 0.62 +/- 0.10 before the increase in MABP and rose to a peak of 0.77 +/- 0.10 during the maximum MABP elevation, suggesting increased CBF during the transient hypertension. In 34 of 37 instances of persistent blood pressure elevations lasting for more than 10 minutes (mean 16.0 +/- 8.0 minutes), the SjvO2 elevation persisted (average duration 15.0 +/- 12.4 minutes), suggesting impaired or lost autoregulatory vasoconstriction. The presence or absence of hyperemia was unrelated to the extent of the autoregulation response. Results indicate that SjvO2 rises with increasing perfusion pressure during and after endotracheal suctioning, suggesting a feeble or absent autoregulatory response following traumatic brain injury.

Early complications of airway management in head-injured patients.

Head-injured patients are frequently young, healthy individuals whose excellent medical condition is suddenly altered by trauma. The purpose of this study is to evaluate the early complications of airway management which occur in head-injured patients and to determine if these are different from what has been reported in patients with chronic illnesses (i.e., diabetes, atherosclerosis, or immunosuppression). Chart review of 52 head-injured patients reveals an early complication rate of 61% for endotracheal intubation and 20% for tracheotomy. Discriminant analysis shows that increasing duration of intubation is the most significant factor in predicting airway management complications (P less than 0.008). The incidence of complications seen in head-injured patients is similar to that of the chronically ill. Complications of endotracheal intubation are judged to be more severe than those of tracheotomy. Data from this study supports the early tracheotomy of severely head-injured patients who are likely to require prolonged airway management.

Resource utilization in traumatic brain injury: the role of magnetic resonance imaging.

Cerebral CT scanning is routine in the acute evaluation of traumatic brain injury (TBI) patients. MRI has been reported to identify cerebral lesions better than CT scan. The purpose of this study was to determine whether MRI influenced the acute diagnosis and management of TBI patients. A retrospective medical records review was performed on all TBI patients undergoing cerebral CT scan and MRI admitted to a regional trauma center during a 2-year period. Patient data collected included demography, extent of TBI, CT scan and MRI use, and therapeutic interventions. Forty TBI patients (initial Glascow Coma Scale, 8.8+/-0.7) underwent 79 CT scans and 40 MRIs. Time to initial CT scan was 6.3+/-4.3 hours and time to MRI was 2.9+/-3.1 days. Nine patients (22.5%) had injuries on CT scan but not on MRI, most commonly skull fractures or small subarachnoid hemorrhages. Twenty-four patients (60%) had injuries on MRI but not on CT scan, most commonly corpus callosum shear injuries. There were two cases of child abuse and both had injuries of varying ages identified by MRI, but not CT. All injuries requiring a therapeutic intervention or change in management were identified by CT scan. Magnetic resonance angiography identified one patient with a traumatic internal carotid artery thrombosis. The performance of MRI resulted in additional charges of $75,640 or $3,152/patient identified with a new lesion. Although MRI identifies lesions not evident on CT scan, MRI does not alter management plans and is of limited value in the acute management of TBI. MRI may be of medicolegal benefit in cases of child abuse.

Predictive value of the Glasgow Coma Scale for tracheotomy in head-injured patients.

Patients with severe head trauma often require prolonged intubation and subsequent tracheotomy. The Glasgow Coma Scale (GCS), an indicator of the severity of head injury, may help identify that subpopulation of trauma victims who will ultimately undergo tracheotomy. This retrospective study demonstrates through discriminant analysis that the likelihood of tracheotomy is significantly greater in patients with a GCS rating less than or equal to 7 than it is in patients with a GCS rating greater than 7 (p = .0001). Conversely, the presence of thoracoabdominal or maxillofacial injury is associated with but not predictive of eventual tracheotomy. In the hope of minimizing complications and enhancing the utilization of hospital resources, this study argues for early tracheotomy in patients with a GCS score less than or equal to 7 who do not undergo craniotomy and are otherwise stable.

Reorganization of a burn unit in response to underutilization: a critical assessment.

The incidence of burn injury in the United States has declined over the past few years, resulting in a dramatic decrease in the number of admissions to burn centers. This decrease has generated considerable concern, leading to a variety of proposals to modify burn units to control the cost of inpatient care. In 1986 Albany Medical Center Hospital, a 654-bed regional academic health sciences center, closed its burn unit and implemented a program to manage thermally injured patients in the intensive and progressive care areas of the medical center. A retrospective study was performed to compare patient outcomes and length of stay for the dedicated burn unit and the integrated burn program. Between the year before and the year after this change there was no significant difference in mortality rate, length of stay, or number of positive blood cultures. The relationship between burn severity and length of stay was unaltered by the burn program change. A comparison of data collected just after the change to those collected 2 years later again showed no difference, except that the annual census had dropped more than 50%. The results suggest that burn units can be converted to integrated burn programs without compromising patient care outcomes, although the lack of a cohesive burn team and the unavailability of beds designated for patients with burns ultimately resulted in a deemphasis of the burn program and consequent marked reduction in the number of patients with burns seen in the institution.

Effects of common dead space on inert gas exchange in mathematical models of the lung.

Theoretical gas exchange is compared in lung models having two different types of dead space. In one, the dead space of a lung unit is "personal" and contains gas equivalent in composition to its own alveolar gas; in the other, the dead space is "common" and contains mixed gas from all gas-exchanging units. Formal algebraic analysis of tracer inert gas exchange in two-compartment models shows that values of compartmental ventilation and perfusion can be found that establish one and only one personal dead-space model equivalent for every common dead-space model. When the total dead space and distribution of blood flow and ventilation in the two models are the same, common dead space will always result in improved inert gas elimination. Under these conditions, the amount of improvement is usually greatest when the partition coefficient of the inert gas is between 0.1 and 1.0 and when there is greatest disparity in the ventilation-perfusion ratios (VA/Q). In the inert gas elimination technique that analyzes all dead space as personal, the presence of common dead space consistently causes the recovered VA/Q distributions to be narrower than the actual distributions, but the resultant error is small.

Ventilation-perfusion relationships during hemorrhagic hypotension and reinfusion in the dog.

The inert gas elimination technique was used to estimate pulmonary ventilation-perfusion (VA/Q) mismatching in heparinized, ventilated, anesthetized dogs during a 90-min period of hemorrhagic hypotension (mean arterial pressure 40 Torr) and subsequent reinfusion of the shed blood. Systemic and pulmonary arterial pressures, as well as cardiac output, were similar to those in previously reported studies using this protocol. Mean arterial O2 partial pressure (PO2) fell from 86 to 75 Torr after hemorrhage and rose to a mean value of 78 Torr after reinfusion. The VA/Q distributions showed that a mean of 56.7% of the ventilation was associated with unperfused or poorly perfused (VA/Q greater than 10) regions during hypotension (control 33.7%). After reinfusion, a mean of 47.8% of the ventilation was still directed to lung with little or no perfusion. This could not be explained on a hydrostatic basis, since pulmonary arterial pressure after reinfusion was greater than the control value. Shunt or blood flow to low VA/Q regions did not increase at any time during hemorrhagic hypotension or reinfusion. Microscopic examination of lung tissue revealed extensive leukocyte aggregation that was not seen in control animals. The mean diameter of obstructed pulmonary vessels was 35 microns (range 13.8-59.8 microns). Storing the shed blood in acid-citrate-dextrose instead of heparin had no significant effect on the extent of leukocyte aggregation. We suggest that leukocyte aggregation and margination may be related to the high VA/Q regions seen in these animals.

Effect of local antigen inhalation and hypoxia on lobar blood flow in allergic dogs.

To determine the local pulmonary vascular response to inhaled antigen and alveolar hypoxia in canine asthma, 8 of 42 skin-test-positive dogs were selected from a preliminary study of airway reactivity to antigen challenge with an extract of Ascaris suum. In an anesthetized, open-chest preparation subjected to left cervical vagotomy, the proportion of pulmonary blood flow to the left lower lobe (Q lobe/Q lung) was estimated by an insoluble gas-elimination method. Continuous inhalation of antigen to the left lower lobe caused a transient decrease in Q lobe/Q lung during inspiration of a hyperoxic gas mixture; it did not affect the local hypoxic vascular response. The local decrease in blood flow during antigen challenge was positively correlated with the airway responsiveness determined in the preliminary study. There was no evidence that the decrease in blood flow was caused by a change in airway pressure in the left lower lobe. We conclude that the chemical mediators of asthma caused the vascular response to antigen challenge, but did not abolish the local hypoxic vascular response.

Effect of cardiac index and hematocrit changes on oxygen consumption in resuscitated patients.

Oxygen consumption (Vo2) has been found to depend on oxygen delivery (Do2) following resuscitation from hemorrhage in both humans and animals. The relative influence of blood flow and arterial oxygen (O2) content, the components of Do2, has not been separately assessed. To determine the relative contribution of content and flow, we determined Do2 and Vo2 while making systematic changes in cardiac index (CI) and hematocrit (HCT). Fourteen patients were studied within 36 hr of hypotension from which they were resuscitated to a HCT of 27.9 +/- 0.4% (mean +/- SEM). Following initial hemodynamic measurements, CI was manipulated by changing end expiratory pressure by increments of +/- 5 cm H2O and measurements were repeated. Patients were then transfused overnight to raise their HCT to 36.7 +/- 0.5% and measurements were repeated, varying CI in the same manner. The increase in HCT resulted in significant (P less than 0.05) increases in O2 delivery (+ 130 +/- 33 ml/min/m2), arterial O2 content (+ 3.9 +/- 0.3 vol%), and mixed venous O2 content (+ 3.7 +/- 0.4 vol%). O2 extraction decreased by 6 +/- 1% from 30 +/- 2%. The change in HCT did not alter Vo2 (143 +/- 7 ml/min/m2), CI (3.6 +/- 0.2 L/min/m2), or intrapulmonary shunt (18.1 +/- 1.7%). However, as CI was changed at both levels of HCT, there were changes in Vo2 directly dependent on Do2. We conclude that oxygen consumption in patients resuscitated from hemorrhage may be influenced by oxygen delivery and that this influence is related more to flow than to arterial content.

Transesophageal echocardiography for the initial evaluation of the widened mediastinum in trauma patients.

Traumatic disruption of the thoracic aorta is an injury that is rapidly fatal if not recognized and treated early. Increasingly, transesophageal echocardiography (TEE) is being used to evaluate the thoracic aorta after trauma with reported sensitivity and specificity rates of up to 100%. To confirm these results, we instituted a protocol using TEE as the initial diagnostic study for excluding a ruptured thoracic aorta in patients with widened mediastinum. All TEE studies were done by experienced cardiologists; 96% were done in the trauma receiving area. TEE studies were classified as positive, negative, or indeterminant. Indeterminant studies were those in which the diagnosis of aortic injury could not be excluded based solely on TEE findings. Because we were interested in using TEE as a "definitive" diagnostic modality, indeterminant studies were regarded as positive for our analysis. This protocol was used in 114 trauma patients over a 3-year period. TEE identified five thoracic aortic disruptions--three confirmed by aortography and two by thoracotomy. TEE was read as indeterminant in 17 patients and further investigation with aortography showed no aortic injury in these patients. TEE was negative in 89 patients who had no further evaluation and were subsequently discharged or who died from other injuries. TEE failed to reveal significant lesions in three patients who had aortograms that revealed disruptions requiring thoracotomy. The use of TEE for the definitive diagnosis of ruptured aorta in this series yields a sensitivity of 63% and a specificity of 84%.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of hyperventilation, mannitol, and ventriculostomy drainage on cerebral blood flow after head injury.

Therapies to lower intracranial pressure (ICP) after traumatic brain injury (TBI) include hyperventilation (HV), intravenous mannitol (IM), and cerebrospinal fluid drainage from a ventriculostomy (DV). To determine the effects of these therapies on cerebral blood flow (CBF), fiberoptic oximetry was used to measure jugular venous O2 saturation (SjvO2) as an index of the CBF to cerebral metabolic rate for O2 (CMRO2) ratio after IM (25 g IV for more than 5 min), DV (3 min), or HV (increase respiratory rate by 4) therapy for elevated ICP. Assuming CMRO2 is constant, changes in SjvO2 reflect changes in CBF. Continuous measurements of SjvO2, ICP, blood pressure, arterial O2 saturation, and end-tidal CO2 were obtained in 22 patients with a Glasgow Coma Scale score of 5.3 +/- 0.4 (mean +/- SD) in the first 5 days after TBI. Therapy was initiated a total of 196 times when ICP was > 15 mm Hg for > 5 minutes, and measurements made at 20 minutes after treatment were compared with those made just before. After DV, ICP fell in 90% of the observations by 8.6 +/- 0.7 mm Hg (mean +/- SEM, n = 119); after IM, ICP fell in 90% of the observations by 7.4 +/- 0.7 mm Hg (n = 43); and after HV, ICP fell in 88% of the observations by 6.3 +/- 1.2 mm Hg (n = 14). In patients where ICP fell, SjvO2 increased by 2.49 +/- 0.7% saturation (from 68.0 +/- 1.3%) with IM, but only by 0.39 +/- 0.4% saturation (from 67.2 +/- 0.9%) with DV.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of prehospital surgical cricothyrotomy in trauma patients.

OBJECTIVE: The use of surgical cricothyrotomy (SC) in the prehospital setting is controversial, and the need to teach this procedure to paramedics and intermediate emergency medical technicians remains unclear. The purpose of this study is to define the efficacy, complication rate, and overall survival after SC performed in the prehospital setting. METHODS: In our region, emergency medical technicians receive training in this technique using an animal model with bi-annual updates required. We retrospectively reviewed data in our regional trauma register (15,686 injured patients) for the years 1991-1995. RESULTS: Prehospital emergency airway intubation was required in 376 patients, 56 of whom received SC. The primary indications for SC were facial fractures and deformities (32%) and blood in the airway (30%). In 79% of the patients requiring SC, attempted orotracheal intubation prior to SC was unsuccessful, with a mean of 1.9 attempts per patient. SC was judged to provide an adequate airway in the field in 89% of attempts. Complications at the scene included six failed attempts, one case of excessive bleeding, and one adverse patient reaction (agitation). When patients arrived at the trauma center, the SC was judged to be acceptable in 64%, whereas 16% were functioning with some question of adequacy and required airway manipulation (most commonly a mainstem bronchial intubation). Overall survival to hospital discharge was 27%; however, survival to emergency department discharge (an indicator of emergency airway adequacy) was 62%. Using TRISS methodology, there were five unexpected survivors and six unexpected deaths. Only three patients were discharged with a "good neurologic recovery." CONCLUSION: (1) Prehospital SC can be performed effectively with few complications after training on animal models (2) Good neurologic outcome is rare after the use of this procedure. (3) Although it is effective, clear indications must be developed and followed for the prehospital use of SC.

Use of an Objective Structured Clinical Examination (OSCE) for the assessment of physician performance in the ultrasound evaluation of trauma.

BACKGROUND: A reliable means of assessing physician competency in performing ultrasound (US) is critical for training and credentialing. Objective Structured Clinical Examinations (OSCE) have been used successfully to assess clinical competency in other areas of surgical education but have not been applied previously to trauma ultrasound training. The objectives of this study were to assess physician performance in the focused abdominal sonography in trauma (FAST) examination by using a specifically designed OSCE, and to determine whether the OSCE detects differences in two determinants of competency (knowledge acquisition and clinical interpretation skills). METHODS: Eighty-two physicians in surgery (n = 49) and emergency medicine (n = 33) at a Level I trauma center were evaluated. All participated in a FAST course consisting of didactic sessions on US physics, indications, and technique, FAST examination videos, and a hands-on session with human models. The OSCE consisted of two parts: written examination that assessed factual knowledge, and videotape of real-time US examinations that assessed interpretation skills. The OSCE was administered before and after the FAST course. RESULTS: Significant improvements in postcourse OSCE scores were observed for factual knowledge (52.5 +/- 2.0 vs. 87.5 +/- 1.1, p < 0.001) and interpretation skills (27.2 +/- 1.4 vs. 62.9 +/- 1.3, p < 0.007). Scores for US interpretation were significantly lower than those for factual knowledge at both precourse (27.2 +/- 1.4 vs. 52.5 - 2.0, p < 0.001) and postcourse (62.9 +/- 1.3 vs. 87.5 +/- 1.1, p < 0.01). No performance differences were observed between surgeons and emergency medicine physicians and no effect of training level on test scores was observed. CONCLUSION: Knowledge acquisition and US interpretation skills can be assessed reliably with a specifically designed OSCE. Although both skills improved after participation in a FAST course, US interpretation scores were consistently lower than those for factual knowledge. This study supports the use of the objective structured clinical examination in both the design of ultrasound teaching programs and the assessment of physician competency.