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Lisa A. Patterson is the associate director of trauma and the surgical director of the intensive care unit at Miami Valley Hospital.
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The mortality rate for patients with ARDS is as high as 40% to 60%.26 The actual survivability depends on multiple factors, including predisposing conditions, severity of illness, age, comorbid conditions, and, in patients with trauma, severity of the underlying lung injury.57
Sepsis is the most frequently identified risk factor for ARDS; other factors are aspiration of gastric material, severe pneumonia, severe trauma, use of cardiopulmonary bypass, multiple transfusions, fat embolism, and pancreatitis.8 For patients with multiple trauma, factors thought to contribute to the development of ARDS include pulmonary edema due to direct damage to lung parenchyma, multiple transfusions, activation of chemical mediators in response to a systemic inflammatory response syndrome or sepsis, multiple fractures, impaired mucociliary clearance, and immobilization.9
| PATHOPHYSIOLOGY OF ARDS |
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In addition to treatment of the underlying cause of ARDS (eg, pulmonary laceration), mechanical ventilatory support is an integral component of care for patients with this syndrome. The objectives of using mechanical ventilation are to improve gas exchange, relieve respiratory distress, improve pressure-volume relationships, allow lung healing, and avoid complications (ie, barotrauma or oxygen poisoning).8 Other methods of improving oxygenation in patients with ARDS have been investigated, including the effects of prone positioning.
| PHYSIOLOGY OF PRONE POSITIONING |
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In 2001, Gattinoni et al11 found that use of the prone position improved oxygenation in greater than 70% of the instances in which it was used. However, despite an improvement in oxygenation, the mortality rate of patients with ARDS who were placed in a prone position did not differ significantly from that of patients treated in the conventional supine position.
In studies15,16 in which computed tomography was used, pulmonary infiltrates, atelectasis, and collapsed lung regions were preferentially located in the dorsal dependent regions when patients with ARDS were in the supine position. When the patients were rotated into the prone position, infiltrates seem to be redistributed toward the ventral region, thereby reducing intrapulmonary shunting and increasing pulmonary perfusion.17 The increase in ventilation-perfusion ratio most likely was due to the recruitment of previously atelectatic areas by gravitational forces.18
Other possible explanations of the benefit of prone positioning in patients with ARDS include changes in functional residual capacity, shifts in the location of lung water and exudates, and changes in regional diaphragm motion.19 Other areas of research focus on the use of various techniques of ventilator support and the use of surfactant and inhaled nitric oxide in the treatment of ARDS.
Absolute contraindications for prone positioning have not been determined to date. Previous research suggested relative exclusion criteria. In some studies,9,12 exclusion criteria specific to trauma patients were identified as increased intracranial pressure (>25 mm Hg) despite adequate treatment, cervical spine fractures that could not be stabilized, intestinal ischemia, and severe inguinal and abdominal soft-tissue infection. Further exclusion criteria not specific to trauma patients included left ventricular failure, hemodynamic instability, unstable bone fractures (site not mentioned), and/or an active intra-abdominal process (undefined).9,18,20
To date, few investigators have examined the effects of prone positioning in patients with multiple trauma and ARDS. Furthermore, information on the use of prone positioning in patients with open abdominal wounds (due to abdominal decompression or damage-control laparotomy) after blunt abdominal trauma is virtually nonexistent. Offner et al21 reported the use of prone positioning in 4 patients who had closed midline abdominal incisions after exploratory laparotomy. During that study, 2 patients were not treated with prone positioning because they had open abdominal incisions. Offner et al suggest, however, that prone positioning might be possible in patients with open abdominal incisions if an abdominal binder is used.
| BARRIERS TO THE USE OF PRONE POSITIONING |
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Other potential complications associated with use of the prone position include peripheral nerve injuries, skin necrosis, corneal ulceration, abdominal wound dehiscence, and facial edema.12,20,21 Although the potential for skin breakdown is a concern for patients placed either supine or prone, Gattinoni et al11 found that during a 10-day period, the number of new or worsening pressure ulcers per patient was significantly higher in patients placed prone than in patients placed supine. The risks of these and other complications can be minimized, however, by using appropriate preparation and by anticipating potential deleterious events.
Offner et al21 suggest that institutions should develop protocols to standardize placing critically ill patients in the prone position. Such protocols should include indications for use of prone positioning, duration and frequency of prone positioning, and frequency of monitoring respiratory parameters. The protocols should also indicate the minimum number of personnel required to turn a patient, care of patients who are in the prone position, and troubleshooting guidelines for potential complications.
At Miami Valley Hospital, Dayton, Ohio, when a patient is placed in the prone position, a surgical resident and a respiratory therapist are present at the head of the bed to control the airway and ventilator tubes. Additionally, depending on the size of the patient and the remaining equipment, 3 to 5 nursing and ancillary staff members are present.
| METHODS OF PLACING PATIENTS PRONE |
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In 1996, Vollman and Bander14 introduced the Vollman Prone Positioner (Hill-Rom Services Inc, Batesville, Ind). The positioner, a lightweight portable support frame, serves as an anchor for the patients body during the turn and then acts as a cushion device to maintain the abdomen free of restriction while the patient is in the prone position.
Whichever method is chosen, meticulous care of patients and anticipation of complications must be ensured to prevent the dislodgement of critical tubes or catheters.
| CASE STUDIES |
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Case 1
R.B., a 31-year-old man, was admitted to the trauma service after a motor vehicle collision. His injuries included splenic rupture, multiple liver lacerations, left-sided pulmonary contusion, bilateral rib fractures, and an open-book pelvic fracture.
Upon his arrival, fluid and blood resuscitation was initiated because of profound hypovolemic shock, and R.B. was taken to the operating room for an exploratory laparotomy. He underwent splenectomy, and the liver was packed to control bleeding. A pelvic hematoma associated with the pelvic fracture was noted intraoperatively. Because the bowel wall was edematous as a result of the resuscitation, primary abdominal wall closure was not done in order to prevent abdominal compartment syndrome. The abdomen was closed temporarily with prosthetic material, and R.B. was taken to the angiography suite to further control bleeding. He underwent embolization of the left internal iliac and right intra-hepatic vessels. After the surgery, he was admitted to the intensive care unit.
One day after admission, he began to have signs of ARDS, and use of prone positioning was tried. The prone position was not well tolerated because of hemo-dynamic instability. Within a few days, progressive respiratory failure developed, leading to a second attempt at prone positioning. The combination of total body weight and the extreme size of the abdominal protrusion (Figure 1
) prevented the use of standard methods.
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Case 2
C.R., a 27-year-old man, was a pedestrian struck by a semitrailer truck at a high rate of speed. His injuries included an atlanto-occipital dissociation (dislocation of the first cervical vertebra from the skull), intracranial hemorrhage, grade IV liver laceration, mesenteric hematoma, right-sided perinephric hematoma, multiple left rib fractures, bilateral pulmonary contusions, right acetabular fracture, and an open-book pelvic fracture.
Upon C.R.s arrival in the emergency department, fluid and blood resuscitation was initiated because of hemodynamic instability. He was emergently taken to the operating room for exploratory laparotomy and control of hepatic bleeding. During the surgery, coagulopathy developed, and he was given multiple blood transfusions. C.R. had severe hypoxia, for which he received maximal mechanical ventilator support. Bilateral chest tubes were placed because of hemothoraces and pneumothoraces but did not markedly improve his pulmonary status. A damage-control laparotomy was done. The liver was packed after surgical control of bleeding, and the abdomen was temporarily closed to prevent abdominal compartment syndrome.
C.R. was taken from the operating room directly to the intensive care unit for stabilization, resuscitation, and completion of radiological studies. Postoperative radiography revealed an atlanto-occipital dissociation, and computed tomography of the head indicated an intracranial hemorrhage. Intracranial pressure monitoring was started, and cervical tong traction was established. Measurements of intracranial pressure were within the normal reference range.
Despite maximum ventilation and oxygenation, C.R. remained hypoxic. It was determined that prone positioning might be beneficial. Radiographs were obtained before and after positioning to assess cervical alignment while C.R. was in traction. He was then transferred onto a Stryker frame so that cervical traction could be maintained while he was rotated into the prone position (Figure 3
). His position was changed from prone to supine or from supine to prone every 4 hours; he tolerated this regimen well. Periodically, lateral cervical spine radiographs were obtained to ensure correct cervical alignment.
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| DISCUSSION |
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In both of our patients, marked hypoxia developed that met the criteria for ARDS despite maximal ventilator support by conventional standards. For this reason, prone positioning was deemed necessary despite the lack of supporting data on its use in patients with open abdominal incisions. In both instances, we created new techniques that enabled us to use prone positioning in these patients safely and effectively. In each case, the process was labor intensive and physically challenging for all personnel involved. Ultimately, with the collaboration of nursing staff, physicians, and physical and respiratory therapists, the tasks were successfully accomplished by using rather unconventional methods. Of note, periods in the supine position were necessary to allow nursing care and evaluation as well as medical intervention (ie, central venous access).
| Acknowledgments |
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| References |
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