Infections in trauma patients

Sepsis is a leading cause of in-hospital death. The incidence of sepsis due to multidrug resistant organisms (MDROs) is rapidly increasing. MDROs can colonize frail patients such as immunocompromised, older and trauma patients. In particular trauma patients who survive to initial injury can develop hospital-acquired infections. 
Without prompt diagnosis and early treatment these infections can lead to sepsis with very poor prognosis.
The epidemiology of trauma death was described by Trunkey in 1983 as a trimodal distribution. The distribution described was immediate death from injuries at the scene, early death from complication of injuries, and late death from organ failure. These late deaths are due to sepsis. The incidence of sepsis in post-traumatic patients reported in literature is from 2% to 10%.
Why trauma patients are at risk to develop sepsis?
Along with comorbidities, previous infections, age, leakage of skin and intestinal barriers as well as impaired defence mechanisms predispose trauma patients to sepsis. A damage control procedure is often performed in these patients in trauma scene or in emergency department (such as pelvic packing). In these conditions there may be a lack of antiseptic measures and bacteria can easily colonize the patients. Trauma can cause deficits in the immune system by depressing the humoral and cell-mediated systems. After major trauma, the function of lymphocytes is depressed. The neutrophil chemotaxis is decreased and monocyte antigen presenting capacity is impaired. There are also changes in complement components.
In the trauma center patients surviving trauma have to be strictly monitorized to diagnose early infection before developing of sepsis.
As in other fields, early diagnosis and prompt and appropriate treatment of sepsis can save lives reducing trauma mortality.
What are the risk factors for sepsis following trauma?
Older age is an independent risk factor for sepsis following trauma. This may be because elderly trauma patients have decreased cardiopulmonary function, poor nutritional status, and are susceptible to increased bleeding after injuries. These factors may contribute to compromise physiological processes and immunologic function. In addition, elder trauma patients may have more pre-existing diseases than young patients, and the pre-existing diseases are also a risk factor for post-traumatic sepsis.
In some studies, the male gender is predictive for sepsis after trauma. It is attributable to the production of cytokines causing immunosuppression. In female gender estrogens seems to reduce the production of cytokine with a beneficial effect on immune and cardiovascular system.
Injury severity can be related to sepsis risk because a greater lesion can cause major immunologic dysfunction. We can measure injury severity through some scoring systems: anatomical scoring, physiological scoring and combined.
The most used anatomical scoring system is the ISS (Injury severity score) score. The ISS is based on the Abbreviated Injury Scale (AIS) severity values and is calculated as the sum of the squares of the highest AIS values from each of the three most severely impaired body regions. The AIS body regions are:  Head or neck (including cervical spine), Face, Chest (including thoracic spine and diaphragm) Abdomen or pelvic contents (including abdominal organs and lumbar spine), extremities or pelvic girdle (including pelvic skeleton) and external.
The main physiological system is the GCS (Glasgow Coma Scale). The most important combined scoring system is the TRISS that unifies ISS score with RTS (Revised Trauma Score composed by Glasgow coma scale, systolic blood pressure and respiratory rate).
Increasing injury severity measured by the ISS is associated with increased incidence of sepsis (ISS> 15). A low GCS value standing for the physiological impairment caused by trauma is related to sepsis risk.
The severity of anatomical damage is related to sepsis risk; but a great physiological impairment with little anatomical lesions (such as the brain damage in case of diffuse axonal injury) can lead to post-traumatic sepsis too, because of long standing hospitalization and major use of invasive devices. Other risk factors for sepsis in trauma patients are hypotension at the arrival in Emergency department, the need of multiple Blood transfusions, the development of hypothermia, the need of ICU and multiple surgical procedures. In addition, older age and higher ISS increase the likelihood of death in patients with post traumatic sepsis.
What are the most common infections in trauma patients?
Pneumonia is one of the most common hospital-acquired infections in trauma patients.
Injuries to the thorax, head, and abdomen are associated with a significantly increased risk of pneumonia because of changes in respiratory mechanics.
However, the main risk factors for hospital-acquired pneumonias (HAPs) in trauma patients are the use of prolonged mechanical ventilation and positive end-expiratory pressure.
Ventilator-associated pneumonias (VAPs) are defined as hospital-acquired pneumonias occurring more than 48 h after patients have been intubated and received mechanical ventilation. VAPs are independently associated with death in less severely injured trauma patients.
Early pneumonia within the first few days of hospitalization can also result from aspiration at the time of injury.
Empyemas after trauma is a rare infective complication and can develop after hemothorax, penetrating trauma to the chest, perforation of the diaphragm, contiguous infection, and prolonged chest tube placement.
The development of urinary tract infections is mainly related to indwelling urinary catheter use.
These infections are associated with a greater mortality in trauma patients. Escherichia coli is the most frequent species isolated, although it comprises fewer than one-third of isolates. Other Enterobacteriaceae, such as Klebsiella species, Serratia species, Citrobacter species, and Enterobacter species; non-fermenters such as P. aeruginosa; and gram-positive cocci, including coagulase-negative staphylococci and Enterococcus species, are also isolated.
Use of the urinary catheter should always be discontinued as soon as appropriate.
Is also important the correct administration of urinary catheter with asepsis principles and strict hygiene.
Resuscitation by intravenous lines is a critical part of the care of the trauma patient.
Unfortunately, they are a major source of bloodstream infections.
Central line-associated bloodstream infections (CLABSIs) in critically ill trauma patients are potentially fatal infections and are associated with a substantial increase in long hospital stay and total hospital cost.
Strict adherence to sterile technique can reduce CLBSIs and has become a quality improvement measure.
Risk factors for bloodstream infections in trauma patients are length of stay, presence of preexisting infection, percentage change of serum albumin levels, multiple invasive procedures, transfusion of 10 or more units of blood, number of central venous catheters, and presence of a chest tube.
Hollow viscus injuries (HVIs) are related to significant morbidity and mortality. HVIs are due to both penetrating injury and blunt trauma. They are uncommon in patients with blunt trauma. In these patients a timely diagnosis can be often difficult.
Several mechanisms have been described for bowel injuries occurring after blunt abdominal trauma. Crushing of the bowel segment between the seat belt and vertebra or pelvis posteriorly is the most common mechanism. It results in local lacerations of the bowel wall, mural and mesenteric hematomas, transection of the bowel, localized devascularization, and full-thickness contusions. Devitalization of the areas of contusion may subsequently result in late perforation.
An important determinant of morbidity in patients with HVIs seems to be the time to surgery. Only an expeditious evaluation and diagnosis and prompt surgical intervention can improve the prognosis of these patients.
Age, Abdominal Abbreviated Injury Score, the presence of a significant extra-abdominal injury, and a delay of more than 5 h between admission and laparotomy were identified as risk factors for mortality.
Surgical site infections (SSIs) are defined as infections occurring up to 30 days after surgery (or up to 90 days after surgery in patients receiving implants) and affecting either the incision or deep tissue at the operation site. In patients undergoing trauma surgery, the incidence of SSIs is higher.
In multivariate analyses risk factors for SSI are: type of trauma (blunt or penetrating), the presence of shock, the number of affected organs, high ISS scores, wound classification, use of prophylactic antibiotics, multiple transfusions, and several surgical procedures. There is a clear association between contamination of the abdominal cavity (understood as any type of contamination owing to hollow viscus injuries) and SSIs. Numerous patient-related and procedure- related factors influence the risk of SSI in surgical patients, and hence, prevention requires a “bundle” approach, with systematic attention to multiple risk factors, in order to reduce the risk of bacterial contamination and improve the patient’s defenses. Good patient preparation, aseptic practice, attention to surgical technique, and antibiotic prophylaxis are all essential for the prevention of SSIs.