Haemodynamically Unstable

Patients with penetrating trauma who are haemodynamically unstable require immediate operation. 'Haemodynamically unstable' includes non-responders and transient-responders to initial small-volume fluid bolus administration. Patients should be taken immediately to the operating room, without further unnecessary investigations or interventions.

The only decision to be made in these patients is where is the bleeding and this which cavity to expose first. Where there is a stab or gunshot wound obviously involving the abdomen, the decision is simple, and the patient has a laparotomy.

If there is a question about the abdomen being the source of the bleeding, Diagnostic Peritoneal Lavage (DPL) or FAST scan is used to determine the presence of free intra-peritoneal fluid. For the DPL, a positive aspiration of frank blood, or lavage fluid with a high red cell count (>100,000/ml) is required to confirm the presence of major intraperitoneal haemorrhage.

The decision to perform a laparotomy may be complicated if:

• There are multiple stab wounds/gunshot wounds to multiple cavities.
• The wounds are at, or cross, junctional zones (eg. costal margin, groin or buttock wounds).
• There is evidence or the possibility of cardiac tamponade

The diagnosis of massive haemothorax may be made clinically, with a FAST scan, chest tube or Chest X-ray, depending on the degree of shock present and the rapidity with which such tests can be performed. Cardiac tamponade may be diagnosed with FAST or in the operating room with a pericardial window.

It is more important to take the patient to the operating room and commence surgery than to make a definitive diagnosis. If a thoracic injury is suspected during a laparotomy a hemithorax can be explored through the diaphragm or a formal thoracotomy, and a tamponade explored through a pericardial window and sternotomy.

There should be no delay in trying to resuscitate the patient prior to surgery.
 

Haemodynamically Normal

Patients with clinical signs of peritonitis, or with evisceration of bowel should be taken immediately to the operating room.

Currently there are several possible options for the evaluation of penetrating abdominal trauma in the haemodynamically normal trauma patient without signs of peritonitis. Many of these patients will have some superficial tenderness around the wound site, but no signs of peritoneal inflammation.

The goal of any algorithm for penetrating abdominal trauma should be to identify injuries requiring surgical repair, and avoid unnecessary laparotomy with its associated morbidity.

Adjuncts the the initial evaluation of the trauma patient can provide clues to significant intra-peritoneal injury:

• Chest X-ray
  An erect chest radiograph may identify sub-diaphragmatic air. This must be interpreted with some caution in the absence of peritonitis, as air may be entrained into the peritoneal cavity with a stab or gunshot wound. However it certainly signals peritoneal penetration and warrants further investigation.
  
• Nasogastric Tube
  Blood drained from the stomach will identify gastric injury.
  
• Urinary catheter
  Macroscopic haematuria indicates a renal or bladder injury. Microscopic injury suggests but is not pathognomonic of ureteric injury.
  
• Rectal examination
  Rectal blood indicates a rectal or signmoid penetration. Protoscopy & sigmoidoscopy should be performed (see below)

Options for evaluation

Further evaluation requires the use of one or more of the following diagnostic modalities:

• Serial Physical Examination (PE)
• Local Wound Exploration (LWE)
• Diagnostic Peritoneal Lavage (DPL)
• Ultrasound (FAST)
• CT Scan
• Laparoscopy
• Laparotomy

These different methods, each discussed below, are by no means equal. The decision on which method, or combination of methods, to choose will depend primarily on hospital factors such as trauma patient load, access to in-patient beds, availability of in-house surgical teams, access to multislice CT scanners etc. Whichever decision tree is chosen should be accepted at a hospital-wide level. The practice should not change from surgeon to surgeon and day to day. The algorithm should be routinely audited for missed injuries, effectiveness and use of resources.

Serial Physicial Examination

Serial physical examination has the best sensitivity and negative predictive value of all modalities for the evaluation of penetrating abdominal trauma.

The patient is admitted for observation for 24 hours. During this time the patient is has frequent (hourly), regluar checks of their haemodynamic status. The abdomen is examined routinely for signs of developing peritonitis. Ideally the same surgeon should examine the patient each time. If this is not possible, during a handover period both surgeons should examine the patient at the same time so they agree on the current status of the abdomen and whether there has been any progression in symptoms. The timing of examinations varies inthe literature, but should probably start out more frequently and then decrease over time. A suggested sequence of examination might be at 1, 4, 12 and 24 hours after the initial assessment. Some authors recommend examination every four hours.

If the patient develops signs of haemodynamic instability or peritonitis during this period of observation, a laparotomy is performed. If the patient is well the following day they start a normal diet, and are discharged once diet is tolerated and they have completed the observation period.

Patients who do not develop frank peritonitis, but who have persistent local symptoms of pain and tenderness, with perhaps a fever or tachycardia at 24 hours should be evaluated by another modality: CT Scan, laparoscopy or laparotomy.

The disadvantages of serial physicial exam are primarily the requirement to admit all patients with a penetrating injury, and the requirement for frequent haemodynamic and physical examinations. This usually requires the patient to be in a high dependency type setting, and requires a body of in-house surgeons to perform the serial evaluations.

Local Wound Exploration

Local wound exploration (LWE) requires a formal evaluation of a stab wound under local anaesthesia. This procedure is usually performed in the operating room, but is performed in the emergency department by some institutions. The wound is extended under local anaesthesia and the track followed through tissue layers.

Penetration of the anterior fascia is considered a positive LWE, as penetration of the peritoneum is difficult to identify. A positive LWE leads to either laparotomy or another diagnostic test such as DPL or laparoscopy.

When LWE is used alone to determine laparotomy, there will be a high non-therapeutic laparotomy rate. Even if the peritoneam is penetrated were used as a cut-off, many of these patients will have no intra-peritoneal injury, or an injury that does not require surgical intervention - most commonly omental laceration, mesenteric laceration or liver tears that have stopped bleeding.

Diagnostic Peritoneal Lavage

Diagnostic Peritoneal Lavage (DPL) involves passing a small catheter into the peritoneal cavity, usually at the umbilicus or just inferior to this. If blood can be aspirated through this catheter, this is referred to as a positive 'tap' or aspiration (DPA). If no blood can be aspirated a litre of warm crystalloid solution is run into the peritoneal cavity and then allowed to drain out. This lavage fluid is then sent to the laboratory for analysis of red cell count, white cell count and any bowel contents (faecal or food matter).

It is important to realise that the role of DPL in the haemodynamically stable patient is diffierent from that in the unstable patient. In the unstable patient the problem is one of major haemorrhage, and identifying the site of haemorrhage. DPL is used as an alternative to the FAST scan to identify intra-peritoneal haemorrhage (more often in blunt trauma). In the unstable patient one is searching for a lot of blood, so a positive DPL in this setting requires either a positive aspiration (DPA) or a high red-cell count (>100,000/ml).

The situation in penetrating abdominal trauma is very different. A haemodynamically unstable patient with an abdominal stab wound needs no further investigations and will proceed to laparotomy, as discussed above. So the role of DPL in the haemodynmically normal patient with penetrating abdominal injury is to identify hollow viscus injury (stomach, small bowel, colon) or diaphragmatic injury.

If faecal or food matter is seen on microscopy this is diagnostic. However this is rarely the case - and a decision to proceed to laparotomy is usually based on the red cell count. By necessity this must be lower than that looking for gross haemorrhage, so the threshold for the red cell count is set somewhere between 5000/ml and 20,000/ml. The lower the threshold, the more sensitive the test, but the higher the non-therapeutic laparotomy rate. Contamination from the insertion site of the DPL can lead to false positive results. Some units also use a white cell count >500/ml as a positive result - this value is probably too low and 3000/ml isprobably a better threshold for gastrointestinal tract injury.

The primary disadvantages of DPL are that it is invasive, does not evaluate the retroperitoneum, and has a signficiant false positive rate.

FAST

The role of FAST in penetrating trauma has not been fully evaluated. While FAST is sensitive for pericardial fluid, it appears to have a high false negative rate for intra-abdominal injury. This may improve if serial FAST scans are performed. Ultrasound as yet cannot detect the small amounts of fluid which may be associated with a hollow viscus injury.

• A positive FAST indicates peritoneal penetration, but is poor at discriminating for injuries requiring intervention
• A negative FAST does not exclude significant abdominal injury.

It is therefore impossible to recommend FAST as the only investigation for the assessment of penetrating intra-abdominal injury. It MAY have a role in combination with other investigations.

CT Scan

As the technology has improved, CT scanning is finding more and more of a role in the evaluation of penetrating abdominal injury. Most studies recommend a multidectector (multislice) scanner with triple-contrast protocol (intravenous, oral and rectal), although it is not clear how important the GI contrast is for the detection of bowel injury. Of all the diagnostic modalities listed, CT gives the best assessment of retroperitoneal structures.

The CT features of penetrating bowel injury are:

• Signs of peritoneal violation
  • Free intra-peritoneal air
  • Free intra-peritoneal fluid
  • Wound track extending through peritoneum
     
• Signs of bowel injury
  • Wound track extending to bowel wall
  • Bowel wall defect
  • Bowel wall thickening
  • Intra-luminal contrast leak
  • (not free intra-peritoneal air - may have been entrained through peritoneal wall)
     
• Other signs of intra-peritoneal injury
  • Intravenous contrast extravasation
  • Diaphragmatic tear (especially on re-formats)

The use of CT for penetrating intra-abdominal injury remains in its infancy, and not all CT scanners have the resolution or software capabilities necessary to achieve the sensitivity and specificity rates quoted in the literature. Interpretation of the scans is also difficult and requires multiple passes on different 'window' settings by a trained and experienced trauma radiologist.

Laparoscopy

Laparoscopy is also a technology somewhat in its infancy, and remains very user dependent. A full trauma laparoscopy for the evaluation of penetrating injury requires general anaesthesia and complete examination of intra-peritoneal contents, including visualisation of the whole small bowel and intra-peritoneal colon. In most studies laparoscopy has a significant false negative, primarily from missed bowel injuries. Laparoscopy is also limited in the evaluation of retroperitoneal injury.

Laparoscopy is the diagnostic method of choice for the diagnosis of suspected diaphragmatic injury. Many diaphragmatic lacerations can alse be repaired via the laparoscope.

Laparoscopy may also have a role in patients who have localised tenderness or develop a white cell count or fever without generalised peritonitis after a period of clinical observation. Laparoscopy may be useful to confirm that a wound is tangential and does not enter the peritoneal cavity - although many of the methods above have advantages over laparoscopy for this indication.

Laparotomy

Exploratory laparotomy for all penetrating abdominal wounds still has a role in resource-limited environments, or occasionally in cases of multi-cavitary injuries. For most situations however the non-therapeutic laparotomy rate will be unacceptable high. With the incidence of complications with a negative laparotomy at of 12%-41%, with hospital stays of 4-8 days, , it is difficult to support such a strategy where adjunctive methods such as CT or DPL are available and serial physicial examination has such a low missed injury rate.

Recommended approaches

Which diagnostic tree a hospital chooses for the evaluation of penetrating injury will be dependent on numerous factors, including trauma patient load, surgical team availability and coverage, the availability of multidetector CT scanners and trauma radiologists, and access to the operating room and critical care beds.

Many different systems are used around the world. The following recommendations are in order of preference and are by no means the only possibilities. Each choice is associated with the caveats listed above.

1. Serial physical examination
    
2. Multidetector CT
    
3. Local Wound Exploration AND either:
   
    
   • Diagnostic Peritoneal Lavage OR
   • Laparoscopy