Blunt Trauma

Before the advent of computed tomography (CT) and US, DPL was the sole diagnostic option to supplement physical examination for predicting the need for operative intervention (Table 43-1). It was integral to both reduction of unnecessary laparotomies and discovery of unsuspected and life-threatening intraabdominal hemorrhage in patients with significant closed-head injury.^6,7

This procedure may be undertaken by the emergency physician, but its use is not mandated and often relegated to the trauma service or consulting surgeon. In a number of respected centers in the United States, DPL continues to be a focal diagnostic instrument.2,8 It serves two primary functions.⁹ First, it can be used to rapidly determine or exclude the presence of IPH (Table 43-2). Thus, a patient with a critical closed-head injury, an unstable motor vehicle crash victim with multiple potential sources of blood loss, or a patient with pelvic fractures and retroperitoneal hemorrhage can be appropriately routed to lifesaving laparotomy.^10,11 Furthermore, given its exquisite sensitivity, a negative peritoneal aspiration allows the clinician to proceed to alternative management steps and the patient to forego unnecessary laparotomy. Second, DPL has been used in less exigent circumstances as a means of predicting solid or hollow visceral injury requiring laparotomy.^12,13 However, in this venue its sensitivity to the presence of hemorrhage may prompt unnecessary laparotomy in patients with self-limited lacerations of the liver, spleen,^14–17 or mesentery.¹⁷ CT specifically evaluates all intraperitoneal structures, as well as the retroperitoneum, a region inaccessible to DPL. Because the resolution and the speed with which it can be undertaken have vastly improved, CT has become an invaluable adjunct in the management of blunt trauma and has largely replaced DPL in stable patients. It is most useful in identifying injury to solid organs with accompanying IPH and greatly assists nonoperative management of these injuries. The ability of CT to discern hollow viscus and pancreatic pathology has continued to improve as the modality has evolved.¹¹ With regard to hollow viscus injury, it is when serial clinical evaluations cannot be performed that gut perforation leads to preventable mortality. This is especially true in patients with severe closed-head injury or high spinal cord injury, in whom physical assessment of the abdomen is quite compromised. It is for these express scenarios that some authorities recommend the performance of DPL. The clinician’s concern for hollow viscus injury should be heightened if US or CT demonstrates minimal amounts of free intraperitoneal fluid without evidence of solid organ damage.¹⁸

Two paradigms have brought US to the forefront. First, this modality has been adopted as the primary triage instrument, in lieu of DPL, for the detection of IPH on the basis of identifying which pouches and gutters are filled with fluid.19–21 Clinical success in this role has been mixed, with reported sensitivity for IPH of 65% to 95%.^22–28 In addition, to be useful in this role, a competent technician and interpreter and the appropriate equipment must be present in real time. It has been demonstrated that emergency clinicians and surgeons can be trained in this technique to a level of competence sufficient for this need.²⁹ In centers that rely on US, DPL should serve as a reliable study when US equipment is unavailable, performance of US is technically difficult, or the results of US are indeterminate, especially when the patient demonstrates hemodynamic compromise.

DPL is a readily available procedure that can be conducted rapidly in the safe confines of the ED. The ability to undertake CT in particular or, to a lesser extent, US in a similar manner requires careful consideration of the clinical circumstances, location of equipment, and capabilities of the personnel available (Fig. 43-1 and Table 43-3).^2,11

Penetrating Trauma

The advent of DPL was seminal in the promotion of selective management for penetrating abdominal injury. Here its role is more dominant than for blunt trauma because of the far greater likelihood of occult injury to hollow viscera and the diaphragm after a penetrating mechanism.30,31

Instruments and missiles may penetrate the abdominal cavity via the anterior abdominal wall, flank, back, or low chest region.³² The intraperitoneal space is vulnerable if penetration occurs as high as the fourth intercostal space anteriorly and the sixth or seventh space laterally and posteriorly because the diaphragm may rise to these levels in the expiratory phase of respiration.³³ Coincident thoracic penetration occurs in up to 46% of patients with abdominal injuries.^34–36 The likelihood of retroperitoneal injury increases when the entry site is over the flank or back, but the prospect of intraperitoneal pathology remains considerable, with cited incidences of up to 43% for the flank and 14% for the back (Table 43-4).^37–39

Placement of the Catheter

There are two basic methods for DPL: open and closed. The two open techniques are semi-open and fully open, and both typically require an assistant. DPL is clearly within the diagnostic armamentarium of the emergency clinician and surgeon. Either may undertake it in keeping with clinical policies established at the particular trauma center.

Site

The optimum location for DPL is at the infraumbilical ring at the inferior border of the umbilicus (Table 43-6). Here, between the rectus abdominis muscles there is adherence of the peritoneum and relative lack of vascularity and preperitoneal fat.⁶¹ Closed DPL should always be conducted here. In the event of second- or third-trimester pregnancy, a suprauterine approach is used. If midline scarring is present, a fully open technique at the lateral border of the rectus abdominis in the left lower quadrant may be necessary. The left side is preferred to avoid later confusion about whether an appendectomy has been performed. It is interesting to note that Moore and associates found no increase in complications or misclassified lavage when the closed technique was used in a small series of patients with previous abdominal surgery.⁷⁴ In the presence of a pelvic fracture, use a fully open supraumbilical approach. This greatly decreases the likelihood of passing the catheter through a retroperitoneal hematoma that has dissected from the fracture anteriorly and across the abdominal wall.⁷⁵ In patients with penetrating trauma, do not perform DPL through the stab or missile entry site. This approach can contaminate the intraperitoneal cavity, potentially exacerbate the abdominal wall bleeding, and lead to a false-positive result.

Aspiration and Lavage

Once the catheter has been placed successfully into the peritoneal cavity, attach the right-angle adapter, extension tubing, and a non–Luer-Lok syringe and attempt aspiration (see Fig. 43-4, step 8). If 10 mm of blood is aspirated, the test is positive and the procedure is terminated. With penetrating trauma, acquisition of lesser amounts may be meaningful because of the tendency for the diaphragm and bowel to hemorrhage minimally when injured. However, no rules have been established in this regard.

If little to no blood is aspirated, lavage the peritoneal cavity with either normal saline or lactated Ringer’s solution (see Fig. 43-4, step 9). Apply a blood pressure cuff or blood infusion pump around the plastic intravenous (IV) bag to speed the influx (i.e., decrease lavage time) if necessary. Large-bore infusion tubing (e.g., urologic irrigation tubing sets, such as the Abbott No. 6543 cystoscopy/irrigation set) also shortens fluid influx time. Infuse 1 L of fluid in adults or 15 mL/kg in children. When possible, roll or shift the patient from side to side after the infusion to increase mixing. Place the IV bag or bottle on the floor (or below abdominal level), and allow the fluid to return by gravity.

If the fluid does not return, there may be several reasons. Some IV tubing contains a one-way valve. If tubing with a valve was used in error, replace it with valveless tubing and reattach it to the IV bag. Another reason for poor return is inadequate suction. To correct this problem, insert a needle into the second opening at the bottom of the IV bag or into the head of the IV bottle for aspiration of 10 mL of air. Alternatively, the catheter may be adherent to the peritoneum. If so, try to relieve some of the pressure in the IV bottle by gently wiggling and twisting the catheter or applying abdominal pressure to aid in the return of flow.

Return of 700 mL or more in an adult is generally accepted as adequate for interpretation of the findings. However, as little as 10% to 20% of the infusate may give a representative sample for both gross and microscopic determination. Send 10 mL of fluid from the return to the laboratory for cell count analysis, and send another 10 mL for enzyme analysis (see the section “Interpretation” later in this chapter). Some operators prefer to leave the catheter in place until the returned fluid is analyzed so that lavage may be repeated if the initial results are borderline or an occult bowel perforation is suspected.

Local and Systemic

Local wound complications, including infection, hematoma, and dehiscence, occurred in only 0.3% of patients in two large series.42,76 Dehiscence with evisceration is an even rarer condition.⁷⁷ Systemic infection has been described rarely (Table 43-7).

Intraperitoneal

Iatrogenic intraperitoneal injury can be inflicted by the trocar, wire, and rarely, the catheter. Virtually any structure in the peritoneal cavity can be breached, including the small and large bowel, the bladder, and major vessels. Typically, if the needle is the culprit and even if the trocar is responsible, injury to these structures is minimal and self-limited, and observation of the patient is sufficient.

Technical Failure

Inability to recover peritoneal aspirate or lavage fluid can result in a false-negative interpretation. This can occur in several circumstances. It follows unwitting placement of the catheter into the preperitoneal space, which is less likely to occur with either open technique. Compartmentalization of fluid by adhesions or obstructing omentum can impede the egress of fluid. When a fully open supraumbilical or suprauterine technique is used, the catheter may be too short to access the depths of the intraperitoneal cavity. Finally, the large diaphragmatic tears typical of blunt pathophysiology allow flow of lavage fluid from the intraperitoneal to the thoracic cavity. Saunders and coworkers compared percutaneous DPL and the open technique in a prospective, randomized trial.⁷⁸ Fluid obtained by the two techniques had similar test performance for intraabdominal pathology. The open technique took, on average, more than 4 minutes longer, but the percutaneous approach had an 11.2% technical failure rate (versus 3.8% with the open approach).

False-positive findings can occur in two ways. First, iatrogenic misadventure may be responsible. Second, in penetrating trauma, particularly stab wounds, bleeding from the abdominal wall injury site into the peritoneal cavity can lead to positive findings when no injury to intraperitoneal structures has occurred.⁴⁴

Gross Blood

Recovery of 10 mL or more of blood via aspiration is considered a positive finding. Aspirates with lesser volume are generally discarded and are not factored into analysis of the lavage fluid. Grossly bloody aspirates are typically indicative of solid visceral or vascular injury, with a positive predictive value of greater than 90%.79,80 Aspiration of blood is responsible for approximately 80% of true-positive DPL findings with blunt trauma and for 50% with stab wounds.⁴³

A positive aspiration in a blunt trauma patient who is hemodynamically stable or has been resuscitated to apparent stability need not mandate urgent surgery. Unnecessary laparotomy will occur if there has been minimal and self-limited damage to the liver, spleen, bowel serosa, or mesentery.⁸¹ In this situation, CT and clinical indicators should be used in concert with the findings on DPL.

RBC Count

The recommended red blood cell (RBC) threshold varies according to the mechanism and, in the case of stab wounds, the external site of injury (Table 43-8). The optimum criterion will deliver excellent sensitivity, a high positive predictive value, and a minimal incidence of unnecessary laparotomy. Negative laparotomy incurs a prolongation of hospitalization and increases the cost of care, in addition to creating the potential for procedural complications.^82,83 RBC counts greater than 10⁵/mm³ (10⁵/µL) are generally considered positive with a blunt mechanism or after stab wounds in the anterior part of the abdomen, flank, or back. Counts of 20,000 to 100,000/mm³ should be considered indeterminate.^43,45,84,85 For stab wounds in the low chest region, where the diaphragm is at increased risk for injury, the RBC criterion should be lowered to 5000/mm³ to maximize sensitivity for isolated injury to this structure.^36,43,86,87 With gunshot wounds involving the abdomen or low chest region, the same RBC criterion of 5000/mm³ is applied. This is intended to increase the sensitivity of the test because intraperitoneal entry by a missile carries a 90% or greater likelihood of intraperitoneal injury.^36,60,88 An uncomplicated DPL should not result in more than several hundred to several thousand RBCs in the peritoneal lavage fluid.