Learning Objectives

Discuss the approach, diagnostic and treatment of patients with free fluid in the abdomen in small animal practice.

Hemoperitoneum also called hemoabdomen, is defined as free blood or hemorrhagic fluid within the abdominal/peritoneal cavity. The truly incidence of this condition is difficult to estimate because mild cases often go undetected due to the lack of evident clinical signs. Hemoabdomen, however, is a frequent finding in small animal emergency cases, specially related to trauma.

Etiology

Etiologies of hemoperitoneum in dogs can be categorized into traumatic and nontraumatic causes. Blunt or penetrating trauma can cause hemoperitoneum, with vehicle injury recognized as the leading traumatic etiology. From 40 dogs that had vehicle trauma, 38 dogs were found to have hemoabdomen diagnosed by ultrasound and fluid analysis.

Nontraumatic causes of hemoperitoneum include acquired coagulation disorders as in rat poison, other coagulation defects, rupture of ill organs an intra- abdominal neoplasm. A recent study report a moderate incidence of spontaneous hemoperitoneum cases in cats with liver diseases as lipidosis. A retrospective study of dogs with nontraumatic hemoperitoneum identified malignant neoplasia as the cause for hemoperitoneum in 24 of 30 dogs with a definitive diagnosis.

History and Clinical Signs

The physical exam can point toward a possible hemoabdomen when reveal abdominal distension, a fluid wave, a palpable abdominal mass, or abdominal pain is found. A minimum amount of 40 ml/kg of peritoneal fluid is necessary to detect a fluid wave, making abdominal distension an insensitive indicator of early free abdominal fluid accumulation.

During the triage, a detailed evaluation of the perfusion parameters (BP, MM, CRT, FP, HR, Temp) will help to categorize the patient according to level of severity of presenting clinical signs (i.e., catastrophic, severe, or mild). Patients presenting with catastrophic hemorrhage will be in late decompensation and at risk for sudden death. Severe clinical signs suggest acute or large volume bleeding and the need for immediate treatment with fluids and volume support. Any diagnostics should be delayed until the patient is stable.

A classification system was developed to evaluate human patients presenting with hemoabdomen:

 Class I hemorrhage
(loss of 0–15% of blood volume)

 Class II hemorrhage
(loss of 15–30% of blood volume)

 Class III hemorrhage
(loss of 30–40% of blood volume)

 Class IV hemorrhage
(loss of >40% of blood volume)

Although no such classification exists for veterinary patients, similar clinical signs would be expected in dogs and cats with significant hemorrhage. In addition, clinical signs may not correlate exactly with these classifications, as other concurrent conditions may be present, affecting the clinical response to the underlying blood loss. Regardless, clinical signs of shock are usually present in patients presenting with significant blood loss into the peritoneal cavity.

Abdominocentesis is a rapid method for diagnosis and can be performed easily with minimal restrain and at the same time of resuscitation. Alternatively ultrasound guidance can be used to visualize abdominal fluid for sampling. When the hemoabdomen is not evident, a low PCV and TS (or PP) is very suggestive of blood loss; however, the presence of a normal or elevated PCV with concurrent low TS also may be the consequence of acute bleeding with splenic contraction and release of sequestered red blood cells. Getting non-clotting whole blood that from the abdomen is confirmatory of the diagnosis of hemoperitoneum and can be assessed by gross examination of the fluid.

Analgesia/Sedation

Hemoabdomen is painful and often those patients presented after very anxious circumstances: Sedation and analgesia is an important part of the treatment and should be always considered:

 Hydromorphone 0.025–0.2 mg/kg IV, IM or SC

 Fentanyl 0.005–0.04 mg/kg IV, as in CRI 005–0.01 mg/kg/hr

 Buprenorphine 0.01–0.02 mg/kg IM–SQ or through the oral mucosa in cats

 Our clinical experience suggest the usage of maropitant 1 mg/kg SID as part of the analgesia strategy.

 Midazolam or diazepam 0.2–0.5 mg/kg IV; butorphanol 0.1 mg/kg IV, IM or SC

Maintain Oxygen-Carrying Capacity

Supplemental oxygen via flow-by, nasal catheter, hood, or cage with aim of Fi02 of 40%can help to increase the arterial partial pressure of oxygen.

Transfusions should be considered whenever there are signs compatible with severe anemia and hemorrhagic shock (tachycardia, tachypnea, bounding pulses, collapse) and there is a declining trend in PCV and Hgb values after initial fluid resuscitation.

As a general guideline in our Hospital we consider transfusion in patients with hematocrit below 20% the HGB concentration below 8 g/dl, however, in cases with severe and active hemorrhage, transfusions could be necessary before reaching those values.

To pursue auto-transfusion, the intra-abdominal blood should collected aseptically by aspirating into a sterile syringe/needle suction or by suctioning into a sterile container during surgery.

Abdominal counterpressure can be quickly applied in dogs for rapid control of intra-abdominal hemorrhage regardless of etiology. This procedure can provide hemostasis, and may be the only option for hemostasis when owners reject surgical intervention.

Diagnostic Imaging

Imaging studies should be delayed until the patient is stable enough to tolerate positioning, sedation and restrain. Radiographs are not specific for patients with hemoperitoneum and the loss of serosal detail are the most common finding.

Focused abdominal sonography for trauma (FAST) is the current standard in the evaluation for the presence of free abdominal fluid. The FAST protocol consists of examination of four intra-abdominal regions: (1) immediately caudal to the xiphoid process, (2) on the ventral midline over the bladder, (3) over the right flank, over the most gravity dependent area of the left flank.

Computed tomography (CT) is the standard diagnostic and monitoring tool used in the management of hemoperitoneum in humans, but disadvantages of standard CT in veterinary medicine include the need for an anesthetic procedure, limited availability, cost, and the need for specially trained operators.

Treating Hypovolemia

Stabilization of patients experiencing hypovolemic shock has been and continue to be a subject of intense controversy related to the amounts, the rates and the type of fluids. New research data has added new information about delayed complications due to aggressive fluid therapy, but anecdotally, do not provide better alternatives on how to treat these patients.

A clear strategy about volume, fluid type, and rates of administration for patients with significant hemorrhagic shock is not evident so far. As a general rule, bolus infusion of crystalloids at 30 ml/kg, could be used and followed by a close monitoring of the patient response. Subsequent boluses of 30 ml/kg may be administered if necessary. Despite that new information revealed potential complications with the usage of synthetic colloids, in cases were moderate to severe hypotension is present, colloids can be administered along with the crystalloids to support both blood pressure and colloid oncotic pressure.

Patients presenting with large amounts of blood into the abdomen, and symptomatic as hypovolemic shock (tachycardia, tachypnea, weal pulse, poor capillary refill time, pale mucous membranes, impair mentation - ambulation, and severe anemia) should be resuscitated with blood products, as whole blood.

Two new resuscitation strategies have been proposed, but still, no consensus exists for the most effective fluid resuscitation plan to reduce mortality from abdominal hemorrhage.

The usage of hypertonic saline (7% solution) has been advocated through the administration of one or two bolus of 2–4 ml/kg in conjunction with isotonic crystalloid CRI infusions.

Surgical Intervention

In the patient with large-volume and ongoing hemorrhage, the sudden decrease in abdominal pressure through the release of abdominal counterpressure or in making the abdominal incision can result in massive hemorrhage and rapid decompensation to the point of hemodynamic collapse.

References

References are available upon request.