Читать книгу Complications in Equine Surgery - Группа авторов - Страница 105

Definition

Postoperative hemorrhage can occur immediately after surgery or can be delayed by several days after surgery. Hemorrhage is most commonly from the surgical site, but can occur in distant areas if a coagulopathy has developed.

Risk factors

Same as for intraoperative hemorrhage (see above)

Pathogenesis

The pathogenesis of postoperative hemorrhage is the same as for intraoperative hemorrhage. Inadequate hemostasis may not be recognized at the time of surgery, possibly due to lower blood pressure under anesthesia, positioning (e.g. lower pressure in the distal limb of a horse in dorsal recumbency), or a temporary clot that becomes dislodged after surgery.

Prevention

Same as for intraoperative hemorrhage (see above)

Diagnosis and monitoring

Acute blood loss of 30% of blood volume will result in cardiovascular shock due to hypovolemia and reduced oxygen delivery to the tissues. Signs of shock include tachycardia, tachypnea, prolonged capillary refill time, cool extremities, depressed or anxious mentation, and hypotension. In horses, splenic contraction will increase the PCV, so the decrease in PCV will typically lag behind the decrease in total solids (TS).

Postoperative hemorrhage may be apparent if there is blood leaking from the surgical drain, incision, or nasal passage. Tachycardia, tachypnea, and pale mucous membranes may signal ongoing blood loss, and serial PCV/TS can help to determine the severity of blood loss. TS should decrease within minutes to hours of blood loss, but PCV may remain normal even during terminal blood loss, due to the effects of splenic contraction [24]. Internal bleeding into the abdomen or thorax may not be apparent until the horse begins to show signs of shock or discomfort. In a recent retrospective study of postoperative abdominal hemorrhage, clinical signs included tachycardia, decreasing PCV/TP, abdominal discomfort, and incisional drainage. The hemoabdomen was confirmed by ultrasound or abdominocentesis [42]. Swirling, echogenic fluid is characteristic of hemoabdomen, and abdominocentesis will confirm the diagnosis (Figure 7.3). Blood loss into the intestinal lumen can be more difficult to detect until it is passed in the feces. Intraluminal blood loss should be suspected in horses that have had an enterotomy or large colon resection, and that have an acute, severe decrease in PCV along with tachycardia and melena within 72 hours of surgery [43].

Treatment

See “Fluid therapy and blood transfusion” and “Adjunctive systemic treatment” sections above.

Reoperation

Reoperation is often the last resort for postoperative hemorrhage, but should be considered early if there is unexpected postoperative hemorrhage and if there is a chance that a ligature may have slipped. A return to surgery may be needed if the patient is deteriorating despite medical therapy, although these patients are likely to be unstable under anesthesia [44]. If bleeding was detected at surgery but was inaccessible, or if the source of bleeding is unlikely to be accessible through the same surgical approach, an alternate approach is indicated. For example, a hemoabdomen post‐castration may be best treated through a standing laparoscopic approach [38].

Figure 7.3 Transabdominal ultrasound image showing cellular echogenic free fluid consistent with hemoabdomen.

Source: Courtesy of Teresa Burns.

In a case series at a level 1 human trauma center, reoperation for bleeding in trauma patients was prompted by direct signs, such as external bleeding or bleeding from drains, in 74% of patients. Indirect signs that led to reoperation included hemodynamic instability, decrease in hematocrit, and abdominal distention [44].

Expected outcome

Mortality in horses with hemorrhage after emergency celiotomy was reported to be 35%. Causes of death were hemorrhagic shock, septic peritonitis, and adhesions [42]. In a report of post‐castration complications, less than 2% of horses undergoing routine castration suffered from significant hemorrhage. In all horses, bleeding occurred within 4 hours of surgery, and all were treated by packing with sterile laparotomy sponges which were removed at 24–48 hours. One horse received aminocaproic acid [45].