Small Animal Surgical Emergencies. Группа авторов
the patient in hypovolemic shock, with emphasis placed on preparing the patient for correction of the intestinal and vascular anatomic abnormalities as promptly as possible. Fluid resuscitation is vital and should be among the first steps in treating patients; it should not be sacrificed in the pursuit of diagnostics. While septic and toxic shock will not resolve without management of the underlying cause, resuscitative efforts are employed to optimize patient status in preparation for anesthesia and surgery (see Chapter 1). Colloids or hypertonic crystalloids are used as necessary to correct hypotension. Once the patient is as stable as possible and a high index of suspicion for intestinal volvulus has been reached, abdominal exploration should not be delayed. Timeliness in correcting the volvulus is critical in influencing patient outcome [9, 20]. Anesthesia should be planned carefully as patients often remain critical at the time of surgery and may decompensate rapidly secondary to reperfusion injury or uncorrected acid–base abnormalities. Vasopressor therapy may be required to maintain normotension and protect renal function. If the patient is not responding to typical resuscitative efforts, and the index of suspicion for intestinal volvulus is high, rapid diagnostic and therapeutic decision making is critical. Typically, abdominal radiographs lead most efficiently to the diagnosis, however, to prevent further patient decompensation, clinical judgment must be exercised when deciding to take the time to obtain radiographs.
Surgical Treatment
Abdominal exploration allows for definitive diagnosis and assessment of the extent of disease while at the same time providing opportunity for correction. Characteristically, deep purple to black intestine is noted wherever vasculature is compromised. Compromised blood flow through the cranial mesenteric artery and its branches leads to ischemic injury in the distal duodenum, jejunum, ileum, cecum, ascending and proximal descending colon [2]. With complete mesenteric torsion, there will typically be a very ischemic to necrotic appearance to the intestine with twisting at the root of the mesentery (Figure 9.4). A segmental intestinal volvulus may result in a smaller portion of intestine appearing affected (Figure 9.5). The root of the mesentery should be identified and evaluated for orientation of volvulus and anatomic abnormalities (adhesions or malformations) that may have contributed to the pathology. The volvulus may be 180 degrees to greater than 360 degrees and has been reported to occur either clockwise or counterclockwise [9, 18]. A full abdominal exploration is indicated to ensure that gastric volvulus or splenic torsion has not occurred concurrently, and to assess for other pathology that may have contributed to gastrointestinal disease.
Figure 9.4 Postmortem photograph of a dog with complete mesenteric torsion. Twisting is apparent at the level of the mesenteric root.
Source: University of Minnesota Veterinary Diagnostic Laboratory, Minneapolis, MN. Reproduced with permission from University of Minnesota Veterinary Diagnostic Laboratory.
Figure 9.5 Intraoperative photograph of a dog with intestinal volvulus involving a portion of the small intestine. Note the marked difference between the appearance of normal intestine and the affected portion.
Correction of intestinal volvulus may be accomplished by derotation alone or derotation with resection and anastomosis. Resection before derotation may minimize injury secondary to reperfusion and release of free radicals or other harmful factors into general circulation. Resection before derotation is more feasible when a segmental volvulus is encountered, or when a clear delineation of a relatively short portion of compromised bowel is identified. Performance of intestinal resection after derotation may allow for more rapid perfusion to partially compromised tissues that may have a chance of ultimate viability. Gradual derotation of the intestine may reduce the rate of perfusion and lessen the consequences of reperfusion [30]. Even after derotation and several minutes of perfusion, the surgeon may be faced with the decision to perform radical intestinal resection. Bowel that remains black, thin, cool to the touch, or has no return of arterial pulses should be resected. With complete volvulus, the extent of compromised tissue may be so great as to result in short bowel syndrome (if more than 70–85% of the intestines must be resected) [31–33] or may render resection incompatible with normal physiologic function and life. Following correction of volvulus, the abdomen is thoroughly flushed to minimize residual contamination from bacterial translocation or intraoperative contamination.
Postoperative Treatment
Unfortunately, recovery from surgery and the anesthetic episode does not ensure a successful or rapid recovery. There are multiple sequelae to which intestinal volvulus patients may succumb during the immediate postoperative period. Aggressive supportive care and vigilant monitoring are vital, owing to the dynamic and rapid progression of shock. Table 9.1 includes recommendations by the authors for postoperative stabilization in dogs following exploratory surgery for an intestinal volvulus. Fluid loss, shock, and reperfusion injury must be addressed. Isotonic crystalloid therapy (PlasmaLyte and Normosol‐R) provides the mainstay treatment for hypovolemic shock, and is administered to effect for stabilization of hemodynamic parameters. Capillary refill time, heart rate, blood pressure, and lactate concentrations can be used to guide the volume and rate necessary. Intensive monitoring whenever available, including central venous pressures and colloid osmotic pressures, is recommended. For patients struggling to maintain normotension, colloids (hetastarch or plasma) or hypertonic saline can be administered along with adjusted rates of crystalloids, again with a goal‐directed plan dictating volume and rate. Positive inotropes (dopamine or dobutamine) or vasopressors (epinephrine or norepinephrine) may become necessary in patients refractory to fluid resuscitation [34–36]. Because patients are considered to be at risk for, or in, septic shock, antimicrobial therapy with broad‐spectrum bactericidal coverage (enrofloxacin and ampicillin) should be administered [34]. Therapy with free radical scavengers may be warranted. Even though antioxidants are difficult to come by in veterinary medicine, possible benefits may be obtained with lidocaine, however optimal dosages have not been established [37–39]. Some patients may benefit from antiemetic therapy (prokinetics, neurokinin‐1 receptor antagonists and centrally acting antiemetics, such as metoclopramide, dolasetron, and maropitant) and may require therapy for peritonitis (fluid replacement and analgesics) [40–42]. Analgesics are an important component of perioperative care (see Chapter 1). Enteral or parenteral nutrition should be considered.
Table 9.1 Emergency therapies.
| Therapy | Dosage |
|---|---|
| Fluids | |
| Crystalloids (Normosol‐R, Plasma‐Lyte) | Shock dosage: up to 90 mL/kg to effect, maintenance: 40–60 mL/kg/day |
| Hypertonic saline | 4–7 mg/kg to effect |
| Colloids | |
| Hetastarch | Shock dosage: 5–20 mL/kg to effect, maintenance: 10–20 mL/kg/day |
|
Plasma
|