Position the patient in dorsal recumbency, and anesthetize the patient with general anesthesia. Because of potential respiratory instability, make the transition from induction to intubation quickly and smoothly to minimize hypoxemia and hypoventilation. Use adequate anesthetic premedication and preoxygenation to minimize stress and maximize oxygenation before induction. Vasopressors (eg, dobutamine, norepinephrine) may be required to maintain blood pressure because of decreased intrathoracic venous return from intrathoracic abdominal organs.
Author Insight
Intermittent positive pressure ventilation is recommended because of the reduced pleural space and loss of negative pressure; however, to minimize barotrauma and the risk for re-expansion pulmonary edema, do not exceed a pressure of 15 to 20 cm H2O.8
STEP 2
Administer perioperative antibiotics (eg, cefazolin [22 mg/kg IV]) 30 minutes before making the incision and every 90 minutes thereafter until skin closure. In cases of chronic diaphragmatic hernia, the degree of adhesion formation will be unknown before surgery; therefore, clip, aseptically prepare, and drape the patient from pubis to manubrium for an exploratory laparotomy and median sternotomy in case increased exposure into the thoracic cavity is required.
Author Insight
Ensure an appropriately wide clip of fur is obtained. Drape the prepared area in anticipation of a thoracostomy, transabdominal, or transthoracic tube.
STEP 3
Perform a ventral midline laparotomy from the xiphoid process to the caudal aspect of the abdomen. Remove the falciform ligament to improve exposure of the cranial abdomen, then apply a Balfour retractor. Note the hernia size, location, organ involvement, and type (eg, radial and circumferential). Gently retract the abdominal organs to allow for repositioning into the abdominal cavity, if possible. Use caution, as the abdominal organs may have adhesions in the thoracic cavity.
Author Insight
Diaphragmatic hernia incarceration may occur if contraction of the hernia occurs over time and makes reduction of abdominal contents challenging. The hernia may need to be enlarged with scissors to allow safe retrieval of abdominal organs.
STEP 4
Adhesions may be present in the thoracic cavity in chronic diaphragmatic hernia patients. Break down adhesions using a combination of sharp–blunt dissection, electrocautery, and/or a vessel-sealing device. In a retrospective study, 14 of 50 chronic diaphragmatic hernia patients required resection of portions of the lung, liver, or intestine.4 Therefore, be prepared to perform lung or liver lobectomies (in addition to intestinal resection and anastomosis) due to adhesions.
If adhesion dissection cannot be performed through the diaphragmatic rent, or if increased exposure is required to perform organ resection, a median sternotomy may be needed. Transect the sternebrae longitudinally on the midline from the xiphoid to the second or third sternebra (depending on how much exposure is required) using a bone saw, osteotome and mallet, or, in young animals, heavy scissors.
Author Insight
If lung adhesions are present, performing a partial or complete lung lobectomy is recommended because of the reported complication of persistent pneumothorax from suspected incidental lung laceration during adhesion dissection.4 The authors prefer using a thoracoabdominal stapler for partial or complete lung lobectomy.
STEP 5
Repair the hernia using either long-acting absorbable (eg, polydioxanone) or nonabsorbable (eg, polypropylene) sutures. In chronic cases, use a scalpel blade to freshen the edges of the hernia to promote healing. For diaphragmatic tears that extend toward the cranial vena cava, begin herniorrhaphy dorsally and commence ventrally toward the laparotomy incision. Use a simple continuous or Ford interlocking pattern. In cases of diaphragmatic tears arising from the costal arch of the diaphragm, circumcostal sutures may be necessary to reattach the diaphragm to the body wall.
STEP 6
After completing the herniorrhaphy and returning abdominal contents to the abdomen, ensure viability of contents via complete abdominal exploration. Lavage the abdomen with warm, physiologic saline. Close the linea alba, subcutaneous tissues, and skin.
In some chronic diaphragmatic hernia cases, closure of the linea alba can be difficult because of the chronically decreased abdominal size. If a median sternotomy was made, close it with either orthopedic wire or heavy suture, depending on patient size.
Author Insights
If the abdominal contents are difficult to maintain within the abdomen because of loss of abdominal domain associated with chronic diaphragmatic hernia, organ resection may be required. Perform splenectomy followed by intestinal resection and anastomosis. Organ resection can reduce intra-abdominal pressure and wound tension to limit the risk for vascular compression and ischemia, which can cause abdominal compartment syndrome.9
There are several strategies for re-establishing negative pressure in the thoracic cavity. The authors prefer the use of thoracic drainage catheters because of their size and ease of placement. Drainage catheters should be placed before herniorrhaphy where visualization of the thoracic cavity can be achieved to allow for safe insertion.
STEP 7
Following hernia repair, perform aspiration to re-establish negative pressure of the thoracic cavity.