Diaphragmatic Hernias

Question 1

Describe the anatomy of the diaphragm

Answer 1

The diaphragm works as ventilation and assist in the movement of lymphatic vessels. The caval foramen houses the caudal vena cava. The esophageal hiatus houses the the esophagus and vagus nerve trunks. The aortic hiatus houses the aorta, thoracic duct and right azygous vein.

Question 2

What is the most common cause of diaphragmatic hernia?

Answer 2

Vehicular trauma

Question 3

Diaphragmatic hernia pathophysiology

Answer 3

Indirect pressure -> increase intraabdominal pressure

• Lost of diaphragmatic function
• pneumo-, hemo-, thorax; pleural effusion
• herniated viscera
• pulmonary or caval compression
• chest wall contusion
• flail chest: fix of ribs so that area is now mobile and moves independently

Question 4

Describe the types of tears within the diaphragm, where are they most common?

Answer 4

Radial: along fiber orientation
Circumferential: at rib attachments
Or combined

Its rare to see a tears within the central tendon, its usually the peripheral muscles

Question 5

What are clinical signs of diaphragmatic hernias?

Answer 5

Dyspnea, hypovolemic shock in acute trauma, GI signs, Lethargy, restlessness, trouble lying down or no clinical signs

Question 6

To dx diaphragmatic hernias you can take __ rads and __ of cases will have loss of the normal diaphragmatic outline. There may also be abdominal viscera in the thorax, obscured or displaced cardiac shadow.

Answer 6

To dx diaphragmatic hernias you can take lateral rads and 66-97% of cases will have loss of the normal diaphragmatic outline. There may also be abdominal viscera in the thorax, obscured or displaced cardiac shadow.

Question 7

Radiographs of a diaphragmatic hernia

Answer 7

Loss of normal diaphragmatic outline in 60-80
5, obscured displaced cardiac silhouette and cranial pylorus/duodenum

Question 8

Ultrasound for diaphragmatic hernias is __ accurate and helpful with __ effusion

Answer 8

Ultrasound for diaphragmatic hernias is 93% accurate and helpful with pleural effusion

Question 9

In what scenarios should you wait for surgery in diaphragmatic hernia cases?

Answer 9

When they are not stable for anesthesia OR when they have pulmonary contusions because they won’t respond to oxygen if they have then. In these cases you can wait 3-5 days for them to improve and it does not increase morbidity rate

Question 10

Reasons to not wait for surgery of diaphragmatic hernias

Answer 10

Persistent deterioration, gastric herniating with tympani, persistent abdominal pain (intestinal strangulation)

Question 11

Anesthesia interventions for diaphragmatic hernia sx

Answer 11

Tilt the table so that the head and thorax are elevated, preoxygenate. Rapidly induce/intubate and keep sternal. Keep positive pressure ventilation while avoiding high inspiratory pressure (>20), IV fluids and ECG monitoring

Question 12

Surgery for diaphragmatic hernia

Answer 12

1. Ventral midline celiotomy
2. Abdominal explore
3. Evaluate viable organs
4. Debride defect edges (if covered in fibrin)
5. Place thoracostomy tube
6. Lavage after you’ve replaced the organs and started the closure
7. Absorbable monofilament suture in simple continuous or tension relieving patterns

Question 13

The thoracostomy tube goes through the __and out __

Answer 13

The thoracostomy tube goes through the diaphragm and out laterally

Question 14

Considerations for chronic hernias

Answer 14

1. Mature adhesions and/or fibrosis
2. Reperfusion injury
3. Re-expansion injury
4. Re expansion pulmonary edema
5. Loss of domain
6. Primary apposition not always possible

Question 15

Adhesions and/or fibrosis for diaphragmatic hernias

Answer 15

• between herniate organs and thoracic wall and/or lung
• adhesions < 7-14 days old should not pose dissection challenges
• possible complications of chronic adhesions are hemorrhage and pulmonary air leak
• potential organ removal

Question 16

Reperfusion injury of diaphragmatic hernia

Answer 16

Vascular obstruction -> anaerobic metabolism

Acute relief of obstruction
1. Free radical oxygen species
2. Inflammatory cytokines
3. SIRS

Treatment goals is removal without obstruction relief

Question 17

Reexpansion pulmonary edema is an issue in __ with chronically __ lungs where acute re expansion results in reperfusion injury and pulmonary edema.

Answer 17

Reexpansion pulmonary edema is an issue in cats with chronically atelectatic lungs where acute re expansion results in reperfusion injury and pulmonary edema.

Question 18

How to prevent re expansion pulmonary edema

Answer 18

-Keep airway pressure <20 cm H20
- do not force them to re inflate or completely re establish pressure
- reduce pneumo thorax slowly over 8-10 hours

Question 19

Loss of domain of diaphragmatic hernias

Answer 19

• chronic absence of viscera from abdomen
• closure risks excessive intra abdominal pressure
• crowding -> vascular compromise of viscera

Surgical options are organ removal, diaphragmatic advancement or abdominal wall reconstruction

Question 20

Alternative methods of closure for diaphragmatic hernias

Answer 20

1. Muscle flaps (TA or RA)
2. Auto genius grafts (omentum or fascia)
3. Exogenous grafts (SIS, silicone or mesh)

Question 21

Prognosis of diaphragmatic hernias

Answer 21

15% mortality pre surgery and perioperative mortality rate 10-30%, but excellent prognosis if they survive the perioperative period

Stabilize and get them through surgery = a good chance!