7. Digestive System

Question 1

What are the 5 anatomical regions of the stomach?

Answer 1

1. Cardia - entrance of the intra-abdominal oesophagus into the stomach; contains primarily mucous cells to provide lubrication for ingesta

2/3. Fundus and body - left and dorsal region of the cardia; food fills the fundus and then body; fundus and body contain primarily chief cells for the production of pepsinogen and parietal cells that produce hydrochloric acid (HCl); body has the greatest dilation capacity.

4. Antrum - distal portion of the stomach, directed cranially; serves in in mechanical digestion containing many mucous cells as well as gastrin-secreting cells (g-cells) which stimulate HCl secretion from the parietal cells.
5. Pylorus - anatomical sphincter between the stomach and duodenum; controls gastric outflow and prevents duodenal reflux.

Question 2

What are the 4 layers of the stomach?

Answer 2

Deep to superficial

1. Mucosa - surface epithelium, rugae; glanular lamina propria and lamina muscularis mucosa
2. Submucosa - elastic layer of connective tissue; CRITICAL HOLDING LAYER
3. Muscularis - outer longitudinal and inner circular smooth muscle fibres thicker in the region of the pylorus
4. Serosa - smooth membrane with a thin layer of epithelial cells which offer minimal holding power for sutures

Question 3

What is the main blood supply to the stomach?

Answer 3

Coeliac artery, which branches into the hepatic, left gastric and splenic arteries

Right gastric artery branches off the hepatic artery and anastomoses with the left gastric artery to supply the lesser curvature of the stomach

Hepatic artery then continues as the gastroduodenal artery and gives rise to the right gastroepiploic artery

Left gastroepiploic artery arises from the splenic artery and arborizes with the right gastroepiploic arter to supply the great curvature of the stomach

Venous drainage is via the gastrosplenic vein on the left and gastroduodenal vein on the right, which then empty into the portal vein

Question 4

What is the nervous innervation to the stomach?

Answer 4

Parasympathetic fibres from the vagus nerves

Sympathetic fibres from the coeliac plexus

Question 5

What is the lymphatic drainage to the stomach?

Answer 5

Gastric and splenic lymph notes to the hepatic lymph nodes

Question 6

Describe healing of the stomach?

Answer 6

Rapid healing - rich blood supply and paucity (littleness) of intraluminal bacteria.

3-4 days postoperative:
- inflammation predominates, infiltration of neutrophils and macrophages to clean up cellular debris
- fibrin seal along serosa typically prevents leakage but surgical sutures are responsive for maintaining wound approximation
- migration of mucosal epithelium across wound bed

5-12 days postoperative:
- rapid acceleration of wound strength
- collagen-rich submucosa main source of fibroblasts for proliferative phase

Weeks following day 12 postoperative:
- maturation of gastrotomy scare

Long term complications uncommon

Question 7

Describe food withholding in patients prior to surgery

Answer 7

Traditionally 8-12 hours recommended

However, withholding food does not reliably empty the stomach, lowers the pH and actually increases the risk of oesophagitis and postoperative stricture from gastro-oesophageal reflux

Small amounts of food at least 3 hours before the procedure have been shown to reduce gastric acidity and even the incidence of reflux

Question 8

What electrolyte abnormalities may result from pyloric FBs?

Answer 8

Loss of potassium, sodium, hydrogen and chloride ions

Results in a hypokalaemic, hypochloraemic metabilic alkalosis

Monitor electrolyte values carefully in the perioperative and immediately postoperative period

Question 9

What key considerations of gastric surgery should be considered?

Answer 9

Exteriorisation
- cannot usually be exteriorised from the abdomen

Contamination risk
- risks of ingesta spilling into abdomen

Visualisation
- requires adequate length abdominal incision extending from the xiphoid process of the sternum to a point caudal to the umbilicus
- may require a parapreputial skin incision in the male dog
- consider falciform ligament excision, especially in overweight and deep-chested dogs
- consider Balfour retractors or large Gelpi retractors in small dogs or cats as a substitute

Stay sutures
- can elevate proportion of the stomach before gastrotomy is made
- can also use Babcock forceps for this purpose

Barriers
- moist laparotomy swabs/sponges
- reduce gastric serosal abrasion if moist

Abdominal lavage
- 0.9% saline or hartmann’s
- 37-39 degrees celcius (warm)
- minimum 1 litre large dog, 500 ml cat
- ensure to suction remnant prior to closure

PPE
- consider clean and dirty surgical kit/gloves
- seperate kits for gastric vs abdominal closure

Perioperative antibiotics
- not required unless break in asepsis/ingesta spillage into abdomen
- relatively low population of bacteria within the stomach normally

Question 10

What are the phases of healing in the stomach, with days?

Answer 10

Lag/reparative phase - day 1-3

Proliferative phase - day 3-14 = wound strength 80% normal

Maturation phase day 14 onwards = reaches 90% normal bursting strength

Question 11

What are the benefits of the submucosa as the primary closure layer?

Answer 11

Greatest vascularity

Greatest collagen content

Greatest tensile strength

Question 12

How should the stomach be closed?

Answer 12

2 layers - including submucosa in at least 1 of the layers

layer 1 - mucosa/submucosa = Cushing or Connell continuous inverting pattern; suture material may enter the lumen of the stomach; can use simple continuous approximating if Cushing or Lembert used for second layer

layer 2 - Cushing or Lembert pattern, can also use simple continuous approximating pattern

Question 13

What type of needle is best for closure of the stomach?

Answer 13

Taper needle or taper point needle.

Cutting needles may lacerate the muscularis or submucosa during passage through those tissues

Question 14

What clinical syndromes may be observed following antrectomy procedures?

Answer 14

Chronic vomiting

Alkaline reflux gastritis

Marginal (anastomotic) ulcer - more common in Billroth 2 procedures

Gastric dumping syndrome

Afferent loop syndrome - Billroth 2 procedure

Question 15

What is a Billroth 1 procedure?

Answer 15

Used when resection of the antrum and/or body of the stomach.

Used to correct luminal disparity, with partial closure of the larger lumen.

Question 16

What is a Billroth 2 procedure?

Answer 16

Gastrojejunostomy following partial gastrectomy (including pylorectomy).

Joins the jejunum to the stomach.

Question 17

Describe a Billroth 1 vs 2 procedure

Answer 17

Question 18

Describe the difference between an axial/sliding hiatal hernia and a paraoesophageal/rolling hiatal hernia.

Answer 18

Question 19

How are hiatal hernias diagnosed?

Answer 19

Survey/contrast radiography
- gastric silhouette cranial to diaphragm
- dilated caudal mediastinal oesophagus (oesophagitis)

Endoscopy
- large gastro-oesophageal junction/large diaphragmatic hiatus

Fluroscopy
- specifically for hiatal hernias that undergo spontaneous reduction

Question 20

Can medical therapy correct a hiatal hernia?

Answer 20

Usually only palliative
- mucosal protectants, e.g. sucralfate
- H2 blocking agents, e.g. omeprazole

Surgical correction usually required

Question 21

Briefly describe the surgical management of a hiatal hernia

Answer 21

• surgical reduction of the oesophageal hiatus
• pexy of the cardia of the stomach to the diaphragm
• left-sided tube or incisional gastropext to place caudal traction on the stomach and reduce chances of reherniation

Question 22

What % of patients post hiatal hernia repair experience continued regurgitation?

Answer 22

Up to 50%

Question 23

Briefly describe the anatomy of the pancreas

Answer 23

• bilobar structure - right and left lobes
• lobes joined at pancreatic body
• angle formed between the pancreatic body by the two lobes is smaller in cats than dogs
• right = duodenal lobe; located in the peritoneal fold of descending duodenum; in cats the distal third curves cranially, giving a hook-like appearance ending close to the vena cava; easily exposed via the duodenal manoevre
• left lobe positioned in a dorsal fold of the omentum; begins at the pylorus and extends along the greater curvature of the stomach to the dorsal extremity of the spleen; exposure best achieved by retraction of the stomach and greater omentum cranially, which retracting the transverse colon caudally
• body of the pancreas is adjacent to the proximal duodenum

Question 24

What is the vascular supply to the pancreas?

Answer 24

Arterial:
- tripartite
- cranial pancreaticodurodenal artery, terminal branch of the gastroduodenal arter
- pancreatitc artery, in 80% of dogs branching from the splenic artery and 20% the pancreatic artery
- caudal pancreaticoduodenal artery, arising from the cranial mesenteric artery

Venous:
- pancreaticoduodenal vein
- splenic vein

Question 25

What innervates the pancreas?

Answer 25

Vagal nerve fibres, that when stimulated cause an increase in pancreatic juice production and secretion Coeliac and superior mesenteric plexus innervate the blood vessels which supply the pancreas

Question 26

What are the main differences in pancreatic duct anatomy between the dog and cat?

Answer 26

Dog: - two pancreatic ducts 1. Pancreatic 2. Accessory Cat: - in 80% will only have accessory pancreatic duct

Question 27

What are the fibrotic nodules (1-2 mm) commonly found on the pancreas of older dogs and cats?

Answer 27

Incidental findings, likely resulting from previous bouts of pancreatitis.

Question 28

List indications for a partial pancreatectomy?

Answer 28

- focal pancreatic trauma - isolated pancreatic masses, pseudocysts or abscesses

Question 29

What percentage of the pancreas can be removed without affecting exocrine and endocrine function?

Answer 29

75-90%

Question 30

Why should a total pancreatectomy NOT be attempted by an inexperienced surgeon?

Answer 30

Extremely difficult to remove right pancreatic lobe while sparing share blood supply to the duodenum.

Question 31

List common surgical conditions of the pancreas?

Answer 31

1. Insulinoma 2. Gastrinoma 3. Glucagonoma 4. Exocrine pancreatic neoplasia 5. Pancreatitis - controversial 6. Pancreatic abscess 7. Pancreatic pseudocyst

Question 32

Why should careful handling of a pancreatic insulinoma occur?

Answer 32

Excessive manipulation can lead to increased insulin secretion, leading to a more profound hypoglycaemia

Question 33

What does persistent hypoglycaemia following insulinoma removal indicate?

Answer 33

1. Residual tumour 2. Undetected masses

Question 34

What are foreign bodies more likely to become lodged in the small intestine rather than the oesophagus or stomach?

Answer 34

The small intestine has a markedly reduced distension ability over the oesophageous or stomach.

Question 35

Briefly describe the key features of the anatomy of the small intestine.

Answer 35

Tethered by mesentery arising from the mesenteric root Mesenteric artery and vein, intestinal lymphatics and large mesenteric nerve plexus arborise in the mesenteric root Relatively immobile duodenum, long and mobile jejunum and short ileum Duodenum: - continuous with pylorus of the stomach - position changes dependent on the colonic and bladder filling - cranially has the right limb of the pancreas within the short mesoduodenum - pancreatic ducts and CBD enter the duodenum - 75% of dogs have two pancreatic ducts - only 20% of casts have an accessory pancreatic duct Jejunum: - longest part of SI - series of loops around the root of the mesentary - contains cranial mesenteric vessels, lymphatics and mesenteric nerve plexus - in contact with majority of organs, but rarely extends into the pelvic cavity - covered ventrally and laterally by omentum - cranial mesenteric artery branches into ileocolic and caudal pancreicoduodenal arterties before branching into 12-15 jejunal arcadial arteries, which in turn branch into terminal arcadial vessels which supple the jejunum by multiple vasa recti that penetrate and supply all layers of the intestinal wall Ileum: - terminal region of SI - gross characteristic is an antimesenteric ileal vessel within the ileocolic fold, the artery arising from the ileocaecal artery - mesenteric ileal artery is a branch of the ileocolic and last jejunal arteries - ileum otherwise grossly the same as the jejunum - joints the LI at the ileocolic valve

Question 36

Describe the blood supply, lymphatic drainage and innervation to the SI

Answer 36

Blood supply - arterial 1. pancreaticoduodenal arteries - cranial artery from hepatic artery from the coeliac artery - caudal artery from cranial mesenteric artery 2. Jejunal arteries - branch from cranial mesenteric artery 3. Ileal arteries - branch from cranial mesenteric artery Lymphatics - duodenum to hepatic and duodenal LNs - jejunum and ileum from right and left mesenteric LNs - additional drainage from ileum to colic LNs Innervation - duodenum from thoracolumbar ganglia and distal ganglia - jejunoileum from vagus nerve, from the ceoliac plexus, and the splanchnic nerve, from the cranial mesenteric plexus

Question 37

Describe the layers of the intestinal wall

Answer 37

Mucosa, submucosa, muscularis and serosa Presence of villi mean 8.5 times greater area of mucosa to serosa, of which may contribute to mucosal eversion during enteric surgery Submucosa is the holding layer

Question 38

Describe healing in the small intestinal tract

Answer 38

1. Lag - days 1-4 - macrophages invade the wound and deliver cytokines that stimulate and facilitate fibroplasia and angiogenesis - by day 3 epithelial migration, sealing the wound - dehiscence most likely to occur within first 72-96 hours as fibrin seal is weakened by fibrinolysis - all support from sutures 2. Proliferative phase - day 3/4 to 14 days - proliferation of fibroblasts - marked increase in immature collagen production, resulting in rapid gain in wound bursting strength - by day 14 wound strength will have reached normal levels 3. Maturation phase - of little clinical importance - continues from day 14 to day 180 (6 months) - reorganisation and remodelling as the collagen fibres selectively resorbed/form important cross links - process dependent on intramural tension

Question 39

List examples of host factors that may affect wound healing in the small intestine.

Answer 39

Question 40

What is the medical term form an omental pedicle wrap?

Answer 40

Omentoplasty

Question 41

What are the benefits of omentoplasty procedures?

Answer 41

stimulate and augment angiogenesis reduce wound 'leak-rates' increase wound-bursting strength well described in veterianary studies recent human studies have questioned the value of omentum in augmenting wound healing

Question 42

Describe the pathophysiology of intestinal obstruction

Answer 42

Question 43

Describe the pathophysiology of small intestinal strangulation

Answer 43

Question 44

List and describe the clinical signs associated with small intestinal obstruction

Answer 44

Question 45

What are patients at risk of if surgical correction of strangulation occurs WITHOUT prior fluid resuscitation?

Answer 45

Reperfusion injury

Question 46

List differential diagnoses for cats and dogs presenting with vomiting, diarrhoea and weight loss.

Answer 46

Question 47

Describe the minimum database required

Answer 47

CBC/haematology Serum biochemistry Blood gas analysis (if available), if not electrolytes Urinalysis

Question 48

How is a small intestine obstruction diagnosed radiographically?

Answer 48

Comparing luminal diameter to the height of the body of the fifth lumbar vertebra at its narrowest point. Should be < 1.6 in a normal intestine. Ratio of > or = 1.95 gives a > 80% chance of SI intestine obstruction.

Question 49

When performing a radiographic contrast study how frequently should radiographs be performed?

Answer 49

Prior to contrast, immediately after administration, and every 15 minutes for first hour; then every 45 to 60 minutes until contrast medium reaches the colon.

Question 50

How long should gastric emptying take in a radiographic contrast study?

Answer 50

Begin within 30 minutes, mostly empty within 1-2 hours. Reach colon within 4-6 hours.

Question 51

What contast medium can be used in the integrity of the GIT is in question?

Answer 51

Use iodine-based contrast over barium.

Question 52

What are some indications for enterotomy vs enterectomy?

Answer 52

Enterotomy: - removal of solid or linear FBs - intestinal biopsy Enterectomy (+ anastomosis): - intestinal perforation - neoplasia - non-reducible intussception - poor intestinal viability and/or necrosis

Question 53

Describe key factors of an intestinal biopsy?

Answer 53

- longitudinal or circular - full-thickness - adequate amount of each intestinal wall layer is obtained

Question 54

Describe features of an enterotomy site?

Answer 54

longitudinal on antimesenteric border

Question 55

How should the enterotomy site be closed?

Answer 55

Holding layer of intestine = submucosa Simple appositional suture patterns Will lead to a small degree of eversion and inversion histologically, although clinical results are good No double-layer closure as will reduce intestinal lumen and have poor submucosal apposition - will heal slower via secondary intention Everting patterns should be avoided as may cause adhesions to develop

Question 56

Describe types of assessments made with small intestine?

Answer 56

Question 57

Describe the placement of a jejunostomy tube

Answer 57

Question 58

List major and minor complications of a jejunostomy tube?

Answer 58

Major: - seperation of jejunum form body wall due to failure of jejunopexy leading to intestinal contents leakage and associated inflammation and peritonitis Minor: - tube obstruction with difficulty in administering contents - localised inflammation or cellulitis Complication rate of 15-40%

Question 59

% of FBs found that are solid in nature?

Answer 59

Dogs = 63-84% Cats = 67% Versus linear or other FBs

Question 60

Small intestinal FB %

Answer 60

37-63% of all GIT obstructions in dogs and cats Complete obstruction in 70% of dogs and 42% of cats

Question 61

Survival rates for SI FBs?

Answer 61

Solid FBs: Dogs = 94% Cats = 100% Linear FBs: Dogs = 80% Cats = 63% Dehiscence rates < 5%

Question 62

Describe the appearance of SI with linear FBs?

Answer 62

Plication due to anchor effect

Question 63

Describe the components of an intussusception?

Answer 63

Intussusceptum = invagination of a portion of the intestine Intussuscipiens = into the lumen of another

Question 64

What are the directions of intussusception?

Answer 64

1. Retrograde direction, e.g. duodenogastric intussusception 2. Normograde direction, i.e. SI --> LI (more common) Majority involve enterocolic junction in dogs and the small intestine in cats.

Question 65

What is the recurrence rate for intussception?

Answer 65

10-30% regardless of location and if reduced manually or resected

Question 66

Why do perineal hernias occurs?

Answer 66

Weakness or separation of the components of the pelvic diaphragm. This permits deviation and dilation of the rectum and caudal protrusion of the various abdominal organs, including prostate gland, cystic paraprostatic tissue, bladder, and intestine into the perineum.

Question 67

What is the most common atrophied muscle with perineal hernias?

Answer 67

Levator ani muscle

Question 68

What is the most common location for perineal hernias to occur?

Answer 68

Between levator ani, internal obturator, and external anal sphincter muscles (termed a caudal perineal hernia). Can also uncommonly occur dorsolaterally (between the coccygeus and levator ani muscles), ventrally (between the ischiourethralis, bulbocavernosus, and ischiocavernosus muscles), or laterally (between the coccygeus muscle and the sacrotuberous ligament), which is also known as a sciatic perineal hernia.

Question 69

Describe the anatomy of the perineum.

Answer 69

Question 70

Describe the aetiology of perineal herniation in dogs

Answer 70

- prevalence 0.1-0.4% - exclusively in older, in tact males, who constitute 83-93% of cases - dogs aged 7-13 years most commonly affected - short-tailed breeds commonly affected - suggesting that structural weakness of pelvic diaphragm may be secondary to underdevelopment of levator ani and coccygeus muscles - multifactorial causes - congenital predispositions, anatomic predisposition (short or docked tail), rectal abnormalities, hormonal imbalance, prostatic enlargement, prostatic cysts or abscesses, intrapelvic masses (e.g. lipoma), and structural weakness of the pelvic diaphragm due to muscle degeneration or myopathy. - persistent straining may weaken pelvic diaphragm - between 25 and 50% of dogs with perineal hernia will also have concurrent prostatic disease

Question 71

What percentage of perineal hernias include bladder retroflexion?

Answer 71

20-29%

Question 72

What percentage of perineal hernias are unilateral vs bilateral?

Answer 72

Unilateral 47-66% Right-sided in 59-84% of cases of unilateral perineal hernias

Question 73

What percentage of unilateral perineal hernias operated on develop contralateral herniation with 1-3 years postoperatively?

Answer 73

10%

Question 74

What are the aims of perineal hernia surgical intervention?

Answer 74

1. Removal of faecal material from the rectum 2. Return of herniated viscera to normal position 3. In some cases anchoring viscera in position 4. Closure of the hernia defect by reconstructing the pelvic diaphragm

Question 75

What techniques for perineal hernia surgical intervention exist?

Answer 75

1. Traditional herniorrhaphy 2. Internal obturator transposition 3. Semitendinosus transposition 4. Superficial gluteal transposition 5. Prosthetic implants/biomaterials

Question 76

What important structures should be avoided with perineal hernia correction?

Answer 76

- internal pudendal and caudal rectal vessels - caudal rectal nerve

Question 77

Describe a traditional herniorrhaphy technique

Answer 77

Question 78

What are the advantages of the internal obturator muscle transposition? Describe the technique.

Answer 78

Advantages (over traditional herniorrhaphy): 1. reduces tension on approximating sutures, thus reduces distortion of the external anal sphincter 2. brings in additional muscular tissue and blood supply, improving healing and preventing breakdown Recommended procedure of choice for bilateral or more severe perineal hernias. Key point is to no pass more cranial than the caudal edge of the obturator foramen. This prevents concurrent damage to the obturator nerve and artery. As elevation occurs 3 tendon bands will emerge. Transect tendon medially to the point where it passes laterally over the body of the ischium to prevent damage to the sciatic nerve. Care to avoid the blood vessel that runs immediately cranial to the tendon. Muscle is transposed medially and dorsally to fill the hernial defect.

Question 79

What other adjunctive procedures may occur during repair of a perineal hernia?

Answer 79

Organopexies: 1. Colopexy - Descending colon and LEFT body wall +/- reduction in luminal size to reduce accumulation of faeces and to prevent caudal migration of the dilated rectum 2. Cystopexy - RIGHT bladder neck and RIGHT lateral abdomen 3. Vas Deferensopexy - relocation of enlarged prostate gland and bladder Neutering: 1. Open castrations - seperation of testicular artery/vein from vas deferens will allow an easier vas deferensopexy to occur Same as gastropexy with partial thickness incisional pexy procedures.

Question 80

List complications of perineal hernia repair, including complication rates.

Answer 80

- overall complication rate 5-68% - traditional technique 29-61% - internal obturator muscle transposition technique 19-45% - superficial gluteal technique 15-58% - perineal swelling - wound infection and abscessation - wound dehiscence - seroma formation - anorexia - faecal incontinence - sciatic nerve entrapment - urethral trauma - anuria - urinary incontinence - urinary tract infection - stranguria - inadvertent prostatectomy - tenesmus - dyschezia - haematochezia - faecal impaction - megacolon - diarrhoea - rectal prolapse - rectocutaneous fistula - anal sac fistulation - flatulence - pain on defecation - recurrence Recurrence rates 0-70%

Question 81

Describe the following for GDV (gastric dilatation and volvulus) in dogs: 1. Predisposing factors for GDV 2. Proposed pathogenesis and pathophysiology of GDV both a the local level of the stomach, and distant systemic level 3. Prognostic factors that dictate outcomes relating to GDV

Answer 81

1. Predisposing factors for GDV - purebred large or giant breed - increased thoracic depth-to-width ratio - history of GDV in first-degree relative - fewer feeds per day - rapid eating - aggressive or fearful temperament - decreased food particle size - increased hepatogastric ligament length - exercise or stress after meal 2. Proposed pathogenesis and pathophysiology at the level of the stomach and systemically Pylorus and proximal duodenum move ventrally and cranially, stretching hepatoduodenal ligament allowing movement of the pylorus that is not normally possible. Pylorus moves from RIGHT to LEFT, creating fold in the stomach, eventually resting dorsally to the oesophagus on the LEFT abdomen. Eructation prevented, allowing aerophagia and dilatation to occur, increasing intragastric pressure, decreasing venous flow through the abdomen by direct compression. Portal hypertension, systemic hypotension and cardiogenic shock result. Stomach level: 1. Gastric wall necrosis = capillaries collapse secondary to intragastric pressure, resulting in subsequent necrosis of gastric mucosa. Coupled with systemic hypotension full-thickness gastric wall necrosis occurs. Also contributed by avulsion of short gastric arteries. 2. Bacterial translocation = poorly reported in some studies Systemic level: 1. Blood flow = increased intraabdominal pressure, decreasing venous flow through abdomen. Specifically venous return from caudal vena cava is reduced, resulting in cardiogenic shock. Portal vein compression results in portal hypertension, producing venous stasis and subsequent mucosal death and bacterial translocation. Reduced blood to liver results in reduced clearance of bacteria and endotoxins. 2. Respiration = pressure on the diaphragm from distended stomach makes inspiration difficult and further decreases oxygen delivery. 3. Cardiac dysfunction = complex and multifactorial, but ultimately inadequate coronary vessel flow, coupled with production of myocardial depressant factor results in myocardial ischaemia. ECG abnormalities reported in 40-70% of dogs with GDV. 4. Reperfusion injury = associated with correction of malposition of stomach and the return of normal blood flow. 3. Prognostic factors - mortality: duration of clinical signs > 6 hours, concurrent gastrectomy or splenectomy, presence of hypotension, gastric necrosis, preoperative cardiac arrhythmias, peritonitis, sepsis or DIC - decreased mortality with increased time from presentation to surgery - lactate > 42.5% change positive prognostic factor - high myoglobin levels > 168 ng/ml