Grace Yu, Medical Student

1
Case Presentation

• Grace Yu, Medical Student
• Surgery Core Clerkship
• July 2004

2
Case

• 79 y/o F h/o Afib presents c 3 month h/o near
  syncopal episodes associated c transient
  confusion and slurred speech admitted to
  hospital.
• PE nml except for tachycardia 110. EKG Afib c
  rapid ventricular rate. TTE nml. CT brain showed
  AVM.
• Hospital course successful cardioversion. Not
  given anticoagulation before cardioversion b/c
  AVM considered contraindication. Coronary
  angiography recommended for neurosurgery and
  underwent cardiac catherization.

Sirmon, M. The Invisible Patient. NEJM 334 (14)
908-911. 1996
3
Case

• 6 hours after catherization, severe generalized
  abdominal pain, nausea, vomiting, and diarrhea.
  Stool tested positive for occult blood. WBC
  increased to 21K with L shift. Abdominal films
  revealed nml gas distribution in the small and
  large bowels without free air.
• The pain persisted, and the following day the pt
  passed BRBPR. Examination revealed mild
  abdominal distension, hypoactive bowel sounds,
  and voluntary guarding. She underwent
  esophagogastroscopy with unremarkable findings,
  followed by colonoscopy, which revealed bloody
  mucus but no evidence of ischemic colitis. WBC
  increased to 29K and metabolic acidosis
  developed.

Sirmon, M. The Invisible Patient. NEJM 334 (14)
908-911. 1996
4
Case

• Abdominal exploration revealed gangrenous bowel,
  extending from ligament of Treitz to the hepatic
  flexure of the colon. No further surgery was
  performed and the incision was closed. The pt
  died 12 hrs later.

Sirmon, M. The Invisible Patient. NEJM 334 (14)
908-911. 1996
5
Diagnosis?

• Acute Mesenteric Ischemic
• Atheroemboli dislogded during cardiac
  catherization

6
Definition

• Abrupt reduction in blood flow to intestinal
  circulation of sufficient magnitude to compromise
  metabolic requirements and potentially threaten
  the viability of affected organs.

7
Epidemiology

• Incidence as high as 1 in 1,000 pts
• Expected to increase c aging population
• Despite growing awareness, morbidity and
  mortality remain high
• Mortality 59-93

8
Pathophysiology

• 10-30 resting C.O. devoted to intestinal blood
  flow
• Most directed towards mucosa, layer c greatest
  metabolic demand and highest rate of cell
  turnover
• Sudden reduction blood flow - organ ischemia
  specifically compromising mucosa
• Inflm cell infiltrate, loss of capillary
  integrity c bowel wall edema - bacterial
  translocation, endotoxemia, exudation of fluid
  from small bowel.
• Injured mucosa sloughs - ulceration - necrosis
  of muscularis and serosa
• Septic shock, MSOF

9
(No Transcript)
10
Etiology?

• 4 types
• Mesenteric Arterial Embolus
• Mesenteric Arterial Thrombosis
• NonOcclusive Mesenteric Ischemia (NOMI)
• Mesenteric Venous Thrombosis (MVT)

11
1. Mesenteric Arterial Embolism

• 50 AMI cases
• Perferentially lodges SMA
• Causes of Emboli
• p MI akinetic or aneurysmal portion LV c
  thrombus
• Afib LA mural thrombus
• Bacterial endocarditis septic emboli
• Intracardiac shunt paradoxical embolus from LE
  DVT
• Atheroemboli dislodging spontaneously from
  proximal aorta
• Catheter manipulation during endovascular
  procedure
• Some cases, source embolic occlusion never
  identified

12
50
13
2. Mesenteric Artery Thrombosis

• Atherosclerotic occlusive lesions tend to occur
  at origins, or very proximal segments, of the
  mesenteric vessels
• Stenosis usu progresses over number of years and
  pts remain symptom free if adequate collateral
  circulation
• Thrombosis of residual lumen often occurs during
  periods of relative hypotension or reduced flow
  (e.g. dehydration)
• In some cases, hemorrhage into wall of
  atherosclerotic plaque leads to complete
  occlusion of vessel lumen.

14
2. Mesenteric Artery Thrombosis

• Chronic AS most common etiology
• Other entities
• Aortic aneurysm
• Arterial dissection
• Isolated dissection of mesenteric vessel
  spontaneously or result of catheter
• Fibromuscular dysplasia
• Vasculitidies (e.g. Takayasus arteritis)
• Hypercoaguable state

15
3. Nonocclusive Mesenteric Ischemia (NOMI)

• Severe mesenteric vasoconstriction
• Causes
• shock (septic, cardiogenic, hypovolemic)
• relative dehydration or hypoperfusion severe
  diarrhea, third spacing (burns, peritonitis)
• Alpha adrenergic agonists (phenylephrine, NE,
  Epi)
• Other drugs (ergot alkaloids, diuretics,
  digitalis, cocaine, etc.)

16
4. Mesenteric Venous Thrombosis (MVT)

• Thrombus typically in portal or superior
  mesenteric venous system - intestinal ischemia
• Increased hydrostatic pressure leads to luminal
  fluid sequestration and bowel wall edema
• Ensuing relative hypovolemia and
  hemoconcentration may contribute to
  vasoconstriction - infarction
• Causes
• Hypercoagulable states (e.g. polycythemia vera,
  OCPs, inherited)
• Traumatic injury
• Obstruction venous flow (e.g. portal HTN,
  abdominal tumors)
• Intra-abdominal infxn or inflm (appendicitis,
  diverticulitis, abscess)
• Epi younger, 30-60 y/o, FM
• Classification
• acute 4 wks
• primary MVT - no precipitating factor identified
  (20) vs.secondary MVT - known cause (80)

17
(No Transcript)
18
History Classic Triad SMA embolism
Acute onset abdominal pain
Gut emptying (Vomiting, diarrhea)
Hx Afib, heart dx
19
History

• 12. AMI secondary to embolus or thrombus
• 7th-8th decades
• CAD, PVD, cardiac dysrhythmias
• Abdominal Pain
• Acute onset with rapid progression over few hours
  most typical of embolic occlusion
• May be colicky initially - sustained as bowel
  viability compromised
• Diffuse or localized to any quadrant of abdomen
• Vomiting, diarrhea
• Occult blood stool - frankly bloody diarrhea

20
History

• Pts c thrombosed vessel c collaterals may have
  more insidious onset c prodrome of anorexia,
  malaise, vague sxms - evolve into frank distress
  over a few dys
• Weight loss, recent illness, changes in eating
  habits, postprandial discomfort leading to food
  aversion (abdominal angina) helps to
  differentiate thrombotic from embolic etiologies,
  although acute arterial thrombosis may have no
  sxms prior to acute event.
• Precipitating event may be sudden drop in C.O.,
  MI, CHF, ruptured plaque, dehydration

21
History

• 3. Nonocclusive mesenteric ischemia Especially
  difficult b/c many pts already critically ill in
  ICU, obtunded, Hx unattainable
• Rare, potentially life-threatening in cardiac
  surgery pts
• Incidence 0.06-0.36
• RF emergent procedures, prolonged pump time,
  IABP, advanced age, failed coronary angioplasty
• Occurs dys after initial procedure with mean
  abdominal exploration time 4-9 dys p cardiac
  surgery
• Delay may be secondary vent support/sedation
  resulting in less accurate PE

22
History

• 4. Mesenteric Vein Thrombosis
• RF hypercoagulable state (e.g. inherited, OCP,
  DVT, cancer, tumor, portocaval surgery)
• Insidious onset over 7-14 dys
• 48 hrs in 75 pts
• w/in 24 hrs only 9 pts
• Poorly localized pain associated c
• Abdominal distension
• Anorexia
• N/V
• Diarrhea

23
Physical

• Sine qua non severe abdominal pain out of
  proportion to physical exam findings early in
  course of illness
• Dehydration signs dry mucus membranes, decreased
  skin turgor, flat neck veins
• Hypoperfusion seen in NOMI cool extremities c
  faint or absent pulses, mottled skin
• CV arrhythmias (Afib) for embolic, CHF
• GI abdominal bruits, scars
• Early abdomen soft, NT, NABS
• Ischemia progresses guarding, hypoactive bowel
  sounds, absent bowel sounds, distension, ascites,
  Hemoccult positive stools, bloody diarrhea
• Later progressive guarding, peritonitis as
  full-thickness intestinal ischemia, necrosis,
  perforation. Tenderness severe and may localize
  to infarcted bowel segment. Tachycardia,
  hypotension, tachypnea, altered mental status

24
Labs

• CBCD
• Chem 10
• Coags
• LFTs
• Amylase
• ABG
• Lactate
• Advanced intestinal ischemia - leukocytosis
  metabolic acidosis, elevated lactate elevated
  amylase level, LDH, CPK, AST but non-specific
• Hemoconcentration c/w dehydration ubiquitous in
  NOMI
• However, absence should not dissuade from
  suspecting mesenteric ischemia.
• No clear markers to establish or exclude AMI and
  labs are generally not helpful.

25
Studies

• Abdominal XRays
• r/o other causes perforated viscus, small or
  large bowel obstruction
• Often nml in AMI and positive findings usu late
  and non-specific
• thumbprinting, bowel wall thickening
• Pneumatosis intestinalis bowel infarction
• rarely seen (5)
• Also associated c other benign findings (e.g.
  COPD, IBD, mechanical ventilation)
• Air in portal venous circulation, bilary tree,
  free peritoneal air
• Late findings c/w bowel necrosis
• Paucity of bowel gas and adynamic ileus
• Most frequent finding in MVT

26
Pneumatosis Intestinalis
27
Studies

• CT, CTA
• May be nml or nondiagnostic
• Series of 39 pts, 64 sensitive, 92 specific c
  at least one finding
• Arterial or venous thrombosis
• Intramural gas
• Portal venous gas
• Thickened BW
• Liver or spleen infarcts
• Diagnostic choice in MVT, sensitivity 90
• Superior mesenteric or portal vein enlarged c
  central areas of attenuation suggestive of
  thrombus.
• BW thickening and presence of ascites also
  suggestive

28
34 y/o woman c nonspecific abdominal pain c
protein C deficiency
29
Other studies

• MRI/MRA similar findings as CT scan, major
  drawback expense and time
• Duplex US exam of mesenteric circulation
• Useful in chronic mesenteric ischemia
• Distended bowel loops limits role in AMI
• Does not exclude embolic phenomenon, but absence
  flow and ascites highly suggestive MVT
• ECHO - Confirm source of emboli
• EKG MI or Afib
• Endoscopy - dx ischemic colitis but does not
  visulaize much of small bowel which is frequently
  involved
• Barium studies
• Contraindicated as increased intraluminal
  pressure - perforation and residual barium may
  obscure crucial angiographic findings

30
Arteriography Gold Standard
31
Arteriography

• Establishes dx, differentiates between
  thrombotic, embolic, and non-occlusive
  etiologies, allow early nonoperative therapeutic
  intervention, allows surgeon select appropriate
  operative approach
• Biplanar (AP and lateral) views of aorta and
  branches

32
Arteriography Findings Based on Etiology

• Acute Thrombotic occlusion
• Origin of SMA or celiac axis c opacification of
  short segment of these vessels may see
  collaterals
• Diffuse atheromatous disease in abdominal aorta
• Acute Embolic occlusion
• Inverted meniscus sign several cm distal to
  origin of SMA usu at origin of middle colic
  artery
• SMA, other mesenteric vessels, abdominal aorta
  relatively undiseased
• Poor collaterals, multiple emboli

33
Lateral arteriogram embolus in SMA several cm
from origin
34
Arteriography Findings Based on Etiology

• MVT
• Not as helpful esp segmental venous thrombosis
• Most importantly, can exclude embolus, thrombus,
  NOMI
• NOMI
• Mesenteric vessels may be patent w or w/o
  evidence of chronic disease
• Intermittent areas of narrowing and dilatation
  (string of sausages) c/w arterial
  vasoconstriction of spasm
• Dx test direct infusion papaverine (60mg) into
  SMA can reverse vasoconstricion and confirms
  diagnosis - can leave catheter in place for
  continuous therapeutic infusion

35
NOMI intermittent spasm and dilatation of vessels
string of sausages
36
Medical Rx

• Substantial protein-rich fluid losses in gut
• Supportive Rx
• Aggressive fluid resuscitation
• Guided by art line, Foley, central line,
  Swan-Ganz
• Volume resuscitation to allow weaning of
  vasopressors
• NE and Phenylephrine particularly deleterious
• Dopamine more appropriate as may cause less
  severe mesenteric vasoconstriction
• Digitalis well-recognized vasoconstrictor of SMA
  smooth muscle and d/ced if possible
• NPO
• NG decompress fluid-filled and distended
  intestinal tract to promote perfusion, decrease
  risk perforation, minimize aspiration risk
• Broad-spectrum ABx including anaerobes given
  bacterial translocation through compromised
  intestinal barrier and documented hi incidence of
  positive blood cultures
• Respiratory support (100, intubation if
  necessary), pain control

37
Medical Rx

• Anticoagulation dependent on etiology of AMI
• MVT
• Heparin decreases recurrence thrombosis 26-14
  and mortality 59-22
• Long-term anticoagulation c warfarin, esp if
  underlying hypercoagulable state
• Acute arterial thrombosis or embolus
  anticoagulation problematic
• Early heparin administration can prevent thrombus
  extension, benefit must be weighed against risk
  of significant GI bleed in bowel ischemia
• In most cases, urgent surgical exploration
  required and anticoagulation should be held
  pre-operatively
• Post-op anticoagulation recommended in those c
  embolic occlusion, but may not be necessary after
  revascularization for thrombosis

38
Interventional Radiology

• Unlike other causes of AMI, primary treatment of
  NOMI is pharmacologic
• Catheter directed administration of number of
  vasodilating agents including papaverine,
  tolazoline, glucagon, NTG, NTP, prostaglandin E,
  phenoxybenzamine, isoproterenol
• Most clinical experience c papaverine
• 60mg c repeat contrast injection demonstrates
  reversal of vasoconstriction
• Catheter left in place c continuous infusion _at_
  30-60mg/hr
• Acccompanied by heparin to prevent propagation of
  thrombus during low-flow state or formation at
  catheter site
• Failure to improve or deterioration mandates
  immediate surgical exploration
• Catheter may be left in place post-operatively to
  maximize perfusion of marginally viable bowel
  after resection of frankly gangrenous segments

39
Interventional Radiology

• Catheter directed thrombolysis anecdoctal
• Risk of intestinal hemorrhage
• Elderly pt c severe medical co-morbidities and
  clinical presentation of early ischemia, this Rx
  may avoid potentially morbid surgery, esp if
  bowel viability can be confirmed through
  laparascopy
• Percutaneous transluminal angioplasty
• After successful lysis thrombus, can treat
  underlying chronic occlusive disease c PTA
• Matsumoto et.al. documented technical success
  102/126 (86) underwsent PTA of chronic visceral
  arterial lesions
• Major complicatons 6

40
Surgical Rx

• Operative delay is the most important determinant
  of adverse outcome
• Goal to confirm diagnosis of mesenteric ischemia,
  assess bowel viability, perform revascularization
  if possible, and resect nonviable bowel

41
Surgery

• OR equipped Woods lamp, fluorescein, continuous
  wave Doppler U/S
• Pt supine c wide field extending nipples to knees
  prepped and draped to allow harvesting GSV if
  necessary
• Abdomen entered long midline incision and bowel
  carefully examined from stomach to rectosigmoid.
  A definite determination of intestinal viability
  should not be made until revascularization
  performed
• Palpation of pulsations or Doppler signals in
  peripheral of mesentery may represent collaterals
  - this finding does not r/o SMA occlusion
• SMA isolated at base of mesentery at it exits
  underneath pancreas and exposed several cm
  distally
• Strong pulsation at base but not palpable
  distally highly suggestive embolus, whereas
  absent pulsation in proximal SMA suggestive
  thrombus
• Use Doppler if no pulses detectable
• Examine celiac axis, IMA, and main branches

42
Surgery

• Inspection of bowel can uncover etiology
• Acute SMA thrombosis typically compromises
  viability R colon and entire small intestine
• Embolic occlusion lodges more distally and
  proximal jejunum may be spared, and more patchy
  involvement in pts c multiple distal emboli
• MVT marked edema of intestine and mesentery,
  cyanotic discoloration bowel, palpable mesenteric
  arterial pulsations
• NOMI peripheral arterial pulsations c distal
  attn noted in absence of apparent thrombosis -
  minimize arterial manipulation to avoid further
  vasoconstriction - urgent transfer to
  angiography for vasodilatory Rx

43
Surgery

• Revascularization for Embolus
• SMA controlled distal to origin of middle colic
  artery and proximal to jejunal arteries and
  arteriotomy performed
• Transverse arteriotomy or if any doubt,
  longitudinal to serve as distal anastomosis of
  bypass graft
• Thrombombolectomy cathether can retrieve embolus
  and thrombotic material
• Also may be possible to milk clot manually from
  distal vasculature
• Infuse heparin distally and for smaller
  thromboemboli thrombolytics may be used
• Infuse vasodilator (e.g. papaverine) into distal
  vessel before closing
• Primary closure or patch angioplasty

44
Surgery

• Revascularization for Thrombus
• Thromboendarterectomy
• Bypass graft - many options for
• conduit used (GSV, synthetic Dacron or
  polytetrafluoroethylene)
• inflow used (infrarenal or supraceliac aorta)
• extent of revascularization

45
Surgery

• Mesenteric Vein Thrombosis
• Primary Rx anticoagulation
• Thromboembolectomy catheter used to extract clot
• Peripheral veins milked to extract as much
  thrombus as possible
• When thrombotic process involves more distal
  small venous channels, bowel resection may be
  only option as common for MVT to extend well
  beyond what appears to be compromised bowel -
  wide margin for resection and low threshold for
  second-look operation

46
Surgical Resection

• Bowel returned to abdominal cavity and
  anesthesiologist maximize hemodynamic status for
  30-45 min before making definitive assessment of
  intestinal viability and necessity for bowel
  resection
• Clinical signs (absence peristalsis, bowel wall
  edema, discoloration of bowel and mesentery,
  mucosal hemorrhage, absence of bleeding from cut
  edges) are imprecise markers and may lead to
  excessive resection.

47
Surgical Resection

• Objective modalities
• Continuous wave Doppler ultrasound
• Fluorescein IV with Woods lamp
• Johns Hopkins prospective study fluoroscein 100
  accurate, clinical judgment 89, and Doppler 84
  accurate in predicting bowel viability
• All nonviable bowel resected or long segments
  marginal bowel left in situ with continuity
  reestablished during second-look procedure 18-24
  hrs later

48
Postoperative Care
49
Postoperative Care

• Primary focus vigorous cardiopulmonary
  resuscitation, esp in NOMI and recognized
  mesenteric capillary leak syndrome
• Aggressive blood and electrolyte rich fluids
• May require 10-20L crystalloid in first 24-48 hrs
  
• Correction arrhythmias
• Vasopressors
• Dopamine 3-8mcg/kg/min, Epi 0.05-0.10 ug/kg/min.
• Pure alpha agonists should be avoided
• Limit reperfusion injury with free oxygen
  scavengers ACEI, Allopurinol
• Correct metabolic acidosis
• Sepsis common Broad spectrum ABx with anaerobic
  coverage for at least 5 dys
• Prolonged NG decompression
• Early institution of parenteral nutrition

50
Postoperative Care Anticoagulation

• MVT Anticoagulation mainstay of therapy
• Heparin at time of dx and continued
  postoperatively
• Duration of long-term warfarin depends on
  underlying cause
• Embolus administer heparin
• NOMI anticoagulation generally not necessary
• Most critically ill pts c AMI after
  revascularization, hypocoagulable state secondary
  liver dysfxn - replenish coagulation factors to
  Rx GI bleeding

51
Prognosis

• Overall mortality 60

52
Summary

• Think of mesenteric ischemia in DDx
• Hx
• Classic triad in SMA embolus acute onset, Gi
  emptying (vomiting, diarrhea), and h/o cardiac dz
• Abdominal distension, hemmoccult positive stool,
  bloody diarrhea, h/o abdominal angina
• Co-morbidities CV disease, arryhthmias,
  hypotension, hypercoagulable
• PE - abdominal pain out of proportion to physical
  exam findings early in illness
• Labs non-specific
• Studies CT, Angiogram gold standard
• Rx Medical, IR, Surgery
• Mortality remains high
• Early diagnosis dramatically increases survival

53
References

• Chang, et. al. Mesenteric Ischemia Acute and
  Chronic. Annals of Vascular Surgery. 17 323-329.
  2003
• Dang, C. Acute Mesenteric Ischemia.
  www.emedicine.com/med/topic2627.htm
• Lee. R. et.al. CT in Acute Mesenteric Ischemia.
  Clinical Radiology. 58 279-287. 2003.
• Oldenberg, A. et.al. Acute Mesenteric Ischemia.
  Arch Intern Med. 164 1054-1062. 2004.
• Sabiston textbook of surgery. pg. 1398-1404. W.
  B. Saunders Company. 2001
• Sirmon, M. The Invisible Patient. NEJM 334 (14)
  908-911. 1996.
• surged.utmem.edu/residents/ lecture/slides/MESENTE
  RIC20ISCHEMIA.htm
• Tendler, et.al. Acute Mesenteric Ischemia.
  www.uptodate.com

54
Addendum
55
Results Acute

• Acute Arterial Thrombosis and Embolism
• Survival superior in embolic vs. thrombotic
  arterial occlusion
• Embolic survival 50-77
• Thrombotic survival 80-96
• Mortality increases c extent of bowel ischemia
  and infarction
• Excessive mortality with leukocytosis,
  peritonitis, resection 1.5m intestine
• Mesenteric angiography can define etiology
• Evidence intra-arterial vasodilator therapy
  improves survival 80 mortality - 45 mortality

56
Results Acute

• NOMI
• Mortality 70-90
• Decline in incidence b/c greater awareness by ICU
  physicians and more liberal administration of
  intra-arterial vasodilator
• Intra-arterial papaverine reduced mortality to
  50-55
• Mesenteric Vein Thrombosis
• Lowest risk mortality 11-38
• Younger, healthier population
• Recognition predisposing factors, indolent
  coruse, and CT accuracy in diagnosis b/f bowel
  infarction occurs
• Shorter segments bowel infarcted

57
Results Long-term

• Less studied but relatively favorable prognosis
• 2 year survival rate 70
• 5 year survival rate 50
• Mortality highest during 1st yr
• Common cause of long-term mortality CV
• Recurrent bowel ischemia infrequent b/c
  aggressive long-term anticoagulation
• QOL
• 38 wt loss
• 19 reduced appetite
• Bowel resection, 20 short gut syndrome and none
  required TPN