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Acute Mesenteric Ischemia окончат студ. 2012.ppt

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Acute Mesenteric Ischemiа Acute Mesenteric Ischemiа

Definition A сritical reduction in blood flow to intestinal circulation Definition A сritical reduction in blood flow to intestinal circulation

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

Etiology? 1. 2. 3. 4. 4 types Mesenteric Arterial Embolus Mesenteric Arterial Thrombosis Non. Etiology? 1. 2. 3. 4. 4 types Mesenteric Arterial Embolus Mesenteric Arterial Thrombosis Non. Occlusive Mesenteric Ischemia (NOMI) Mesenteric Venous Thrombosis (MVT)

1. Mesenteric Arterial Embolism l l 50% AMI cases Causes of Emboli l l 1. Mesenteric Arterial Embolism l l 50% AMI cases Causes of Emboli l l l akinetic or aneurysmal portion LV c thrombus 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

50% 50%

2. Mesenteric Artery Thrombosis l l Atherosclerotic occlusive lesions tend to occur at origins, 2. Mesenteric Artery Thrombosis l l Atherosclerotic occlusive lesions tend to occur at origins, or very proximal segments, of the mesenteric vessels Stenosis 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 In some cases, hemorrhage into wall of atherosclerotic plaque leads to complete occlusion of vessel lumen.

2. Mesenteric Artery Thrombosis Chronic AS most common etiology l Other entities: l l 2. Mesenteric Artery Thrombosis Chronic AS most common etiology l Other entities: l l Aortic aneurysm l Arterial dissection l Isolated dissection of mesenteric vessel spontaneously or result of catheter l Fibromuscular dysplasia l Vasculitidies (e. g. Takayasu’s arteritis) l Hypercoaguable state

3. Nonocclusive Mesenteric Ischemia (NOMI) Severe mesenteric vasoconstriction l Causes: l l shock (septic, 3. Nonocclusive Mesenteric Ischemia (NOMI) Severe mesenteric vasoconstriction l Causes: l l shock (septic, cardiogenic, hypovolemic) l relative dehydration or hypoperfusion = severe diarrhea, third spacing (burns, peritonitis) l Alpha adrenergic agonists (phenylephrine, NE, Epi) l Other drugs (ergot alkaloids, diuretics, digitalis, cocaine, etc. )

4. Mesenteric Venous Thrombosis (MVT) l l Thrombus typically in portal or superior mesenteric 4. Mesenteric Venous Thrombosis (MVT) l l 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: l Hypercoagulable states (e. g. polycythemia vera, OCPs, inherited) l Traumatic injury l Obstruction venous flow (e. g. portal HTN, abdominal tumors) l Intra-abdominal infxn or inflm (appendicitis, diverticulitis, abscess)

Pathophysiology l l l 10 -30% resting C. O. devoted to intestinal blood flow Pathophysiology l l l 10 -30% resting C. O. devoted to intestinal blood flow Most directed towards mucosa, layer c greatest metabolic demand 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

ETIOLOGY Incd (%) Age Presentation RF 1. Arterial Embolism 50% Elderly Acute catastrophe Arrhythmias ETIOLOGY Incd (%) Age Presentation RF 1. Arterial Embolism 50% Elderly Acute catastrophe Arrhythmias Recent MI CHF RF, endocarditis, CM, ventricular anuerysms, h/o emblic events, recent angiography High 2. Arterial Thrombosis 25% Elderly Insidious onset, progression constant pain Systemic AS, prolonged hypotension, estrogen, hypercoagul. Very high 3. Nonocclusive mesenteric ischemia 20% Elderly Acute or subacute Shock, hypotension, hypovolemia, CPB, alphaagonists, burns, pancreatitis Highest 4. Mesenteric venous thrombosis 5% Young er Subacute Hypercoag, portal Lowest HTN, Infxn/inflm, prior surgery, trauma Mortality

History: Classic Triad SMA embolism Acute onset abdominal pain Gut emptying (Vomiting, diarrhea) Embolic History: Classic Triad SMA embolism Acute onset abdominal pain Gut emptying (Vomiting, diarrhea) Embolic risk

Stadium of ADMC (AMI) 1. Ischemia (6 -12 h) l 2. Infarct (12 -24 Stadium of ADMC (AMI) 1. Ischemia (6 -12 h) l 2. Infarct (12 -24 h) l 3. Peritonitis (more 24 h) l

History AMI secondary to embolus or thrombus l 7 th-8 th decades l cardiac History AMI secondary to embolus or thrombus l 7 th-8 th decades l cardiac dysrhythmias l Abdominal Pain: l Acute onset with rapid progression over few hours most typical of embolic occlusion l May be colicky initially -> sustained as bowel viability compromised l Diffuse or localized to any quadrant of abdomen l Vomiting, diarrhea l Occult blood stool - bloody diarrhea l Changes of arterial pressure

History Nonocclusive mesenteric ischemia l Rare, potentially life-threatening in cardiac surgery Incidence 0. 06 History Nonocclusive mesenteric ischemia l Rare, potentially life-threatening in cardiac surgery Incidence 0. 06 -0. 36% l emergent procedures, prolonged pump time, failed coronary angioplasty l

History 4. Mesenteric Vein Thrombosis l RF: hypercoagulable state ( DVT, cancer, tumor, portocaval History 4. Mesenteric Vein Thrombosis l RF: hypercoagulable state ( DVT, cancer, tumor, portocaval surgery) l Poorly localized pain associated c: l l Abdominal distension Anorexia N/V Diarrhea

Labs l l Advanced intestinal ischemia -> leukocytosis; metabolic acidosis, elevated lactate; elevated amylase Labs l l 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.

l Abdominal X-rays l l l Studies r/o other causes: perforated viscus, small or l Abdominal X-rays l l l Studies r/o other causes: perforated viscus, small or large bowel obstruction Often nml in AMI and positive findings late and non-specific Pneumatosis intestinalis = bowel infarction Air in portal venous circulation, bilary tree, free peritoneal air l Late findings c/w bowel necrosis Paucity of bowel gas and adynamic ileus l Most frequent finding in MVT

Pneumatosis Intestinalis Pneumatosis Intestinalis

Studies l CT l 64% sensitive, 92% specific c at least one finding: Arterial Studies l CT l 64% sensitive, 92% specific c at least one finding: Arterial or venous thrombosis l Intramural gas l Portal venous gas l Thickened BW l Liver or spleen infarcts l l Diagnostic choice in MVT, sensitivity 90% Superior mesenteric or portal vein enlarged c central areas of attenuation suggestive of thrombus. l BW thickening and presence of ascites also suggestive l

34 y/o woman c nonspecific abdominal pain c protein C deficiency 34 y/o woman c nonspecific abdominal pain c protein C deficiency

Other studies l l Duplex US exam of mesenteric circulation l Useful in chronic Other studies l l Duplex US exam of mesenteric circulation l Useful in chronic mesenteric ischemia l Distended bowel loops limits role in AMI l Does not exclude embolic phenomenon, but absence flow and ascites highly suggestive MVT ECHO - Confirm source of emboli EKG – MI or Afib Endoscopy - ischemic colitis but does not visulaize much of small bowel which is frequently involved

Arteriography = Gold Standard Arteriography = Gold Standard

Arteriography Findings Based on Etiology l Acute Thrombotic occlusion l l l Origin of Arteriography Findings Based on Etiology l Acute Thrombotic occlusion l l l 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 l l l 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

Lateral arteriogram: embolus in SMA several cm from origin Lateral arteriogram: embolus in SMA several cm from origin

Arteriography Findings Based on Etiology l MVT l l l Not as helpful esp Arteriography Findings Based on Etiology l MVT l l l Not as helpful esp segmental venous thrombosis Most importantly, can exclude embolus, thrombus, NOMI l l l 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 (60 mg) into SMA can reverse vasoconstricion and confirms diagnosis > can leave catheter in place for continuous therapeutic infusion

NOMI intermittent spasm and dilatation of vessels “string of sausages” NOMI intermittent spasm and dilatation of vessels “string of sausages”

Medical Rx l l l Aggressive fluid resuscitation l Guided by art line, Foley, Medical Rx l l l Aggressive fluid resuscitation l Guided by art line, Foley, central line, Swan-Ganz Volume resuscitation l Dopamine more appropriate as may cause less severe mesenteric vasoconstriction Nasogastric 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

Medical Rx l l Anticoagulation dependent on etiology of AMI MVT l l l Medical Rx l l Anticoagulation dependent on etiology of AMI MVT l l l 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 l l l 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 anticoagulation should be held pre-operatively Post-op: anticoagulation recommended in those c embolic occlusion, but may not be necessary after revascularization for thrombosis

Interventional Radiology l l l Primary treatment of NOMI is pharmacologic Catheter directed administration Interventional Radiology l l l 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 l l 60 mg c repeat contrast injection demonstrates reversal of vasoconstriction Catheter left in place c continuous infusion @ 30 -60 mg/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 l Catheter may be left in place post-operatively to maximize perfusion of marginally viable bowel after resection of frankly gangrenous segments

Surgical Rx l l Operative delay is the most important determinant of adverse outcome Surgical Rx l l 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

Surgery l Inspection of bowel can uncover etiology l l Acute SMA thrombosis: typically Surgery l Inspection of bowel can uncover etiology l l 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

Surgery Revascularization for Embolus l SMA controlled distal to origin of middle colic artery Surgery Revascularization for Embolus l SMA controlled distal to origin of middle colic artery and proximal to jejunal arteries and arteriotomy performed l Transverse arteriotomy or if any doubt, longitudinal to serve as distal anastomosis of bypass graft l Thrombombolectomy cathether can retrieve embolus and thrombotic material l Also may be possible to “milk” clot manually from distal vasculature l l l 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

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

Surgery Mesenteric Vein Thrombosis l Primary Rx anticoagulation l Thromboembolectomy catheter used to extract Surgery Mesenteric Vein Thrombosis l Primary Rx anticoagulation l Thromboembolectomy catheter used to extract clot l Peripheral veins “milked” to extract as much thrombus as possible l 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

Surgical Resection l l Bowel returned to abdominal cavity and anesthesiologist maximize hemodynamic status Surgical Resection l l 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.

Surgical Resection l Objective modalities: l l Continuous wave Doppler ultrasound Fluorescein IV with Surgical Resection l Objective modalities: l l Continuous wave Doppler ultrasound Fluorescein IV with Wood’s 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 1824 hrs later

Postoperative Care l Primary focus: cardiopulmonary resuscitation, esp in NOMI and recognized mesenteric capillary Postoperative Care l Primary focus: cardiopulmonary resuscitation, esp in NOMI and recognized mesenteric capillary leak syndrome l Aggressive blood and electrolyte rich fluids l l l Correction arrhythmias Vasopressors l l l l May require 10 -20 L crystalloid in first 24 -48 hrs Dopamine 3 -8 mcg/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

Postoperative Care: Anticoagulation l MVT = Anticoagulation mainstay of therapy l l l Heparin Postoperative Care: Anticoagulation l MVT = Anticoagulation mainstay of therapy l l l 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

Prognosis l Overall mortality 60% Prognosis l Overall mortality 60%

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

Results: Long-term l l l Less studied but relatively favorable prognosis 2 year survival Results: Long-term l l l Less studied but relatively favorable prognosis 2 year survival rate: 70% 5 year survival rate: 50% Mortality highest during 1 st yr Recurrent bowel ischemia infrequent aggressive longterm anticoagulation l l l 38% wt loss 19% reduced appetite Bowel resection, 20% short gut syndrome and none required TPN