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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5524_Библиотеки_им_академика_М_И_Перельмана.pdf
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- •Table of Contents
- •Dedication
- •Foreword
- •Contributing Authors
- •Balancing limited resources and care of the individual patient
- •Reducing waste in the ICU
- •Practical Algorithms/Diagram
- •I: Background
- •1. Critical Care Responsibility in Healthcare Reform
- •Take Home Points
- •Background
- •Main Body
- •Review of Current Literature with References
- •2. Initial Approach to the Trauma Patient
- •Take Home Points
- •Background
- •Main Body
- •Review of Current Literature with References
- •3. Systems-based Approach to the Critically Ill Surgical Patient
- •Take Home Points
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •II: System-Based Management
- •4. Central Nervous System
- •Take Home Points
- •Background
- •Main Body
- •Take Home Points
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagram
- •Review of Current Literature with References
- •5. Cardiovascular
- •Take Home Points
- •Background
- •Main Body
- •Cellular metabolism
- •Assessment of cellular metabolism
- •Oxygen delivery
- •Assessment of Oxygen Content
- •Assessment of CO
- •Assessing oxygen balance and cellular metabolism
- •Assessments of VO2
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Recognition of shock
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Resuscitation strategies
- •Resuscitation markers
- •Practical Algorithm(s) /Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Cardiac support
- •Vasoconstrictors
- •Vasodilators and sympathetic antagonists
- •Practical Algorithm(s)/ Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •The conduction system of the heart
- •Cardiac electrophysiology and understanding the electrocardiogram
- •Main Body
- •Arrhythmia in the postoperative period
- •The evaluation of a patient with an arrhythmia
- •Bradyarrhythmias
- •Tachyarrhythmias
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Treatment of acute coronary syndrome
- •Background
- •Main Body
- •Defining the acute coronary syndromes
- •Evaluation of a patient with a suspected acute coronary syndrome
- •Early diagnostic measures
- •Cardiac imaging
- •Definitive therapy for ACS
- •Sequelae of myocardial infarction
- •Post-myocardial infarction hospital care
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •6. Respiratory
- •Take Home Points
- •Background
- •Main Body
- •ICU patient/physiology
- •Airway equipment/management
- •Extubation
- •Practical Algorithm(s)/ Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •I. Common indications for ABG:
- •II. ABG interpretation
- •III. Common causes of acid base disturbances in the ICU
- •IV. Sample ABG analyses
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Initiation of ventilation: modes of ventilation and phase variables
- •Positive-end expiratory pressure
- •Ventilator asynchrony
- •Acute hypoxic events during mechanical ventilation
- •Practical Algorithm(s)/ Diagrams
- •Take Home Points
- •Background
- •Main Body
- •Predicting the need for prolonged mechanical ventilation early
- •Transitioning the work of breathing to the patient
- •Determining successful transitioning
- •The myth of “minimal ventilator settings”
- •Extubation
- •The difficult to wean patient
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Complex pleural effusion/empyema
- •Hemothorax
- •Mediastinitis
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •7. Renal
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s) / Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Definition
- •Causes of oliguria
- •Work-up of oliguria
- •Initial management of oliguria
- •Commonly used medications associated with renal injury (not a comprehensive list)
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Key concepts of RRT
- •Hemodialysis versus hemofiltration: Mechanisms
- •Indications for CRRT and clinical considerations
- •Dosing
- •Practical Algorithm(s) / Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Literature
- •Take Home Points
- •Background
- •Main Body
- •Pathology
- •Diagnosis
- •Treatment
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •8. Gastrointestinal
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •History
- •Controversial issues
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s) / Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s) / Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s) / Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s) / Diagrams
- •Review of Current Literature with References
- •9. Hematology
- •Take Home Points
- •Background
- •Main Body
- •Theoretical basis for pRBCs transfusion
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •10. Infectious Disease
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background
- •Main Body
- •Practical Algorithm(s)/Diagrams
- •Review of Current Literature with References
- •Take Home Points
- •Background

178 J. A. Salotto
vasodilator) as compared to those patients on room air (Am J Physiol Heart
Circ 2005; 288: H1057–1062). A Cochrane review later examined four trials
of 430 patients with confirmed STEMI or NSTEMI. They observed a twofold increase in mortality in those treated with oxygen, but ultimately these
numbers were underpowered. They concluded that evidence in support of
oxygen use in ACS is sparse, and that oxygen should be used with caution
given the trend towards harm (Cochrane Database of Systemic Reviews
2013; Issue 8 Art No: CD007160).
• Rao et al. performed a retrospective review of over 24,000 patients in three
trials of patients with ACS. Cohorts were divided into those who received
blood transfusions or not. The group undergoing transfusion had a significantly higher rate of 30-day death (8% vs. 3%), myocardial infarction (25%
vs. 8%) and death or MI (29% vs. 10%). They calculated a hazard ratio for
30-day death with transfusion at 3.94, and this was statistically significant.
The risk of 30-day death was higher with transfusion hematocrit triggers
above 25%. (JAMA 2004; 292: 1555–1562).

Chapter 5-(viii)
Vascular Emergencies
Charles J. Fox, MD*
*Chief of Vascular Surgery, Denver Health Medical Center
Take Home Points
• Early initiation of damage control resuscitation (blood in 1:1:1 ratios and
limiting crystalloid) is crucial in performing a successful simultaneous vascular reconstruction without ongoing physiologic derangements.
• A vascular assessment should begin in the admitting area using a handheld
continuous wave Doppler device.
• A CT angiogram may be useful for cervical or truncal vascular injuries to plan
the best approach, but rarely necessary for extremity vascular injury.
• Pre-hospital tourniquets should be exchanged for the pneumatic type and
removed in the operating room if the patient is unstable or if hemorrhage is
expected.
• Vascular repairs often require massive transfusion, therefore temporary shunt-
ing with delayed repair should be considered at remote community hospitals
with limited blood banks.
Contact information: Denver Health Medical Center, University of Colorado Health
Sciences Center, 777 Bannock Street, MC 0206, Denver, CO 80204; Tel.: 202-697-1456,
email: Charles.fox@dhha.org
179

180 C. J. Fox
• A second surgical team can save time by placing external fixation, and per-
forming saphenous vein harvests or fasciotomy.
• A vein interposition graft is durable when there is adequate muscle coverage;
otherwise a longer bypass tunneled out of the zone of injury should be chosen
to prevent desiccation or delayed rupture.
• Veins can be ligated but repair time permitting will improve outflow.
• Trust your repair. Remember, a patient in shock may not have a palpable pulse
when leaving the operating room.
Background
• Traumatic vascular emergencies have special importance as injuries to major
vessels offer unique surgical challenges, and comprise the majority of potentially preventable deaths from penetrating injury.
• In the presence of hemorrhagic shock, you will routinely perform vascular
surgery in less than optimal situations.
• These situations demand early deliberate preparation to ensure successful
management of vascular wounds.
• Many lessons learned during U.S. military operations continue to advance
the practice of vascular trauma surgery and now, translates into the current
surgical practices which are recommended.
• Common non-trauma vascular emergencies such as iatrogenic vascular access
complications, vasopressor induced ischemia and acute thromboembolism are
common to the ICU setting.
Main Body
• Assessment of the vascular trauma patient
Vascular trauma usually involves extremities and is often part of the
injury complex in patients with exsanguinating hemorrhage. Optimal
management requires proper planning and recognition of the essential
priorities necessary to prevent immediate hemorrhagic death. Following
immediate airway control, attention is directed at controlling hemorrhage
and obtaining vascular access. External bleeding can often be hidden by
warming blankets or transport gear. You will fi nd that direct pressure is
the most effective way to control hemorrhage. A volume depleted patient
may not always manifest active arterial bleeding at the time of admission.
Pre-hospital tourniquets, if used, should nonetheless be inspected and

Vascular Emergencies 181
readjusted or replaced once the resuscitation restores adequate peripheral
perfusion. Intravenous access may be hindered by shock, and immediate
intraosseous access into the tibia or the humerus is easy and rapid. Initial
laboratory studies will depict the degree of physiologic distress that is
used to guide the resuscitation and early operative planning. Damage
control resuscitation, a strategy of liberal blood product administration,
minimal crystalloid use, should begin early in the emergency room and
continue intra-operatively. The goal is to achieve hemostasis, restore
normal physiology, and potentially complete a vascular reconstruction,
upon arrival in the ICU. If the graft is done correctly, it should not fail
because you withheld heparin or gave hemostatic agents to a coagulopathic patient. Blood products should be transfused within minutes of
arrival with an emergency release of four units of type O packed red
blood cells (PRBCs), and two units of thawed AB plasma sent from
the blood bank. The blood products are best transfused through a rapid
infuser system that is reserved in the admitting area. Unstable patients
with a truncal injury or those with more than one mangled extremity are
considered “in-extremis” and should trigger a massive transfusion protocol. This involves a standardized release and transfusion of PRBCs,
thawed plasma, cryoprecipitate, and platelets.
Recognizing the need for vascular reconstruction at the time of the trauma
admission is crucial for success as indecision and progressive ischemic
burden can result in ultimate graft failure and subsequent limb loss. Most
of the extremity injuries involve fractures and large soft tissue wounds
that can make the diagnosis, by physical exam alone, very accurate.
Radiographs can provide early clues that extremity vascular injuries exist
and you should take a close look at the plain fi lms as you enter the admitting area. For example, supracondylar femur and tibial plateau fractures
are frequently associated with injuries to the distal femoral and popliteal
artery. This is among the most common lower extremity vascular injury
patterns that you will encounter. Deformed extremities are straightened
and the onset of additional hemorrhage is controlled with direct pressure, gauze packing, hemostatic dressings or additional tourniquets.
Alternatively, in stable patients, without active bleeding, pre-hospital
tourniquets should be carefully loosened to determine the degree, if any,
of vascular injury. A Doppler assessment is advised to confi rm the absence
of pedal pulses and to perform an Ankle-Brachial Index when possible.
A patient assessment done in concert with an orthopedic surgeon will facilitate the necessary discussion regarding the sequence of the operation, and

182 C. J. Fox
preferred techniques for external fi xation that best aid in the anticipated
vascular exposure. Important information to relay to the entire operative
team should include ideal patient positioning, the plan for vein harvesting
in a contralateral extremity, and the desire for a C-arm or arteriography.
Special instruments located in “peel packs” can ease the apprehension of
not having the favored instruments when needed quickly. The earlier you
relay this information to the OR, the easier and faster your case will be.
• Tips and strategies for success
For extremity injury, a two-team practice reduces ischemic time as the
primary team may be preoccupied with thoracotomy, or laparotomy to
control hemorrhage, or other damage control maneuvers. Do not hesitate
to involve a second team as they can be used to apply external fi xation,
perform fasciotomies, begin a peripheral vascular exposure, or harvest
vein from a non-injured or amputated extremity. It is important to take
some extra “careful” time when doing the vein harvest. You should always
caution your assistant on the potential for injury to the saphenous vein
when performing a fasciotomy. Position the patient to enable unimpeded
access to another body cavity or limb in the event of unexpected deterioration or need for additional vein harvesting.
Initial control of hemorrhage is often accomplished by digital occlusion
using an assistants hand prepped directly into the bleeding wound bed with
betadine spray. This is followed by a careful dissection proximal and distal
to the site of injury. Balloon catheters may also tamponade hemorrhage
when a tourniquet or manual pressure is not effective. Blind insertion of
surgical instruments can be unproductive, or harmful, and is discouraged.
Tourniquets are left in place until the anesthetist has suffi cient time to
resuscitate the patient. Proximal femoral injuries are best managed by
division of the inguinal ligament or a simple retroperitoneal approach and
clamp control of the external iliac artery. For proximal axillo-subclavian
wounds, sternotomy or left anterior thoracotomy and clamping of the
subclavian artery eliminate the error of uncontrolled dissection through
an expanding hematoma of the chest. You should approach distal axillary
and proximal brachial arterial injuries with infraclavicular incisions, and
extend across the deltopectoral region into the upper arm as needed. The
medial approach is preferred for femoropopliteal injuries. The approach
in relation to the knee joint is directed by the level of the wound, however
total division of muscular attachments at the knee is sometimes required to

Vascular Emergencies 183
control hemorrhage of transected arteries and veins. You may fi nd that the
transected end can be diffi cult to identify in the destroyed tissue. Although
often thrombosed at the time, these vessels must be found and ligated
because they will re-bleed later after the patient is resuscitated. Retrograde
advancement of a Fogarty catheter from an uninjured distal site can also
be used to locate the transected artery in a horrifi c wound that is no longer
bleeding. When making a decision to amputate or salvage an extremity,
you should consider the patients’ condition, extent of injury, and your
willingness to commit the patient to the necessary defi nitive orthopedic
care and physical rehabilitation. No one situation or scoring system can
replace the surgical judgment developed by an experience team.
A primary end-to-end repair is preferred when lateral sutures cannot repair
the injured vessel. Advantages of this repair include a single anastomosis,
and use of autologous tissue. Dividing nearby branches may gain some
length in non-calcifi ed vessels, but this repair should be both expedient
and tensionless. A complete debridement of any disrupted tissue is an
essential step of the repair, and sacrifi ces made to avoid an interposition
conduit should be keenly resisted. The complexity and additional operative time required for vein harvest and interposition grafting or bypass
should be appreciated, and the fi nal operative plan and estimated time
should be communicated early to the entire operative team. The saphenous vein is the preferred conduit for vascular injuries. The poor historical
results of prosthetic material when used in contaminated wounds are the
justifi cation for this approach. In my experience, prosthetic grafts placed
in larger vessels with good muscle coverage have been used successfully.
I have used prosthetic grafts for “clean” subclavian and carotid wounds,
however inferior long term patency of prosthetic materials and the potential
for infection in war wounds have restricted its widespread use in combatrelated extremity wounds.
High energy munitions produce large cavitary wounds, with numerous
disruption of the skin, and loss of underlying muscle that may prevent
attempts to achieve suitable graft coverage. When you are confronted with
this situation, a longer vein graft tunneled completely around the zone
of injury should be chosen over a shorter poorly covered vein interposition conduit. Appropriately applied external fi xation will take this issue into consideration, and this is an important subject to discuss before
fasciotomy incisions are made. Devitalized tissue is excised and irrigated
under low pressure, with careful evaluation of muscle tissue for viability.

184 C. J. Fox
A lengthy and meticulous debridement at the outset is not necessary as
these wounds look much better in a few days after subsequent washouts
and vacuum dressings.
Ballistic trauma can transmit kinetic energy and result in intimal injury
well beyond the transected arterial segment. Therefore, perform your
debridement with a great deal of concentration and focus on the quality of the luminal surface and strength of the arterial infl ow relative to
the patients’ hemodyanamics. When necessary, a Fogarty catheter should
be carefully advanced as pre-hospital tourniquets and incomplete heparin
dosing in trauma may result in thrombus accumulation proximally. A four
quadrant, heel-to-toe anastomosis that is well-spatulated is the easiest repair method to teach and perform in diffi cult situations. Small Heifetz
clips or Bulldog clamps can also minimize the chance of a clamp injury.
Special precautions are worthwhile and should in particular include routine
fl ushing of the graft, and native artery with heparinized saline to dislodge
fi brin strands, and platelet debris.
Upper extremity injuries should not be underestimated, and often require
massive transfusions, from ongoing blood loss and resuscitation requirements. The arm swelling and wound expansion that can result highlights
the importance of a wide tunnel for a saphenous vein graft. There has been
a sustained interest in repair of venous injuries to avoid the potential for
early limb loss from venous hypertension or long term disability from
chronic edema. With combined injuries, arterial repair should precede
venous repair to minimize further ischemic burden, unless the vein repair
requires very little effort.
The temporary use of shunts for vascular trauma is a very effective dam-
age control technique to allow for delayed reconstruction. The value of
temporary shunting should be compared with the consequences of simple
ligation. For example, ligation of the brachial artery after confi rming distal
signals and palmar blood fl ow, allows for elective delayed reconstruction if
indicated. Surgeons at smaller remote facilities may prefer shunting when
rapid evacuation to places capable of matching transfusion requirements
or performing emergent complex vascular repairs is necessary.
While arteriography remains the gold standard for guiding surgical
reconstruction, static fi lm arteriography has largely been replaced with
portable C-arm units capable of digital subtraction angiography. Contrast
arteriography is very useful for locating the injured vascular bed when
there are diffuse fragmentation wounds to the extremity. Hand injected
contrast images using butterfl y needles without special wires or catheters

Vascular Emergencies 185
can be acquired quickly using the digital subtraction mode on a mobile
C-arm unit. Rotating the table before the start of the case may be necessary
to properly maneuver the C-arm. When all else fails, holding the feet off
the end of the table may allow for the acquisition serial images to satisfactorily complete the case. The logistics of maintaining a robust inventory
in a fi eld hospital continues to limit the capability to carry out these interventions in combat. Completion assessments following open repair or
endovascular interventions make use of a combination of physical exam,
the handheld Doppler and selective arteriography.
• Delayed evaluation and postoperative care
The early postoperative period is focused on patient warming, resus-
citation, and hourly vascular checks which should be performed with
a hand-held continuous wave Doppler probe. Palpable pulses and,
sometimes, normal ankle-brachial ratios (>0.9) may be delayed until
an appropriate resuscitation period has occurred. Patients should remain
in the ICU for the at least 24 hours. In addition to ensuring overall cardiopulmonary and metabolic stability, plans for evacuation out of the war
zone should take the threat of early graft failure and post-operative bleeding into consideration. The vascular injured patient should not be hurried
unnecessarily through the chain of evacuation. External fi xators are readjusted based on the appearance of plain fi lm radiographs, and a wound
inspection is normally performed within 24 hours. The typical patient is
returned to the operating room every 48–72 hours for additional washouts, debridement’s, and negative pressure “vacuum” dressing changes.
A careful assessment for the development of a compartment syndrome is
essential, especially when the patient is transferred out of the combat zone
to providers unfamiliar with the initial post-operative exam. You should
always maintain a low threshold for performing a fasciotomy for patients’
with extremity vascular injury.
• Non-trauma emergencies
Pseudoaneurysm: A pseudoaneurysm can develop after a traumatic
arterial injury and, unlike a hematoma, will demonstrate arterial fl ow
through a neck into a false space contained by surrounding tissue. This
occurs frequently following arterial puncture and may be from inadequate
compression. Pseudoaneurysms are characterized by a pulsatile mass,
tenderness and in severe cases, ulceration or necrosis of the overlying skin.
A Duplex ultrasound evaluation can determine the size and location. The

186 C. J. Fox
typical pulsatile echolucent sac will have a swirling “to-and-fro” fl ow
pattern. Compression (10–30 mins) may avoid surgery but is often too
painful and may lead to embolization or thrombosis of the native artery.
Ultrasound-guided thrombin injection (1000 units/mL) is generally considered a fi rst-line therapy for anatomically favorable lesions (saccular,
narrow neck). The tip of a 22 gauge spinal needle is directed away from
the infl ow neck to avoid distal embolization and 0.1–0.2 ml of thrombin
is injected into the sac. An ultrasound performed in 24–48 hrs confi rms
resolution. Direct surgical repair or endovascular interventions continue
to be employed for challenging lesions. Open techniques involve traditional proximal and distal control with suture or patched repair. However,
directly entering the capsule and applying digital pressure is an expeditious approach. In the endovascular era, adjunctive balloon occlusion, coil
embolization, or covered stents may simplify the approach in surgically
inaccessible areas.
Arterial-Venous Fistula: Percutaneous techniques such as central
venous cannulation and arterial catheterization have led to an increased
incidence in arteriovenous fi stulae. When the adjacent artery and vein are
simultaneously punctured, an abnormal connection can form. The local
hemodynamic changes result in elongation and dilation of the proximal
veins and the arterial circulation may be compromised distally by steal.
In larger chronic fi stulas, the systemic circulation may also be affected.
A thrill may be palpated over the affected site or a bruit appreciated on
auscultation. The natural history is thought to be one of gradual enlargement or thrombosis. Symptomatic patients require repair by open or endovascular techniques to restore normal perfusion and venous drainage by
closing the communication. Extensive collateral circulation and friability
of the artery can make the operation technically diffi cult when delayed.
Therefore, most surgeons prefer to treat these cases when diagnosed. Open
repairs involve either isolation of all four limbs, and quadruple ligation or
ablation of the communication channel and restoration of fl ow by suture
repair, patch, or interposition grafting of the two vessels. Transcatheter
embolization and covered stent grafts have gained popularity particularly
in surgically inaccessible areas. Endovascular interventions are particularly less morbid but the materials are expensive. Long-term follow-up is
required to evaluate stent patency and monitor for stent migration.
Percutaneous Closure Devices: Closure devices have permitted earlier
ambulation and discharge following diagnostic and therapeutic catheterizations. The incidence of complications ranges from 0.5–5% depending

Vascular Emergencies 187
on the sheath size, use of anticoagulation, and indications. Closure devices
can actively or passively close the puncture site by using suture-mediated,
collagen-based, or metal clip/disk-based mechanisms of action. The typical
complication is device malfunction resulting in bleeding and necessitating
manual compression or surgical exploration. Compression site thrombosis
or vessel occlusion from the device itself may cause lower limb ischemia.
It is necessary to have documentation of the baseline exam. Usually upon
exploration, suture-mediated devices disrupts the back wall and dissects the
artery or in the case of collagen devices, the material inadvertently advances
into the lumen of the artery. Treatment options include exploration, surgical
thrombectomy and primary repair.
Vasopressor Induced Ischemia: Vasopressor agents such as norepi-
nephrine, dopamine, vasopressin, and epinephrine are often used to treat
shock. Intricate mechanisms exist that modulate vasomotor tone by these
vasoactive substances. The vasomotor response of vascular smooth muscle depends on whether an intact endoluminal endothelial layer is present or absent. When present, the endothelium responds to blood-borne
substances that infl uence smooth muscle contractility. Paracrine mediators
such as nitric oxide modulate the response. When endothelium is absent
as in advanced peripheral arterial disease, the direct effect by vasoactive substances on vascular smooth muscle is often unopposed vasoconstriction. The consequences on digital blood fl ow can be signifi cant and
result in gangrenous changes. Ischemic areas should be protected from
additional mechanical injury which is expected given the likelihood of
impaired sensation in the affected parts. Increasing ambient temperature
and rewarming of any tissue not deemed to be irreversibly ischemic will
improve tissue perfusion and prevent further tissue loss. Antimicrobial
ointments such as silver sulfadiazine should be applied to blistered and
de-epithelialized areas. Similar to a frostbite injury, the ischemic areas
should be allowed to demarcate for auto-amputation in very severe cases.
Acute Limb Ischemia: Arterial embolus produces acute limb ischemia
characterized by pulselessness, pallor, paralysis, pain and parasthesias. In
comparison, thrombotic events are more gradual and associated with atherosclerotic disease. Most embolic events are cardiac in origin or derived
from the atheroemboli of peripheral aneurysms. The specifi c level of the
arterial occlusion directs the preference for catheter-directed thrombolysis (distal small vessels) or opens surgical embolectomy (larger proximal
vessels). Therapeutic unfractionated intravenous heparin should be started
as soon as the diagnosis is suspected. The standard approach is a wide
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