ANAESTHESIA ANAESTHESIA AND AND

ANTICOAGULANTANTICOAGULANTSS

Done by: Done by:

Dr. Ahmad AlrefaieDr. Ahmad Alrefaie

HemostasisHemostasis Prevention of blood loss whenever a Prevention of blood loss whenever a

vessel is severed or ruptured.vessel is severed or ruptured. It is a combination of events that occur It is a combination of events that occur

due to physical and chemical forces. due to physical and chemical forces. Achieved by several mechanisms:Achieved by several mechanisms:1.1. Vascular spasm.Vascular spasm.2.2. Formation of platelet plug.Formation of platelet plug.3.3. Formation of blood clot as a result of Formation of blood clot as a result of

coagulation.coagulation.4.4. Growth of fibrous tissue.Growth of fibrous tissue.

The ultimate step in clot formation is The ultimate step in clot formation is conversion of conversion of FIBRINOGEN FIBRINOGEN , a soluble , a soluble plasma protein into plasma protein into FIBRIN FIBRIN , an , an insoluble thread like molecule.insoluble thread like molecule.

The conversion is catalyzed by the The conversion is catalyzed by the enzyme enzyme THROMBENTHROMBEN at the site of at the site of injury.injury.

Thrombin exist in the plasma in the Thrombin exist in the plasma in the form of an inactive precursor called form of an inactive precursor called PROTHROMBINPROTHROMBIN. .

Prothrombin convert’s into thrombin Prothrombin convert’s into thrombin by by FACTOR XFACTOR X, a plasma clotting , a plasma clotting factor.factor.

Factor X present in the blood in Factor X present in the blood in inactive form and must be converted inactive form and must be converted into it’s active form by another into it’s active form by another activated factor, and so on.activated factor, and so on.

AnticoagulantsAnticoagulants

Why we use Why we use anticoagulants?anticoagulants?1.1. Prophylaxis and treatment for deep Prophylaxis and treatment for deep

venous thrombosis (DVT) and venous thrombosis (DVT) and pulmonary embolism which are pulmonary embolism which are commonly associated with surgical commonly associated with surgical procedures.procedures.

2.2. Mechanical heart valves.Mechanical heart valves.

3.3. Cardiac arrhythmias. Cardiac arrhythmias.

Who are patient at risk for Who are patient at risk for DVT?DVT?1.1. Major lower limb or pelvic surgery.Major lower limb or pelvic surgery.2.2. Trauma patient.Trauma patient.3.3. Malignancy ( increase the risk 7-fold).Malignancy ( increase the risk 7-fold). Central neuraxial block significantly Central neuraxial block significantly

reduces the incidence of DVT after reduces the incidence of DVT after orthopaedic surgery but additional orthopaedic surgery but additional prophylaxis is necessary to reduce prophylaxis is necessary to reduce the rate to acceptable levels. the rate to acceptable levels.

AspirinAspirin

Also called acytelsalicylic acid.Also called acytelsalicylic acid. Impair platelet function by inhibiting Impair platelet function by inhibiting

platelet cyclo-oxygenase (COX).platelet cyclo-oxygenase (COX). Aspirin inhibits COX irreversibly, Aspirin inhibits COX irreversibly,

Therefore the antiplatelet effect of Therefore the antiplatelet effect of aspirin persists until a new platelet aspirin persists until a new platelet population is manufactured (at least population is manufactured (at least 7 days). 7 days).

IndicationsIndications

Local analgesic effect.Local analgesic effect. Antipyretic.Antipyretic. Anti-inflammatory.Anti-inflammatory. Antiplatelet.Antiplatelet.

COX 1COX 1

Continuously stimulated by the body.Continuously stimulated by the body. Its concentration in the body remain Its concentration in the body remain

stable.stable. Creates prostaglandins used for basic Creates prostaglandins used for basic

house keeping throughout body.house keeping throughout body. Prostaglandins stimulate normal body Prostaglandins stimulate normal body

functions such as stomach mucous functions such as stomach mucous production, regulation of gastric acid production, regulation of gastric acid and kidney water excretion.and kidney water excretion.

COX 2COX 2

Induced ( normally not present in cells).Induced ( normally not present in cells). Built only in special cells (A549 lung Built only in special cells (A549 lung

cells).cells). Used for signaling pain and Used for signaling pain and

inflammation.inflammation. Produces prostaglandins for Produces prostaglandins for

inflammatory response.inflammatory response. Stimulated only as part of immune Stimulated only as part of immune

response.response.

It is safe to proceed with central and It is safe to proceed with central and periphral nerve block in patients periphral nerve block in patients taking Aspirin. taking Aspirin.

NSAIDsNSAIDs

Analgesic, antipyretic and, in higher doses, Analgesic, antipyretic and, in higher doses, anti-inflammatory drugs.anti-inflammatory drugs.

Impair platelet function by inhibiting Impair platelet function by inhibiting platelet platelet cyclo-oxygenase (COX).cyclo-oxygenase (COX).

NSAIDs inhibit COX reversibly.NSAIDs inhibit COX reversibly. Platelet function returns to normal within 3 Platelet function returns to normal within 3

days after stopping NSAIDs.days after stopping NSAIDs. It is safe to proceed with central and It is safe to proceed with central and

periphral nerve block in patients taking periphral nerve block in patients taking NSAIDs.NSAIDs.

COX 2 inhibitorsCOX 2 inhibitors

Anti-inflammatory drugs that Anti-inflammatory drugs that selectively inhibit selectively inhibit COX 2COX 2..

They do not affect platelet function.They do not affect platelet function. It is safe to proceed with central and It is safe to proceed with central and

periphral nerve block in patients periphral nerve block in patients taking COX 2 alone.taking COX 2 alone.

They can potentiate the effect of They can potentiate the effect of warfarin by increasing the warfarin by increasing the prothrombin time ( PT ). prothrombin time ( PT ).

ClopidogrelClopidogrel

A thienopyridine derivative.A thienopyridine derivative. It is a potent antiplatelet agent.It is a potent antiplatelet agent. It inhibits It inhibits ADP-induced platelet ADP-induced platelet

aggregation and binding between aggregation and binding between platelets and fibrinogen.platelets and fibrinogen.

The effect is irreversible and platelet The effect is irreversible and platelet function does not return to normal function does not return to normal until at least 7 days after stopping the until at least 7 days after stopping the drug. drug.

It is used in combination with aspirin It is used in combination with aspirin in patients with acute coronary in patients with acute coronary syndrome.syndrome.

It should be discontinued 7 days It should be discontinued 7 days before surgery, central neuraxial and before surgery, central neuraxial and peripheral block.peripheral block.

If an antiplatelet effect must be If an antiplatelet effect must be maintained, aspirin can be substituted maintained, aspirin can be substituted safely. safely.

Unfractionated heparinUnfractionated heparin

Indications:Indications:

1.1. Thromboprophylaxis.Thromboprophylaxis.

2.2. Therapeutic anticoagulation.Therapeutic anticoagulation. Subcutaneous thromboprophylactic Subcutaneous thromboprophylactic

doses are seldom associated with doses are seldom associated with bleeding complications.bleeding complications.

Central and periphral block in Central and periphral block in thromboprophylaxis dose: the dose should thromboprophylaxis dose: the dose should be stoped 4 hours before or more than one be stoped 4 hours before or more than one hour after the procedures.hour after the procedures.

Catheter should be removed 2-4 hours Catheter should be removed 2-4 hours after the last dose.after the last dose.

In therapeutic dose: activated partial In therapeutic dose: activated partial thromboplastin time (APTT) should be thromboplastin time (APTT) should be normal before attempting a block or normal before attempting a block or removing a catheter. removing a catheter.

Patients who have been receiving Patients who have been receiving unfractionated heparin for more than unfractionated heparin for more than 4 days should have a platelet count, 4 days should have a platelet count, because the incidence of heparin-because the incidence of heparin-induced thrombocytopenia is about induced thrombocytopenia is about 3%.3%.

LMWHsLMWHs

Indications:Indications:

1.1. Thromboprophylaxis.Thromboprophylaxis.

2.2. Therapeutic anticoagulation.Therapeutic anticoagulation. Have longer half-lives than unfractionated Have longer half-lives than unfractionated

heparin, which allows once daily heparin, which allows once daily administration.administration.

They have They have anti-Xa activityanti-Xa activity.. There is no monitoring test for routine use. There is no monitoring test for routine use.

Central and periphral block in Central and periphral block in thromboprophylaxis dose: the dose should thromboprophylaxis dose: the dose should be stoped 12 hours before the block or be stoped 12 hours before the block or catheter removal.catheter removal.

The first dose is given within 6 hours of The first dose is given within 6 hours of surgery or 2 hours after the block.surgery or 2 hours after the block.

In therapeutic dose: it takes about 24 In therapeutic dose: it takes about 24 hours for coagulation to return to normal. hours for coagulation to return to normal. Therefore, an interval of 24 hours should Therefore, an interval of 24 hours should elapse before attempting block. elapse before attempting block.

FondaparinuxFondaparinux

Indications:Indications: for thromboprophylaxis. for thromboprophylaxis. It is a synthetic pentasaccharide, which It is a synthetic pentasaccharide, which

has potent has potent anti-Xa activityanti-Xa activity.. It has a longer elimination half-life than It has a longer elimination half-life than

LMWH ( 17 hours in young patients and 21 LMWH ( 17 hours in young patients and 21 hours in healthy elderly patients ).hours in healthy elderly patients ).

It is administered 6 hours after surgery.It is administered 6 hours after surgery. An interval of at least 24 hours should An interval of at least 24 hours should

elapse before removal of neuraxial or elapse before removal of neuraxial or peripheral nerve catheters. peripheral nerve catheters.

WarfarinWarfarin Indications:Indications:1.1. Thromboprophylaxis in AF.Thromboprophylaxis in AF.2.2. Post prosthetic heart valve replacement.Post prosthetic heart valve replacement.3.3. Treatment of DVT or PE.Treatment of DVT or PE. Central and periphral block: INR ≤ 1.5, this Central and periphral block: INR ≤ 1.5, this

normally takes about 4 days after stoping normally takes about 4 days after stoping warfarin.warfarin.

If a LMWH or unfractionated heparin has been If a LMWH or unfractionated heparin has been administered in place of warfarin, the administered in place of warfarin, the recommended intervals discussed above should recommended intervals discussed above should be observed before performing any block. be observed before performing any block.

Anticoagulants Anticoagulants perioperativelyperioperatively Warfarin should be stopped 2-4 days Warfarin should be stopped 2-4 days

preoperatively, and the PT time preoperatively, and the PT time monitored daily (INR ≤ 1.5).monitored daily (INR ≤ 1.5).

If INR prolonged:If INR prolonged:1.1. Administer vitamin K.Administer vitamin K.2.2. Fresh frozen plasma.Fresh frozen plasma. It is often appropriate to start an It is often appropriate to start an

alternative anticoagulant, such as LMWH alternative anticoagulant, such as LMWH or unfractionated heparin, until warfarin or unfractionated heparin, until warfarin is re-established and the INR is back in is re-established and the INR is back in the therapeutic range postoperatively.the therapeutic range postoperatively.

After minor surgery: warfarin may be After minor surgery: warfarin may be restarted on the first postoperative day.restarted on the first postoperative day.

After major surgery: an infusion of After major surgery: an infusion of unfractionated heparin may be used to unfractionated heparin may be used to maintain anticoagulation ( with control maintain anticoagulation ( with control by APTT ) until warfarin therapy is by APTT ) until warfarin therapy is restarted.restarted.

Unfractionated heparin is reversed Unfractionated heparin is reversed rapidly with protamine 1 mg for every rapidly with protamine 1 mg for every 100 units of heparin.100 units of heparin.

Unfractionated heparin is preferable Unfractionated heparin is preferable to LMWH because it may be to LMWH because it may be monitored more easily and reversal monitored more easily and reversal titrated more accurately.titrated more accurately.

SummarySummary

Aspirin and NSAIDs:Aspirin and NSAIDs: No No contraindication.contraindication.

Clopidogrel:Clopidogrel: Stop 7 days before Stop 7 days before surgery, central and peripheral block.surgery, central and peripheral block.

Warfarin:Warfarin: INR ≤ 1.5. INR ≤ 1.5. After minor surgery: start on the first After minor surgery: start on the first postoperative day. postoperative day. After major surgery: an infusion of After major surgery: an infusion of unfractionated heparin may be used to unfractionated heparin may be used to maintain anticoagulation. maintain anticoagulation.

Unfractionated heparin:Unfractionated heparin:1.1. Thromboprophylaxis dose: stop 4 Thromboprophylaxis dose: stop 4

hours before or > than one hour hours before or > than one hour after the procedures. after the procedures. Catheter should be removed 2-4 Catheter should be removed 2-4 hours after the last dose.hours after the last dose.

2.2. Therapeutic dose: (APTT) should be Therapeutic dose: (APTT) should be normal before attempting a block or normal before attempting a block or removing a catheter. removing a catheter.

LMWH:LMWH:

1.1. Thromboprophylaxis dose: the dose Thromboprophylaxis dose: the dose should be stoped 12 hours before the should be stoped 12 hours before the block or catheter removal. block or catheter removal. The first dose is The first dose is given within 6 hours of surgery or 2 given within 6 hours of surgery or 2 hours after the block.hours after the block.

2.2. Therapeutic dose: the dose should be Therapeutic dose: the dose should be stoped 24 hours before the block.stoped 24 hours before the block.

Fondaparinux:Fondaparinux: Start 6 hours after surgery. Start 6 hours after surgery. Stop 24 hours before removal of neuraxial Stop 24 hours before removal of neuraxial or peripheral nerve catheters. or peripheral nerve catheters.

REFERENCE:REFERENCE:1.1. AnaesthesiaUKAnaesthesiaUK2.2. Europian Journal of Anaesthesiology2007Europian Journal of Anaesthesiology20073.3. Medical Physiology, GuytonMedical Physiology, Guyton4.4. Fundamentals of PhysiologyFundamentals of Physiology5.5. Text book of Anaesthesia, AitkenheadText book of Anaesthesia, Aitkenhead

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