hemostasis

Dr.Niti SarawgiII MDS

HAEMOSTASIS

Contents• Introduction• Events in haemostasis• Intrinsic pathway & extrinsic pathway• Mechanical haemostasis• Chemical haemostasis• Thermal haemostasis• Conclusion

INTRODUCTION

Hemostasis is the process of forming clots in the walls of damaged blood vessels and preventing blood loss while maintaining blood in the fluid state within the vascular system.

EVENTS IN HAEMOSTASIS

Haemostasis means prevention of ‘Blood Loss’. Haemostasis is achieved by several mechanism:-

Vascular constrictionFormation of platelet plugFormation of blood clotGrowth of fibrous tissue into the clot.

VASCULAR CONSTRICTION

The contraction results from:- Local myogenic spasms Local autacoid factors Nervous reflexes

Platelets release, thromboxane-A2 which is responsible for vasoconstriction of smaller vessels.

The more severely a vessel is traumatized, the greater the degree of vascular spasm.

MechanismVasoconstriction is as a result of increased Ca ion conc. in smooth muscles.Hormonal components :Circulating epinephrine & activation of sympathetic nervous system.Interact with cell surface adrenergic receptorsSignal transduction Increased intercellular Ca from sarcoplasmic reticulum Ca-calmodulin complex Activates myosin light- chain kinase stimulate cross bridge cycle

• Factors :• -Exogenous – temperature (cold)• -Endogenous-Autonomic nervous system,

hormones and mechanisms inherent to vasculature (myogenic response)

-Medications: antihistamines , amphetamines , cocaine

FORMATION OF PLATELET PLUG

PHYSICAL AND CHEMICAL CHARACTERISTICS OF PLATELETS

MECHANISM OF PLATELET PLUG• Platelet adhesion• Platelet activation • Platelet aggregation• Formation of temporary haemostatic plug

NORMAL ARCHITECTURE OF A BLOOD VESSEL

PLATELETS Platelets are enucleate

cells 1-4 micro meters in size Normal blood

concentration of platelets is 1.5L-3L/micro liters

Formed in bone marrow from megakaryocytes

T-1/2 is 8-12 days Eliminated from the

circulation by tissue macrophages.

CONTD…Platelet cytoplasm contains active factors

such as:-

Actin and myosin molecules Thrombosthenin is another contractile protein which

can cause platelets to contract. ER and the Golgi apparatus Mitochindria and enzyme system.

PLATELET-CELL MEMBRANE

Surface coat of glycoproteins a) repulse adherence to normal endothelium b) but adherence to injured vessel wall i.e.,

endothelial cells, and even more to the exposed collagen from deep with in the vessel wall

Large amounts of phospholipids – activates multiple stages in blood-clotting process.

PLATELET ADHESON

PLATELET ACTIVATION

PLATELET AGGREGATION

• The activated sticky platelets stick to each other form Platelet aggregation

• TXA2 powerful vasoconsrictor &mobilisation Ca from dense tubular system –activates myosin -actin cause release reaction –Platelet aggregation

• This involves a series of self sustaining events • Leads to formation of platelet plug

MECHANISM OF PLATELET PLUG Platelet repair of vascular openings is based on

several important functions of the platelet itself Contractile proteins adhere to collagen & vWF

Secrete ADP and their enzymes form thromboxane-A2 ADP + thromboxane-A2 activates adjacent platelets Initial Platelet Plug

BLOOD COAGULATION IN RUPTURED VESSEL

Third mechanism for hemostasis is formation of blood clot

Clot begins to develop- severe trauma-15 to 20 sec minor trauma-1 to 2 min

MECHANISM OF BLOOD COAGULATION

BASIC THEORY

GENERAL MECHANISM

GENERAL MECHANISM

In response to rupture of the vessel or damage to the blood itself-formation of prothrombin activator

Prothrombin activator catalyzes conversion of prothrombin to thrombin

Thrombin catalyzes fibrinogen into fibrin fibers.

CONVERSION OF PROTHROMBIN TO THROMBIN

Contd… Then Fibrin Stabilizing Factor is released from platelets

entrapped in the clot Same thrombin that causes fibrin formation activates

the Fibrin Stabilizing Factor, before FSF can have effect on fibrin fibers

Activated FSF forms strong covalent bond b/w monomer of the fibrin and multiple cross linkage b/w adjacent fibrin fibers.

BLOOD CLOT

The clot is a meshwork Fibrin fibers also adhere to damaged surfaces of

blood vessels.

CLOT RETRACTION-SERUM

Contraction causes expression of fluid from clot-serum Platelet contractile proteins contributes greatly to the

clot retraction by activating Platelet Thrombosthenin

They also helps compress fibrin mesh work into smaller mass.

As the clot contracts, the edges are further pulled together, contributing ultimate state of Hemostasis.

VISCIOUS CIRCLE OF CLOT FORMATION

Positive feed back for clot formation Most important cause of this is the the proteolytic

action of thrombin For instance, thrombin has a direct proteolytic

effect on prothrombin itself, hence more of thrombin formation

Critical amount of thrombin causes more blood clotting and hence further more production of thrombin and hence called a vicious circle of clotting.

INITIATION OF COAGUALTIONFORMATION OF PROTHROMBIN ACTIVATOR

These mechanisms are set into play by:- Trauma to the vascular wall and the adjacent tissues Contact of the blood with damaged endothelial cells

Prothrombin activator is generally considered to be formed in these ways-

a) Extrinsic pathway for initiating blood clotting

b) Intrinsic pathway for initiating blood clotting

CLOTTING FACTORS• Factor I (fibrinogen)- Fibrinogen is a soluble plasma protein (MW

330000) which is acted upon by thrombin to form insoluble fibrin clot.

• Factor II (prothrombin)- Inactive precursor of thrombin is formed in liver. • Factor III (tissue factor, tissue extract,

thromboplastin)- This converts prothrombin in the presence of

factors V, VII, and Xa, Calcium, and phospholipid.

CONTD.

. Factor IV (calcium)- Factor V (labile factor, thrombogene or

proaccelerin)- This factor is reqd. for the conversion of prothrombin

to thrombin by tissue extract and plasma factors. Factor VII (stable factor, autoprothrombin I)- Factor VII is reqd. for the formation of prothrombin

activator by tissue extract. Factor VIII (antihemophilic globulin [AHG],

antihemophilic factor)- Factor VIII is reqd. for the formation of prothrombin activator from blood constituents; it’s consumed during clotting and hence absent from serum. In vivo the half life of factor VIII is 10-20h.

Factor IX (Christmas factor, plasma thromboplastin component, autoprothrombin II)-

It’s needed for the formation of prothrombin activator from blood constituents..

Factor X (stuart-prower factor)-

Converted to factor Xa either by factors IXa & VIII or factor VII & tissue factor. Factor X can be activated by other proteases such as trypsin or Russel’s viper venom.

Factor XI (plasma thromboplastin acntecedent-PTA)-

Also a beta2 globulin present both in serum & alumina treated plasma. It’s thermolabile. Unlike factor XII, its activity increases when stored frozen.

CONTD..

Factor XII ( Hageman factor or contact factor)- It takes part in the formation of prothrombin activator

from blood constituents. It’s present in both serum & plasma.

Factor XIII (fibrin stabilizing factor)- This is plasma protein which causes polymerization of

soluble fibrin to produce insoluble fibrin. Fletcher factor- Described by Hathway (1965). Deficiency resembles

factor XII deficiency. It’s a prekallikerin. Evidence indicating that prekallikerin is activated by limited proteolysis.

Fitzgerald factor- Its heat stable. This appears to act after the activation

of Hageman factor & Fletcher factor but before the activation of factor XI. It’s necessary for conversion of factor XI by Kaolin activated factor XII. It’s reqd. for normal fibrinolysis & kinin formation.

CONTD..

EXTRINSIC PATHWAY FOR INITIATING BLOOD CLOTTING

INTRINSIC PATHWAY FOR INITIATING BLOOD CLOTTING

INTRINSICPATHWAY

COMMON PATHWAY

ROLE OF CALCIUM IONS IN BOTH

PATHWAYS

• Except for first two steps in the intrinsic pathway Ca2+

ions are required for the promotion/acceleration of all the blood-clotting reactions

• In the living body Ca2+ ion concentration seldom falls low enough to significantly affect the kinetics

INTERACTIONS B/W THE EXTRINSIC & INTRINSIC PATHWAYS-SUMMARY

OF INITIATION

LYSIS OF BLOOD CLOTS• Plasminogen or profibrinolysin when activated

forms plasmin (fibrinolysin)• Plasmin is a proteolytic enzyme that digests fibrin

fibers and protein coagulants such as fibrinogen, Factor V, Factor VIII, prothrombin & Factor XII.

Streptokinase is an exogenous activator derived from beta-haemolytic streptococci

FIBRINOLYTIC SYSTEM

ACTIVATION OF PLASMINOGEN TO FORM PLASMIN: THEN LYSIS OF CLOT

Injured tissues and vascular endothelium gradually, after the clot has stopped the bleeding, release powerful activator, t-PA (tissue plasminogen activator)

t-PA converts plasminogen to plasmin, which in turn removes the remaining unnecessary blood clot.

Infact, many small blood vessels in which blood flow has been blocked are reopened by this mechanism.

Methods of haemostasis

Mechanical

Chemical

Thermal

Mechanical haemostasis

Direct pressure

Gauze pack

Suture and ligation

Staples

Direct pressure

• First choice to control bleeding• Fast and simplest• Small Arterial bleeding • Venous bleeding• 15-20 sec• Not recommended in major artery and veins.

Fabric pads/gauze/spong

e• Used with direct pressure• It is used in - only pressure is not an option -systemic bleeding due to infection,

trauma, massive blood loss, and platelet dysfunction.

Suture/staples/ligating clips

• Suture – used in major arteries and veins• Ligation of facial artery, lingual artery, and

external carotid artery

Stick Tie Ligation

Types of Ligation• Stick Tie: • Also called as transfixation.Used for High Blood pressureProximal part of the vessels• Regular Tie Used for Distal part of the vessels Also used for tubectomy .

Regular Tie

• Staples- sterile and disposable titanium staples

• Ligating clips- quick and easy decrease foreign body reaction various size

Use of Hemostats• Hemostats (Mosquito and Artery) are designed to

catch bleeders.• Can be straight or curved.• Various sizes –Micro mosquito,Hartman artery,

Halstead mosquito, Crile ,Crile Ranklin, Kelly Ranklin,Long , Loop or sponge locking

Bone wax• Is a mixture of Beeswax (70%) and Vaseline (30%).• It is a non-absorbable material , becoming soft and

malleable in the hand when warmed• Its Hemostatic effect is based on physical rather than

biochemical properties.• It has been used in bone surgeries• COMPLICATIONS:ALLERGIC, GRANULOMA, INFECTION,

INTERFERES WITH BONE HEALING

Trans Catheter arterial embolization

-Restricts tumors blood supply .-Arterial embolization preferentially interrupts tumors blood supply and stalls growth until neovascularization- Used to control bleeding in Hemangiomas

Thermal Energy Method

• Heat (Cautery)• Electro cautery: it is the use of high frequency

alternating current for cutting, coagulating, dessication or fulgurating tissue in both open and laparoscopic procedure

monopolar electro surgery bipolar electro surgery bipolar electrosurgery vessel sealing technology argon enhanced coagulation technology• Ultrasonic device• Lasers

Monopolar electro surgery

• Most frequently used• Two electodes- active (the pencil) - dispersive• Modes - coagulation mode - cutting mode - blend mode• Current flows through the patient from electrode

(active) to electrode (dispersive)

Bipolar electro surgery

• Current does not flow through the patient’s body• Lower voltage • Indicated in limited thermal spread• Delicate tissue, small anatomical tissue• Safe for implanted medical devices such as

pacemaker, internal cardioconverter fibrillator etc.

Bipolar electrosurgery

sealing technology• Advances electrosurgery modality in which the

intimal layers of the vessel are fused and permanent seal is formed.

• Heat with compression• Capable of simultaneously sealing and

transecting vessel upto 7mm in diameter, large tissue pedicle and vascular bundles

Argon enhanced coagulation technology

• Used a stream of inert non combustible argon gas.

• Argon gas makes more conductive in electrosurgery

• Acts as a bridges between patientt and electrode• In this monopolar current is transmitted to a

tissue through the flow of argon gas .The tip of the coagulator is held 1 cm from the tissue . A flow of argon gas clears the surgical site of fluids to allow current to be focused directly on the tissue .

Ultrasonic device• Converts electrical energy into mechanical

energy• Oscillate longitudinally at the point of contact,

vibrating at 55,500/sec.• Simultaneously cuts and coagulates• Seal vessel upto 5 mm diameter• Limits thermal damage to surrounding tissue• No current through the body

• Laser : Light amplification by stimulated emission of radiations.

• results in bloodless surgery. As they coagulate the small blood vessel during cutting of tissues.

• Cryosurgery :- Extreme cooling has been used for hemostasis .temperature ranging from -20 to -180 are used. Tissue capillaries ,small arterioles undergo cryogenic necrosis . This is caused by dehydration and denaturation of lipid molecules

Chemical methods• Pharmacological agents• Topical haemostatic agent Passive active

Pharmacological agents

• Sterile haemocoagulase solution• Epinephrine• Vitamin k• Protamine• Desmopressin• Lysin analogs• Etamsylate

Sterile haemocoagulase • Eg. Botro clot, Reptilase inj.• Contents –• Haemocoagulaes- isolated from bothrox atrox• Chlorhexidine solution• Water• Topical application of 5-10 drops , 1ml IM

Styptics• Monsels solution – ferric subsulphate :Acts by precipitating protein.Used for capillary bleeding and post-extraction bleeding• Tannic acid :Acts by precipitating proteinsHome remedy for an emergency• Mann Hemostatic – tannic acid , alum and

chlorobutanol• Others:-Silver nitrate-Ferric chloride

Epinephrine• Causes direct vasoconstriction• Can be applied topically and can be injected

with LA • Prolong analgesic effect• Reduces bleeding during surgery• Topical - The drug is applied with the help of

gauze pack in concentration of 1:1000 over a oozing

• It is also injected along with local anesthetics in concentration of 1:80,000 and 1:2,00,000.

Vitamin K• Plays important role in coagulation process• Helps in production of fibrinogen and

prothrombin in liver• Route- orally and IV(slow)• IM and subcutaneous is not recommended

because irratic absorption• Dose- Males: 120 mcg/day PO• Females: 90 mcg/day PO•  5-10 mg IV (dilute in 50 mL IV fluid and infuse

over 20 min

Protamine• Reverse heparin anticoagulation activity• Adverse effect- anaphylaxis, acute pulmonary

vasoconstriction, right ventricular failure• Contraindication -diabetic -pt undergone vasectomy -drug allergy -previous protamine exposure• Dose -1.0 -to- 1.5 mg protamine sulfate IV for every

100 IU of active heparin

Desmopressin• Synthetic vasopressin analogues• Stimulates the release of von willibrand factor

and factor Viii from the endothelial cells.• Enhances primary haemostasis• Slow iv infusion• Dose- 0.3 µg/kg diluted in 50ml saline and infused

i.v over 30 min.• Reduces perioperative bleeding

Lysine Analogues• Eg. Epsilon Aminocaproic acid, tranexamic acid• Inhibits the activation of plasminogen• Reduces the conversion of plasminogen into

plasmin• Dose iv- Epsilon aminocaproic acid- 1-

15gm(loading dose) followed by maintenance dose of 1-2gm hourly

• Total dose of 10-30gm• Oral- 500mg ,• Inj – 5g/20 ml

• Tranexamic acid- loading dose 2-7gm• Follwed by 20-250 mg hourly• Total dose of 3-10gm• Oral dose; 500 mg 6-8 hrly• Children; 1.25g/5 ml of syrup• Inj- 0.5-1g slow i.v infusion TID

Ethamsylate• Reduces capillary bleeding• Increase the ability of platelets to stick together• Dose; 250-500 mg 8 hourly• Contraindication- hypersensitivity and blood

porphyria.

Adenochrome Monosemicarbazone

-Doubtful efficacy1mg/ml inj is given as 2ml/6 hourly before surgery-Acts by correcting abnormal platelet adhesion Contraindications-Allergy to ingredients -Pregnancy & Lactation

Topical Haemostatic Agents

• Passive- collagen based product - oxidised regenerated cellulose - gelatine

• Active haemostat - thrombin product - pooled human plasma thrombin - recombinant thrombin

Collagen base products

• Derived from bovine tendon or bovine dermal collagen

• Further divides into – microfibrillar collagen haemostat eg. Avitene, ultrafoam, Instat. Absorable collagen haemstat sponge eg. Helistat

Oxidised regenerated

cellulose• Eg. Surgicel, surgicel NU KIT• Absorbable white knitted fabric sheet with high or

low density.• It should be use dry.

Gelatins• Eg. Gelfoam , gelfoam plus, surgiform• Absorbable porcine gelatin haemostatic agent• Sponge or powder• Frequently used with saline with thrombin or

epinephrine

Polysaccharides hemospheres

• Eg. Arista, hemostase, vitasure• Topical hemostatic agent derived from vegetables

starch• Should not be used in closed spaces

Bovine thrombine• Powder in vial form• Spray kit or gelatin sponge• Eg. Thrombin JMI

Pooled human thrombin

• Frozen liquid in vial form • Applied via saturated kneaded absorable gelatin

sponge • Eg. evithrom

Recombinant thrombin

• Lyophilized powder in vial form• Used with sterile saline• Should be used within 24hr after reconstitution• Applied with pump or spray or via saturated

kneaded absorbable gelatin sponge• Eg recothrom

Flowable haemostat agent

• Combination of active and passive• Blocking the blood flow as well as converting

fibrinogen into fibrin at the site of bleeding• Combination of• buvine gelatine and pooled human thrombin• Absorbable porcine gelatin + either of the 3

thrombin types

SealantFibrin sealantPolyethylene glycol polymersAlbumin and glutaraldehydecyanoacrylates

Fibrin Sealant• Concentrated fibrinogen and thrombin• Three types• Pooled human plasma• Individual human plasma with bovine and bovine

thrombine• Pooled human plasma and equine sealant

Polyethylene glycol polymers

• Three types• Coseal- PEG polymer• Duraseal- PEG with trilysine amine and blue dye• Progel- PEG human serumm albumin

Albumin glutaraldehyde

• Eg bioglue• 10% glutaraldehayde Crossed linked 45%

bovine serum albumin sealant

Cyanoacrylate• 2-Octyl and Butyle lactoyl cyanoacrylate• Mainly used on the skin• Suture less closure of the wound

Conclusion

References

• Human Physiology, vol.1; Dr. C.C.Chaterjee.• Review of Medical Physiology; W.F.Ganong• Essentials of Medical Physiology – A. Sembulingum• Physiological Basis of Medical Practice; John B. West.• Haematology; Martin R. Howard, Peter J. Hamilton.• Internet sources