Hemostasis is the body’s natural process for stopping blood flow, and it must be deliberately managed during surgery to ensure a successful outcome. Surgical hemostasis is the intentional application of various techniques to prevent or halt bleeding from damaged blood vessels. Effective management of blood loss is paramount for maintaining the patient’s physiological stability and providing the surgeon with a clear operative field. This control minimizes the need for blood transfusions, reduces operating time, and significantly lowers the risk of postoperative complications. The methods employed fall broadly into three categories: mechanical, energy-based, and topical agents.
Mechanical Methods of Achieving Hemostasis
Mechanical techniques are the most fundamental and direct means of stopping blood flow, relying on the physical principle of vessel occlusion. For small bleeding sources, direct pressure is applied using a surgical sponge or gauze. This compression temporarily squeezes the vessel walls together, allowing natural clotting factors to form a stable plug at the injury site.
For larger vessels, instruments are used to physically seal the channel. Surgical clamps, often called hemostats, temporarily grasp and crush a bleeding vessel, holding it closed until a more permanent technique can be applied.
Permanent mechanical hemostasis is most commonly achieved through ligation. This involves placing a suture material, or ligature, around the vessel and cinching it down to permanently block the lumen and stop blood flow. The material used is typically absorbable, meaning the body will break it down after the tissue has healed and the vessel is sealed.
An alternative method for permanent closure is the use of surgical clips. These are small, metallic staples applied across the vessel wall using a specialized applier. The clips crush the vessel ends together, forming a tight physical seal that remains in place permanently.
Energy-Based and Thermal Techniques
Energy-based methods use controlled heat to achieve hemostasis by modifying the structure of the tissue, a process known as coagulation. This is accomplished by denaturing the proteins within the vessel walls and surrounding tissue, causing them to shrink, seal, and form a tight barrier.
Electrocautery is the most frequently used thermal method, employing high-frequency electrical current to generate heat at the tissue site. Monopolar electrocautery utilizes a current that flows from the surgical instrument through the patient’s body to a grounding pad. The concentration of energy at the small instrument tip generates intense heat to coagulate the vessel.
Bipolar electrocautery offers a more localized effect because the electrical current flows only between two closely spaced tips of the instrument. This confines the energy to the small piece of tissue grasped between the tips, which minimizes the spread of heat to surrounding structures. This focused application is useful for delicate areas where collateral thermal damage must be avoided.
Ultrasonic Instruments
Specialized ultrasonic instruments achieve coagulation through rapid mechanical vibration rather than electrical current. A Harmonic Scalpel, for example, vibrates its blade at ultrasonic frequencies, creating friction that generates heat to seal vessels up to several millimeters in diameter. The focused heat is sufficient to denature collagen and elastin, effectively sealing the vessel and simultaneously cutting the tissue.
Laser Technology
Laser technology can also be used, where a concentrated beam of light energy is converted to heat upon absorption by the tissue. This causes instantaneous vaporization of water and coagulation of proteins to seal small bleeders.
Topical and Biologic Hemostatic Agents
Topical hemostatic agents are substances applied directly to the bleeding surface, acting as an adjunct to mechanical or thermal methods, particularly for diffuse capillary or venous oozing. These agents either passively provide a matrix for clotting or actively accelerate the natural coagulation cascade. They are useful in areas where suturing or cautery is impractical, such as raw bone surfaces or large areas of soft tissue.
Passive hemostatic agents work by acting as a physical scaffold that concentrates platelets and clotting factors at the site of hemorrhage. Materials like oxidized regenerated cellulose (a gauze-like mesh) or gelatin sponges (which swell upon contact with blood) provide a structural matrix. This enhances the formation of a stable blood clot.
Active hemostatic agents directly participate in the biological process of clot formation by introducing a component of the clotting cascade. The most common active agent is topical thrombin, an enzyme that rapidly converts the circulating protein fibrinogen into fibrin. This conversion is the final step in the body’s natural cascade, leading to the formation of a stable fibrin mesh clot almost immediately upon application.
Fibrin sealants combine both thrombin and concentrated fibrinogen, effectively mimicking the last stage of the coagulation process when applied. The two components are mixed at the site of bleeding, instantly forming a flexible, durable fibrin clot that adheres to the tissue surface. These advanced biologic glues are highly effective for managing persistent oozing and sealing tissue planes.