Categories of Hemostasis
Hemostasis is achieved through mechanical, thermal, and chemical/topical methods, often used in combination. Understanding which method fits which bleeding scenario is a core CST exam competency.
Mechanical Hemostasis
| Method | Description |
|---|
| Digital/manual pressure | Direct pressure applied with a sponge or fingers; first response to active bleeding |
| Hemostatic clamp + ligature | Vessel clamped, then tied with suture (free tie or clamp-and-tie) |
| Surgical clips (e.g., titanium, polymer) | Applied with a clip applier to occlude small vessels quickly |
| Vessel loops/tourniquets | Temporarily occlude a vessel or limb to control flow during dissection |
| Pledgets and bolsters | Reinforce suture lines under tension to prevent tissue tear-through |
Thermal Hemostasis
| Method | Description |
|---|
| Monopolar electrosurgery | Current flows from an active electrode through the patient to a dispersive (grounding) pad; used for cutting and coagulation |
| Bipolar electrosurgery | Current passes only between the two tips of the forceps; safer near nerves and in patients with implanted devices; no dispersive pad required |
| Ultrasonic energy (e.g., Harmonic scalpel) | High-frequency vibration denatures protein and seals vessels with minimal thermal spread |
| Advanced bipolar vessel sealing (e.g., LigaSure) | Combines pressure and bipolar energy to fuse vessel walls up to 7mm |
| Argon beam coagulator | Argon gas stream conducts monopolar current for broad-surface coagulation (e.g., liver, spleen) |
Chemical and Topical Hemostatic Agents
| Agent | Mechanism | Note |
|---|
| Absorbable gelatin sponge (Gelfoam) | Provides a mechanical matrix for clot formation; absorbs blood and swells |
| Oxidized regenerated cellulose (Surgicel) | Provides a matrix and creates an acidic, bactericidal local environment |
| Microfibrillar collagen (Avitene, Instat) | Attracts platelets, initiating aggregation directly on the collagen matrix |
| Topical thrombin | Converts fibrinogen to fibrin directly at the bleeding site; often combined with gelatin matrix |
| Fibrin sealant (tissue glue) | Combines fibrinogen and thrombin components to form a fibrin clot; also used for tissue adherence |
| Bone wax | Mechanically occludes bleeding from cancellous bone surfaces (not absorbed, not a true hemostatic agent) |
Key Exam Points
- Bipolar electrosurgery does not require a dispersive/grounding pad because the circuit stays local between the forceps tips.
- Bone wax is mechanical, not absorbable - it can impair osteogenesis and is used sparingly.
- Topical hemostatic agents work best on a relatively dry field; heavy active bleeding should be controlled mechanically or thermally first.
- Excess microfibrillar collagen or cellulose left in a closed space can act as a nidus for infection or granuloma formation, so excess material is typically removed before closure.
- Electrosurgical unit (ESU) settings and mode (cut vs. coagulation, monopolar vs. bipolar) are confirmed with the surgeon before use, and smoke evacuation should be used per facility policy.