Hemostatic Agents

Hemostatic agents are critical in surgical procedures to control bleeding and promote wound healing. Various materials are used, each with unique properties and mechanisms of action. Below is a detailed overview of some commonly used hemostatic agents, including Gelfoam, Oxycel, Surgical (Oxycellulose), and Fibrin Glue.

1. Gelfoam

• Composition: Gelfoam is made from gelatin and has a sponge-like structure.

• Mechanism of Action:

  • Gelfoam does not have intrinsic hemostatic properties; its hemostatic effect is primarily due to its large surface area, which comes into contact with blood.
  • When Gelfoam absorbs blood, it swells and exerts pressure on the bleeding site, providing a scaffold for the formation of a fibrin network.

• Application:

  • Gelfoam should be moistened in saline or thrombin solution before application to ensure optimal performance. It is essential to remove all air from the interstices to maximize its effectiveness.

• Absorption: Gelfoam is absorbed by the body through phagocytosis, typically within a few weeks.

2. Oxycel

• Composition: Oxycel is made from oxidized cellulose.

• Mechanism of Action:

  • Upon application, Oxycel releases cellulosic acid, which has a strong affinity for hemoglobin, leading to the formation of an artificial clot.
  • The acid produced during the wetting process can inactivate thrombin and other hemostatic agents, which is why Oxycel should be applied dry.

• Limitations:

  • The acid produced can inhibit epithelialization, making Oxycel unsuitable for use over epithelial surfaces.

3. Surgical (Oxycellulose)

• Composition: Surgical is a glucose polymer-based sterile knitted fabric created through the controlled oxidation of regenerated cellulose.

• Mechanism of Action:

  • The local hemostatic mechanism relies on the binding of hemoglobin to oxycellulose, allowing the dressing to expand into a gelatinous mass. This mass acts as a scaffold for clot formation and stabilization.

• Application:

  • Surgical can be applied dry or soaked in thrombin solution, providing flexibility in its use.

• Absorption: It is removed by liquefaction and phagocytosis over a period of one week to one month. Unlike Oxycel, Surgical does not inhibit epithelialization and can be used over epithelial surfaces.

4. Fibrin Glue

• Composition: Fibrin glue is a biological adhesive that contains thrombin, fibrinogen, factor XIII, and aprotinin.

• Mechanism of Action:

  • Thrombin converts fibrinogen into an unstable fibrin clot, while factor XIII stabilizes the clot. Aprotinin prevents the degradation of the clot.
  • During wound healing, fibroblasts migrate through the fibrin meshwork, forming a more permanent framework composed of collagen fibers.

• Applications:

  • Fibrin glue is used in various surgical procedures to promote hemostasis and facilitate tissue adhesion. It is particularly useful in areas where traditional sutures may be challenging to apply.

Numerical Values to Remember

• Implant torque: 10 – 20 N/cm
• Lateral force test: 5 lb
• Failed implant mobility: >1mm horizontal or <500gm force
• CO₂ laser necrosis zone: ~500 microns (continuous) vs <100 microns (pulsed)
• Scar revision wait: 6 – 12 months minimum
• Scar maturation: 4 – 24 months

Key Diagnostic Tests

• Bowstring test: NOE fractures (medial canthal ligament)
• Torque testing: Implant osseointegration
• Percussion test: Implant stability

Most Common/Frequent

• Most frequent orbital fracture: Floor medial to infraorbital canal
• Most useful implant failure sign: Loss of crestal bone
• Greatest ectropion risk: Subciliary incision
• Most recent laser delivery: Hollow wave guide technology

Treatment Hierarchies

Parotid Duct Injury: Location determines treatment Scar Management: Timing is crucial Laser Parameters: Pulse manipulation reduces tissue damage

Memory Aids:

• RSTA: Reflection, Scatter, Transmission, Absorption (laser interactions)
• 4 P's: Photothermal, Photoablative, Photochemical, Photoacoustic (tissue reactions)
• Implant Forces: "10 – 20 torque, 5 lb lateral, < 500gm = fail"

• Normal clotting time: 8 – 15 minutes.
• Platelet – rich plasma (1 unit): Raises platelet count by 7,000 – 10,000/μL.
• Fresh frozen plasma (150 mL): Contains 200 μ factors VIII & IX, 400 mg fibrinogen.
• Cryoprecipitate: Contains factors VIII, XIII, vWF, fibrinogen.
• DIC marker: Elevated D – dimers.
• Hemophilia factor levels: Majority have < 5%.
• Surgery in hemophilia: Raise factor levels to 50 – 75%.

Characteristics of Middle-Third Facial Fractures

Middle-third facial fractures, often referred to as "midfacial fractures," involve the central portion of the face, including the nasal bones, maxilla, and zygomatic arch. These fractures can result from various types of trauma, such as motor vehicle accidents, falls, or physical assaults. The following points highlight the key features and clinical implications of middle-third facial fractures:

1. Oedema of the Middle Third of the Face

• Rapid Development: Oedema (swelling) in the middle third of the face develops quickly after the injury, leading to a characteristic "balloon" appearance. This swelling is due to the accumulation of fluid in the soft tissues of the face.

• Absence of Deep Cervical Fascia: The unique anatomical structure of the middle third of the face contributes to this swelling. The absence of deep cervical fascia in this region allows for the rapid spread of fluid, resulting in pronounced oedema.

• Clinical Presentation: In the early stages following injury, patients with middle-third fractures often present with similar facial appearances due to the characteristic swelling. This can make diagnosis based solely on visual inspection challenging.

2. Lengthening of the Face

• Displacement of the Middle Third: The downward and backward displacement of the middle third of the facial skeleton can lead to an increase in the overall length of the face. This displacement forces the mandible to open, which can result in a change in occlusion, particularly in the molar region.

• Gagging of Occlusion: The altered position of the mandible can lead to a malocclusion, where the upper and lower teeth do not align properly. This can cause discomfort and difficulty in chewing or speaking.

• Delayed Recognition of Lengthening: The true increase in facial length may not be fully appreciated until the initial oedema subsides. As the swelling decreases, the changes in facial structure become more apparent.

3. Nasal Obstruction

• Blood Clots in the Nares: Following a middle-third fracture, the nares (nostrils) may become obstructed by blood clots, leading to nasal congestion. This can significantly impact the patient's ability to breathe through the nose.

• Mouth Breathing: Due to the obstruction, patients are often forced to breathe through their mouths, which can lead to additional complications, such as dry mouth and increased risk of respiratory infections.

Scar Timeline

• Worst appearance: 2 weeks to 2 months post – suturing
• Complete maturation: 4 – 24 months
• Revision timing: Wait 6 – 12 months minimum

Maturation Assessment Parameters

• Degree of discomfort
• Erythema
• Induration

• Minimum platelet count for surgery: 75,000/cu mm
• Absolute contraindication: Platelets < 50,000/cu mm
• Blood unit volume: 450 mL
• PRBC effect: ↑ Hb by 1 g/dL, ↑ Hct by 3%
• Warfarin patient: Check INR & PT before extraction
• Normal PT: 11–14 seconds