What Are Surgical Dressings?
A surgical dressing refers to any material — used alone or in combination — applied to cover a wound. The purpose of a dressing is to protect the wound and promote proper healing.
Key functions of surgical dressings:
- Reduce microbial contact and protect against infection
- Provide mechanical support and assist tissue healing
Classification of Surgical Dressings
A. Fibres
- Non-medicated fibres — Absorbent cotton, wool, silk, etc.
- Medicated fibres — Capsicum wool, etc.
B. Fabric
C. Bandages
D. Rubber and Oil Impregnated Materials
Cotton (Absorbent Cotton)
Synonyms: Cotton wool, surgical cotton, purified cotton. Family: Malvaceae Biological Source: Epidermal trichomes (hairs) from the seeds of Gossypium herbaceum and other Gossypium species. Geographical Source: Commercially produced in the USA, Egypt, and India; also cultivated in Africa and South America.
Cultivation and Collection
The plant bears fruits (capsules) after flowering. Each capsule contains numerous seeds covered with hairs called bolls. The bolls are collected, dried, and taken to a ginning press where the trichomes (hairs) are separated from the seeds. The separation yields:
- Short hairs (linters) — used in manufacturing absorbent cotton
- Long hairs — used in cloth preparation
Chemical Constituents
Raw cotton contains about 90% cellulose, 7–8% moisture, wax, fat, and remnants of protoplasm. Purified cotton is entirely cellulose with 6–7% moisture.
Chemical Tests
- Insoluble in dilute NaOH and HCl; soluble in 66% H₂SO₄
- With iodinated ZnCl solution → turns violet
- When 0.1g is heated with 10ml ZnCl solution at 40°C → fibres do not dissolve
Uses
- Used as a filtering medium in surgical dressings
- Absorbs blood, mucus, and pus; protects wounds from microbial infection
- Used as an insulating material
Silk
Synonyms: Fabric, sarsenet, textile. Family: Bombycidae | Order: Lepidoptera Biological Source: Fibres obtained from the cocoons of Bombyx mori and related Bombyx and Antheraea species. Geographical Source: Fine quality silk is manufactured in Japan, Italy, China, and France; also produced in large quantities in India.
Preparation
- The silkworm larva produces silk fibroin fibres from glands in its mouth.
- Fibroin combines with a gum-like secretion called sericin to form a cocoon.
- Cocoons are heated to 60–80°C by steam exposure to prevent further insect development.
- The heated cocoons are placed in hot water to dissolve the gum and separate the fibres.
Chemical Constituents
Silk contains the protein fibroin. On hydrolysis, fibroin yields the amino acids glycine and alanine.
Uses
- Considered the “Queen of Textiles” — soft, smooth, and lustrous
- Used for clothing — shirts, suits, ties, blouses, pyjamas, etc.
Storage
Must be stored in a cool place. Exposure to light causes darkening; bleaching reduces its tensile strength.
Wool
Synonyms: Fleece, coat, woollen hair. Family: Bovidae | Order: Ungulata Biological Source: Fibres obtained from the fleece of sheep Ovis aries. Geographical Source: Australia, Russia, Argentina, USA, and India are major producers.
Preparation
The fleece is removed from the sheep at shearing time, then processed to remove wool fat and dirt. The clean and defatted wool is bleached, washed again, and dried.
Chemical Constituents
Wool contains keratin — a sulphur-containing protein rich in the amino acid cystine.
Chemical Test
Add 0.5g sample in chloroform with 1ml acetic anhydride and 2–3 drops of sulphuric acid → deep green colour indicates the presence of cholesterol.
Uses
- Used as a water-absorbable ointment base and common ingredient in water-soluble creams and cosmetics
- Widely used in winter clothing — sweaters, winter coats, caps, etc.
Regenerated Fibres
Regenerated fibres are made from the cellulosic parts of plants by dissolving them in chemicals. They are partially natural and partially synthetic.
Rayon (Viscose Rayon / Regenerated Cellulose)
Source and Preparation:
- Cellulose from coniferous wood pulp (80–90% cellulose and hemicellulose) is treated with sodium to form sodium cellulosate.
- Further treated with carbon disulphide and sodium hydroxide to produce a viscous solution of sodium cellulose xanthate.
- After ripening, this solution is forced through fine nozzles into a bath of sodium sulphate and sulphuric acid, forming continuous filaments.
- Filaments are drawn together to form yarn, then desulphurised, bleached, washed, twisted, and dried.
Rayon contains about 10% moisture and, unlike cotton, does not lose absorbency on storage.
Uses:
- Making fabrics
- Preparation of surgical dressings
- Production of viscose rayon absorbent wool
Sutures
Sutures are sterile threads, strings, or strands specially prepared for use in surgery to sew tissues together.
Ideal Properties of Sutures
- Must be sterile and cause no irritation
- Intended for single-use only
- If absorbable, the time of absorption must be known
- Must not show any chemical reaction with body chemicals
- Must maintain tensile strength until tissue healing is complete
Classification
Sutures can be made from intestinal tissues, tendons of animals and birds, vegetable fibres, camel hair, human hair, synthetic threads, or metallic wires. They are classified as:
- Absorbable sutures — broken down by body enzymes over time
- Non-absorbable sutures — remain in the body permanently or must be removed
- Haemostatics — used to control bleeding
Surgical Catgut
Catgut is a type of cord prepared from natural fibres of cattle intestine — originally from sheep intestine, and also from goat, horse, and donkey intestines. Catgut sutures treated with chromium salt solutions resist body enzymes and slow down absorption — these are known as chromic catgut sutures. Modern catgut is also prepared from synthetic absorbable polymers such as vicryl and polydioxanone.
Uses:
- Used in surgery for accidental or trauma conditions to block excessive bleeding
- Used in tissue replacement, delivery procedures, cancer surgery, and wound healing
Ligatures
Ligatures are specially prepared and sterilised threads used without a needle to tie blood vessels and other tissues together. Stainless steel ligatures are used specifically for tooth aligning and levelling in orthodontics.
D.Pharma 1st Year — All Subjects Notes
D.Pharma 2nd Year — All Subjects Notes