KEY NOTES CHAPTER 1: GENERAL PRINCIPLES (H) Wound dressings, sutures, local anaesthesia

Question 1

How are local anaesthetics classified?

Answer 1

Amino-esters - metabolised by pseudocholinesterase to PABA (para-aminobenzoic acid) - e.g. Procaine, cocaine Amino-amides - metabolised by liver - e.g. Lidocaine, bupivicaine, prilocaine

Question 2

What is LA toxicity?

Answer 2

Local hypersensitivity (not toxicity) - erythema, urticaria, oedema, dermatitis CNS Prodromal - light-headed, dizzy - metallic taste - circumoral numbness - tinnitus Severe - grand mal seizures - unconsciousness CVS - hypotension - tachy or bradyarrythmias - VF- CV collapse Idiosyncratic - pseudocholinesterase deficiency, PABA hypersensitivity (esters) - liver disease

Question 3

What are the symptoms and signs of lignocaine toxicity?

Answer 3

Levels (mg/ml) 3-6: subjective (circumoral numbness, tinnitus, drowsiness, lightheadedness, difficulty focusing) 5-9: objective (tremors, twitching, shivering 8-12: seizures, cardiac depression 12-14: unconscious, coma 20: respiratory arrest 25: cardiac arrest

Question 4

How do you treat LA toxicity?

Answer 4

Stop administering LA! CNS Airway, oxygen (hyperventilate - toxicity exacerbated by hypercarbia) IV diazepam, thiopental CVS Fluids Treat arrhythmias as per ALS protocols Anaphylaxis Airway, oxygen Diphenhydramine IV fluids Vasopressors Bronchodilators

Question 5

How do you treat a patient with lignocaine toxicity?

Answer 5

ALS Stabilise potential life threats - impending airway compromise - significant hypotension - treat dysrhythmias - treat seizures (benzodiazepines, barbiturates) Antidote: Intralipid 20% 1.5ml/kg bolus, then ivi 0.25ml/kg

Question 6

What are the goals of GA?

Answer 6

Analgesia Amnesia Preservation of vital functions Muscle relaxation and suppression of undesirable reflexes Quiet, relaxed field for surgeons

Question 7

What types of GAs are used for balanced analgesia?

Answer 7

Nitrous oxide Halogenated agents - halothane, enflurane, isoflurane

Question 8

What is the ASA grading?

Answer 8

I Healthy individual no systemic disease II One-system, well controlled diseaseIII Multisystem or well-controlled major system disease IV Severe, incapacitating, poorly controlled or end-stage disease V Imminent danger or death with or without op ‘e’ emergency op qualifier

Question 9

What is an ideal dressing?

Answer 9

• Physical protection - Non-irritant - Remove necrotic material - Promote epithelialisation - Promote granulation- Be cheap and readily available

Question 10

How do you classify dressings?

Answer 10

Passive vs. interactive vs occlusive Alginates, Films, Foams, Hydrocolloids, Hydrogels, Hydrofibre.

Question 11

What low adherent dressings do you know?

Answer 11

Low adherent - Melolin → gauze with polyethylene backing - Inadine → rayon mesh with povidone-iodine impregnation - Jelonet → paraffin gauze - Bactigras → Paraffin gauze impregrated with chlorhexidine - Mepitel → silicone

Question 12

What semipermeable film dressings do you know?

Answer 12

Permeable to gas and vapours but not to liquids and bacteria - Opsite and Tegaderm → films with adhesive

Question 13

What are hydrogels and hydrocolloids?

Answer 13

Hydrogels e.g. intrasite - Starch-polymer matrix which swells to absorb moisture - Promote autolysis of necrotic material and are used to debride wounds Hydrocolloids e.g. Granuflex and Duoderm - Hydrocolloid matrix backed with adhesive - protects the wound, absorbs fluid and maintains moist environment

Question 14

What are alginates?

Answer 14

• derived from seaweed, - contain calcium,- activates the clotting cascade,- very absorbent, - gelatinous when wet.e.g. Sorbisan and Kaltostat

Question 15

What synthetic foams are used?

Answer 15

• Usually used in concave wounds, conform to the cavity, obiterating dead space - Suitable for heavy exudate - Lyofoam, Mepilex

Question 16

What is topical negative pressure therapy?

Answer 16

Application of suction aids wound healing. Mechanism unclear o Direct suction pulls the wound inwards o ↑ rate of angiogenesis and granulation o ↓ conc of tissue metalloproteinases o ↓ bacterial contamination o ↓ interstitial fluid Nonadherent sponge → semipermeable film → intermittent or continuous suction - Acute wounds 125mmHg - Chronic wounds 50-75mmHg Contraindicated - active bleeding, cancer

Question 17

How do you classify suture materials?

Answer 17

• Absorbable or non-absorbable - Synthetic or natural - Braided or monofilament

Question 18

What types of sutures do you know?

Answer 18

Polyglycolic acid o Dexon → synthetic suture of polyglycolic acid, degraded by hydrolyzation o Loses strength 21 days and absorbed 90 days Polyglactin 910 o Vicryl → loses strength by 21 days absorbed by 90 days o May provoke significant inflam reaction so avoid on face Poliglecaprone 25 o Monocryl → monofilament synthetic, similar absorption to vicryl Polydioxanone o PDS → monofilament synthetic → Loses strength by 3 months and absorbed by 6 months.