What are the causes of sudden death in surgery?
Anaesthetic causes Hypoxia:
■ Respiratory obstruction (including kinked or displaced endotracheal tube)
■ Vagal stimulation
■ Disconnection from ventilator
■ Tension pneumothorax secondary to positive-pressure ventilation
■ Mendelson syndrome or chemical pneumonitis (due to hydrochloric acid aspiration during induction)
■ Shock (undetected hypotension secondary to internal bleeding)
■ Embolisation (venous, air, fat).
Medication:
■ Inappropriate drugs administered
■ Anaphylactic reaction (drugs or blood)
■ Overdose of medication (local anaesthetic)
■ Cardiac dysrhythmias (vasodilators, ganglion blocks, diuretics)
■ Electrolyte and metabolic imbalances
■ Opiates.
Surgical causes
■ Hypotension (manipulation of bowel, mesenteric stretching or sympathectomy)
■ Cardiac arrhythmia (induced by catheterisation, cardiac surgery)
■ Oculocardiac reflex (patient in prone position with direct pressure on eyes causing vagal stimulation)
■ Damage to surrounding nerves, arteries and veins (e.g. incision of a groin aneurysm during a hernia repair).
Patient causes
Myocardial infarction, pulmonary oedema, pulmonary embolism, stroke, dehydration, electrolyte imbalances.
Sutures
B&L
For further reading see Bailey and Love, Chapter 18.The examiner may ask you to demonstrate your surgical skills in suturing.
Practise your technique on models and patients prior to the examination.
What is a suture?
A suture is a material used to tie or approximate tissues together. (A suture is also a joint with minimal connective tissue located in the skull vault – e.g. coronal and sagittal sutures.)
Sudden death
What are the types of suture?
Sutures are classified as follows: absorbable versus non-absorbable;
natural versus synthetic; and monofilament versus polyfilament (braided).
Sutures may also be classified by size (5/0, 4/0, 3/0 etc.).
■ Absorbable: PDS (polydioxanone); vicryl (polyglactin); monocryl
■ Non-absorbable: steel; prolene (polypropylene); nylon (ethilon); silk
■ Natural: silk; catgut
■ Synthetic: vicryl; PDS
■ Monofilament: PDS; prolene
■ Polyfilament/braided: vicryl; silk.
How are sutures broken down?
■ Proteolytic digestion (e.g. catgut)
■ Hydrolysis (e.g. vicryl).
What makes a good suture material?
An ideal suture:
■ is all-purpose (can be used for all types of surgery)
■ is easy to handle
■ maintains adequate tensile strength
■ causes minimal tissue reaction
■ holds securely
■ has no memory
■ is resistant to shrinkage
■ is inexpensive
■ is easily sterilised
■ has predictable performance
■ has high breaking strength
■ is inert (electrolytic, capillary, allergenic and non-carcinogenic).
What type of suture is vicryl?
Vicryl (polyglactin) is an absorbable, synthetic, braided polymeric suture.
It produces a minimal tissue reaction. It is fully absorbed after 56–70 days, and provides adequate support for around 30 days.
What type of suture is silk?
Silk is a non-absorbable, natural, braided suture. It is biodegradable. Its tensile strength lasts up to one year. It causes an inflammatory tissue reaction and should be avoided in the placement of vascular prostheses or artifical heart valves.
Needles
B&L
For further reading see Bailey and Love, Chapter 18.What are the parts of a needle?
A needle is compromised of its point, body and swage.
Section 3: Applied surgical science
How are needles classified?
Needles can be classified by shape, type and effect (Fig. 3.3).
Shape
■ Straight
■ Curved: 1/4, 3/8, 1/2 and 5/8 circle
Needles
1/4 circle 3/8 circle 1/2 circle
1/2 curved
Straight
Compound curve J needle
Cutting needles for stitching skin
Needles used for suturing the bowel The threads are swaged into the needles
Needles used for suturing the abdominal wall:
Round-bodied needles for peritoneum, muscles and fat
Cutting needles for aponeurosis 5/8 circle
Cross-section
Figure 3.3 ● Types of needles used for sutures. The sutures are swaged on to prevent a ‘shoulder’ and allow easy passage through tissues. (Bailey and Love, Figure 18.6, p. 241.)
Section 3: Applied surgical science
■ J-shaped
■ Compound curve.
Type
Round-bodied needles:
These are designed to separate (not cut) tissue fibres. They may be used in soft tissues. After the needle is passed, the tissue closes tightly around the suture material to form a leakproof line. Types are:
■ intestinal
■ heavy
■ blunt taper-point
■ blunt point.
Cutting needles:
These are designed for tough or dense tissues. Types are:
■ tapercut
■ conventional cutting
■ reverse cutting.
Effect
■ Traumatic needles are with holes or eyes. They are supplied separate from the suture thread. The suture is threaded on-site. A needle with an eye carries a double strand, which creates a larger hole and disruption to the underlying tissue. These are rarely seen nowadays but are occasionally still used (e.g. aneurysm needle).
■ Atraumatic needles are eyeless and are swaged (pre-mounted) to a suture. This reduces handling and preparation time and causes less trauma to the underlying tissues.
What advantage does a reverse cutting needle have over a cutting needle?
In a reverse cutting needle the cutting edge is situated on the outside of the needle and is therefore less likely to cut through the tissues. In addition, by having the apex cutting edge on the outside of the needle curvature, this improves the strength of the needle and increases its resistance to bending.
How are surgical needles chosen?
Remember the mnemonic PATS:
■ P = procedure
■ A = access
■ T = tissue
■ S = surgeon’s preference.
Nutrition
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For further reading see Bailey and Love, Chapter 17.What is the normal daily resting energy expenditure of a 70 kg man?
He uses 1800 kcal.
What are the daily protein/nitrogen requirements for healthy and critically ill patients?
■ Healthy patient requires 0.15 g/kg of nitrogen
■ Critically ill patient requires 0.3 g/kg of nitrogen.
What routes of nutrition are available, and why are they chosen?
See Fig. 3.4.
■ Enteral nutrition is used in patients with a normally functioning gastrointestinal tract. Feeding routes are oral, nasogastric, nasojejunal, nasoduodenal and tube enterostomy.
■ Parenteral nutrition is the treatment of choice in patients with catabolic states and non-functioning gastrointestinal tracts.
If enteral feeding is preferred, what are the indications for total parenteral nutrition?
■ Patient who cannot ingest food
Nutrition
■ Anorexia:
• neurological disorders
• posterior fossa cranial surgery
• head injury
• coma (reduced GCS)
■ Trauma and tumours (involving the maxilla, head or neck):
• patients with malfunctioning gastrointestinal tract
• short-bowel syndrome secondary to small bowel resection
• fistula (enteroenteric, enterocolic, enterovesical, enterocutaneous)
• obstruction (GI tumours, strictures, adhesions, pyloric obstruction)
• paralytic ileus
• inflammatory disease (Crohn’s disease, ulcerative colitis, pancreatitis diverticular disease, radiation enteritis)
• peptic ulceration
• mesenteric vascular occlusion (ischaemia)
• malignancy
• trauma
■ Hypercatabolic states
■ Major GI anomalies (tracheo-oesphageal fistula, gastroschisis, and intestinal atresia).
What are the major complications of enteral feeding?
Related to intubation of GI tract
■ Fistulation
■ Wound infection
■ Peritonitis
■ Displacement and catheter migration
■ Obstruction of the tube.
Related to delivery of nutrient to GI tract
■ Aspiration or pneumonia
■ Feed intolerance
■ Diarrhoea.
What are the major complications of parenteral feeding?
Related to catheter – mechanical
■ Blockage
■ Migration
■ Fracture
■ Displacement
■ Central vein thrombosis
■ Air embolism
■ Pneumothorax, haemothorax or hydrothorax
■ Subclavian artery and vein injury
■ Cardiac arrhythmias (if catheter is placed in the ventricle).
Section 3: Applied surgical science
Related to catheter – infective
■ Exit site skin infection
■ Line sepsis
■ Infective endocarditis.