Surgical questions 2 Flashcards
How do you give a fluid challenge?
500ml IV normal saline over 30 minutes - if worried about cardiac failure, try 250ml.
Monitor HR, BP, urine output and mental state for response and check for pulmonary oedema. If vital signs still abnormal but no pulmonary oedema, repeat fluid challenge.
If still unstable, may need a CVP line and senior help.
What is the minimum obligatory volume of urine produced for a normal patient?
0.5ml/kg/hr. If less urine than this is produced, the patient is oliguric.
What is a standard maintenance fluid replacement regime?
1L normal saline and 2L of 5% dextrose, with 20mM potassium to each 1L bag. Each bag should run over 8 hours, lasting the whole day.
Describe the daily maintenance fluid requirements for a 70 kg man.
Water 1.5ml/kg/hour - roughly 2.5L/day (1.5L/day urine, 200ml/day faeces and 800ml/day insensible losses)
Na 2mmol/L - 140mmol
K 1mmol/L - 70mmol
How do you work out insensible losses?
Insensible losses from the skin and respiratory system roughly 800ml/day.
Increase by 20% for each degree rise in temperature (roughly an extra 500ml)
Burns patients will need extra fluids and this can be calculated using the Parkland formula: Fluids (ml) - 4 x weight (kg) x % surface area burnt
Stoma patients - the only way to calculate how much excess fluid is being lost is by measuring and recording how much fluid a stoma drains
What is a laparostomy and when is it indicated?
Laparostomy = leaving the abdomen open
Indications: if there has been extensive tissue loss such that it is impossible to close the abdomen; abdominal compartment syndrome - when fluid in the peritoneal and retroperitoneal space accumulates>abdominal wall compliance threshold, reducing venous return and eventually causing ischaemia (can occur due to capillary permeability in SIRS in a critically ill patient).
What are the borders of the inguinal canal?
Posterior: transversalis fascia and conjoint tendon
Roof: arching fibres of internal oblique and transversus abdominis
Anterior: skin, superficial fascia, external oblique aponeurosis and the internal oblique for the lateral third
Floor: inguinal ligament
What are the boundaries of the femoral canal?
Anterior: inguinal ligament
Posterior: pectineal ligament and pectineus
Medial: lacunar ligament
Lateral: femoral vein
What are the potential complications of a surgical hernia repair?
General: haemorrhage, infection, thromboembolism, anaesthetic complications, death
Specific: hernia recurrence, ischaemic orchitis/testicular atrophy, bruising of scrotum and penis, cutaneous anaesthesia or hyperaethesia (but note that there is considerable overlap in the cutaneous areas supplied by the iliohypogastric, ilioinguinal and genitofemoral nerves)
What are the boundaries of Hesselbach’s triangle and what is its significance?
Whether an inguinal hernia is direct or indirect is defined according to its relationship with Hesselbach’s triangles. The boundaries are as follows:
- Medially: rectus sheath
- Inferiorly: inguinal ligament
- Superiorly: inferior epigastric artery
An inguinal hernia that arises within Hesselbach’s triangle is direct, whereas indirect hernias arise lateral to the inferior epigastric artery and thus lateral to the triangle.
What are the contents of the inguinal canal?
Think of structures arising in sets of 3.
Three layers of fascia: external spermatic fascia (from external oblique aponeurosis), cremasteric fascia (from internal oblique aponeurosis), internal spermatic fascia (from transversalis fascia).
Three arteries: gonadal, cremasteric, artery of the vas
Three veins: testicular, cremasteric, vein of the vas
Three nerves: ilioinguinal nerve, sympathetic supply from T10 and 11, genital branch of the genitoinguinal nerve
Three other things: vas deferens, lymphatics, patent processus vaginalis (if present)
What must you always do with any patient who is receiving IV fluids of any sort?
If a patient is receiving IV fluids, you must always document fluid input and output and always reassess the patient clinically and biochemically for fluid status and electrolytes.
What is the neuroanatomical basis for the shifting location of the pain in appendicitis?
There are two pain sensation systems in the abdomen - the splanchnic system, which only senses stretch and spasm, and the cerebrospinal pathway. The embryonic gut arises as a midline organ and its splanchnic innervation is bilateral, thus visceral pain is felt in the midline. The splanchnic nerves carrying this information synapse on neurons which also receive inputs from the anterior abdominal wall. The appendix, being an embryological midgut organ, is innervated by the lesser splanchnic nerve (T10 and T11) and thus pain is felt around the umbilicus.
As the inflammation extends to involve the parietal peritoneum, the pain signals are carried in somatic nerves and inflammation can be localised to the actual site of the appendix, usually in the RIF.
Which two incisions are commonly used for appendicectomy?
The classic approach was the gridiron incision, made perpendicular to the imaginary line between the umbilicus and ASIS and centred over McBurney’s point. This is rarely performed now. The Lanz incision is placed slightly lower in the RIF, starting 2cm medial to the ASIS and follows a horizontal course, following a skin crease.
The laparoscopic approach is now becoming more common place.
At the time of the operation, in the presence of a normal appendix, the surgeon also inspects the distal two feet of the terminal ileum. Why?
One of the differential diagnoses of appendicitis is an inflamed Meckel’s diverticulum.
