Fluid and Electrolytes: Pre and Post Op Management

Question 1

What are some of the reasons that surgical patients may be in fluid or electrolye deficit?

Answer 1

• Intestinal obstruction
• Fistulae
• Bleeding
• Peritonitis
• Vomiting
• Diarrhoeah

Question 2

What happens in bowel obstruction with regards to volume?

Answer 2

• Isotonic hypovolaemia
• Vomiting -> HCl ion loss -> metabolic alkalosis
• Renal compensation - preserves H+ at the expense of potassium -> hypokalaemia
• End result: hypochloremic, hypokalaemic, metabolic alkalosis

Question 3

Why is fluid and electrolye imbalance important prior to anaesthesia?

Answer 3

• Anaesthetic agents - reduce sympathetic tone/ -ve inotropic effect
• Dehydrated pt - sympathetic nervous system is maximally activated to maintain vital organ perfusion
  
  • If dehydration not corrected -> pt can become hypotensive -> death on anaesthesia
• Anaesthetci agents affect cardiac muscle contraction, hypokalaemia/ hyperkalaemia

Question 4

What are the consequences of starvation prior to surgery?

Answer 4

• Reduce risk of vomiting and regurgitation whilst under general anaesthetic
• Risk of airway obstruction
• Reduced energy - hypoglycaemia, irrtability, headache. dehydration, hypovolaemia
• Blood is not directed to the GI tract

Question 5

Why does surgery lead to DVT and PE?

Answer 5

• Injury and stasis of the blood
• Without proper prophylaxis surgical patients are at risk of developing thrombi in their soleal and gastrocnemius venous sinuses
• These will then travel proximaly -> popliteal and superficial femoral veins

Question 6

When does a classic post op PE develop?

Answer 6

After 10-12 days

Question 7

How can post op DVT’s be prevented?

Answer 7

• Pre operative mobility
• Post operative mobility
• Graduated compression stocking or anti-embolism stockings AES
• Intraoperative intermittent calf compression
• Maintain hydration
• Stop pro thrombotic drugs e.g. COCP - stop 4 weeks before surgery
• Prophylaxis: LMWH Dalteparin 12 hours before surgery

Question 8

What are some of the common early and delayed complication of blood transfusion?

Answer 8

• Early: TRALI, acute haemolytic reactions, fluid over load, anaphylaxis, bacterial contamination
• Delayed: infections (viruses, hep B/C, HIV, bacteria protozoa), iron overload, graft versus host disease, purpura

Question 9

How long should patients by NBM pre operatively?

Answer 9

• Emergency: 6 hr before
• Elective: 6h before for food; 2h for clear fluid

Question 10

How should anti coagulants be stopped pre operatively?

Answer 10

• Stop warfarin 5 days before (target INR range 3.0-4.0).
• Bridge with LMWH (dalteparin) for 2 days after last dose of warfarin
• BD Dalteparin 100units/ kg - give half dose (100 units/kg OD) on day before procedure and ensure at least 24 hour interval between last dose and time of procedure
• Start prophylactic dalteparin 6 hrs post op

Question 11

How should steroid administration be managed for patients on steroid?

Answer 11

GIVE MORE

• Minor surgery: no supplementation needed
• Moderate procedure: 50mg hydrocortisone before induction adn 25mg every 8h for 24h
• Major: 100mg hydrocortisone before and 50mg every 8h for 24h