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BusySpR MRCOG PART I - CLINICAL MX & DATA
MRCOG Part 1 , MRCOG I

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Forum >> MRCOG Part I single best answers: Peri-operative care
MRCOG Part I single best answers: Peri-operative care Posted by PAUL A.
Sun Jul 1, 2012 01:58 am

There are over 1,000 single best answer questions on the main website. In this forum, we will post the new questions we are writing to give you easy access to all of them and get discussion going.

1) Which one is most likely to cause hyperchloraemic acidosis when used for resuscitation or fluid replacement? 

 

A) Ringer’s lactate solution

B) Hartman’s solution

C) Normal (0.9%) saline  

D) 5% dextrose

E) Dextrose/saline 4%/0.18%

 

2) Which one of the above should not be used for resuscitation or fluid replacement in otherwise healthy women

 

A) Ringer’s lactate solution

B) Hartman’s solution

C) 4% gelatin

D) 6% hydroxyethyl starch (HES)

E) Dextrose/saline 4%/0.18%  

 

 

3) The recommended daily adult requirement for sodium is

 

A) 1-2 mmol

B) 10-20 mmol

C) 50-100 mmol  

D) 100-150 mmol

E) 180- 300 mmol

 

4) The recommended daily adult requirement for potassium is

A) 1-2 mmol

B) 4-8 mmol

C) 10-30 mmol

D) 40-80 mmol  

E) 100-120 mmol

 

5) The daily volume of water needed by adults is

A) 0.5-1 L

B) 1.0-1.5 L

C) 1.5-2.5 L  

D) 2.5-3.5 L

E) 3.5-5.0 L 

 

 

6) The recommended daily adult requirement for sodium is

 

A) 1-2 mmol

B) 10-20 mmol

C) 50-100 mmol  

D) 100-150 mmol

E) 180- 300 mmol

 

7) The recommended daily adult requirement for potassium is

 

A) 1-2 mmol

B) 4-8 mmol

C) 10-30 mmol

D) 40-80 mmol  

E) 100-120 mmol

 

8) The daily volume of water needed by adults is

 

A) 0.5-1 L

B) 1.0-1.5 L

C) 1.5-2.5 L  

D) 2.5-3.5 L

E) 3.5-5.0 L 

 

 

9) A 67 year old woman is due to have TAH + BSO for endometrial cancer. She has no significant past medical or surgical history. Oral intake of clear non-particulate fluids should be discontinued

 

A) At least 12h before induction of anaesthesia

B) At least 6h before induction of anaesthesia

C) At least 4h before induction of anaesthesia

D) No more than 4h before induction of anaesthesia

E) No more than 2h before induction of anaesthesia  

 

 

10) A 67 year old woman is due to have TAH + BSO for endometrial cancer. The administration of carbohydrate-rich beverages 2-3 hours before induction of anaesthesia is associated with

 

A) Higher risk of vomiting during induction of anaesthesia

B) Higher risk of aspiration pneumonitis

C) An increase in post-operative insulin resistance

D) A reduction in post-operative nausea and vomiting  

E) Increased risk of bowel injury during the operation

 

 

11) A 70 year old woman is due to undergo laparotomy TAH + BSO + omentectomy for ovarian cancer. Mechanical bowel preparation has been prescribed. During bowel preparation

 

A) The woman should be nil by mouth

B) Oral fluids should be recommended to prevent dehydration

C) 5% dextrose iv should be administered

D) Normal (0.9%) saline iv should be administered

E) Hartman’s solution iv should be administered  

 

 

12) A 63 year old woman has developed ileus following TAH + BSO for endometrial cancer. Intravenous fluid replacement should be by administration of

 

A) 5% dextrose

B) 5% dextrose alternating with normal (0.9%) saline

C) Normal (0.9%) saline

D) Ringer’s lactate solution  

E) 4% gelatin

 

13) A 37 year old woman is experiencing heavy vaginal bleeding following a spontaneous second trimester miscarriage. Administration of which intravenous fluid is most likely to lead to a hyperoncotic state?

 

 

A) Normal (0.9%) saline

B) 5% dextrose

C) 4% gelatin  

D) Hartman’s solution

E) Ringer’s lactate solution

 

 

14) Which one is not a contributor to post-operative oliguria?

 

A) Peri-operative fluid restriction

B) Increased ADH secretion

C) Inactivation of the Renin-angiotensin-aldosterone system  

D) Increased circulating catecholamines

E) Intra-operative blood loss

 

 

 

 

15) Following major abdominal surgery

A) Secretion of anti-diuretic hormone is reduced

B) The capacity of the kidneys to dilute urine is enhanced

C) The capacity of the kidneys to concentrate urine is enhanced

D) Infusion of large volumes of normal (0.9%) saline may cause hyponatraemia  

E) Dextrose/saline 4%/0.18% is the ideal fluid for intravenous fluid replacement

 

17) In the post-operative patient, hyperchloraemia caused by infusion of normal (0.9%) saline is associated with

 

A) Renal vasoconstriction  

B) Increased GFR

C) Increased renal sodium excretion

D) Increased renal water excretion

E) Metabolic alkalosis

 

18) In a malnourished surgical patient

 

A) Urea production is decreased

B) The capacity of the kidneys to concentrate urine is increased

C) Urea excretion by the kidneys competes with sodium excretion  

D) The risk if interstitial oedema is decreased

E) Intra-cellular potassium concentration is increased

 

 

19) In the malnourished surgical patient

 

A) There is intracellular sequestration of sodium  

B) The activity of the Na+K+ ATPase pump is enhanced

C) The intracellular concentration of potassium is increased

D) There is decreased potassium excretion by the kidneys

E) Inactivation of the renin-angiotensin-aldosterone system decreases renal potassium excretion

 

 

20) In malnourished surgical patients receiving oral nutritional supplementation, the feeds

 

A) Should be potassium-poor

B) Should be phosphate poor

C) Should be supplemented with thiamine  

D) Should be supplemented with sodium

E) Should have a high water content

 

 

21) Re-feeding a malnourished surgical patient is associated with

A) Cellular uptake of potassium  

B) Cellular uptake of sodium

C) Efflux of phosphate from cells into extra-cellular fluid

D) Inactivation of membrane Na+K+ ATPase pump

 

22) According to NICE, nutritional support should be considered in

 

A) Patients with a BMI over 35 kg/m2

B) Patients with unintentional weight loss over 10% in the last 3-6 months  

C) Patients with a BMI over 35 kg/m2 and unintentional weight loss over 5%

D) Patients with intentional weight loss over 15%

E) Patients who are not expected to eat for the next 3 days or longer

 

 

23) Oliguria is defined as

A) Urine output of < 30 ml/h

B) Urine output of < 100 ml over 4h

C) Urine output < 0.1 ml/kg/h

D) Urine output < 0.5 ml/kg/h  

E) Urine output < 1.0 ml/kg/h

 

 

24) Post-operative hyponatraemia

A) Is more common in male than in female patients

B) Is more likely to cause brain damage in pre-menopausal than post-menopausal women  

C) Will not result in brain damage until sodium concentrations are below 120 mmol/L

D) Is less likely to occur if the patient is taking thiazide diuretics pre-operatively

E) Will not occur is normal (0.9%) saline is the only iv fluid administered

 

 

25) Post-operative hyponatraemia is characterized by

A) Decreased urine osmolarity

B) Raised serum urea concentration

C) Impaired adrenal cortical function

D) Normal plasma osmolarity

E) Improvement of hyponatraemia with fluid restriction  

 

 

26) Which one is not an early symptom of post-operative hyponatraemia?

A) Muscle weakness

B) Nausea

C) Confusion  

D) Headache

E) Vomiting

 

 

29-31) You have been asked to review a 68 year old woman who is complaining of worsening headache, weakness and vomiting 48h after abdominal hysterectomy. Investigations have shown Hb = 10.2g/dl, WCC = 13.2, platelets = 235. Na = 125, K = 3.7, Urea = 5.2, Creatinine = 65. She has received 2 L normal (0.9%) saline and 1 L 5% dextrose every 24h.

 

29) The most likely underlying cause of her symptoms is:

 

A) Ileus

B) Bowel obstruction

C) Renal failure

D) Hyponatraemia  

E) Hypokalaemia

 

 

30) Which one of these is unlikely to be a contributory factor to this woman’s underlying disorder?

 

A) Impaired adrenal cortical activity  

B) Pre-operative fluid restriction

C) Surgical stress

D) Infusion of 5% dextrose

E) Infusion of normal (0.9%) saline

 

31) Which one is the most appropriate treatment option?

 

A) Anti-emetics and analgesia

B) Naso-gastric tube

C) Fluid restriction  

D) Infusion of 3 L normal (0.9%) saline per 24h

E) Infusion of 2x normal (1.8%) saline

 

 

Answers Posted by Farrukh G.
Sat Jul 7, 2012 03:50 pm

 

*1) C

  • The normal sodium intake in adults is 50-100 mmol/24 hours, which should be accompanied by about 1.5 to 2.5 L (25 to 35 mL/kg/24h) of water
  • Chloride ions cause renal vasoconstriction and reduce glomerular filtration rate resulting in sodium retention
  • Because of the risk of inducing hyperchloraemic acidosis when crystalloid resuscitation or replacement is indicated, balanced salt solutions e.g. Ringer’s lactate/acetate or Hartmann’s solution should be used instead of 0.9% saline, except in cases of hypochloraemia e.g. from vomiting or gastric drainage.

 

*2) E

  • Solutions such as 4%/0.18% dextrose/saline and 5% dextrose are important sources of free water for maintenance, but should be used with caution as excessive amounts may cause dangerous hyponatraemia, especially in children and the elderly. These solutions are not appropriate for resuscitation or replacement therapy except in conditions of significant free water deficit e.g. diabetes insipidus.

*3) C

*4) D

*5) C

  • To meet maintenance requirements, adult patients should receive sodium 50-100 mmol/day, potassium 40-80 mmol/day in 1.5-2.5 litres of water by the oral, enteral or parenteral route. Additional amounts should only be given to correct deficit or continuing losses.

*6) = 3) = C

 

*7) = 4) = D

 

*8) = 5) = C

 

Apologies these questions were repeated

 

Type

Na (mM)

K (mM)

Cl (mM)

Osmolarity

(mosmol/L)

Plasma vol expansion duration (h)

Plasma

136-145

3.5-5.0

98-105

280-300

--

5% dextrose

0

0

0

278

--

Dextrose saline 0.18%

30

0

30

283

--

Normal saline 0.9%

154

0

154

308

0.2

Ringer’s lactate

130

4

109

273

0.2

Hartman’s

131

5

111

275

0.2

Gelatin 4%

145

0

145

290

1-2

5% albumin

150

0

150

300

2-4

HES 6% 130/0.4

154

0

154

308

4-8

 

Composition of commonly used intravenous solutions. HES (hydroxyethyl starch)

 

 

*9) E

*10) D

 

In patients without disorders of gastric emptying undergoing elective surgery clear non-particulate oral fluids should not be withheld for more than two hours prior to the induction of anaesthesia.

 

In the absence of disorders of gastric emptying or diabetes, preoperative administration of carbohydrate rich beverages 2-3 h before induction of anaesthesia may improve patient well being and facilitate recovery from surgery. It should be considered in the routine preoperative preparation for elective surgery.

 

Preoperative oral administration of solutions of carbohydrate oligomers has been shown in several trials to attenuate preoperative thirst, anxiety and postoperative nausea and vomiting. It also substantially reduces postoperative insulin resistance, thereby improving the efficacy of postoperative nutritional support.

 

*11) E

*12) D

  • Routine use of preoperative mechanical bowel preparation is not beneficial and may complicate intra and postoperative management of fluid and electrolyte balance. Its use should therefore be avoided whenever possible.

 

  • Where mechanical bowel preparation is used, fluid and electrolyte derangements commonly occur and should be corrected by simultaneous intravenous fluid therapy with Hartmann’s or Ringer-Lactate/acetate type solutions.

 

  • Excessive losses from gastric aspiration/vomiting should be treated preoperatively with an appropriate crystalloid solution which includes an appropriate potassium supplement. Hypochloraemia is an indication for the use of 0.9% saline, with sufficient additions of potassium and care not to produce sodium overload.

 

Losses from diarrhoea/ileostomy/small bowel fistula/ileus/obstruction should be replaced volume for volume with Hartmann’s or Ringer-Lactate/acetate type solutions. 

 

*13) C

 

Hypovolaemia due predominantly to blood loss should be treated with either a balanced crystalloid solution or a suitable colloid until packed red cells are available.

Hypovolaemia due to severe inflammation such as infection, peritonitis, pancreatitis or burns should be treated with either a suitable colloid or a balanced crystalloid.

The administration of large volumes of colloid without sufficient free water (e.g. 5% dextrose) may precipitate a hyperoncotic state.

 

*14) C

*15) D

Post-operative handling of sodium & water load

 

For the surgical patient it is even more difficult to excrete a salt and water load and to maintain normal serum osmolarity for several reasons.

 

  • The stress response to surgery causes anti-diuresis and oliguria mediated by ADH, catecholamines and the Renin-Angiotensin-Aldosterone System (RAAS).

 

Following surgery, even when the serum osmolarity is reduced by administration of hypotonic fluid, the ability to excrete free water is limited because the capacity of the kidney to dilute, as well as to concentrate urine, is impaired. Excess free water infusion risks dilutional hyponatraemia.

 

*17) A

If saline is infused, chloride overload accompanies sodium overload, and hyperchloraemia causes renal vasoconstriction and reduced GFR, further compromising the ability of the kidney to excrete sodium and water.

 

*18) C

*19) A

  • In more seriously ill surgical catabolic patients with increased urea production, there is a reduced ability to concentrate urine. As a consequence it requires two or more times the normal volume of urine to excrete a sodium and chloride load given in the perioperative period. Sodium and chloride excretion competes with excretion of nitrogen mobilised by the inflammatory response to surgery. A large proportion of the administered sodium, chloride and water is therefore retained as interstitial oedema.
  • Potassium depletion, due both to RAAS activity and the cellular loss of potassium which accompanies protein catabolism, reduces the ability to excrete a sodium load.
  • A sustained increase in systemic capillary permeability allows albumin and its attendant fluid (18 ml for every gram of albumin) to leak into the interstitial space, thereby worsening interstitial oedema. This exacerbates intravascular hypovolaemia and sodium and water retention by activation of the RAAS and secretion of ADH.
  • Intracellular sequestration of sodium and fluid due to lack of intracellular energy and failure of the cellular Na/K ATPase pump may occur in trauma, shock and fasting/malnutrition. In severe cases this gives rise to the so-called sick cell syndrome

 

*20) C

Nutritional status

 

  • Nutritionally depleted patients need cautious refeeding orally, enterally or parenterally, with feeds supplemented in potassium, phosphate and thiamine. Generally, and particularly if oedema is present, these feeds should be reduced in water and sodium. Though refeeding syndrome is a risk, improved nutrition will help to restore normal partitioning of sodium, potassium and water between intra- and extra-cellular spaces.

Surgical patients should be nutritionally screened, and NICE guidelines for perioperative nutritional support adhered to. Care should be taken to mitigate risks of the refeeding syndrome.

 

*21) A

 

Nutritionally depleted patients need cautious re-feeding orally, enterally or parenterally, with feeds supplemented in potassium, phosphate and thiamine. Generally, and particularly if oedema is present, these feeds should be reduced in water and sodium. Though re-feeding syndrome is a risk, improved nutrition will help to restore normal partitioning of sodium, potassium and water between intra- and extra-cellular spaces.

 

Surgical patients should be nutritionally screened, and NICE guidelines for perioperative nutritional support adhered to. Care should be taken to mitigate risks of the re-feeding syndrome.

 

Potassium is the dominant intracellular and sodium the dominant extracellular cation, but because in severe illness or malnutrition there is impairment of the Na/K ATPase pump, sodium tends to move into the cells and K out, a process which is related to surgical mortality. Conversely, re-feeding the depleted patient is associated with rapid cellular uptake of potassium and phosphate and exhaustion of limited thiamine stores leading to the re-feeding syndrome unless appropriate supplements of potassium, phosphate and thiamine are given. NICE criteria for identifying patients at risk of re-feeding syndrome.

 

*22) B

 

NICE criteria for nutritional support.

 

  • Nutritional support should be by the safest, simplest, most cost effective approach acceptable to the patient.
  • Favour oral over enteral and enteral over parenteral feeding.
  • Nutrition support should be considered in people who are malnourished, as defined by any of the following:
  • A BMI of less than 18.5kg/m2
  • Unintentional weight loss greater than 10% within the last 3-6 months
  • A BMI of less than 20kg/m and unintentional weight loss greater than 5% within the last 3-6 months.

 

  • Nutrition support should be considered in people at risk of malnutrition as defined by any of the following

 

  1. Have eaten little or nothing for more than 5 days and/or are likely to eat little or nothing for the next 5 days or longer
  2. Have a poor absorptive capacity, and/or have high nutrient losses and/or increased nutritional needs from causes such as catabolism.

 

*23) D

 

Defined as urine output < 0.5ml/kg/h

 

 

*24) B

 

Post-operative hyponatraemia

 

  • Up to 20% of women who develop symptomatic hyponatraemia die or suffer serious brain damage
  • Caused by surgical stress resulting in a syndrome of inappropriate antidiuretic hormone secretion and promoting water retention for several days
  • Women are more affected than men, as a result of their smaller fluid volume and other sex related hormonal factors
  • Premenopausal women are prone to brain damage at sodium concentrations below 128 mmol/l
  • Postmenopausal women do not usually become symptomatic until sodium concentrations have fallen below 120 mmol/l but may be symptomatic at higher levels if the rate of change is rapid
  • Ageing impairs fluid homoeostasis and increases the risk of severe hyponatraemia. This is compounded by chronic diseases and long-term use of drugs such as thiazide diuretics.
  • The risk of hyponatraemia is further increased by routine infusions of isotonic dextrose. Post-operative patients metabolise glucose almost immediately.
  • Isotonic dextrose infusions are effectively just water and volumes as low as 3-4 L over two days may cause convulsions, respiratory arrest, permanent brain damage, and death in healthy women

However, post-operative hyponatreamia also occurs even after infusion of near-isotonic solutions only (sodium chloride, 154 mmol/L, or Ringer lactate [sodium, 130 mmol/L, and potassium, 4 mmol/L])

 

*25) E

 

Typical features of post-operative hyponatreamia include

 

  • Hyponatraemia and low plasma osmolarity
  • Persistent excretion of hypertonic urine
  • Otherwise normal renal function (normal urea and creatinine)
  • Normal adrenal function
  • No evidence of extracellular fluid volume contraction (dehydration / hypotension)

Improvement of hyponatreamia following fluid restriction

 

*26) C

 

Post-op hyponatraemia

 

Early symptoms include:

  • Weakness
  • Nausea
  • Vomiting
  • Headache

 

Late symptoms include

  • Confusion and restlessness
  • Convulsions
  • Drowsiness
  • Eventually, coma and respiratory arrest

 

Typically, patients have an initial uncomplicated post-operative recovery followed by symptoms of hyponatraemic encephalopathy

 

*27) D

 

Typical features of post-operative hyponatreamia include

 

  • Hyponatraemia and low plasma osmolarity
  • Persistent excretion of hypertonic urine
  • Otherwise normal renal function (normal urea and creatinine)
  • Normal adrenal function
  • No evidence of extracellular fluid volume contraction (dehydration / hypotension)
  • Improvement of hyponatreamia following fluid restriction

 

Early symptoms include:

  • Weakness
  • Nausea
  • Vomiting
  • Headache

 

Late symptoms include

  • Confusion and restlessness
  • Convulsions
  • Drowsiness
  • Eventually, coma and respiratory arrest

 

Typically, patients have an initial uncomplicated post-operative recovery followed by symptoms of hyponatraemic encephalopathy

 

*28) A

 

Factors contributing to inappropriate ADH secretion in the post-operative period

 

  1. Pre-operative fasting: dehydration results in increased ADH secretion
  2. Pain & emotional stimuli: shown to increase ADH secretion. ADH levels shown to be increased by incision and stimulation of the pleura and peritoneum
  3. Haemorrhage: results in reduction of circulatory volume and stimulation of ADH secretion
  4. General anaesthesia: general anaesthetics produce an acute fall in GFR and urine volume with an increase in ADH secretion

Drugs: opiates and barbiturates increase ADH secretion

 

*29) C

 

Treatment options

 

  1. Fluid restriction to 1.5-2 L normal saline per 24h with sodium levels monitored every 2h. The aim is to raise serum sodium by 1-2 mmol/l per hour
  2. Hypertonic saline may be used but closer monitoring should be undertaken as a rapid rise in sodium concentration may lead to osmotic demyelination
  3. A loop diuretic such as furosemide may be used to enhance free water excretion and hasten the restoration of normal sodium concentrations