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bookmarked qns surgery > pre-op management > Flashcards

pre-op management Flashcards

1
Q

What is the composition of the following fluids:

0.9% saline
5% dextrose
0.18% NaCl/ 4% dextrose

A

A 1% solution contains 1g per 100ml of solvent

  • 0.9% saline is 150 mmol/L of Na and 150 mmol/L of Cl
  • 5% dextrose is 50g of dextrose
  • 0.18% NaCl/4% dextrose is 40g of dextrose and 30mmol/L of Na and 30mmol/L of Cl
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2
Q

How does 0.18% NaCl/4% Dextrose distribute across body compartments?

A

Theorectically this fluid is 1 part 0.9% NaCl (200ml) and 4 parts 5% Dextrose (800ml)

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3
Q

IV fluids need to be isotonic so as not to damage red blood cells. However 4% Dextrose/0.18% Saline is hypertonic, why is this and why can it be used as a fluid?

A

Initially dilutes osmolality of extracellular fluid but once cell has used the dextrose, the remaining saline and electrolytes act isotonic

5% dextrose is isotonic as the dextrose is metabolised to water

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4
Q

Why is there a normal postoperative phase of oliguria?

A

Surgery is trauma which causes ADH and cortisol release which causes more water to be reabsorbed in the kidney so less urine produced

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5
Q

Why are many surgical patients in fluid/electrolyte deficits?

A
  • Vomiting from intestinal obstruction: vomiting causes loss of isotonic fluid leaving space in gut for more to be sequestered so many patients in hypovolaemic shock as lost a lot of fluid from ECF
  • Peritonitis: large surface area so if inflammad can give off litres of fluid as normal blood flow is 150ml/min and SA is 2m2
  • Fistulae
  • Bleeding
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6
Q

What are some useful biochemical markers for dehydration in a patient who is vomiting due to a bowel obstruction?

A

Raised haematocrit (>55%)
Raised serum urea
Raised serum urea in comparison to creatinine as urea can be reabsorbed but creatinine cannot

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7
Q

What are some of the reasons colloids are not often used?

A

High cost
Risk of anaphylaxis
Increased risk of coagulopathy

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8
Q

What are some of the different enteral feeding options?

A

TPN is used when intestinal failure (e.g perforations or short gut from resection) or cannot access jejunum
Hierarchy of feeding
Tube enterostomies are used long term when need feeding over 4 weeks. PEG better as can be used for night feeds with less risk of aspiration

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9
Q

What causes low albumin levels?

A

Chronic inflammation
Protein losing enteropathy
Proteinuria
Hepatic dysfunction
NOT MALNUTRITION

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10
Q

What are the consequences of poor pain control?

A
  • Slower recovery time due to reluctant to mobilise
  • Inadequate ventilation leading to possible subsequent atelectasis and hospital-acquired pneumonia as they are not breathing as deeply as they would if they were not in pain
  • Cardiovascular: tachycardia, hypertension
  • GI: ileus, N+V, urinary retention, ileus
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11
Q

What are the side effects of NSAIDs?

A

Work by decreasing synthesis of prostaglandins so decreased inflammation

IGRAB

interactions with other drugs
gastric ulcerations
renal impairment
asthma sensitivity
bleeding risk

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12
Q

side effects of opioids

A

dry mouth
eurphoria
sedation
constipation
nausea and vomiting
respiratory depression

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13
Q

when do PEs classically occur?

A

10-12 days post op

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14
Q

how can post op DVT be prevented

A

pre-op mobilisation
post - op mobilisation
stop thrombotic drugs
TED stockings

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14
Q

How does the dose of dalteparin vary if a patient is renally impaired? (eGFR<30)

A

Need to use a lower dose (2/3 of body weight if treating VTE) OR

Use UFH

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14
Q

How long is dalteparin prophylaxis given for?

A
  • Normal surgery: give dose 1-2 hours before surgery then every 24 hours whilst at risk of VTE
  • Major orthopaedic surgery (e.g THR/TKR): consider Dalteparin for up to 35 days after surgery if high risk
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14
Q

What are some contraindications of mechanical VTE prophylaxics (AES and IPC)?

A

Peripheral arterial disease
Peripheral oedema
Local skin conditions.

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15
Q

How do you reverse the following anticoagulants?

Dabigatran
LMWH
Rivaroxaban
Warfarin (reversal needed for procedure in 5 days)
Warfarin (immediate reversal)
Warfarin (reversal needed for procedure next day)

A

short half life but idarucizumab can be used
Witholding usually sufficient due to short half life but protamine can be use
Withold drug 24 hours as not reversal, can try PCC
Withhold drug and bridge with LMWH till 24 hours before
- Prothrombin Complex Concentrate

  • Vitamin K
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16
Q

When do you need to do bridging therapy when stopping warfarin for surgery?

A

If high risk of VTE (e.g VTE within last 3/12, AF with previous stroke or TIA, or mitral mechanical heart valve) then bridge

Start LMWH and stop 24 hours before surgery if surgery has high bleeding risk

Start warfarin again at night after surgery that day

17
Q

Q
How long before surgery do you need to stop aspirin and clopidogrel?

A

Aspirin: 7-10 days before

Clopidogrel: 7 days before

18
Q

wells score for DVT and what is the management?

A
  • If 1 or less DVT is unlikely but do D-Dimer to rule out. D-dimer can also be raised in recent surgery/trauma, pregnancy, liver disease, infection, prolonged hospital stay
  • If 2 or more DVT likely so do US
    mx: DOACs first line or dabigatran
19
Q

How are PEs investigated and managed?

A

Ix

  • Wells Score less than or equal to 4: PE unlikely, but D-dimer test to exclude
  • Wells Score greater than 4: PE likely and confirm diagnosis with CTPA scan (or V/Q scan in those with poor renal function).

Can do ECG to rule out MI differential and may have S1Q3T3
Mx

  • Interim anticoagulation: offer apixaban or rivaroxaban first line for 5 days then dabigatran for 5 days

If CTPA is negative stop anticoagulation
If CTPA positive keep on anticoagulation for 3 months if unprovoked, longer if provoke
If haemodynamically unstable give oxygen, continuous UFH infusion and consider systemic thrombolytic therapy

20
Q

When diabetic patients are due to have surgery, how is their blood glucose control altered to their normal regime? (use flowchart)

A

If expected to miss more than one meal put on variable rate intravenous insulin infusion of soluble human insulin in sodium chloride 0.9 % (sliding scale)
Need to run intravenous glucose-containing ‘substrate solution’ alongisde it
Need to check BM hourly, especially for first 12 hours of VRII, to see if in range of 6-10 mmol/L (4-12 acceptable)
Conversion back to s/c insulin when patient can eat and drink with no N+V with overlap of 30 minutes

21
Q

How can you tell if a diabetic patient is hypoglycaemic whilst under anaesthesia and what are the consequences of this?

A

There is no way, you just have to monitor BM!! Sugars often go up in surgery due to stress response
Risk of brain injury and seizures as not aerobically respiring

22
Q

Why is there a risk of aspiration of gastric contents during induction of anaesthesia?

A

Relaxation of lower esophageal sphincter
Lower level of consciousness
Loss of protective reflexes

23
Q

what are intraoperative hypo and hyperglycaemia treated at

A

hypo: less than or equal to 4mmol/l
hyper: more than or equal to 12mmol/l

24
Q

Why is potassium not often given in fluids after surgery?

A

Trauma of surgery causes rhabdomyolysis so may be slightly raised from this anyway

25
Q

What surgical patients are at high risk of deterioration?

A

Surgical emergencies
Elderly
Pre existing diseases
On steroids
Massive blood transfusions

26
Q

What are some of the complications of too much fluid or too little fluid in fluid prescriptions?

A

Too much

Pulmonary oedema
ARDS
Peripheral oedema
Electrolyte imbalances
Hyperchloraemic acidosis
Too little

AKI
Dehydration
Hypovolemia
Poor end organ perfusion

27
Q

What are the clinical and biochemical features of an Addisonian crisis?

A

Clinical:

Severe weakness
Confusion/Reduced Consciousness
Pain in lower back or legs
Severe abdominal pain, vomiting and diarrhea, leading to dehydration
Biochemical:

Hypotension
Hyponatraemia
Hyperkalaemia
Sometimes hypoglycaemia

28
Q

Addison’s crisis can cause death by circulatory collapse and arrhythmias with hypoglycaemia contributing.

What is the treatment for an Addisonian crisis?

A
  • Bloods for cortisol and ACTH
  • U+Es (do ECG for K+ and give Ca gluconate if needed, fluids and steroids will resolve low Na)
  • 100mg Hydrocortisone IM/IV stat
  • IV fluid bolus for hypotension
  • Monitor BM for hypoglycaemia

Continue Hydrocortisone 100mg/8hr and change to oral steroids after 72 hours
Continue fluid resus until electrolytes balanced

29
Q

How are MRSA surgical site infections managed?

A

Ciprofloxacin.
Co-trimoxazole.
Doxycycline.
Trimethoprim.

30
Q

How is post-op fever investigated?

A

A
- Sepsis screen

Blood tests– FBC, CRP, U&Es.
Urine dipstick
Cultures– blood, urine, sputum, and wound swab
Imaging– Chest X-ray
CT - Anasotmotic leak
Doppler US - DVT

31
Q

What are some causes of a post-op fever?

A

Day 1-2 – respiratory source (often atelectasis)

Day 3-5 – urinary tract source

Day 5-7 – surgical site infection or abscess/collection f

Any day post-operatively – consider infected IV lines or central lines as a source

Others: drug induced reactions (abx or anaesthesia), transfusion reaction, PE, DVT, pyrexia of unknown origin, secondary to prosthesis

32
Q

What are the different type of oxygen delivery systems?

A

Low flow (do not meet inspiratory demand, oxygen dilute with air)

Nasal cannula
Simple face mask
High flow

Venturi mask
Non-rebreather mask

33
Q

Why may patients become dyspnoeic or hypoxic following surgery and how do you manage them?

A

Causes: pneumonia, pulmonary collapse, PE, LVF due to fluid overload, pneumothorax, drugs

Mx:

Sit up and monitor sats
Assess airway then give oxygen or bag valve mask
Examine and listen to chest
Take FBC, ABG, CXR, ECG and manage accordingly

34
Q

Why may some patients have oliguria after surgery and how is this managed? (aim for >30ml/h or >0.5ml/kg/h)

A

Anuria: Blocked or malsited catheter so flush catheter

Oliguria: Often due to too little replacement of lost fluid or AKI so increase fluid input. AKI can be due to shock (septic/hypovolemic), transfusion, pancreatitis, trauma

Mx

Review fluid chart
Check for urinary retention by looking for palpable bladder
Fluid challenge
Catheterise
Stop nephrotoxic drugs

35
Q

What are the issues with PONV?

A

increased anxiety for future surgical procedures
increased recovery time and hospital stay
aspiration pneumonia
incisional hernia or suture dehiscence
bleeding
oesophageal rupture
metabolic alkalosis

36
Q

How are the components of donated blood broken down?

A

Red cells: to increase oxygen carrying capacity and replace blood loss

Platelets: often used prophylactically for patients with thrombocytopenia

FFP: contains clotting factors used for DIC and massive haemorraghe. Not recommended for warfarin reversal

Cryoprecipitate: source of fibrinogen and factor VIII given when low levels of clotting factors

37
Q

What are some acute transfusion reactions and how do they present?

A
  • Acute haemolytic transfusion reaction: fever, chills, hypotension, tachycardia, haemoglobinuria, due to ABO incompatibility
  • Anaphylaxis: urticaria, pruitis, wheezing, hypotension, angiooedema, due to reaction to foreign plasma proteins
  • Febrile Non-Haemolytic transfusion reaction: just a temperature rise
  • Transfusion related fluid overload
  • Bacterial contamination
38
Q

What are some alternatives to blood transfusions for surgical patients?

A

Consider EPO if anaemia and stopping anticoagulant/antiplatelets in pre op assessment
- Oral/IV iron before and after surgery if iron deficiency anaemia

  • Tranexamic acid for any expected blood loss >500ml

Intraoperative cell salvage (filter loss blood and put in saline and give back to patient)

39
Q

What is the definition of a massive blood transfusion?

A

Transfusion of 10 units of packed red blood cells (PRBCs) within a 24 hour period

40
Q

What are the aims of anaesthesia (image) and the stages of it?

A

Induction:
Analgesics (fast acting opioid e.g fentanyl)
Hypnotic (IV propofol)
Muscle relaxant (suxamethonium)
Airway management (laryngeal mask supraglottic or ET tube for longer operations)

Maintenance:
Monitor BP/HR/sats/Temp
IV infusion or volatile agent (added to N2O mix) with mechanical ventilation

Recovery
Change inspired gases to 100% oxygen
Discontinue anaesthesia and reverse muscle relaxant
Extubate patient

41
Q

Apart from anaesthetic agents, what are some other drugs an anesthetic may give to a patient?

A
  • Anxiolytics: e.g benzodiazepines like lorazepam for pre meds
  • Analgesics
  • Anti emetics: e.g ondansetron
  • Anatacids: e.g ranitidine if risk of aspiration
  • Antibiotics
42
Q

What are some examples of amnesia agents?

A

Benzos (midazolam)
Propofol
Ketamine
Thiopentone sodium

43
Q

What are some examples of muscle relaxants used in anaesthesia?

A

Depolarising: Succinylcholine

Non depolarising: Atracurium, Rocuronium

Used for skeletal muscle relaxation to aid intubation. Diaphragm is first to relax and first to come back

44
Q

What are some complications of anaesthesia and why do they arise?

A
  • Loss of pain: urinary retention, pressure necrosis, local nerve injuries e.g arm hanging off table
  • Consciousness: cannot communicate
  • Loss of muscle power: corneal abrasion (tape eyes), no cough reflex so risk of pneumonia and atelectasis, no respiration

bookmarked qns surgery (10 decks)

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