Perioperative Flashcards
14 Please look at these arterial blood gas results: pH 7.30, Pa O2 66mmHg, Pa CO2 26mmHg, base excess - 6.5, lactate 9.4. What is a summary description of these results?
This ABG shows metabolic acidosis with partial respiratory compensation. The low PaO2 and high lactate suggect cellular hypoxia and subsequent anaerobic metabolism has occurred
15 Please look at these arterial blood gas results: pH 7.30, arterial blood gas results: pH 7.30, Pa O2 66mmHg, Pa CO2 26mmHg, base excess - 6.5, lactate 9.4. What causes a blood gas profile of this sort?
This ABG shows metabolic acidosis with partial respiratory compensation. The low PaO2 and high lactate suggect cellular hypoxia and subsequent anaerobic metabolism has occurred
Causes of metabolic acidosis
1. Increased acid production (increased anion gap) - lactic acidosis, ketoacidosis, ingestion (methanol, ethylene glycol, aspirin)
2. Decreased bicarbonate - diarrhoea, ileostomy, proximal renal tubular acidosis, carbonic anhydrase inhibitors
3. Decreased renal acid secretion - CKD, renal tubular acidosis
Type A is the most likely cause in this scenario given a high lactate and hypoxaemia
16 What is a deep vein thrombosis?
A type of venous thromboembolism involving blood clot formation in the major deep veins of the:
- lower limb (popliteal, femoral)
- pelvis (iliac veins)
- abdomen (IVC)
DVTs typically form just above and behind a venous valve
Most are asymptomatic but can present with: asymmetrical swelling, unilateral leg pain, dilation of superficial veins, red/discoloured skin
17 Why is a DVT important?
DVT is important largely due to the complications that can occur if it is left untreated
- PE - occurs in 50% of patients with proximal DVT and 5% of patients with distal DVT. The 30 day mortality for an acute massive PE is 50%
- Post-thrombotic syndrome - pain, discomfort, swelling, pigmentation, venous ulcers. Due to incompetence of venous valves and subsequent venous stasis
- Complications of treatment - bleeding, heparin-induced thrombocytopenia, increased hospitalisation and associated risks e.g., pneumonia
18 What are some of the risk factors for hypercoagulability?
Inherited
- Factor V Leiden mutation (most common)
- Protein C deficiency
- Protein S deficiency
- Antithrombin deficiency
- Prothrombin gene mutation G20210A
Acquired
Malignancy, dehydration, sepsis, smoking, recent trauma or surgery, antiphospholipid syndrome, oestrogen (HRT, OCP), polycythemia, pregnancy, obesity, nephrotic syndrome
19 How can the risks of a DVT be reduced in a surgical patient?
Pre-operative
Smoking cessation, weight loss, cessation of hormonal therapies, good hydration
Post-operative
Behavioural: good hydration, early ambulation
Mechanical: TEDS, intermittent pneumatic compression
Pharmacological: Enoxaparin 40mg daily, dalteparin 5000 daily, LDUH 5000 tds, fondaparinux 2.5mg daily
20 What is Virchow’s triad?
Describes the 3 factors that contribute to venous thrombis formation
- *1) Endothelial injury** e.g., trauma, surgery, venepuncture, heart valve disease or replacement, atherosclerosis, indwelling catheters
- *2) Venous stasis** e.g., AF, immbolity, varicose veins, venous insufficiency, obstruction (pregnancy, tumour, obesity)
- *3) Hypercoagulability** (inherited or acquired)
21 You are the general surgery resident on call. You are asked to review a 70 year old man who is 72 hours post elective, uncomplicated colonic surgery. He has developed an acute confusion having been well and behaving normally since surgery. What are you going to do?
This patient most likely has post-operative delirium, defined as an acute and fluctuating disturbance in attention and/or awareness with additional disturbances in cognition, representing a change from baseline.
We need to establish delirium as the diagnosis, then investigate for a cause and manage accordingly.
1. Is this patient delirious?
Confusion Assessment Method (CAM)
1 + 2 + 3/4 required for diagnosis
1) Altered mental status (change from baseline) or fluctuating course (on/off or changing severity)
2) Inattention (easily distratced or difficulty following what is said) - serial 7s, “WORLD” backwards, months backwards
3) Altered level of consciousness (alert/vigilant to lethargic/stupor/coma) - Richmond Agitation Sedation Scale
4) Disorganised thinking (unclear/illogical flow of ideas, unpredictable switching between subjects)
2. Cause/investigations
Disorientation from rapid changes in environment
Dehydration - skin turgur, mucous membranes etc. haematocrit
Hyponatremia - nausea, vomiting, headache, seizures, muscle cramps, UECs
Glucose abnormalities - fingerprick, polydipsia, tremor, anxiety, tachycardia, hunger
Drugs/toxins (benzodiazepines, anticholinergics, withdrawal) - history
CNS lesion - neurological examination
Infection, especially UTI and pneumonia - urine MCS, CXR, dysuria, cough, dyspnoea
3. Management
Reverse causes
Aids to help orientation - stay in the one location, photos from home, regular nurses, clocks, calendars
22 You are the general surgery resident on call. You are asked to review a 70 year old man who is 72 hours post elective, uncomplicated colonic surgery. He has developed a fever of 38.2 degrees C, having had no fever recorded since surgery. What are you going to do?
Fever is common in the first few days following major surgery and is most commonly caused by inflammation from surgery and resolves. However, fever developing or persisting beyond 48 hours post-op warrants investigation
The 5 Ws of Post-Op Fever
• Wind (24-48 hours) - i.e. chest infection
- Predisposition - instrumentation of airway during GA ⇒ air stasis, inadequate pain relief ⇒ air stasis
• Water (3-5 days) - i.e. UTI
- Especially if urinary catheter in place
• Walking (4-6 days) - i.e. VTE
- Due to stress response of surgery or immobilisation
- Should have prevention (low-molecular weight heparin) and stockings
• Wound (5-7 days) - i.e. SSI
- If considering, think about an intra-abdominal or intra-thoracic collection
• What have we done? - i.e. iatrogenic causes
- Medication reactions
- Cannula site infections
- Blood transfusion reactions
Clinical assessment would be focused on determining which of the 5 Ws is responsible
1) Initial assessment
- Observations - BP, HR, RR, O2 sats, temperature, GCS
- Systems-based assessment for cause
→ Wind: pleuritic chest pain, productive cough
→ Water: catheterised, frequency, urgency, dysuria
→ Walking: pressure sores, calf pain, leg swelling
→ Wound: change in pain around site, dry/healthy vs. red/pus/hot
→ Wonder: cannula site assessment, medication allergies
- DECIDE: is the person septic? (2+ SIRS + source of infection + associated organ dysfunction)
2) Review notes for:
- Post-op notes - what procedure? Any intra-operative complications?
- Co-morbid conditions
- Current reported clinical issues
3) Review chart for:
- Antibiotics
- VTE prophylaxis
- C. difficile infection risk
Investigations/management
• Suspicion-specific investigation
- Wind = sputum, CXR
- Water = urine dipstick/MCS
- Walking = coagulation studies, USS
- Wound = swab
- Wonder = line sample, culture of line tip
• Sepsis 6
- Give 3 - high flow O2, broad-spectrum antibiotics, fluid challenge
- Take 3 - blood cultures x 2, lactate (via ABG) and other bloods (FBC, CRP/ESR, UEC, LFT), monitor urine output
• Other supportive medication (e.g. analgesia, anti-emetic)
• VTE prophylaxis correction (if inadequate)
• Escalation - notify registrar
23 You are the general surgery resident on call. You are asked to review a 70 year old man who is 12 hours post elective, uncomplicated colonic surgery. He has developed an acute episode of hypotension, which has persisted for 10 minutes. What are you going to do?
- *Confirm hypotension and assess severity**
- Compare with previous
- HNE Health: <100 is yellow, <90 is red (but review chart for change in calling criteria) - MET call (7700) if red
- *Primary survery** - assess whether shocked or septic
- Assess alertness and orientation - assume shock if unresponsive and hypotensive
- Brief history concurrent with ABC resuscitation (2x large-bore IVC), supportive care (supplemental O2), temperature measurement
- Assessment of organ perfusion - tachycardia, altered cognition or reduced LOC, diaphoresis, and oliguria are all suggestive of shock, serum lactate
Assess for aetiology
Most common causes: pain, anxiety, hypercapnia, hypoxiam bladder distention
Hypovolemia - iatrogenic, haemorrhagic
Decreased cardiac output - MI, dysarrhythmia, hypoxia, pneumothorax, PE, cardiac tamponade
Decreased peripheral resistance - sepsis, anaphylaxis, morphine
- *Investigations**
- Bedside: pulse oximetry, ECG, ABG
- Bloods: FBC, UEC, LFTs, coags, BSL, TSH, group and hold
- Targeted: D-dimer, serum troponin, FAST scan
Management
Consult senior staff
Haemorrhage - transfusion, fix cause if possible
PE - anticoagulate/tPA
MI - PCI/thrombolysis
Anaphylaxis - adrenaline
Septic - culture and Abx
24 You are the general surgery resident on call. You are asked to review a 70 year old man who is 24 hours post elective, uncomplicated colonic surgery. His urine output has dropped from an average of 60mL/hr in the first 24 hours to 20mL/hr in the last 2 hours. What are you going to do?
Oliguria is output <0.5mL/kg/hr. Therefore, this patient is oliguric.
Low urinary output is a common postoperative problem. The most common cause is urinary retention, particularly in males. It is readily diagnosed if there is a palpable suprapubic mass which is dull to percuss. A diagnosis can be confirmed by an US or by passing a urinary catheter.
More sinister causes include hypovolemia, cardiac failure, MI, urethral injury and sepsis
Catheter dysfunction may also be the cause
Initial actions
1) ABCDE, assessing for shock
1) Does the patient need to pee? If yes, drain bladder for rentention
2) Assess the level of renal failure - zero output or some output?
Zero output = post-renal obstruction = reposition patient, check Foley catheter function)
3) If some output, give fluid challenge
Improvement = dehydration = optimise hydration, consider central venous line for CVP monitoring)
No improvement = intrinsic renal cause = call for nephro consult
25 What are the symptoms and signs of a PE?
Symptoms: dyspnoea, chest pain (worse with inspiration), cough, haemoptysis
Signs: tachycardia, tachypnoea, hypotension, elevated JVP (uncommon)
26 How is a PE diagnosed?
If haemodynamically unstable
Bedside echocardiography or venous compression ultrasound to justify the administration of potentially life-saving therapies
If haemodynamically stable
Combine a clinical and pretest probability assessment (e.g., Well’s score) with D-dimer testing and definitive diagnostic imaging (e.g., CTPA, V/Q scan)
Wells score > 4 - immediate UF followed by CTPA
Wells score 4 or less
If poitive D dimer - CTPA
If negative D dimer - PE unlikely
27 How is a PE treated?
1) Correct any haemodynamic instability (resuscitate)
2) Transthoracic echo (if still unstable)
3) Anticoagulation (unless contraindicated)
4) Thrombolysis
5) Surgical or catheter embolectomy
28 What is a pulmonary embolism?
Obstruction of the pulmonary artery or one of its branches by material (thrombus, fat, tumour, air) that originated elsewhere in the body
Massive PE is that which causes haemodynamic compromise or where >30% of the pulmonary vasculature is compromised
Can be further defined by:
- Presentation: acute, subacute (days/weeks), chronic (months/years)
- Stable/unstable haemodynamics
- Anatomy: saddle, lobar, segmental
- Symptomatic/asymptomatic
Clinical presentation: dyspnoea, pleuritic chest pain, tachycardia, tachypnoea, haemoptysis, signs of DVT
Assess likelihood with Wells criteria - used as guide for whether D-dimer is warranted (only in low likelihood to rule out PE)
30 What are the important contraindications for a patient to have an epidural catheter placed for analgesia?
35 What is the adult daily potassium requirement? How do you usually prescribe this for IV infusion?
0.5-1 m mol/kg
+ 10 mmol in 10 mL of NaCl is available
