Post-operative medicine Flashcards
What is pulmonary artery occlusion pressure?
indirect measure of left atrial pressure, and thus filling pressure of the left heart.
What is a normal PAOP?
8-12mmHg
what does low PAOP mean?
<5
hypovolaemia
What does low PAOP with pulmonary oedema mean?
<5 ARDS
What does high PAOP mean?
> 18
overload
What does ASA I mean?
No organic physiological, biochemical or psychiatric disturbance. The surgical pathology is localised and has not invoked systemic disturbance
What does ASA II mean?
Mild or moderate systemic disruption caused either by the surgical disease process or though underlying pre-existing disease
What does ASA III mean?
Severe systemic disruption caused either by the surgical pathology or pre-existing disease
What does ASA IV mean?
Patient has severe systemic disease that is a constant threat to life
What does ASA V mean?
A patient who is moribund and will not survive without surgery
Which anaesthetic agent is associated with hepatotoxicity?
Halothane
How is TPN best administered?
Internal jugular vein via central venous catheter
for feeding < 14 days consider feeding via a peripheral venous catheter
for feeding > 30 days use a tunneled subclavian line
Which patients are at risk of malnutrition?
eaten nothing or little > 5 days, who are likely to eat little for a further 5 days
poor absorptive capacity
high nutrient losses
high metabolism
which patients are malnourished?
BMI < 18.5 kg/m2
unintentional weight loss of > 10% over 3-6/12
BMI < 20 kg/m2 and unintentional weight loss of > 5% over 3-6/12
ECG features in hyperkalaemia?
Peaking of T waves (occurs first)
Loss of P waves
Broad QRS complexes
Ventricullar fibrillation
What does TPN contain?
glucose, lipids and essential electrolytes, the exact composition is determined by the patients nutritional requirements.
Complications of TPN?
sepsis, re-feeding syndromes and hepatic dysfunction.
Pulmonary function tests in obstructive lung disease?
FEV1 - significantly reduced
FVC - reduced or normal
FEV1% (FEV1/FVC) - reduced (less than approx. 70%)
Pulmonary function tests in restrictive lung disease?
FEV1 - reduced
FVC - significantly reduced
FEV1% (FEV1/FVC) - normal or increased (over approx. 70%)
Examples of obstructive lung disease?
Asthma
COPD
Bronchiectasis
Bronchiolitis obliterans
Examples of restrictive lung disease?
Pulmonary fibrosis
Asbestosis
Sarcoidosis
Acute respiratory distress syndrome
Infant respiratory distress syndrome
Kyphoscoliosis
Neuromuscular disorders
Which muscle relaxant is an agent that is degraded by hydrolysis and may produce histamine release?
atracurium
Negative side effects of etomidate?
adrenal suppression
Post operative vomiting is common
Complications of using dextran?
Dextran 40 and 70 have higher incidence of anaphylaxis than either gelatins or starches
What is typically used to monitor cardiac output?
Swan Genz catheter
Swan-Ganz catheter can measure several variables it can be used to calculate:
Stroke volume
Systemic vascular resistance
Pulmonary artery resistance
Oxygen delivery (and consumption)
MOA of noradrenaline?
alpha agonist
Effect of noradrenaline?
Vasopressor action, minimal effect on cardiac output
MOA of adrenaline?
α and β receptor agonist
Effect of adrenaline?
Increases cardiac output and peripheral vascular resistance
MOA of dopamine?
β1 agonist
Effect of dopamine?
Increases contractility and rate
MOA of dobutamine?
β1 and β2 agonist
Effect of dobutamine?
Increases cardiac output and decreases SVR
MOA of milrinone?
Phosphodiesterase inhibitor
Effect of milrinone?
Elevation of cAMP levels improves muscular contractility, short half life and acts as vasodilator
Causes of ARDS?
Sepsis
Direct lung injury
Trauma
Acute pancreatitis
Long bone fracture or multiple fractures (through fat embolism)
Head injury (causes sympathetic nervous stimulation which leads to acute pulmonary hypertension)
Clinical features of ARDS?
Acute dyspnoea and hypoxaemia hours/days after event
Multi organ failure
Rising ventilatory pressures
Management of ARDS?
Treat the underlying cause
Antibiotics (if signs of sepsis)
Negative fluid balance i.e. Diuretics
Recruitment manoeuvres such as prone ventilation, use of positive end expiratory pressure
Mechanical ventilation strategy using low tidal volumes, as conventional tidal volumes may cause lung injury (only treatment found to improve survival rates)
wHY does ARDS cause hypoxaemia?
loss of surfactant and increased elastase release from neutrophils, results in fluid accumulation. This leads to reduced diffusion, which is the main reason for hypoxaemia.
How to calculate nutrition prescription for those at risk of refeeding syndrome?
-Start at up to 10 kcal/kg/day increasing to full needs over 4-7 days
-Start immediately before and during feeding: oral thiamine 200-300mg/day, vitamin B co strong 1 tds and supplements
-Give K+ (2-4 mmol/kg/day), phosphate (0.3-0.6 mmol/kg/day), magnesium (0.2-0.4 mmol/kg/day)
How to calculate nutrition prescription for those at risk of refeeding syndrome?
-Start at up to 10 kcal/kg/day increasing to full needs over 4-7 days
-Start immediately before and during feeding: oral thiamine 200-300mg/day, vitamin B co strong 1 tds and supplements
-Give K+ (2-4 mmol/kg/day), phosphate (0.3-0.6 mmol/kg/day), magnesium (0.2-0.4 mmol/kg/day)
Main side effect of neostigmine?
bradycardia
Management of neuropathic pain?
First line: Amitriptyline (Imipramine if cannot tolerate) or pregabalin
Second line: Amitriptyline AND pregabalin
Third line: refer to pain specialist. Give tramadol in the interim (avoid morphine)
If diabetic neuropathic pain: Duloxetine
N.B. SE of amitriptyline is orthostatic hypotension
Criteria for brainstem death testing?
Deep coma of known aetiology.
Reversible causes excluded
No sedation
Normal electrolytes
How to test for brainstem death?
-Fixed pupils which do not respond to sharp changes in the intensity of incident light
-No corneal reflex
-Absent oculo-vestibular reflexes - no eye movements following the slow injection of at least 50ml of ice-cold water into each ear in turn (the caloric test)
-No response to supraorbital pressure
-No cough reflex to bronchial stimulation or gagging response to pharyngeal stimulation
-No observed respiratory effort in response to disconnection of the ventilator for long enough (typically 5 minutes)
Who can test for brainstem death?
two appropriately experienced doctors on two separate occasions
at least 5y post grad experience
one must be consultant
not member of transplant team
which variables are required for calculation of SOFA score?
PaO2, platelet count, creatinine level, and bilirubin level, GCS, Cardiovascular MAP
Which variables are required for a quick (qSOFA) score?
Respiratory rate 22/min
Altered mentation (<15)
Systolic blood pressure 100 mm Hg
Which variables are required for a quick (qSOFA) score?
Respiratory rate 22/min
Altered mentation (<15)
Systolic blood pressure 100 mm Hg
What does a SOFA score >=2 indicate?
A SOFA score of 2 or more reflects an overall mortality risk of approximately 10% in a general hospital population with suspected infection
What are the goals of resuscitation?
CVP 8-12mmHg
MAP >65mmHg
Urine output >0.5ml/kg per hour
Superior vena cava oxygen saturation >70%
Normal lactate
What is septic shock?
sepsis with persisting hypotension requiring vasopressors to maintain MAP 65 mm Hg and having a serum lactate level >2 mmol/L (18mg/dL) despite adequate volume resuscitation
(mortality >40%)
What should be monitored before and during administration of TPN?
Weight
BMI: at start of feeding and then monthly
If weight cannot be obtained: monthly mid arm circumference or triceps skin fold thickness
Daily electrolytes until levels stable. Then once or twice a week.
Weekly glucose, phosphate, magnesium, LFTs, Ca, albumin, FBC, MCV
What should be monitored if stable on TPN?
- 2-4 weekly Zn, Folate, B12 and Cu levels if stable
-3-6 monthly iron and ferritin levels, manganese (if on home parenteral regime)
-6 monthly vitamin D
-Bone densitometry initially on starting home parenteral nutrition then every 2 years
Why should suxamethonium be avoided in extensive poly trauma and tissue necrosis?
may induce hyperkalaemia as it induces generalised muscular contractions
cardiac arrest
Which operations carry higher chance of anastomotic leak?
rectal resections
Which signs may indicate a new anastomotic leak?
new AF and raised inflammatory markers 5 days post resection
Enteral feeding of ITU patients?
ITU patients should have continuous feeding for 16-24h (24h if on insulin)
When can a PEG be used and removed?
PEG can be used 4 hours after insertion, but should not be removed until >2 weeks after insertio
Side effects of spinal anaesthesia?
hypotension, sensory and motor block, nausea and urinary retention.
Preferred anaesthetic technique for extensive laparotomy?
Transversus Abdominal Plane block (TAP)
What is pethidine?
Synthetic opioid which is structurally different from morphine but which has similar actions. Has 10% potency of morphine.
Differences between pethidine and morphine?
Short half life and similar bioavailability and clearance to morphine.
Short duration of action
