General Duties Flashcards
Ideal body weight calculation
Height in cm - 100 for men or 105 for women
List some parametric tests
Two sample t-test
Paired t-test
ANOVA
Pearson’s correlation coefficient
List some non-parametric tests
Mann-Whitney U test
Wilcoxon rank-sum
Kruskal-Wallis test
Spearman’s rank correlation coefficient
What is the concentration of intralipid for LA toxicity?
20%
What is the initial bolus dose required for intralipid in LA toxicity?
1.5ml/kg
What is the infusion rate of intralipid for LA toxicity?
15ml/kg/hr
2 further bolus doses can be given 5 mins apart
Double rate of infusion to 30ml/kg/hr if clinical situation unchanged
What is the maximum cumulative dose of intralipid?
12ml/kg (?)
Name the structures in the paravertebral space
Parietal pleura (anteriorlateral)
Superior costotransverse ligament (posterior) - need to go through this to get to paravertebral space
Intercostal nerve
?sympathetic chain
List common complications associated with paravertebral block at T4
Pneumothorax Vascular puncture Dural puncture Horner’s syndrome Harlequin syndrome
What are the features of Harlequin syndrome?
Contra-lateral hyperperfusion
So the face on the opposite side is all red
After a PVB a patient has ipsilateral miosis. What condition is this likely to be and how would you confirm your diagnosis?
Horner’s syndrome
Ptosis, miosis, anhydrosis & enopthalmos
Describe the features of Parkinson’s disease
Tremor Bradykinesia Rigidity Autonomic features - BP control GI - constipation CNS - low mood/dementia Quiet voice, slow speech
Describe the classes of drugs used in PD
Dopamine - Levodopa (plus something to try and prevent peripheral L-dopa breakdown)
Domaine agonists - apomorphine/rotigotine
MAO-B inhibitors - selegiline
COMT inhibitors - entacapone
Anti-cholinergics
What other treatments exist for Parkinson’s Disease?
Deep brain stimulation - electrodes into subthalamic nuclei connected to pulse generator
What drugs should be avoided for anaesthesia of a PD patient?
Atropine Halothane High dose Fentanyl/Alfentanil DIRECT ACTING sympathomimetics DA antagonists Serotonin syndrome - Tramadol
What considerations are needed for a PD patient having an operation?
Surgery timing (first)
Ensure drug regime continued and minimise disruption
Avoid prolonged starvation
RA vs GA
Poor swallow - airway concerns
Interference/artefact with electrical equipment - from tremor
Think if they have a DBS - diathermy, checking the machine still works afterwards etc
May not be able to work PCA
May need critical care admission if severe PD - complex multisystem disease
What PD drugs can be given via a different route to PO?
Rotigotine
Apomorphine
These discussions should be made with a PD specialist (and a patient)
Critical care admission may be required
How do you describe doing a nerve block?
Consent Block name Equipment needed: trained assistant, AAGBI monitoring, venous access, access to resus equipment/intralipid Patient position Asepsis & LA to skin US +/- NS settings Probe orientation and location Structures identified; needle end point Injection method - slow incremental injection with rate always <20ml/min Post block instructions
Definition of major haemorrhage?
150ml/min blood loss
Loss of 50% blood volume in <3 hours
Loss of entire circulating blood volume in 24 hours
How would you manage a major trauma ?
Trauma call ABC -secure airway -apply O2 IV access Crossmatch Activate major haemorrhage protocol Give TXA
Early diagnosis of bleeding points and management - CT/surgery/binders/haemostatic dressings
What parameters do you transfuse to in major haemorrhage? (Or other parameters you want to stick to)
Systolic BP ~100mmHg Aim for Hb 90-100 during bleed; above 80 afterwards Hct >0.3 Plts >100 Fibrinogen >1.5g (2 in obstetrics) Ionised calcium Ca2+ >1mmol/L pH >7.2 BE 36
What is damage control resuscitation?
Maintain circulating blood volume, control haemorrhage and correct lethal triad of trauma (hypothermia/acidaemia/coagulopathy)
What are the principles of damage control resuscitation?
Damage control surgery
Permissive hypotension (except in head injury)
Rapid rewarming
Limit crystalloid
Early blood component therapy
Correct hypofibrinogenaemia & coagulopathies
What is damage control surgery?
Limited surgery interventions to control haemorrhage and minimise contamination
Come back later when patient more stable
These patients have reduced acidaemia/hypothermia/coagulopathy on arrival to ICU if the surgery is SHORT (<1hour)
What is the mechanism behind acute traumatic coagulopathy?
Activated protein C causes anticoagulation
Endothelial glycocalyx releases heparin when disrupted
Loss of fibrinogen
Platelet dysfunction from initial hyper activation as a result of widespread ADP release from endothelial cells
Define neuropraxia
Temporary physiological interruption of conduction without loss of atonal continuity
Define axonotmesis
Loss of relative continuity of the axon and its covering of myelin, but preservation of the connective tissue framework of the nerve
Define neurotmesis
Total severance or disruption of the entire nerve fibre with no distal nerve conduction
What is prehabilitation?
The process of enhancing an individual’s functional capacity to enable them to withstand a forthcoming stressor such as major surgery
What are the 2 main models to describe frailty?
Frailty phenotype
Frailty index
Give an example of a tool to describe frailty
Edmonton Frail Scale
Canada Study of Health and Ageing (CSHA) frailty index
List some risk factors for frailty
Age Female sex Lower socioeconomic class Depression Disability Comorbidities such as cardiovascular disease Diabetes Stroke Cancer Arthritis COPD Anaemia
What are the 4 main components of prehabilitation?
Medical optimisation
Physical activity
Nutritional support
Psychosocial support
What are the potential benefits of prehabilitation?
Shorter length of stay
Reduced post operative pain
Fewer post-op complications
What 3 physiological benefits may be gained from physical training as part of a prehabilitation program?
Improve functional reserve Improve mitochondrial oxygen uptake Improved lean body weight/weight loss Improved anaerobic threshold Improved VO2 max.
Give 4 benefits of carbohydrate preloading and nutritional optimisation
Shorter fasting time Improved wound healing Reduced length of stay Reduced infection Decreased insulin resistance Promotes anabolic state
Define delirium
Acute disturbance in cognitive state with fluctuations in orientation
What drugs are safe to use in porphyria?
Propofol
Fentanyl
Atracurium
What drugs need to be avoided in acute haemolytic porphyria?
Thiopentone Etomidate Ketamine Anything that stimulates P450 Antibiotics (although penicillins are ok) Antifungals Dexmedetomidine Anti-arrhythmics Ergometrine Anti-epileptics
What is acute hepatic porphyria?
Group of AUTOSOMAL DOMINANT conditions
Partial deficiency in the activity of enzymes involved in haem synthesis
Most common = AIP
Then hereditary coproporphyria and variegateporphyria
Build up of products - ALA & PBG - build up and cause attacks
Haem suppresses the whole pathway and stops attaches
What are some features of a Neurovisceral attack in Acute Hepatic Porphyria?
Abdo pain Hypertension Seizures Confusion N&V Peripheral neuropathy
What investigation would you do to confirm an attack of AHP?
PBG (urine)
Has to be taken at the time of the attack
Can also do plasma and faecal sample for porphyrin
What are the anaesthetic principles for a patient with AHPorphyria?
Minimise starvation time
Avoid precipitant drugs
Minimise stress by using good analgesia and avoiding PONV
Consider early epidural in obstetrics
How would you manage an acute attack of AHP?
Remove or treat participating factor Maintain carb intake Effective pain management Control PONV Exclude other causes of abdominal pain Monitor for neuropathy Send urinary PBG Involve UK NAPS to arrange giving HAEM ARGINATE (reduces duration of attack but causes severe thrombophlebitis)
What perioperative consequences may be associated with pre-operative anaemia?
Risk of cancellation of case - delayed treatment
Poor wound healing
Longer hospital stay
Higher risk of complications - MI, wound infections/LRTI/UTI
Increased all cause morbidity and mortality
High risk of needing blood transfusion and its assoc risks
What adaptions occur to offset effects of anaemia?
Increased O2 extraction
Increased CO - decreased SVR from reduced blood viscosity/sympathetic response
R shift of OHDC due to increased 2,3DPG
Redistribution of cardiac output to high demand areas
Describe perioperative events that will worsen the effects of anaemia?
Shivering Pain Stress response Fever Hypoxaemia if inadequate oxygen therapy etc Reduced CO from anaesthetic agents Blood loss from surgery Reduced erythropoiesis due to inflammatory response Hypothermia causing L shift of OHDC
What further blood tests may help the classification of this anaemia?
B12
Folate
Iron
Ferritin
Reticulocyte count - low count = bone marrow problem; high count = haemolysis
Total iron binding capacity - raised in IDA
Transferrin saturations - low in IDA
What scoring systems can be used to help predict perioperative risk before major surgery?
ASA POSSUM SORT Revised CRI Nottingham hip fracture score V-POSSUM Carlisle risk calculator for elective AAA
What are the main measures of fitness obtained by CPET?
Anaerobic threshold - the level of O2 delivery at which anaerobic metabolism occurs
VO2 peak
Workload
What abnormalities seen at time of testing in CPET may suggest cardio-respiratory disease?
Rapid rise in HR Reduced peak O2 pulse (reduced SV) ECG abnormality Reduced BP with exercise Raised ventilatory equivalent for CO2/O2 Spirometry abnormalities such as significant reductions in FVC, FEV1 Reduced SpO2 at peak exercise
How can frailty be assessed?
End of the bed/first clinical impression of an experienced doctor/clinician
ASA score
Clinical frailty scale (score 1-9)
Edmonton Frail Scale
Canadian Study of Health and Aging clinical frailty scale
Electronic Frailty Index (using SystemOne)
What drugs would you use in a hypertensive response to phaeochromocytoma tumour handling?
Mg Phentolamine GTN Sodium nitroprusside Nicardipine Esmolol
Define difficult airway
Difficulty with face mask ventilation/supraglottic device ventilation/endotracheal intubation or all 3
>2 attempts at laryngoscopy using direct laryngoscopy
What are the contraindications to AFOI?
Inexperienced operator Basal skull fracture Allergy to LA Infection/contamination of upper airway - bleeding/friable tumour/abscess Distorted anatomy Impending airway obstruction (cork in a bottle) Uncooperative patient Penetrating eye injury
What are the muscles of the larynx and what do they do?
Cricothyroid - tenses vocal cords
Thyroarytenoid and vocalis - slacken vocal cords
Lateral cricoarytenoid and transverse arytenoids - adduction of vocal cords
Posterior cricoarytenoid - abduction of vocal cords
What is the nerve supply to the larynx?
Recurrent laryngeal to all intrinsic muscles of larynx except cricothyroid (external laryngeal)
Recurrent laryngeal - sensation below glottis
Superior laryngeal nerve - internal branch - sensation above glottis
You used AFOI to intubate the patient. How would you be sure the patient is safe at extubation?
Extubate in theatre with assistant
Appropriate drugs ready for reintubation
Appropriate equipment for reintubation
Verbalise plan
Surgical team in theatre
Observation in theatre prior to transfer to recovery
Ensure: CVS stability, RS stability, Metabolic/Temp stability, Neuromuscular function returned
State three factors that affect blood viscosity
Temperature
Flow rate
Haematocrit
List intraoperative strategies to maintain perfusion to a free flap
Normothermia Normovolaemia Vasodilatation from anaesthetic agents Sympathetic blockade - paravertebrals/epidurals Minimised handling of flap
List 2 surgical and 2 non-surgical causes of free flap failure
Surgical:
- Arterial - vessel spasm/trauma/thrombus/technical problems with anastomoses
- Venous - kicking of anastomosis, thrombus, haematoma compressing drainage
Non-surgical:
- Oedema from excess fluid
- Hypercoagulable state
How do you assess a free flap?
Colour CRT Skin turgor Skin temperature Bleeding on pinprick Doppler
What happens at the initiation of exercise?
Resp and CVS increase O2 demand
Increased CO and Vasodilatation through:
-Vasodilatory metabolites - H+, K+, PO4, AMP and adenosine
-Improved O2 dissociation through increased temp/reduced pH
-Increased muscle blood flow
CO increases:
- SV increase from increased venous return and increased inotropy from catecholamines
- HR increase from SNS stimulation and vagal inhibition
What is the maximum HR?
Maximum HR = (220 - age) +/- 11
What is the anaerobic threshold?
The point at which O2 demand of muscles exceeds the ability of the cardiopulmonary system to supply O2
Where blood lactate rises as metabolism switches from aerobic to anaerobic
Marker of exercise intensity Occurs from: -Low muscle O2 -Accelerated glycolysis -Recruitment of fast twitch fibres -Reduced rate of lactate removal
What is VO2?
Oxygen consumption
What is CPET?
A dynamic, non-invasive assessment of cardiopulmonary system at rest and during exercise
Determines functional capacity
What are the CPET-derived variables?
What other measurements can CPET record?
Anaerobic threshold - AT
Peak O2 consumption - VO2peak
Ventilatory efficiency for CO2 - VE/VCO2
Maximum workload/rate
Respiratory exchange ratio (RER) - VCO2/VO2 Work rate (in Watts) Ventilatory measurements: -SpO2 -VE -Vt -RR -VE/VO2 & VE/VCO2
CVS:
- HR
- ECG ST segment changes
- NIBP
Which CPET-derived variables are associated with poor postoperative outcomes?
Anaerobic threshold <11
Peak O2 consumption (VO2peak) <15
Ventilatory efficiency for CO2 (VE/VCO2) 36
Mortality/morbidity/ICU admission/LoS
What is the normal CVS response to exercise?
Increase in systolic BP Reduced SVR (increasing muscle perfusion) Increased venous return
CO increases in proportion to intensity of exercise from increase HR and SV
How is CPET done?
What equipment is needed?
Electromagnetically braked cycle ergometer Rapid gas analyser Pressure differential pneumotachograph ECG SpO2 NIBP
Measurements taken:
- at rest
- during unloaded cycling
- during increasing resistance
- in recovery phase after cessation of exercise
Inputting patient gender/height/weight/age calculates a normal value which is then compared to those obtained
What is VO2peak?
What is VO2max?
VO2max is the maximum VO2 achievable by an individual performing a specific type of exercise
-often not achieved by elderly/co-morbid
The plateau of O2 uptake at a certain work rate
The O2 intake during exercise at which actual O2 intake reaches a maximum beyond which no increase in effort can raise it
VO2peak is the highest VO2 measured
- often the point at which the test is terminated
- regardless of the subject’s effort