Critical Care Flashcards
(45 cards)
How can local anaesthetics be classified?
Amides - lidocaine, bupivacaine, prilocaine
Esters - cocaine, procaine
What are the possible complications of local anaesthetics?
Neurological - personal & glossitis paraesthesia, light-headedness, drowsiness, seizures, tinnitus, tremors, confusion, coma
Cardiovascular - bradycardia, hypotension, VF, asystole
How would you manage a patient with lidocaine toxicity?
ALS approach
Primarily supportive
Seizure control with diazepam / midazlolam (phenytoin ineffective).
Cardiac monitoring
Which local anaesthetic is used in haematoma blocks?
Plain prilocaine, no adrenaline.
- undergoes faster hepatic metabolism and has lower direct neurotoxicity
- can cause methaemoglobinaemia
What are the safe maximum doses of local anaesthetic?
Lidocaine: 3mg/kg (7mg/kg with adrenaline)
Bupivacaine: 2mg/kg (3mg/kg with adrenaline)
What are the potential complications of spinal anaesthetics?
Hypotension & urinary retention
- During insertion: direct neural injury, bleeding, haematoma, headaches
- Due to catheter: block, dislodgement, infection, chronic fibrosis
- During removal: haematoma, cord compression & paralysis. Anti-coags should be stopped prior to removal.
What is a burn injury?
Jackson’s burn model describes burns as ‘tri-zone injuries’
- central area of coagulative necrosis
- surrounded by static area of inflammation and ischaemia
- further encircled by an area of hyperaemia
How would you classify burn injuries?
Depth: superficial, partial thickness, full thickeness
Cause: flash/flame, contact (hot/cold), friction, chemical, electrical, radiation
How do you assess burn size?
- Patient’s palm ~1% TBSA
- Wallace’s rule of nines: adult, head 9%, arm 9%, ant leg 9%, post leg 9%, ant trunk 18%, post trunk 18%, perineum 1%
- Lund & Browder Chart: most accurate, adjusted for age
What fluid regime would you use to treat a burn injury?
Parkland formula = %TBSA x weight (kg) x 4ml in 24 hrs, first 50% given in first 8 hours post burn injury.
Required for adults with TBSA >15% or children with TBSA >10%
Which burns injuries should be referred to a burns unit?
- full thickness TBSA >5%
- partial thickness TBSA >10% in pts <10 or >50yrs
- face, eyes, ears, hands, feet, genitalia & perineum
- joints
- inhalation, chemical and electrical
- circumferential
Prognosis of burns patients?
Bull Chart estimates chance of survival based on age and %TBSA.
If patients age + %TBSA >100 survival is poor ~20%
How is a CVP line used to measure left atrial pressure?
Line inserted into SVC / right atrium to record right atrial pressure
- assumed to be equal to left atrial pressure
- if sides are asynchronous the assumption is no longer valid
How does cardiopulmonary bypass work?
- right atrium cannula insertion
- gravitational drainage of venous blood into reservoir
- blood heparinisation
- membrane oxygenator add O2 and removes CO2
- heat exchanger controls blood temperature
- oxygenated blood is passed through a bubble trap and microemboli filter
- blood is returned to aortic circulation
What are the clinical indications for cardiopulmonary bypass?
- Cardiothoracic surgery e.g. aortic surgery, CABG, valve repair / replacement, lung transplant, pulmonary thrombectomy
- Neurosurgery e.g. basilar artery aneurysm repair
- Supportive (critically ill pts) e.g. drug overdose, hypothermia
What are the complications of cardiopulmonary bypass?
- immediate: air embolism, coagulopathy, hypothermia, inflammatory response, thrombocytopenia
- early: ARDS, arrhythmia, AKI
- late: coma, focal neurological deficit, mesenteric ischaemia, pancreatitis, seizures
What is the difference between primary and secondary brain injury?
Primary: occurs at time of injury e.g. direct brain cortex injury
Secondary: occurs after the injury, may be due to:
- Hypoxia
- Hypotension
- Hypercarbia
- High ICP
What is the Monro-Kellie doctrine?
Describes the intracranial pressure-volumes relationship as governed by: brain tissue, blood & CSF within a closed rigid box of fixe volume.
Change in 1 component must result in a compensatory change in another component in order to prevent a rise in ICP
What are the causes of increased intracranial pressure?
- Medical: electrolyte imbalance, infection, stroke
- Surgical: haemorrhage / haematoma, oedema (contusions & DAI), tumour
What is the cerebral perfusion pressure?
CPP = MAP - ICP
It is the pressure gradient which drives cerebral blood flow, O2 delivery and metabolite clearance.
What are the key constituents of TPN?
- carbohydrates >50%
- fat >30%
- amino acids
- water
- electrolytes
- trace elements
- vitamins
Define acute and chronic renal failure
- Acute: sudden, usually reversible impairment of functioning nephrons, resulting in reversible (usually) kidney function impairment
- Chronic: progressive, permanent loss of functioning nephrons, resulting in irreversible kidney function impairment. CRF = advanced stage 4/5 CKD
How is renal failure classified?
Pre-renal
- hypovolaemia (inadequate fluids, haemorrhage, burns, D&V)
- decreased cardiac output (HF, PE)
- hypotension (sepsis, anaphylaxis)
- vascular (renal artery or vein obstruction)
Intrinsic renal
- Drugs (gentamicin, NSAIDs)
- Glomerular (glomerulonephritis, antibody-mediated)
- Interstitial (pyelonephritis, sarcoid, lupus)
Post-renal (calculus, carcinoma for all)
- Ureteric
- Cystic
- Prostatic (BPH)
- Urethral (blocked catheter, stricture)
What are the types of renal replacement therapy?
- haemodialysis (works by diffusion)
- haemofiltration (works by convection)
- haemodiafiltration (combination of above)
- peritoneal dialysis
