Good morning and welcome to your Wednesday dose of Your Daily Meds.
Bonus Review: At what level in the body does control of iron stores occur?
Answer: Control of iron in the body occurs at the level of the small bowel mucosal cells. These enterocytes are responsible for the control of iron absorption.
* When body iron stores are low - plasma transferrin is high, its iron saturation is low, more iron passes from ferritin in the eneterocytes to transferrin in blood
* When body iron stores are adequate - transferin saturation is higher, the iron remains in the enterocyte and the unwanted iron is lost from the available absorption pool when the enterocyte is shed
* Remember that iron is readily absorbed by these enterocytes, but the absorption across the enterocyte basal membrane is regulated by levels of ferritin and transferrin and transferrin saturation.
* If we overload this mucosal block with excessive iron supplementation, we will absorb excess iron
* Or if the function of the control mechanism is defective, such as in haemochromatosis, we will be overloaded with iron, resulting in iron deposition in the tissues
Case:
A 45-year-old male is brought to the Emergency Department by ambulance.
On examination, he has a temperature of 38.2°C and is agitated.
There is tremor, muscle rigidity and a marked deep tendon hyperreflexia of the lower limbs more so than the upper limbs.
His pupils are dilated and mucus membranes dry.
Relatives at his home informed the paramedics that he has a history of depression for which he is known to a Psychiatrist.
Which of the following is the most likely diagnosis?
* Serotonin syndrome
* Neuroleptic malignant syndrome
* Malignant hyperthermia
* Sympathomimetic toxicity
* Seizure
Have a think.
Scroll for the chat.
Procedure:
Alright then.
As if in an OSCE situation, tell me how you would approach, prepare for and conduct the ‘procedure’ of local anaesthetic infiltration.
Have a think.
Jot some things down.
Scroll for the chat.
The Syndrome:
This man has signs suggestive of serotonin syndrome.
Serotonin syndrome can be a life-threatening condition with increased serotonergic activity in the central nervous system. It can be caused by therapeutic medication use, interactions between medications and intentional overdose. Classically, serotonin syndrome is a clinical diagnosis of mental status changes, autonomic hyperactivity and neuromuscular abnormalities. In this case, serotonin syndrome is manifested by hyperthermia, agitation, muscular rigidity and hyperreflexia, along with the history of antidepressant use. Common antidepressants like Sertraline are Selective Serotonin Reuptake Inhibitors (SSRIs), which increase the extracellular levels of serotonin and serotonergic neurotransmission in the brain.
Neuroleptic malignant syndrome is a life-threatening neurological emergency associated with the use of neuroleptic medication. It is characterised by mental status change, rigidity, fever and dysautonomia. In this case, the physical signs more prominent in the lower limbs and the associated SSRI usage are more suggestive of serotonin syndrome.
Malignant hyperthermia is characterised by hypermetabolic crisis when a susceptible individual is exposed to a volatile anaesthetic agent, which is unlikely given the history in this case.
Sympathomimetic toxicity is manifested by stimulation of alpha- and beta-adrenergic receptors and characterised by typical adrenergic signs and symptoms, including hyperthermia, tachycardia, diaphoresis, hypertension and cardiac arrhythmias. Sympathomimetic toxicity can be caused by prescribed and non-prescribed substances, such as ecstasy.
Seizure is unlikely given the autonomic changes and neuromuscular abnormalities in this patient.
Infiltration:
Ok, so lets start with Indications:
* Local anaesthesia (LA) for painful procedures eg
* Suturing
* Debridement of wound
* Foreign body removal
* Reduction of disclocated small joint
* Arterial puncture
Then some Contraindications:
* Local anaesthetic allergy - rare
* Avoid lignocaine with adrenaline in areas of end-arterial supply eg:
* Fingers
* Toes
* Penis
* Pinna
* Nose
* (Even though amputated digits can be reattached (after a period of literally zero blood supply) and adrenaline is used in local anaesthetics for digital blocks of fingers and toes… best stick to the safe answer in the test…)
Equipment:
* Alcohol swab
* Skin cleansing solution eg some chlorhexidine
* Local Anaesthetic agent of choice
* Syringe: 5mL or 10mL
* Needle: 25G and 21G
Choice:
* Small volumes of concentrated anaesthetic for small areas or joints
* Large volumes of less concentrated anaesthetic for large areas or joints
* Select adrenaline-containing anaesthetic for vascular sites - causes vasoconstriction
* Likely help reduce bleeding
* Reduce systemic absorption of lignocaine
* Maintain higher anaesthetic concentration near nerve fibres
* Prolong local anaesthetic conduction blockade
* Lignocaine is most commonly used
* Bupivacaine and Ropivacaine are longer acting, usually used for nerve blocks or epidurals
Calculate:
Maximum safe dose of your chosen agent:
* Lignocaine - Max dose 3mg/kg - Duration 0.5-1 hour
* Lignocaine with adrenaline - Max dose 7mg/kg - Duration 2-5 hours
This means you will need to do some maths to work out how many mL of a particular % concentration lignocaine +/- adrenaline you can safely inject.
Just make sure you calculate your maximum mg for the particular patient FIRST, then work out the mL from the bottle SECOND.
Procedure:
* Consent, explain procedure blah blah blah
* Clean the site
* Recheck dose, safe maximum, dilution, allergies etc
* Draw LA into syringe with 25G needle
* Enter dermis of skin at 45deg, aspirate to ensure needle not in blood vessel
* Infiltrate 1-2mL of LA to make a bleb
* Exchange 25G for 21G needle
* Enter skin through previously anaesthetised bleb site
* Advance subcutaneously, aspirate and inject
* Repeat: Advance, aspirate, inject
* If you aspirate blood, withdraw a bit, aspirate then inject and continue
* Repeat such that the desired area is infiltrated with LA
* Wait at least two minutes to take effect
Then get on to cutting or suturing or realigning or whatever.
Bonus: How is iron carried (or transferred) in the blood?
Answer in tomorrow’s dose.
Closing:
Thank you for taking your Meds and we will see you tomorrow for your MANE dose. As always, please contact us with any questions, concerns, tips or suggestions. Have a great day!
Luke.
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