pharmacology Flashcards
fluids-
rule of 1/3s
for 70kg patient
TBW 42 L
- intracellular = 2/3 = 28L
- extracellular = 1/3 = 14L
- Interstitial fluid 2/3 of ECF 9L
- Intravascular - 1/3 of ECF 5L
- Interstitial fluid 2/3 of ECF 9L
total blood volumes for:
adults
children
neonates
adults = 70mls/kg children = 80mls/kg neonates = 90mls/kg
define osmolality
osmoles per kg of solvent (usually water)
define osmolarity
osmoles per litre
define tonicity
the ability of a solution to cause water movement
name two types of fluid
crystalloid - better for resus
colloids
what happens if you leave people on just a normal saline drip?
hypernatraemia
hyperchloraemia
acidotic
if you provide someone with glucose what happens to their potassium?
lowers potassium
as when you process the glucose by glycolysis this is co-transported into cells with potassium
so if you give someone shit loads of sugar expect their potassium to decrease
hartmanns/plasmolyte
what is it?
very close ionically to our own plasma so its good
requirements per day of water, sodium, potassium, energy
water - 30mls/kg/day
sodium - 1-2mmols
potassium - 1mmols
energy - 30kcal
if you have a patient that is hypovolaemic, but you are loading them with lots of fluids. what can be the explanation for this?
this is commonly seen in people with pancreatitis and severe illness of any kind.
there is this ‘third space’, so not intracellular not extracellular the fluid is just leaking out and going somewhere else.
if someone is on IV fluids consistently in hospital, how often should they be having a U+E?
at least every 24/hrs if not more!!
normal urine output
0.5ml/kg/hr
fluids formulas for adults
deficit:
4mls/kg/hr up to 10kg
2mls/kg/hr up to 20kg
1mls/kg/hr for rest
maintanence
25–30 ml/kg/day of water and
approximately 1 mmol/kg/day of potassium, sodium and chloride
+ 50-100g/day glucose to prevent starvation ketosis.
so prescribe 25-30ml/kg/day sodium chloride 0.18% in 4% glucose with 27 mmol/l potassium on day 1 for routine maintenance
simple analgesia examples
paracetamol
NSAIDs - ibuprofen
when can you not prescribe paracetamol
hepatic impairment severe cachexia (less than 50kg = max 500mg QDS)
when can you not prescribe NSAIDs
CI - GI bleeds or ulcer history, asthma
- renal impairment and platelet count
- concurrent meds - warfarin, digoxin, steroids
weak opioids
and their problems
codeine
dihydrocodeine
tramadol
problems - ceiling effect, therefore if not working go to stronger opioid not add another weak opioid.
strong opioids
morphine fentanyl diamorphine - IM/IV oxycodone - sibling of morphine - normally better s/e buprenorphine
specialist palliative care only analgesia
hydromorphone
alfentanil
methadone
ketamine
questions to ask patient before starting strong opioid
- every had before? if so what happened?
- renal function - if low egfr then oxycodone NOT morphine
- age/frailty - changes dose
- co-morbidities
- patient concerns
- are they driving?
- will they take them as prescribed?
- have you prescribed medications for any s/e
how potent is codeine/tramadol in comparison to oral morphine
1/10th
if someone was on 60mg QDS of codeine phosphate but this was not managing pain, what would you next prescribe and its dose?
currently on 240mg/24hrs of codeine.
/10 to get same potency in morphine.
= 24mg of morphine
so prescribe 10mg BDS of morphine modified release
if someone was on 100mg QDS of tramadol but not coping, next steps are?
400mg/24 hrs
/10
= 40mg morphine
so prescribe 20mg BD of modified release morphine
modified release analgesia
for background pain acts for 12 hours examples - - morphine = MST (tablet), Zomorph (capsule) - oxycodone = oxycontin
immediate release analgesia
for breakthrough pain
acts for 4 hours
- morphine = ormorph (liquid), sevredol (tablet)
- oxycodone = oxynorm (liquid or capsule)
oxycodone/morphine potency ratio
2/1
how to work out PRN doses
1/6th of 24hr dose.
for example if they are having 60mg/24hrs of morphine.
PRN dose = 10mg
(!!! DONT forget the potency difference between oxycodone/morphine with this though)
s/e of opioid management
antiemetic PRN
laxative - stimulant
opioid s/e
common
less freq
rare
common -
- constipation
- nausea
- sedation
- dry mouth
less frequent
- psychomimetic effects
- confusion
- myoclonus
rare
- allergy
- resp depression
- pruritis
analgesia patches examples, indication and housekeeping
fentanyl
buprenorphine
indication - for stable opioid responsive pain, intolerable s/e, oral route difficulties: compliance/dysphagia, renal impairment
DO NOT USE IN ACUTE PAIN - takes 1-3 days to reach analgesic concentrations
housekeeping -
- hairless, dry, non-inflamed skin
- always check fully adhered on admission/inbetween changes
- avoid heat pads as decrease absorption
potency comparison:
5microgram/hour buprenorphine patch changed every 7 days is equivalent to how much morphine over 24hrs
12mg
what might you prescribe for neuropathic pain?
amitriptylline
duloxetine
pregablin
gabapentin
what might you prescribe for muscle spasms
baclofen
tizinidine
what might you prescribe for compression symptoms?
dexamethasone
what might you prescribe for spasms, ?neuropathic pain
clonazepam
diazepam
what might you prescribe for focal areas of pain
topical lidocaine plasters
what might you prescribe for bone pain?
bisphosphonates
- zolendronic acid
potency comparison -
injectable opioids: oral opioids
2:1
patient is on 50mg BD morphine MR and oramorph 15mg PRN - needing to be converted to syringe driver as of recent swallowing problems. what would you prescribe?
50mg x 2 = 100mg
/2 - as of potency when IV = 50mg SC morphine/24hrs
PRN - 7.5mg SC
if on fentanyl patch and stable and wanting to swap to syringe driver to control pain - what do you do with the patch?
leave it there
what unit must you always prescribe opioids?
mg
nociception nerve fibres -
types
A-delta - myelinated and fast conduction
C - non-myelinated and slow conduction
two tracts involved with pain
dorsal root ganglion - afferent, first order neurons
spinothalamic tract - second order neuros
formula to work out dose in IV infusions
mls/hr x mg/ml
= mg/hr
what is the most common shape for gram positive bacteria?
cocci
what is the most common shape for gram negative bacteria?
bacilli
name an anaerobic gram negative bacilli
bacteroides eg B. fragilis
name the aerobic gram negative bacilli and their growth requirements
lactose fermenters - MacConkey Pink or XLD:
- Escherichia Coli
- Klebsiella pneumoniae
(***on XLD = e.coli yellow colonies, salmonella = black)
non-lactose fermenters - MacConkey pale - salmonella typhi/paratyphi/enterica - shigella sonnei/dysenteriae - proteus mirabilis (***OXIDASE TEST - positive = pseudomonas aerginosa -negative = salmonella, shigella, proteus)
others -
- pseudamonas aeurginosa
- vibrio cholerae
fastidious growth requirements - chocolate agar
- parvobacteria - haemophilus influenzae, bordatella pertussus, legionella pneumophilia, brucella, campylobacter jejuni (grown on CCDA - charcoal plate)
- helicobacter pylori
name the gram neg cocci
neisseria meningitidis
neisseria gonorrhoeae
moraxella catarrhalis
gram positive cocci - pairs/chains
CATALASE NEGATIVE
streptococcus - blood agar used to detect haemolysis, CBA plate
alpha haemolytic - DARK GREEN
- strep pneumoniae - optochin sensitive
- strep oralis
- strep sangius
- strep viridans
- enterococci
beta haemolytic - PALE YELLOW AND TRANSPARENT
- step pyogenes -A
- strep agalactiae - B
non-haemolytic - NO CHANGE
- strep mutans
- strep milleri - lung abscess
- enterococcus faecalis
gram positive cocci - clusters
CATALASE POSITIVE
staphylococcus
coagulase negative - staph epidermis, staph saprophiticus
coagulase positive - staph aureus - lung abscess
mycobacterium TB - staining and growth and cell type
weakly gram positive bacilli
doesnt gram stain well
ACID FAST BACILLI - high lipid content in cell wall
ziehl-neelson stain - stain is coloured red
can also use lowenstein jensen medium - takes 3-8 weeks
b-haemolytic strep groups
group A - pyogenes
B - perinatal
C- bowel/UTI
gram positive bacilli-
anaerobic-
- clostridium perfringens
- c. tetani
- c. botulinium
- c. dificile
aerobic
- cornybacterium diptheriae
- listeria monocytogenes
- bacillus anthracis
- bacillus cereus
the penicillin group - coverage and what are they effective against
penicillin V -
- narrow spec, strep throat, can be added to fluclox in skin infections
amoxicillin - broader than pen v and much better absorption
neuropathic pain ladder
1st line - amitriptyline or pregablin
2nd - amitriptyline + pregab
3rd - refer to pain specialist - give tramadol in the interim (avoid morphine)
what do you prescribe a diabetic if they have neuropathic pain
duloxetine
anaesthetic analgesic ladder
management of acute pain
severe pain to moderate so normally the opposite to WHO ladder
1st - strong analgesic + local anaesthetic block and peripherally acting drug
2ns - restore use of oral route. should be fine with weak opioids + para/ibup
3rd - just para/ibup
WHO analgesic ladder
para/ibup
weak opioid eg codeine
strong opioid eg morphine
if large volumes of 0.9% saline is given what is your patient at risk of and why?
hyperchloraemic metabolic acidosis
saline causes a overload of chloride ions into the blood which forces bicarb to move intracellularly to maintain ionic equilibrium, thus reducing the available bicarbonate for the pH buffering system leading to net acidosis.
when should Hartmann’s NOT be used
in patients with hyperkalaemia as it contains potassium!!!
when is hartmans preferred to be used
after surgery
what is not recommended for post surgery patients for fluid replacement
5% dextrose and dextrose/saline combs
if you have a patient who is oedematous but also hypovolaemic what do you do
hypovolaemia should be treated first
followed by a negative fluid balance (higher UO than input fluids) monitored using Na excretion levels.
however solutions such as dextran 70 should be used in caution in patients with sepsis as there is a risk of AKI
what is a crystalloid fluid?
what is colloid fluid?
crystalloid - solutions of small molecules in water (eg nacl, hartmann’s, dextrose)
colloid - larger organic molecules (eg albumin, gelofusine). they carry a risk of anaphylaxis and research has shown that crystalloids are superior in initial fluid resus
describe the tonicity of each of these fluids: NaCl hartmanns NaCl 0.18%/ glucose 4% 5% dextrose
NaCl - isotonic (used for resus)
hartmanns - isotonic (used for resus)
NaCl 0.18%/ glucose 4% - hypotonic
5% dextrose - hypotonic
what does hypotonic fluid mean
less fluid, salt, sug than blood
what does isotonic fluid mean
similar fluid, salt, sug than blood
assessing a patient for fluid prescription
look at fluid chart - input/output
ask nurses about - vom/diarrhoea
check for any drains
co-morbs? heart/renal failure
aims of initial evaluation of trauma
aims:
- stabilise
- identify life-threatening conditions in order of risk and initiate supportive treatment
- organise definitive treatments or transfer for it
trauma a-e
prep!!
- airway equip - laryngoscopes
- IV fluids + warming equip
- monitoring equip
- methods of summoning extra medical help
- prompt labs and radiology backup
- transfer arrangements with trauma centre
CABCDE
trauma a-e
prep
prep!!
- airway equip - laryngoscopes
- IV fluids + warming equip
- monitoring equip
- methods of summoning extra medical help
- prompt labs and radiology backup
- transfer arrangements with trauma centre
TTBTO - turn the blood tap off - if an obvious massive haemorrhage sort that first (ie squirting) - direct manual pressure
C - cpsine immobilise - then follow ABCDE as normal, except:
A - will probs need to intubate
B- more important to get full vision of chest to chest for trauma think about potential: - tension pneumo - flail chest - haemothorax
C - see rest on A+E notes
when to expect electrolyte changes in fluid losses and therefore need to alter fluid replacement regime
vomiting NG tube diarrhoea/excess colostomy loss jujenal loss high vol ileal loss via new stoma lower vol ileal loss via established stoma or fistula pancreatic drain or fistula loss bilary drainage loss inapprop urinary loss (monitor elec closely as can be highly variable)
if you suspect any electrolyte losses then which is the best solution to give in hypovolaemia in a bolus
hartmanns - as will replace them
when do you stop giving boluses to someone in an emergency
when you reach 2000mls
if reach this and not better - SENIOR HELP
which compartment are fluids put into?
intravascular
however certain amount will be redistributed across all compartments depending on their osmotic gradient
hierarchy of how long IV fluids stay intravascularly before being redistributed into other compartments (longest -> shortest)
colloids saline hartmanns dex-saline dex
when would you give 5% dextrose? and why is it bad?
if just need to give pure water and they cannot swallow - as glucose is just used up
bad - resus, too much too quick = hyponatraemia
good/bad things about normal saline
can add 20-40mmol KCl per 1L bag
good as maintainence - alternate with 5% dex in those with normal electrolytes (1 salty + 2 sweet)
bad
hypernatraemia
using it alone without alternating with dex can be renotoxic - massive sodium load on kidneys causing renal vasoconstriction
give hyperchloraemic acidosis
good/ bad about hartmanns
good - anaesthetics choice, excellent to replace plasma during GI losses/surg
bad - shouldnt be used as maintanence alone as will give 3x too much sodium and not enough pot
- cannot add extra pot or mag to bag
what causes electrolyte loss
D+V NG aspirate stoma burn pancreatitis
dehydration loss and its replacement
caused by pyrexia + poor intake
replace with dex-saline
what does raised creat + urea indicate when there has been fluid losses
dehydration
urea will rise first
the classic fluids prescribed for a 70kg man maintenance
CHECK U+E FIRST!!!
saline 0.9% + 20mmol KCl over 8 hours
dextrose 5% +20mmol KCl over 8 hours
(repeat this for last 8 hours)
why does potassium increase post surg
cell lysis
as potassium is intracellular
whats first line choice fluids post-op if no electrolyte imbalances
sodium retaining mechanisms are activated in surg so dex-saline is best choice
if patient can drink just let them dont prescribe
first line fluid replacement choice in sepsis
hartmanns
as capillary vasodilation and leakiness causes intravascular depletion
heart failure fluid requirements
NO MORE THAN 2L/24 hrs - aka no more than 2 bags per day
overloaded? furose + max 1.5l per day (try oral) + low sodium diet + daily weights (1kg less = 1L lost)
you have a patient that had low systolic BP + low UO but is at risk of LVF -
what two clinical pictures can cause this?
dehydration
LVF + overload: LVF causes low SBP, hence low UO - rx = furose which improves LVF and hence paradoxically increase SBP and UO
fluid losses in liver failure patient - choice of fluid and why?
5% dex
as excess sodium causes ascites
fluid choice in AKI
no potassium supplementation
fluid choice in hx of alc excess/ poor nutrition
give pabrinex before giving 5% dex, even if hypoglycaemic or the glucose load may precipitate korsakoffs syndrome
fluid replacement in brain haemorrhage
avoid dex - can worsen oedema due to osmotic shifts
saline would be a good first choice
fluid replacement in risk of refeeding syndrome
avoid dex and can precipitate
may have hypomag/kal/phos so these will need replacing
(on placement we gave phosphate polyfuser and the rest sorted itself out??)
what are the average insensible fluid losses from a person on a normal day
500-800mls
What largely determines the movement of water between intra and extracellular compartments
sodium
what is high/low electrolyte wise in intra/extracellular compartments
what maintains this gradient?
intracellular - potassium high, sodium low
(these solute concentrations remain more or less constant)
extracellular - sodium high, potassium low
gradient maintained by sodium-potassium ATPase pump
what is the main process called that drives water across membranes and explain it
name another force that can act on this water movement gradient and when this can come into affect
osmosis
this pressure is provided mainly by large molecular weight particles eg proteins.
in a normal healthy individual there are more proteins in intravascular space rather than interstitial fluid
another force-
hydrostatic pressure gradient
this can be affected by circ probs and pressure in tissues such as oedema, mech restriction such as with infection, plaster casts and bandaging
why add in glucose to fluids?
to limit starvation ketosis
what may cause an increase in insensible losses of fluid
sweating
tachypnoeic
febrile
open cavity surg
which electrolytes are lost when you sweat
sodium
which electrolytes are lost when you have diarrhoes/increased stoma output
sodium/potassium/bicarb
which electrolytes are lost when you vomit and what may it lead to if excessive
k
cl
hydrogen ions
this may lead to hypochloraemic metabolic alkalosis, sometimes also mild hypokalaemia
what are insensible losses normally made up of (fluid/electrolyte)
pure water
how many grams of glucose are in IL bag of 5% dextrose
50g
what is the checklist of things you need to check before prescribing fluids
type of fluid loss renal function cardiac function concomittant electrolyte abnormalities BP CRT fluid balance charts skin turgor weight med review - diuretics?
what is a hypertonic solution + examples
they increase plasma tonicity and draw fluid out of cells
sodium chloride 3%
mannitol
if you give NaCl 0.9% what % of that will go into the interstitial fluid and how much intracellular from intravascular
BAZINGA nothing into intravasc as its isotonic with plasma
75% will go interstitial
where does 5% dex distribute to
follows normal water
so for example if you put 1000mls into intravascular space only 80ml will stay there
examples of colloids
blood dextrans gelatin - gelofusine human albumin solution hydroxyethyl starch
draw fluid across capillary border from interstital space to intravascular compartment
what other abx has a cross over with penicillin?
cephalosporin by 20%
what do you have to think about when prescribing for the elderly
decrease in metabolism - renal impairment/liver
polypharmacy
potentially more serious outcomes of adverse events from prescribing
things that cause worsening AKI - pharmacological
loop diuretics
ACEi
what drugs are affected by CYP450 enzyme in liver?
bhjbk
what drugs cause enzyme induction?
aka reduce drug concs PC BRAS
P - phenytoin
C - carbamazepine
B- barbituates
R - rifampicin - interaction with methadone 33-66% reduction after just one dose
A - alcohol (chronic excess)
S - sulphonylureas
what drugs cause enzyme inhibition (CYP450)?
aka increase drug concs
AO DEVICES
A - allopurinol, azole antifungals
O - omeprazole
D- disulfiram E - eryhtromycin V - valporate I - isoniazid C - ciprofloxacin E - ethanol (acute intox) S - sulphonylureas
macrolide inhibitor - clarithromycin is a p glycoprotein inhibitor (eg statins with this)
classic situ - person on warfarin started on erythromycin and can cause a massive rise in INR. warfarin needs to be reduced in this case
what is a narrow therapeutic index drug?
drugs in which the effective therapeutic conc is close to or exceeds the toxic conc
small changes in drug level can result in significant toxic effect
level monitoring eg aminoglycosides, phenytoin, lithium, warfarin
what does smoking do to drugs?
enzyme inducer
what drugs should definitely not be stopped for surgery
CCB
BB
drugs to be stopped for surg
I LACK OP
Insulin - variable stopping (look at local policy)
Lithium - day before
Anticoags/antiplatelets - variable stopping (local pol)
COCP/HRT - stop 4 weeks before
K-sparing diuretics - day of
Oral hypoglycaemics - local pol
Perindopril and other ACEi - day of
drugs to change around the time of surgery
?long term pred have adrenal atrophy - unable to cope with physiological stress response to surg = profound hypotension if theyre stopped.
as with ‘sick day rules’ where patients double their dose when ill, at induction of anaesthesia pts given IV steroids to prevent this
how do acei cause a cough and hyperkalaemia
cough - accumulation of bradykinin
hyperkalaemia - reduced aldosterone production
how does ibuprofen cause renal failure and gastric probs
inhibits prostaglandin synthesis which is needed for gastic mucosal protection + also reduces renal art diamter = renal hypoperfusion + function
what drugs are notorious for causing confusion in elderly
tramadol
cyclizine
diazepam
what should never be paired with a BB
CCB
risk of asystole
type 1 allergic reaction
itching urticaria hypotension angioedema wheeze
patient follow up requirements after severe anaphylactic shock
pred 3days non-sed antihistamine for 3 days issue medical alert band document communicatw with GP advise of what drugs they need to avoid provide written info on this to patinet prescribe 2 x adrenaline auto-injector for self-admin only refer to specialist centre for possible ix into -> all severe reactions, gen anaesthetic.
explain how when a patient following an AKI can then suddenly start to have low pot/sodium on U+Es and high urine output following aggressive fluid management?
they sometimes follow a phenomena called polyuric phase - can cause urine output >200mls/hr - leads to dehydration again
general input should match output so with treatment regimes follow that - choice should be guided by patients abnormal electrolytes
