Transcript ASTHMA MANAGEMENT

Safe Prescribing
Week 3 – Amino
glycosides + electrolytes
Dr Ian Coombes,
Senior Clinical Lecturer University of Queensland
Schools of Medicine and Pharmacy
Safe Medication Practice Unit, Queensland Health
The University of Queensland
Objectives
• Principles of once daily
Aminoglycoside dosing and avoiding
toxicity
• Key messages about analgesia use
Gentamicin Revision
• Gram negative bactericidal agent
• Excellent anti-pseudomonal cover
• Once daily dosing benefits vs tds or bd:
- high peak level – excellent distribution
- post antibiotic effect (>24-36 hours)
- reduced monitoring and administration
- reduced nephro and ototoxicity
- easier monitoring (10-12 hours post dose)
Severe risks of nephrotoxicity and
ototoxicity
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Mrs HR
78 years, wt 57kg
Admitted to outlying hospital acute exacerbation COPD
Baseline Cr 80mol/L
Charted gentamicin 160mg daily for 5/7
CrCl = 45ml/min
Date
3/6
5/6
6/6
7/6
8/6
9/6
10/6
11/6
12/6
13/6
14/6
15/6
16/6
17/6
Gent Dose
160mg
160mg
160mg
160mg
160mg
ceased
Level
Cr
0.08
Urea
8.5
15.5
6.2
9.0
0.11
0.13
0.17
16.9
0.22
28.3
7.8
0.36
0.39
0.41
0.50
0.59
0.65
35.0
21.9
33.6
38.9
40.6
• 21/6 Gent level still 1.4!!!!
• 23/6 complaining of dizziness, unsteady
feeling, vestibular symptoms, vomiting
• 1/7 Cr 0.21 recovering
Aminoglycoside dosing and Monitoring
Case continued…
Day 3:
• Mr AD (67yrs) has now developed sever hospital acquired
pneumonia
• Ward round decisions
- start gentamicin once a day
 dose as per levels each night at 20:00
 recall patient weighs 70 kg
 creatinine has improved (now 140 micro mole/l)
- start Co-Amoxiclav 1.2g IV q8h
Creatinine Clearance
• Do NOT use eGFR provided by AusLab
(calculated using standard 70 kg patient  can lead to over-dosing)
• Recall Cockcroft-Gault Formula:
CrCl (mL/min) = [140-age (years)] * ideal weight (kg)
[0.814 * serum creatinine
(micromol/L)]
{♀ * 0.85 }
If patient 70 kg, 67 y.o. with serum creat~140micromol/L:
CrCl ≈ 42 mL/min (140-67 X 70) / (0.814 x 140)
Calculating first dose gent
Gentamicin Dose Adjustment
Day 4:
 gentamicin level = 2.5
(taken 08:00, 12 hrs post dose)
• The initial dose given in emergency department
was 280mg (4mg/kg x approx 70kg)
Prescribe new gentamicin dose based on level
2.5
Adjusting doses of gentamicin
Gentamicin Dose Adjustment
• Level at 12 hours = 2.5 (ideal = < 2)
• New Dose =
Level Wanted (mg/L) x Dose Given (mg)
Level Achieved (mg/L)
In this case: (1.5/2.5) x 280 = 168 mg
• round down to 160 (nearest multiple of 40 mg)
- amps = 40 mg/mL
When NOT to take levels
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Do not take levels if:
Stat dose
Or
Patient has Normal renal function and is only
receiving 1 or 2 doses ie prophylactic
Variable Dose Medication
Drug Level and Time Taken
Dose Time and Actual Time Given
Use in moderate to sever renal
function
• Where ever possible withhold other
nephrotoxic drugs and ensure no other
altenative
• Ie unavoidable use of gentamicin:
• Requires extended dose intervals 36, 48 or 96
hours
• Effectively daily levels wait til < 1.0mmol/l
then dose again
Gentamicin FAQs
• Patient returns from OT, septic, at 4 p.m.?
- dose now
- get level 8 a.m. (difficult to get bloods during night)
 if level < 0.5, clearance satisfactory
• Patient in ED at 4 a.m. with severe pneumonia?
- give standard dose now; dose again at 8 p.m.
• Level low but adequate dose? (patient ok clinically)
- dose 4-5mg/kg has long post antibiotic effect
- don’t increase
• If in doubt, CHECK!
- Registrar; clinicial pharmacists; ID team
Gentamicin Ordering key messages
• If elderly (renal impaired) is there an alternative safer drug?
• Do not write as a regular medication – prescribe dose for regular
dosing after levels available
• Dose according to gentamicin level
• Use aminoglycoside dosing guides
- these notes www.wiki.tox.org.2.17 safe prescribing
• Try to prescribe in multiples of 40mg (ampoule contains
80mg/2mL = 40mg/mL)
• Where possible, dose at a time that allows level to be taken on
next day’s blood round
Questions?
Introduction to Prescribing
Analgesia and Pain Relief
Presented by: [insert presenter name here]
You have been asked to write up a
patient’s analgesia…
What patient factors do you need
to consider?
Patient Assessment
Goal to individualise analgesic therapy
Assess patient characteristics:
- indication for analgesia
- age, sex, weight
- culture
- vital signs
- allergies/ADRs
- opioid tolerance
- respiratory status
- renal/hepatic function
- other medical co-morbidities
- mental state
- other Rx
- availability of oral/rectal routes
WHO Analgesic Ladder
(ideally fro chronic pain)
Level 1: Non opioid/adjuvant
(paracetamol; NSAIDs; amitriptyline; local anaesthetics)
Level 2: Weak opioid + non-opioid
Level 3: Strong opioid +/- non-opioid/adjuvant
1 2 3
NOT ACCEPTED- Use Multimodal Analgesia
DRUGS
Nociceptive
e.g. fracture
Paracetamol Effective when
taken regularly
at max. dose
Opioids
Effective
PAIN TYPE
Neuropathic Inflammatory
eg neuralgia
e.g. rheumatoid
arthritis
Less effective Effective, but not
anti-inflammatory
May be
May be effective
effective
(depends on
(agent + dose) dose)
NSAIDs
Effective
Not effective
Effective
TCAs,
parenteral,
local
anaesthetics
antiepileptic
Rarely used
(clonidine may
be effective as
adjunct)
May be
effective
Rarely used (may
be effective as
adjunct)
Adapted from Table 3-1, Australian Medicines Handbook
NSAIDs- Adverse Effects
Side effects
• hypersensitivity/allergy
• GI (GORD/PUD)
• platelet inhibition
• sodium retention, oedema
• renal toxicity
• hepatic toxicity
Cautions
NSAIDs- Adverse Effects
Side effects
Cautions
• hypersensitivity/allergy
- asthma
• GI (GORD/PUD)
- GI bleeding/ulceration
• platelet inhibition
- coagulation disorders
- warfarin therapy
• sodium retention, oedema - hypertension
- cardiac failure
- ACEI/ARA/diuretics
• renal toxicity
- renal impairment
- gentamicin therapy
• hepatic toxicity
- hepatic impairment
NSAIDs – Caution!
Major cause of ADEs and hospital admissions
 use lowest effective dose for shortest possible time
 use paracetamol as alternative or to reduce NSAID dose
 COX-2 inhibitors
- similar adverse effects to non-selective
- increase risk of thrombotic events (stroke; MI)!
 little difference in efficacy between NSAIDs
 avoid aspirin < 18 yrs in viral illness (Reye’s syndrome)
 elderly - increased risk of adverse effects
Continue only if effective. Avoid if possible!
Potential Adverse Effects of
Opioids?
Opioids – Adverse Effects
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respiratory depression
sedation
nausea and vomiting
confusion
hypotension; bradycardia
pruritus
constipation / ∆ gut motility
urinary retention
Opioids – Precautions
 hypotension, shock
 concomitant CNS depression
 impaired respiration /↓ respiratory reserve
 elderly
 hepatic impairment
 renal impairment
 epilepsy/recognised seizure risk
 biliary colic or surgery
 phaeochromocytoma
Regular vs PRN Analgesia
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regular analgesia is better in setting of continuous pain
PRN only if pain intermittent and unpredictable
in most settings, pain is predictable
problems with using only PRN analgesia
- dose prescribed by Dr/administered by nurse
- patients don’t ask for medication
 inadequate or infrequent dosing → unrelieved pain
 keeping up with pain is easier than catching up with pain
 prn dose = 1/6 →1/12 total regular daily dose
Key Messages
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individualise analgesic therapy
choose analgesics judiciously
use multimodal analgesia
regular pain monitoring is critical to outcomes
regularly review and revise analgesic doses
adjust regular dose according to breakthrough usage
anticipate and manage analgesic-associated adverse
events
 avoid NSAIDs – major cause of morbidity/mortality!
 avoid tramadol, dextropropoxyphene, pethidine
Electrolyte Objectives
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Fluid requirements
Common error traps
Electrolyte requirements
Key messages for safe electrolyte
prescribing
Maintenance Fluid for “Standard”
Patient
–70 kg
–euvolaemic
–no electrolyte derangements
–not septic
–normal cardiac and renal function
–no additional ongoing fluid losses
Sodium
Daily Requirement 2 mmol/kg
0.9% NaCl 1L
(Normal Saline) +/- 150 mmol
20/40 mmol KCl/l
4% glucose &
0.18% NaCl 1L
3.3% glucose &
0.3% NaCl +/20/40 mmol KCl 1L
30 mmol
50 mmol
Glucose Potassium
>100G
1 mmol/kg
0
0, 20 or 40
mmol
40G
0
33G
0, 20 or 40
mmol
Risks of Having IV Line
• Infection
– Time and effort to re-site every 48 hours
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Immobility
Thrombophlebitis
Direct costs of consumables
Overdosing of fluids and electrolytes
Key Messages
IV Fluid Ordering
• Supply orally if possible
• Assess current fluid status
- wet / dry / ‘just right’?
- how do you tell?
• Review fluid balance chart
• Assess ongoing requirements and losses
• Reassess fluid status at least daily
Potassium
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What is normal?
Where do you lose it from?
How much do you need?
How can you replace it?
Routes of administration?
How fast can you replace it?
Quantities?
What goes wrong?
Potassium
• Normal serum K+ = 3.8-4.9 mmol/L
• Daily requirement = 1 mmol/kg
• Dietary K+ < 25 mmol (1gram)/day leads to
hypokalaemia
• Is magnesium low (< 0.5 mmol/L)?
(makes it difficult to correct potassium)
Causes of Hypokalaemia
• Potential sites for K+ loss
- urine; faeces; drain sites; vomitus
• Intracellular shifts
-
insulin
β adrenoceptor agonists
caffeine
hyperthyroidism
correction of acidosis
• Increased external losses
- Drugs that promote renal K+ excretion
 loop diuretics (eg frusemide)
 aldosterone; thiazides; penicillins
Potassium Replacement
• There is no single way to correct potassium
• serum K+ of 0.3 mmol/L = overall deficiency
 100 mmol K+ (but extremely variable)
• Replace with oral supplements where possible
• Ideally, correction of potassium should occur over a
period of days
• Account for deficit + ongoing normal requirements
Case Study - Mr KCl
• 72 y.o. ♂
• Med Hx: hypertension, heart failure
• Rx: frusemide 80mg mane; lisinopril 10mg mane;
amlodipine 10mg mane
• Admitted for elective TKR
• Pre-op serum potassium: 2.9 mmol/L
• Registrar:
- “Give him some IV KCl and fluids pre-op”
- suggests 40 mmol in 100mL N Sal over 60 min
- What happened?
Potassium Administration
• In non critical care cases, Should NOT give KCL
> 10 mmol/hour WITHOUT a pump
• With a pump max. rate = 20 mmol/hour
• Concentrations > 40 mmol/L: risk causing
thrombophlebitis, pain and loss of IV site
• If via central line, concentration NOT a concern,
but RATE is!
Causes of Hyperkalaemia
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↓ K+ excretion (renal insufficiency)
↑ K+ intake (but rapid K+ excretion 2o to ↑ intake)
K+ release from cells
Metabolic acidoses
Medications
Hypoaldosteronism/resistance to aldosterone
Managing Hyperkalaemia
– What are your aims?
– What are the risks?
– What do you do?
– How do you do it?
Cardiovascular Protection
Calcium Gluconate by slow IV push
– decreases membrane excitability
– 10 mL of 10% calcium gluconate (2.2 mmol)
– onset 2-5 minutes, lasts up to an hour
– can repeat if no ∆ ECG after 5-10 minutes
Shift Intravascular → Intracellular
• Insulin
- 10 units insulin in 50 mL of 50% glucose
- via syringe or free running drip
- onset 15-30 minutes, lasts 1-3 hours
- ↓ plasma K+ by 0.5-1.5 mmol/L
• Nebulised salbutamol
- 5 mg
- onset within 30 minutes, lasts 2-4 hours
- ↓ plasma K+ by 0.5-1.5 mmol/L
Removing Excess Potassium
• Resonium® A (sodium polystyrene sulfonate)
- promotes exchange of Na+ for K+ in the GIT
- 30g orally or 60g enema mixed with glucose
- onset within 2 hours, peak effect at 6 hours
- 1 gram binds 1 mmol K+ and releases 2-3 mmol Na+
- generally lowers plasma K+ by 0.5-1.0 mmol/L
- can give up to 4 doses per day (as per levels)
• Haemodialysis
- severe life-threatening hyperkalaemia unresponsive
to more conservative measures
Sodium Replacement
• Consider
- ? over filling (heart, renal, liver failure)
- ? over diuresis
- ? SIADH – SSRIs; TCAs; carbamazepine
• Replace Na+ gradually (↑ plasma Na+ by ≤ 10 mmol/L/day)
• Na+ required to ↑ plasma Na+ by 10 mmol/L:
[0.6 * total body weight (kg)] * 10 = x mmol/L Na+
NEVER attempt to replace sodium with hypertonic saline!
- IRREVERSIBLE osmotic demyelination of CNS
(several cases in QLD in recent years)
Magnesium
• Indications
- hypomagnesaemia
- post MI
- antiarrythmic
- acute asthma
- pre-eclampsia
• Oral - limited value (laxative)
• Be aware of IV rate - vasodilator!
Key Messages
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Use oral route for electrolytes if possible
Significant patient harm 2° to rapid/concentrated KCl
K+ reduction - protect heart (short and long term)
NO place for hypertonic saline – demyelenitaion risk
Magnesium used for hypertension
Questions?