Exam 1 - Preop Medications Flashcards
1
Q
Where is histamine released from?
A
Basophils and mast cells
2
Q
What 3 things does histamine release cause?
A
- Contractions of airway smooth muscle
- Gastric acid secretion
- Release of NT in the CNS (ACh, norepinephrine, and serotonin)
3
Q
What 4 drugs mentioned in lecture induce histamine release as a side effect?
A
- Morphine
- Mivacurium (Mivacron)
- Protamine
- Atracurium (Tracrium)
4
Q
What other receptors can histmaine activate at H1 and H2?
A
H1
- muscarinc, cholinergic, 5HT3, and ⍺-adrenergic
H2
- 5HT3 and β1
5
Q
What are the effects of histamine on the H1 receptor?
A
Inflammatory pain, hyperalgesia, and allergic rhino-conjunctivitis symptoms
6
Q
What are the effects of histamine on the H2 receptor?
A
- ↑ cAMP (β1-like stimulation)
- ↑ gastric acid and volume
7
Q
What are the systemic effects from both H1 and H2 stimulation?
A
- Hypotension from NO release
- Capillary permeability
- Flushing
- Prostacyclin release
8
Q
How do histamine antagonists interact with the receptor?
A
- Inverse agonists; cause reversal of symptoms
- Don’t prevent the release of histamine
9
Q
Where are H1 receptors found?
A
- Vestibular system
- Airway smooth muscle
- Cardiac enodthelial cells
10
Q
What caution should you have for anyone receiving H1 antagonists, especially ambulatory or elderly patients?
A
H1 antagonist cross the BBB and cause sedation
11
Q
What are the 2 H1 antagonist given pre-op?
A
- Diphenhydramine (Benadryl)
- Promethazine (Phenergan)
12
Q
Why are second generation H1 antagonists sometimes preferred?
Examples?
A
- Do not cross the BBB, less sedation
- Cetirizine (Zyrtec)
- Loratadine (Claritin)
13
Q
What are the common side effects of H1 antagonists?
A
- Anticholinergic symptoms (blurred vision, urinary retention, dry mouth)
- Drowsiness (1st generation)
14
Q
What is the primary indication for diphenhydramine pre-op?
A
- Used as an antipruritic
- Pre-treatment of known allergies
- Anaphylaxis
15
Q
What is the dose and elimination 1/2 time for Benadryl?
A
Dose: 25-50 mg IV (can give less)
E 1/2 time: 7-12 hrs
16
Q
What are the eye and lung effects of diphenhydramine?
A
- Inhibits afferent arc of oculo-emetic reflex
- Stimluates ventilation by augmenting the relationship of hypoxic and hypercarbic drives
17
Q
What is the pre-op use of promethazine?
A
- Anti-emetic
- Reduces peripheral pain levels via anti-inflammatory effects
18
Q
What is the dose and E1/2 time for phenergan?
A
Dose: 12.5 - 25 mg IV
E 1/2 time: 9 - 16 hours
19
Q
Why is there a black box warning for promethazine (phenergan)?
A
- Fatal bronchospasms in children less than 2
- Causes tissue ischemia if infiltrated
20
Q
What is the primary use for H2 antagonists
A
- Used for duodenal ulcer disease and GERD
- Decreases hypersecretion of gastric fluid
- ↓ Gastric volume, ↑ pH
21
Q
What is an adverse effect caused by prolonged administration of H2 antagonists?
A
Gastric mucosa becomes weakened from bacteria leading to increased lung infections and candida albicans
22
Q
What renal side effects could you see with H2 antagonists?
A
↑ serum creatinine by 15% d/t competition for tubular secretion
23
Q
What are the 3 examples of H2 receptor antagonists?
A
Cimetidine (Tagamet)
Rantidine (Zantac)
Famotidine (Pepcid)
24
Q
What is the dose for cimetidine?
A
150-300 mg IV
1/2 dose if renally impaired
25
Which H2 antagonist effects CYP the most?
What drugs are affected?
- Cimetidine, stongly inhibits CYP450
- warfarin, phenytoin, lidocaine, tricyclics, propranolol, nifedipine, meperidine, diazepam
26
What are the adverse effects of tagamet?
- Bradycardia and hypotension with rapid infusion from cardiac H2 receptors
- Increases prolactin levels
- Prevents dihydrotestosterone from binding to androgen receptors leading to male impotence
27
What is the dose for ranitidine (Zantac)?
50 mg diluted to 20 mL over 2 mins
1/2 dose for renal impairment
28
What is the dosing for pepcid?
20 mg IV
1/2 dose for renal impairment
29
Which H2 antagonists is the most potent with the longest half life?
Famotidine (2.5-4 hrs)
30
Which H2 antagonist would you avoid in patients with bone disorders?
Famotidine - interferes with phosphate absorption causing hypophosphatemia
31
What is the MOA of PPIs?
Inhibits movement of protons in gastric parietal cells - only works on currently active pumps
32
What are the time considerations for PPI's?
Can take up to 5 days to have onset
Not much effectiveness in same day cases
33
What situations are H2 antagonists perferred over PPI's?
- Aspiration pneumonitits concerns
- Symptoms are intermittent
34
What are the adverse effects of PPI use?
* SLE
* Fractures
* C diff
* Blocks enzyme that activates clopidogrel
* Inhibits metabolism of warfarin, antifungals, antibiotics, and antiseizures
35
What is the naming convention for PPIs?
-prazole
36
What is the adsorption for omeprazole (prilosec)?
Prodrug - pronates in parietal cells to active form
37
What is the dosing for omeprazole?
40 mg in 100 mL over 30 mins
PO > 3 hrs before surgery
38
Which PPI crosses the BBB and can cause side effects?
Omeprazole (Prilosec)
39
What are PPIs most effective for?
Decreasing gastric volume and controlling acidity
40
Which PPI can begin to start working as soon as 1 hour?
Pantoprazole, although probably not effective enough to prevent aspiration prior to surgery
41
What is the dosing for pantoprazole?
40 mg in 100 mL over 2-15 mins
42
What type of antacid would we never give pre-op?
Why?
Particulate (aluminum/magnesium based)
Would be worse if aspirated
43
What are the concerns for long term use of antacids?
Prolonged increase in gastric pH prevents food breakdown and can cause bacterial overgrowth
44
What concerns are there with magnesium, calcium, and sodium based antacids?
Mangesium - can cause neurological impairment from hypermagnesemia
Calcium - can cause kidney stones from hypercalcemia
Sodium - increases fluid retention causing hypertension
45
Which patients do we always give sodium citrate (Bicitra)?
C sections
46
Why do we give Bicitra to surgical patients?
It works immediately to neutralize stomach acid to protect against aspiration pneumonitis
47
What is the dose for Bicitra?
15-30 mL PO
48
What is the MOA for dopamine blockers?
Stimulate gastric motility by increasing lower esophageal sphincter tone and relaxing pylorus and duodenum.
49
Who should not recieve a dopamine blocker post op?
Patients with a dopamine depletion (Parkinsons and Huntingtons)
50
Which drug is cleared for diabetic gastroparesis?
metaclopramide (reglan)
51
What side effect of metoclopramide can mimic a more sinister condition?
Can cause neuroleptic malignant syndrome - mimicing MH (high temp, muscle rigidity, tachycardia)
52
What neurological side effects do we see with Reglan?
It cross the BBB and can cause extrapyramidal symptoms and sedation
53
What is the dosing for reglan?
10 - 20 mg IV over 3-5 mins (15-30 mins prior to induction)
54
What are the neurological effects of domperidone?
None, doesn't cross the BBB
55
Why isn't domperidone available in the US?
Causes arrythmias and sudden death
56
What is the black box warning for droperidol (inapsine)?
Prolonged QT interval and torsades
Many serious drug interactions
57
Which drug is just as effective and much safer than droperidol?
Ondansetron
58
What is the patho behind vomiting?
Serotonin is released from chromaffin cells of the small intestine → stimulates vagal afferent via 5HT3 receptors → vomiting
59
Where are 5HT3 receptors found?
Everywhere, but high amounts in brain and GI tract
60
When are 5HT3 antagonists ineffective at treating vomiting?
Motion sickness, vestibular stimualtion, and if already vomiting
60
What is the naming convention for 5HT3 antagonists?
-setron
61
What is the most important side effect to know about ondansetron (Zofran)?
Causes slight QT prolongation
62
What is the half life and dosing for ondansetron?
Half life: 4 hours (give at end of case)
Dose: 4-8 mg IV
63
What are the preposed MOA of anti-emetic effects of corticosteroids?
Controls endorphin release and produces anti-inflammatory effects (less pain, less opioids)
64
When should you administer decadron to prevent PONV?
Airway edema?
* PONV: 2 hours before extubating (takes 2 hours for onset)
* Airway: immediately after intubation
65
What are the two side effects for decadron?
1. Perineal buring
2. Hyperglycemia in diabetics (minimal with 1 dose)
66
What is the dosing for dexamethasone?
PONV: 4mg - 8mg
Airway: 12 - 20mg
67
Why is scopolamine the anticholinergic of choice for prevention of PONV?
Produces more desirable effects than the others:
68
What is the MOA of scopolamine?
Competitive muscarinic antagonist (inhibts ACh)
69
When does scopolamine peak?
What does this mean for dosing time?
8 - 24 hours
Should be applied prehospital
70
What is the dosing for a scopolamine patch?
1 patch for 24-72 hours
Priming dose = 140 mcg
Maintenance dose = 1.5 mg over next 72 hours
71
What is the MOA of bronchodilation for SABAs?
Stimulates G proteins → activate cAMP → decreases Ca entry → decrease contractile strength
72
What is the effectiveness of SABA?
Causes a 15% increase in FEV1 in 6 mins (not that effective)
73
What side effects are we concerned with for SABAs?
Tremor (β2 in skeletal muscle)
Tachycardia
Transient decrease in arterial O2 (newly opened alveoli have to offload CO2 first)
Hyperglycemia
74
Which SABA would we give if we wanted to try to avoid the systemic side effects?
Levo-albuterol (Xopenex)
75
What is the dose for Droperidol (Inapsine)?
0.625-1.25mg IV
