Premedication

Question 1

what are goals of premedication?

Answer 1

• reduce anxiety, amnesia
• pain relief
• sedation
• reduce risk of aspiration
• nausea and vomiting prophylaxis
• antisialagogue
• reduce MAC
• prophylaxis of allergic reaction

Question 2

what is the MOA of benzodiazepines?

Answer 2

• sedation produced by intensification of GABA effects

- anxiolysis produced by glycine-mediated inhibitory effect on neuronal pathways in the brain

Question 3

what are the advantages of benzos?

Answer 3

• sedation
• anxiolysis
• amnesia
• minimal effects on ventilation and cardiovascular
• raise seizure threshold
• reduce MAC

Question 4

what are disadvantages of benzos?

Answer 4

• no analgesia (must consider whether pain med is needed more in preop)
• possible paradoxical reaction (confusion, agitation)
• implicated as teratogenic during first trimester (cleft lip)

Question 5

what is the MOA of droperidol (Inapsine)?

Answer 5

antagonizes the activation of dopamine receptors, interferes with transmission mediated by serotonin, NE, GABA; also alpha-adrenergic blocker

Question 6

what are effects of droperidol?

Answer 6

• outward appearance of calm
• dysphoria, restlessness, fear of death
• antiemetic effects

Question 7

what is the MOA of opioids?

Answer 7

bind to specific receptors throughout the central nervous system, tissues

Question 8

what are the advantages of opioids?

Answer 8

• no direct myocardial depression
• pre-emptive analgesia
• analgesia in pre-existing pain, painful procedures
• decreases incidence of increased HR during surgical procedure

Question 9

what are disadvantages of opioids?

Answer 9

• depresses ventilation, particularly RR; apneic threshold elevated; hypoxic drive decreased (not good w/ sleep apnea)
• orthostatic hypotension
• N/V
• no amnestic effect
• sphincter of Oddi spasm
• dysphoria in patients without pain
• histamine release

Question 10

describe morphine

Answer 10

• well absorbed IM
• histamine release
• may cause orthostatic hypotension, pruritus, respiratory depression
• dose 0.1-0.2 mg/kg IM (15-30 min)

Question 11

describe fentanyl

Answer 11

• about 100x more potent than morphine
• usually given just prior to induction
• 5-8 mcg/kg blunts response to laryngoscopy
• most commonly used opioid in anesthesia
• dose IV 1-2 mcg/kg (30-60 sec) last about 30 min to an hour

Question 12

describe NSAIDS

Answer 12

• given to reduce the amount of opioids required postop
• pre-emptive analgesia
• beware: prostaglandin inhibition may decrease platelet aggregation
• caution: elderly, h/o gastric ulcers, renal impairment
• decision to give must involve surgeon
• acetaminophen contraindicated w/ hepatic impairment

Question 13

describe antihistamines

Answer 13

• H1 antagonist given to pts. with h/o chronic atopy or at risk for allergic reaction
• give along with a H2 antagonist
• Benadryl dose: 0.5-1 mg/kg PO

Question 14

describe alpha 2 agonist clonidine

Answer 14

• centrally acting alpha 2 agonist which blunts the autonomic nervous system reflex responses to surgical stimulation (such as increased HR and BP)
• can decrease anesthetic requirement, decrease MAC
• potential for bradycardia and hypotension- give fluids
  dose: 5 mcg/kg PO (90 min)

Question 15

describe anticholinergics

Answer 15

• historical use
  advantages: vagolytic effect, antisialogue effect (turning prone), sedation and amnesia (atropine/scopolamine cross BBB)
  disadvantages: central anticholinergic syndrome, mydriasis and cycloplegia (caution w/ glaucoma), tachycardia and arrhythmias (don’t give to CAD pts.)

Question 16

which anticholinergics are best for increase in HR, antisialogue effects, and sedation?

Answer 16

• atropine increase in HR (give to infants 6 months or <)
• scopolamine best for sedation
• glycopyrrolate best antisialogue effect

Question 17

what are the different types of antiemetics

Answer 17

• GI prokinetics (metoclopramide)
• butyrophenones (droperidol)
• phenothiazines (promethazine)
• serotonin receptor antagonists (Zofran)
• corticosteroids

Question 18

what are the goals to prevent aspiration?

Answer 18

• gastric pH > 2.5

- gastric volume < 25 ml

Question 19

how do H2 antagonist provide prophylaxis against aspiration?

Answer 19

• increase the pH of whatever is released in the stomach from the time medicine takes effect
• takes time to change pH of contents already in stomach since that must be diluted over time
• *does not change volume
• *need to receive the night before and morning of

Question 20

what are different histamine2 receptor antagonists?

Answer 20

• ranitidine (Zantac)
  dose: 150-300 mg PO; 50 mg IV
  onset: 60-90 min
  duration: up to 9 hrs
• famotidine (Pepcid)
  dose: 20-40 mg PO; 20 mg IV
  onset: 60-90 min
  duration: 10-12 hrs

Question 21

how does gastrokinetic agents (metoclopramide) provide prophylaxis against aspiration?

Answer 21

enhances the effects of ACh on the intestinal smooth muscle to :

1) speed gastric emptying
2) increase lower esophageal sphincter tone
3) relax the pylorus and duodenum
4) lower gastric volume
* does not effect gastric pH

Question 22

what is the antiemetic effect of metoclopramide?

Answer 22

dopamine antagonist in the CTZ of the CNS

Question 23

what is the dose and onset of metoclopramide?

Answer 23

PO 10-15 mg (30-60 min)
IV 10 mg (15-30 min)
peds: 0.25 mg/kg

Question 24

what are contraindications of metoclopramide use?

Answer 24

• intestinal obstructions
• Parkinson’s disease (dopamine blockage)
• push slow (potential for extrapyramidal effects; often r/t tardive dyskinesia

Question 25

describe antacids

Answer 25

raises the gastric pH of fluid already present in the stomach by neutralizing the hydrogen ions with a base * disadvantage: increases volume * use a nonparticulate (non colored, no Mylanta) like sodium citrate (Bicitra) * seen often in L&D; always prepare as if you may intubate

Question 26

what is the dose of sodium citrate?

Answer 26

15-30 ml PO (15-30 min)

Question 27

describe proton pump inhibitors

Answer 27

- most effective in controlling gastric acidity and volume - limits the last step in secretion of hydrogen ions: hydrogen-potassium ATPase * clinical use in moderate to severe GERD * takes daily admin over 5 days to inhibit secretion 66% * better than H2 blockers in inhibiting secretion, healing duodenal and gastric ulcers, and treating reflux esophagitis

Question 28

what is the dose of omeprazole (Prilosec)?

Answer 28

20mg PO (single dose takes > 3 hrs to increase pH)

Question 29

describe pediatric anxiolysis

Answer 29

- preop includes parents, patient, visual aids - empower by allowing to bring toy, blanket, source of security - explain as you go, allow to help, distract - reduce anxiety, sedate, provide amnesia * indicated for 6 mths and older - oral, nasal, or rectal - versed- PO - methohexital- PR - ketamine- IM