Preoperative Medications

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Preoperative Medications
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Goals of Pre-op Medication

• Optimize physical condition
• Relief of anxiety
• Relief of pain
• Amnesia
• Facilitate induction

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Goals (cont)

• Facilitate smooth operative course
• Facilitate smooth wake-up
• Antiemetic effect
• Prophylaxis against aspiration

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Psychological Preparation

• Pre-op visit lays the foundation
• Trust and confidence are essential
• Be efficient, informative and reassuring
• More effective than sedatives

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Psychological Prep (cont)

• All patients have some anxiety
• May be outwardly calm, inwardly terrified
• Patients on sedatives have more anxiety

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Preoperative Medication

• Should be individualized
• Give for specific indications
• Monitoring should be appropriate

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Contraindications to Sedation

• Poor physiologic reserve
• Extremes of age
• Head injury
• Hypovolemia

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Routes of Administration

• Oral (60-90 minutes)
• Intramuscular (30-60 minutes)
• Intravenous
• Rectal
• Nasal
• Dermal

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Specific Drugs and Dosages

• Know drugs in each class
• Know characteristics of class

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Benzodiazepines

• Anxiolysis
• Amnesia
• Sedation
• Anti-convulsant
• All effects are dose-dependent

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Benzodiazepines

• Minimal respiratory depression
• Minimal cardiovascular depression
• Work well with opioids
• Few side effects

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CNS Action

• Sedation
• Enhancement of GABA
• Anxiolytic
• Glycine mediated inhibition of brain stem
• Amnesia
• Unknown mechanism

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Specific Benzodiazepines

• Diazepam (standard)
• Pain on injection
• Active metabolites
• Good anticonvulsant
• Used as P.O.. pre-op

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Specific Benzodiazepines (cont)

• Lorazepam
• Slow onset, long duration
• Profound amnesia
• Not good for outpatients

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Specific Benzodiazepines (cont)

• Midazolam
• No irritation or phlebitis
• 2-3x potent as diazepam
• Rapid onset, rapid metabolism
• Excellent short-term amnesia
• Given IV prior to surgery
• Given P.O.. to children

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Barbiturates

• Sedative
• Dose dependent respiratory depression
• Less safe than benzodiazepines
• Do not give to patients with porphyria

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Butyrophenones (Droperidol)

• Dopamine antagonist
• Appear calm and tranquil
• Inner terror is reported
• High rate for refusing surgery
• Alpha blockade
• Excellent anti-emetic

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Other Sedatives

• Hydroxyzine
• Used to augment opioids
• Diphenhydramine
• Histamine blocker
• Sedative and anticholiergic

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Other Sedatives (cont)

• Phenothiazines
• Used to augment opioids
• Chloral hydrate
• P.O.. pre-op for elderly patients

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Opioids

• Produce analgesia
• Useful prior to painful procedure
• Establish baseline analgesia
• Reduce anesthetic requirements
• Comfort upon awakening
• Work well with sedatives

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Problems with Opioids

• Respiratory depression
• Orthostatic hypertension
• Histamine release (morphine)
• Shift in CO2 response curve

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Problems with Opioids (cont)

• Occasional dysphoria
• Nausea and vomiting
• Pruritus
• Sphincter of Oddi spasm

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Opioid Premedication

• Usually given IV in holding area
• Monitor pulse oximetry
• Fentanyl lollipop
• Nasal sufentanil
• Oral codeine

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Prophylaxis for Aspiration

• Who is at risk?
• Full stomach (all emergencies)
• Pregnancy
• Obesity
• Diabetes
• Hiatal hernia / reflux

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Prophylaxis / Aspiration (cont)

• Critical values
• Volume gt 25 ml.
• pH lt 2.5

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Prophylaxis / Aspiration (cont)

• NPO Guidelines
• NPO after midnight
• Tradition of strict enforcement
• Now being challenged
• Clear liquids may be o.k.
• Dehydration and hypoglycemia

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Pharmacologic Preparation

• Reduce gastric volume
• Increase gastric pH
• Increase gastric motility

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Anticholinergics

• Atropine / Robinul
• Probably not effective
• Relax lower esophageal tone
• Have CV side effects

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Histamine-Receptor Antagonists

• Cimetidine / Ranitidine
• Reduce gastric acid secretion
• Increase gastric pH
• Few side effects
• Give H.S. and A.M..

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Histamine Receptor Antagonists (cont)

• Cimetidine
• Slows metabolism of other drugs
• Ranitidine
• More effective
• Does not alter hepatic function

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Antacids

• Neutralize stomach acids
• Onset is rapid
• Increase gastric volume
• Antacid can be aspirated
• Use only non-particulate antacids

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Metoclopramide

• Gastrokinetic agent
• Increases upper GI motility
• Increases G.E. sphincter tone
• Relaxes pyloris and duodenum

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Metoclopramide (cont)

• Has antiemetic properties
• May be offset by atropine or opioids
• Combine with H2 antagonist
• Do not use on bowel cases

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Antiemetics

• Emesis is cause for admission
• Treatment is cost effective
• Treat high risk patients
• History of N and V
• Ophthalmologic surgery
• Gyn procedures
• Obesity

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Antiemetics (cont)

• Droperidol
• Effective in low dose
• Metoclopramide
• Antiemetic effect in addition to reduction in
  gastric volume

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Antiemetics (cont)

• Ondansetron
• Highly effective new drug
• Very expensive
• Good rescue drug

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Anticholinergics

• Antisialagogue
• Glycopyrrolate
• Ophthalmic procedures
• ENT procedures
• Vagolytic effect
• Atropine

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Anticholinergics (cont)

• Sedation and amnesia
• Scopolamine
• See Barash for side effects

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Clonidine

• Antihypertensive
• Alpha-2 blocker
• Produces sedation
• Reduces anesthetic requirements
• Acute withdrawal causes rebound

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Other Pre-op Medications

• Antibiotics
• Ordered by surgeon
• Protocol for valvular heart disease
• Give slowly

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Other Preop Medications (cont)

• Steroids
• Adrenals may be suppressed up to one year after
  taking steroids
• Hydrocortisone 100 mg IV

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Other Preop Medications (cont)

• Insulin
• Agree on plan prior to surgery
• Always start IV with dextrose prior to giving
  insulin

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Other Preop Medications (cont)

• Insulin (cont)
• Treatment plans
• No insulin
• 1/2 dose of insulin
• Insulin infusion

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Pediatric Considerations

• Always approach a child as if you will have to do
  him/her again
• Use oral medication where possible
• Consider needs of the parent

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Small Infants

• Separation not a problem
• High vagal tone
• Consider anticholinergic

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Preschool Children

• Separation extremely traumatic
• Use oral premedication
• Versed
• Fentanyl
• Anticholinergic after asleep
• Avoid cyclobrutane

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Older Children

• Assess level of anxiety
• Include in decision making
• Premedicate as appropriate
• Pre-op visit extremely important