PRE OPERATIVE EVALUATION BY VAISHALI SYAL MAM
TEXT IN THE PPT
PREMEDICANT DRUGS
Vaishali Syal Moderator – Dr. Manisha Bhatt
Introduction
Preoperative medication consists of :
□ psychological
□ pharmacological preparation.
How the patient should be like before entering OT:
□ free from apprehension
□ sedated
□ arousable
□ cooperative.
Goals of preoperative medication
□ Relief of anxiety
□ Sedation
□ Amnesia
□ Analgesia
□ Drying of airway secretions
□ Prevention of autonomic reflex response
□ Reduction of gastric fluid volume and increased pH
□ Antiemetic effects
□ Reduction of anesthetic requirements
□ Facilitation of smooth induction of anesthesia
□ Prophylaxis against allergic reactions.
Psychological preparation
Non-pharmalogical antedote to
apprehension :
□ preoperative visit
□ interview
Adminstration of premedication :
□ 1-2 hr before the surgery
□ night before.
Prescribed medications:
□ 2 hours prior to surgery
□ small sip of water (<30 ml) orally
Ideal premedicant drug :
□ Anxiolytic
□ Analgesic
□ Sedative
□ Amnesic
□ Safe for patient
□ Painless and easy to administer
□ Highly reliable and specific
□ Rapid onset and rapidly cleared
□ Free of side effect and interaction with other drugs
□ Should not produce undue depression of cardiovascular, respiratory and central nervous system
Relative contraindications to sedative premedication :
□ New born < 1 year, elderly
□ Decreased level of consciousness, intracranial pathology
□ Severe pulmonary pathology
□ Hypovolemia
□ Airway obstruction or airway surgery, sleep apnea
□ Severe hepatic and renal disease
□ Rapid sequence induction
□ Obstetric anesthesia
□ Day case surgery
Recent practice of
premedication :
Morphine and hyoscine has been abandoned
with:
□ Modern intravenous and inhalational anesthetic agents
□ Increasing use of day-case surgery
□ Same-day admissions
□ Changes to the surgical list ,making the timing of drug delivery difficult
▪ The choice of drugs used for premedication depends on the procedure, patient and anesthetic technique.
▪ Some patients prefer not to have premedication.
▪ Potential benefits may be outweighed by potential problems especially with day-case surgery.
▪ Reviews found no evidence of a difference in time to discharge from hospital following adult day surgery in patients who received anxiolytic premedication.
Premedication for anxiety in adult day surgery. Smith AF', Pittaway AJ. # Author information
Update in Premedication for anxiety in adult day surgery. [Cochrane Database Syst Rev. 2003]
Abstract BACKGROUND: Surgery is increasingly performed on a day-case basis. Many patients are anxious pre-operatively and might benefit from pharmacological anxiolysis. Drugs are sometimes not used, however, for fear of delaying discharge from hospital.
OBJECTIVES: To asses the effect of anxiolytic premedication on time to discharge in adult patients undergoing day case surgery under general anaesthesia.
SEARCH STRATEGY: Trials were identified by computerised searches of the Cochrane Controlled Trials Register, MEDLINE, EMBASE, by checking the reference lists of trials and review articles, by hand-searching three main anaesthesia journals and by contacting five researchers active in the field and the Product Information departments of the manufacturers of five commonly used premedicants.
SELECTION CRITERIA: All randomised controlled trials comparing an anxiolytic drug(s) with placebo before general anaesthesia in adult day case surgical patients.
DATA COLLECTION AND ANALYSIS: We collected data on anaesthetic drugs used, results of tests of psychomotor function where these were used to assess residual effect of premedication, and on times from end of anaesthesia to ability to walk unaided or readiness for discharge from hospital. Formal statistical synthesis of individual trials was not performed in view of the variety of drugs studied.
MAIN RESULTS: Searching identified twenty-nine reports; fourteen studies, with data from a total of 1263 patients, were considered eligible for analysis. Only two studies specifically addressed the discharge questi studies used clinical criteria to assess fitness for discharge, though times were not given. Again, there was no difference from placebo. Four studies used both clinical measures and tests of psychomotor function as tests of recovery from anaesthesia. In none of these studies did the premedication appear to delay discharge, although performance on tests of psychomotor function was sometimes still impaired. Of the four studies which used tests of psychomotor function to assess recovery, three showed impaired recovery (after midazolam 7.5mg, midazolam
15mg or diazepam 15mg) which might possibly interfere with discharge from hospital.
REVIEWER'S CONCLUSIONS: We have found no evidence of a difference in time to discharge from hospital in patients who received
anxiolytic premedication. However, in view of the age and variety of anaesthetic techniques used, inferences for current day-case practice should be made with caution.
Group of preanesthetics
Anxiolysis Benzodiazepines
145-90 mins preoperatively)
Amnesia Benzodiazepines
(as above)
Analgesia Opioids
6A'S OF images.medchrome.com
Premedicatie
Anti-autonomia Anticholinergics (Antisialog ogue: Antivagolytic) Beta-blockers
Antiemetic
Dopamine antagonists, SHT
antagonist, Antihistminic, Anticholinergic
Antacid H2 Blocker
PEL Sodium citrate
I. Anxiolytics / Sedative / Hypnotic :
□ – Benzodiazepines (still commonly used)
□ · Diazepam
□ · Lorazepam
□ · Midazolam
□ · Alprazolam
□ – Barbiturates (not used much)
□ · Secobarbital
□ · Pentobarbital
Benzodiazepines :
□ Produce anxiolysis, amnesia and sedation
□ Act predominantly on GABA receptors in the CNS.
□ Minimal respiratory and cardiac depression
□ Do not produce nausea and vomiting
□ They are not analgesics
□ Crosses placental barrier and may cause neonatal depression
Comparison of pharmacologic variables of benzodiazepines:
Diazepam Lorazepa
m
Midazola m
Dose equivalent (mg)
10 1-2 3-5
Time to peak effect after oral dose (hr)
1-1.5 2-4 0.5-1
Elimination half life (hr)
20-40 10-20 1-4
Clearance (mL/kg/min)
0.2-0.5 0.7-1.0 6.4-11.1
Volume of distribution
0.7-1.7 0.8-1.3 1.1-1.7
Diazepam
□ Can be used as a sole agent as for cathetrisation, cardioversion, bronchoscopy etc and as an adjuvant to LA
□ Cirrhosis of liver leads to upto fivefold increase in elimination half- life
□ Doses :
0.25 to 0.5 mg/kg orally 0.25 mg/kg IM 0.3 to 0.6 mg/kg IV as an inducing agent Dose requirements decrease 10% per decade of patient’s age.
□ Flumazenil, is effective in reversing the sedative effects.
Lorazepam
□ A new and effective sedative/amnesic/anxioloytic
□ Has stabilising effect on cardiovascular and respiratory systems
□ Twice as potent as midazolam.
□ used for lengthy procedures where prompt emergence not desirable
□ Obesity prolongs the sedative effects of Lorazepam.
□ Dose for premedication :
□ Oral – 50 μg/kg, not more than 4 mg (can be given 90 min before anesthesia)
□ 0.03–0.05 mg/kg IM
□ Sedation : 0.03–0.04 mg/kg IV
Midazolam
□ Water soluble benzodiazepine with painless administration
□ Amnesic effects are more potent than sedative effects.
□ choice of drug for out patient surgery and pediatric premedication
□ Capable of crossing the BBB with effects ranging from tranquillization to full anesthesia.
□ Respiratory depressant
□ Hazardous in hypovolemic patients.
Midazolam
□ Patients with decreased intracranial compliance show little or no change in ICP with midazolam
□ Usual dose : 0.15 to 0.3 mg/kg IV
□ Lesser dose to be used in elderly and obese patients
□ 0.5 to 0.75 mg/kg orally produces anxiolysis and degree of tranquillity within 30 min
□ Pediatric dose : 0.1 mg/kg IV or IM
□ Intranasal midazolam 0.3 mg/kg has quicker onset of action than oral midazolam.
II. Opioid analgesics
□ – Morphine
□ – Pethidine
□ – Fentanyl
They differ in duration of action ; can be given parentally.
• administered preoperatively for sedation
• control hypertension during tracheal intubation
• analgesia
For preoperative analgesia, the use of IV fentanyl is preferred :
• rapid onset
• short duration
❑ Fentanyl is also available as transdermal
patches.
Morphine
□ An opium alkaloid and a standard potent addictive analgesic/hypnotic/sedative/anxiolytic
□ May lead to GI spasm, biliary tract spasm, even renal tract spasm.
□ Causes constipation and urinary retention
□ Depresses respiration both in rate and depth
□ Passes through placental barrier
□ Tolerance occur to morphine
□ 1mg of IV morphine ≈ 4 mg of oral morphine
□ Dose : 1.0 – 2.5 mg IV
Morphine
□ Morphine should be carefully used in :
▪ Extremes of ages
▪ Respiratory cripples
▪ Hypothyroidism and hypopituitarism
▪ Liver and kidney pathology
▪ In patients with increased ICP
▪ Pregnancy
▪ Patients treated with MAO inhibitors
Fentanyl
□ Potent narcotic analgesic ; 100 times more potent than morphine
□ Metabolised in liver and excreted through urine and feces
□ Respiratory depression and rigidity of respiratory muscles which can be satisfactorily treated with naloxone
□ Less nausea and vomiting
□ Can be used along with droperidol for neuroleptanalgesia
□ Cautious use in patients with COPD, head injury and patients on MAO inhibitors
□ Dose : 1-5 μg/kg IV
III. Anticholinergic drugs
Three drugs are in use as preanesthetic :
□ – Atropine
□ – Hyoscine
□ – Glycopyrrolate While the first two are tertiary amines that cross the BBB, glycopyrrolate is a quateranry amine which does not cross BBB and is not absorbed from GI tract
Doses :
• Atropine 0.3 – 0.4mg IV : has vagal inhibition, CNS stimulations
• Hyoscine 0.4 mg IV : more antisialogogue action with less vagal inhibition and causes sedation and amnesia, so avoided in elderly patients
• Glycopyrrolate (dose 0.1 – 0.3 mg IV) : has no central action, longer duration of action, and less tachycardia
Clinical effects of anticholinergics
□ Antisialogogue effects : Glycopyrrolate and hyoscine are more potent than atropine, reduce secretions and bradycardia after succinylcholine
□ Sedative and amnesic effect : In combination with morphine, hyoscine produces powerful sedative and amnesia effects
□ Prevention of reflex bradycardia : Atropine is used to prevent oculocardiac reflex in eye surgery and is used to prevent halothane bradycardia
Comparitive effects of anticholinergics :
Atropine Hyoscine Glycopyrrola
te
Antisialogogue effect
+ +++ ++
Sedative and amnesic effects
+ +++ 0
Central nervous system toxicity
+ ++ 0
Relaxation of gastro- oesophageal sphincter
++ ++ ++
Mydriasis and cycloplegia
+ ++ 0
Increased heart rate
+++ + ++
Side effects of anticholinergics :
□ CNS toxicity : Atropine produces central anticholinergic syndrome of the CNS, producing restlesness, agitation, somnolence and convulsions.
Physostigmine 1-2 mg IV reverses the effects when given with glycopyrrolate
□ Reduction in lower oesophageal sphincter tone
□ Tachycardia & Hyperthermia
□ Mydriasis and cycloplegia
□ Unpleasant and excessive drying of mouth Increased physiological dead space by 20-
IV. Antiemetics
□ – Ondansetron
□ – Metoclopramide – most commonly used
□ – Phenothiazines – Promethazine used
Antihistamnies and antiemetics enhance gastric emptying and are used to prevent nausea, vomiting in patients which is the single most common factor delaying recovery in patients.
Additional usage includes :
▪ Sedative property
▪ Relieving anxiety
Ondansetron
❑ Highly effective in management of vomiting
related with chemotherapy and radiotherapy ❑ Used for prevention of PONV in a dose of 4
mg IV ❑ In children, a dose of 0.1 mg/kg upto 4 mg may
be used in vomiting prone children ❑ Elimination half life is 3.5 to 4 h in adults ❑ Side effects include headache, constipation,
diarrhoea, sedation, a sense of flushing, warmth and so on.
Metoclopramide
❑ A new stable, water soluble antiemetic drug used
parenterally, orally and even rectally ❑ Dose : 0.15 to 0.3 mg/kg IV, effect lasts for 12h ❑ Increases the rate of gastric emptying, and
causes some increase in peristalsis of gut ❑ May be used in emergency anesthesia ❑ Indicated in patients with hiatus hernia, obese,
parturients and duodenal ulcer. ❑ Acts both centrally and peripherally
Metoclopramide
• Central Action : Acting as dopamine antagonist, acts on medullary vomiting center, producing anti-emetic effect.
• Peripheral Action : Enhances gastric emptying so that gastric components are passed earlier, preventing gastric aspiration. NOTE : Atropine should be withheld until
induction of anesthesia as it blocks effects of metoclopramide
▪ Side effects include abdominal cramps following rapid IV injection, occasional neurological dysfuncyion etc
V. Prevention of pulmonary aspiration :
□ No drug or combination is absolutely reliable in preventing the risk of aspiration
□ Patients with no apparent risk of aspiration, these drugs are not recommended
□ Cimetidine and Ranitidine are the two drugs in common clinical use which when used as premedication may increase the gastric pH higher than 2.5 and decrease the gastric volume < 25 mL
Factors predisposing to aspiration :
□ Emergency surgery
□ Inadequate anesthesia
□ Abdominal pathology
□ Obesity
□ Opioid premedication
□ Neurological deficit
□ Lithotomy
□ Difficult intubation/airway
□ Hiatal hernia
Summary of fasting recommendations to reduce the risk of pulmonary aspiration :
Ingested material Minimum fasting
period ( hrs)
Clear liquids 2
Breast milk 4
Infant formula 6
Non human milk 6
Light meal (toast and clear liquids) 6
□ Reduce the secretion of acid into the stomach by about 70% by blocking the effect of histamine on receptors in the stomach wall
□ Used for prevention of acid aspiration syndrome
Ranitidine seems to be better than
cimetidine due to:
▪ its longer duration of action
▪ its lower incidences of side effects and drug interactions
□ Doses : Cimetidine – 400 mg (PO) Ranitidine – 150 mg (PO), 90 to 150 min before induction of anesthesia
□ Also effective when given IV 45 to 60 min before induction, but are unable to influence acid already present in the stomach, which depends on gastric emptying
□ Oral sodium citrate 15-30 minutes before induction can also be used for this purpose
Premedication in pediatric patient :
□ Includes age-specific psychological preparation and an emphasis on oral medications when sedation is desired.
□ Topical anesthetic creams are often prescribed for children before cannulation
A. Psychological factors in pediatric patients:
1. Age : most important factor in the success of
preoperative visit and interview 2. Children who do not ask questions during
preoperative interview may be masking high levels of anxiety 3. It may be helpful to have the parents
accompany these children to the operating room for children who wish to take active part in anesthesia
B. Pharmacological preparation for pediatric patient :
Their use is controversial. (Oral premedication is preferred for patients without IV access.) 1. Midazolam (0.5 – 0.75 mg/kg) in a flavored
oral preparation produces sedation. Roohafza, honey etc can be used as effective flavoring agents. Intranasal midazolam has faster onset but causes nasal burning. 2. Paracetamol syrup - 5-10mg/kg
10-15mg/kg rectally produces analgesic effects.
3. Ketamine (5 – 10 mg /kg) prescribed 20 to 30
min before induction facilitates smooth separation from parents 4. Opiods : In the absence of an IV catheter,
transmucosal administration of fentanyl (lollipop) is effective in producing sedation.
Preoperative Surgical Antibiotic Prophylaxis :
❑ Indications :
• Contaminated and clean contaminated procedures
• Clean procedures when infection would be catastrophic (device implants)
• Prevention of endocarditis
• Prevention of infection in immunocompromised patients
□ Antibiotic selection : Cephalosporins (against skin microbes)
Vancomycin (anerobic and gram-negative microbes)
□ Timing :
• 1 hour prior to incision
• 2 hours before incision for vancomycin
• Prior to tourniquet inflation
• Redose after two half lives (Cefazolin has half- life of 2 hours so redose if surgical procedure > 4 hours)
□ Beta-Lactam allergy : Vancomycin or Clindamycin
Preop Medication instruction guideline :
Medication to be continued on day of Surgery :
□ Anti hypertensive
□ Diuretics
□ Cardiac medication
□ Antidepressant – antianxiety
□ Thyroid, asthma medication
□ Steroids (oral & inhaled)
Medications to be discontinued before surgery :
□ Aspirin : * 7 days before surgery
□ NSAIDs : * 48 hrs before plastic retinal surgery
□ Oral hypoglycemic drugs : * on the day of surgery
□ Insulin : * 1/3rd dose in morning
□ Warfarin : * 4 days before surgery
□ Heparin : * 4 – 6 hrs before surgery
□ MAO inhibitors : * 2 weeks before surgery
Conclusion
□ Preoperative visit from an anesthesiologist greatly reduces patient anxiety than preoperative sedative drugs.
□ Children, aged 2–10 years who experience separation anxiety, may benefit from premedication
□ Patients who will undergo airway surgery or extensive airway manipulations benefit from preoperative administration of anticholinergics to reduce airway secretions before and during surgery.
□ “Premedication should be given purposefully, not
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