5183premedication in Anaesthesia Final Dr Jayesh Jain

Dr.Jayesh J.JainDr.Jayesh J.Jain

NKPSIMS & NKPSIMS & RC,RC,

NagpurNagpur..

ContentsContents Definition Definition HistoryHistory AimsAims Qualities of premedicantQualities of premedicant Drugs usedDrugs used Premedication in associated disordersPremedication in associated disorders Premedication in obstetrics patients Premedication in obstetrics patients Premedication in outpatients surgeries. Premedication in outpatients surgeries. Premedication in pediatric patients. Premedication in pediatric patients.

DEFINITION DEFINITION

Administration of various drugs Administration of various drugs before induction of before induction of

anaesthesia. anaesthesia.

HISTORYHISTORY :

• 1869 –Bernard gave morphine as premedicant in dogs and

showed, it reduce the dose of chlorofom required.

• 1911 – at anaesthetic section of Royal Society of Medicine,

use of atropine, morphine and scopolamine before induction

was first described

AIMS OF PREMEDICATION AIMS OF PREMEDICATION :

• To allay pre-operative fear and anxiety.

• To produce amnesia and analgesia.

• To reduce secretion from salivary glands and respiratory tract.

• To potentiate anaesthetic drugs

• To depress unwanted reflex vagal activities

• To reduce the pH and volume of gastric contents and risk associated with regurgitation and aspiration.

• To attenuate sympathetic reflex activities and stress associated with anaesthesia and surgery.

• To reduce incidence of post operative nausea and vomiting.

Qualities of an ideal Qualities of an ideal premedication drugpremedication drug

Devoid of any side effects Devoid of any side effects Minimal depression of respiration and Minimal depression of respiration and

cardiovascular function. cardiovascular function. Simple and pleasant to take. Simple and pleasant to take. Should act over reasonable period of time. Should act over reasonable period of time. Should be effective in all patients. Should be effective in all patients.

1. OPIOIDS 1. OPIOIDS :

• As a premedicant produce analgesia , sedation and angiolysis.

Mechanisms of Action :

• Interact with specific receptors in the CNS and in peripheral tissue namely , , .

Supraspinal & Supraspinal &

spinal analgesiaspinal analgesiaSupraspinal & Supraspinal &

spinal analgesia spinal analgesia Supraspinal & Supraspinal &

spinal analgesia spinal analgesia

Respiratory Respiratory depressiondepression

Respiratory Respiratory depressiondepression

Respiratory Respiratory depressiondepression

Constipation Constipation DysphorhiaDysphorhia Physical Physical dependencedependence

Urinary retention Urinary retention Sedation Sedation Urinary retention Urinary retention

Miosis Miosis Constipation Constipation

DiuresisDiuresis

ACTIONS :

CNS :

• Analgesia, sedation, euphoria

• Depression of respiratory centre.

• Depression of vasomotor centre.

• Depression of cough reflex.

• Hypothermia

• Stimulate chemo-receptor trigger zone

• Stimulate vagal centre

• Stimulate EW nucleus

• Cortical and hippocampal areas.

CVS :

• Vasodilatation

• Bradycardia

• Decrease cardiac work.

GIT :

• Constipation

• Delayed gastric emptying.

Respiratory system :

• Respiratory depression.

• Broncho constriction

Genitourinary :

• Urinary retention

• Diuresis

• Antidiuresis

CONTRA INDICATIONSCONTRA INDICATIONS

• Respiratory insufficiency.

• Head injury

• Hypotensive states.

• Undiagnosed acute abdomen.

• Elderly patient

• Hypothyroidism

Commonly used OPIOIDS

DrugDrug Dose Dose AdvantageAdvantage DisadvatageDisadvatage

MorphineMorphine

0.1 – 0.2 mg/kg 0.1 – 0.2 mg/kg IMIM

10 – 15 mg IM in 10 – 15 mg IM in adultsadults

Sedation Sedation

AnxiolysisAnxiolysis

AnalgesiaAnalgesia

Depression of Depression of cough reflex, cough reflex,

miosis, addictive miosis, addictive propertiesproperties

Pethidine Pethidine

1.5 – 2 mg/kg IM1.5 – 2 mg/kg IM

Child. Child.

50 – 100 mg IM50 – 100 mg IM

AdultsAdults

Less spasmodicLess spasmodic

Less histamine releaseLess histamine release

Less depression of cough Less depression of cough reflex reflex

Less newborn respiratory Less newborn respiratory depression depression

Effective antishiveringEffective antishivering

Less potent Less potent

Antimuscarinic Antimuscarinic effectseffects

High incidence of High incidence of nausea vomitingnausea vomiting

Convulsant. Convulsant.

Fentanyl Fentanyl 2 – 5 2 – 5 g/kg IV g/kg IV

Hemodynamics stability Hemodynamics stability

Absence of histamin Absence of histamin release release

Suppression of stress Suppression of stress responseresponse

More potent, short More potent, short duration duration

Muscle rigidity Muscle rigidity

Bradycardia Bradycardia

PentazociPentazocine ne 0.4 mg/kg IV0.4 mg/kg IV

Less respiratory depression Less respiratory depression

Low addictive property Low addictive property

Sympathetic over Sympathetic over activityactivity

Less sedation Less sedation

2. BENZODIAZEPINES

• As a premedicant – sedation, anxiolysis, anticonvulsant, muscle relaxation, anterograde amnesia.

Mechanism of Action :

• Facilitating the action of GABA on post synaptic membrane increase chloride conductance hypopolarization.

Advantages of Benzodiazepines :

1. High therapeutic index

2. Less respiratory depression

3. Low abuse potential

4. Lack microsomal induction

5. Specific antidote – Flumazenil.

Commonly used BENZODIAZEPINES

DrugDrug Dose Dose AdvantageAdvantage DisadvatagDisadvatagee

DiazepaDiazepamm

0.25-0.5mg/kg 0.25-0.5mg/kg orallyorally

5-10mg iv5-10mg ivPotent sedative Potent sedative

Pain on Pain on injection injection

Long acting Long acting

MedazolaMedazolamm

0.03 – 0.05 0.03 – 0.05 mg/kg IVmg/kg IV

0.5 mg/kg oral.0.5 mg/kg oral.

Short acting Short acting

More potent More potent

LorazepaLorazepam m

25 – 50 mg oral 25 – 50 mg oral

1 – 4 mg IV / IM. 1 – 4 mg IV / IM.

Age and liver Age and liver disease does not disease does not

affect metabolismaffect metabolismLong acting. Long acting.

Common Features :

• Potentiate the effect of non-depolarizing muscle relaxant.

• Depressed respiration when administered with opioids.

• Scopolamine potentiate their amenstic activity.

• Midazolam is helpful in preventing emergence delirium after ketamine anaesthesia

3. PHENOTHIAZINES :

• As a premedicant – produce sedation, anti emetic.

Mechanism of action

• D2 receptor antagonism in CNS.

Actions :

• CNS –

• Indifference to surrounding

• Pausity of thought

• Emotional quietening

• Sleep which is easily arousable.

• ANS –

1 antiadrenergic activity

• Anticholinergic

• Antihistaminic

• Anti 5HT-3 activity.

• CVS –

• Hypotension

• Tachycardia

Adverse Effect :

• Drowsiness lethargy

• Anticholinergic

• Hypotension

• Extrapyramidal side effect

• Cholestatic jaundice.

Commonly used drug :

• Promethazine – 0.5 mg/kg IM/IV

4. NEUROLEPTICS :

• As a premedicant – produced sedation, antiemetic

Mechanism of Action :

• D2 Antagonism in CNS.

Actions :

• CNS –

• Indifference to surrounding

• Paucity of thought

• Emotional quietening

• Sleep which is easily arousable.

• ANS –

• Weak 1 antiadrenergic

• Weak anticholinergic.

CVS –

• Hypotension

• Tachycardia

Adverse Effect

• Drowsiness

• Lithargy

• Postural hypotension

• Anticholinergic

• Endocrinal imbalance.

• Extra pyramidal disturbances.

• Acute muscular dysptonia

• Akanthisia

• Malignant neuroleptic syndrome.

Commonly used drug

• Haloperidol – 5 mg IM

• Droperidol – 0.2 mg/kg orally

0.1 mg /kg IM

5. ANTICHOLINERGIC

As a premedicant –

• Reduced secretions.

• Vagolytic

Mechanism of Action :

• Block post ganglionic parasympathetic nerve endings through muscarinic receptors i.e. M1, M2, M3 receptors.

Drug Drug Vagolytic Vagolytic AntisialagoguAntisialagogue e

Sedation Sedation & &

Amnesia Amnesia

AtropineAtropine 3 +3 + 1 + 1 + 0 0

ScopolaminScopolaminee

1 +1 + 2 + 2 + 3 + 3 +

GlycopyrolaGlycopyrolate te 2 + 2 + 3 + 3 + 00

COMPARATIVE EFFECTS OF ANTICHOLINERGICS

ACTIONS :

CNS –

• Overall CNS stimulation by atropin

• CNS depression by hyosin.

CVS –

• Facilitate AV conduction – increase PR interval.

• Tachycardia and stimulation of vasomotor centre – increase blood pressure.

• Histamine release and direct vasodilator effect – decrease blood pressure.

SMOOTH MUSCLES :

• All smooth muscles are relax

• In GIT – constipation

• Bronchodilatation

• Urinary retention

GLANDS :

• Decrease secretion from all glands.

• Decrease the volume of gastric content.

INCREASE BODY TEMPERATURE

EYE –

• Mydriasis ,

• cycloplegia.

SIDE EFFECT :

• Dry mouth, difficulty in swallowing

• Fever

• Difficulty in micturation.

• Photophobia, blurring of vision.

• Excitement

• Psychotic behavior.

COMMONLY USED DRUGS :

• Atropine – 0.02 mg/kg IV/IM

Disadvantage – CNS excitation

Tachycardia

Fever.

• Hyosine : 0.015 mg/kg oral or IM in children

0.3 – 0.6 mg IM in adult.

Disadvantages : -

More mydriatic

Prolonged sedation.

• Glycopyrrolate – 4 – 8 gm/kg

6. Drugs used to alter gastric fluid volume & pH :

As a premedicant – reduced the likelihood of aspiration of gastric contents.

Risk factors : associated with aspiration.

• Abdominal distention

• Diabetics

• Emergency surgery.

• Raised intracranial tension.

• Hiatal hernia.

• Pregnancy

• Drugs

• Antimuscarinics opioids.

A. Antacids

a) Soluble : Na bicarbonate

b) Non-soluble – Mg hydroxide, Al hydroxide, Calcium carbonate.

Actions :

• Neutralises gastric acid immediately.

• Doest not decrease gastric volume.

• Can increase gastric volume – when used with opioids.

• Better to administer with prokinetics.

• In soluable antacids. May cause significant pulmonary damage after aspiration.

B. H2 antagonists :

• Ranitidine – 50 – 200 mg orally

50 – 100 mg IV

• Cimetidine 150 – 300 mg orally/parenterally

• Famotidine. 20 mg orally BD

Actions :

• Block nucturnal and fasting acid production.

• Partially block meal induced acid serection.

• Ranitidin most commonly used have less side effect and long duration of action.

• Cost effective.

C. Proton Pump Inhibitor :

• Inhibit H+ K+ ATPase enzyme present in parital cells

• Minimal side effect

• Cost is concern

• Drugs -

• Omeprazole – 20 – 40 mg OD

• Lansoprazol – 15 – 30 mg OD

D. Prokinetics :

• Acts by increasing cholinergic activity in enteric neurons.

• Agonist at 5HT4 – promotes release of ACH.

• D2 antagonism – potentiate cholinergic stimulation

anti emetic and anti nausea.

• Well tolerated

• If given rapidly – abdominal cramps.

• Drowsiness, restlessness, agitation.

Drugs :

• Metoclopramide – 0.1 – 0.3 mg /kg IV

• Domperidon – 0.3 – 0.6 mg /kg orally

• Domperidon produce less CNS side effects.

7. Antiemetics-

• Nausea and vomiting are single most common factor delaying recovry of patients.

• Factors associated with increased incidence of nausea and vomiting

•Sex – female

•Type of surgery- gynaecological, laparoscopic, ENT, ophthalmic sx

• Prolonged duration of anaesthesia

• Metabollic disturbances

• Raised ICT

• Previous history

• Psychogenic stimuli

DRUGS-

1. 5HT3 Antagonist-

• Blocks 5HT3 receptors on intestinal vagal afferent as well as CNS

• Most effective

• Exhibit few side effects

• Cost is major concern

Ondansetron- 4-8mg iv

0.1mg/kg upto 4 mg in children

Dolasetron- 25-50mg oral

12.5mg IV

2. Butyrophenones-

• Action is through central dopaminergic blockade.

• Potent sedative with an anti anxiety action.

• Extrapyramidal effects 1 anti adrenergic action, anticholinergic effects are major side effects.

• Drugs :

• Droperidol 2.5 mg to 10 mg IM or IV.

3. Phenothiazine

• Action is through antidopaminergic and anticholinergic properties.

• Powerful hypnotic with minimal respiratory depression.

• Cost Effective.

• Drugs :

• Promethazine, perphenazine, promazine.

8. Centrally acting 8. Centrally acting 2 agonists2 agonists – –

As a premedicant –

• Sedation and anxiolysis

• Reduced requirements of anaesthetic and analgesic drugs.

• Maintain perioperative hemodynamic stability.

• Reduced agitation in children after Sevoflurene anaesthesia

• Reduced PONV.

• Obtund stress response

Drugs :

• Clonidine – 3 – 5 g /kg orally – 60 – 90 min. before surgery.

• Residual post-op sedation is major concern.

PREMEDICATION IN ASSOCIATED DISORDERS :

1. Hypertensive patients :

• Objective of premedication –

• Optimum sedation and anxiolysis

• To preserve perioperative hemodynamics stability

• To obtund stress response to intubation and surgery.

• Antihypertensive drugs to be continued except Losertan & Diuretics

2 agonist, opioids, esmolol are given to preserve perioperative hemodynamic stability.

• Hypokalemia - common in patients on diuretics

- to be correct preoperatively.

2. Ischemic Heart Disease Patients :

• Objective of premedication – optimum sedation and anxiolysis without undesirable ventilatory and circulatory depression.

• Anticholinergic mainly atropin to be avoided.

• One useful combination is morphine 10 – 15 mg. IM + hyoscine 0.4 – 0.6 mg IM.

• Aspirin to be discontinued 7 days before surgery.

3. Rheumatic Heart Disease Patients :

• Premedication should decrease anxiety and associated adverse circulatory response

• Patients are more susceptible to depressant effect of sedative drugs

• Prophylactic antibiotics should be considered

• Antcholinergics better avoided

• Patients on anticoagulant therapy- warfarin should be substituted by heparin 3-5 days prior sx

4. Patients with COPD and Asthma :

• Bronchodilators , steroids should be continued

• Prophylactic antibiotics in COPD patients

• Opioids to be used cautiously – respiratory depression, bronchoconstriction

• Anticholinergics should be individualized – dries secretion difficult to remove

• NSAIDS should be avoided

5. Diabetes mellitus:

• Objectives-

Avoid hypoglycemia , excessive hyperglycemia , ketoacidosis

Blood glucose should be maintained 120-180m

• OHD to be avoided on day of surgery

• Premedication to avoid aspiration and nausea vomiting

PREMEDICATION IN OBSTRETIC ANAESTHESIA

• Patients are at risk of aspiration due to –

Progesterone delays gastric emptying

Gravid uterus

Drugs esp opioids

• Opioids and BZD may cause adverse effect on neonate

• Amnesia – woman may not be able to remember her birthing experiences

PREMEDICATION IN OUTPATIENTS PREMEDICATION IN OUTPATIENTS SURGERIES SURGERIES

• Aims and objectives are similar, care to be taken not to prolong recovery of patient

• Short acting benzodiazepines medazolam commanly used

• Short acting opioids such as fentanyl, sufentanyl are preffered

• Alpha 2 agonist can be used

• NSAID on fixed dosing schedule may reduce intra op opioid requirement

• Premedication to avoid aspiration and nausea , vomiting

o 5HT 3 antagonist are most effective

o Droperidol less than 10 umg/kg cost effective

o Phenothiazines to be avoided

PREMEDICATION IN PAEDIATRIC PATIENTS

• Premedication in infants-

•Infant less than 6 months don not require sedative premedication

•Antisialogouges no longer required in neonate

• Aim is to obtund vagal reflexes

• Premedication in children-

• Aims –

• To get calm and comfortable child in operating room

• To decrease secretions

• To obtund vagal reflexes

• To avoid post op. behavioral disturbances

• Considering fear for needles , routes other than im / iv prefered

1.Sedatives and hypnotics-

Midazolam- most commanly used

0.5-0.75mg/kg orally 20 mins prior

0.2-0.3mg/kg intrnasal

0.4-0.5mg/kg per rectally

Temazepam- 0.5 mg/kg orally

Chloral elixir- 35mg/kg orally

Trichlophos- 75-100mg/kg orally

Methohexital-20-30mg/kg rectally

2. Analgesics-

Paracetamol syrup-5-10mg/kg

10-15mg/kg rectally

Diclofenac- 1.5mg/kg rectally

3. Opioids-

OTFC-in the form of lollypop

controlled dosing

onset 20-30mins

high incidence of pruritus and nausea vomiting

Pethidine-1-2mg/kg im

Morphine-o.1-o.2mg/kg im

4. Ketamine-

6mg/kg orally

3mg/kg intranasally

3-5mg/kg im

5. Anticholinergics-

Preffered in oral surgeries , ocular surgeries , along with ketamine

Atropine- 0.02mg/kg im/iv

glycopyrrolate-50ug/kg orally

4-8ug/kg im/iv

Don’t significantly reduce laryngeal reflexes during intubation. However they reduce incidence of hypotension during induction.

6. Antiemetics-

Droperidol- 0.05-0.1mg/kg

Ondansetron- 0.1mg/kg

Promethazine- 0.5mg/kg

Every route of drug administration has its own drawback