Transcript Preoperative Evaluation And Preparation For Anesthesia

PRE-OPERATIVE
PRE - MEDICATION
Pre-medication
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Pre-medication is the administration of drugs before
anesthesia.
Pre-medication is used to prepare the patient for
anesthesia and to help provide optimal conditions for
surgery.
Premedication used for the following reasons:
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Reduction of anxiety and pain.
Promotion of amnesia.
Reduction of secretions.
Reduction of volume and pH of gastric contents (to
avoid Mendelson’s Syndrome).
Reduction of postoperative nausea and vomiting.
Enhancing the hypnotic effects of general anesthesia.
Reduction of vagal reflexes to intubation.
Specific indications, e.g. prevention of infective
endocarditis
Premedication
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Premedication is usually given 1-3 hours preoperatively.
Topical anesthetic creams are often prescribed for
children before cannulation.
Taking Prescribed Medications and
Premedication
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Prescribed medications, especially pre-medication can
be taken within the 2 hours prior to surgery with a
small drink of water (<30 ml).
Some medications may be omitted prior to surgery as
a result of other protocols e.g. ACE inhibitors, warfarin
and oral hypoglycaemic agents.
Analgesic drugs should not normally be omitted due to
fasting as pain may prolong gastric emptying times.
Premedication
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The practice of premedication has changed
substantially in recent years.
The use of strongly sedative drugs,
e.g. morphine and hyoscine, to aid smooth induction
and reduce salivation has been abandoned with:
The advent of modern intravenous and inhalational
anesthetic agents, which fewer side-effects and faster
action
Increasing use of day-case surgery
Same-day admissions – patients often do not find a
bed until just before surgery
Changes to the surgical list, making the timing of drug
delivery difficult
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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
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anxiety
Benzodiazepines are ideal agents to reduce anxiety.
They provide anterograde amnesia and light sedation.
Relieving anxiety and sedation may also be achieved
by morphine, pethidine, fentanyl citrate.
In children, oral antihistamines e.g. alimemazine.
Premedication for amnesia
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Especially useful in the young age group or those having
repeated general anesthetics.
The most effective agents are lorazepam and
midazolam.
Premedication for analgesia
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Opioids ,paracetamol and NSAID drugs * reduce the required dose
of anesthetic agent and * improve patient comfort in the immediate
postoperative period.
Opioids are the drugs of choice in the presence of acute pain.
Opioids also cause variable sedation and cardiorespiratory
depression.
S/E :
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All opioids cause nausea and vomiting and this may outweight any
beneficial effects. Opioids may also precipitate bronchospasm
or anaphylaxis.
Premedication for Antivagal
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effects
Response to surgery often includes vagally
mediated bradycardia
Antisialagogues (e.g. glycopyrrolate IM or IV)
are rarely needed but may be indicated for:
*awake fiber-optic intubation or *before ketamine anesthesia
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However, antisialagogues cause unpleasant dry mouth.
Hyoscine is the most potent agent available with the added
advantage of amnesia and sedation. However, it can cause
significant preoperative confusion in elderly patients.
Premedication for antiemetics
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They are used either to reduce the emetic effects of
anesthetic agents (antihistamines, butyrophenones,
hyoscine) or to enhance gastric emptying
(metoclopramide).
Those with a risk of regurgitation of gastric contents or
undergoing procedures with a high incidence of nausea
and vomiting, e.g. laparoscopy, should receive agents to
reduce gastric acidity
Can use H2-receptor antagonist or proton pump
inhibitors several hours preoperatively and oral sodium
citrate 15-30 minutes before induction.
Preoperative management of Anticoagulation
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Surgery on patients on long-term oral anticoagulation,
the major concern is when it is safe to perform surgery
without increasing the risk of hemorrhage or increasing
the risk of thromboembolism (venous, arterial) after
discontinuing oral anticoagulation therapy.
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Most patients can undergo dental extractions, arthrocentesis,
biopsies, ophthalmic operations and diagnostic endoscopy without
alteration of their regimen. For other invasive and surgical
procedures, oral anticoagulation needs to be draw
Invasive surgery is generally safe (from major hemorrhagic
complication) when the INR ~1.5.
It takes approximately 4 days for the INR to reach 1.5 once oral
anticoagulant is stopped preoperatively.
It takes approximately 3 days for the INR to reach 2.0 once oral
anticoagulant is restarted postoperatively.
If oral anticoagulant is held 4 days pre-op and started
immediately post-op, the patient is, in the mean time, without
anticoagulation for 2 days (24 hours preop and 24 hours post-op).
Management recommendations
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If INR pre-op is 2-3, stop oral anticoagulant 4 days prior
to surgery (or longer if INR > 3.0).
one day before:
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Measure INR one day prior to surgery: if it is ≥ 1.7, give 1
mg vitamin K (SC) .
Day of surgery :
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If on the day of surgery the INR is 1.3-1.7, administer 1
unit of fresh frozen plasma and administer 2 units if the INR
is 1.7-2.0.
The following approaches can be used: administer full-dose
anticoagulation with IV unfractionated heparin (UFH);
administer full-dose anticoagulation with LMWH; or
administer prophylactic doses of UFH or LMWH.