PRE-OPERATIVE PRE - MEDICATION

Pre-medication  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:  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  Premedication is usually given 1-3 hours preoperatively.  Topical anesthetic creams are often prescribed for children before cannulation.

Taking Prescribed Medications and Premedication  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  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: 1) The advent of modern intravenous and inhalational anesthetic agents, which fewer side-effects and faster action 2) Increasing use of day-case surgery 3) Same-day admissions – patients often do not find a bed until just before surgery 4) 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  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  Especially useful in the young age group or those having repeated general anesthetics.  The most effective agents are lorazepam and midazolam.

Premedication for analgesia  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 :  All opioids cause nausea and vomiting and this may outweight any beneficial effects. Opioids may also precipitate bronchospasm or anaphylaxis.

Premedication for Antivagal 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  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  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 minutes before induction.

Preoperative management of Anticoagulation  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.

1) 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 2) Invasive surgery is generally safe (from major hemorrhagic complication) when the INR ~1.5. 3) It takes approximately 4 days for the INR to reach 1.5 once oral anticoagulant is stopped preoperatively. 4) It takes approximately 3 days for the INR to reach 2.0 once oral anticoagulant is restarted postoperatively. 5) 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  If INR pre-op is 2-3, stop oral anticoagulant 4 days prior to surgery (or longer if INR > 3.0). one day before:  Measure INR one day prior to surgery: if it is ≥ 1.7, give 1 mg vitamin K (SC). Day of surgery :  If on the day of surgery the INR is , administer 1 unit of fresh frozen plasma and administer 2 units if the INR is  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.