Pre-Operative Testing د. صباح نوري السعد M.B.Ch.B, D.A, F.I.M.S, C.A.B.A & I.C

Pre-Operative Testing Haemoglobin: History of or anticipated blood loss, major surgery, cardio-respiratory diseases, routinely for female patient. Blood Urea, Serum Creatinine & Serum Electrolytes: Hypertension, heart failure, renal failure, major gut or urological surgeries, diabetic patient, diuretic therapy. Urine Exam: urinary tract infection, diabetes mellitus.

Pre-Operative Testing Chest X-Ray: Heart failure, pulmonary disease with localising sign, hypertension, other cardiac diseases.

Pre-Operative Testing Electrocardiography (ECG): Arrhythmia, angina pectoris, history of myocardial infarction, hypertension, heart failure.

Pre-Operative Testing Thoracic Inlet X-Ray: Thyroid enlargement. Pulmonary Function Test: Asthma, chronic obstructive airway disease, thoracic surgeries. Liver Function Test, Albumin, Bilirubin: Liver disease, alcoholics. Coagulation studies: Liver disease, anticoagulant drugs, plan for spinal or epidural anaesthesia. Echocardiography: Heart failure, congenital heart diseases, valvular heart diseases.

Special Situations Day-Case-Surgery: Patient can be discharged home few hours after operation. Patient criteria for day-case-surgery: Otherwise completely fit patient, or have minor, well-controlled condition. Has undergone proper pre-operative assessment (regarding history, physical examination, and testing). Has undergone a proper period of starvation. Has a responsible adult to act as an escort home and for overnight supervision. The patient must be advised not to drive or operate machinery for 24 hours.

Emergency Surgery The patient general medical condition should be ascertained. In the case of abdominal emergencies or acute haemorrhage, a period of resuscitation may be required to restore circulating volume and/or extracellular fluid, because anaesthesia whether general or regional is hazardous in hypovolemic patient, so it is usual to complete rehydration and resuscitation before surgery takes place. Requirement for fluid resuscitation may be easily gauged by the clinical approach:

Tachycardia, hypotension, cool peripheries, low urine output → low circulating volume. Breathlessness, raised jugular venous pressure, and basal crepitation → excessive fluid replacement. Clinical judgement can be supported by central venous pressure (CVP) measurement. N.B: only in cases of ongoing blood loss (e.g. trauma, rupture ectopic gestation, leaking aortic aneurysm), speed is important, and resuscitation must proceed at the same time as surgery and anaesthesia.

Fasting For elective surgery: Non Per Os (NPO, nothing by mouth) from midnight for patient having operation in the morning, while patient having operation in the afternoon have been thus starved from 7:00 a.m. For emergency surgery: starvation depends on the urgency of the case.

Premedication: Premedicants: drugs that are given in the surgical ward mainly to allay patient fear and anxiety (like benzodiazepines orally or intramuscularly) or to relief pain like morphine. Other drugs: Antiemetics: metoclpramide, ondansetron H2-receptor antagonist Transdermal glyceryl trinitrate patch Steroids Atropine Heparin Antihypertensive, anti-ischemic, anti-epileptics

Local and Regional Anaesthesia Local: normally means the use of a drug to produce anaesthesia by topical, infiltration or ring block. Regional: a term reserved to describe major nerve blocks, spinal and epidural techniques.

Loco-Regional anaesthesia versus General anaesthesia: Advantages: Avoids adverse effects of general anaesthetic agents like, respiratory depression, cardiovascular depression, nausea and vomiting, and hangover. Avoids potential hazards of unconsciousness: ●loss of airway, ●aspiration of gastric contents, ●damage to joints, skin, etc through malpositioning. Minimize endocrine stress response to surgery. Decreased post-operative pain. Earlier discharge from hospital.

Disadvantages: Toxicity of local anaesthetics Often difficult techniques: failure, partial success, more discomfort while performing block, may take longer time to establish anaesthesia. Greater cooperation needed from patient. Sets time limit for surgery. Restricts surgeon flexibility if operation needs to be more extensive.

Topical Anaesthesia Rapid absorption of local anaesthetic from mucous membrane → rapid rise of plasma concentration. (e.g. application of local anaesthesia to the mucous membrane of pharynx, larynx, urethra). Nowadays topical anaesthesia for skin by EMLA (Eutectic Mixture of Local Anaesthetics).

Infiltration anaesthesia: Subcutaneous infiltration of local anaesthetic 1cm from the edge of a wound (elliptical infiltration), or subcutaneous infiltration of an area covering superficial masses.

Most commonly used local anaesthetic Lidocaine (xylocaine) 1% or 2%, 1% solution → 1g/100ml or 10mg/ml, which is fair enough for infiltration Maximum safe dose: 3mg/kg (plain solution) 7mg/kg (with adrenaline) N.B: Adrenaline added to local anaesthetics to: local vasoconstriction → less systemic absorption (less toxicity), and more prolonged effect of local anaesthesia. But addition of adrenaline is contraindicated in areas supplied by end arteries: fingers, toes & penile block → irreversible pharmacologic tourniquet → gangrene.

Other local anaesthetic is Bupivacaine (Marcaine ®) 0. 125%, 0 Other local anaesthetic is Bupivacaine (Marcaine ®) 0.125%, 0.25% and 0.5%, maximum dose: 2mg/kg (plain solution). Its onset is slower than lidocaine, but has longer duration. Ring Block: Circumferential infiltration of a digit or toe proximal to the wound (without adrenaline).

Local Anaesthetic Toxicity: Causes: Inadvertent intravenous injection of local anaesthetic. Local anaesthetic infiltration with an amount that exceeds maximum safe dose. Signs & Symptoms of local anaesthetic toxicity: Central Nervous System Paraesthesia especially around the mouth. Anxiety Tremor Fitting Coma Cardiovascular System Bradycardia Fall in cardiac contractility → hypotension Cardiac arrest

Management: Support for ventilation and circulation with close monitoring. Diazepam or small dose thiopentone to control fit. Coma and cardiac arrest → Proper cardiopulmonary resuscitation.