Preoperative Preparation
د. صباح نوري السعدM.B.Ch.B, D.A,F.I.M.S, C.A.B.A & I.CPreoperative Preparation Introduction: Aims of the preoperative visitTo ensure that the patient is presented for theatre in an optimum state.It offers an opportunity to discuss the anaesthetic technique with the patient.To minimize the patient anxieties.To prescribe premedication
Patient Assessment
I.Cardiovascular System: 1.Coronary Artery Disease:The role of exercise toleranceThe role of Cardio-Pulmonary Exercise Test (CPET)Stable AnginaUnstable AnginaPrevious Myocardial Infarction2.Cardiac Failure:Careful assessment especially if the patient has basal crepitations or Gallop rhythm.I.Cardiovascular System: 3.Arrhythmias:History of palpitation or stokes-Adams attacksInfrequent ectopics are rarely significant unless associated with electrolytes imbalance, or thyroid disease.Usually diagnosed accurately by ECG.Certain arrhythmia requires control or correction before operation, e.g. rapid atrial fibrillation (AF), or 2nd and 3rd degree heart block.
I.Cardiovascular System: 4.Hypertension: Hypertension should be treated before operation:Patients who have their diastolic blood pressure persistently exceeds 110 mmHg require control before operation.Mild-moderate hypertension require control if hypertension is associated with end-organ damage.Hypertensive patient on treatment but still their hypertension not adequately controlled.All antihypertensive medications should be continued up to including the day of surgery.
II.Respiratory System: 1.Upper Airway: Lips – TracheaMouth OpeningPresence of diseased teeth or denturesCervical spine mobilityThyro-mental distance
II.Respiratory System: 2.Chronic Obstructive Airway Disease (including Asthma)Severity of the disease can be assessed by: exercise tolerance, current medication, frequency of hospital admission.Physical signs such as cyanosis and wheezes are important in more severe diseaseChest X-Ray although routinely taken but rarely helps.Pulmonary Function Test (PFT) is usually performed, Peak Expiratory Flow Rate (PEFR).Patient with severe disease requires early admission.Local and Regional Anaesthesia is preferred.
II.Respiratory System: 3.Upper and lower respiratory tract infectionsElective surgery should be delayed; otherwise life-threatening respiratory tract infection may develop post-operatively.
III.Endocrine Diseases: 1.Diabetes Mellitus:Usually they have cardiovascular and renal diseases.The most common practical problem is the management of diabetes mellitus during inevitable period of starvationRandom Blood Sugar (RBS) below 15 mmol/L is acceptableGeneral principles of management under General Anaesthesia:Hypoglycaemia must be avoidedRegular measurements of random blood sugar is importantInsulin-Dependent diabetics require insulin even during starvation and they require more insulin than usual.Non-Insulin-Dependent diabetics may require insulin for a brief period.
A suggested scheme for management of diabetic patient undergoing elective surgery: Type of Diabetes Minor Surgery Major Surgery 1. Diet controlled Measure blood sugarRarely require treatment Measure blood sugarRarely require insulin 2. Oral treatment Measure blood sugarOmit treatment 12-24 hours before operation Measure blood sugarOmit treatment 12-24 hours before operation Both groups may require insulin after operation 3. Insulin-dependent For both operation: measure blood sugarinsulin (injection or infusion) + 5% dextrose infusion (together or separately)
III.Endocrine Diseases: 2.Thyroid Disease:Patient with thyroid disease should have Thyroid Function Test before elective surgery.Uncontrolled hyperthyroidism Thyroid CrisesMyxoedema Delayed Recovery and Heart FailureClinical judgement and high index of suspicion is important.
IV.Neuromuscular System: 1.Epilepsy:Avoid anaesthetic drugs which are suspected of being epileptogenic (Ketamine)Continue anticonvulsant medications including the day of surgery, and as soon as possible post-operatively.2.Lower Motor Neuron disease:Altered response to suxamethonium → hyperkalemia
IV.Neuromuscular System: 3.Myasthenia Gravis: assessment of severityHighly sensitive to non-depolarizing muscle relaxantsPlanning for post-operative intensive care unit (ICU) admission and possibly mechanical ventilation.4.Malignant Hyperthermia:Runs in familiesHypermetabolic stat of skeletal muscles is triggered hyperthermia and electrolyte imbalance.5.Stroke:There is no post-stroke “Risk Period”It makes sense not to undertake elective surgery during recovery from strokeGood control of hypertension
V.Genito-urinary System: 1.Renal Failure:The pathophysiology of Renal Failure whether acute or chronic is complexChronic renal failure:Hypertension, cardiomyopathy, pericardial effusionAnaemia and platelet dysfunctionImpaired Blood-Brain barrier (highly sensitive to opioid analgesics especially Morphine).Fluid and Electrolyte imbalanceDialysis may be required before operation.
V.Genito-urinary System: 2.PregnancyElective surgery is contraindicatedEarly pregnancy → Teratogencity of anaestheticsLate pregnancy → Premature labour
VI.Haematological System: 1.Anaemia: Lowest Hemoglobin for elective surgery is 10 mg/dL except chronic renal failure patients.2.Clotting Disorders: Chronic liver disease, primary haematological disease, or drug (warfarin).
VII.Concurrent drug treatment:these might interact with anaesthetic drugs; Drug Effect A. Cardiovascular system: 1.Potent antihyperensives,e.g. β-Blockers, ACE Inhibitors → Enhance hypotensive effect of general anaesthesia or spinal anaesthesia 2.Antiarrhythmics,e.g. Digoxin, amiodarone → Increased risk of bradycardia ± significant myocardial depression, digoxin may cause significant arrhythmia 3.Diuretics,e.g.thiazide,spironolactone → Dehydration ± electrolyte imbalance 4.Anticoagulant, e.g. warfarin → Major regional block contraindicated
Drug Effect B. Respiratory system: Bronchodilators, e.g. Aminophylline → Increased likelihood of arrhythmia C. Central Nervous System: 1.Sedative and hypnotics →Chronic use induce tolerance to general anaesthesia 2.Monoamine Oxidase → Interact with sympathomimetic (ephedrine), and pethidine to cause hypertension and tachycardia → Fatal 3.Antiparkinson drugs → Levodopa increase risk of arrhythmia 4.Antiepileptics → Increase tolerance to general anaesthesia
Drug Effect D. Drug of abuse 1.Tobacco → Reduce O2 carriage capacity by formation of Carboxyhemoglobin (COHb)Major Factor in chronic obstructive airway diseaseMay induce tolerance to general anaesthetics 2.Alcohol → Tolerance to anaestheticsChronic use may cause cirrhosis and cardiomyopathy 3.Intravenous drug abuse → Tolerance to effects of opioidsRisk of hepatitis and AIDSMay have difficult veins
Drug Effect E. Steroids: glucocorticoids → currently or in the previous 6 months cause adrenocortical suppression F. Oral Contraceptive Pills (OCP) 1.Oestrogen-containing OCP → Deep venous Thrombosis and pulmonary embolismN.B: Should be stopped 1 month before elective operation 2.Progesterone-only OCP → No effect G. Aspirin and Clopidogrel (Plavix) → Platelet dysfunction, better to be stopped at least 1 week before elective operation.In coronary stenting better not to stop clopidogrel E. Steroids: glucocorticoids → currently or in the previous 6 months cause adrenocortical suppression