Pre-operative Management Pre-operative Assessment
"People don't die of their diseases: they die of the pathophysiological effects of disease." Sir William Osler 1897.
Pre-operative assessment should aim to identify risk factors which could be optimised to minimize complications, improve outcome and ensure patient safety and comfort.
AIMS
. Establish rapport the patient and family, and allay anxiety.
Assess functional status, optimise and balance risk and benefit.
Plan peri-operative management according to the risk factors. Explain all procedures, establish communication and obtain informed consent.
HISTORY
Vital and most informative and cannot be substituted for by investigations
Age : biological age is more important than chronological age
Profession, lifestyle, effort tolerance and metabolic equivalents (see page 10.1)
Presenting complaint, its complications and surgery planned
Current and past medical diseases, drug therapy, sepsis, allergies Coagulopathy: gum bleeding, bruises, knee swellings
. Menstrual and obstetric history Previous anaesthesia, date and nature of surgery and complications
Family history of medical illnesses, anaesthetic complications Social habits : smoking, alcoholism, drugs, high risk behaviour
SYSTEM REVIEW
Nutrition
CVS
RS
CNS
Liver
Kidney
Oral
GIT
: appetite, weight loss / gain, malnutrition, oedema, obesity : chest pain, dyspnoea, palpitations, syncope, oedema
: cough, sputum, snoring, dyspnoea, tachypnoea, wheeze
: headache, convulsions, strokes, blackouts, sleep, gait : jaundice, ascites, encephalopathy, hepatitis, cirrhosis
: oliguria, polyuria, nocturia, hacmaturia : dentures, caps, crowns, bridges, loose teeth, gums, sepsis
Endocrine
Haematology
Musculoskeletal
EXAMINATION
: diabetes, thyroid, adrenocortical disease
: anaemia, coagulopathy
: arthritis, myopathies, facial and spinal deformities
System based examination specially RS, CVS and those indicated by review. Special : Airway, spine, venous access, varicose veins, skin, nerves, joints
INVESTIGATIONS
Investigations should be ordered on the basis of history and examination:
For diseases suspected / detected on clinical assessment or as base line
For vital organ function which maybe compromised by surgery
Consider its value: Will it reveal information not obtained by examination? Will the results alter management of the patient?
Guidelines for investigations
Urine analysis : Ward test for sugar, blood, protein, for all patients
Full blood count : All females, males > 40 years, major surgery, suspected anaemia, If expected to exceed "allowable blood loss" (see page 23.12) Bleeding, pallor, coagulopathy, infection, vital organ dysfunction
: with antibody screen for surgery likely to require red cell transfusion Renal profile : Diarrhoea, vomiting, metabolic disease, diabetes, anaemia
Blood grouping
(serum creatinine, electrolytes and
blood urea)
Renal, CVS or hepatic disease, long term i.v. therapy Drugs (diuretics, digoxin, antihypertensives, steroids) Major surgery with expected large fluid shifts
Chest X-ray and : CVS or RS disease, thoracic surgery
Spo,
ECG
Echocardiogram
Blood sugar
Risk of tuberculosis or malignancy
: Males >40 years, females postmenopausal Cardio-vascular disease, hypertension, diabetes : Cardiac symptoms, signs, BMI>35, hypertension, DM.
: Age >40 years, obesity, chronic wounds Glycosuria, known diabetic or family history Cardio-vascular disease, steroid therapy
Coagulation screen : Bleeding disorder, anticoagulant therapy, liver disease
Liver function
: Jaundice, alcoholic, hepatic disease, renal or cardiac failure Abnormal nutritional status or metabolic disease
Lung function : Chronic respiratory disease, thoracotomy Arterial blood gas: Abnormal lung function
Unexplained tachypnoea (possible metabolic acidosis)
Pregnancy test : Whenever there is a possibility of pregnancy
: gastric stasis, heart burn, vomiting, bowel habits
RISK STRATIFICATION OF PROBLEMS IDENTIFIED
1. Patient risk factors
What risk factors will lead to a poor outcome? Is pre-operative optimisation needed and possible? Should surgery be delayed and for how long? What specific goals may be achieved with optimisation?
2. Surgical requirements
Surgical access : intubation, shared airway, positioning required Minimizing bleeding : position, IPPV, hypotensive agents, adrenaline Special problems : increase of intra ocular pressure, intra cranial pressure, CO, (laparoscopy)
3. Anaesthetic problems
"Full stomach", difficult / shared airway, high risk patient Optimal technique, drugs, monitoring, and post-operative care to be planned
considering the surgery, patient problems, and possible complications leading to mortality and morbidity
RISK ASSESSMENT
Is the patient in optimum physical condition for anaesthesia? Are the benefits of surgery greater than the anaesthetic and surgical risks?
Procedure following risk assessment :
Medical disease : institute or optimise appropriate therapy Discuss with surgeon : timing of surgery, pre-operative treatment
Discuss with consultant postponement of surgery, ICU care
CAUSES OF PERI-OPERATIVE MORBIDITY AND MORTALITY
The overall post-operative mortality is about 1%. Direct anaesthetic deaths are about 1:100,000 in ASA I and II patients.
The common causes of death and the high risk factors should be recognised operatively and prophylactic measures instituted.
Haemorrhage
Sepsis
Deep vein thrombosis and pulmonary embolism
Myocardial infarction
Pneumonia
Emergency surgery outside normal working hours by inexperienced juniors
ASA PHYSICAL STATUS
The American Society of Anaesthesiologists (ASA) classification does not emb. aspects of anaesthetic risk, but is internationally applied for all surgical patient
ASA PHYSICAL STATUS SCA
ASA 1 : A normal healthy individual (No organic, biochemical or psychiatric disea
Surgical problem localize
ASA 2 : Mild systemic disease with no limitation of activity (mild asthma, diabetes, hypertension, obesity, anaemi
ASA 3 : Moderate disease with functional limitation (myocardial infarction with complications, angina, COP
ASA 4 : Severe systemic disease - a constant threat to life (unstable angina, cardiac, hepatic or renal failur
ASA 5 : Moribund patie
(expecting high mortality <24hrs with or without surgery) ASA 6 : Brain dead don
(awaiting organ retrieval) E : Emergency surgery (haemorrhage, head injur
Pre-operative Optimizati
Anaesthesia for routine surgery is contraindicated in the followin
Chronic uncontrolled medical diseases (cardiac failure, hypertension, diabetes, asthma, COPD, hepatic and renal diseas
Acute illness (myocardial infarct within 3 months, wheezing, severe respiratory infection, viral hepatitis, influenza, etc
Inadequate fasting period (< 6h for solid
High risk patients must be identified before surgery, and medically optimised to reduce morbidity and mortalit
This requires assessment preferably some days or even weeks before planned surgery, and as soon as possible before emergency surger
Treat identified problems and optimise all disease medication. Commence chest physiotherapy, dental treatment etc where appropriat
Check need for and availability of bloo
Check need for and availability of ICU bed
d.d.e.y.y.s).)e)g:ony)ornte)D)a)d)seLEs.ck need for and availability of ICU bed.
Premedication
"That which cannot be easily treated had better be prevented." Alfred Lee. Medication should be individualized to the patient and risk factors.
1. Anxiolytic
Building a rapport with the patient is the best anxiolytic. Drugs needed specially for cardiac, hypertensive, asthmatic patients. Caution in extremes of age, renal and hepatic failure. e.g. diazepam or midazolam. Use lorazepam in the elderly.
2. Amnesic
To avoid 'awareness' specially with minimal anaesthesia e.g. midazolam, lorazepam in trauma, cardio pulmonary by pass surgery etc.
3. Anti sialogogue
To reduce secretions in oral surgery, in the mentally handicapped e.g. atropine, glycopyrrolate
4. Autonomic suppression
Vagolytic (atropine) for dilatations, squint and retinal surgery, children Beta blocker for hypertension, IHD, and hypotensive anaesthesia
5. Analgesic
Paracetamol, NSAIDs, tramadol (unless regional analgesia is planned)
EMLA patch (1 hr before) or ametop (20 min before)
6. Antiemetic/Prokinetics
Patient : migraine, motion sickness, obesity, young, females, cyclic with menstruation, prolonged fasting, full stomach Surgical : gynaecological, ENT, eye, laparoscopy, chemotherapy Anaesthetic: opiates, N, O, thiopentone, ketamine, gas in stomach
Give metoclopramide (for most), promethazine (for opiates), ondansetron and dexamethasone for chemotherapy or if resistant.
7. Acid aspiration prophylaxis
Risk of aspiration, acidity (pregnancy, obesity, heartburn, etc) Give ranitidine, metoclopramide, sodium citrate
8. Anti thrombotic : DVT prophylaxis (see page 1.7)
9. Adrenal cover : steroids (see page 8.19)
10. Antibiotic prophylaxis : heart disease, contaminated surgery, prosthetic implants, immunocompromised. (see page 10.14)
11. Anti disease medication : antihypertensives, bronchodilators etc
Pre-operative Modification of Patient's Drug Therapy
10
Aim To obtain best optimisation and stability peri-operatively To ensure reversibility and quick control, change to drugs with shorter half lives To minimize withdrawal, side effects, and drug interactions To modify drug, dose, route and anaesthetic for best outcome
Stop • Oestrogens (DVT risk) for 4 weeks pre and post surgery (may continue if ambulatory, minor operations, or low dose)
• ACE inhibitors and angiotensin receptor inhibitors for 24 hours
• Clopidogrel for 7 days
Change • MAOI : pargyline, phenelzine, tranylcypromine, isocarboxacid Danger with pethidine, ephedrine (hypertension, fits, coma)
• Tri -cyclic anti-depressants block reuptake, cause tachyarrhythmias Danger with ephedrine, halothane, ketamine, and pancuronium
• Potassium sparing diuretics cause hyperkalaemia
Danger with muscle injury, burns, renal disease, suxamethonium
Warfarin : stop for 3 days, convert to heparin, if needed • Aspirin : stop for 7 days, but weigh risk / benefit (TURP high risk)
Continue Beta blockers, Ca blockers, clonidine, to avoid hypertensive crises
• Anti-anginal therapy to prevent ischaemia
• Bronchodilators to prevent bronchospasm
• Steroids to prevent adrenal crisis
Anti epileptic therapy to avoid seizures
Sympathomimetics cause hypertension, tachycardia, arrhythmias. Enzyme inhibitors (cimetidine) may prolong action of opiates,
benzodiazepines, theophylline, LA, beta blockers, anti-coagulants.
Enzyme inducers : Na valproate, barbiturates, phenytoin, carbamazepine
• Suxamethonium prolonged with ecothiopate, neostigmine, chemotherapy.
Non-depolarizers prolonged with aminoglycosides, Ca antagonists, Mg, immunosuppressives, anti-arrhythmic drugs.
Amiodarone may cause 3rd degree heart block. Diuretics causes hypovolaemia and hypokalaemia.
• Lithium causes hypokalaemia. Digoxin toxicity with hypokalaemia • Anti-epileptics may have drug interactions due to enzyme induction.
Venous Thrombo-Embolism and Thromboprophylaxis
11
Individualize prophylaxis balancing the risk of thrombosis vs the risk of bleeding
Risk of thrombosis : admission related (surgical and trauma patients)
Total surgical time >90 min or for pelvic and lower limbs >60min Acute surgical admission with inflammatory or intra abdominal condition
Expected to have significantly reduced mobility for >3 days
Critical care admission, or hip or knee replacement or hip fracture
Risk of thrombosis : patient related
Active cancer and cancer treatment
. Age>60 years
Critical care admission, dehydration, known thrombophilias
Obesity (BMI > 30kg/m2)
Co-morbidity (CVS, RS, metabolic, endocrine, infections, inflammations)
Personal history or first degree relative with a history of VTE
Use of hormone replacement or oestrogen therapy
Varicose veins with phlebitis
Pregnancy or <6 weeks postpartum
Risk of bleeding : patient related
Active bleeding
Bleeding disorders - acquired (liver failure) or inherited (haemophilia) Anticoagulation (eg. warfarin with INR >2) or platelets <75,000/ mm
Acute stroke or uncontrolled BP >230/120
Risk of bleeding : admission related
Neuro, spinal, eye, or other surgery with high risk of bleeding Lumbar puncture, SAB, EDB, within previous 4 hr or next 12 hrs.
Prophylaxis
. All patients : Ensure hydration, encourage mobility, consider SAB / EDB
Low risk : Use anti embolism stockings (thigh or knee length), foot impulse devices, or intermittent pneumatic compression devices
High risk : (hip, knee, cancer, abdominal, pelvic surgery) If low risk of bleeding, add drug therapy till mobilised (1-2 weeks) LMWH Enoxaparin 40mg s.c, 2h pre-op and daily for 1-2 weeks Fondaparinux 2.5mg s.c. 6h postop and daily (4 weeks for hip) Unfractionated heparin (UFH) 5,000u s.c. bd for patients in renal failure Monitor INR, fibrinogen. Avoid NSAIDs. Avoid i.m. injections. Antidote: protamine Img/lmg for UFH (<50mg) slow i.v. over 10min.
Pre-operative Fasting
"No solids; a cup of tea 2 hours before surgery." Joseph Lister 1883
AIM: The aim of fasting is to prevent pulmonary aspiration of gastric contents. Goals of fasting : To reduce gastric acidity (pH >3), and residual volume < 25ml
Danger of aspiration
Solids aspirated cause obstruction in large airways and collapse of the lung. Liquid aspiration causes pneumonia and possibly lung abscess. Acid aspiration (pH<2.5) causes chemical pneumonitis (Mendelson's syndrome).
PATIENTS AT HIGH RISK OF ASPIRATION
Uncooperative patients : Children, mentally deficient Delayed gastric emptying time : Fear, pain, opiates, labour, trauma (check last meal to injury time), diabetes, renal failure, head injury, pyloric stenosis Raised abdominal pressure : Pregnancy, obesity, tumour, distension, ascites
Increased acid : "heart burn", gastritis Increased reflux / regurgitation : Barrier pressure disrupted (increased intra
gastric pressure, relaxed lower oesophageal sphincter, hiatus hernia, lithotomy) Altered motility, vomiting : Acute abdomen, electrolyte imbalance, opiates Depressed laryngeal reflexes : acute alcoholism, low GCS
Drugs: Narcotics delay emptying, atropine relaxes lower oesophageal sphincter
At induction : Difficult airway, gastric insufflation, hypotension, hypoxia
SAFE FOOD FOR THE DAY OF SURGERY
Homogenous liquid of neutral pH (avoid acidic alcohol, apple, pineapple and milk) Iso-osmolar (not ribena), non-carbonated (to minimize gas in stomach) drinks High calorie, low fat food (avoid meats, fats which take >8h to empty) Low residue carbohydrates (avoid roughage, vegetables, carrots, peas)
TIMING OF FASTING PRIOR TO SURGERY
2 h : Clear liquid (water, king coconut water, plain tea, coffee) should be given up to 2h prior to surgery as it dilutes gastric acid and stimulates gastric emptying. Half life of water in stomach is only 10 minutes even in high risk patients.
4-6 h : Toast, plain biscuit, milk, maybe allowed in low risk patients 8 h : Avoid solid fatty meals on day of surgery to ensure 8h fast for heavy solids.
Disadvantages of fasting : Thirst, dehydration, hunger, hypoglycaemia, increased gastric acidity, PONV