fwd: bambury tutorial on preop assessment

Preoperative care

Ms. Niamh Bambury

05/02/09

Overview Nutrition Fluids and electrolytes Anaesthetic review Preoperative care Analgesic ladder Blood products Antibiotic prophylaxis Classification of wounds

Nutrition Essential for

Wound healing Immunological shield Maintaining normal functioning of organs

The fasting state After 12 hours of fasting the nutrients

provided have been utilised. Plasma insulin levels fall Glucagon levels rise

Glycogen is stored in the liver, muscle The liver converts glycogen into glucose Muscle glycogen is broken down into lactate,

exported to the liver and converted into glucose

The fasting state After 24 hours glycogen stores are

depleted and gluconeogenesis occurs mostly in the liver

Protein is broken into amino acids which undergo gng to form glucose

Fat is broken down into Glycerol-glucose Fatty acids-ketone bodies in the liver

Requirementsin the healthy person CHO and lipids are the mainstay of

energy intake 20-25kcal/kg/day Vitamins

metabolic co-enzymes co-factors in wound healing antooxidants

Requirementsin the healthy person Trace elements

Eg zinc, copper, iron cofactors for metabolic processes components of body tissues

Nitrogen-approx 12g/day- normally provided by protein

Changes in calorific needs Postoperatively-35kcal/kg/day Increases 10% per degree increase in

temperature Sepsis- 40-45kcal/kg/day Hypercatabolic states (burns, severe

pancreatitis)-60kcal/kg

Assessing nutritional status

Body Weight and anthropometric techniques

Clinical Laboratory techniques

Body Weight and anthropometric techniques Body weight (loss of 10% of BW in preceding 6

months is an indicator of poor clinical outcome) Triceps skin fold thickness(body fat mass) Mid-arm muscle circumference(muscle mass) Body mass index

BW in kg Height in m2• Note these values can be inaccurate in the

presence of oedema which occurs when there are changes in fluid balance in critically ill patients with fluid retention

Clinical assessment Clinical history- weight change, dietary intake Physical examination- muscle wasting, loss of

subcutaneous fat, oedema, alopecia Hand grip strength and respiratory function

assess functional impairment which is associated with undernourishment.

Laboratory techniques Serum albumin can be an indicator of

nutritional status However it is affected in the acute

phase response and by inflammation

(where it falls rapidly and therefore is of little use in assessing nutrition)

• U&E-Ca, Mg, PO4, Na, K

Feeding options Oral Enteral Parenteral

Enteral Feeding Requires GIT to be intact. Can be given NG, NJ, PEG, PEJ Indications

Dysphagia (esp for solid food) Major trauma/Surgery- when fasting will be

prolonged IBD(Short gut syndrome,Crohn’s,Pancreatitis) Distal low output enterocutaneous fistulae Oesophagogastric surgery.

Enteral feeding Monitoring of patients on enteral feeding

Clinical assessment Daily weights Fluid balance Twice weekly electrolytes and trace

elements

Enteral Feeding Complications

Malposition of the tube itself Aspiration Fistula formation Peritonitis Tube blockage Feed intolerance Hyperglycaemia Enteric infection

Parenteral Feeding Definition; the delivery of essential

nutritional requirements intravenously usually through a central venous catheter or PICC.

Used in intestinal failure where there is an inability of the GIT to absorb nutrients.

Parenteral Feeding Indications

Proximal intestinal fistulae Massive intestinal resecton especially

<100cm of bowel left. Severe pancreatitis Prolonged ileus

Parenteral Feeding Contents of TPN

>50% CHO 40% fat emulsions 1-2g/kg of fat/day H2O 35ml/kg/day Electrolytes-Na, K, Cl, Ca, Mg, PO4 Nitrogen Vitamins ADEK B&C

Parenteral Feeding Monitoring patients on TPN

Weight U&Es, FBC, LFTs Glucose Temperature and Vitals(signs of sepsis) Daily inspection of line Trace elements

Parenteral Feeding Complications

Line insertion Sepsis Pneumo/haemothorax Arterial damage/thrombosis Malposition of catheter Cardiac arrythmias

Parenteral Feeding Complications cont’d

Feed itself Metabolic derangement

TPN jaundice Hyper/Hypoglycaemia

Electrolyte disturbances Vitamin/Trace element deficiency

Anaesthetic review Suitability for surgery

Cardiac Respiratory

Need for blood products Type of anaesthetic GA versus spinal Post op analgesia required

Assessment of cardiac function

Non-invasive Chest x-ray ECG Echocardiography Exercise test

Invasive Coronary angiography Thallium scanning

Assessment of cardiac function Chest x-ray

indicated in the presence of cardiorespiratory symptoms or signs

Increased cardiac morbidity associated with Cardiomegaly Pulmonary oedema

Assessment of cardiac function ECG

features of ischaemia or previous infarction(LBBB) may be present

Stress test- if there are symptoms of IHD such as chest pain, SOB

on exertion 24-hour monitoring is useful in the detection and

assessment of arrhythmias

Assessment of cardiac function

Echocardiography Percutaneous Transoesophageal(TOE)

Allows assessment of Muscle mass Ventricular function / ejection fraction End-diastolic and end-systolic volumes Valvular function Segmental defects

Assessment of cardiac function

Nuclear medicine Myocardial scintigraphy allows assessment of

myocardial perfusion Radiolabelled thallium is commonest isotope used Areas of ischaemia or infarction appear as 'cold' spots

Assessing respiratory function Lung function tests

predict the type and severity of lung disease predict risk of complications and postoperative

mortality Arterial blood gases Radiological investigations

chest x-ray high-resolution thoracic CT

Lung Function Tests

Allow assessment of :1)Lung volumes2)Airway calibre3)Gas transfer

1)Lung Volumes

Assessed with spirometry Volumes measured include:

IC IRV TV VC FRC RV ERV TLC

2) Airway calibre

Assessed by Peak flow rates Flow rates measured

FVC = Forced vital capacity FEV1 = Forced expiratory volume in one

second Absolute values depend on height, weight, age,

sex and race FEV1 / FVC ratio is important

2) Airway calibre Lung function can be classified as:

Normal Restrictive Obstructive

Restrictive lung disease FVC is reduced but FEV1/FVC is normal

Obstructive lung disease FVC is normal or reduced and FEV1/FVC is

reduced

3)Gas transfer Measured by arterial blood gases (ABG) Also allow assessment of ventilation / perfusion mismatch Important parameters to measure are

pH Partial pressure of oxygen Partial pressure of carbon dioxide

Pulse oximetry gives an indirect estimate of gas transfer Technique is unreliable in the presence of other medical

problems (e.g. anaemia)

Assessment of Renal function Glomerular filtration rate is the gold standard test of

renal function Can be calculated by measuring creatinine clearance rate Requires 24-hour urine collection

Serum creatinine allows a good estimate of renal function may be inaccurate in patients with:

Obesity Oedema Pregnancy Ascites

Anaesthetic preview Medical co-morbidity increases the risks

already associated with anaesthesia and surgery.

American Society of Anesthesiologists devised a grading system to accurately predict morbidity and mortality

ASA Grade

Definition Mortality

1 Healthy individual 0.05

2 Mild systemic disease that does not limit activity

0.4

3 Severe systemic disease that limits activity but isn’t incapacitating

4.5

4 Incapacitating disease which is always life-threatening

25

5 Moribound 50

ASA grading

Cardiovascular disease- Angina, Hypertension, Diabetes. Grade 2-3

Respiratory disease- COPD, Asthma. Grade 2-3

Planning postoperative pain management. Postoperative pain management is

essential for a number of reasons Improved mobility Patient comfort Enhanced breathing Prevention of gut immobility

Analgesic Ladder Paracetamol NSAIDS Codeine phosphate Morphine Local anaesthesia

Analgesic ladder Paracetamol

inhibits COX3 useful for simple operations

NSAIDS used for moderate pain as an adjuvant with opiates in severe pain nonspecific COX inhibition leads to its side effects

especially loss of platelet function renal haemostasis and gastric cytoprotection

Analgesic ladder Codeine phosphate

does not have a significant respiratory effect

useful in intracranial surgery

Analgesic ladder Stronger analgesics IM morphine PCA

IV or via epidural catheter Patient controlled lock out time predetermined

Local analgesics continuous epidural anaesthesia with opiates or

local anaesthetics Spinal opiates

Fluid and electrolytes Managing fluids pre and postoperatively

essential

Fluid and electrolyte balanceDaily requirementsFor the ‘average’ 70 Kg man

Total body water is 42 L (~60% of body weight) 24L is in the intracellular and 14 L in the extracellular compartments The plasma volume is 3 L The extravascular volume is 11 L

Composition of crystalloids

Hartmann’s Solution

Normal Saline Dextrose Saline Sodium (mmol/l) 131 150 30 Chloride (mmol/l) 111 150 30 Potassium (mmol/l) 5 Nil Nil Bicarbonate (mmol/l) 29 Nil Nil Calcium (mmol/l) 2 Nil Nil

* Clinical history and observations – Pulse, blood pressure, skin turgor * Urine output – oliguria < 0.5 ml/kg/hr * CVP or pulmonary capillary wedge pressure * Response of urine output or CVP to fluid challenge * A fluid challenge should be regarded as a 200-250 ml bolus of colloid * This should be administered as quickly as possible * A response in the CVP or urine output should be seen within minutes * The size and duration of the CVP response rather the actual values recorded is more important

Fluid replacement 3 factors to consider

Maintenance requirements Abnormal losses Pre-existing deficits in fluids and

electrolytes

Fluid replacement Maintenance requirements Adults require approx 30-40mls/kg/day Children require considerably more

0-10 kg -100 ml/kg 10-20 kg -1000 ml + 50 ml/kg for each kg > 10 >20 kg -1500 ml + 25 ml/kg for each kg > 20

Fluid replacement Daily requirements

Sodium and potassium requirements are approx 1mmol/kg/day

Note that there is always a loss of potassium from faeces and urine so patients with diarrhoea can rapidly become hypokalaemic

Insensible losses

Faeces approx 100 ml/ day Lungs approx 400 ml/ day Skin approx 600 ml/ day Urine approx 1,500mls/day

Fluid replacement Abnormal losses

Nasogastric aspirate-rich in Na and K Vomit, diarrhoea Stoma, drains, fistula etc

Pre-existing fluid and electrolyte deficit Specific diseases- acute pancreatitis and SBO -

massive consumption of electrolytes and fluid

Assessing Fluid balance Vital signs-pulse,BP Urine output Dry mucosal surfaces Skin turgor Mental status Capillary return

Composition of crystalloids Hartmann’s Solution

Sodium 131 mmol/l Chloride 111 mmol/l Potassium 5 mmol/l

Normal Saline Sodium 150mmol/l Chloride 150 mmol/l Potassium 0 mmol/l

Sodium 131 mmol/l Chloride 111 mmol/l Potassium 5 mmol/l

Preoperative blood testing FBC U&E Coag screen Group and Hold

Coagulation tests Prothrombin time (PT)

extrinsic and common pathways measures factors II, V, VII, X and fibrinogen PT is expressed as International Normalised Ratio

(INR) Prolonged in:

Warfarin treatment Liver disease Vitamin K deficiency Disseminated intravascular coagulation

Coagulation tests Activated partial thromboplastin time (APPT)

Tests intrinsic pathways Prolonged in:

Heparin treatment Haemophilia and factor deficiencies Liver disease Disseminated intravascular coagulation Massive transfusion Lupus anticoagulant

Transfusion Medicine Choose patients who need to have their

blood type identified pre-operatively

Transfusion Medicine ABO system

Consists of three allelles - A, B and O antibodies are found in the serum of those lacking the

corresponding antigen. ABO blood group system

Blood group O = universal donor Blood group AB = universal recipient

Rhesus system Rhesus antibodies are immune antibodies requiring

exposure during transfusion or pregnancy 85% population are rhesus positive

Transfusion Medicine Cross Matching

Patients red cells grouped for ABO and Rhesus antigens

Serum tested to confirm patients ABO group Antibody screening to detect red cell antibodies in

patient’s serum Tests donor red cells against patients serum

Blood products Whole blood Packed red cells Platelet concentrates Human plasma - fresh frozen plasma Human albumin 25% Cryoprecipitate Clotting factors - Factor VIII / IX Immunoglobulins

Cryoprecipitate prepared from plasma contains factor 8, and fibrinogen.vWF Factor 13, and

ffibronectin. given as ABO compatible Indications for giving cryoprecipitate

Haemophilia - Used for emergency back up when factor concentrates are not available.

Von Willebrands Disease - As with other forms of haemophilia, factor concentrates are the therapy of choice.

low fibrinogen levels as can occur with massive transfusions Bleeding from excessive anticoagulation- FFP preferable Massive haemorrhage DIC

Fresh frozen plasma the fluid portion of one unit of human blood Contains components of the coagulation, fibrinolytic and

complement systems Indications for use

Reversal of warfarin effect deficient in the vit K dependent coagulation factors II, VII, IX,

and X, as well as proteins C and S. can be reversed by the administration of vitamin K but

immediate reversal with FFP for patients undergoing emergency surgery

Massive blood transfusion (>1 blood volume within several hours)

FFP is efficacious for treatment of deficiencies of factors II, V, VII, IX, X, and XI when specific component therapy isn’t available

Antithrombin 3 deficiency

Complications of blood transfusion Early Haemolytic reactions (immediate or delayed) Bacterial infections from contamination Allergic reactions to white cells or platelets Air embolism Hyperkalaemia Clotting abnormalities Late Infection - cytomegalovirus / hepatitis Immune sensitisation Iron overload

Disseminated intravascular coagulation Results in

activation of clotting cascade Bleeding due to consumption of clotting factors

May present with Bruising purpura Oozing (may be noticed during surgery)

Caused by Severe infection (meningococcal) metastatic adenocarcinoma shock Burns Transfusion reactions

DIC cont’d Investigation

Increased APTT and PT Reduced serum fibrinogen levels (<1 mg / ml) Thrombocytopenia

Management Treat underlying cause Supportive treatment with fluid and blood products

including platelets, cryo and FFP

Goals of antibiotic administration Reduce the incidence of surgical site

infection Minimise the effect of antibiotics on the

host’s normal flora Minimise damage to the Host’s immune

system Minimise adverse effects

Benefits of antibiotic prophylaxis Reduce morbidity and mortality Reduce length of hospital stay as a

result Avoidance of infection in surgical

wounds associated with faster return to normal activity

Risks of prophylaxis Anaphylactic reaction Antibiotic related diarrhoea Clostridium difficile infection more

common in Elderly GI surgery Use of broad spectrum antibiotics in

particular 3rd generation cephalosporins

Risks of prophylaxis cont’d Antibiotic resistance

Due to the amount of patients in a population receiving antibiotics and the length of time they are on them

Therefore prophylactic antibiotics should be a single dose unless otherwise indicated

Risks of prophylaxis cont’d Multiple resistance

NB patients undergoing elective surgery (eg hip replacement, valve replacement, CABG) should undergo screening for carriage of MRSA prior to hospital stay

Indications for antibiotic prophylaxis Intracranial surgery Upper GI surgery

Oesophageal, stomach and duodenal surgery

Hepatobiliary Lower GI

esp. colorectal and appendicectomy

Antibiotic prophylaxis Not indicated for Clean abdominal

operations Hernia repair OGD Mesh repairs

Antibiotics should however be considered in High risk patients

How do the specific type of antibiotics translate into the need for antibiotics?

Predisposal to infection Patient factors

Extremes of age Poor nutritional status Obesity Diabetes Co-existing infections Immunosuppressants

Predisposal to infection Operative factors

Length of operation Shaving/skin prep Sterility of instrument/theatre ventilation Drain insertion Haemostasis Type of operation and adequate

antimicrobial coverage

Classification of wounds Clean Clean contaminated Contaminated Dirty

Classification of wounds Clean

No inflammation encountered Viscera not entered No break in aseptic technique Eg hernia repair

Classification of wounds Clean contaminated

emergency surgery Viscus opened but no spillage of gut

content Minor break in aseptic technique right hemicolectomy and cholecystectomy Infection rate usually <10%

Classification of wounds Contaminated

Wounds left open Penetrating trauma less than 4 hours old Viscus opened with inflammation or spillage of

contents Major break in sterile technique appendicectomy and stab wound Infection rate 15-20%

Classification of wounds Dirty

Presence of pus Intraperitoneal abscess formation or

visceral perforation Penetrating trauma more than 4 hours old perforated abdominal viscera Infection rate 40%

Overview