General Surgery/trauma (Ht)

Front 1

MASTER trial

Back 1

- Lancet 2003
- 1000 high risk patients undergoing major abdominal surgery randomised to thoracic epidural vs IV opioid
- primary endpoint was death at 30/7 or major post-op morbidity
- no difference in mortality
- subgroup analysis showed less respiratory failure in epidural group (NNT 15)
- intention to treat analysis, included those epidurals which fell out/removed etc (also compared as treated analysis which showed no difference)

Front 2

obesity

Back 2

BMI >30
BMI >55 = supermorbid obesity

Front 3

co-morbidities with obesity

Back 3

CVS
- HTN
- high chol
- IHD

Resp:
- OSA
- obesity hypoventilation syndrome
- decreased FRC
- prone to rapid desaturation from reduced FRC and also increased O2 requirement
- decreased chest wall compliance

Endo
- DM

Gasto
- fatty liver

Front 4

Physiological effects of pneumoperitoneum

Back 4

CVS
- reduced venous return (initial increase from splachnic autotransfusion) due to compression of IVC, leads to reduced CO
- SVR increased from direct pressure effect on aorta, release of catecholamine and also from activation of RAAS
- increase in myocardial work, prone to myocardial ischaemia
- CO initial increase from increased VR, then decreased
- risk of bradycardia from vagal stimulation with insufflation
- elevated CO2 causes tachycardia
- risk of VAE on insufflation

Resp:
- FRC reduced (further if trendelenburg)
- increased airway resistance
- reduced compliance
- absorption of CO2 causes hypercarbia and R shift of Hb-O2 dissociation curve
- risk of PTx, scut emphysema

Renal
- decreased renal perfusion, compounded by reduced CO

Neuro
- increased ICP from elevated intrathoracic pressure and hypercarbia

GIT:
- increased risk of aspiration

Acid-Base
- acidosis, hyperkalaemia from inactivated Na-K ATPase

Front 5

Virchow's triad

Back 5

- describes pathology which predisposes to VTE
- hypercoagulable state eg malignancy, SIRs postop, thrombophilia, smoking, drugs eg OCP
- endothelial damage eg surgery, trauma, burns, indwelling devices
- venous stasis eg surgery with paralysis, prolonged travel, indwelling devices, low CO, obesity

Front 6

General measures to reduce VTE

Back 6

- modify social factors eg smoking, weight loss
- avoid dehydration
- early mobility
- high quality surgery (reduces duration)

Front 7

Mechanical measures to reduce VTE

Back 7

1/ calf compressor
- periodic compression of calf and thigh to mimic affect of muscle pump

2/ TEDs (thromboembolic deterrent stocking)
- exert graded circumferential pressure from distal to proximal
- need to be fitted correctly
- thigh length may be more beneficial then knee length
- additional benefit when given with heparin

Front 8

Pharmacological measures to reduce VTE

Back 8

- most common: heparin and LMWH
- other: aspirin, warfarin, Xa inhibitors and direct thrombin inhibitors
- balanced against risk of bleeding eg current bleeding, coagulation disorder (platelet dysfunction, coagulopathy, other medication which also increases bleeding risk) or high risk of bleeding (CNS surgery, high falls risk)

Front 9

Unfractioned heparin

Back 9

- derived from naturally occuring anticoagulant
- MOA via potentiation of AT3, which inhibits factor X and 2, inhibits platelets at high doses
- measure via use of APTT
- can reverse with protamine
- metabolised via liver, safe in renal failure
- need bd dosing
- risk of HITs
- less predictable effect cf LMWH

Front 10

LMWH

Back 10

- short chains derived from heparin
- similar effect to UFH, more anti-X effect and less intrinsic pathway effect, APTT less reliable
- once a day dosing
- less risk of HITs
- more reliable PK, so dont need monitoring (can use anti-Xa if needed)
- renally cleared so can accumulate in renal failure

Front 11

warfarin

Back 11

- inhibits reduction of vitamin K back to active form so inhibits vit K dependent factors 2, 7, 9 and 10
- also inhibits protein C and S (inhibited 1st so pro-coagulant effect, protein C breaks down 5 and 8, protein S stimulated C)
- unstable PK

Front 12

aspirin

Back 12

- irreversible inhibition of COX, leading to reduced thromboxane prodn and unopposed prostaglandin
- leads to reduced platelet aggregation and vasoconstriction
- only small decrease in VTE risk

Front 13

fondaparinux

Back 13

- synthetic drug, with almost identical structure as heparin for AT3
- potentiates AT3 effect, similar to heparin
- PO dosing once per day
- can use in HITs patients
- similar risk prevention as LMWH but higher bleeding risk

Front 14

other VTE prophylaxis

Back 14

- regional anaesthesia
works via blockade of sympathomimetics leading to vasodilation

- caval filters
place into IVC and prevent emboli from reaching R heart

Front 15

cell salvage

Back 15

- process of collecting blood from surgical field via special sucker
- blood added to heparinised saline and or citrate anti-coagulant then filtered and washed to remove contaminants
- red cells retained, plasma, platelets, heparin, free Hb and inflammatory mediators discarded

Front 16

benefits of cell salvage

Back 16

- reduced need for allogenic blood transfusion, therefore avoid risks eg ABO/Rh/other red cell antibody incompatibility, low risk transmission of blood borne disease eg Hep C, decreased risk of TRALI, immune modulation
- useful if rare blood type or antibodies
- acceptable for some JW
- blood has normal O2 carrying capacity (if reinfused rapidly)
- blood may be stored for 6/24 before reinfusion

Front 17

limitations of cell salvage

Back 17

- expensive to setup and acquire equipment and train staff
- require specialised equipment and staff
- risk of air and fat embolism
- risk of electrolyte imbalance eg hypocalcaemia
- risk of AFE and transmission of cancer cells if used in obstetrics or cancer surgery
- dilutional coagulopathy (only contains RBC, no platelets or factors)
- risk of bacterial contamination
- require finite amount of suctioned blood before can be washed if used fixed volume system

Front 18

indications for use

Back 18

- anticipated blood loss >20% of blood volume
- pre-op anaemia or risk factors for bleeding
- patients with rare blood groups
- patient refusal to receive allogeneic blood

Front 19

thermoneutral zone

Back 19

- range of core temperatures over which there is no autonomic response occurs
- range of 0.2 degrees around 37

Front 20

physiological changes if temperature below thermoneutral zone

Back 20

- behavioural eg jumper on, move out of wind
- shivering
- peripheral vasoconstriction
- piloerection
- non-shivering thermogenesis (in neonates)

Front 21

thermoneutral zone

Back 21

range of ambient temperature over which there is no metabolic response

Front 22

systematic changes with hypothermia

Back 22

CVS
- catecholamine release, leading to increased CO and myocardial O2 demand
- systemic and pulmonary vasoconstriction
- increased risk of ischaemia
- increase in arrhytmias eg VT particularly below 30
- ECG changes (increased PR, widened QRS, J wave)

Resp:
- Hb-O2 curve L shifted
- increased solubility of gases in blood (pH vs alpha stat)
- reduced ventilatory response to PaCO2

Neurological
- reduced CMRO2
- reduced CBF and therefore ICP

Immune
- impaired wound healing
- increased risk of wound infection

Haematological
- impaired clotting factors, platelets

Musculoskeletal
- increased shivering to increase heat production

Renal
- diuresis from reduced absorption from LoH

GIT
- reduced gastric motility

Pharmacological
- decreased MAC
- reduced metabolism of some drugs eg NDMR

Front 23

indications for hypothermia

Back 23

- hypoxic neonatal encephalopathy
- OOF VF/VT arrest
- cerebral protection for aortic arch surgery

Front 24

heat loss

Back 24

- radiation (60%)
- convection (25%)
- evaporation (10%)
- conduction 5%)

- evaporation

Front 25

methods to prevent heat loss

Back 25

pre-op
- pre-warming - acts to reduce core to periphery heat gradient
- heat theatre
- pharmacological agents eg nifedipine (not used clinically)

intra-op
- cutaneous warming with active warming with FAWB or passive by covering with sheet (FAWB much more effective)
- HME filter and low gas flows
- fluid warming (IV fluids, blood and products, surgical wash)

Front 26

ERAS

Back 26

- uses a variety of strategies to reduce complications after surgery and improve patient recovery
- multidisciplinary approach to planning, perioperative management of surgery, anaesthesia and recovery
- detailed preoperative patient education, information and risk assessment
- avoidance of pre-op dehydration, specialised carbohydrate drinks up to 2/24 pre-op
- no sedative pre-medication
- pre-warming
- early administration of antibiotics
- minimally invasive surgical approaches eg laparoscopic
- goal directed fluid therapy through use of non-invasive cardiac output monitors eg vigeleo, oesophageal doppler
- multimodal analgesia strategy including regional techniques (thoracic epidurals) to reduce postop opioid consumption
- avoidance of NG and surgical drains
- early removal of IDC
- early enteral feeding
- early mobilisation and input from physiotherapy
- early input from acute pain team
- aggressive treatment for prophylaxis for PONV

Front 27

When to activate MTP

Back 27

- transfused ≥4 units or anticipate need to transfuse ≥4 within 4/24 and haemodynamically unstable
- severe thoracic, abdominal or long bone trauma
- major obstetric, gastrointestinal or surgical bleeding
- aim for temp >35, Plt >50, fibrinogen >1, ionised Ca >1.1, pH >7.2, INR ≤1.5