8.1 Valve Replacement for Urgent Surgery

Question 1

You are asked to see a 63-year-old woman requiring hemiarthroplasty.
She was found on the floor by her husband earlier that day and had sustained a
fracture of neck of femur.

Past Medical History Rheumatic heart disease diagnosed when she was about 30 years of age,
and 2 years ago she had aortic and mitral valve replacements.

She also had two strokes many years ago with no residual neurological
deficit. Before the fracture, she was walking with a Zimmer frame but would
get breathless after 100 yards when she would have to stop and ‘take a
breath

Social History

She gave up smoking 10 years ago after having smoked most of her life.
She drinks socially and does not indulge in illicit drugs.

Drugs
Spironolactone 25 mg oD Bumetanide 1 mg oD
Lisinopril 5 mg oD Digoxin 125 mcg oD
Warfarin (variable dose over the week) Paracetamol and Tramadol prn

on examination Awake and alert
Respiratory rate: 30/min
Saturation: 94% on high flow oxygen
Heart rate: 85/min
Blood pressure: 110/70 mmHg
BMI: 38.8
Raised JVP
Reduced air entry bilaterally with bibasal crepitations

investigations Hb 10.1 g/dL (13–16) Na 128 mmol/L (137–145)
WCC 3.0 × 109/L (4–11) K 4.8 mmol/L (3.6–5.0)
Platelets 242 × 109/L (140–400) Urea 12 mmol/L (1.7–8.3)
PCV 0.35 (0.38–0.56) Creat 150 umol/L (62–124)
MCV 88 femto Litres (80–100)
MCH 30 pico grams (26–34) INR 3.6 (0.8–1.2)

summarise the case.

What are the pertinent
features?

Answer 1

This is a relatively young obese patient who sustained a fracture of her neck
of femur, the circumstances of which are unknown but could be linked to an
acute event as this woman has multiple comorbidities.

Her medical history is mainly centred on her aortic and mitral valve
replacements, which occurred 2 years ago and she is now presenting with
clinical signs of cardiac failure and renal impairment for which she is treated.
She is on two types of diuretics, digoxin, ACE inhibitors, and warfarin. She
also suffered from two CVAs in the past.

• Two metallic valves
• Cardiac failure
• Renal impairment
• Obesity
• Correction of high INR
• Bridging therapy during surgery
• High-risk case

Question 2

some statistics regards to hip #

Answer 2

70 000 to 75 000 hip fractures per year in the UK
Mortality: 10% at one month, 20% at three months, 30% at one year.

This is linked to the fact that neck of femur (NoF) fractures occur very often
following a fall due to an ‘event’ (i.e. atrial fibrillation (AF), cerebrovascular
accident (CVA), sick sinus syndrome).

Question 3

What are the consequences of obesity?

Answer 3

1. Anatomically
   * Difficult IV access
   * Difficult airway
   * Increased risk of aspiration
   * Difficult procedures such as spinal, epidural, and any regional technique
2. Physiologically
3. Associated diseases: Diabetes and ischaemic heart disease.
4. Increased risk of DVT, CVA, fatty liver disease

Increased blood loss

Question 4

What are the consequences of obesity?

Physiological

Answer 4

• Increased oxygen demand and CO2 production
• Reduced FRC, chronic hypoxaemia, and hypoxic pulmonary
  vasoconstriction with increased pulmonary pressures leading to
  right-sided cardiac failure. In her case this is compounded by left-sided
  cardiac failure linked to her valve replacements.
• Obstructive sleep apnoea
• Hypertension (her BP is normal but she is on antihypertensives. In
  addition, her cardiac failure would not generate high blood pressures)
  Associated diseases: Diabetes and ischaemic heart disease.
  Increased risk of DVT, CVA, fatty liver disease
  Increased blood los

Question 5

talk through the blood results.

Answer 5

Her preliminary investigations show that she is anaemic (normocytic and
normochromic), has low sodium, raised urea, and an elevated creatinine.
The most striking is her INR which is 3.6.

Question 6

Looking at the results, what are the potential causes, in
this particular case, for a low sodium, raised urea, and low haemoglobin?

Answer 6

• Hyponatraemia due to cardiac failure with subsequent fluid retention and
  diuretics.
• Raised urea due partly to dehydration but is also indicative in this case of
  impaired renal function (creatinine 150).
• The reason for her low haemoglobin is multi-factorial including blood loss
  from the fracture site but also chronic loss due to red cell damage by the
  valves and chronic insensitive loss as she is on warfarin.

Question 7

What do the cXR and
ecG show?

Answer 7

cXR
Cardiomegaly
Sternotomy wires
Two metallic valves—mitral and aortic valves
Bilateral increased lung markings
Alveolar oedema
Kerley B lines

___________________________

ECG
Sinus rhythm rate 85/min
Wide QRS complexes keeping with LBBB
Left axis deviation
QRS fragmentation in V4–5

Question 8

How to recognise left axis deviation

Answer 8

Three Lead analysis

QRS is POSITIVE (dominant R wave) in Lead I

QRS is NEGATIVE (dominant S wave) in leads II, III and aVF

Causes
Left anterior fascicular block
Left bundle branch block
Left ventricular hypertrophy

Question 9

How would you identify these prosthetic valves as mitral and aortic?

Answer 9

Localising cardiac prosthetic valves can be difficult. The best strategy that
can be employed to aid in characterising the type of prosthetic valve involves
assessing the location of the valve and then determining the orientation and
direction of flow (most accurate).

Location
on the frontal chest radiograph (either the AP or PA view), draw a
longitudinal line through the mid sternal body and intersect it by a sagittal
line.

The aortic valve should overlie the intersection of these two lines, and
the mitral valve will lie in the lower left quadrant (the patient’s left).

Direction of flow
If the direction of flow is from inferior to superior (towards the aorta), then an
aortic valve is likely. If the direction of flow is from superior to inferior (towards
the apex) in the left chest, then the valve is likely a mitral valve.

Question 10

What further investigations would you request prior to going to theatre?

Answer 10

• Group and save, cross match blood and blood products
• Liver function tests as high BMI and potential right-sided cardiac failure
• Echocardiogram prior to cardiology opinion

Question 11

What will an ECHO show?

Answer 11

An echocardiogram will provide:

1. Qualitative assessment:
   Establish the integrity of the valves and the gradients as well as any
   regurgitation.
   The quality of the ventricular function, establishing any diastolic (ventricular
   compliance) and systolic dysfunction (ejection fraction).
2. Quantitative assessment:
   Atrial and ventricular measurements
   Filling pressures
   Ejection fraction
   Valve dimensions

Question 12

Discuss the specific benefits of the various drugs the patient takes.

Answer 12

• Lisinopril—
  inhibits angiotensin-converting enzyme
  =
  decreases the formation of Angiotensin II
  ->
  decreased sympathetic activity,
  =
  reverses myocardial and vascular remodeling
• Spironolactone—
  mineralocorticoid receptor blockade -> natriuresis,

diuresis,
K retention, and
also decreases the myocardial collagen
formation and endothelial dysfunction

• Bumetanide—loop diuretic for symptom control
• Digoxin—rate control if patient is in atrial fibrillation
• Warfarin—for thromboprophylaxis

Question 13

What should the patient’s normal INR be?

Answer 13

The presence of mechanical mitral valve calls for a maintenance of INR
2.5–3.5; but the history of CVAs while on warfarin warrants an INR of 3–4.

target inR
* 2–3 for
DVT prophylaxis, treatment of pulmonary embolus (PE), transient
ischaemic attack (TIA), and AF with high risk of embolisation.

• 2.5–3.5 for mechanical mitral valve or aortic valve
  with additional risk factors.
• 3.0–4.0 for mechanical valve and
  systemic embolism despite therapeutic
  INR of 2.5–3.5.

Question 14

What INR is considered safe for a hemiarthroplasty?
How would you correct this patient’s high inR?

Answer 14

An INR of 1.5 is considered safe for surgery in these patients.

Correction is required for surgery,
but this has to be achieved for as short a period of time
as possible due to the high risk of thromboembolism.

Base your answer on the way warfarin works
(i.e. how it competes with vitamin K in the synthesis of
factors II, VII, IX, and X and is highly protein bound).

1. Vitamin K
2. PCC
3. FFP

Question 15

Vitamin K

Answer 15

5–10 mg IV, takes 4 to 8 hours to work and will interfere
with anticoagulation for a long time.

Question 16

Prothrombin complex concentrate

Answer 16

Prothrombin complex concentrate (Beriplex)

is now preferred over FFP.

Beriplex is made from blood and is a
combination of factors II, VII, IX, and X with proteins C and S.

It comes as a powder with a solvent to make a
100 ml solution containing 250 IU.

The dose is calculated based on the patient’s weight and current INR.

The INR is normalised within 30 min, and the effect lasts 6 to 8 hours.

Thus, if vitamin K has been administered
at the same time, it should take effect when Beriplex stops working.

Repeated monitoring of INR is compulsory.

Question 17

Fresh frozen plasma

Answer 17

Fresh frozen plasma is no longer recommended. Also a large volume
is needed (15 ml/kg), and this is detrimental in this patient with cardiac
failure.

Question 18

How would you prevent thromboembolic risks while you normalise the inR?

Answer 18

Perioperative management of patients on warfarin or antiplatelet therapy
involves balancing individual risks for thromboembolism and bleeding.

Discontinuing anticoagulant therapy is necessary for major surgery, and
to prevent thromboembolic events during this period, bridging therapy is advised.

Before surgery
* Discontinue warfarin 5 to 6 days before surgery.
* Start therapeutic low molecular weight heparin (LMWH) 36 hours after last dose of warfarin.
* Stop LMWH 24 hours prior to surgery.

After surgery
* Start therapeutic LMWH 24 hours after surgery.
* Restart anticoagulant after discussion with the surgeon and bleeding risks assessed
* Check INR daily.
* Discontinue LMWH once target INR is reached.

Question 19

What is cardiac failure?

Answer 19

Cardiac failure is a complex clinical syndrome

that results from any structural or functional impairment of
ventricular filling or ejection of blood,

secondary to hypertension, valvular heart disease, and ischaemic heart disease.

It is a major clinical predictor of perioperative risk

Question 20

Describe the pathophysiology of heart failure.

Answer 20

• Long-standing pressure or volume overload
  leads to cardiac myocyte remodeling and
  chamber enlargement and stiffness that impair filling.
• Decreased cardiac output leads to
  sympathetic activation of the
  renin-angiotensin-aldosterone system (RAAS)

resulting in salt and water retention and
an increase in circulating volume.

Initially this restores the cardiac output in accordance

with the Frank Starling’s law,

but later it results in a

myocardium vulnerable to ischaemia

and a circulation that is dependent on sympathetic tone.

Question 21

can you quantify heart failure?

Answer 21

According to ejection Fraction (EF)

Normal: EF of 60%–70%
Mild: EF of 40%–50%
Moderate: EF of 30%–40%
Severe: EF < 30%

NYHA classification

I: ordinary physical activity does not cause symptoms.
II: ordinary physical activity causes fatigue, dyspnoea, and angina.
III: Comfortable at rest.
IV: Symptomatic at rest.

Question 22

How would you treat this patient’s
symptomatic cardiac failure?

Answer 22

This patient is already on cardiac failure treatment

(i.e. diuretics, digoxin, ACE inhibitors);

thus, any further improvement would require the involvement of a cardiologist

who might consider adding
vasodilators,
β blockers,
angiotensin II receptor antagonists.

Question 23

How would you anaesthetise her?

Discussion

Technique

Answer 23

This is a challenging patient who needs consultant input from a range of
specialties—anaesthetic, surgical, cardiology, haematology, as well as
postoperative ITU care. Consideration should be given to the resources
available locally, and transfer to a tertiary centre might have to be considered
in view of her complex cardiac history.

The patient and her family should be made aware of the high risk of severe
postoperative complications including death.

The pertinent points as set above means that in order to decide between a
regional technique or a general anaesthesia +/– nerve block, the following
have to be taken into account:

• There is no clear evidence to suggest one technique over the other.
  Weigh the benefits and risks and choose your anaesthetic method.
• Although an INR of 1.5 does not preclude a spinal, a regional technique
  would not only be difficult (obese and positioning problem) but could lead
  to a potential catastrophic cardiovascular instability due to associated
  vasodilatation.
• A general anaesthetic would allow for more control of blood pressure and
  cardiac output.

Question 24

Preoperative

Answer 24

• Assessment—
  history and examination to look for decompensation
• Optimisation of medical therapy—
  to decrease symptoms and prevent
  disease progression
• Investigations—
  to assess cardiac function

Question 25

Intraoperative

Answer 25

Intraoperative

• Anaesthetic—
  GA or RA with application of general principles (see below).
• Invasive monitoring—
  arterial line, CVP, oesophageal Doppler, or other
  method of cardiac output monitoring is useful.
• Analgesia—
  regional block like fascia iliaca block with catheter can
  be considered for postoperative analgesia. Avoid NSAIDS due to
  susceptibility to renal failure and fluid retention.
• Fluid balance—
  strict fluid balance guided by invasive monitoring is
  important.
• Temperature control—
  maintains cardiac stability.
• Antibiotics—for endocarditis and surgical prophylaxis.

Question 26

Antibiotics and valves

Answer 26

According to NICE guidelines, antibiotics should not be given routinely to
patients with heart valve replacement but discussed on a case-by-case
basis. This is a change from the past recommendations based on the
increase in antibiotic resistance.
From the surgery point of view, the NICE guidelines have to be adhered to
and antibiotics given at least 30 min prior to the start of the operation.
Cefuroxime 1.5 g is commonly used and Teicoplanin 400 mg can also be
given, as this patient group has a high MRSA contamination level.

Question 27

Postoperative

Answer 27

ITU care is advisable due to chance of increased risk of:

• Cardiac failure
• Myocardial infarction
• Renal failure
• Endocarditis
• Valve failure
• TIA/CVA
• Death

Question 28

General principles

Answer 28

Avoid
* Tachycardia and arrhythmias
* Hypotension/hypertension
* Hypovolemia
* Hypoxia and hypercarbia
* Anaemia
* Pain

Maintain
* Preload
* Contractility
* Afterload
* Fluid balance
* Tissue perfusion and cardiac output

Question 29

Patient has advanced directive with DnAR status. Does this affect your management?

Answer 29

This does not affect the initial management as do not resuscitate doesn’t mean do not treat, but it will help putting in place treatment ceilings if the
patient deteriorates and is not responding to the therapy implemented.

Question 30

What do you know about bone cement implantation (BCIS) syndrome?

Answer 30

BCIS is an important cause of intraoperative morbidity and mortality.

It happens as a result of right ventricular failure due to increase in pulmonary
vascular resistance and increased pulmonary artery pressure.

Question 31

What is the composition of bone cement?

Answer 31

The important constituents of bone cement are:

Polymer—polymethyl methacrylate (PMMA) as a white powder

Liquid monomer—methyl methacrylate (MMA)

Activator—N, N-dimethyl-p-toluidine

Antibiotics—optional

once mixed together, the powder particles become entrapped and glued
within the net of the polymerised monomer.

Question 32

What do you know about the pathophysiology?

Answer 32

Emboli theory
Reaming of the femur increases intramedullary pressure and releases
debris such as marrow, bone, fat, and along with the cement particles, they
embolise to the right heart and cause increased pulmonary artery pressure.

Mediators theory
Systemic embolisation of the bone cement causes release of
proinflammatory mediators such as histamine, complement factors, thrombin
and tissue thromboplastin, which further increases the pulmonary vascular
resistance and bronchoconstriction and V/Q mismatch.

Question 33

How can you grade the BCIS according to severity?

Answer 33

I: Moderate hypoxia (Spo2 > 94%) or a
decrease in systolic arterial pressure > 20%.

II: Severe hypoxia (Spo2 44%) or unexpected loss of consciousness.

III: Cardiovascular collapse requiring cardiopulmonary resuscitation.

Question 34

What are the risk factors for the development of BCIS?

Answer 34

Patient factors
ASA III/IV
Preexisting pulmonary hypertension
Significant cardiorespiratory disease
Osteoporosis

Surgical factors
Pathological fracture
Intertrochanteric fracture
Long-stem arthroplast

Question 35

How would you prevent and treat BCIS?

Answer 35

Prevention

1. General
   Identify high-risk patients
   Avoid cemented arthroplasty in these patients
2. Anaesthetic management
   optimise the cardiovascular reserve
   Maintain normovolaemia and high inspired oxygen
   Avoid haemodynamic compromise
3. Surgical management
   Thorough lavage of the medullary canal
   Good haemostasis
   Specific cement mixing method
4. Treatment
   High flow oxygen
   IV fluids
   Pulmonary vasodilators
   Inotropes (Dobutamine, Milrinone)
   Invasive monitoring

BCIS is reversible, and the pulmonary artery pressures normalise within
24 hours. This means effective resuscitation is essential to decreasing the
morbidity and mortality of this potentially life-threatening condition.