Sickle cell in obstetrics
Take home messages
- Acute chest syndrome is potentially life threatening
- Discuss transfusions with haematology and crossmatch early
- Above all, avoid hypoxia, dehydration, hypothermia and acidosis
A quick recap
We've done a post on sickle cell disease here:
Anaestheasier ltd.
However this is not specific to obstetrics, hence we've written this one too.
What happens
Sickly haemoglobin is due to an autosomal recessive genetic mutation at position 6 on chromosome 11 where a negatively charged glutamic acid is replaced by not-at-all-charged valine within the β chain.
This change in charge alters the behaviour of the quaternary structure of haemoglobin, making it polymerise into inflexible clumps at low oxygen tensions.
This sets up the sickling spiral of doom:
- Sickling erythrocytes block up blood vessels
- Venous stasis worsens
- Hypoxia worsens
- More sickling
Hello painful crisis, stroke, acute chest syndrome - etc etc
If this happens on a recurrent basis, you get microangiopathic multi-organ damage, including but not limited to:
- Renal dysfunction
- Gall stones
- Splenic infarction
- Pulmonary hypertension
- Haemolytic anaemia (sickle cells only last 12 days, not the medical school 120)
Other factors at play
Interestingly, people with the same genotype have wildly different disease severity and symptomatology, meaning there has to be something else going on.
Possibilities include:
- Disordered vasoregulation
- Deranged nitric oxide signalling
- Unstable HbS molecules
- Differences in expression of cell-surface adhesion molecules
- Weirdly over-reactive vascular endothelium
No-one knows for sure, which means it probably isn't examinable either.
They need pre-assessment
Any expectant mother with a significant medical comorbidity should ideally be seen by a consultant anaesthetist in pre-assessment clinic, long before anything exciting kicks off.
'Should' is the key word here. Sometimes women will present for the first time with no prior knowledge of their condition.
Cardiovascular concerns
- Pulmonary hypertension - 10%
- Reduced blood viscosity, as anaemic and cardiac output higher
- Reduced pulmonary vascular resistance (if anaemic)
- Theoretical iron overload from repeated transfusions (rare)
Note that all the usual tactics to reduce pulmonary vascular resistance don't tend to work.
Pulmonary hypertension in pregnancy is bad news, and needs to be dealt with in a specialist centre that can manage heavy-duty cardiorespiratory support in a parturient.
Haematological concerns
- You want to know their baseline Hb
- A reticulocyte count is helpful
- If you can get hold of a %HbS (needs electrophoresis) then you're doing very well indeed
- Ideally you'd know their red cell antibody status for transfusions as well
- Document any history of hyperhaemolysis (should avoid transfusions wherever possible and needs MDT input)
- Can also consider EPO in pregnancy if substantial anaemia
Immunological issues
- Immunosuppression due to splenic infarction
- Continue their penicillin V (or other prophylaxis) antenatally
- If any suspicion of sepsis in labour, or requiring surgical intervention, then broad spectrum antibiotics are a must
The two bugs to remember for the exam are Strep pneumoniae and Haemophilus influenzae.
Pain control
Sickle cell crises are uniquely excruciating, and patients often require enormous doses of opioids to get any semblance of control.
It is likely that your sickle cell parturient will not be opioid naive, and may need much larger prescriptions than you would routinely supply on labour ward.
Things to ask the patient:
- Do they get regular crises?
- How bad are they?
- What symptoms do they get and which body parts are affected?
- How much opioid do they need?
Regional anaesthesia
Being told to 'avoid pain' with a labouring woman is less than helpful, so we'll say something more useful such as 'consider an early epidural' instead.
Obviously check for relevant contraindications first.
Avoid pethidine as there is an increased risk of seizures, but other opioids are fine to use as you would usually.
Bleeding and Transfusions
You need to think a little more carefully when timing any neuraxial procedures for analgesia in labour.
- Mothers with sickle cell disease are usually on aspirin from 12 weeks onwards to reduce the likelihood of pre-eclampsia.
- They are often also on low molecular weight heparin from 28 weeks, or sooner if there is significant risk or history of thrombosis.
When do I transfuse them?
- If Hb <50 g/litre
- If more than 20 g/litre drop from their usual Hb
- If significantly symptomatic
Should we routinely transfuse women prophylactically?
The logic:
- Reduces painful crises in the later stages of labour
The reality:
- No improvement on foetal outcome
- Substantial risk of transfusion reactions
- Risk of alloimmunisation
When to consider it:
- Multiple pregnancy
- Women on hydroxycarbamide
- Women with severe problems in previous pregnancies
As always - discuss with haematology, multi-disciplinary team meetings...yada yada
It will not suprise you to hear that this should only be initiated by the haematology experts.
Generally speaking if a woman was having exchange transfusions regularly, prior to becoming pregnant, then these would usually continue during pregnancy.
What are the risks of transfusion in sickle cell disease?
- Alloimmunisation (making non-ABO antibodies)
- Delayed haemolytic transfusion reaction (DHTR) - can mimic a pain crisis
- Iron overload (rare unless very regular transfusions)
- Infection
- Volume overload
- Hyperviscosity
- Transfusion-Related Acute Lung Injury - even more dangerous when they are at risk of acute chest crisis anyway
So what do I look out for?
Pain crisis
- Around half of women with sickle cell will experience an acute painful crisis during their pregnancy
- They often have a characteristic presentation, with a similar type and location of pain, however don't assume this - ask
- The key is lots of analgesia and quickly, along with fluids and oxygen
You'll probably be asked for help with cannulation
Acute Chest Syndrome
Defined by the presence of a new pulmonary infiltrates on chest X-ray plus one or more of:
- Chest pain - pleuritic usually
- Fever
- Shortness of breath
- Cough
- Hypoxia
Triggers
- Infection
- Fat Embolism
- Pulmonary Infarction
- Hypoxia
What actually happens
- Red cells sickle and occlude small pulmonary blood vessels
- Inflammation then makes this worse
- This all causes hypoxia
- Everything gets even worser
Treatment
- Oxygen
- Fluids
- Pain control
- Temperature management
- Transfusion
- Antibiotics
Stroke
- Any sudden change in neurology should trigger consideration of acute stroke
- This can be embolic or haemorrhagic
- CT head
- Discuss with neuro
- Consider exchange transfusion
You do not thrombolyse a sickle stroke.
What should I do for Caesarean sections?
Surprise surprise, we still prefer regional, largely because it avoids airway and respiratory issues and the extra bleeding of GA that can then trigger sickly badness.
Having the patient awake - on top of all the well established benefits for mum and baby - also means you can monitor for evidence of sickle-related issues, such as:
- acute chest syndrome
- painful sickle crisis
- acute stroke
How do I avoid problems?
- Keep them warm
- Position them carefully*
- Liberally apply oxygen - at least 94% sats
- Keep them hydrated with warmed fluids
- Use lots of antiemetics
- Keep their blood pressure within 10% of their normal range
- Give broad spectrum antibiotics prior to skin incision
- Exchange transfusion can also be considered in certain cases
- Lots of pain relief
- Regional if possible, and safe within the confines of whatever anticoagulation the woman has had
*They may have avascular necrosis of the hip which can make positioning difficult.
If you have to GA
I know that you know that we all know you're supposed to maintain oxygenation throughout induction of anaesthesia because hypoxia is bad.
It's just even extra more bad in sickle cell patients.
- Try and identify tricky airways first, and make a bunch of back up plans
- High flow nasal oxygen for preoxygenation
- Ramped position
- Rapid sequence induction
Basically do what you always do, but really well.
Who is most at risk of complications?
Women with:
- Frequent painful crises
- Previous acute chest syndrome
- Previous stroke
Not exactly surprising.
Can I give uterotonics?
Yes. They're anaemic and at risk of bleeding.
- IV bolus oxytocin followed by
- 10 unit per hour infusion (or whatever your institution's policy is)
The same cautions as usual apply to the other two:
- Ergometrine - avoid in heart disease, pre-eclampsia and pulmonary hypertension
- Prostaglandins - avoid in severe brittle asthmatics
Nothing new here.
Major haemorrhage
Ideally you've already spoken to haematology, and ideally you have four units crossmatched and ready to go.
Ideally.
When it comes down to it, the decision is often 'what's the least bad option?' and the answer to this may well be giving the major haemorrhage protocol blood, and then dealing with any reactions afterwards.
You may need to consider prophylactic:
- IVIG
- Methylprednisolone
To avoid a delayed haemolytic transfusion reaction.
Can I use Cell Salvage?
Erm... sort of.
Sickle cell is not an absolute contraindication to cell salvage, but there isn't sufficient data to confirm that it's safe to do so.
The major concern is that dragging unhappy red cells out of the body, traumatising them in a centrifuge, cooling them down and making them hypoxic and acidotic is a surefire way to inject a whole load of sickles back into the patient.
If you are going to use cell salvage:
- Discuss with haematology first
- Explore other options first
- Keep the patient and the blood (where possible) normothermic, normoxic and normo-pH-ic
And after?
You can relax when the patient goes home, or you get home, and not a moment before.
Women with sickle cell should stay on labour ward for at least 24 to 48 hours for close observation, and if they've had any major surgical intervention then you're ideally looking at HDU if possible.
If there's an epidural catheter in at the end of the section, maybe leave it there for good luck.
Post op analgesia
- Regional - epidural, TAP blocks
- Regular paracetamol
- Systemic opioids - and you might need a lot if they're not opioid naive*
Probably best to avoid NSAIDs if there is any concern about renal function.
*A PCA is probably going to be everyone's best friend here.
Here's our post on sickle cell
Anaestheasier ltd.References and Further Reading
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