3.1 Pregnant woman with DKA Flashcards
summarise the case.
A 20-year-old woman with known Type I DM presenting with an infected
hand requiring surgical debridement complicated by the fact that she is
30 weeks pregnant and showing signs of diabetic ketoacidosis (raised blood
sugar, compensated metabolic acidosis, and abdominal pain).
can you explain the blood results?
Which are consistent with
pregnancy?
- Most striking abnormality is metabolic acidosis on blood gas with raised
blood glucose and ketones in urine consistent with diabetic ketoacidosis
(DKA) - Raised urea consistent with dehydration,
bordering on acute renal failure when taken in context with creatinine (GFR is usually much increased in pregnancy ∼ 50% at term;
therefore, although creatinine is in range,
it is much higher than would be expected for the
increase urea and creatinine clearance than
one would expect at this stage of pregnancy) - Raised white cell count with neutrophilia consistent with bacterial
infection (infected hand) - Mild anaemia consistent with physiological anaemia of pregnancy (plasma
volume increases by up to 45% with only a 20%–30% increase in red cell
mass, hence a ‘physiological’ anaemia)
Discuss the management of DKA.
General management
* Managed in HDU setting
* Joint care with obstetricians and medical team
DKA consists of the biochemical triad of ketonaemia, hyperglycaemia, and
acidaemia.
Therefore, management is directed at correcting these key issues.
- Full clinical history and examination
- Rapid ABC assessment including a full set of observations
and Glasgow coma score - Large-bore IV access (or central access if this is not possible)
- Consider precipitating causes and treat appropriately
- All patients with DKA need specialist
diabetic team input within 24 hours of admission
Initial investigations
- Blood:
blood glucose, urea and electrolytes, full blood count, blood
cultures, blood gas - ECG to look for arrhythmias due to associated electrolyte abnormalities
- Chest radiograph if clinically indicated
- Urinalysis and culture to rule out infection
Specific Treatment
Drugs
- Drugs
° Establish usual medication for diabetes
° Commence a fixed rate insulin infusion (FRII),
if weight not available from patient estimate weight in kg
(in pregnancy you should use patients current weight)
- Fluids
° Restore circulating volume with boluses of 500 mL–1000 mL 0.9%
sodium chloride if systolic blood pressure is < 90 mmHg (may need
more depending on response and may need to consider use of
vasopressors to maintain BP)
Suggested regiment
° once blood glucose is less than 14 mmol/L, then 10% dextrose
should be commenced at 125 mL/hr and ran with the normal saline
Suggested fluid regime
The suggested regime in a previously healthy 70 kg adult would be:
- 1L 0.9% sodium chloride over first hour
- 1L 0.9% sodium chloride with potassium chloride over next 2 hours
- 1L 0.9% sodium chloride with potassium chloride over next 2 hours
- 1L 0.9% sodium chloride with potassium chloride over next 4 hours
- 1L 0.9% sodium chloride with potassium chloride over next 4 hours
- 1L 0.9% sodium chloride with potassium chloride over next 6 hours
- Mandatory reassessment of cardiovascular status at 12 hours
- Electrolyte replacement
° If potassium is > 5.5 mmol/L,
no potassium replacement is given in fluid infusions
° If 3.5–5.5 mmol/L, 40 mmol per litre of saline should be given
° Below 3.5 mmol/L requires senior ITU input as more potassium will
need to be given with extra monitoring
- Goals
° Aim is to reduce blood ketones and suppress ketogenesis
° Achieve a fall of ketones of at least 0.5 mmol/L/hr
° Get resolution within 12–24 hours
- The precipitating cause needs to be treated (in this case, the infected
hand)
How do you make a sliding scale insulin or Variable Rate intravenous insulin infusion (VRiii)?
- The latest guidelines for the management of DKA
no longer recommend the use of a sliding scale insulin - A fixed rate insulin infusion is made by drawing up
50 units of human soluble insulin (e.g. actrapid)
and making it up to 50 mL with 0.9% sodium chloride.
- This is then run at 0.1 units/kg/hr until the ketone level is less than 0.6 mmol/L
Which fluids would you give her and why?
Why do patients become hypovolaemic
- There are several mechanisms responsible for fluid depletion in DKA
° osmotic diuresis due to hyperglycaemia
° Vomiting—commonly associated with DKA
° Inability to take in fluid due to a diminished level of
consciousness
- Electrolyte shifts and depletion are in part related to the osmotic
diuresis
- Electrolyte shifts and depletion are in part related to the osmotic
- Hyperkalaemia and hypokalaemia need particular attention
I would follow the fluid regime above and
tailor it to the specific needs of the patient.
I would use 0.9% sodium chloride with potassium chloride as
required as it is compliant with NPSA safety regulations, but I would be
aware of the risk of hyperchloraemic acidosis.
The surgeons are keen to debride her hand.
Describe how you would anaesthetise her.
At this stage I wouldn’t anaesthetise her; she needs her DKA treated and her
fluid status optimised prior to receiving an anaesthetic, be that regional or
general
You arrange a bed for her on the high-dependency unit, and 18 hours later her DKA has corrected but her hand still requires surgical debridement.
What is your anaesthetic choice?
Regional vs. general anaesthesia.
- My preferred method would be regional in view of recent metabolic
derangement and pregnancy.
Axillary brachial plexus block is the choice for forearm and hand surgery.
* If GA is planned, then this would need to be a rapid sequence induction.
There is a risk of difficult airway and a need for left lateral tilt.
* Ensure well-balanced anaesthetic avoiding hypoxia, hypercarbia, and
hypothermia.
* Fetus would require CTG monitoring.
Describe the technique for performing an axillary brachial plexus block.
General
* Full anaesthetic history and examination
* Informed consent of the patient
* Trained assistant
* Full monitoring as per AAGBI guidelines
* Ultrasound machine
* IV access
conduct of block
- Aseptic technique
- Ultrasound probe positioned with short axis
to arm just distal to pectoralis major insertion
- Ultrasound probe positioned with short axis
- Aim to achieve local anaesthetic spread around the axillary artery
covering median, ulnar, and radial nerve and a separate injection to cover
the musculocutaneous nerve
- Aim to achieve local anaesthetic spread around the axillary artery
- Total volume of local anaesthetic 20–25 mls of 0.25% L – Bupivacaine
(5–7 mL around each nerve)
- Total volume of local anaesthetic 20–25 mls of 0.25% L – Bupivacaine
Look at the ultrasound image
in Figure 3.1a and name the
structures.
Median, ulnar, and radial nerves are seen scattered around the axillary
artery with the tissue sheath. The musculocutaneous nerve is seen between
the biceps and coracobrachialis away from the rest of the brachial plexus.
The axillary vein is compressed leading to the possibility of accidental
intravascular injection of local anaesthetic
As you inject the local anaesthetic for your block, the woman begins to have a seizure.
What is your differential diagnosis?
- Non-pregnancy-related:
local anaesthetic toxicity,
hypoxia,
hypoglycaemia,
epilepsy,
metabolic derangement
(e.g. cerebral oedema from DKA)
- Pregnancy-related: Eclampsia
