On successfully completing this topic, you will be able to:
understand the management of severe hypertension in pregnancy
prevent and treat eclamptic fits
manage fluid balance in pre-eclampsia/eclampsia
investigate, recognise and treat the complications of the condition.
Introduction
Definitions: pre-eclampsia and eclampsia
Pre-eclampsia is pregnancy-induced hypertension in association with proteinuria or oedema or both. Virtually any organ system may be effected.
The Magpie trial defined severe pre-eclampsia as:
diastolic blood pressure greater than 110 mmHg on two occasions or systolic blood pressure greater than 170 mmHg on two occasions and proteinuria greater than 3+ or
diastolic blood pressure greater than 100 mmHg on two occasions and proteinuria greater than 2+ and at least two signs or symptoms of imminent eclampsia.
Eclampsia is defined as the occurrence of one or more convulsions during pregnancy or the first 10 days postpartum, together with at least two of the following features within 24 hours of the convulsions:
HELLP (haemolysis, elevated liver enzymes and low platelets) syndrome is an important variant of pre-eclampsia. Strictly, a diagnosis of HELLP syndrome needs confirmation of haemolysis, either by measuring lactate dehydrogenase (LDH) levels, as commonly carried out in the US, or by blood film to look for fragmented red cells. Alanine aminotransferase (ALT) levels above 75IU/l are seen as significant and levels above 150 IU/l are associated with increased morbidity to the mother. The platelet count should be below 100 × 109/litre to support the diagnosis.
Epidemiology
Eclampsia rates have fallen since the introduction of magnesium sulphate. The UK Obstetric Surveillance study in 2005 reported a rate of 2.7 cases per 10 000 births, compared with 4.9 cases per 10,000 births in the 1992 survey. There were no deaths in the 2005 study. Sixtythree percent of the women did not have established pre-eclampsia, and over 20% had their first fits at home.
The latest MBRRACE report has shown the lowest number of deaths from pre-eclampsia/eclampsia since the reports began with a rate of approx. 0.4 per 100,000 maternities. These are going to be reported on in detail in 2016 but messages from previous enquiries highlighted areas for improvement in care as follows:
control of systolic hypertension (aim for <150 mmHg)
management of the third stage as three women developed hypertension after administration of syntometrine.
Management of severe pre-eclampsia and eclampsia
The general principles are outlined below.
Senior and multidisciplinary involvement including:
obstetrician
midwife
anaesthetist
haematologist
intensivist
paediatrician.
All must be working to a standardised pattern of management (guidelines) that should only be deviated from rarely and then only by senior staff (consultants) and should undertake:
regular review of all parameters with an awareness of complications
prompt control of hypertension (especially systolic)
meticulous fluid balance to avoid iatrogenic fluid overload
seizure prophylaxis.
Note: Automated blood pressure recording systems can systematically underestimate blood pressure in pre-eclampsia, to a serious degree. Blood pressure values should be compared at the beginning of treatment, with those obtained by conventional sphygmomanometers and, if different, manual recording should be made subsequently.
Symptoms and signs
Pre-eclampsia is a multisystem disorder and its clinical presentation reflects this. Awareness of the complications (see Table 24.1) that can occur allows anticipation and prompt management.
| Maternal | Fetal |
|---|---|
| Severe hypertension | Prematurity |
| Risk of cerebrovascular accident | Intrauterine growth restriction |
| Oliguria, renal failure | Respiratory distress syndrome |
| Liver failure or rupture | Acute fetal distress (particularly with lowering of blood pressure) |
| DIC | |
| HELLP syndrome | Intrauterine death |
| Placental abruption | |
| Pulmonary oedema, ARDS | |
| Pulmonary oedema/haemorrhage | |
| Aspiration pneumonia | |
| Retinal detachment |
The following should raise concern:
headache, visual disturbances
vomiting, epigastric pain
nondependent (especially facial) or pulmonary oedema
right upper-quadrant or epigastric abdominal tenderness
recently developed hypertension greater than 160/110 mmHg with proteinuria greater than 1g in 24 hours
hyper-reflexia with clonus
rapidly changing biochemical/haematological picture.
Initial assessment of the woman
Antenatal history
A major aim of antenatal care is to detect women at risk of or with early signs of pre-eclampsia and increase the level of care. The Pre-eclampsia Community Guideline (PRECOG) emphasises the importance of investigating women with either new hypertension or new proteinuria.1
Acute management
The maternal and fetal condition should be assessed. As these are potentially sick women, it is appropriate that senior obstetric and anaesthetic staff should be involved in their assessment and management early.
The classification of severity is primarily based on the level of blood pressure and the presence of proteinuria. However, after making an initial diagnosis, other organ involvement becomes important in assessing maternal risk and this includes fetal assessment.
Atypical presentations of pre-eclampsia include women presenting initially with convulsions, abdominal pain or general malaise. In these cases, pre-eclampsia should always be considered and the blood pressure should be measured, the urine analysed and blood sent for analysis. A deterioration in clinical condition, particularly headache and abdominal pain, indicates worsening disease. Increasing oedema is not in itself a sign that should determine management. Maternal tendon reflexes are difficult to perform in a reproducible way, so are not of value to assess the risk of convulsion, although the presence of exaggerated clonus may be helpful.
NB: Tendon reflexes are of help when assessing magnesium toxicity: in this case they are reduced or absent.
Taking the blood pressure
Automated methods can systematically underestimate blood pressure, particularly the systolic blood pressure. It has been suggested that mercury sphygmomanometers should be used to establish baseline values. However these are no longer available in many units and a baseline check with another device, validated for use in pregnancy, is recommended, although such devices are limited.
While taking the blood pressure, the woman should be in a comfortable position, if possible, sitting at a 45° angle. The blood pressure cuff must be of the appropriate size. Too small a cuff over reads and too large will under read. Table 24.2 gives the correct-sized cuff to use, based on the circumference of the middle of the upper arm.
| Upper arm circumference | Sphygmomanometer cuff size |
|---|---|
| 18–23 cm | Small adult cuff |
| 23–33 cm | Standard adult cuff |
| 33–42 cm | Large adult cuff |
The cuff should be at the level of the heart. There are fluctuations in blood pressure in normal circumstances so multiple readings are needed to confirm the diagnosis. There is now a consensus that Korotkoff phase 5 is the preferable measurement of diastolic blood pressure.
As part of the initial assessment, blood pressure should be checked every 15 minutes until the woman is stabilised and then repeated half hourly. If intravenous antihypertensive drugs are administered, the blood pressure may need to be measured every 5 minutes in order to titrate treatment against the response.
Measuring proteinuria
Proteinuria is classically associated with the pathological lesion, glomeruloendotheliosis. Proteinuria per se is not a sign of renal damage and will usually recover after delivery. The widely used visual dipstick assessment as a screening test produces significant rates of false negative as well as false positive results. 2+ protein on dipstick testing is evidence of proteinuria but a more accurate test, such as 24-hour urine, should be undertaken to confirm this. In circumstances where immediate delivery is required, newer techniques such as protein/creatinine ratios can be performed quickly but have not yet been fully evaluated. A level of 30 mg/mmol urinary protein/creatinine appears to be equivalent to 0.3 g protein/24 hours.
Basic investigations
Blood should be sent for:
| Serum electrolytes: | Na, K, urea, creatinine, urate |
| Liver function tests: | albumin, ALT, aspartate aminotransferase (AST), bilirubin |
| Full blood count: | haemoglobin, white cell count, platelets |
| Clotting factors: | prothrombin time (PT), APTT + fibrinogen, fibrin/fibrinogen degradation products (FDPs) |
Group-and-save serum
Urine should be tested for protein and sent for culture.
All tests should be checked daily or more frequently if abnormal.
Coagulation
If the platelet count is above 100 × 109/litre and liver function tests are normal, the likelihood that the clotting results will be abnormal is very low and some units choose not to perform clotting tests without an abnormal platelet count. If the woman is clinically unwell, a coagulation screen should be sent to establish baseline values. There is no direct correlation between platelet count and liver damage and assessment of liver enzyme levels (usually by AST and ALT) is required. An AST level of above 75 IU/litre is seen as significant and a level above 150 IU/ litre is associated with increased maternal morbidity.
A diagnosis of HELLP syndrome must not be made on liver function tests alone – there needs to be confirmation of haemolysis, either increased LDH levels (commonly measured in the USA) or by visual examination of the blood film to look for fragmented red cells.
Renal function
Although, in pre-eclampsia, a rise in urate correlates with a poorer outcome for both mother and baby, the levels, in themselves, are not useful for clinical decision-making.
Renal function is generally maintained in pre-eclampsia until the late stage. Elevated creatinine at presentation should lead to suspicion of an underlying renal problem. In severe disease, rising serum creatinine is associated with a worsening outcome. Renal failure requiring support is now uncommon in pre-eclampsia in the developed, but and when it occurs it is usually associated with haemorrhage or sepsis.
Monitoring of clinical signs
The following should be monitored:
blood pressure (see above for details) and pulse rate
respiratory rate should be measured hourly particularly in women on magnesium
oxygen saturation should be measured continuously and charted hourly; if oxygen saturation falls, then medical review is essential to consider the possible differential diagnosis, with a high index of suspicion of early pulmonary oedema
fluid balance should be monitored very carefully and detailed input and output recordings should be charted
urine output should be measured carefully and hourly rates calculated; in more severe disease, and when delivery is planned or intravenous fluids are being given, this should be via an indwelling catheter
urine should be tested for proteinuria 4-hourly, if conservative management is planned, then a 24-hour assessment of urinary protein is helpful in assessing the disease
temperature should be measured 4-hourly, especially in those women with pre-eclampsia who are in labour, postpartum or immediately postoperative
optic fundi should be examined to assess for any signs of haemorrhage or papilloedema.
Assessment of the fetus
The fetus is at risk of growth restriction. Ultrasound assessment of fetal growth and liquor volume may be appropriate. Umbilical artery Doppler is a valuable noninvasive test of fetal wellbeing but is gestation dependent and needs careful interpretation in the very preterm pregnancy (below 30 weeks). Doppler of fetal vessels can be used but requires expert assessment and evaluation.
Cardiotocography (CTG) is the most widely used technique for the initial assessment of fetal wellbeing but it has little predictive value. If the woman is in labour, continuous electronic fetal monitoring is required.
Antepartum and intrapartum management
Control of blood pressure
The level of blood pressure that requires treatment is still unclear. The 2006–08 CMACE report suggests that treatment should be instituted if the systolic blood pressure is over 150 mmHg.2 The previous confidential maternal mortality report had suggested treating systolic pressures of 160 mmHg. Previously, the Magpie study definition of severe hypertension (systolic over 170 mmHg or diastolic 110 mmHg or mean arterial pressure [MAP] above 125 mmHg) was considered a clear threshold for treatment.3
The aim of therapy should be to stabilise the woman’s blood pressure. As a guide, this means:
maintaining systolic blood pressure at less than 150 mmHg
reducing diastolic blood pressure by 10 mmHg and bringing it below 105 mmHg in the first instance
maintaining the blood pressure at or below these levels.
Rapid drops in blood pressure should be avoided, particularly when the fetus is undelivered as this can potentially trigger acute fetal compromise.
Drug treatment
Labetalol
Labetalol is a combined alpha and beta blocker and is less likely to decrease uteroplacental blood flow than pure beta-blockers. It may improve cerebral perfusion, thereby reducing the risk of eclampsia.
Oral
If the woman can tolerate oral therapy, an initial 200 mg dose can be given. This can be given immediately, before venous access is established, to achieve as quick a result as an initial intravenous dose. There should be a reduction in blood pressure in about half an hour. A second oral dose can be given, if needed, after 1 hour. Over 50% of women requiring antihypertensive treatment can be controlled with oral therapy.
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