Preeclampsia: issues for anaesthetists
Alicia Dennis1, 2
1The University of Melbourne,Australia
2The Mercy Hospital forWomen, Heidelberg,Victoria,Australia
Preeclampsia is a disease of controversy, consensus opinion and coexisting theories of aetiology. It is also a disease of considerable morbidity and mortality complicating 5-8% of pregnancies and still remains in the top three causes of maternal morbidity and mortality globally. Deaths are due to intracranial haemorrhage and cerebral infarction, acute pulmonary oedema, respiratory failure and hepatic failure or rupture. It is the leading cause of fetal growth restriction, intrauterine fetal demise and planned preterm birth.1, 2 .
Understanding of the complexities of preeclampsia is hindered by confusion regarding terminology, by lack of a uniform definition, no diagnostic test and uncertainly related to the underlying aetiological factor or factors. These issues also lead to significant methodological problems when conducting research as achieving group homogeneity is difficult. Fundamental research into the causes of preeclampsia has however rapidly progressed over the last five years and important work is being done by many groups throughout the world particularly in Australia.
Hypertension in pregnancy can be caused by a variety of different pathologies. Important secondary causes of hypertension include renal disease, acute fatty liver and cholecystitis, haemolytic uraemic syndrome/thrombotic thrombocytopenia purpura, phaeochromocytoma, drug usage such as cocaine and amphetamines, and cardiovascular disease such as coarctation, subclavian stenosis, aortic dissection and vasculitis. By the very nature of the definition, preeclampsia is a postnatal diagnosis. From a practical treatment point of view however, interventions need to be made when the full diagnostic criteria have not been met. The most appropriate definition for use in Australia and New Zealand is from the Australasian Society for the Study of Hypertension in Pregnancy 2000.
Definition3
Hypertension arising: after 20 weeks gestation with resolution of the disease and hypertension by three months postpartum.
Systolic Blood Pressure (SBP) ≥ 140mmHg &/or
Diastolic Blood Pressure (DBP) (KorotkoffV) ≥ 90mmHg + one or more of
Proteinuria >0.3g/24 hours
Renal insufficiency
Liver disease
Neurological problems
Haematological disturbances
Fetal growth restriction
Severe preeclampsia presents with extreme derangements of organ function (SBP ≥160mmHg, DBP ≥ 110mmHg). These may include central nervous system problems of fitting (eclampsia), impaired conscious state and visual disturbances, renal dysfunction (≥5g protein/24 hours) and haematological complications including haemolysis and thrombocytopenia which, if they occur with abnormalities of hepatic function, is sometimes referred to as HELLP (haemolysis, elevated liver enzymes, low platelets) syndrome.
Pathophysiology4,5
It is now understood that there is widespread endothelial dysfunction affecting vascular beds throughout the body. The clinical manifestations of preeclampsia can vary depending on the degree of vascular involvement of each particular vascular bed.Many inflammatory and immunological mechanisms have been proposed.There is often abnormal trophoblastic invasion, with an absence of the normally occurring spiral vessel remodeling in the placenta.This leads to placental hypoxia and increased circulating soluble fms-like tyrosine kinase 1 (sFlt1). sFlt1 antagonizes the actions of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF).VEGF is responsible for decreasing vascular tone and reducing blood pressure.Thus antagonism of these proteins can induce many of the pathological changes in preeclampsia.
Key management points are:
1. Experienced multidisciplinary team -obstetrician, anaesthetist, physician, midwife, paediatrician
2.A plan for delivery of the fetus considering fetal lung maturation issues and health of the woman. Definitive treatment is removal of the placenta.
3. Commencement of magnesium sulphate for eclampsia prophylaxis in women with severe preeclampsia.The exact level of blood pressure and disease severity at which to commence magnesium sulphate remains controversial despite the MAGPIE trial. 6 Given that magnesium sulphate is a relatively safe drug and has been shown to be beneficial in reducing the incidence of eclampsia, magnesium sulphate should be commenced in women meeting the criteria of severe preeclampsia.
4.Treatment of hypertension.The latest Confidential Enquiries into Maternal and Child Health (CEMACH) 2007 recommends that a SBP ≥ 160mmHg be treated. Recommendations are also to treat a diastolic BP of ≥110mmHg.Treatment should be commenced at lower levels if there are other signs or symptoms of severe disease.The main medications used are hydralazine and labetalol. 1,7
5,Assessment of volume status, cardiac function and judicious use of intravenous fluids 8
6.Assessment of haematological derangements9
7.Aspiration prophylaxis
8. Regional anaesthesia, in the absence of contraindications, is safe. Lumbar epidural analgesia has benefits during labour and regional anaesthesia is the preferred method in the case of caesarean section10. Single shot spinal, combined spinal-epidural and epidural anaesthesia have been safely employed. Invasive monitoring such as an arterial line should be considered. Hypotension occurring during regional anaesthesia can be treated with titrated doses of intravenous ephedrine. Ergometrine should be avoided due to its propensity to cause a hypertensive crisis.
9. General anaesthesia should be avoided. If used particular attention and extreme vigilance should be given to ablating the potentially fatal hypertensive response to intubation.Many drugs have been used for this purpose including alfentanil, fentanyl, magnesium sulphate, intravenous lignocaine and esmolol.1
10. Postpartum surveillance – consideration of intensive care/monitoring for ongoing complications of preeclampsia and regional anaesthesia
11. Longer term follow up and confirmation of resolution.
1. Lewis G:The Confidential Enquiry into Maternal and Child Health(CEMACH). Saving Mothers’ Lives:reviewing maternal deaths to make motherhood safer -2003-2005,The Seventh report on Confidential Enquiries into Maternal Deaths in the United Kingdom. London, CEMACH, 2007
2. Khan KS,Wojdyla D, Say L, Gulmezoglu AM,Van Look PF:WHO analysis of causes of maternal death: a systematic review. Lancet 2006; 367: 1066-74
3. Brown MA, HagueWM, Higgins J, Lowe S,McCowan L,Oats J, Peek MJ, Rowan JA,Walters BN:The detection, investigation and management of hypertension in pregnancy: full consensus statement. Aust N Z J Obstet Gynaecol 2000; 40: 139-55
4.Maynard SE,Min J-Y,Merchan J, Lim K-H, Li J,Mondal S, Libermann TA,Morgan JP, Sellke FW, Stillman IE, Epstein FH, SukhatmeVP, Karumanchi SA: Excess placental soluble fms-like tyrosine kinase 1 (sFlt1) may contribute to endothelial dysfunction, hypertension, and proteinuria in preeclampsia.[see comment]. Journal of Clinical Investigation 2003; 111: 649•58
5.Makris A,Thornton C,Thompson J,Thomson S,Martin R,Ogle R, Waugh R,McKenzie P, Kirwan P, Hennessy A: Uteroplacental ischemia results in proteinuric hypertension and elevated sFLT-1.[see comment]. Kidney International 2007; 71: 977-84
6.Altman D, Carroli G, Duley L, Farrell B,Moodley J, Neilson J, Smith D: Do women with pre•eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial. Lancet 2002; 359: 1877-90
7. RCOG:The management of severe pre-eclampsia/eclampsia Guideline Number 10(A), Royal College of Obstetricians and Gynaecologists Guidelines, 2006, pp 1-11
8. GanzevoortW, Rep A, Bonsel GJ, FetterWP, van Sonderen L, DeVries JI,Wolf H:A randomised controlled trial comparing two temporising management strategies, one with and one without plasma volume expansion, for severe and early onset pre-eclampsia. Bjog 2005; 112: 1358-68
9. Katz L, de Amorim MM, Figueiroa JN, Pinto e Silva JL: Postpartum dexamethasone for women with hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome: a double-blind, placebo-controlled, randomized clinical trial.Am J Obstet Gynecol 2008; 198: 283 e1-8
10.Visalyaputra S, Rodanant O, SomboonviboonW,Tantivitayatan K, Thienthong S, Saengchote W: Spinal versus epidural anesthesia for cesarean delivery in severe preeclampsia: a prospective randomized, multicenter study.[see comment].Anesthesia & Analgesia 2005; 101: 862-8
