O&g: Hypertensive Disorders Of Pregnancy

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Definition of Hypertension in pregnancy

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Definition of hypertension : can be defined in several ways using different parameters 1. Hypertension is said to occur if the systolic pressure is more than 140 mmHg or the diastolic is more than 90mmHg measured on two separate occasions of at least 4-6hrs apart.2. Single measurement of 160mmHg systolic or 110mmHg diastolic 3. An increase of at least 15mmHg diastolic or 30mmHg systolic over the booking blood pressure in the first half of pregnancy 4. Increase in the mean Arterial blood pressure of 20mmHg 5. Mean arterial blood pressure of up to 105 mmHg if the previous Bp is unknown. M.A.P. = Pulse pressure/3 + Diastolic Hypertension in Pregnancy is a major cause of maternal mortality in Africa and complicates about 7% of pregnancies.

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Classification of hypertensive disorders of pregnancy

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1. Chronic hypertension.

2. Pre- eclampsia

3. Chronic hypertension with superimposed pre-eclampsia

4. Eclampsia

5. Gestational hypertension (transient HBP)

6. Unclassified hypertension

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Chronic hypertension

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Chronic hypertension is one that occurs in pregnancy with or without proteinuria in the early part of pregnancy (b/4 20wks) it could be due to essential hypertension, renal disease or other causes of hypertension.

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Pre-eclampsia

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Pre-eclampsia is the occurrence of hypertension accompanied by significant proteinuria with or without oedema after 20wks of gestation in a known normotensive, non- proteinuric woman

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Eclampsia

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Eclampsia is the occurrence of convulsion in a pre- eclamptic patient in the absence of coincidental neurological disease.

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Significant proteinuria

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Significant Proteinuria is urine protein of more than 300mg in 24hrs or above 1g/l on dipsticks testing (2+) in two random urine specimen collected at least 6 hrs apart .

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Aetiology of pre-eclampsia

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This is often referred to as the disease of theories. It is a multisystemic disease. •The latest theory that may explain some of the problems in this disease is the failure of the second trophoblastic invasion of the spiral arteries of the uterus in the second trimester. The arteries retain their elastic and muscle component and are not converted to a high capacitance, low pressure vessels

.Other theories:•Immunologic theory•Imbalance in protanoids:- prostacycline and thromboxane.•Excessive placental mass•Circulating toxins

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Risk factors for pre-eclampsia

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•Patient <20 or> 35 yrs of age (Extremes of age)

•Hx in a first degree relative.

•Molar pregnancy

•First pregnancy with a new partner

•Diabetes in pregnancy

•Chronic renal disease

•Chronic hypertension

•Maternal obesity(BMI >32)

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Clinical features of pre-eclampsia

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Pre –eclampsia can be mild or severe. Mild disease is usually asymptomatic and is diagnosed during routine antenatal screening by finding raised BP and proteinuria Symptoms of severe pre- eclampsia are:- headache, dizziness, drowsiness, tinnitus, tachycardia, fever, diplopia, blurred vision, scotoma, epigastric pain, nausea, vomiting, oliguria, anuria, haematuria, signs include hyper-reflexia, Clonus ,papilloedema, epigastric tenderness, oedema and raised BP.

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Investigations for pre-eclampsia

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Pcv (Haemoconcentration) Platelet count, clotting profile, Urinalysis, 24 hr urine protein, LFT, SEUC, serum uric acid, grouping and cross matching of blood, abdominal USS. .

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Treatment of pre-eclampsia

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TREATMENT OF P-E This depends on the severity and the gestational age of the pregnancy. Once the pregnancy is term, consider delivery no matter the severity blc the rate of disease progression is not predictable

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Management of preterm with mild P-E (BP >140/90 <160/110)

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•Admit for closer observation for the persistence of hypertension, persistence of proteinuria, IUGR, abnormal lab results. •If the condition is not worsening conservative management is continued until fetal lung maturity is achieved during which delivery can be done.

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Management of severe pre-eclampsia (BP>/= 160/110 or proteinuria of up to (++) or >1g/L in the absence of UTI)

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•Signs & symptoms include epigastric pain, headache, hyper-reflexia, clonus, eye signs, altered consciousness, IUGR, oliguria, HELLP syndrome. •The Principles of management include control of hypertension, prevention of fits, safe mother followed by delivery of a live matured baby.• Delivery is the only cure (IOL or LSCS)•Strict Fluid balance.•Stabilize the BP using agents like hydrallazine, methyldopa, Nifedipine, Labetalol; chlormethiazole(Hemnevarine)•Prevent fit by using Mgso4 .•If the fetal lung has not yet matured give steroids like Dexamethasone or Betamethasone to reduce perinatal mortality.

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When can eclampsia occur

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During antenatal, Intrapartum or postpartum period up to 10 days postpartum

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Commonest type of eclampsia in Nigeria

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Intrapartum type

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Incidence & etiology of eclampsia

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Varies widely from 1 in 100 to 1 in 3,448 pregnancies

Aetiology: Unknown but usually follows pre-eclampsia. The pathophysiology is thought to involve cerebral vasospasm leading to ischemia, disruption of BBB and cerebral oedema. It does not depend on the level of BP.

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Clinical features of severe preeclampsia/ imminent eclampsia

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Headache, dizziness, blurring of vision epigastric pain (stretching of the Glisson's capsule ff hepatocellular necrosis, ischemia or subcapsular hemorrhage), nausea, vomiting, clonus, hyper-reflexia, oliguria, pulmonary edema, macroangiopathic hemolytic anaemia, elevated liver enzyme, elevated serum creatinine level, platelet count less than 100×10^6, diastolic BP greater than or equal to 110mmHg and/or systolic BP greater than or equal to 160mmHg

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Investigations for eclampsia

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Investigations: these are to assess severity and prepare the patient for possible LSCS. They include Hb, Urinalysis, platelet count, bedside clothing time, prothrombin time, LFT, SEUC, serum uric acid, blood grouping and cross matching.

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Treatment of eclampsia

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This involves the stabilization of the patient and delivery by the fastest and safest means. The G.A. is no longer considered once eclampsia has occurred. The treatment includes:- clearing and maintaining the airway, control and prevention of further fits, blood pressure control and maintaining balanced fluid input/output then delivery.

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Clearing & maintaining the airway in eclampsia

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AIRWAY:- use suction machine to clear secretions. Insert gag to avoid tongue biting. Avoid gag reflex which can lead to aspiration.

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Management of fit in eclampsia

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Mgt of fit: This can be done with Mgso4, Diazepam, phenobarb, lytic cocktail etc. Evidence has shown that Mgs04 is the best b/c it can prevent and abort ongoing seizure. It also does not affect the fetus. It can be given by either I.V. or I.M. routes. The various regimens for giving Mgs04 include:- 1. Pritchard (I.M &I.V) 14g loading dose with 5g maintenance dose 4hrly I.M. 2. Zuspan (IV) 3. Sibai (IV).

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Pritchard regimen

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Pritchard regimen is the one we use in our environment because the maintenance dose is given I.m and also risk of toxicity is lower. In the Pritchard Regimen, the loading bolus dose of 4 g of 50% MgSO4 is given slowly intravenously in 100-150ml of normal saline over 15 minutes and this is followed by 10 g given intramuscularly (5 g in each buttock). Subsequently, 5 g maintenance is given intramuscularly into alternate buttocks every 4 h. Continue Mgs04 until 24hrs after the last fit or after delivery whichever that occurs last.

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Indicators for monitoring MgSO4 toxicity

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1. Urine output (<100ml/4hrs or >/= 25-30ml/hour)

2. Respiratory rate ( < 16 cycles/min).

3. Knee jerk (Depression). First sign of MgSO4 toxicity is loss of deep tendon reflex

4. Serum level of Mgso4 (Biochemical) 2-4 mmol/l is the therapeutic range.

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Management of MgSO4 toxicity

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This is managed by giving 10ml of 10% Calcium gluconate solution slowly over 5mins intravenously. This drug must be handy whenever Mgso4 is being used.

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Blood pressure control in eclampsia

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The commonest drug used to control Bp in eclampsia is hydralazine injection which is given as 5mg boluses slowly every 20-30mins. Aim at BP of 90-100 diastolic and 140-150 systolic. Labetalol can be used but it is less available. Monitor Bp every 5mins once you are giving a patient hydralazine.

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Fluid management in eclampsia

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Fluid mgt: Monitor fluid input/output. Limit fluid input to 2litres/24hrs.

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Points to take note of in management of eclampsia

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•Delivery is the only cure of P.E &E.

•Drugs like antihypertensive only mask the signs but does not prevent disease progression.

•In status eclampticus, the pt can be paralysed and artificially ventilated.

•Avoid using ergometrine in the mgt of 3rd stage of labour in P.E or E because it increases the mean arterial pressure predisposing the woman to cerebrovascular accident.

•Keep the pt under close monitoring for at least 24hrs after delivery

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Complications of P-E & eclampsia

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1. Maternal: C.V.A., DIC, ARF, Liver rupture, heart failure, pulmonary edema, increases c/s rate and death.

2. Fetal: Abruptio placetae, IUGR, Oligohydramnios, placental infarcts, utero- placental insufficiency, prematurity, stillbirths, neonatal deaths.

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Delivery option

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DELIVERY: Route depends on the Cervical status. Choose the fastest and safest route. Vaginal route is safer if it can be achieved fast enough.

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Prevention of P-E

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Low dose aspirin started early after the first trimester in people at risk has been found to be preventive or delay the onset. Not useful if the disease has started before the drug is started. Others like Ca, Vit C & E are inconclusive

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Prognosis of Eclampsia

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PROGNOSIS: Recurrence rate of Eclampsia has been reported at 15.6%.

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Type of anaesthesia used during c/s in pre-eclamptic patients

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Local-regional anesthesia

This is because with general anaesthesia, endo-tracheal intubation will lead to the release of endogenous adrenaline/epinephrine leading to a sudden rise in BP that may aggravate the clinical condition

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Observations recommended during conservative management of pre-eclampsia

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1. Frequent BP monitoring depending on the degree of Hypertension

2. Daily urine protein estimation

3. Serial fundal height estimation to monitor fetal growth (weekly)

4. Features of imminent eclampsia should also be inquired into or looked out for

5. Specific obstetric care will include feto-maternal surveillance: monitor fetal heart rate, ask the woman to keep daily fetal kick, Cardiotocography weekly, serial USS 2 weekly to access for fetal growth

Another fetal surveillance comprises biophysical profile (2 weekly) & Doppler studies (4 weekly)

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Mechanism of action of Magnesium Sulphate

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Has peripheral and central mechanism of action

Central action: it is a cerebral vasodilator and a blocker of N-methyl-D-aspartate (NMDA) receptors in the brain, the pathway for anoxic cell damage

Peripheral action: it competitively inhibits the influx of calcium ion into the sarcoplasm of the smooth muscle thereby preventing actin-myosin action