CHAPTER 12 HYPERTENSION IN SPECIAL GROUPS HYPERTENSION IN PREGNANCY

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1 CHAPTER 12 HYPERTENSION IN SPECIAL GROUPS HYPERTENSION IN PREGNANCY v Mild preeclampsia is managed by close observation of the mother and fetus preferably in hospital. If the diastolic blood pressure remains persistently >100 mmhg, oral antihypertensive drug therapy is instituted. v Severe preeclampsia (SBP > 169 mmhg and/or DBP > 109 mmhg) is a medical emergency chiefly because of the high risk of maternal death and disability associated with intracerebral hemorrhage. The mother should be hospitalized for rapid lowering of the blood pressure using IV hydralazine, anticonvulsant therapy, and timely induction of labor after stabilization of the blood pressure. v The oral antihypertensive drug of choice in pregnancy is methyldopa. Alternatives include b- blockers, labetalol, and nifedipine. Diuretics are better avoided. ACE-inhibitors and angiotensin receptor blockers are absolutely contraindicated. v The drug of choice for parentral therapy is hydralazine. Possible alternatives include nitroglycerin and labetalol. v All antihypertensive drugs which are excreted in breast milk are present in very low concentrations except atenolol and nifedipine which attain high levels in breast milk and should be avoided in lactating mothers. Hypertension complicates about 7-10% of all pregnancies. Apart from being the most common medical complication of pregnancy, it is the leading cause of maternal morbidity and mortality worldwide. DEFINITIONS AND CLASSIFICATION There are four major hypertensive disorders in pregnancy: 1. Preeclampsia- eclampsia. 2. Chronic preexisting hypertension. 3. Preeclampsia superimposed on chronic hypertension.

2 4. Gestational hypertension. Hypertension is defined as blood pressure exceeding 140/90 mmhg. Diastolic blood pressure is measured at Korotkov phase V. Chronic preexisting hypertension: hypertension that predates pregnancy or a blood pressure > 140/90 which develops before the 20 th week of gestation. Rarely high blood pressure is the result of secondary causes as renal parenchymal disease. Gestational hypertension: is transient mild hypertension during the third trimester. It carries little risk to the mother or fetus. The hypertension typically resolves shortly after delivery, but tends to recur with subsequent pregnancies and may represent a risk factor for future development of essential hypertension. Preeclampsia: hypertension associated with proteinuria and generalized oedema which develops after the 20 th week of gestation. Eclampsia: the development of convulsions unrelated to other cerebral conditions during the course of preeclampsia. PREECLAMPSIA- ECLAMPSIA Preeclampsia complicates 3-14% of all pregnancies. Eclampsia occurs at a variable incidence of 1/300 to 1/3000 deliveries. Clinical Manifestations More common in nulliparas, older multiparas, hydatiform mole, twins and diabetic women. Proteinuria ( 300 mg/d) is abnormal in pregnancy. it may be absent in early preeclampsia. Oedema alone is not abnormal in pregnancy. Elcampsia does not necessarily correlate with the severe features of hypertension. So, all women with preeclampsia are at risk. Ominous features in women with preeclampsia are listed in table 18.

3 Table 18. Ominous Features in Preeclampsia Systolic blood pressure >169 mmhg Diastolic blood pressure > 109 mmhg Proteinuria 2 gm/day or spot urine protein > 100 mg/dl Increasing serum creatinine (> 2 mg/dl) Platelet count < /mm3 Evidence of haemolysis Epigastric or right upper abdominal pain Severe headache, or other cerebral signs Congestive heart failure Retinal hemorrhage, exudates, or papilloedema Intrauterine fetal growth retardation Management Non pharmacologic Management and Preventive Measures Adequate periods of rest. Normal diet. Salt restriction is not recommended. Weight reduction is not advised, since it may be associated with reduced fetal birth weight. Calcium supplementation (2 gm/day) may reduce the incidence of pregnancy related hypertension. There is no sufficient evidence to support the use of low-dose aspirin to prevent preeclampsia. Mild Hypertension There is no evidence that antihypertensive drug therapy alters maternal or foetal outcome. Pregnancy is allowed to mature as long as blood pressure is controlled and other signs of severe preeclampsia are absent. Patients with a diastolic pressure of mmhg should be put under close observation. A short period of hospitalization may be required. If the diastolic blood pressure remains persistently > 100 mmhg, oral antihypertensive therapy can be started. Methyldopa is the drug of choice. Possible alternatives include β- blockers, labetalol and long acting nifedipine.

4 Severe Hypertension Patients with systolic blood pressure >169 or diastolic blood pressure > 109 mmhg should be hospitalized. Management includes rapid lowering of blood pressure, prophylactic anticonvulsant therapy and timely induction of labour. In patients with ominous features of preeclampsia (Table 1), immediate delivery is mandatory. IV hydralazine is the drug of choice. Refractory cases can be given IV nitroglycerin, or IV labetalol. IV magnesium sulfate is the drug of choice for preventing eclamptic convulsions. It is administrated slowly as a loading dose of 6 gm diluted in 150 ml glucose 5% over administered minutes followed by continuous infusion of 2 gm/hr. MANAGEMENT OF CHRONIC PREEXISTING HYPERTENSION Preexisting hypertension is managed according to the same principles applied for management of preeclampsia. In general, patients can continue their previous medication except for ACE-I and Angiotensin receptor blockers. In patients with mild hypertension, the threshold to start drug therapy should be lowered to 140/90 mmhg under the following conditions: - Evidence of target organ damage. - Presence of intrinsic renal disease. - Preeclampsia superimposed on chronic hypertension. ANTIHYPERTENSIVE DRUGS IN PREGNANCY Oral Drug Therapy Methyldopa This is the most widely used antihypertensive drug in pregnancy because of its long established safety to the foetus. The total daily dose varies from mg. b - Blockers Metoprolol ( mg) and oxprenolol ( mg), are safe and effective when used in late pregnancy. An increased incidence of intrauterine growth retardation has been reported when treatment was started in early or mid

5 pregnancy. Other adverse effects to the fetus include bradycardia, hypoglycemia, and transient neonatal apnea. Atenolol is not the β- blocker of choice in pregnancy. Labetalol Labetalol (combined α and β- blocker) decreases the peripheral vascular resistance with little effect on maternal heart rate. It appears to be safe to the fetus although it was associated with intrauterine growth retardation. The oral daily dose varies from mg. Calcium Channel Blockers Nifedipine retard is used in a dose of mg bid. It may decreases uterine contractions and prolongs the course of labour. Drug interaction with magnesium sulfate may cause severe hypotension. Diuretics Diuretics should be avoided in pregnancy because of its relatively low efficacy, risk of hypovolemia, stimulation of the renin-angiotensin system, hyperuricemia, hyponatremia and neonatal thrombocytopenia. Patients with chronic hypertension already on diuretic therapy can probably continue taking it through pregnancy as long as volume depletion can be avoided. The only established indication of diuretics in preeclampsia is the use of frusemide in the postpartum period to treat fluid overload and pulmonary oedema. ACE-Inhibitors and Angiotensin Receptor Blockers These drugs are absolutely contraindicated in pregnancy since they cause a significant reduction in placental blood flow, foetal deformity, neonatal renal failure and intrauterine foetal death. Hydralazine Hydralazine is the parentral drug of choice for management of severe hypertension in pregnancy. Action starts in minutes, with a peak effect in 60 minutes and a duration of 2-4 hours. The total dose should not exceed mg.

6 Dose: given in intermittent IV boluses starting by 5 mg and increasing to 10 mg, and if necessary repeated every minutes until the diastolic blood pressure is reduced below 100 mmhg. Side Effects: - Maternal tachycardia, headache, tremors, vomiting, and salt and water retention. - Excessive lowering of blood pressure is associated with reduced placental blood flow and foetal distress. Nitroglycerin IV nitroglycerin is indicated only in patients who do not respond adequately to hydralazine. Careful monitoring is necessary to avoid abrupt hypotension in volume depleted women which may lead to foetal distress. Labetalol Given slowly as 20 mg bolus repeated every 10 minutes to a total dose of 300 mg. Sodium Nitroprusside This potent vasodilator is generally avoided in pregnancy since even small doses are associated with abrupt hypotension and paradoxical bradycardia in volume-depleted preeclamptic patients. It carries the risk of thiacyonate and cyanide toxicity to the mother and foetus. Its use should be restricted to refractory hypertensive crisis which failed to respond to other agents. The initial infusion dose should be 0.2 µg/kg/min. HYPERTENSION AND LACTATION Breast-feeding does not increase blood pressure in the nursing mother. Bromocryptine which is used to suppress lactation may induce hypertension. All antihypertensive drugs are excreted in breast milk. Most are present in very low concentrations except atenolol and nifedipine which attain high levels in breast milk and should be avoided in lactating mothers.