HYPERTENSION IN PREGNANCY

Check the sphygmomanometers and make sure that your staff know how to use them. If the circumference of a patient’s arm is >30 cm, use a wide long cuff. Don’t diagnose a high blood pressure on one measurement alone. Use the fourth sound of Korotkoff to measure her diastolic blood pressure. This is the point at which they become muffled, rather than when they disappear (the fifth sound).

ESSENTIAL HYPERTENSION

Suspect essential hypertension if her blood pressure is raised before 28 weeks. If her diastolic blood pressure is consistently >90 mm Hg before 28 weeks, she ideally needs treatment with methyldopa (’Aldomet’), but this is not essential.

MILD AND MODERATE GESTATIONAL HYPERTENSION

This is the patient with a blood pressure of <160/100 mm Hg and no proteinuria. Risk factors which suggest that her gestational hypertension may progress are: (1) A history of previous IUGR, a previous intrauterine death, or a low birth-weight baby. (2) Signs of IUGR in this pregnancy.

Rest her. She need not be in bed all the time, but when she is in bed, she should be lying on her side, not on her back. Watch for the signs and symptoms of impending eclampsia. Record her blood pressure 4-hourly, and test her urine for protein daily. If her blood pressure settles, and she has no danger signs (proteinuria, headache) she can go home.

Ideally, induce her at 38 weeks, or as soon as her surfactant test (19.2) is positive. If you are in doubt about the maturity of her baby, it is probably safe to wait until term.

CAUTION! (1) Primigravidae 18 years old or less are at special risk, so treat them in a grade higher than their symptoms suggest. For example, consider a primigravida aged 16 with a blood pressure of 140/90 and no protein in her urine as having moderate hypertension. Consider a primigravida of 15 with a blood pressure of 150/100 as having severe hypertension. (2) Mild gestational hypertension can progress to eclampsia in a few days. (3) A primigravida can go into labour at term with no signs of gestational hypertension. Her blood pressure can rise rapidly during labour, and fits appear before she has any protein in her urine (unusual).

SEVERE GESTATIONAL HYPERTENSION (pre–eclampsia)

LESS THAN 35 WEEKS. She has a blood pressure of >160/110 mm Hg, and/or proteinuria of ’2+’ (0.45–1 g/l) or more, on more than one occasion, but she has no symptoms—headaches, visual disturbances, epigastric pain, or fits. If she does have them, treat her as for eclampsia (see below).

Admit her, and sedate her heavily with oral phenobarbitone (60 mg 6 hourly, or 30 to 60 mg twice daily), or sodium phenobarbitone 200 mg intramuscularly. If her blood pressure settles, treat her with phenobarbitone by mouth, until her baby is mature.

If her blood pressure does not settle, give her methyldopa, starting with 250 mg 3 times daily, and gradually increasing; maximum dose 3 g daily. It works slowly, and will not have much effect for 2 days.

Maternal indications for terminating pregnancy: (1) Her blood pressure is uncontrollable (>160/110 mm Hg) in spite of 2 g of methyldopa daily. (2) Imminent signs of eclampsia (see below). (3) Signs of renal failure, with a rising blood urea and a falling urine output. Fetal indications for terminating pregnancy: (1) Severe IUGR (19.13) after 32 weeks with a viable baby. (2) The decision to terminate pregnancy is also dependent on its duration, and the severity of her proteinuria. For example, proteinuria of <0.5 g/l at 28 weeks does not demand termination. Once it reaches 0.5 g/l, whatever the duration of pregnancy, it is a general rule that eclampsia will probably follow within 2 weeks, unless she is delivered sooner.

If her baby is alive, induce her; this is usually easy. Section her if there are difficulties (CPD, a breech, or a cervix which you are not able to ripen, etc.). If he is dead, spontaneous labour is likely in a few days, but induce her if necessary.

CAUTION! (1) Always admit her for antihypertensive treatment. (2) It does not invariably prevent eclampsia and abruption.

MORE THAN 35 WEEKS. Lower her blood pressure by one of the methods below, and terminate her pregancy if her cervix is favourable for induction.

ECLAMPSIA OR IMPENDING ECLAMPSIA

If she has fits, she has eclampsia. The signs of impending eclampsia are: a blood pressure of >160/110 mm Hg or a rapidly increasing blood pressure, proteinuria >2+, oliguria (<400 ml daily), headaches, visual disturbances, and epigastric pain. Muscle twitches and exaggerated reflexes indicate that fits are about to begin. Aim to deliver the baby. Give her magnesium sulphate, or sedate her heavily.

CAUTION! (1) Before you diagnose gestational hypertension as the cause of fits or coma, don’t forget that they can be caused by cerebral malaria, meningitis, or epilepsy, and also by less common causes. Be especially careful if her blood pressure is normal and she has little proteinuria. If her fits really are unexplained, treat her as if she had eclampsia. (2) Eclampsia is rare before 26 weeks, or more than two days after delivery. (3) Meningitis may produce fits and little neck stiffness in a pregnant patient. (4) The intensive treatment of cerebral malaria is not the same as the ”routine’ treatment of ordinary malaria (17.2). (3) Record her blood pressure not less than 4-hourly, and if necessary half-hourly.

An eclamptic fit is a grand mal epileptic convulsion. A tonic phase in which all the muscles of the body contract, so that it becomes rigid, is followed by a clonic phase of rhythmic muscular contractions. She becomes unconscious with the fit, and remains so for a variable time afterwards. When she has a fit, clear her airway and insert an oral airway. Give her diazepam 10 to 20 mg intravenously slowly by bolus injection (or give her chlormethiazole, see below). Then give her: (1) magnesium sulphate. Or (2) phenytoin. Or (3) heavy sedation with chlormethiazole. Or (4) the lytic cocktail. Or (5) diazepam as an infusion.

IF YOU ARE USING MAGNESIUM SULPHATE, you will need 20% and 50% sterile solutions, calcium gluconate 10%, and a tendon hammer. If you have no sterile magnesium sulphate, make it. Most brands of magnesium sulphate, including magnesium sulphate BP, are satisfactory. Be sure to monitor her carefully, because an overdose can cause respiratory failure. Inject 4 g of magnesium sulphate (20 ml of a 20% solution) intravenously over a period of 3 to 5 minutes. Then immediately give her 10 g intramuscularly (10 ml of a 50% solution deeply into each buttock). This loading dose of 14 g will usually control her fits immediately. If they don’t stop, give her diazepam 10 to 20 mg by bolus intravenous injection in addition.

As a maintenance dose, every 4 hours afterwards, give her 5 g of magnesium sulphate into alternate buttocks, but only provided that: (1) her respirations are more than 16 per minute, (2) her knee-jerks are present, and (3) she has excreted at least 100 ml of urine since the last dose. Alternatively, give her a drip of 1 g/hour. Continue this regime until 48 hours after delivery.

CAUTION! (1) If her respiration becomes depressed while she is having magnesium sulphate, give her 10 ml of 10% calcium gluconate intravenously slowly over not less than 10 minutes. This is an instant antidote, so it must be available. (2) Stick to one anticonvulsant regime and don’t mix them. (2) If you are giving her magnesium sulphate (or phenytoin), there is no need to sedate her.

IF YOU ARE USING PHENYTOIN, give an initial dose of 10 mg/kg slowly intravenously, followed 2 hours later by 5 mg/kg intravenously. Maintain her on oral or intravenous doses of 200 mg 8-hourly for 3 or 4 days.

CAUTION! There is a small risk of inducing cardiac arrhythmias with intravenous phenytoin, so give it very slowly over 5 minutes.

IF YOU ARE SEDATING HER, adjust the level of sedation carefully. She should sleep, but just be able to respond to her name if you rouse her. If she talks coherently when roused, she is too light. If she does not respond at all, she is too deep. Provided she does not become too deep, her laryngeal reflexes will be adequately preserved. She usually needs to be sedated for about 4 days, and often for less. This includes 24 hours for control, time to induce labour and deliver her, and 48 hours afterwards (see below).

CAUTION! (1) If with any of the sedative methods, particularly it is said chlormethiazole, she becomes restless and perhaps uncontrollable, she may be ’too deep’ rather than ’too light’, and may be in the excitement stage of anaesthesia (equivalent to Stage Two with ether, A 11.2). If this happens, give her less not more sedation. (2) You are giving agents which can produce anaesthesia in higher doses. So if she gets too deep be prepared to intubate her.

If you are using chlormethiazole (’Heminevrin’), in severe cases, give it as a rapid infusion of 8 g/l until she is asleep and her jaw sags. Pass a (Ryle’s) stomach tube, and give her 2 g intragastrically (aspirate the oily capsules, and pass the contents down the tube). Insert an oral airway to prevent her tongue falling back. Give her pethidine as necessary for analgesia also. Regulate the intravenous drip so that she can just be roused. Use the intragastric route as the main one, and the intravenous one for fine adjustment. This will economize in intravenous fluids, and avoid overloading her. She may need 24 g of chlormethiazole or more each 24 hours.

If you are using the lytic cocktail, give her pethidine 50 mg, chlorpromazine 50 mg, and promethazine 50 mg intramuscularly 4 to 6-hourly. This is easy, effective, and cheap, but they are poor anticonvulsants. Alternatively, give the first dose by bolus intravenous injection and then give the drugs intramuscularly. Don’t exceed chlorpromazine 300 mg in 24 hours.

If you are using diazepam for continued sedation, give her 40 mg in 500 ml of 5% dextrose (for the use of intravenous diazepam see A 2.8). Start at 30 drops a minute, and maintain heavy sedation as for chlormethiazole. Unfortunately, it is difficult to maintain the drip at a constant speed, and you may find other methods easier.

CAUTION! Give her diazepam intravenously or orally. Don’t try to give it intramuscularly: its absorption is unpredictable, and it acts more slowly than oral diazepam. If she is unconscious and cannot swallow, give it down a tube.

BLOOD PRESSURE. If, when you have controlled her fits, her blood pressure is more than 170/110 mm Hg, give her hydralazine (’Apresoline’); this is the most suitable drug, but it may cause tachycardia. Give her 10 mg intramuscularly. Measure her blood pressure after an hour, and if it is >160/110, give her another 10 mg. Continue to monitor her blood pressure hourly, and whenever it is >160/110 give her another 10 mg. Explain this regime to the midwives, and let them continue. This is much easier than giving it intravenously.

CAUTION! (1) Don’t use methyldopa, it is too slow-acting to control hypertension in an emergency. (4) Don’t try to induce her if she has a blood pressure of more than 170/110 mm, without first lowering it, or she may have fits during labour.

FLUID BALANCE. Monitor her carefully, and keep a chart like that in Fig. A 15-5. Keep the fluid balance part of it accurately, and pass an indwelling catheter. Take care not to overload her circulation. You can easily cause pulmonary oedema by giving her too much fluid. As soon as she is delivered she will shift the oedema fluid into her circulation. There are two regimes:

The ’dry regime’

Give her a litre of fluid in 24 hours and don’t worry too much about oliguria: she will eventually get a diuresis.

The ’wet regime’

is sometimes advised to maintain renal perfusion and a good urine output. There is however a danger of fluid overload and pulmonary oedema. It is probably safer to err on the side of undertransfusion. Give her plasma expanders (dextran or albumen 2 l/24 hours) or 2 litres of intravenous fluid in 24 hours. Give her her normal requirement of one litre of Ringer’s lactate or saline, and 1 litre of 5% dextrose intravenously in 24 hours. Add to this a volume of Ringer’s lactate, or saline, equal to any vomit or diarrhoea, etc., that she may have. Aim for a minimum urine output of 30 ml/hour. There is a danger of causing pulmonary oedema with this regime, especially if nursing is poor. So watch her central venous pressure, (preferably with a CVP line), and maintain her urine output >30 ml/hr. If it falls below this, give her intravenous mannitol (A 15.1), or frusemide 20 to 40 mg at a rate not exceeding 4 mg/minute.

HYPERPYREXIA is a serious risk, especially in hot climates. Record her rectal temperature 4-hourly, and if necessary hourly. If it rises over 39C, use tepid sponging. If it reaches 41C, remove all clothing, cool her with a wet sheet in contact with as much of her skin as possible, and turn a fan on her. This will cool her 0.5]C in 10 minutes. An irreversible hyperpyrexia of >43C indicates brain damage.

NURSING is critical and needs to be expert and continuous. Nurse her in a side room, or in the labour ward. A patient with severe gestational hypertension ideally needs a nurse to herself day and night, with no other duties except to turn her every 1–2 hours, to aspirate her pharynx, and to measure and chart her blood pressure and her urine output. She may die from the aspiration of secretions or vomit, so lay her in the recovery position (51-2), and keep a sucker handy. Protect her corneae: keep her eyes closed, if necessary with tape across her eyelids. Watch and treat her pressure areas (64.15).

VAGINAL DELIVERY. Provided there are no contraindications to vaginal delivery, induce her (19.3) and deliver her vaginally as soon as you can, when her fits and her blood pressure are controlled, and her general condition is stable. Don’t delay. To induce her, rupture her membranes, and then give her an oxytocin drip (M 22.2). (Watch the volume of intravenous fluid you are giving her.) If you give her >1 l/24 hours, keep her urine flow >30 ml/hour. If you cannot insert a finger to rupture her membranes, you can insert a Foley catheter to ripen her cervix (19.3), but section may be wiser.

Alternatively, if there is less urgency for delivery, and the condition of her cervix is unfavourable, insert prostaglandin gel (2 mg) in a diaphragm to induce contractions and soften her cervix. Or proceed immediately to section her.

CAESAREAN SECTION is indicated if she has: (1) an unfavourable cervix, (2) a breech, (3) CPD, or (4) the scar from a previous Caesarean section. (5) If induction is not followed by active labour in 8 hours. (6) If she does not progress in labour.

AFTER DELIVERY, continue her hypotensive, anticonvulsive, and sedative drugs for 48 hours, after which the risk of fits is very low. Don’t discharge her until her diastolic blood pressure is <100 mm Hg.

DIFFICULTIES WITH GESTATIONAL HYPERTENSION

If your CIRCUMSTANCES ARE VERY DIFFICULT, such that you may not even have a sphygmomanometer, so that the routine monitoring of patients described above is impractical: (1) Encourage them to come into hospital early if they have the warning symptoms of eclampsia (headaches, visual disturbances and epigastric pain). (2) Test their urine for protein, and encourage them to do it at home with test papers. A urine protein of >0.25 g is likely to indicate gestational hypertension.

If a patient has GENERALIZED OEDEMA during pregnancy, she is at increased risk of gestational hypertension, so monitor her blood pressure and urine for protein with extra care.

If she is not pregnant and has ESSENTIAL HYPERTENSION with a diastolic pressure of >110 mm Hg (uncommon), counsel her about the possible problems of hypertension during pregnancy. If you treat her hypertension before and during pregnancy (methyldopa or propanolol are suitable), her baby’s prognosis is quite good, and her own risks are very small unless she has renal failure. She runs a higher risk of gestational hypertension, but renal problems seldom develop for the first time, although they may get worse. She can expect more problems in pregnancy (eclampsia and abruption), but the long-term prognosis of the disease, including her life-expectancy is not affected.

If you have had to give her MORE THAN 30 mg OF DIAZEPAM within 15 hours of delivery, her baby may have APNOEIC ATTACKS (a major problem), hypotonia, reluctance to suck, or an impaired metabolic response to cold. So manage him with particular care (19.12). At the time of writing there is no specific ’antidiazepam’ licensed, although one is under development.

If her URINE VOLUME FALLS to less than 500 ml in 24 hours: (1) She may be dehydrated. Provided that her lung fields are clear and there is no chance of cardiac failure, give her a litre of 5% glucose during about an hour. She is in more danger of pulmonary oedema from too much fluid than of renal failure from too little fluid. If you cannot be certain that she has not got a raised central venous pressure, don’t push fluids. (2) If this does not produce a diuresis, she has renal failure. Give her 100 ml of 20% mannitol over 10 minutes (A 15.1). If this fails, try frusemide 80 mg intravenously, repeated in 2 to 4 hours if it is not effective. If this too fails to restore her urine output, limit her intake to 500 ml in 24 hours plus a volume equal to her urine output. See also 53.3. If she has renal impairment and subsequently has a diuresis, she will need extra sodium and potassium (53.3).

If she starts HYPERVENTILATING or is CYANOSED, (1) She may be developing pulmonary oedema, so sit her up and give a diuretic and oxygen. Or, (2) she may be acidotic (uncommon). If so, correct her acidosis cautiously with 50 to 150 mmol (50 to 150 ml of an 8.4% solution) of sodium bicarbonate intravenously (A 15.1).

If her UTERUS BECOMES TENDER, her blood pressure and urinary output fall, and the fetal heartbeat disappears (uncommon), suspect abruption. Restore her blood volume with Ringer’s lactate, or saline, and blood in appropriate proportions. For this to be safe, monitor her CVP (A 19.2). Hasten delivery.

If she becomes cyanosed or develops PULMONARY OEDEMA, give her continuous oxygen and frusemide 20 to 40 mg intravenously. The need to observe cyanosis is one reason why she must not be nursed in a dark room.

If her FITS CONTINUE despite heavy sedation and adequate doses of magnesium sulphate, make sure the diagnosis of eclampsia is correct (see above), that her blood pressure is adequately controlled, and that she is not in pain. Try another sedative, for example paraldehyde 10 ml intramuscularly. If even this fails, paralyse her with a muscle-relaxant and ventilate her with IPPV (A 13.2, A 19.4), using a cuffed tracheal tube (rarely necessary).

If she goes into prolonged deep COMA, make sure you have not oversedated her. Keep her adequately oxygenated. Intubate her to maintain a clear airway, and suck out her trachea. Start IPPV when necessary (rare). She has probably had a cerebrovascular accident.

If her BLOOD PRESSURE STAYS HIGH 48 HOURS AFTER DELIVERY, treatment depends on how high it is. If it is >160/120, acute complications (a cerebrovascular accident or renal failure) are likely. Lower it actively. If it is <160/120, maintain mild sedation for a few days. It will probably fall spontaneously. See her in 6 weeks. If it remains high (diastolic pressure >110 mmHg), consider long-term medical treatment with all its problems and complications, which she will be unlikely to accept. In most countries of the world the cost and inconvenience of long-term antihypertensive treatment probably outweighs its benefits.

If her blood pressure is noticed to be HIGH FOR THE FIRST TIME AFTER DELIVERY, or she has FITS AFTER DELIVERY, it may have been high before delivery, or it may have risen for the first time afterwards. She may develop eclampsia, especially within 48 hours of delivery; after this time the risks of a first fit are minimal. If she has signs of severe gestational hypertension, treat her for it with magnesium sulphate or sedation as above. If her blood pressure remains high, see above.

If she has ALREADY ASPIRATED secretions before she was admitted, suck her out as best you can (9.11), raise the foot of her bed, and give her antibiotics.