Regarding anti-D prophylaxis during first trimester pregnancy in a Rh negative female, which ONE of the following is the MOST CORRECT?
Answer: B: Rh D immunoglobulin (RhIG) is usually given to Rh D negative women with no preformed anti-D antibodies during pregnancy if they experience a ‘sensitizing’ event in which there is a risk of fetal blood crossing into the maternal circulation. The administration of RhIG has been shown to decrease maternal sensitization and fetal complications during late pregnancy; however, it is unclear whether first trimester events lead to sensitization as there is a paucity of well-designed studies addressing this issue.
A 2003 National Health and Medical Research Council (NHMRC) report16 recommends the administration of RhIG to every Rh D negative women in the first trimester (up to and including 12 weeks’ gestation) with no preformed anti-D to ensure adequate protection against immunization after the following sensitizing events (level IV evidence):
The report further elaborates on the use of RhIG in miscarriage stating that there is insufficient evidence to support the use of RhIG in bleeding prior to 12 weeks’ gestation in an ongoing pregnancy (threatened miscarriage), but if the pregnancy then requires curettage, or if the bleeding is particularly heavy or associated with a visible subchorionic haemorrhage, these patients should be considered at higher risk of sensitization and RhIG given. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) guidelines for the use of RhIG in obstetrics are based on this report. The Australian Therapeutic Guidelines support the above four indications for RhIG in first trimester bleeding; however, it refers to ‘miscarriage’ only and does not extrapolate on threatened miscarriage. Regardless, the tradition of giving Rh prophylaxis to all Rh negative patients with first trimester bleeding, including threatened miscarriage, is well established among practitioners albeit not evidence based. Additionally, most expert opinion is in favour of RhIG administration during the first trimester due to the extremely low incidence of complications from RhIG administration and the potential grave risks of maternal sensitization that have been extrapolated from experience with late pregnancy bleeding and subsequent sensitization.
Because the volume of fetal cells potentially involved in the fetomaternal haemorrhage (FMH) is small, the recommended does of RhIG is 250 IU. For successful prophylaxis, Rh(D) immunoglobulin should be given as soon as possible after the sensitizing event but always within 72 hours (level I evidence). If RhIG has not been offered within 72 hours, a dose offered within up to 10 days may provide protection. Blood should be taken prior to administration to exclude the presence of antibodies. In cases of ongoing bleeding, it is recommended that RhIG be given every 6 weeks.
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Regarding administration of anti-D (RhIG) after the first trimester of pregnancy in Rh negative females, which ONE of the following is TRUE?
Answer: D: Current national recommendations for the administration of RhIG after sensitizing events beyond the first trimester include:
Studies have shown that Rh(D) immunoglobulin 100 IU is sufficient to protect against a FMH of 1.0 mL of fetal red cells (2.0 mL whole blood). The majority of fetal bleeds are <5 mL of red blood cells, therefore a dose of RhIG 625 IU is sufficient to protect against most cases of FMH but not all, and it is recommended that the magnitude of the FMH following a sensitizing event be quantified to ensure an adequate dose of Rh(D) immunoglobulin is offered, as more than one dose may be required. The Kleihauer-Betke acid elution test is one such test that is commonly used to establish the extent of FMH and requires the collection of 7 mL of maternal venous blood in an EDTA® tube.
The occurrence and degree of FMH after trauma is difficult to establish at the bedside. Since sensitization can occur in pregnant patients exposed to a transplacental haemorrhage of <0.1 mL, it seems sensible to administer RhIG to all pregnant patients following abdominal trauma. The recommended standard dose in Australian is 625 IU. The Kleihauer-Betke acid elution test can be performed in addition to assess if further doses of RhIG are required.
The Australian Rh immunoglobin product can only safely be given intra-muscularly. In some circumstances such as severe thrombocytopenia or a coagulation disorder, access to an intravenous Rh(D) preparation may be warranted. A quantity of intravenous Rh(D) immunoglobulin has been reserved for this purpose and is available from the Australian Red Cross Blood Service.
Regarding preeclampsia in pregnancy, which ONE of the following is TRUE?
Answer: B: Preeclampsia is a multisystem disorder usually diagnosed in the presence of hypertension associated with proteinuria after the 20th week of gestation in women known to be normotensive beforehand. Oedema is no longer included in the definition of preeclampsia because it is commonly found in many women with normal pregnancies. The International Society for the Study of Hypertension in pregnancy defines hypertension as ‘a diastolic BP of 90 mmHg or higher on 2 consecutive occasions at least 4 hours apart or a single diastolic BP greater than 110 mmHg’. Blood pressure during pregnancy should be measured with the patient in the sitting position or lying at a 45° angle with the arm at the level of the heart. Alternatively, the left lateral recumbent position can be used. An appropriate size cuff (length 1.5 times upper circumference or a cuff with a bladder that encircles 80% or more of the arm) should be used. A mercury sphygmanometer is preferred as it is more accurate than electronic devices. Phase V Korotkoff sound (sound disappearance) should be used to measure diastolic BP. Although the use of antihypertensive drugs in women with preeclampsia and severe rises in BP have been shown to prevent cerebrovascular problems, such treatment does not prevent or alter the natural course of the disease in women with mild-moderate elevations of BP. Antihypertensive therapy have been remarkably unsuccessful in improving fetal outcome or prolonging pregnancy.
Proteinuria is defined as the presence of ≥300 mg of protein in a 24-hour urine collection. This usually correlates with 1+ protein on a random urine dipstick. However, proteinuria may be variable at any given time and may not be detectable in a random urine specimen. Furthermore, it is important to be aware that preeclampsia may occur without proteinuria. Diagnosis in such cases rests on confirming hypertension and evidence of multisystem involvement.
A 24-year-old female presents to the ED with blurred vision and slight headache. She is 26 weeks pregnant. Her BP is 150/100 mmHg and a urine dipstix shows 1+ protein.
Which ONE of the following is the MOST appropriate?
Answer: D: This patient satisfies the criteria for severe preeclampsia and has signs of imminent eclampsia. Symptoms and signs suggestive of imminent eclampsia include headache, visual disturbances, epigastric/RUQ pain and hyperreflexia. However, about one-quarter of cases of eclampsia occur without preceding signs or symptoms suggestive of imminent eclampsia. The definition of severe preeclampsia is not standardized but most regard it as the presence of any one of the following in the setting of preeclampsia:
Severe preeclampsia is managed in the same way as eclampsia. The focus of treatment of severe preeclampsia is on the prevention of seizures (eclampsia) and treatment of hypertension to prevent permanent damage to maternal organs:
A 34-year-old female presents with a new onset generalized tonic–clonic seizure. She is 27 weeks pregnant.
Which ONE of the following is TRUE?
Answer: A: Eclampsia should be suspected and treated in any pregnant patient who is >20 weeks of gestation or <4 weeks postpartum who develops seizures. The diagnosis of eclampsia is secure in the presence of generalized oedema, hypertension, proteinuria and convulsions. While hypertension is considered the hallmark for the diagnosis of eclampsia, it may not always be present. The hypertension can be severe (≥160/110 mmHg) in 20–54% of cases or mild (140–160/ 90–110 mmHg) in 30–60% of cases.
However, in 16% of cases, hypertension may be absent, hence, although control of BP is important, it will not necessarily prevent or treat eclampsia. Similarly, the diagnosis of eclampsia is usually associated with proteinuria (at least 1 + on dipstick) but it may be absent in 14% of cases.
The standard of care for women with eclampsia is to use an anticonvulsant drug to control the immediate fit, and to continue maintenance treatment to prevent further seizures. Magnesium sulphate is the first-line treatment in termination of acute seizures as well as prevention of further seizures. It has been shown to be more effective than diazepam or phenytoin in the treatment and prophylaxis of eclamptic seizures. The use of phenytoin should be confined only to patients who have persistent seizures despite magnesium. Various regimes exist but a loading dose of magnesium 4–6 g is usually given over 10–20 minutes followed by a maintenance infusion of 2g/hour by intravenous infusion. Approximately 10% of eclamptic women will have a second convulsion after receiving magnesium sulfate. In these women, another bolus of 2 g magnesium sulfate can be given intravenously over 3–5 minutes.
The hypertension associated with eclampsia is often controlled adequately by terminating the seizures. Rapid lowering of BP can result in uterine hypoperfusion, so specific antihypertensive treatment is usually initiated only if the diastolic BP remains above 105 mmHg after control of seizures. Additionally, many patients do not require specific antihypertensive treatment after treatment with magnesium sulfate. Intravenous hydralazine is most commonly used in Australia at repeated doses of 2.5–10 mg every 20 minutes to keep the diastolic BP below 105 mmHg. Labetalol has also been reported to be safe and effective; however, the intravenous preparate is not available in Australia.
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