IN ASSOCIATION WITH THE NSPKU
Suzanne Ford NSPKU Dietitian for Adults Suzanne Ford is a Metabolic Dietitian working with Adults at North Bristol NHS Trust and also for the National Society of Phenylketonuria).
IMD WATCH
CASE STUDY: DIETETIC MANAGEMENT IN ORNITHINE TRANSCARBAMYLASE DEFICIENCY A 34-year-old female with an ornithine transcarbamylase deficiency planned to conceive. This article is an account of dietetic management before and during pregnancy and delivery. BACKGROUND This female patient is a carrier manifest of an X linked urea cycle disorder, ornithine transcarbamylase (OTC) deficiency. She is known to have c.217-1G>A mutation, which is a mutation associated with relatively little enzyme activity. The deficient enzyme places the individual at risk of hyperammonaemia which can lead to encephalopathy and death. Treatment of OTC deficiency is a safe protein diet (i.e. moderately low, with or without essential amino acids and micronutrient supplements), daily ammonia scavengers, an arginine supplement and, finally, glucose polymer emergency regimen to reduce the effects of catabolism.
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This patient has a history of decompensations - critical care and heroic measures were needed; the last hospital admission was at age 33 years old and she is under sixmonthly follow-up with her metabolic team. The patient’s medications were: • Sodium benzoate 16g in divided doses orally; • L-Arginine 6g daily orally; • B12 3 monthly intramuscular injection; • Calcichew D3 forte orally; • Forceval once daily orally. Dietary management centred on a moderate protein restriction; it is possible that the patient was not consistently compliant; she had hospital admissions for management of hyperammonaemia at age 15, 26, and 33. Her use of emergency regime was approximately once per year due to intercurrent illnesses. In inborn errors of metabolism the best outcomes are with planned pregnancy, so, in 2010, the patient and her husband had genetic counselling. They went on to have pre-implantation genetic diagnosis (funding was obtained from clinical commissioners). The patient underwent an obstetric and gynaecological assessment including cyst removal, super-ovulation and egg harvest, then in vitro fertilisation followed by genetic diagnosis of foetus and implantation. This was done twice to no avail. Following this, there was a natural conception of an affected male and termination in April 2015. After the termination, another natural pregnancy occurred, this time found to be female. DIETARY MANAGEMENT PRECONCEPTION AND FIRST TRIMESTER 1. The patient changed from taking a standard multivitamin to pregnancy multivitamin/ mineral, including 400ug folic acid and also an omega-3 supplement (containing 200mg preformed docosohexanoic acid). 2. Frequent detailed dietary assessment based on a preconception weight of 54kg, with advice for an intake of 45g protein (0.83g/kg) and approximately 1,670kcals daily. 3. There was very strong encouragement to take an emergency regimen (of 25% glucose polymer solution every two hours) if experiencing nausea or vomiting, and to contact the metabolic team/seek admission to A & E if this did not work for more than eight hours.
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IMD WATCH 4. I reiterated standard recommendations for food safety advice in pregnancy. 5. At eight weeks into pregnancy, I asked the patient to: a) start taking daily essential amino acid supplement (providing additional 5g protein); b) eat every three hours whilst awake - gave list of 200kcal snacks; c) increase carbohydrate intake, and ensure she was eating carbohydrate more frequently - this was strongly linked to the snacks, but also to ensure that she d) have 200mls of her emergency regimen drink (25% glucose polymer) every night at bedtime (9pm); e) get a suitable anti-emetic from her GP - she was prescribed cyclizine which is known to be safe in pregnancy; f) use fatigue management strategies as fatigue was a significant feature at this stage. When regular carbohydrate is needed, dietetic assessment should always include sleep patterns and sleep duration. METABOLIC DECOMPENSATION IN THE FIRST TRIMESTER At 9/40 this patient was admitted to ICU with an ammonia of 300, she was encephalopathic and uncooperative so was sedated, intubated and fed via a nasogastric tube, along with having intravenous ammonia scavengers - benzoate with butyrate, plus intravenous dextrose for extra calories. The feed was 12 hours Nutrison only, as after this time the sedation was lifted, the patient vomited out her nasogastric tube and declined a second tube. She had oral nutrition support (Fortisips no more than four daily) for day two to four of her admission and went home on day five. At this stage, the effects of metabolic decompensation on her foetus were unknown. Careful questioning is vital after a decompensation, as part of understanding causative factors and preventing future events. In this case, the aetiology was a reduced intake secondary to nausea and also tiredness, latter exacerbated by having taken cyclizine (antihistamine anti-emetics with potential sedative side effect). Preceding the decompensation, there had been over 14 hours with no carbohydrate intake. DIETARY ADVICE SECOND TRIMESTER Protein intake kept at ~45g/day (0.83g/kg)
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DIETARY ADVICE THIRD TRIMESTER • Increased total protein intake at 28/40 by increasing dietary protein to 50g/day. • 32/40 - further increase to 60g total protein - 0.9g/kg/day. Growth scan at 28/40 - abdominal circumference, head circumference and femur length as well as foetal, weight were all on 50th centile; four-weekly repeat growth scans showed good interval growth and always remained close to the 50th centile. PLAN FOR LABOUR • Induction of labour likely on estimated date of delivery, i.e. at 40/40 if the patient had not delivered naturally by then. • 10% IV dextrose to start on admission with medications, plus oral glucose polymer solution, to provide external calories for the effort of labour. • Regular anti-emetics administered to avoid vomiting and also IV antibiotics and paracetamol given to mother to prevent or damp down any metabolic stress.
PERI-PARTUM DIETARY MANAGEMENT PLAN • 2,500kcal if possible during labour/post labour. • ‘Sliding scale’ SOS25/snacks to meet above. • 25-30g protein daily peri-partum. • Low protein/high carbohydrate snack and meal options previously discussed. • Ensure fully prepared - glucose polymer in her hospital bag; low protein foods on standby. BEFORE DISCHARGE AND POST DISCHARGE • IV dextrose continued until eating and drinking well and was replaced with oral glucose polymer drinks until day five to six. • Ammonia monitoring - this was done daily day one to seven post-delivery. • Six- to 12-hourly ammonia monitoring if any increase occurred (there was one small increase only). • Discharge home on was on day 10 (the discharge was complicated by the daughter’s OTC status looking positive and in fact this was confirmed via genetics subsequently - neonatal ammonia levels are difficult to interpret). • Follow-up was three times per week in first week post discharge, and twice weekly ammonia levels for one month postpartum - the involution of the uterus (a large release of endogenous collagen, i.e. protein into the blood stream) can occur anytime between one and eight weeks post-delivery. I can report that there were no subsequent metabolic decompensations since the one described here. Metabolic stability has been achieved for the time being for this patient
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