Women with chronic kidney disease (CKD) may present in pregnancy. Some women, including those with no known pre-existing renal dysfunction, may develop acute kidney injury (AKI) in pregnancy or the puerperium, perhaps as a complication of a pregnancy- related problem. Either way, it has implications for the obstetric anaesthetist.
Although pregnancy was uncommon in patients with CKD in the past, improvements in the care of patients requiring renal replacement mean that women on dialysis programmes or having received renal transplants are increasingly likely to present to the maternity department. Conversely, pregnancy-related AKI related to an obstetric complication should be becoming less common as care of the sick mother (in both the maternity suite and the intensive care unit) improves, although there are few data relating to this.
It should be remembered that the normal physiological changes of pregnancy result in an increased glomerular filtration rate and a lowering of the ‘normal’ blood indices of renal function. Thus, the usual blood urea concentration in pregnancy is 3.0-4.0 mmol/l and the creatinine concentration 55-65 mmol/l. In contrast to non-pregnant subjects, a moderate increase in blood urea concentration in a pregnant woman may thus represent significant renal impairment.
Problems and special considerations
Pre-existing disease
In terms of general anaesthetic management, the problems of pre-existing renal disease are the same as in the non-pregnant population. These include the underlying cause of renal impairment, systemic manifestations of renal failure (in particular hypertension and ischaemic heart disease, thrombocytopenia and anaemia), the patient’s medication, altered handling of drugs and fluid management, including the nature and timing of dialysis.
Obstetric management maybe influenced by the above factors and any history of previous abdominal surgery, including the presence of a transplanted kidney. There is an increased risk of pre-eclampsia in mothers with renal impairment. The fetus may also be at risk, either from the underlying disease that caused renal impairment or from the above complications.
Pregnancy-related acute kidney injury
Typically, pregnancy-related AKI is especially associated with pre-eclampsia, HELLP syndrome, septic abortion and massive haemorrhage (traditionally caused by placental abruption, although any cause of hypovolaemia maybe followed by AKI). Other important causes include pyelonephritis, drug reactions (especially non-steroidal anti-inflammatory drugs, NSAIDs), acute fatty liver, incompatible blood transfusion and thrombotic microangiopathies. In most cases, AKI is caused by acute tubular necrosis, although cortical necrosis has been seen after abruption and pre-eclampsia. Problems are those of AKI generally, especially related to fluid balance and the apparently increased susceptibility of pregnant women to developing pulmonary oedema.
Management options
Parturients with pre-existing kidney disease should have their renal function closely monitored and blood pressure optimised during pregnancy. Severe anaemia may need to be corrected. Discussion with renal physicians and obstetricians is required regarding the timing of dialysis and method of delivery. Any arteriovenous shunt should be noted and steps taken to protect it during labour and/or delivery. Standard anaesthetic and analgesic techniques are suitable, given the above considerations, although regional anaesthesia may not be appropriate in some patients with coagulopathy or in those who have had recent haemodialysis. Drugs excreted renally should be used with caution, and those known to impair renal blood flow or function (especially NSAIDs) should be avoided. The management of women with previous renal transplant is discussed in Chapter 154, Transplantation).
Management of AKI in pregnancy is along standard lines. Preventive management aims at the identification of risk factors and early intervention, for example correction of hypovolaemia. Careful fluid balance is especially important, given the propensity of obstetric patients to pulmonary oedema, and invasive haemodynamic monitoring may be required in some women. Serum electrolytes must be monitored, particularly in women receiving magnesium therapy. Renal replacement therapy may occasionally be needed. Most mothers regain normal renal function, depending on the underlying cause, although a degree of renal impairment may persist postpartum.
Key points
• Mothers with chronic kidney disease require careful monitoring and an interdisciplinary approach.
• Obstetric anaesthetic management uses standard techniques, taking into account the underlying cause and systemic effects of renal dysfunction, use of drugs and problems relating to fluid management.
• Acute kidney injury may develop during or after obstetric catastrophes; management is along standard lines, and recovery of function is usual.
Further reading
Acharya A. Management of acute kidney injury in pregnancy for the obstetrician. Obstet Gynecol Clin North Am 2016; 43: 747-65.
Chinnappa V, Ankichetty S, Angle P, Halpern SH. Chronic kidney disease in pregnancy. Int J Obstet Anesth 2013; 22: 223-30.
Galvagno SM, Camann W. Sepsis and acute renal failure in pregnancy. Anesth Analg 2009; 108: 572-5. Liu Y, Ma X, Zheng J, Liu X, Yan T. Pregnancy outcomes in patients with acute kidney injury during pregnancy: a systematic review and meta-analysis. BMC Pregnancy Childbirth 2017; 17: 235.
Webster P, Lightstone L, McKay DB, Josephson MA. Pregnancy in chronic kidney disease and kidney transplantation. Kidney Int 2017; 91: 1047-56.