| disease | Neonatal Hypocalcemia |
| alias | Hypocalcemia, Hypocalcemia, Hypocalcemia |
The normal concentration of total calcium in the blood is 2.5 mmol/L (10 mg/dl). Hypocalcemia is defined when the total blood calcium falls below 1.75–2 mmol/L (7.0–8.0 mg/dl) or when the ionized calcium is below 0.9 mmol/L (3.5 mg/dl). It is one of the important causes of neonatal seizures.
bubble_chart Etiology
The balance of calcium primarily relies on the regulation of the parathyroid glands and calcitonin. If this regulatory function is impaired, or if fetal calcium storage is insufficient or postnatal phosphorus intake is excessive, it can lead to hypocalcemia. The specific disease causes are as follows:
1. Early hypocalcemia occurs within the first 2 days after birth, often due to temporary suppression of parathyroid function. During the late stage of pregnancy [third trimester], the increased transfer of calcium from the maternal blood to the fetus via the placenta Dongshu suppresses parathyroid function. Low birth weight infants, those with asphyxia, and newborns suffering from respiratory distress syndrome have poorer parathyroid function compared to full-term healthy newborns, along with lower calcium reserves, resulting in a higher incidence of the condition. Some suggest that elevated calcitonin levels in the blood during the first few days after birth may also contribute to hypocalcemia. In early-onset cases, blood calcium levels often fall below 1.75 mmol/L.
2. Advanced-stage hypocalcemia occurs after the third day of birth, peaking at the end of the first week. It is more common in formula-fed newborns due to excessive phosphorus intake, which lowers blood calcium levels. Blood calcium values typically drop below 2.00 mmol/L.
3. A small number of cases are caused by congenital parathyroid insufficiency, which may manifest early or late, with symptoms persisting for over 3 weeks. However, most infants gradually develop normal parathyroid function as they grow, making this condition temporary.4. Rarely, pregnant women with hyperparathyroidism or adenomas may exhibit no symptoms themselves but have elevated blood calcium levels, severely suppressing fetal parathyroid function. This leads to persistent hypocalcemia in the infant after birth. In some cases, the newborn’s condition becomes a clue for diagnosing the mother’s thyroid tumor.
bubble_chart Clinical Manifestations
Symptoms vary in severity, primarily manifesting as restlessness, startling, tremors, and convulsions, occasionally accompanied by laryngospasm and apnea. During the onset, infants generally appear well but may exhibit slightly increased muscle tone and enhanced tendon reflexes. The positive facial nerve tapping test (Chvostek's sign) in normal newborns lacks diagnostic significance.
1. It is more common in infants whose mothers may have had diabetes or pregnancy-induced hypertension during pregnancy, as well as in premature infants and those with a history of asphyxia.
2. Symptoms usually appear within hours to 2 days after birth, including restlessness, startling, limb tremors, laryngospasm, and convulsions. Between episodes, the infant generally appears healthy.
3. Blood calcium is below 3.5 mmol/L (7 mg/dl) or free calcium is below 1.75 mmol/L (3.5 mg/dl).
bubble_chart Treatment Measures
Calcium therapy is highly effective. For those affected, use 10% calcium gluconate at a dose of 1.0–2.0 ml/kg per administration, diluted with an equal volume of 5% glucose solution, and administer by slow intravenous injection at a rate not exceeding 1 ml per minute. Repeat the dose once after 6–8 hours if necessary. During treatment, monitor the heart rate closely; if it falls below 80 beats per minute, discontinue the injection. Take care to prevent medication leakage outside the blood vessels to avoid tissue necrosis. After convulsions cease, switch to oral calcium at 0.25 g per dose, 2–3 times daily, to maintain blood calcium within the normal range. For infants with advanced-stage hypocalcemia, breastfeeding or formula feeding is recommended.
Hypocalcemic convulsions may be accompanied by hypomagnesemia. In such cases, after administering calcium gluconate, add an intravenous drip of 2.5% magnesium sulfate at 2–4 ml per dose, once daily. Otherwise, convulsions may persist. Typically, convulsions cease after 1–2 days of injection, after which switch to oral 10% magnesium sulfate at a concentration not too high, 1–2 ml/kg per dose, 2–3 times daily for 5–7 days. Excessive blood magnesium can suppress respiration; in such cases, administer 10% calcium gluconate intravenously at 1–2 ml/kg per dose. Premature infants should not receive intramuscular magnesium sulfate to avoid local necrosis.
1. Hypoglycemia Both hypoglycemia and hypocalcemia can occur in the early neonatal period, but hypoglycemia is more common in low birth weight infants, while hypocalcemia can occur in any type of newborn.
2. Hypomagnesemia The average blood magnesium level in newborns is 0.82 mmol/L (2.0 mg/dl). When blood magnesium falls below 0.62 mmol/L (1.5 mg/dl), it is termed hypomagnesemia. Its symptoms resemble those of hypocalcemia, making the two conditions difficult to distinguish, and they may coexist. Blood generation and transformation testing aids in diagnosis.
4. DiGeorge syndrome This syndrome manifests as permanent parathyroid insufficiency, accompanied by thymic aplasia, immunodeficiency, and micrognathia, sometimes with abnormalities of the main stirred pulse arch. Symptoms include recurrent hypocalcemic convulsions. The absence of a thymic shadow on chest X-rays aids in differentiation. {|103|}
