Hyponatraemia and hiccups

Hiccups are observed in many patients with hypohatraemia. We performed a case-control study to evaluate their association in a referral teaching hospital in South India.

Fifty consecutive patients who developed hiccups during an 18-month period were studied. They were categorized according to age group and diagnosis and controls matched for age and sex were selected from patients admitted on the same day in the medical wards. Hiccups were graded on a four-point severity scale at recruitment and every day till day 7 or till hiccups subsided.

The step-wise logistic regression analysis done to establish independent association showed that for every 10 mEq/L reduction in serum sodium, patients were 17 times (p = 0.001; confidence interval: 4-87) at risk of developing hiccups. The only other significant determinant of the symptom was the diagnostic category of renal failure (odds ratio = 128; confidence interval: 1-1420). The number of patients who had hyponatraemia with varying severity of hiccups showed a dose-response relationship. The crude odds ratios were 7, 58 and 320 for mild, moderate and severe hiccups.

There is a strong and independent association between hyponatraemia and hiccups in hospitalized patients. A causative association is suggested by the dose-response relationship demonstrated in the study. In many hospitals in developing countries where measurement of serum sodium is difficult and unreliable, it is important to be aware of this association since it can be easily corrected.