Prevalence of immediate vasovagal reaction in blood donors visiting two blood banks of Karachi.

Vasovagal reaction (VVR) is a very common adverse event related to blood donation. No study has been conducted in Pakistan to estimate the prevalence of VVR in blood donors. This study was conducted to estimate the prevalence of immediate VVR in blood donors of Karachi, Pakistan. The study was conducted in two blood banks of Karachi. Data regarding the development of immediate VVR were documented. The effect of blood donation on vital parameters like pulse rate, blood pressure (BP), temperature and respiratory rate was also observed. Six hundred and seventy-four blood donors were recruited. All the donors who consented were males. Weakness and dizziness were two most common symptoms which were reported by 91 (13.5%) and 73 (10.8%) of the participants, respectively. Out of 91 donors in whom signs and symptoms of immediate VVR were observed, a significant drop in systolic BP (13.5 +/- 2.5 mmHg) and decrease in pulse rate (13.3 +/- 3.6) were concurrently noted in 55 donors (8.2% of all the participants). There was lack of association of age, body mass index (BMI), estimated blood volume, ethnicity, educational status, profession and first time donation status with the frequency of VVR. Only marital status was found to be significantly associated with higher frequency of immediate VVR, where married donors were having higher odds as compared to singles. The prevalence of VVR in the blood donors at two blood banks of Karachi is at least 8.2%. Furthermore, married men are at more risk of experiencing VVR in our population.