Study of the incidence of accidental dural punctures (ADP) in relation to the body mass index (BMI) in the Obstetric Anaesthesiology Service of the General University Hospital Gregorio Marañón

INTRODUCTION 
The performance of an epidural technique for labor is an essential part of the obstetric patient's pain management. In our center, this procedure is performed for more than 90% of the patients who attend delivery. Despite being a safe technique, occasionally an accidental dural puncture (ADP) can be produced during the performance of the technique, with an incidence that varies between 0.2 and 4%. It is considered that this complication can have important clinical repercussions in obstetric patients, such as the occurrence of a post-puncture headache (PPHA). This complication is related to the caliber of the needle, the weight of the woman and the age; among other factors. The goal of our study is to determine the relationship between the incidence of ADP and the BMI of the patients.

MATERIAL AND METHODS 
We have designed a descriptive, observational and cross-sectional study where we collected information on 27094 epidurals carried out between June 2010 and March 2017. In all the epidurals performed in the delivery rooms, the informed consent is obtained from the woman before the realization of the technique. Afterwards, a survey is filled in with the following data: age, ASA, weight and height, week of pregnancy and obstetric formula. And later, data related to the anesthetic technique is filled in: epidural or spinal technique, if the loss of ressistant was done with air or physiological saline solution, number of spaces punctured, place of puncture, position of the patient as well as complications are reflected: blood puncture, paresthesias, intravascular or painful injection, complete spinal block, or others. Subsequently we calculated the BMI of the patients, relating it to the incidence of ADP, considering a low BMI below 18.5, normal between 18.5-24.99, overweight 25-29.99, obesity above 30 and morbid obesity above 40.

RESULTS
Between June 2010 and May 2017, a total of 27094 women in labor received epidural analgesia. A total of 147 ADPs have been found, which would condition an incidence of 0.54%. Of these, weight and height data of 99 patients have been collected. With a normal BMI we found 30 PDA (29.7%), with a BMI of overweight there were 42 (41.58%), with obesity 25 (24.75%) and 2 were patients with morbid obesity (1.98%).

DISCUSSION 
Although the epidural for labor is still the analgesic technique of choice and is a safe and effective technique, we must not forget that it is not free of complications. The ADP can produce PPHA that conditions a great discomfort to the patient, in addition to the need of treatment that can range from intravenous or oral analgesia to the realization of a blood patch; besides increasing the length of hospital stay. In other studies, different risk factors have been identified that can condition an increase in the incidence of ADP, such as the experience of the anesthesiologist performing the technique, the weight of the woman as well as the ability to adopt the posture and remain still during the procedure; the characteristics of the needle (Tuohy needle) ... etc . In our case, and in regard to the physical characteristics of the patients, we found that the majority of ADPs occur in those with a BMI above 25, with the highest incidence in the overweight group. As protective measures against ADP, some authors suggest leaving the catheter in the intradural space to favor fibrosis and thus avoid the leakage of cerebrospinal fluid, although in the literature we do not find consensus regarding this measure.

CONCLUSION 
The prevalence of ADP is similar in our hospital to other series. With the data we have collected and analyzed, we can conclude that the achievement of ADP is more frequent in those patients with a BMI greater than 25 (68.31% of cases).

06 / Study of the incidence of accidental dural punctures (ADP) in relation to the body mass index (BMI) in the Obstetric Anaesthesiology Service of the General University Hospital Gregorio Marañón