Incidence of PDPH: Post dural puncture headache (PDPH) is the most reported complication that can occur following spinal anaesthesia. Several studies carried out across the globe have shown the incidence of PDPH to range from 1% to 75% (13) and 3% to 60% (10). From this study, we found an unexpectedly high incidence of PDPH among women undergoing caesarean section in Mulago National Referral Hospital for the period from July 2015 to February 2016. Despite this incidence being in accordance with the ranges reported above, it is the highest incidence reported in published studies in which relatively small needle gauges like 25 gauge Quincke needles were used(12, 14-18). This was twice that reported in a similar study done in Nairobi (24.4%) (9). Studies have shown that using small gauge needles like the one used in this study is protective however we still found out a higher incidence of PDPH which is 1.5 times higher than reported by a study done in Kasr El aini teaching hospital in Cairo, Egypt using a bigger gauge needle (gauge 22) were the overall incidence was reported 32.58%(7).
These differences could be explained by the fact that in our study, we only recruited women due for emergency caesarean section who required immediate intervention without time for pre loading fluids or correcting fluid deficits. (19)
If a post dural puncture headache is to occur, it has been reported to occur in 90% of patients within the first 72 hours (13). True to this finding, most patients developed the PDPH within that time duration with a cumulative incidence of 31.8% however we had 23.7% of patients developing PDPH on the seventh day. This suggests presence factors out of hospital possibly contributing to the high incidence seen in our setting. Furthermore, when compared to studies that followed patients for only three days, (17) the cumulative incidence by day three in our study is still higher(8.7% versus 31.8%). The difference in sample size could still account for this finding.
Factors associated with post dural puncture headache in parturients in MNRH.
Turnbull and Shepherd in 2003, named a number of factors that were associated with PDPH. Among these were needle size and design, operator skill and level of training, number of attempts, body posture, time to ambulation and fluids received. From studies assessing factors directly associated with PDPH, we considered factors that may contribute to PDPH in our setting taking into account the patient burden and hospital limitations. (7, 12, 13, 16, 20).
The factors that were significantly associated with PDPH from this study were previous exposure to spinal anaesthesia and blood loss greater than 0.5 liters.
Women who lost more than 0.5litres of blood during surgery were more likely to have PDPH compared to those who lost comparably smaller amounts of blood. This is novel as there is no published literature comparing the volume of blood lost intra operatively and development of post dural puncture headache.
Patients with previous exposure to spinal anaesthesia developed PDPH as compared to of women without previous exposure (53% vs. 46.8% respectively), P value=0.04. This was consistent with findings from studies describing factors associated with PDPH (7-9, 20-23). The exact mechanism by which this happens is not known.