Ellen de Kort

138 Chapter 8 The incidence of hypotension was over 50% in all groups. The blood pressure decline was mainly dependent on the starting dose that was used, and less influenced by the cumulative propofol dose that was administered to achieve successful endotracheal intubation. To the best of our knowledge, this is the first study to evaluate the effect of different propofol doses on blood pressure. Comparisonwith data from the literature, therefore, is somewhat difficult. In our analysis, propofol-induced hypotension was observed in 63%, 52% and 62% of the patients receiving a propofol starting dose of 1.0 mg/kg, 1.5 mg/kg and 2.0 mg/ kg, respectively. Previous literature shows somewhat controversial effects of propofol on blood pressure in newborns. Smits et al., in their dose-finding study, found an incidence of hypotension of 64% in the entire population irrespective of the starting dose that was administered. 13 Welzing et al. and Simons et al. both reported an incidence of propofol- induced hypotension of 39%. 9,10 In their randomized controlled trial comparing propofol to sufentanil and atracurium, Durrmeyer et al. found hypotension to occur in 13.3% of patients in the propofol group. 12 In contrast to these findings, others reported no hypotension to occur in their study population treated with propofol for endotracheal intubation. 6,11 Part of these controversial results might be found in different definitions used for hypotension in preterm infants. Even in the 21 st century, there is no generally accepted definition. Without any evidence to support it, the most popular criterion to define hypotension is mean blood pressure below gestational age. 15,16 The second most used definition is a MBP below the 10 th or 5 th percentile. 16 There are numerous reference ranges, often based on gestational age, birthweight and postnatal age criteria, with considerable variation among these reference ranges. 15,17 Finally, MBP below 30 mmHg is used to define hypotension, because some studies found loss of cerebral autoregulation below this threshold. 16,18,19 In our study and in the study of Smits et al. the MBP below gestational age criterion was used. Both studies also used this definition for infants beyond the first 72 hours of life and therefore somewhat modified the definition to MPB below postmenstrual age. 13,14 Simons et al. also used the MBP below gestational age criterion but only reported on hypotension of a severity that required treatment. 9 This could explain why they found a lower incidence of hypotension of 39%. Should we have only reported on hypotension that required treatment, our incidence of hypotension would have been 32%. Welzing et al. used a much more liberal definition of MBP less than 25 mmHg in a study population with a gestational age of 29 to 32 weeks and 28 to 34 weeks respectively. 10 Should they have used the MBP below gestational age criterion, the incidence of hypotension would have been much higher.