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This paper develops the approach of using continuous second order models of spatial variation, as described by Matern (1970), for the purposes of comparing the efficiencies of alternative experimental designs and analyses for crop experiments. The development is in three stages. First, a form of model is derived which is capable of describing the most important features of variation of crop yield in the field. In the second stage, techniques for fitting the model to uniformity trial data are developed in such a way that all the important parameters of the model can be estimated and tested. Finally procedures are outlined for evaluating the expected residual mean square resulting from a given design and analysis on a field whose properties obey a given realization of the model. These procedures include classical design and analysis and neighbouring plot methods.

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Background: The addition of intrathecal fentanyl to spinal anesthesia for cesarean delivery has been shown to be beneficial, but its rate of utilization in the community setting is unknown. The primary aim of our study was to determine the rate of intrathecal fentanyl use for cesarean deliveries with spinal anesthesia in a community hospital, and our secondary aim was to determine its effect on anesthetic outcomes. Methods: Patients who underwent cesarean delivery from June 1, 2017 to November 30, 2019 with spinal anesthesia as the initial anesthetic technique were included. Results: Seven hundred sixty-one cesarean deliveries met inclusion criteria, and 161 (21.2%) patients received intrathecal fentanyl in their spinal anesthetic for cesarean delivery. A multivariate model that controlled for patient weight and time from spinal placement to procedure end showed that patients who received intrathecal fentanyl were less likely to have conversion to general anesthesia or administration of systemic anesthetic adjuncts compared to patients who did not receive intrathecal fentanyl (odds ratio 2.889, 95% CI 1.552-5.903; P=0.0017). Conclusion: Only 1 in 5 patients received intrathecal fentanyl for cesarean deliveries performed under spinal anesthesia in a community hospital despite known benefits. Patients who did not receive intrathecal fentanyl had increased odds of conversion to general anesthesia or administration of systemic anesthetic adjunct administration, a finding consistent with previous studies. The addition of intrathecal fentanyl to spinal anesthesia for cesarean delivery should be strongly considered in the community setting.

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