ABSTRACT
PURPOSE: To determine the causes of failure of epidural analgesia during labour and delivery. METHODS: During six months, pregnant patients receiving epidural analgesia and delivering vaginally were studied prospectively. Bupivacaine 0.125% was used for the initial bolus dose and subsequent continuous infusion. Top-ups of the same solution were used for inadequate pain relief assessed using a visual analogue pain score (VAPS) and/or by clinical examination. Inadequate pain relief was defined as the need for > or = 2 top-ups in addition to epidural infusion and failure during delivery as VAPS > or = 30 mm during the expulsion phase. RESULTS: 1009 patients delivered during this period, 596 had epidural analgesia for vaginal delivery of a live infant and data were complete in 456. Inadequate pain relief during labour and during delivery were found in 5.3% and 19.7% of patients. Risk factors of inadequate pain relief included: inadequate analgesic efficacy of the first dose (Odds ratio: 3.5, P = 0.001) and posterior presentation (Odds ratio: 5.6, P = 0.001). Radicular pain during epidural placement was associated with failure during labour (Odds ratio: 3.9, P = 0.05). Duration of epidural analgesia > six hours (Odds ratio: 9.1, P = 0.001) was a risk factor for insufficient pain relief during labour whereas duration of epidural analgesia < one hour was associated with pain during delivery (Odds ratio: 18.3, P = 0.001). CONCLUSION: Several obstetrical and epidural-related factors increase the risk of inadequate epidural analgesia. For some, simple changes of practice pattern may lead to improved pain relief.
Subject(s)
Analgesia, Epidural , Analgesia, Obstetrical , Adult , Body Weight , Female , Humans , Multivariate Analysis , Pregnancy , Prospective Studies , Risk Factors , Treatment FailureABSTRACT
The problem of successive transverse plane reconstruction in single photon emission computerized tomography (SPECT) is modeled in its more general form, which implies the definition of emission tomographic operators (ETO's) for which an analytical solution can be derived. The properties of the attenuated tomographic operator (ATO) are described and discussed, including the attenuation which is distributed on the reconstruction domain. For this particular operator, a regularizing method (RIM) is proposed, for which it is demonstrated and tested with simulation studies that a filtered, accurate solution can be extracted for the tomographic images as obtained using a single photon emission tomograph based on a rotating gamma camera in clinical use.
ABSTRACT
The problem of transverse plane reconstruction from an ensemble of projections is considered in its general formulation and an analytically exact solution to the attenuated tomographic operator is proposed. Such a technique, called the regularizing iterative method (RIM), allows the introduction of a priori knowledge on the size and shape of the activity distribution and in principle on the exact attenuation distribution. The relaxation factor used is so named because it provides noise filtering for a small number of iterations. The effectiveness of RIM was studied in the single photon emission computed tomography (SPECT) problem with the aim of correcting for attenuation before quantitative study. Its application involves the use of a rotating scintillation camera connected to a mini-computer system. Various mathematical and physical phantoms were studied, and a satisfactory attenuation correction was always obtained in the final image with an improvement in the contrast and signal-to-noise ratio. Preliminary clinical studies on liver transverse sections seems to indicate an improvement in deep lesion detectability, compared with images obtained by the filtered (Ramp) back projection technique.
