The Effect of Preoperative Cannabis Use on Postoperative Pain Following Gynaecologic Oncology Surgery.

OBJECTIVE: To determine whether cannabis users have different pain scores after gynaecologic oncology surgery than non-cannabis users. METHODS: A retrospective chart review was completed for 654 patients who underwent gynaecologic oncology surgery during a 2-year period. The primary outcome was postoperative pain at 12 and 36 hours after surgery using an 11-point pain scale. Secondary outcomes included opioid consumption, length of hospital stay, opioid side effects, and sleep disturbance. RESULTS: Of all patients included in this study, 64 used cannabis and 590 did not. Propensity score matching and list-wise deletion identified 57 matched pairs. Pain scores were significantly higher at 12 hours (P < 0.001) and 36 hours (P =0.002) after surgery in cannabis users (median pain scores 6 [IQR 5-7]) and 5 [IQR 4-7], respectively) than non-users (median pain scores 4 [IQR 3-6] and 4 ([IQR 2-5], respectively). Median opioid consumption was significantly higher at 12 hours (P = 0.039) and 36 hours (P = 0.044) after surgery in cannabis users (oral morphine equivalent [OME] 20 [IQR 10-40] mg and OME 40 [IQR 10-100] mg, respectively) than non-users (OME 10 [IQR 5-20] mg and OME 30 mg [IQR 7.5-50] mg, respectively]. Sleep disturbance was significantly higher in cannabis users (odds ratio 3.31; P = 0.009). CONCLUSIONS: After gynaecologic oncology surgery, patients who used cannabis preoperatively had higher postoperative pain scores, higher opioid use, and more sleep disturbance than non-users. This suggests that preoperative cannabis use is a risk factor for postoperative pain.

A parametric evaluation of shear wave speeds estimated with time-of-flight calculations in viscoelastic media.

Shear wave elasticity imaging (SWEI) uses an acoustic radiation force to generate shear waves, and then soft tissue mechanical properties are obtained by analyzing the shear wave data. In SWEI, the shear wave speed is often estimated with time-of-flight (TOF) calculations. To characterize the errors produced by TOF calculations, three-dimensional (3D) simulated shear waves are described by time-domain Green's functions for a Kelvin-Voigt model evaluated for multiple combinations of the shear elasticity and the shear viscosity. Estimated shear wave speeds are obtained from cross correlations and time-to-peak (TTP) calculations applied to shear wave particle velocities and shear wave particle displacements. The results obtained from these 3D shear wave simulations indicate that TTP calculations applied to shear wave particle displacements yield effective estimates of the shear wave speed if noise is absent, but cross correlations applied to shear wave particle displacements are more robust when the effects of noise and shear viscosity are included. The results also show that shear wave speeds estimated with TTP methods and cross correlations using shear wave particle velocities are more sensitive to increases in shear viscosity and noise, which suggests that superior estimates of the shear wave speed are obtained from noiseless or noisy shear wave particle displacements.

Exact and approximate analytical time-domain Green's functions for space-fractional wave equations.

The Chen-Holm and Treeby-Cox wave equations are space-fractional partial differential equations that describe power law attenuation of the form α(ω)≈α0|ω|y. Both of these space-fractional wave equations are causal, but the phase velocities differ, which impacts the shapes of the time-domain Green's functions. Exact and approximate closed-form time-domain Green's functions are derived for these space-fractional wave equations, and the resulting expressions contain symmetric and maximally skewed stable probability distribution functions. Numerical results are evaluated with ultrasound parameters for breast and liver at different times as a function of space and at different distances as a function of time, where the reference calculations are computed with the Pantis method. The results show that the exact and approximate time-domain Green's functions contain both outbound and inbound propagating terms and that the inbound component is negligible a short distance from the origin. Exact and approximate analytical time-domain Green's functions are also evaluated for the Chen-Holm wave equation with power law exponent y = 1. These comparisons demonstrate that single term analytical expressions containing stable probability densities provide excellent approximations to the time-domain Green's functions for the Chen-Holm and Treeby-Cox wave equations.

The utility of universal urinary drug screening in chronic pain management.

BACKGROUND: A recent systematic review found few studies that assessed the value of urinary drug screening (UDS) in the management of chronic pain. The Pain Management Unit in Halifax, Nova Scotia, has recently implemented tandem mass spectrometry (TMS) UDS for all new patients. AIMS: To study the prevalence of unexpected TMS UDS results at a hospital-based chronic pain center, to assess which drugs are most likely to contribute to an unexpected result and to assess the clinical utilization of unexpected results by pain physicians. METHODS: From June 2014 to June 2016, a total of 664 patients with chronic non-cancer pain (CNCP) were seen for initial consult. Charts were reviewed and used to create a database containing sex, age, UDS result, physician, and medication/illicit drug history. For all unexpected UDS results, an interview was conducted with the treating physician to determine its clinical implications. RESULTS: For the general pain specialists, the overall percentage of patients with an unexpected UDS result was 16.67%. Excluding codeine, at most 4.47% of patients tested unexpectedly positive for a strong opioid. Although eight out of nine physicians found UDS helpful in general, only 29.58% of unexpected results were helpful in the management of their patients and directly influenced their care. CONCLUSIONS: The prevalence of an unexpected UDS result in patients with CNCP is significant. Most physicians agree that UDS is helpful but in only a limited number of cases did the unexpected result provide helpful information that significantly influenced patient care.

Contexte: Une revue systématique récente a démontré que peu d'études évaluaient la valeur du dépistage urinaire de drogue dans la prise en charge de la douleur chronique. L'Unité de prise en charge de la douleur d'Halifax, en Nouvelle-Écosse, a récement instauré le dépistage urinaire de drogue par spectrométrie de masse en tandem pour tous ses nouveaux patients.But: Éudier la prévalence de résultats inattendus lors du dépistage urinaire de drogue par spectométrie de masse en tandem dans un centre de la douleur chronique en milieu hospitalier, afin d'évaluer quelle drogues sont les plus susceptibles de donner lieu à un résultat inattendu et à la fois évaluer l'utilisation clinique des résultats inattendus par les médecins spécialisés dans le traitement de la douleur.Méthodes: De juin 2014 à juin 2016, 664 patients souffrant de douleur chronique non cancéreuse ont été vus pour une consultation initiale. Leurs dossiers ont été étudiés et utilisés pour créer une base de données contenant leur sexe, leur âge, le résultat obtenu lors du dépistage urinaire de drogue, leur médecin traitant et leurs antécédents en matière de médication ou de drogues illicites. Pour tous les résultats de dépistage urinaire de drogue inattendus, une entrevue a eu lieu avec le médecin traitant afin d'en déterminer les implications cliniques.Résultats: Pour les spécialistes de la douleur générale, le pourcentage global de patients ayant obtenu un résultat inattendu lors du dépistage urinaire de drogue était de 16,67 %. À l'exclusion de la codéine, tout au plus 4,47% des patients ont obtenu un résultat positif inattendu pour un opioïde puissant. Bien que huit médecins sur neuf aient trouvé le dépistage urinaire de drogue utile en général, seulement 29,58% des résultats inattendus ont été utiles dans la prise en charge de leurs patients et ont influencé directements les soins prodigués.Conclusions: La prévalence d'un résultat inattendu lors du dépistage urinaire de drogue chez les patients souffrant de douleur chronique non cancéreuse est élevée. La plupart des médecins sont d'accord pour dire que le dépistage urinaire de drogue est utile, mais que le résultat inattendu a fourni de l'information utile ayant influencé les soins aux patients de manière significative seulement dans un nombre limité de cas.