Mark Sweeney

Autonomous extraction of optimal flame fronts in OH planar laser-induced fluorescence images

The location of a flame front is often taken as the point of maximum OH gradient. Planar laser-induced fluorescence of OH can be used to obtain the flame front by extracting the points of maximum gradient. This operation is typically performed using an edge detection algorithm. The choice of operating parameters a priori poses significant problems of robustness when handling images with a range of signal-to-noise ratios. A statistical method of parameter selection originating in the image processing literature is detailed, and its merit for this application is demonstrated. A reduced search space method is proposed to decrease computational cost and render the technique viable for large data sets. This gives nearly identical output to the full method. These methods demonstrate substantial decreases in data rejection compared to the use of a priori parameters. These methods are viable for any application where maximum gradient contours must be accurately extracted from images of species or temperature, even at very low signal-to-noise ratios.

The efficacy and safety of cryoprecipitate in the treatment of acquired hypofibrinogenaemia

Acquired hypofibrinogenaemia can result in haemorrhage and significant morbidity and mortality. Cryoprecipitate is well established as the treatment of acquired hypofibrinogenaemia in the UK. Although its use is being superseded by fibrinogen concentrate in a number of other countries (Warmuth et al, 2012), there remains a paucity of clinical data on the relative merits of both products, leading to significant variation in clinical practice between institutions (Tinegate et al, 2012; Wikkelsø et al, 2013;) This retrospective, noncontrolled observational study aimed to determine the safety and efficacy of cryoprecipitate in improving plasma fibrinogen levels, coagulation parameters and clinical status in acute and chronic acquired hypofibrinogenaemia. Clinical and laboratory details of patients who were treated with cryoprecipitate in a large teaching hospital between October 2010 and September 2011 were acquired from the electronic records of the hospital’s transfusion service. For each patient, demographic data were collected, as well as primary cause of hypofibrinogenaemia. Plasma Clauss fibrinogen levels, prothrombin time (PT) and activated partial thromboplastin time (aPTT) were recorded prior to cryoprecipitate administration, and subsequent levels noted at both 24 and 72 h following administration. Medical records were used to confirm the indication for cryoprecipitate administration and any subsequent adverse effects post-administration. All cryoprecipitate was sourced from National Health Service Blood and Transplant with a standard adult dose comprising 2 pools (10 units) of cryoprecipitate with a quoted mean dose of 1575 mg of fibrinogen per pool. During the 12-month study period cryoprecipitate was given on 143 separate occasions. Of these, 89 (62 2%) met our inclusion criteria. Our cohort comprised 50 males and 39 females with a mean age of 51 8 years (Table I). All work was undertaken with approval from the local Research Ethics Committee. Across all groups, the mean fibrinogen level was 1 01 g/l (standard deviation [SD] 0 52) at baseline, and the administration of an average of 2 04 units (SD 0 98) of cryoprecipitate increased the average level of fibrinogen by 0 79 g/l (SD 0 89; P < 0 0001) by 24 h, reaching 1 80 g/l, and then by a further 0 41 g/l (SD 1 23; P = 0 02) between 24 and 72 h, to a final mean value of 2 21 g/l. This increase was significantly greater in the acute group compared to the chronic group both at 24 h (increment of 1 00 vs. 0 46 g/l, P = 0 0013) and 72 h (increment of 1 68 vs. 0 40 g/l, P = 0 0006). The average fibrinogen level before administration of cryoprecipitate was similar in the two disease groups (acute vs. chronic; mean 1 02 g/l [SD 0 60] vs. 0 99 g/l [SD 0 37]; P > 0 05 [not significant]), and the amount of cryoprecipitate administered was comparable in the two cohorts, with 2 15 units (SD 0 97) in the chronic group and 1 98 units (SD 0 98) in the acute group. At 24 h post-cryoprecipitate the mean fibrinogen level was higher in the acute group when compared to the chronic group (2 02 g/l [SD 1 03] vs. 1 45 g/l [SD 0 51]; P = 0 0009). This observation was also true at the 72-h time-point (acute 2 70 g/l [SD 1 25] vs. chronic 1 39 g/l [SD 0 95]; P = 0 0004). Despite cohort differences, the increase in fibrinogen level was statistically significant for both cohorts between baseline and 24 h (acute, P ≤ 0 0001; chronic, P = 0 0001). The fibrinogen level continued to rise significantly between 24 and 72 h in the acute group (P = 0 003) but failed to do so in the chronic group (P = 0 14 [not significant]; Fig. 1). Significantly, there were no acute adverse transfusion reactions reported as a direct result of the cryoprecipitate administration; in particular, no cases of transfusion-associated circulatory overload or transfusion-transmitted infection (TTI) were noted. The current study demonstrates that cryoprecipitate is an effective and safe method of increasing the plasma fibrinogen level in hypofibrinogenaemic patients. It is most effective in the absence of any chronic underlying cause for hypofibrinogenaemia where endogenous production of fibrinogen can resume once the acute insult has ceased. It proved less effective when used in patients with underlying hepatic insufficiency. These findings contribute to the growing debate over the continued use of cryoprecipitate in the UK, which was initially developed for the treatment of haemophilia A and only subsequently found a role in the treatment of hypofibrinogenaemia. Concerns about its usage have focused on the potential risks of TTI and variability in fibrinogen content of individual units, together with issues surrounding controlled thawing, transport to patients and timely administration. These concerns have intensified with the ready availability of plasma-derived pasteurized fibrinogen concentrate, which may theoretically overcome many of the potential disadvantages of cryoprecipitate. Previous data on cryoprecipitate was limited to isolated case reports and a small study comparing its activity to fresh frozen plasma in patients with liver failure, which observed a

Is the continued use of UK plasma sourced cryoprecipitate justified? Response to Makris.

throp, C., Balendran, G. & Besser, M. (2014) The efficacy and safety of cryoprecipitate in the treatment of acquired hypofibrinogenaemia. British Journal of Haematology, 166, 458–461. NCJDRSU (2014) Variant Creutzfeldt-Jakob Disease: Current Data (June 2014). www.cjd.ed.ac. uk/documents/worldfigs.pdf The National Creutzfeldt-Jakob Disease Research & Surveillance Unit.