Temperature mapping in an air ambulance helicopter: Implications for the delivery of pre-hospital transfusion.

BACKGROUND: Pre-hospital blood products, including freeze-dried plasma, are increasingly carried on air ambulance helicopters. The purpose of this study was to map the temperatures within a civilian air ambulance and consider the implications for pre-hospital transfusion. MATERIALS AND METHODS: We conducted a single-site prospective observational study in the United Kingdom. Tinytag temperature data-loggers (Gemini, UK) were secured on to three locations throughout an air ambulance, and one was placed inside an insulated drug-pouch. Temperatures were monitored at 5-min intervals. Data were downloaded monthly and processed using R and MKT software to collate maximum, minimum, and day/night mean kinetic temperatures (MKTs). Blood was transported in Credo ProMed 4 containers (Peli Products, S.L.U) and monitored with QTA data-loggers (Tridentify, Sweden). RESULTS: A total of 344,844 temperature recordings were made on 302 days during a 12-month period from January 2019. The external ambient temperatures varied seasonally from -7.1°C to 31.2°C, whereas internal temperatures ranged from -0.3°C to 60.6°C. The warmest area was alongside the left front-crew position (range 1.9-60.6°C, MKT 24.8°C). The lowest daytime MKT (16.9°C) and range (1.7°C-36.4°C) were recorded next to the patient stretcher. Temperatures ranged from 4.2°C to 40.1°C inside the insulated drugs-pouch, exceeding 25°C on 47 days (15%) and falling below 15°C on 192 days (63%) In contrast, thermally packed blood maintained a range of 2-6°C. CONCLUSION: The temperatures within an air ambulance varied throughout the cabin and often exceeded the external ambient temperature. Appropriately selected thermal protection and monitoring is required for the successful delivery of pre-hospital transfusion, even in a temperate climate.

A rapid and sensitive method to detect siRNA-mediated mRNA cleavage in vivo using 5' RACE and a molecular beacon probe.

Specific detection of mRNA cleavage by 5'RACE is the only method to confirm the knockdown of mRNA by RNA interference, but is rarely reported for in vivo studies. We have combined 5'-RNA-linker-mediated RACE (5'-RLM-RACE) with real-time PCR using a molecular beacon to develop a rapid and specific method termed MBRACE, which we have used to detect small-interfering RNA (siRNA)-induced cleavage of ApoB, RRM1 and YBX1 transcripts in vitro, and ApoB in vivo. When RNA from siRNA-transfected cells was used for 5'-RLM-RACE and a cleavage site-specific molecular beacon probe was included in subsequent real-time PCR analysis, the specific mRNA cleavage product was detected. Detection of siRNA-mediated cleavage was also observed when RNA from mouse liver following administration of ApoB-specific siRNA was analysed, even in cases where ApoB knockdown measured by real-time PCR was <10%. With its sensitivity and specificity, this variation on the 5'RACE method should prove a useful tool to detect mRNA cleavage and corroborate knockdown studies following siRNA use in vivo.

Resuscitation with blood products in patients with trauma-related haemorrhagic shock receiving prehospital care (RePHILL): a multicentre, open-label, randomised, controlled, phase 3 trial.

BACKGROUND: Time to treatment matters in traumatic haemorrhage but the optimal prehospital use of blood in major trauma remains uncertain. We investigated whether use of packed red blood cells (PRBC) and lyophilised plasma (LyoPlas) was superior to use of 0·9% sodium chloride for improving tissue perfusion and reducing mortality in trauma-related haemorrhagic shock. METHODS: Resuscitation with pre-hospital blood products (RePHILL) is a multicentre, allocation concealed, open-label, parallel group, randomised, controlled, phase 3 trial done in four civilian prehospital critical care services in the UK. Adults (age ≥16 years) with trauma-related haemorrhagic shock and hypotension (defined as systolic blood pressure <90 mm Hg or absence of palpable radial pulse) were assessed for eligibility by prehospital critial care teams. Eligible participants were randomly assigned to receive either up to two units each of PRBC and LyoPlas or up to 1 L of 0·9% sodium chloride administered through the intravenous or intraosseous route. Sealed treatment packs which were identical in external appearance, containing PRBC-LyoPlas or 0·9% sodium chloride were prepared by blood banks and issued to participating sites according to a randomisation schedule prepared by the co-ordinating centre (1:1 ratio, stratified by site). The primary outcome was a composite of episode mortality or impaired lactate clearance, or both, measured in the intention-to-treat population. This study is completed and registered with ISRCTN.com, ISRCTN62326938. FINDINGS: From Nov 29, 2016 to Jan 2, 2021, prehospital critical care teams randomly assigned 432 participants to PRBC-LyoPlas (n=209) or to 0·9% sodium chloride (n=223). Trial recruitment was stopped before it achieved the intended sample size of 490 participants due to disruption caused by the COVID-19 pandemic. The median follow-up was 9 days (IQR 1 to 34) for participants in the PRBC-LyoPlas group and 7 days (0 to 31) for people in the 0·9% sodium chloride group. Participants were mostly white (62%) and male (82%), had a median age of 38 years (IQR 26 to 58), and were mostly involved in a road traffic collision (62%) with severe injuries (median injury severity score 36, IQR 25 to 50). Before randomisation, participants had received on average 430 mL crystalloid fluids and tranexamic acid (90%). The composite primary outcome occurred in 128 (64%) of 199 participants randomly assigned to PRBC-LyoPlas and 136 (65%) of 210 randomly assigned to 0·9% sodium chloride (adjusted risk difference -0·025% [95% CI -9·0 to 9·0], p=0·996). The rates of transfusion-related complications in the first 24 h after ED arrival were similar across treatment groups (PRBC-LyoPlas 11 [7%] of 148 compared with 0·9% sodium chloride nine [7%] of 137, adjusted relative risk 1·05 [95% CI 0·46-2·42]). Serious adverse events included acute respiratory distress syndrome in nine (6%) of 142 patients in the PRBC-LyoPlas group and three (2%) of 130 in 0·9% sodium chloride group, and two other unexpected serious adverse events, one in the PRBC-LyoPlas (cerebral infarct) and one in the 0·9% sodium chloride group (abnormal liver function test). There were no treatment-related deaths. INTERPRETATION: The trial did not show that prehospital PRBC-LyoPlas resuscitation was superior to 0·9% sodium chloride for adult patients with trauma related haemorrhagic shock. Further research is required to identify the characteristics of patients who might benefit from prehospital transfusion and to identify the optimal outcomes for transfusion trials in major trauma. The decision to commit to routine prehospital transfusion will require careful consideration by all stakeholders. FUNDING: National Institute for Health Research Efficacy and Mechanism Evaluation.

The impact of change in albumin assay on reference intervals, prevalence of 'hypoalbuminaemia' and albumin prescriptions.

BACKGROUND: We studied the impact on reference intervals, classification of patients with hypoalbuminaemia and albumin infusion prescriptions on changing from a bromocresol green (BCG) to a bromocresol purple (BCP) serum albumin assay. METHODS: Passing-Bablok regression analysis and Bland-Altman plot were used to compare Abbott BCP and Roche BCG methods. Linear regression analysis was used to compare in-house and an external laboratory Abbott BCP serum albumin results. Reference intervals for Abbott BCP serum albumin were derived in two different laboratories using pathology data from adult patients in primary care. Prescriptions for 20% albumin infusions were compared one year before and one year after changing the albumin method. RESULTS: Abbott BCP assay had a negative bias of approximately 6 g/L compared with Roche BCG method.There was good agreement (y = 1.04 x - 1.03; R(2 )= 0.9933) between in-house and external laboratory Abbott BCP results. Reference intervals for the serum albumin Abbott BCP assay were 31-45 g/L, different to those recommended by Pathology Harmony and the manufacturers (35-50 g/L). Following the change in method there was a large increase in the number of patients classified as hypoalbuminaemic using Pathology Harmony references intervals (32%) but not when retrospectively compared to locally derived reference intervals (16%) compared with the previous year (12%). The method change was associated with a 44.6% increase in albumin prescriptions. This equated to an annual increase in expenditure of £35,234. CONCLUSIONS: We suggest that serum albumin reference intervals be method specific to prevent misclassification of albumin status in patients. Change in albumin methodology may have significant impact on hospital resources.

The importance of RT-qPCR primer design for the detection of siRNA-mediated mRNA silencing.

BACKGROUND: The use of RNAi to analyse gene function in vitro is now widely applied in biological research. However, several difficulties are associated with its use in vivo, mainly relating to inefficient delivery and non-specific effects of short RNA duplexes in animal models. The latter can lead to false positive results when real-time RT-qPCR alone is used to measure target mRNA knockdown. FINDINGS: We observed that detection of an apparent siRNA-mediated knockdown in vivo was dependent on the primers used for real-time RT-qPCR measurement of the target mRNA. Two siRNAs specific for RRM1 with equivalent activity in vitro were administered to A549 xenografts via intratumoural injection. In each case, apparent knockdown of RRM1 mRNA was observed only when the primer pair used in RT-qPCR flanked the siRNA cleavage site. This false-positive result was found to result from co-purified siRNA interfering with both reverse transcription and qPCR. CONCLUSIONS: Our data suggest that using primers flanking the siRNA-mediated cleavage site in RT-qPCR-based measurements of mRNA knockdown in vivo can lead to false positive results. This is particularly relevant where high concentrations of siRNA are introduced, particularly via intratumoural injection, as the siRNA may be co-purified with the RNA and interfere with downstream enzymatic steps. Based on these results, using primers flanking the siRNA target site should be avoided when measuring knockdown of target mRNA by real-time RT-qPCR.

Conjugative transfer of clostridial shuttle vectors from Escherichia coli to Clostridium difficile through circumvention of the restriction barrier.

Progress towards understanding the molecular basis of virulence in Clostridium difficile has been hindered by the lack of effective gene transfer systems. We have now, for the first time, developed procedures that may be used to introduce autonomously replicating vectors into this organism through their conjugative, oriT-based mobilization from Escherichia coli donors. Successful transfer was achieved through the use of a plasmid replicon isolated from an indigenous C. difficile plasmid, pCD6, and through the characterization and subsequent circumvention of host restriction/modification (RM) systems. The characterized replicon is the first C. difficile plasmid replicon to be sequenced and encodes a large replication protein (RepA) and a repetitive region composed of a 35 bp iteron sequence repeated seven times. Strain CD6 has two RM systems, CdiCD6I/M.CdiCD6I and CdiCD6II/M. CdiCD6II, with equivalent specificities to Sau96I/M. Sau96I (5'-GGNMCC-3') and MboI/M. MboI (5'-GMATC-3') respectively. A second strain (CD3) possesses a type IIs restriction enzyme, Cdi I, which cleaves the sequence 5'-CATCG-3' between the fourth and fifth nucleotide to give a blunt-ended fragment. This is the first time that an enzyme with this specificity has been reported. The sequential addition of this site to vectors showed that each site caused between a five- and 16-fold reduction in transfer efficiency. The transfer efficiencies achieved with both strains equated to between 1.0 x 10-6 and 5.5 x 10-5 transconjugants per donor.

The development of Clostridium difficile genetic systems.

Clostridum difficile is a major cause of healthcare-associated disease in the western world, and is particularly prominent in the elderly. Its incidence is rising concomitant with increasing longevity. More effective countermeasures are required. However, the pathogenesis of C. difficile infection is poorly understood. The lack of effective genetic tools is a principal reason for this ignorance. For many years, the only tools available for the transfer of genes into C. difficile have been conjugative transposons, such as Tn916, delivered via filter mating from Bacillus subtilis donors. They insert into a preferred site within the genome. Therefore, they may not be employed for classical mutagenesis studies, but can be employed to modulate gene function through the delivery of antisense RNA. Attempts to develop transformation procedures have so far met with little success. However, in recent years the situation has been dramatically improved through the demonstration of efficient conjugative transfer of both replication-proficient and replication-deficient plasmids from Escherichia coli donors. This efficient transfer can only be achieved in certain strains through negation of the indigenous restriction barrier, and is generally most effective when the plasmid employed is based on the replicon of the C. difficile plasmid, pCD6.