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Biomedical subjects

C D Deakin

Publications and source records attributed to C D Deakin.

At least 19 recordsLinked to original sources
PubMed2006

Does telephone triage of emergency (999) calls using Advanced Medical Priority Dispatch (AMPDS) with Department of Health (DH) call prioritisation effectively identify patients with an acute coronary syndrome? An audit of 42,657 emergency calls to Hampshire Ambulance Service NHS Trust.

INTRODUCTION: The National Service Framework for Coronary Heart Disease requires identification of patients with an acute coronary syndrome (ACS) to enable prompt identification of those who may subsequently require pre-hospital thrombolysis. The Advanced Medical Priority Dispatch System (AMPDS) with Department of Health (DH) call prioritisation is now the common triage tool for emergency ('999') calls in the UK. We retrospectively examined patients with ACS to identify whether this triage tool had been able to allocate an appropriate emergency response. METHODS: All emergency calls to Hampshire Ambulance Service NHS Trust (HAST) from the Southampton area over an 8 month period (January to August 2004) were analysed. The classification allocated to the patient by AMPDS (version 10.4) was specifically identified. Data from the Myocardial Infarct National Audit Project) were obtained from the receiving hospital in Southampton to identify the actual number of patients with a true ACS. RESULTS: In total, 42 657 emergency calls were made to HAST from the Southampton area. Of these, 263 patients were subsequently diagnosed in hospital as having an ACS. Of these 263 patients, 76 presented without chest pain. Sensitivity of AMPDS for detecting ACS in this sample was 71.1% and specificity 92.5%. Positive predictive value was 5.6% (95% confidence interval 4.8 to 6.4%), and 12.5% (33/263) of patients with confirmed ACS were classified as non-life threatening (category B) incidents. CONCLUSION: Only one of approximately every 18 patients with chest pain has an ACS. AMPDS with DH call prioritisation is not a tool designed for clinical diagnosis, and its extension into this field does not enable accurate identification of patients with ACS.

Chest Pain↗
PubMed2005

Securing the prehospital airway: a comparison of laryngeal mask insertion and endotracheal intubation by UK paramedics.

OBJECTIVES: The recent introduction of a disposable laryngeal mask airway has provided paramedics with an alternative to endotracheal intubation. Time taken to secure the airway with each device was compared in patients undergoing elective surgery. METHODS: Patients undergoing general anaesthesia were studied. Paramedics trained in laryngeal mask use and endotracheal intubation participated in the study. A Portex disposable laryngeal mask was inserted and removed, followed by a Portex endotracheal tube. Time taken from beginning of the procedure to ventilation of the patient was recorded. RESULTS: Laryngeal mask insertion and endotracheal intubation was attempted on 52 patients. Median age was 63.5 years (range 39-83). Laryngeal mask insertion was successful in 88.5% (46 of 52) patients; endotracheal intubation was successful in 71.2% (37 of 52) patients (after no more than two attempts), p = 0.049. Intubation success was related to laryngoscopic view (87.5% grade 1, 56.3% grade 2, 0.0% grade 3. p<0.0001). When laryngeal mask/endotracheal tube insertion were both successful (n = 35 of 52), there was no significant difference in median time to secure the airway (laryngeal mask 47.0 seconds (range 24-126) compared with endotracheal tube 52.0 seconds (range 27-148) p = 0.22). Laryngeal mask insertion was successful in 80.0% (12 of 15) patients in whom endotracheal intubation had failed. CONCLUSIONS: Even under optimal conditions, 30% of attempts at intubation by paramedics were unsuccessful. A disposable laryngeal mask has a higher success rate in securing the airway and overall, secures the airway more reliably than endotracheal intubation.

Adult↗
PubMed2004

Reducing allogeneic transfusion in cardiac surgery: a randomized double-blind placebo-controlled trial of antifibrinolytic therapies used in addition to intra-operative cell salvage.

BACKGROUND: The transfusion of allogeneic red blood cells and allogeneic coagulation products is associated with risk to the patient and the depletion of an increasingly scarce resource. This prospective, randomized, double-blind, placebo-controlled trial investigated practices to avoid transfusion in patients undergoing first-time cardiac surgery. METHODS: Patients were randomized to one of three treatment groups: an aprotinin group, a tranexamic acid group, and a control group receiving normal saline. Intra-operative cell salvage was used for all patients. The primary outcomes were the number of patients exposed to allogeneic red blood cells, allogeneic coagulation products or any allogeneic transfusion (allogeneic red blood cells and/or allogeneic coagulation products). RESULTS: Patients were 2.5 times more likely to receive any allogeneic transfusion in the tranexamic group than in the aprotinin group (21 patients out of 60 compared with nine out of 60, respectively). The relative risk of any allogeneic transfusion comparing aprotinin with tranexamic acid was 0.43 (95% confidence interval 0.21-0.86; P=0.019). Patients in the control group were four times more likely to receive any allogeneic transfusion when compared with the aprotinin group (37 patients out of 60 compared with nine out of 60, respectively). The relative risk of any allogeneic transfusion comparing aprotinin with control was 0.24 (95% confidence interval 0.13-0.46; P<0.001). CONCLUSIONS: When used in addition to intra-operative cell salvage, aprotinin is the most efficacious pharmacological therapy for reducing patient exposure to any allogeneic transfusion during first-time cardiac surgery.

Adult↗
PubMed2004

Laryngopharyngeal pH measurement.

OBJECTIVES: Most emergency department (ED) intubations are to prevent gastric contents aspiration. The incidence of aspiration is unknown and intubation has complications. Balancing these risks requires an idea of the incidence of aspiration. This study assessed one technique for investigating the aspiration risk in ED patients. Cricoid pressure is used to reduce this risk and the technique may also examine this manoeuvre. METHODS: Cohorts of unconscious adult ED and elective surgical patients were recruited. The posterior pharyngeal wall pH was measured immediately before and after intubation. Pharyngeal pH was used to indicate risk of aspiration, and pH change to assess the efficacy of cricoid pressure. RESULTS: Eight ED and 48 control patients were recruited. In the ED cohort, pH ranged from 6.0 to 8.0 before intubation and 4.7 to 8.0 after intubation: a mean decrease of 0.3 (95% CI 1.5 decrease to 0.9 increase). In the control cohort pH ranged from 5.8 to 8.0 before intubation and 6.0 to 8.0 after intubation: a mean increase of 0.4 (95% CI 0.1 to 0.6 increase). CONCLUSIONS: This is a simple, cheap, and repeatable technique for assessing aspiration risk in emergency intubations. A larger study is required to assess the efficacy of cricoid pressure.

Adult↗
PubMed2001

How often should defibrillation pads be changed?: the effect of evaporative drying.

OBJECTIVE: In order to minimise transthoracic impedance (TTI) during defibrillation, water-based pads are used to improve conductivity between metal defibrillation paddles and skin. Subjectively, these pads appear to dry very quickly; an effect that may lead to an increase in TTI due to poorer conduction between paddles and skin. This study was carried out to assess the effect of evaporative drying of defibrillation pads on TTI. MATERIALS AND METHODS: TTI was measured at 5-10 min intervals in 20 adult male volunteers across 3M defibrillation pads (2346N) placed in the anterior-apical position. Measurements of TTI were made at 30 kHz using a Bodystat MultiScan 5000 monitor at end-expiration. A third pad was placed on the left precordium and its mass recorded each time a TTI measurement was made. RESULTS: The median age of subjects was 22 years (range 21-52 years) and their median body mass index was 23.1 kg m(-2) (range 18.4-42.8 kg m(-2)). Median room temperature was 23.0 degrees C (range 19.0-24.0 degrees C) and the median humidity was 31.0% (range 28.0-48.0%). 3M defibrillation pads had an initial mean mass of 25.14 g (S.D. +/- 0.41 g). Changes in defibrillation pad mass due to evaporative loss occurred immediately and rapidly, with all measurements being significantly lower than the baseline value. Mean baseline TTI was 63.6 ohms (S.D. +/- 13.7 ohms). After 30 min a statistically significant (P = 0.012) rise of 1.4 ohms (2.2%), was observed corresponding to a 12.6% decrease in pad mass, after which TTI continued to increase in a linear fashion. CONCLUSION: In the absence of a defibrillation current. 3M defibrillation pads can safely be left on the chest wall for at least 25 min in a typical hospital environment before evaporative drying results in a significant increase in transthoracic impedance.

Adult↗
PubMed2001

Does paddle force applied during defibrillation meet advanced life support guidelines of the European Resuscitation Council?

OBJECTIVES: to determine whether paddle force applied during defibrillation meets the 12 kg (approximately 120 N) force recommended by the advanced life support (ALS) guidelines of the European Resuscitation Council (ERC). MATERIALS AND METHODS: an adult mannequin was "defibrillated" using standard defibrillation paddles instrumented to measure paddle force. Paddle force was recorded at the time the discharge buttons on the paddle handles were depressed. RESULTS: 54 doctors and nurses performed simulated defibrillation on a mannequin. Median sternal paddle force was 60.6 N (range 26.1-132.8 N) and median apical paddle force was 59.5 N (range 18.6-118.5 N). Only 3/54 operators (5.6%) applied sternal paddle force equal to or in excess of ERC recommendations. No operator applied apical paddle force equal to or in excess of ERC recommendations. CONCLUSIONS: force applied to defibrillation paddles does not meet guidelines of the European Resuscitation Council. Greater emphasis during advanced life support training should be placed on the importance of firm paddle force during defibrillation.

Adult↗
PubMed2001

Evidence-based guidelines for the use of defibrillation pads.

OBJECTIVE: Defibrillation pads are used routinely at both cardiac arrests and cardioversion procedures. There are currently no evidence-based guidelines on how often pads should be replaced, although it has been suggested that they should be changed as often as every three shocks to maintain optimal performance. Previously, we have shown that on exposure to air, pad mass diminishes over time due to evaporation--an effect likely to lead to poorer conduction between skin and paddle. This prospective study was designed to determine if evaporation is accelerated by the passage of a defibrillation current and to formulate evidence-based guidelines for defibrillation pad replacement. MATERIALS AND METHODS: 3M defibrillation pads (2346N) were collected from acute wards and emergency departments in two hospitals in the UK over a 2 month period. The duration of exposure to air, number and energy of shocks, and type of procedure were recorded. When no longer required, pad masses were determined and the loss of pad mass due to evaporation calculated. RESULTS: 26 pairs of pads were collected from 14 cardiac arrests and 12 cardioversions. The total defibrillation energy used ranged from 150 to 5080 J and evaporative drying time from 4 to 38 min. The rate of evaporation from these pads (86.1 mg x min(-1)) was not significantly different from pads previously studied on volunteers in the absence of a defibrillation current (99.4 mg x min(-1)). Of the defibrillation pads exposed to air for less than 30 min, in only one of 49 pads was the loss of mass due to evaporation consistent with a significant increase in transthoracic impedance (TTI). Correspondingly, of two pads used for more than 30 min, both attained a mass consistent with a significant increase in TTI. CONCLUSIONS: Defibrillation pads can be used for up to 30 min without evaporation causing a clinically significant increase in TTI. The passage of a defibrillation current across pads does not further accelerate water loss.

Electric Countershock↗
PubMed2001

Are European Resuscitation Council recommendations for paddle force achievable during defibrillation?

Transthoracic impedance (TTI) is an important determinant of success in defibrillation. Low TTI increases transmyocardial current and therefore increases the chance of depolarising a critical mass of myocardium. A major component of TTI occurs at the paddle-skin interface and is minimised by pressure applied to the defibrillation paddles. The International Liaison Committee on Resuscitation (ILCOR) 2000 guidelines recommend that 'firm force' should be applied to both paddles, whereas previous European Resuscitation Council (ERC) 1992 guidelines were more precise, recommending that 12 kg of force should to be applied. We assessed whether defibrillator operators are capable of achieving 12 kg paddle force. Fifty advanced life support-trained doctors and nurses attempted to achieve 12 kg paddle force while simulating defibrillation on a resuscitation doll. The median value of the maximum pressures obtainable was 10.1 (max 16.0; min 5.0) kg force. Only 14% could achieve > or =12 kg force on both paddles for defibrillation. Men achieved more force than women (10.7 vs. 8.1 kg force; P<0.01), and there was a correlation between maximum force achieved and operator height (r2=0.27) and dominant hand-grip strength (r2=0.34). The ERC recommendation of 12 kg paddle force is not achievable by the majority of defibrillator operators.

Cardiography, Impedance↗
PubMed2001

Autotransfusion decreases blood usage following cardiac surgery -- a prospective randomized trial.

INTRODUCTION: 10% of blood issued by the National Blood Service (220,000) is utilised in cardiac procedures. Transfusion reactions, infection risk and cost should stimulate us to decrease this transfusion rate. We tested the efficacy of autotransfusion of washed postoperative mediastinal fluid in a prospective randomized trial. PATIENTS AND METHODS: 166 patients undergoing coronary artery bypass grafting (CABG), valve or CABG + valve procedures were randomized into three groups. The indication for transfusion was a postoperative haemoglobin (Hb) < 10 g/l or a packed cell volume (PCV) < 30. When applicable, group A patients received washed post-operative drainage fluid. Group B all received blood processed from the cardiopulmonary bypass (CPB) circuit following separation from CPB and if appropriate washed post-operative drainage fluid. Group C were controls. Groups were compared using analysis of variance. RESULTS: There was no significant difference in age, sex, type of operation, CPB time and preoperative Hb and PCV between the groups. Blood requirements were as shown. [table - see text] Twelve patients in group A and 10 in group B did not require a homologous transfusion following processing of the mediastinal drainage fluid. CONCLUSION: Autotransfusion of washed postoperative mediastinal fluid can decrease the amount of homologous blood transfused following cardiac surgery. There was no demonstrable benefit in processing blood from the CPB circuit as well as mediastinal drainage fluid.

Adult↗
PubMed2001

Do physiological changes in pregnancy change defibrillation energy requirements?

Resuscitation during pregnancy is uncommon, with approximately 70 deaths occurring during pregnancy in the UK per annum. Physiological changes during pregnancy may affect transthoracic impedance (TTI), which determines transmyocardial current. Increased blood volume, cardiomegaly, haemodilution, changes in lung volume and changes in thoracic volume may alter impedance in ways that are difficult to predict. We measured TTI at term and after delivery once physiological changes had resolved. Mean (SD) TTI was 91.3 (15.8) Omega at term and 91.6 (11.8) Omega 6-8 weeks after delivery; the difference was not statistically significant. We conclude that current energy requirements for adult defibrillation are appropriate for use during pregnancy.

Adult↗
PubMed2001

Pre-hospital trauma care.

The chain of survival in outcome from major trauma is equally as important as its well established concept in survival from cardiac arrest. Preventive measures have been shown to be an effective means of reducing death from trauma, and the standard of pre-hospital care for those surviving the primary injury is improving in many trauma systems. The optimal pre-hospital interventions are still debated, but evidence suggests that patients with severe head injury in particular will benefit significantly from pre-hospital rapid-sequence intubation and field stabilization, whereas those with penetrating injury require rapid evacuation to hospital with minimal intervention. Pre-hospital asystole from trauma has a universally poor outcome. When delivering appropriate care, several helicopter-based systems have shown improvements in outcome compared with ground-based systems. The International Liaison Committee on Resuscitation recently published guidelines on resuscitation, with particular relevance to pre-hospital trauma care. The importance of bystander cardiopulmonary resuscitation, oxygenation, and the avoidance of iatrogenic morbidity are stressed.

Journal Article↗