Search PubMed⌕ Search

Biomedical subjects

C D Deakin

Publications and source records attributed to C D Deakin.

49 records · Page 3Linked to original sources
PubMed1998

Changes in core temperature compartment size on induction of general anaesthesia.

A two-compartment model of temperature distribution estimates the core compartment to occupy 66% of body mass at rest, while the peripheral compartment comprises the remainder. General anaesthesia impairs thermoregulation by central and peripheral actions. Peripheral vasodilatation accelerates heat transfer from the core to peripheral compartment causing the core compartment to cool and expand in size. Core hypothermia may be a significant cause of postoperative morbidity. This undocumented change in the size of the core compartment on induction of anaesthesia can be calculated. Core size increased from the established value of 66% before induction of general anaesthesia to 71.2 (SD 6)% of body mass, 20 min after induction of anaesthesia (P = 0.0001). On induction of general anaesthesia, the core compartment cools and expands while the peripheral compartment warms and contracts by a corresponding amount. Measurement of the magnitude of changes in core:periphery heat distribution on induction of anaesthesia contribute to a clearer understanding of the pathophysiology of perioperative hypothermia.

Adult↗
PubMed1996

Haemodynamic effects of descending aortic occlusion during cardiopulmonary resuscitation.

We describe two patients who both suffered a cardiac arrest whilst maintained on an intra-aortic balloon pump. In an attempt to improve coronary and cerebral blood flow during cardiopulmonary resuscitation, the intra-aortic balloon was inflated to occlude the descending aorta and preferentially direct blood to the cerebral and coronary circulation. In case 1, mean radial artery pressure rose from 71/14 mmHg (mean = 33 mmHg) to 92/24 mmHg (mean = 47 mmHg). Diastolic right atrial pressure was 16 mmHg both with the balloon deflated and inflated. In patient 2, mean radial artery pressure rose from 48/21 mmHg (mean = 25 mmHg) to 62/26 mmHg (mean = 36 mmHg). Right atrial pressure was 90/6 mmHg (mean 34 mmHg) with the balloon deflated and 104/8 mmHg (mean = 40 mmHg) with the balloon inflated. Coronary artery perfusion pressure in case 1 increased from -2 to 8 mmHg and in case 2 increased from 15 to 18 mmHg. These results suggest that occlusion of the descending aorta during cardiac massage may improve coronary and cerebral perfusion pressures. Animal studies are consistent with these findings and show that aortic occlusion may significantly improve outcome from cardiac arrest.

Aorta, Thoracic↗
PubMed1996

Prehospital management of the traumatized airway.

Prehospital airway obstruction is common following traumatic injury. Airway management of these patients is difficult in the prehospital setting, particularly because those providing care are often not trained in the skills necessary for endotracheal intubation. As a result, a number of alternative devices are available for airway maintenance. Nevertheless, endotracheal intubation remains the gold standard in airway management. Although it provides the optimum airway and protects the airway from aspiration, its successful insertion requires regular training. Incorrect placement carries considerable risk. The laryngeal mask airway may be a suitable alternative for many situations and appears to be the best alternative to endotracheal intubation. Training in its use is straightforward and it is relatively easy to insert. Risks of aspiration appear small. The pharyngotracheal lumen airway and Combitube are both more difficult to use than the laryngeal mask airway and risk inflating the stomach if the devices are incorrectly used. Cricothyroidotomy is associated with serious complications but is only used where there is no other option. As with other techniques, it requires regular training in its use.

Airway Obstruction↗
PubMed1995

Simple thoracostomy avoids chest drain insertion in prehospital trauma.

Tension pneumothorax and hemothorax are life-threatening emergencies that require immediate treatment. Field stabilization of trauma patients often requires rapid surgical drainage of these injuries but inevitably delays departure for hospital. Conventional treatment involves the insertion of a chest drain but we describe a modified technique of simple thoracostomy that is faster and simpler to perform and avoids the risks associated with insertion of the chest drain. Following use of a simple thoracostomy as an alternative to chest drain insertion in 45 patients at the roadside, this technique appears to have important advantages over conventional techniques and warrants further clinical evaluation.

Adolescent↗
PubMed1994

AB or ABC: pre-hospital fluid management in major trauma.

Pre-hospital trauma care in the United Kingdom is a neglected field with little consideration being given to this phase. Of the 14,500 annual fatalities from road traffic accidents in this country, 60% die before reaching hospital and it has been estimated that one-third of these fatalities are due to hypovolaemia. The pre-hospital fluid resuscitation of trauma patients is a controversial area and although it would seem sensible to commence intravenous (i.v.) fluids at the roadside, several large studies have failed to show any benefit from this intervention. By delaying departure to hospital, initiation of i.v. fluid replacement may actually worsen outcome. This paper reviews recent studies and discusses current thought on pre-hospital fluid replacement in major trauma.

Emergency Medical Services↗
PubMed1994

Early fluid resuscitation in haemorrhagic shock.

For 25 years aggressive prehospital fluid administration in trauma patients has been common practice. Recent studies suggest that this may increase mortality in patients with hypovolaemic shock. These studies include retrospective analysis of patient survival, computer modelling of volume loss and replacement, controlled animal experiments, and clinical studies of trauma patients. Fluid resuscitation before definitive haemostasis has been achieved, may accelerate blood loss, cause hypothermia and result in a dilutional coagulopathy. Further studies are needed to establish optimum volume replacement in trauma patients with hypovolaemic shock.

Animals↗
PubMed1991

Cytoprotective effects of calcium channel blockers. Mechanisms and potential applications in hepatocellular injury.

Deregulation of calcium homeostasis is strongly implicated in the development of cellular injury, including in hepatocytes, and is thought to be the limiting step in transition to an irreversible stage. Calcium channel blockers appear to exert their cytoprotective effects through several mechanisms. These may involve blockade of L-(long-lasting)-type calcium channels, reduction of oxidative stress, antagonism at inflammatory mediator receptor sites and interaction at other intracellular sites. Studies relating to the liver are few but suggest that calcium channel blockers may have a role to play in limiting hepatocellular damage, especially those arising from exposure to a variety of toxic agents.

Animals↗
PubMed1991

Delayed calcium channel blockade with diltiazem reduces paracetamol hepatotoxicity in mice.

1. Diltiazem (30 mg kg-1 body weight, intraperitoneally) given to mice 9 h after paracetamol (450 mg kg-1, orally) reduced liver damage, as judged by plasma aspartate aminotransferase activity (median 186, range 6-602 IU 1(-1), n = 18 vs 466, range 23-3872 IU 1(-1) in 18 saline-treated controls; P less than 0.05) with comparable reductions in mortality (14% vs 33%, respectively; NS). 2. Regenerative activity, as judged by mitotic figures in tissue removed at 30 h after paracetamol, was significantly higher in mice treated at 9 h with diltiazem (median 0.83 per high power field vs 0.1 in saline-treated controls; P less than 0.05). 3. Diltiazem administered earlier or later than 9 h showed reduced efficacy and in some cases potentiated toxicity, as did nifedipine (40 mg kg-1 in divided doses up to 9 h).

Acetaminophen↗
PubMedDate not supplied

A comparison of transthoracic impedance using standard defibrillation paddles and self-adhesive defibrillation pads.

The success of defibrillation is related to transmyocardial current. This current is inversely proportional to transthoracic impedance (TTI). A similar TTI between different pads and paddles is important to deliver a consistent therapeutic dose to all subjects. Failure to do so may result in either insufficient or excessive transmyocardial current leading to a risk of failed defibrillation or tissue damage respectively. Several different types of defibrillation paddles and self-adhesive defibrillation pads are currently available for clinical use but the TTI achieved with each type has not been established. We measured TTI using two types of commonly used paddles and self-adhesive pads to establish whether any significant differences exist between the products. TTI in 40 adult males was measured using defibrillation paddles and self-adhesive defibrillation pads placed in the antero-apical position. Measurements were made using a 30 kHz low amplitude AC current and taken at end-expiration. Mean TTI (omega)+/-S.D. was 68.2+/-16.1 (Hewlett Packard paddles; A), 62.8+/-13.2 (Hewlett Packard pads; B), 64.6+/-14.3 (PhysioControl paddles; C) and 95.6+/-22.3 (PhysioControl pads; D). Significant differences existed between all groups (P < 0.05) except between B and C. Differences in TTI between A, B and C were small and probably of no clinical significance. TTI in group D is significantly larger. Although transmyocardial current is related to TTI, the relationship is complex and differences in TTI alone cannot predict the outcome from defibrillation.

Adult↗