Bradycardia and hypotension associated with severe hemorrhage are reversed by morphine given centrally or peripherally in anesthetized rats

When is the best time to fix fractures?

The best time to operate on a fracture is governed in part by the nature of the fracture itself. It is also influenced by the premorbid condition of the patient and by the degree that associated injuries have disrupted normal processes. It is likely that some patients have a period of increased physiological risk for intervention, during which a second insult will result in further harm. The picture is not yet fully clear but relates to variations in the inflammatory response to trauma. One consistent lesson appears to resonate throughout the published literature. The most predictable risk factor for iatrogenic physiological disturbance is transfer to the operating theatre before adequate resuscitation of the patient has taken place.

Haemodynamic changes in trauma

Trauma is the leading cause of death during the first four decades of life in the developed countries. Its haemodynamic response underpins the patient's initial ability to survive, and the response to treatment and subsequent morbidity and resolution. Trauma causes a number of insults including haemorrhage, tissue injury (nociception) and, predominantly, in military casualties, blast from explosions. This article discusses aspects of the haemodynamic responses to these insults and subsequent treatment. 'Simple' haemorrhage (blood loss without significant volume of tissue damage) causes a biphasic response: mean arterial blood pressure (MBP) is initially maintained by the baroreflex (tachycardia and increased vascular resistance, Phase 1), followed by a sudden decrease in MAP initiated by a second reflex (decrease in vascular resistance and bradycardia, Phase 2). Phase 2 may be protective. The response to tissue injury attenuates Phase 2 and may cause a deleterious haemodynamic redistribution that compromises blood flow to some vital organs. In contrast, thoracic blast exposure augments Phase 2 of the response to haemorrhage. However, hypoxaemia from lung injury limits the effectiveness of hypotensive resuscitation by augmenting the attendant shock state. An alternative strategy ('hybrid resuscitation') whereby tissue perfusion is increased after the first hour of hypotensive resuscitation by adopting a revised normotensive target may ameliorate these problems. Finally, morphine also attenuates Phase 2 of the response to haemorrhage in some, but not all, species and this is associated with poor outcome. The impact on human patients is currently unknown and is the subject of a current physiological investigation.

Combat Casualty Care research programme

The Combat Casualty Care research programme is an integrated suite of projects designed to address Defence Medical Services' research needs for casualty care. The programme covers a broad spectrum of topics ranging from the pathophysiological and immunological impact of military relevant injuries to the effects of these disturbances on the response to early treatment. Dstl Porton Down has a long history of studying military injuries and has developed models, both in vivo and physical, to address the research needs. The work is conducted in close collaboration with clinical colleagues at the Royal Centre for Defence Medicine who have direct experience of the clinical issues faced by combat casualties and insights into the potential clinical implications of emerging strategies. This article reviews progress in research areas spanning forward resuscitation, with a particular focus on blast-related injuries, trauma coagulopathy, effects of drugs on the response to haemorrhage and deployed research. A significant 'value added' component has been the underpinning of higher degrees for seconded military clinicians at Dstl Porton Down who have made a valuable contribution to the overall programme.

HEMODYNAMIC AND IMMUNE CONSEQUENCES OF OPIATE ANALGESIA AFTER TRAUMA/HEMORRHAGE

The regulation of compensatory hemodynamic, inflammatory, and metabolic counter-regulatory responses to traumatic injury (trauma/hemorrhage [tx/hem]) and subsequent inflammatory challenges during the post-tx/hem period relies on balanced activation of neuroendocrine and opioid pathways. Pharmacological interventions during the rescue period as well as during the early post-tx/hem period that target these regulatory pathways can potentially affect the activation or efficacy of compensatory mechanisms. Their impact on mechanisms involved in these responses has not been well defined. We examined the impact of morphine and ketamine on immediate hemodynamic responses to tx/hem as well as on the integrity of host defense mechanisms at day 5 post-tx/hem. Morphine (10 mg/kg), ketamine (18 mg/kg), or saline (0.3 ml) were injected intraperitoneally at 15 min post-tx/hem (soft tissue injury and fixed pressure hemorrhage, 40 mmHg, 60 min) and 15 min before lactated Ringer's fluid resuscitation (LRFR, 2.4x total blood volume removed). Morphine, but not ketamine, produced effective and sustained analgesia. Morphine and ketamine impaired the rise in mean arterial blood pressure (MABP) during LRFR and increased 48-h mortality (2- to 3-fold). Morphine and ketamine markedly (40%-80%) attenuated the systemic LPS- (100 microg/100 g body weight) induced TNF response at day 5 post-tx/hem. Morphine attenuated LPS-induced lung and spleen TNF expression, whereas ketamine enhanced spleen TNF expression but did not alter lung responses. Subsequent studies demonstrated that the morphine-induced impairment of the response was not due to altered cytokine responses during the early post-tx/hem period but that they could be restored and 24 h mortality could be reduced by increasing the volume of LRFR (2-fold). These results indicate that morphine and ketamine analgesia compromise the hemodynamic and host defense responses after tx/hem, directly affecting mortality and morbidity during the recovery period.