Cardiovascular, adrenocorticotropin, and cortisol responses to hypertonic saline in euvolemic sheep are altered by prostaglandin synthase inhibition

The role of hypertonic saline dextran in trauma resuscitation

Modern trauma management has recognized the importance of using conservative fluid resuscitation regimes in order to prevent complications from fluid overload arising. Hypertonic/hyperoncotic fluids appear to provide an ideal means of facilitating this, requiring only small volumes to rapidly elevate blood pressure. Hypertonic saline dextran (HSD) was introduced in 1985 but its take up has been slow, a large part of this has been due to the lack of human trials and concerns about complications.

The current evidence has been reviewed and it is clear that HSD is an efficient means of correcting hypotension, doing so mainly by the mobilizing endogenous water. It is becoming apparent that early administration has the potential to modulate the inflammatory cascade in patients at risk of developing adult respiratory distress syndrome (ARDS) and multiorgan failure. This is reflected in the handful of human trials that show a trend towards increased survival (particularly for head injuries) and a possible reduction in ARDS. The side effect profile appears to be good, even in the presence of dehydration or penetrating trauma.

Published human trials have methodological problems and lack of power of study this has led to a reliance on animal studies. Clearly there is great potential, but before large-scale prehospital usage can be justified further well-conducted randomized human trials are needed.

Review article: hypertonic saline use in the emergency department

Hypertonic saline (HS) is being increasingly used for the management of a variety of conditions, most notably raised intracranial pressure. This article reviews the available evidence on HS solutions as they relate to emergency medicine, and develops a set of recommendations for its use. To conclude, HS is recommended as an alternative to mannitol for treating raised intracranial pressure in traumatic brain injury. HS is also recommended for treating severe and symptomatic hyponatremia, and is worth considering for both recalcitrant tricyclic antidepressant toxicity and for cerebral oedema complicating paediatric diabetic ketoacidosis. HS is not recommended for hypovolaemic resuscitation.

The effects of 10% hypertonic saline, 0.9% saline and hydroxy ethyl starch infusions on hydro-electrolyte status and adrenal function in healthy conscious dogs

The purpose of this study was to investigate the influence of different saline and colloid solutions on adrenal steroid secretion in dogs. Six healthy male Beagles underwent three infusion cycles: 10 min infusion of 30 ml/kg of NaCl 0.9%, 5 ml/kg of hydroxy ethyl starch, or 5 ml/kg of NaCl 10%. Plasma osmolality, hematocrit, total solids, cortisol and aldosterone levels were measured at 0, 5, 15, 30, 60, 120, 180 and 240 min after beginning infusion. Plasma ACTH levels were measured at 0, 15 and 240 min. An identical timing of sampling was applied during a control session omitting the fluid infusion. Osmolality, sodium, chloride and cortisol levels were found to be significantly higher with hypertonic saline solute compared to control. All fluid infusions lead to lowered plasma potassium, hematocrit, total solids and aldosterone values. ACTH concentrations did not show significant changes with any of the infusion cycles. The increase in cortisol levels suggests that hypertonic saline infusion could be interesting in critical care resuscitation, particularly in patients who are suffering from relative adrenal insufficiency.

Traumatic brain injury

PURPOSE OF REVIEW

Management of the patient with traumatic brain injury is a rapidly advancing field, characterized in recent years by an improved understanding of intracranial pathophysiology and ways in which outcomes can be improved. Many traditional therapies, such as fluid restriction and hyperventilation, have been called into question and are no longer recommended. Other proposed therapies, such as deliberate hypothermia, remain controversial. This detailed review of the recent literature helps the reader come to an understanding of current scientific and evidence-based practices in this area, with emphasis on those therapies most likely to be of use to the practicing intensivist.

RECENT FINDINGS

High-quality care of the traumatic brain injury patient demands the integrated activities of a number of different medical and nursing specialties. The best outcomes today are achieved by those systems that are able to focus as a team on the collective goal of minimizing secondary brain injury, and the respiratory therapist adjusting the patient's mechanical ventilation may be just as important to this effort as the attending neurosurgeon. Although the search for new diagnostic, prognostic, and therapeutic modalities continues (many of the more promising of which are reviewed in this article), it is clear that there exists no "silver bullet" therapy that will help all patients. Instead, it is the systematic integration and application of many small advances that will ultimately lead to better outcomes.

SUMMARY

Some issues in traumatic brain injury have now been resolved, and specific recommendations can be made. Fluid therapy directed toward a euvolemic state is now universally recommended, for example, as is the role of intracranial pressure monitoring. Other areas, such as the use of hypertonic saline, remain controversial. In both cases the authors have made an effort to cite the most recent literature, so that readers can draw their own conclusions from the original source material.

Traumatic brain injury in infants and children: mechanisms of secondary damage and treatment in the intensive care unit

Unfortunately no specific pharmacologic therapies are available for the treatment of TBI in patients. Current investigation of contemporary therapies for the treatment of TBI consists of recycling of previously tested therapies in the era of contemporary neurointensive care. These therapies include hypothermia, decompressive craniectomy, osmotherapy, and controlled hyperventilation. It is hoped that more detailed knowledge regarding the dominant pathophysiologic mechanisms associated with TBI-excitotoxicity, CBF dysregulation, oxidative stress, and programmed cell death-will catapult an efficacious intervention from the laboratory bench to the bedside. This intervention may be a potent agent targeting a single dominant pathway, a broad-spectrum intervention such as hypothermia, or, more likely, a combination of therapies. Meanwhile, practitioners must offer meticulous supportive neurointensive care using clinically proven therapies aimed at minimizing cerebral swelling for the management of pediatric patients who are victims of TBI.

Cellular localization of thromboxane synthase in ovine spinal cord and hindbrain

We and others have demonstrated that endogenously-produced prostanoids modify the function of the hypothalamus-pituitary-adrenal (HPA) axis. We have demonstrated that exogenously-administered thromboxane mimetic stimulates ACTH secretion in fetal sheep, and that the endogenous production of thromboxane modifies the HPA response to cardiovascular stress. The purpose of this study was to identify the structures within the fetal and adult ovine medulla and hindbrain which express immunoreactive thromboxane synthase. Using immunohistochemical techniques, we demonstrated thromboxane synthase immunostaining in regions important for cardiovascular afferent signaling (nucleus tractus solitarius, ventrolateral medulla) in both cell bodies and axons. Thromboxane synthase was also apparent in neuroanatomical locations which are consistent with afferent and efferent projections from the cerebellum. We observed staining in the superior cerebellar peduncle in the rostal pons, in the corticopontocerebellar fibers, and in Purkinje cells. The enzyme was found in motor regions, including the dorsal motor nucleus of the vagus nerve, and in the motor neurons of the dorsal column of the spinal cord. In addition to the apparent neuronal staining, there was positive staining in the ventricular ependymal cells. We conclude that, consistent with physiological evidence, thromboxane synthase is present in brain regions which are important for afferent and efferent cardiovascular signaling.

Promising strategies to minimize secondary brain injury after head trauma

OBJECTIVE

To review novel therapeutic approaches in the treatment of severe traumatic brain injury.

DESIGN

Eighty-three studies were reviewed specific to the treatment of traumatic brain injury, in either experimental models or in patients.

CONCLUSION

Four therapeutic strategies appear to be the most promising approaches currently in clinical trials for severe traumatic brain injury: a) the novel pharmacologic agent dexanabinol; b) hypertonic saline; c) mild hypothermia; and d) decompressive craniectomy. Each of these therapies share the common feature of targeting multiple mechanisms, suggesting this may be an important factor to the development of a successful approach to severe traumatic brain injury.

The effects of repeated dosing with 7.5% sodium chloride/6% dextran following uncontrolled intra-abdominal hemorrhage

The use of hypertonic saline Dextran (HSD) for resuscitation following trauma has many potential benefits, especially for the treatment of military casualties, but there is very limited data on the responses following multiple dosing with this fluid. The effects of a second dose of hypertonic saline dextran for resuscitation of uncontrolled intra-abdominal haemorrhage were studied in an experimental model. Under general anaesthesia, 17 large white pigs (weight range, 48-67 kg) were subjected to uncontrolled hemorrhage produced by a tear in the common iliac artery. This resulted in a significant (P < 0.01) reduction of both mean arterial pressure (MAP) and cardiac index. One hour after injury, animals were assigned to one of three groups, receiving either no resuscitation (Group A), or two doses of HSD (at a dose rate of 4 mL/kg), administered either 1 and 4 h after injury (Group B) or 1 and 7 h after injury (Group C). Animals were monitored for 12 h post-injury. A second infusion of HSD caused a significant hypernatremia and diuresis (P< 0.01) in both Groups B and C. There was a non-significant rise in MAP in both treatment groups, and in Group B only, there was a significant increase in cardiac index (P= 0.014). It is concluded that repeat administration of HSD for the resuscitation of uncontrolled hemorrhage results in limited cardiovascular improvements, but that the metabolic sequelae are potentially detrimental to survival.