Optimizing the respiratory pump: harnessing inspiratory resistance to treat systemic hypotension.

We review the physiology and affects of inspiration through a low level of added resistance for the treatment of hypotension. Recent animal and clinical studies demonstrated that one of the body's natural response mechanisms to hypotension is to harness the respiratory pump to increase circulation. That finding is consistent with observations, in the 1960s, about the effect of lowering intrathoracic pressure on key physiological and hemodynamic variables. We describe studies that focused on the fundamental relationship between the generation of negative intrathoracic pressure during inspiration through a low level of resistance created by an impedance threshold device and the physiologic sequelae of a respiratory pump. A decrease in intrathoracic pressure during inspiration through a fixed resistance resulting in a pressure difference of 7 cm H(2)O has multiple physiological benefits, including: enhanced venous return and cardiac stroke volume, lower intracranial pressure, resetting of the cardiac baroreflex, elevated cerebral blood flow oscillations, increased tissue blood flow/pressure gradient, and maintenance of the integrity of the baroreflex-mediated coherence between arterial pressure and sympathetic nerve activity. While breathing has traditionally been thought primarily to provide gas exchange, studies of the mechanisms involved in animals and humans provide the physiological underpinnings for "the other side of breathing": to increase circulation to the heart and brain, especially in the setting of physiological stress. The existing results support the use of the intrathoracic pump to treat clinical conditions associated with hypotension, including orthostatic hypotension, hypotension during and after hemodialysis, hemorrhagic shock, heat stroke, septic shock, and cardiac arrest. Harnessing these fundamental mechanisms that control cardiopulmonary physiology provides new opportunities for respiratory therapists and others who have traditionally focused on ventilation to also help treat serious and often life-threatening circulatory disorders.

Evaluation and management of the trauma patient for the interventional radiologist.

Interventional radiologists are adopting an increasingly important role in the evaluation and management of the acutely injured patient. The interventional radiologist may be called upon to provide services while hemorrhage is active, the patient is hemodynamically compromised, and a comprehensive trauma assessment is incomplete. The initial diagnostic and management approach to the trauma patient is optimally organized through the principles of advanced trauma life support. A basic understanding of common injury patterns, immediate lifesaving interventions, and principles of resuscitation is of value to the interventional radiologist in his or her interactions with the trauma team and contribution to patient care.

Hormone replacement therapy in brain-dead organ donors: a comprehensive review with an emphasis on traumatic brain injury.

BACKGROUND: Organ shortage is an ongoing problem in the United States. Most donor organs are procured following brain death and a significant portion of brain-dead donors result from devastating brain injury. Without a standard practice for hormone replacement therapy (HRT) in the setting of brain death, a comprehensive review of the literature was deemed necessary. METHODS: A search of published literature was conducted with terms "TBI" or "brain injury" or "head injury" AND "hormone" or "management" AND "organ" AND "donor" or "donation." Abstracts and full texts were screened for relevance and inclusion of information on HRT. Additional studies were selected from references cited within these. Excluded studies were non-English, nonhuman based, or had small sample size, (i.e., case reports or series with fewer than five subjects). RESULTS: Fifteen studies were selected for inclusion and contained Level III or Level IV evidence. Combinations of thyroid hormone, insulin, and corticosteroids were the most commonly cited HRT. Ninety-three percent of studies found a significant increase in organ procurement rate among donors who received HRT. Hormone replacement therapy was administered after brain death declaration in eight studies. Only two studies specifically explored the effects of starting HRT earlier and identified even greater procurement rates. Four studies were specific to traumatic brain injury (TBI); the remaining 11 studies involved TBI in 22% to 89% of the sample. CONCLUSION: Organ shortage remains a growing problem in the United States. Donor management including HRT has been proposed to combat the endocrine derangement associated with brain death and, in particular, TBI. While the existing literature reported compelling outcomes using HRT, there remains a need for further Level I and Level II evidence studies to define optimal practice. LEVEL OF EVIDENCE: Review article, level IV.