Hypothermia in acute blunt head injury

The effect of induced hypothermia on the duration of action of atracurium when given by infusion to critically ill children

The aim of the study was to investigate the effect of induced hypothermia on the offset time of atracurium when given by continuous infusion to critically ill children. Over a period of 8 months, six mechanically ventilated children had a steady-state infusion of atracurium discontinued. The offset time of atracurium was assessed by train-of-four (TOF) stimulation of the ulnar nerve; recording the time taken to reach a TOF ratio of 0.9. Nine assessments were carried out. The mean offset time of atracurium was 82 min. This was significantly longer than in patients with temperatures within the normal physiological range. When considering all assessments, performed both in hypothermic and normothermic patients, there is a strong correlation between rectal temperature and the offset time of atracurium. Prolonged moderate hypothermia has a very significant effect on the offset time of atracurium when given by infusion to critically ill children.

Granulocyte colony-stimulating factor ameliorates life-threatening infections after combined therapy with barbiturates and mild hypothermia in patients with severe head injuries

OBJECTIVE

The objective of this study was to clarify the effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) administration on infections in patients with severe head injuries after combined therapy with high-dose barbiturates and mild hypothermia.

PATIENTS AND METHODS

Since 1996, we have administered rhG-CSF to eight patients with severe head injuries for 5 days (group G). Their treatment results were compared with those of 22 patients cared for earlier without rhG-CSF treatment (group N). All patients in both groups met the criteria of total leukocyte count (TLC) less than 5,000/mm3, C-reactive protein (CRP) over 10 mg/dL, and the presence of an infectious complication. Changes in the TLC, CRP, respiratory index, intracranial pressure, and infectious condition were evaluated in both groups. In addition, the nucleated cell count and differentiation from bone marrow aspiration, neutrophil functions, serum concentrations of interleukin-6, and plasma concentration of leukocyte elastase were evaluated in group G.

RESULTS

In group G, TLC, nucleated cell count, and neutrophil functions significantly increased, whereas CRP, respiratory index, and interleukin-6 decreased reciprocally. There was no deterioration of intracranial pressure and leukocyte elastase. Consequently, seven of the eight patients in group G recovered from life-threatening infections, and none of the eight patients died. However, in group N, CRP and respiratory index remained high and TLC did not increase as much as it did in group G. Infections continued after 5 days in 17 of the 22 patients, 7 of whom died from severe infections during hospitalization.

CONCLUSION

Administration of rhG-CSF ameliorated life-threatening infections without causing lung injury or increasing brain swelling in patients with severe head injuries who were treated with combined therapy involving high-dose barbiturates and mild hypothermia.

[Protective effect of hypothermia in cerebral ischemia]

The use of hypothermia to protect the brain from ischaemic insults is an old concept. During the last decades, studies have mainly shown a modulating effect of hypothermia on biochemical cerebral responses to ischaemia, in addition to the basic effect of energy savings. Thus, the beneficial effects of decreased brain temperature, even when limited during transient ischaemic insults, whether global or focal, complete or incomplete, have been established. The deeper the hypothermia, the longer the ischaemia can be prolonged with acceptable neurological outcome. Conversely, the effects of postischaemic hypothermia remain unclear, while extracerebral deleterious effects cannot be overlooked, and many parameters remain to be evaluated before undertaking a beneficial clinical trial. The only indication for therapeutic postischaemic hypothermia in the near future could be in the control of impending intracranial hypertension occurring after cerebral ischaemia.

Experience with prolonged induced hypothermia in severe head injury

BACKGROUND: Recent prospective controlled trials of induced moderate hypothermia (32-34 degrees C) for relatively short periods (24-48 h) in patients with severe head injury have suggested improvement in intracranial pressure control and outcome. It is possible that increased benefit might be achieved if hypothermia was maintained for more periods longer than 48 h, but there is little in the literature on the effects of prolonged moderate hypothermia in adults with severe head injury. We used moderate induced hypothermia (30-33 degrees C) in 43 patients with severe head injury for prolonged periods (mean 8 days, range 2-19 days). RESULTS: Although nosocomial pneumonia (defined in this study as both new chest radiograph changes and culture of a respiratory pathogen from tracheal aspirate) was quite common (45%), death from sepsis was rare (5%). Other findings included hypokalaemia on induction of hypothermia and a decreasing total white cell and platelet count over 10 days. There were no major cardiac arrhythmias. There was a satisfactory neurological outcome in 20 out of 43 patients (47%). CONCLUSION: Moderate hypothermia may be induced for more prolonged periods, and is a relatively safe and feasible therapeutic option in the treatment of selected patients with severe traumatic brain injury. Thus, further prospective controlled trials using induced hypothermia for longer periods than 48 h are warranted.

[Hypothermia in traumatology]

Basing on the experience of the Chamonix hospital team which managed in six years 89 cases of hypothermia in trauma patients, this article reviewed the literature concerning the association hypothermia-trauma. Shock is a major triggering factor. The deleterious effects of hypothermia on the outcome is due to inadequate cardiorespiratory adaptation to shock and to increased bleeding. Although a few articles reported a beneficial effect of hypothermia in head trauma, further studies are required to assess the value of deliberate hypothermia in such patients. Restoration of a satisfactory haemodynamic activity is a priority and most often requires surgery. The rewarming manoeuvres should be initiated early and always be preventive. They are active, internal and rapid in case of haemodynamic instability and when the central temperature is below 32 degrees C. It can be more progressive and less invasive in other cases. During recovery from anaesthesia the patient must be closely monitored. In spite of a possible protecting effect, hypothermia remains an aggravating factor in traumatology and must therefore be either prevented or amended.

Acute metabolic and endocrine effects of induced hypothermia in hemorrhagic shock: an experimental study in the pig

BACKGROUND

Hypothermia is considered harmful in trauma patients. In surgery, hypothermia is occasionally used to reduce metabolism and protect the brain. Recent studies in animals have also shown protective effects of hypothermia in hemorrhagic shock. The aim of this study was to evaluate the metabolic and endocrine effects of induced hypothermia in hemorrhagic shock.

METHODS

Half of the individually calculated blood volume was removed from 17 anesthetized piglets. They were then randomized to normothermia or hypothermia and followed for 4 hours after hemorrhage.

RESULTS

In the hypothermic pigs, arterial PO2 increased from 10.3 +/- 0.7 to 16.4 +/- 0.9 kPa, but it remained unchanged in the normothermic group. The serum levels of potassium increased from 3.9 +/- 0.2 to 5.0 +/- 0.2 mmol/L in the normothermic group. In the hypothermic pigs, the potassium levels temporarily decreased from 3.8 +/- 0.1 to 3.0 +/- 0.1 mmol/L but then returned to baseline levels. The levels of serum catecholamines surged in both groups during hemorrhage. They remained elevated in normothermic pigs but declined in the hypothermic group.

CONCLUSION

In porcine hemorrhagic shock, induced hypothermia increases arterial oxygen tension and stabilizes serum levels of potassium and catecholamines.

Cerebro-protective effects of ENA713, a novel acetylcholinesterase inhibitor, in closed head injury in the rat

Focal ischemic brain damage and diffuse brain swelling occur in severe cases of traumatic head injury. Ischemia decreases brain acetylcholine (ACh) levels and head trauma upregulates acetylcholinesterase (AChE) in experimental animal models. The present study determined whether a brain-selective AChE inhibitor, ENA713, given once, up to 2 h after closed head injury (CHI) could reduce the vasogenic edema and accelerate recovery from neurological deficits induced by the injury in rats. ENA713 1-5 mg/kg produced a dose-related inhibition of AChE ranging from 40-85% in the cortex and hippocampus. Doses of 1, 2 and 5 mg/kg, significantly reduced the motor and neurological deficits and speeded recovery, as indicated by measurements made 7 and 14 days after injury. The two larger doses were still effective when injected 1 or 2 h after CHI. The acceleration by ENA713 of recovery of motor function was independent of its reduction in body temperature and was prevented by the simultaneous injection of mecamylamine (2.5 mg/kg), but not by scopolamine (0.2 or 1 mg/kg). Edema in the contused hemisphere (24 h after injury) and disruption of the blood brain barrier (4 h after injury) were significantly reduced (about 50%) by doses of 2 and 5 mg/kg, but not by 1 mg/kg. The data support the hypothesis that ENA713 exerts a neuroprotective effect in brain injury by preventing the decrease in cholinergic activity in cerebral vessels and in neurones.

Induced hypothermia in intensive care medicine

Induced hypothermia as adjunctive therapy has been the subject of considerable research interest and debate for over fifty years. Recently the first prospective randomized controlled trials were undertaken in humans with severe traumatic brain injury, with supportive results. Another prospective controlled study of induced hypothermia in severe septic adult respiratory distress syndrome also suggested improved outcome. Other studies in patients with anoxic brain injury have been suggested following promising findings in animal models. There have been anecdotal reports of the use of induced hypothermia in a wide range of other neurological injuries. There are significant physiological changes during induced hypothermia, particularly affecting the cardiovascular system. In addition, hypokalaemia, prolonged clotting times and neutropenia may occur. The evidence that induced hypothermia may be hazardous is mostly drawn from the literature on accidental hypothermia occurring in trauma, or patients with sepsis. It is likely that further trials will be conducted and if benefit is confirmed, induced hypothermia may become more widely used in selected patients in the intensive care unit.