Outcome in severe Reye syndrome with early pentobarbital coma and hypothermia

Role of barbiturate coma in the management of focally induced, severe cerebral edema in children

Barbiturates are widely used in the management of high intracranial pressure (ICP) caused by diffuse brain swelling. The cardiovascular, renal, and immunological side effects of these drugs limit them to last-line therapy. There are few published data regarding the role of barbiturates in focal brain lesions causing refractory elevated ICP and intraoperative brain swelling in the pediatric population. The authors here present 3 cases of nontraumatic, focally induced, refractory intracranial hypertension due to 2 tumors and 1 arteriovenous malformation, in which barbiturate therapy was used successfully to control elevated ICP. They focus on cardiovascular, renal, and immune function during the course of pentobarbital therapy. They also discuss the role of pentobarbital-induced hypothermia. From this short case series, they demonstrate that barbiturates in conjunction with standard medical therapy can be used to safely reduce postoperative refractory intracranial hypertension and intraoperative brain swelling in children with focal brain lesions.

Therapeutic hypothermia: applications in pediatric cardiac arrest

There is a rich history for the use of therapeutic hypothermia after cardiac arrest in neonatology and pediatrics. Laboratory reports date back to 1824 in experimental perinatal asphyxia. Similarly, clinical reports in pediatric cold water drowning victims represented key initiating work in the field. The application of therapeutic hypothermia in pediatric drowning victims represented some of the seminal clinical use of this modality in modern neurointensive care. Uncontrolled application (too deep and too long) and unique facets of asphyxial cardiac arrest in children (a very difficult insult to affect any benefit) likely combined to result in abandonment of therapeutic hypothermia in the mid to late 1980s. Important studies in perinatal medicine have built upon the landmark clinical trials in adults, and are once again bringing therapeutic hypothermia into standard care for pediatrics. Although more work is needed, particularly in the use of mild therapeutic hypothermia in children, there is a strong possibility that this important therapy will ultimately have broad applications after cardiac arrest and central nervous system (CNS) insults in the pediatric arena.

Characteristics of infection and leukocyte count in severely head-injured patients treated with mild hypothermia

OBJECTIVE

This study was designed to characterize the infectious complications and kinetics of leukocyte count in severely head-injured patients treated with mild hypothermia.

PATIENTS AND METHODS

We retrospectively analyzed the incidence and severity of infectious complications as well as daily changes in leukocyte count in 41 severely head-injured patients treated with mild hypothermia (group H). They were retrospectively compared with 25 severely head-injured patients treated with high-dose barbiturates (group B) and to 25 other severely head-injured patients treated with no barbiturates (group N).

RESULTS

Initial intracranial pressure was significantly higher in group H than in the other groups. No significant differences existed in the incidence of pneumonia or meningitis among the three groups, whereas the incidence of bacteremia was significantly higher in group H than in the other two groups. Pneumonia was significantly more severe in group H than in the other groups. In six patients of group H, pneumonia spread fulminantly to become life threatening. Daily changes in total leukocyte count showed the same pattern, consisting of a peak, a nadir, and a second peak in all groups. Total leukocyte count was, however, significantly lower during the first 2 weeks in group H than in the other two groups. Lymphocyte and neutrophil counts were also lower in group H.

CONCLUSION

Infectious complications were more severe and leukocyte counts were lower in patients treated with mild hypothermia, who also had the highest initial intracranial pressures, than in patients treated with conventional therapies. Measures against increased susceptibility to infection and leukocyte suppression should be explored.

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.

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.

Effect of mild hypothermia on uncontrollable intracranial hypertension after severe head injury

Recent experimental studies have demonstrated that mild hypothermia at about 34 degrees C can be effective in the control of intracranial hypertension. A randomized controlled study of mild hypothermia was carried out in 33 severely head-injured patients. All patients fulfilled the following criteria: 1) persistent intracranial pressure (ICP) greater than 20 mm Hg despite fluid restriction, hyperventilation, and high-dose barbiturate therapy; 2) an ICP lower than the mean arterial blood pressure; and 3) a Glasgow Coma Scale score of 8 or less. The patients were divided into two groups: one received mild hypothermia (16 patients) and one served as a control group (17 patients). Mild hypothermia significantly reduced the ICP and increased the cerebral perfusion pressure. Eight patients (50%) in the hypothermia group and three (18%) in the control group survived (p < 0.05), while five (31%) in the hypothermia group and 12 (71%) in the control group died of uncontrollable intracranial hypertension (p < 0.05). In five patients in the hypothermia group, cerebral blood flow was measured by the hydrogen clearance method and arteriojugular venous oxygen difference was evaluated before and during mild hypothermia. Mild hypothermia significantly decreased the cerebral blood flow, arteriojugular venous oxygen difference, and cerebral metabolic rate of oxygen (p < 0.01). The results of this preliminary investigation suggest that mild hypothermia is a safe and effective method to control traumatic intracranial hypertension and to improve mortality and morbidity rates.

Management of intracranial hypertension

Intracranial hypertension is the final common denominator of morbidity and mortality for diverse neurologic problems, and its proper treatment requires the heuristic application of the available therapeutic alternatives when the clinical situation and patient's prognosis warrants treatment. The initial therapeutic focus for ICP reduction should be control of factors that may aggravate intracranial hypertension such as inappropriate head and body position, elevated body temperature, pain, noxious stimuli, elevated airway pressure, elevated blood pressure, seizures, and hypotonic intravenous fluids. The appropriate conventional therapies (e.g., hyperventilation, osmotic agents, sedatives, barbiturates, and cerebrospinal fluid removal) should be selected based on the details of each individual case. Surgical removal of intracranial mass lesions may be indicated in some circumstances, particularly for intractable intracranial hypertension and progressive, severe brain tissue shifts.

Effects of temperature on phagocytosis of human and calf polymorphonuclear leukocytes

The in vitro effect of temperature on the phagocytic function of human and calf polymorphonuclear leukocytes (PMN) was studied. To observe the PMN phagocytic function (PPF) at various temperatures, PMN from healthy human and calf donors were incubated with serum-opsonized fluorescent latex particles (diameter 1.66 microns) at 25, 37, 40, 42, 44, or 46 degrees C for 1 h and then observed for their phagocytic activity by fluorescent microscopy. At 25, 40, and 42 degrees C, human PPF was not significantly different from that at 37 degrees C (87%, 89%, and 80% vs. 93%). At 44 degrees C, PPF was noticeably depressed (19%, p < 0.05) when compared to that at 37 degrees C. Next, to determine the critical temperature and duration of exposure that would irreversibly damage PPF, PMN were preincubated at 42, 44, or 46 degrees C for 5-30 min before being subjected to a standard phagocytosis assay at 37 degrees C. The human PPF was significantly depressed after 30 min at 44 degrees C (33%, p < 0.05) or 10 min at 46 degrees C (30%, p < 0.05). In conclusion, neither human nor calf PPF was significantly altered at and below 42 degrees C. In contrast, the PPF was irreversibly and time-dependently damaged when incubated at and above 44 degrees C.

Effect of hypothermia and cardiac arrest on outcome of near-drowning accidents in children

We conducted a retrospective review of 55 near-drowning victims (mean age 4.75 years) admitted to the intensive care unit during a 5-year period, to determine the factors that may influence survival both before and after hospital admission. All patients who remained comatose after resuscitation received ventilation for an initial 24 hour period, after which an assessment of central nervous system injury was made. Intracranial pressure was not monitored, and barbiturate therapy was used only for seizure control. Thirty-seven children survived and 18 died; five survivors had profound neurologic damage resulting in a persistent vegetative state: the remaining 32 (58%) survived intact. The major factors that separated intact survivors from those who died and from survivors in a persistent vegetative state were the presence of a detectable heartbeat and hypothermia (less than 33 degrees C) on examination in the emergency department. Thirteen patients with absent vital signs and a temperature of greater than 33 degrees C either died or survived in a persistent vegetative state. Fourteen patients had a combination of absent vital signs and hypothermia and were resuscitated; eight died, two survived in a persistent vegetative state, and four survived intact. All intact survivors had been submerged in cold water for prolonged periods, and all underwent prolonged cardiopulmonary resuscitation. All patients with a detectable pulse, regardless of temperature, survived without neurologic sequelae. The 58% intact survival rate in this series compares favorably with the 50% we reported previously when high-dose barbiturate therapy and hypothermia were used to control intracranial pressure; at the same time, the number of survivors with a persistent vegetative state has been reduced by 50%. We conclude that prolonged in-hospital resuscitation and aggressive treatment of near-drowning victims who initially have absence of vital signs and are not hypothermic either results in eventual death or increases the number of survivors with a persistent vegetative state.

Surgical hypothermia

Induced hypothermia is an interesting and useful adjunct to therapy in many areas of surgery and medicine. To paraphrase Professor Swan (1973), clinical hypothermia 'has a past and some promise for the future'.

Reye syndrome

Reye syndrome has emerged as the quintessential example of an acute metabolic encephalopathy with an annual incidence ranging from 0.3 to 6.0 cases per 100,000 children. The general management has become standardized, and the mortality has declined to approximately 10 per cent. The role of aspirin in the etiopathogenesis remains controversial.

Neutrophil migration in vitro and in vivo during hypothermia

The effect of hypothermia on pig leukocyte migration in vitro and in vivo was studied. Neutrophil chemotaxis in vitro under agarose was significantly impaired at 29 degrees C (2.7 +/- 0.6 [mean +/- standard error]; 37 degrees C, 7.1 +/- 1.1). Leukocytes isolated from hypothermic pigs and tested at 37 degrees C migrated normally (7.8 +/- 0.6). Neutrophil and monocyte migration in vivo was markedly reduced at 29 degrees C. Reduced inflammatory responses may contribute to increased infections during hypothermia.

Neutrophil circulation and release from bone marrow during hypothermia

The effect of hypothermia on neutrophil circulation and release from bone marrow has been studied. Pigs were anesthetized and maintained at 37 degrees C or surface cooled to 29 degrees C over 60 min. As the core temperature was reduced to 29 degrees C, the number of circulating neutrophils (X 10(9) per liter) fell from 6.0 +/- 0.6 to 2.3 +/- 0.3 by 60 min. No significant change in the number of circulating mature or immature neutrophils was observed over the 4 h of observation at 29 degrees C. Neutrophil demargination after administration of intravenous catecholamines was similar at 37 and 29 degrees C. Steroid stimulation of bone marrow to release neutrophils was markedly impaired at 29 degrees C. Circulating mature neutrophils in normothermic pigs increased from 5.6 +/- 1.2 to 10.4 +/- 1.2 by 120 min after administration of intravenous hydrocortisone sodium succinate. Circulating immature neutrophils increased from 1.7 +/- 0.3 to 5.3 +/- 0.4. At 29 degrees C, no significant changes in the number of circulating mature or immature neutrophils occurred. Endotoxin also failed to stimulate neutrophil release from the bone marrow. Furthermore, a marked neutropenia occurred in hypothermic pigs after intravenous endotoxin, which persisted for the 3 h of observation. Neutrophil circulation and release from bone marrow are compromised by hypothermia, which may increase the risk for bacterial infection.

Intracranial pressure monitoring as a guide to prognosis in the nearly drowned, severely comatose child

During a 34-month-period, 55 nearly drowned, comatose children who were admitted to our pediatric intensive care unit were divided into C1 (decorticate), C2 (decerebrate), and C3 (flaccid) subgroups. Patients in subgroup C3 were selected for intracranial pressure (ICP) measurements by the subarachnoid bolt, and were reclassified according to clinical outcome into recovered (group A), fatality (group B), and brain damaged (group C) categories. Six children (29%) had complete recovery, 10 died (48%), and five (23%) demonstrated residual brain damage. There was a highly significant difference between the ICP in group A and group B (P less than 0.001), and between group B and group C (P less than 0.001). Both group A and group C had highly significant differences in mean cerebral perfusion pressure (CPP) values compared with group B (P less than 0.001). There were no significant differences in ICP or CPP between groups A and C. Finally, using a combination of ICP and CPP, we found that ICP less than or equal to 20 mm Hg and CPP greater than or equal to 50 mm Hg were associated with survival in 11 of 12 patients (92%), whereas ICP greater than 20 mm Hg and CPP less than 50 mm Hg were associated with death in seven patients cases (100%). The two other patients who died had either CPP less than 50 mm Hg or ICP greater than 20 mm Hg, but not both. We find that intracranial pressure monitoring is a safe, useful tool in predicting death or survival, but not residual brain damage, in the nearly drowned, severely comatose child.