Showing papers by "Bruno Bissonnette published in 1999"

Early SjvO2 monitoring in patients with severe brain trauma.

Abstract: Objective: To investigate early cerebral variables after minimal resuscitation and to compare the adequacy of a cerebral perfusion pressure (CPP) guideline above 70 mmHg, with jugular bulb venous oxygen saturation (SjvO2) monitoring in a patient with traumatic brain injury (TBI). Design: Prospective, observational study. Setting: Anesthesiological intensive care unit. Patients: 27 TBI patients with a postresuscitation Glasgow Coma Scale score less than 8. Intervention: After initial resuscitation, cerebral monitoring was performed and CPP increased to 70 mmHg by an increase in mean arterial pressure (MAP) with volume expansion and vasopressors as needed. Measurements and results: MAP, intracranial pressure (ICP), CPP, and simultaneous arterial and venous blood gases were measured at baseline and after treatment. Before treatment, 37 % of patients had an SjvO2 below 55 %, and SjvO2 was significantly correlated with CPP (r = 0.73, p < 0.0001). After treatment, we observed a significant increase (p < 0,0001) in CPP (78 ± 10 vs 53 ± 15 mmHg), MAP (103 ± 10 vs 79 ± 9 mmHg) and SvjO2 (72 ± 7 vs 56 ± 12), without a significant change in ICP (25 ± 14 vs 25 ± 11 mmHg). Conclusion: The present study shows that early cerebral monitoring with SjvO2 is critical to assess cerebral ischemic risk and that MAP monitoring alone is not sensitive enough to determine the state of oxygenation of the brain. SjvO2 monitoring permits the early identification of patients with low CPP and high risk of cerebral ischemia. In emergency situations it can be used alone when ICP monitoring is contraindicated or not readily available. However, ICP monitoring gives complementary information necessary to adapt treatment.

Neuroleptanesthesia: current status.

Abstract: Purpose To review the current status and possible future of neuroleptanalgesia/anesthesia, techniques that may be nearly extinct.

The Impact of Systemic Vasoconstrictors on the Cerebral Circulation of Anesthetized Patients

Abstract: BackgroundThe effect of vasoconstrictors on intracerebral hemodynamics in anesthetized patients is controversial. The influence of phenylephrine and norepinephrine on the cerebral circulation was investigated in isoflurane- or propofol-anesthetized patients using transcranial Doppler ultrasonography

Deep hypothermia and rewarming alters glutamate levels and glycogen content in cultured astrocytes.

Abstract: BACKGROUND: Deep hypothermia has been associated with an increased incidence of postoperative neurologic dysfunction after cardiac surgery in children. Recent studies suggest an excitotoxic mechanism involving overstimulation of glutamate receptors. Extracellular glutamate uptake occurs primarily by astrocytes. Astrocytes also store glycogen, which may be used to sustain the energy-consuming glutamate uptake. Extracellular glutamate and glycogen content were studied during temperature changes mimicking cardiopulmonary bypass in vivo. METHODS: Primary cultures of cerebral cortical astrocytes were used in a specially designed incubator allowing continuous changes of temperature and ambient gas concentrations. The sequence of events was as follows: normothermia, rapid cooling (2.8 degrees C/min) followed by 60 min of deep hypothermia (15 degrees C), followed by rewarming (3.0 degrees C/min) and subsequent 5 h of mild hyperthermia (38.5 degrees C). Two different conditions of oxygenation were studied: (1) normoxia (25% O2, 70% N2, 5% CO2); or (2) hyperoxia (95% O2, 5% CO2). The extracellular glutamate concentrations and intracellular glycogen levels were measured at nine time points. RESULTS: One hundred sixty-two cultures were studied in four independent experiments. The extracellular concentration of glutamate in the normoxic group increased significantly from 35+/-10 nM/mg protein at baseline up to 100+/-15 nM/mg protein at the end of 5 h of mild hyperthermia (P < 0.05). In contrast, extracellular glutamate levels did not vary from control in the hyperoxic group. Glycogen levels decreased significantly from 260+/-85 nM/mg protein at baseline to < 25+/-5 nM/mg protein at the end of 5 h in the normoxic group (P < 0.05) but returned to control levels after rewarming in the hyperoxic group. No morphologic changes were observed in either group. CONCLUSION: The extracellular concentration of glutamate increases, whereas the intracellular glycogen content decreases when astrocytes are exposed to a sequence of deep hypothermia and rewarming. This effect of hypothermia is prevented when astrocytes are exposed to hyperoxic conditions.

Thermal regulation and mild intraoperative hypothermia.

Abstract: Homeothermic species such as birds and mammals require an almost constant internal body temperature to preserve normal physiological and metabolic function. When the internal temperature deviates significantly from normal, metabolic function deteriorates and death may result. The efficiency of the thermoregulatory system is highly affected by the administration of medication and by illnesses. Hypothermia may result, especially when these conditions are associated with exposure to a cold environment. Because such conditions exist during anaesthesia and surgery, the understanding of the physiology of the thermoregulatory system and the associated perianaesthetic thermal disturbances is essential to a proper intraoperative management. The purpose of this review is to provide clinicians with a better understanding of these principles, and also to elaborate on the most recent advances in this field, which should help to improve intraoperative anaesthetic temperature management.