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Biomedical subjects

B Bissonnette

Publications and source records attributed to B Bissonnette.

At least 19 recordsLinked to original sources
PubMed2000

Relationship between intracranial pressure, mild hypothermia and temperature-corrected PaCO2 in patients with traumatic brain injury.

OBJECTIVE: To study the effects of mild hypothermia and associated changes in temperature-corrected PaCO2 (cPaCO2) on intracranial pressure (ICP), mean velocity of the middle cerebral artery (Vm), and venous jugular saturation in O2 (SjvO2) in patients with severe traumatic brain injury (TBI). DESIGN: Prospective, observational study. SETTING: Intensive care unit. PATIENTS: Severe TBI patients mechanically ventilated, sedated and paralyzed. INTERVENTIONS: Twenty patients were subjected to four consecutive periods: (a) normocapnia-normothermia; (b) hypocapnia-normothermia, where hypocapnia was induced by an increase in minute volume; (c) hypocapnia-hypothermia, where hypocapnia was induced by hypothermia maintaining the ventilatory settings constant; (d) normocapnia-hypothermia, where normocapnia was achieved by a decrease in minute volume. MEASUREMENTS AND RESULTS: cPaCO2 was 41 +/- 8 mmHg in periods 1 and 4, and 31 +/- 7 mmHg in periods 2 and 3. Core temperature was 37.1 +/- 0.8 degrees C in periods 1 and 2, and 34.1 +/- 1.1 degrees C in periods 3 and 4. End-tidal CO2 and cPaCO2 values showed no difference between periods 1 and 4 and periods 2 and 3. ICP and Vm were dependent on cPaCO2 but independent of core temperature values. SjvO2 was related to cPaCO2 and was significantly higher during period 3 than during period 2 (P < 0.05). CONCLUSION: The decrease in ICP was similar when hypocapnia was induced by hyperventilation or as a result of hypothermia alone. The relationship between cPaCO2 and ICP might predict variations in ICP during changes in core temperature. Further studies are needed to confirm the cerebral metabolic effects of moderate hypothermia in TBI patients.

Adult↗
PubMed2000

[From the macroscopic lesion to cellular ischemia].

Traumatic brain injury (TBI) constitutes a major health and economic problem for developed countries, being one of the main causes of mortality and morbidity in children and young adults. Because of the immense importance and future consequences of TBI, the physician who sees a patient soon after brain injury must have a complete understanding of the pathophysiology and develop a practical knowledge of initial management of such patients. TBI may have intracranial and systemic effects that combine to give overall cerebral ischaemia. Injury to the nervous system is characterised by a stereotypic pattern, irrespective of the primary injury. The primary injury initiates a multitude of inflammatory cascades resulting in secondary brain injury, the effect of which is as important as the primary injury. This period of brain inflammation can last up to three weeks and renders the brain more susceptible to the effects of systemic insults such as hypotension, hypoxia and/or pyrexia. It has been shown in postmortem examination of patients dying from severe TBI that more than 90% had evidence of secondary ischaemic damage. The concept of 'cerebral protection' has been extended to encompass pretreatment of secondary injury. Preventing and treating cerebral ischaemia is the main goal of initial management of head-injured patients. Initial care focuses on achieving oxygenation, airway control and treatment of arterial hypotension.

Adult↗
PubMed2000

The effect of low concentrations of halothane on the cerebrovascular circulation in young children.

To determine the effect of halothane on cerebral blood flow velocity measured by transcranial Doppler, 23 healthy young children were studied during surgery. Anaesthesia was induced with thiopental, fentanyl and vecuronium, and maintained with halothane in 70% nitrous oxide in oxygen. A continuous epidural anaesthesia with 0. 25% bupivacaine was performed. End-tidal carbon dioxide pressure, temperature, heart rate and systolic blood pressure were kept constant. Three minimal alveolar concentrations (MAC; 0.5, 1.0 and 1. 5) of halothane were administered in stepwise increases. The cerebral blood flow velocity increased significantly at 1.0 (p < 0. 01) and 1.5 MAC (p < 0.001) compared with the value at 0.5 MAC. No further change in cerebral blood flow velocity was seen between 1.0 and 1.5 MAC. These data show that maximal changes in cerebral blood flow velocity are obtained at 1.0 MAC and that further increases in halothane concentration do not modify the cerebral circulation. It is suggested that young children differ from adults in that the maximal effect of halothane occurs at lower concentrations.

Anesthetics, Inhalation↗
PubMed2000

Potassium as a surrogate marker of debris in cell-salvaged blood.

UNLABELLED: Centrifuge-based cell salvage systems have decreased the use of homologous blood transfusions. Although the evidence is anecdotal, the risk associated with the use of salvaged erythrocytes seems related to cellular and chemical contaminants. We sought to determine if potassium can be a surrogate marker for cellular debris and to measure the residual heparin level. Four units of expired whole blood were heparinized and concentrated with a Sequestra 1000 (Medtronics), Parker, CO) cell salvage device. The potassium, free hemoglobin, leukocyte, and platelet counts were sampled after each 250-mL normal saline wash aliquot, to a total wash volume of 1500 mL, whereas the heparin samples were obtained at wash volumes 0 and 1000 mL. Potassium, leukocyte, and platelet concentrations at wash volumes 0 and 250 mL were significantly greater than at all other volumes (P < 0.001). After 500 mL of saline wash, the change in these values was not significant. The mean (+/- SD) heparin levels (units/mL) at wash volumes 0 and 1000 mL were 10.2 (+/-3.1) and 0.11 (+/-0.02), respectively (P < 0.007). The r(2) values for free hemoglobin, leukocytes, and platelets versus potassium were 0.006, 0.992, and 0.995, respectively. No convenient test has been validated as an indicator of salvaged erythrocyte cleanliness. This in vitro study suggests that residual potassium concentration seems to be a good indicator of quality after washing with a contemporary intraoperative salvage system. IMPLICATIONS: No convenient test has been validated as an indicator of salvaged erythrocyte cleanliness. This in vitro study suggests that residual potassium concentration seems to be a good indicator of quality after washing with a contemporary intraoperative salvage system.

Blood Platelets↗
PubMed2000

Cerebral hyperthermia in children after cardiopulmonary bypass.

BACKGROUND: Cerebral hyperthermia after hypothermic cardiopulmonary bypass has been poorly documented for adults and never in children. This study was designed to monitor brain temperature during and up to 6 h after cardiopulmonary bypass in infants and children. METHODS: Fifteen infants and children, between 3 months and 6 yr of age, were studied. A right retrograde jugular bulb catheter was used to measure the jugular venous bulb temperature (JVBT) during the procedure and the first 6 h in the critical care unit. The temperature of the blood from the bypass machine was measured at the aorta through the cannula using an indwelling temperature probe. All data were acquired every minute. RESULTS: The age of the patients ranged from 3 to 71 months (median, 15 months). The mean weight was 11.5 +/- 8.4 kg. The mean JVBT recorded at the end of cardiopulmonary bypass was 36.9 +/- 1.4 degrees C but reached 39.6 +/- 0.8 degrees C after six h (P < 0.01). The kinetics of brain rewarming was determined by the slope of the mean JVBT and corresponded to y +/- 0.006x + 37.21 (r2 = 0.97). The JVBT differed from the tympanic temperature after 200 min (P < 0.01) and the lower esophageal (P < 0.05) and rectal (P < 0.001) temperatures after 300 min. After 6 h, the tympanic, rectal, and lower esophageal temperatures were 37.8 +/- 0.9, 37.7 +/- 0.6, and 38.4 +/- 0.7 degrees C, respectively, whereas the JVBT was 39.6 +/- 0.8 degrees C (P < 0.001). However, the correlation coefficients between the JVBT and the tympanic, rectal, and esophageal temperatures were 0.98, 0. 85, and 0.97, respectively. No complications were recorded with placement of the jugular bulb catheter. CONCLUSIONS: Mean JVBT was significantly increased over the mean core temperature at all times from rewarming by cardiopulmonary bypass onward. Although the lower esophageal, rectal, and tympanic temperatures correlated well with JVBT, all three failed to reflect JVBT during recovery. This observation might help to elucidate factors involved in the functional and structural neurologic injury known to occur in pediatric patients.

Body Temperature↗
PubMed2000

Effects of neck position and head elevation on intracranial pressure in anaesthetized neurosurgical patients: preliminary results.

This study reports the collective effect of the positions of the operating table, head, and neck on intracranial pressure (ICP) of 15 adult patients scheduled for elective intracerebral surgery. Patients were anesthetized with propofol, fentanyl, and maintained with a propofol infusion and fentanyl. Intracranial pressure was recorded following 20 minutes of stabilization after induction at different table positions (neutral, 30 degrees head up, 30 degrees head down) with the patient's neck either 1) straight in the axis of the body, 2) flexed, or 3) extended, and in the five following head positions: a) head straight, b) head angled at 45 degrees to the right, c) head angled at 45 degrees to the left, d) head rotated to the right, or e) head rotated the left. For ethical reasons, only patients with ICP < or = 20 mm Hg were included. Intracranial pressure increased every time the head was in a nonneutral position. The most important and statistically significant increases in ICP were recorded when the table was in a 30 degree Trendelenburg position with the head straight or rotated to the right or left, or every time the head was flexed and rotated to the right or left-whatever the position of the table was. These observations suggest that patients with known compromised cerebral compliance would benefit from monitoring ICP during positioning, if the use of a lumbar drainage is planed to improve venous return, cerebral blood volume, ICP, and overall operating conditions.

Adult↗
PubMed1999

Neuroleptanesthesia: current status.

PURPOSE: To review the current status and possible future of neuroleptanalgesia/anesthesia, techniques that may be nearly extinct. SOURCE: Articles from 1966 to present were obtained from the Current Science and Medline databases. Search terms include neurolepananalgesia/anesthesia, conscious sedation, droperidol, benzodiazepines, propofol, ketamine, and opioids. Information and abstracts obtained from meetings on this topic helped complete the collection of information. PRINCIPAL FINDINGS: Droperidol/fentanyl may still be clinically indicated in the management of surgical seizure therapy for electrocorticography. However, the high incidence of post-operative sedation and restlessness discourage its use for other surgical or diagnostic procedures. Many surgical interventions, once thought ideally suited for neuroleptic agents, now meet better success with newer medications. The use of midazolam and/or propofol, in association with newer opioids, provides ideal anesthetic combinations. CONCLUSION: The advantages of newer anesthetic agents have redefined the clinical indications for neuroleptanesthesia. In routine modern anesthesia, anxiolysis, sedation, and/or analgesia is better provided, with quicker recovery, by the new pharmacokinetic and pharmacodynamic characteristics of recent medications than by the neuroleptic component of neuroleptanesthesia.

Adjuvants, Anesthesia↗
PubMed1999

Early SjvO2 monitoring in patients with severe brain trauma.

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.

Adolescent↗
PubMed1999

Midazolam premedication and thiopental induction of anaesthesia: interactions at multiple end-points.

We have studied the effects of midazolam premedication on multiple anaesthetic end-points (hypnotic, loss of verbal contact (LVC); motor, dropping an infusion flex or bag (DF); analgesic, loss of reaction to painful stimulation (LRP); and EEG, attainment of burst suppression (BUR)) during induction by slow thiopental infusion at a rate of 55 mg kg-1 h-1. Patients received midazolam 0.05 mg kg-1 i.v. (group TM, n = 12) or no midazolam (group T0, n = 13). ED50 and ED95 values and group medians for times and doses at the end-points were measured. Midazolam premedication reduced significantly thiopental ED50 and ED95 values at all end-points (exception for ED95 for BUR). Potentiation was greatest for the motor end-point (dropping the infusion bag (DF)) (ED95 +52%, ED50 +23%, median +39%), and smallest for painful stimulation (LRP) (median +18%; ED50 +13%). For LRP and DF, premedication was associated with significant, non-parallel increases in the slope of the thiopental dose-response curves, resulting in marked potency ratio changes from ED50 to ED95 (LRP +31%, DF +29%). There were no such increases for LVC or BUR. The interaction between midazolam and thiopental varied with the anaesthetic end-point and may also depend on the dose of thiopental. Our data suggest that the mechanism of interaction between midazolam premedication and thiopental was different for motor effects or analgesia (DF, LRP) compared with hypnotic effects or cortical depression (LVC, BUR), in agreement with the different central nervous system substrates underlying these distinct anaesthetic end-points.

Adult↗
PubMed1999

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

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.

Algorithms↗
PubMed1998

[Assessment of intubation time and conditions under the influence of rocuronium].

PURPOSE: To evaluate the tracheal intubating conditions when intubation time is determined by the onset time of the neuromuscular block either of the adductor pollicis (AP) or of the orbicularis oculi muscle (OO). METHODS: In this prospective, double blind, randomised study, 40 adults ASA I-II undergoing general anaesthesia with tracheal intubation were allocated to two groups (n = 20) according to the reference muscle (AP or OO) used to determine the appropriate intubation time. Induction of anaesthesia was achieved with 5-7 mg.kg-1 thiopentone, 1.5-2.5 micrograms.kg-1 fentanyl and 0.9 mg.kg-1 rocuronium (3 x ED95) for muscular relaxation. Supramaximal train of four stimulation of the ulnar and facial nerve every 10 sec was used to monitor the neuromuscular block. After visual loss of AP or OO contraction, tracheal intubation and quality of intubation assessment were performed by two independent anaesthetists. Data are expressed as mean and standard error of the mean (X +/- SEM). RESULTS: Curarisation time of the OO was shorter (110 +/- 4.9 sec) than that of the AP (144 +/- 5.5 sec; P < 0.0001). Intubation conditions were excellent in 95% and good in 5% of the patients in the AP group whereas in the OO group only 65% of the patients had excellent and 20% good intubation conditions (P < 0.05). Coughing was observed in 15% of patients in the OO group during tracheal intubation. CONCLUSION: Monitoring neuro-muscular activity of the AP using TOF to determine the appropriate tracheal intubation time and conditions in patients paralysed with rocurorium is more clinically relevant than monitoring the OO muscle.

Adult↗
PubMed1998

Cerebral physiology in paediatric cardiopulmonary bypass.

PURPOSE: To analyze studies of neurological injury after open-heart surgery in infants and children and to discuss the effects of cardiopulmonary bypass, hypothermia and deep hypothermic circulatory arrest on cerebral blood flow, cerebral metabolism and brain temperature. SOURCE: Articles were obtained from the databases, Current Science and Medline, from 1966 to present. Search terms include cardiopulmonary bypass (CPB), hypothermia, cerebral blood flow (CBF), cerebral metabolism and brain temperature. Information and abstracts obtained from meetings on the topic of brain and cardiac surgery helped complete the collection of information. PRINCIPAL FINDINGS: In adults the incidence of neurological morbidity is between 7 to 87% with stroke in about 2-5%, whereas the incidence of neurological morbidity increases to 30% in infants and children undergoing cardiopulmonary bypass. Besides the medical condition of the patient, postoperative cerebral dysfunction and neuronal ischaemia associated with cardiac surgery in infants and small children are a combination of intraoperative factors. Deep hypothermic circulatory arrest impairs CBF and cerebral metabolism even after termination of CPB. Inadequate and/or non-homogenous cooling of the brain before circulatory arrest, as well as excessive rewarming of the brain during reperfusion are also major contributory factors. CONCLUSION: Newer strategies, including the use of low-flow CPB, pulsatile CPB, pH-stat acid-base management and a cold reperfusion, are being explored to ensure better cerebral protection. Advances in monitoring technology and better understanding of the relationship of cerebral blood flow and metabolism during the different modalities of cardiopulmonary bypass management will help in the medical and anaesthetic development of strategies to improve neurological and developmental outcomes.

Acid-Base Equilibrium↗
PubMed1998

Bupivacaine 0.125% produces motor block and weakness with fentanyl epidural analgesia in children.

PURPOSE: Epidural infusions of fentanyl (2 micrograms.ml-1) alone or combined with bupivacaine 0.125% were compared for perioperative analgesia, motor block and other side-effects in children who underwent urological surgery. METHODS: In a prospective, double-blind study, 42 children, ASA I-II, 1-16 yr, were randomly allocated to receive either epidural F (fentanyl bolus 2 micrograms.kg-1 in 0.5 ml.kg-1 saline followed by 2 micrograms.ml-1 fentanyl infusion) or epidural F-B (fentanyl bolus 2 micrograms.kg-1 in 0.5 ml.kg-1 bupivacaine 0.25% followed by 2 micrograms.ml-1 fentanyl infusion in bupivacaine 0.125%) after induction of general anaesthesia. Adequacy of analgesia, lower limb motor block and side-effects were assessed four hourly postoperatively. RESULTS: Both infusion regimens provided excellent analgesia (median objective pain scores = 0). Epidural infusion rates were similar in the F (0.29 +/- 0.07 ml.kg-1.hr-1) and F-B (0.26 +/- 0.05 ml.kg-1.hr-1) groups. Three children in the F group and all children in the F-B group developed lower limb weakness. (P < 0.05) Bromage scores were different in the F group (median 0, range 0-0.66) compared with the F-B group (median 0.33, range 0-1) (P < 0.001). Other side-effects did not differ. CONCLUSION: Postoperative epidural fentanyl infusion provides equipotent analgesia to administration of a solution including both fentanyl and bupivacaine 0.125% and causes less lower limb weakness. No reduction in the fentanyl requirement resulted from the addition of bupivacaine 0.125%.

Adolescent↗
PubMed1998

Methods for warming intravenous fluid in small volumes.

PURPOSE: Laboratory experiments were performed to determine warming rates of albumin 5% at room temperature and human packed red blood cells (PRBCs) at 4 degrees C in small volumes. Four methods used in clinical practice to warm volumes appropriate for neonates were studied. METHODS: The fluids were warmed either by infusion through a fluid warmer with temperature-controlled coaxial tubing (Group I), immersion in a water bath at 37 degrees C (Group II), placing pre-filled syringes (10 and 20 ml) between a circulating water mattress and a forced-air warming blanket (Group III), or placing the same syringes between the water mattress and cotton towels (Group IV). The temperature of each fluid was recorded for the next 60 sec after the bolus injection in group I and every five minutes for a total of 30 min for the other groups. The time constant of warming for each group was calculated. The time constant and the temperature reached after the warming period were compared among groups. RESULTS: In group I 20 ml room temperature albumin 5% or 4 degrees C blood reached temperatures of 36.9 +/- 1.5 degrees C and 34.5 +/- 2.3 degrees C within 60 sec, respectively. This was faster than all other techniques used (P < 0.001). The time constants measured for the albumin and the PRBCs were 0.23 +/- 0.1 and 0.20 +/- 0.05 minutes respectively. After 15 min albumin and PRBCs in group II reached 35.5 +/- 0.4 degrees C and 33.4 +/- 0.3 degrees C, in group III reached 33.7 +/- 1.0 C and 32.8 +/- 1.7 C, and in group IV reached 29.5 +/- 0.1 degrees C and 23.3 +/- 0.8 degrees C after 15 min respectively. CONCLUSION: Warming of intravenous fluids in small volumes is accomplished most rapidly using a fluid warmer with temperature-controlled coaxial tubing and occurs more slowly in syringes, bottles, or bags exposed to various environmental conditions.

Albumins↗
PubMed1998

Closure of persistently patent arterial duct and its impact on cerebral circulatory haemodynamics in children.

PURPOSE: Closure of a patent arterial duct (PDA) is suggested as a risk factor associated with intraventricular haemorrhage and/or cerebral ischemia in neonates. This study evaluate the effects of transcatheter closure of a patent arterial duct in children on cerebral blood flow velocity. METHODS: Twelve children, aged from one to eight years were enrolled. Anaesthesia induction consisted of thiopentone, fentanyl and diazepam. Tracheal intubation was facilitated with vecuronium. Anaesthesia was maintained with N2O 70% in O2 and a PaCO2 between 35 to 40 mmHg. No cerebral vasoactive agents were used. Mean arterial pressure (MAP), central venous pressure (CVP), heart rate were continuously recorded. Systolic (Vs) and diastolic (Vd) cerebral blood flow velocity (CBFV) were recorded. Cerebral perfusion pressure (CPP) was calculated. The mean CBFV, the systolic-mean ratio and the cerebral blood volume were estimated from the area under the velocity-time curve (AUC) before PDA closure, immediately after and for 10 min following occlusion. RESULTS: The mean (+/- SD) age and weight were 30 +/- 22 mo and 13 +/- 5 kg, respectively. Continuous recording during duct closure showed an abrupt increase in Vd (P < 0.05) whereas Vs remained constant. The AUC increased after closure and persisted for 10 min (P < 0.05). CONCLUSION: This study confirms that closure of a PDA leads to acute changes in intracerebral diastolic flow and volume. This observation gives weight to mechanisms involved in IVH in smaller infants after arterial surgical duct closure. The anaesthetic technique used for arterial duct closure in these procedure could influence these observations.

Area Under Curve↗
PubMed1998

-The effect of ondansetron on intracranial pressure and cerebral perfusion pressure in neurosurgical patients-.

OBJECTIVE: To determine the effect of ondansetron on intracranial pressure (ICP), mean arterial pressure (MAP) and cerebral perfusion pressure (CPP). STUDY DESIGN: Prospective, comparative, randomized double-blind study. PATIENTS: Twenty-six patients undergoing intracranial surgery. METHOD: Induction was obtained with propofol (1-2.5 mg.kg-1), fentanyl (1.5 micrograms.kg-1) and pancuronium (0.1 mg.kg-1), and maintenance was achieved with propofol and fentanyl. Intermittent positive pressure ventilation was used to ensure mild hypocapnia at 35 +/- 2 mmHg. Positioning of the patient was followed by 15 minutes steady-state. Patient received thereafter either 8 mg ondansetron or a placebo intravenously. The ICP was measured using a lumbar malleable spinal needle. CPP was calculated using the formula CCP = MAP-ICP. All variables were measured every minute for 15 minutes. RESULTS: The ICP, MAP and CPP did not differ between the two groups. There were no differences in the highest ICP values in patients receiving either ondansetron or placebo (11 +/- 5 versus 9 +/- 5, mean +/- SD), respectively. CONCLUSION: Intravenous administration of 8 mg ondansetron affects neither cerebral hemodynamics nor ICP.

Adolescent↗
PubMed1998

Recovery characteristics of propofol anaesthesia, with and without nitrous oxide: a comparison with halothane/nitrous oxide anaesthesia in children.

Few studies have examined whether nitrous oxide influences the recovery characteristics of propofol anaesthesia. The present study examined the effect of nitrous oxide on the recovery characteristics of propofol anaesthesia, and compared these data with those for halothane/nitrous oxide anaesthesia. Sixty children aged 3-12 years were assigned at random to receive one of three maintenance regimens: propofol with or without nitrous oxide (70%) or halothane/nitrous oxide (70%). During propofol/N2O anaesthesia, the infusion rate of propofol (180 +/- 39 micrograms.kg-1.min-1) required to maintain the mean arterial pressure and heart rate within 20% of the baseline values was significantly less than that during propofol/O2 (220 +/- 37 micrograms.kg-1.min-1; P < 0.005). The time from discontinuation of anaesthesia to eye-opening (11 +/- 6 min), to response to commands (12 +/- 6 min), and to return of full wakefulness (21 +/- 10 min) after propofol/N2O were similar to those after propofol/O2, but significantly less (by approximately 30%) than those after halothane (P < 0.05). The overall incidence of emesis after propofol/N2O (53%) was greater than that after propofol/O2 (17%, P < 0.05) and comparable to that after halothane/N2O (58%). These data suggest that N2O has little effect on the rate of recovery after propofol, but significantly increases the incidence of postoperative emesis, thereby attenuating one of the main attributes of propofol anaesthesia.

Anesthesia Recovery Period↗