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Biomedical subjects

B Bissonnette

Publications and source records attributed to B Bissonnette.

At least 19 recordsLinked to original sources
PubMed1997

Heart rate and cardiac output after atropine in anaesthetised infants and children.

PURPOSE: Heart rate is considered to be a major determinant of cardiac output in infants and small children but the relationships between age, heart rate and cardiac output in humans have never been clearly established. This study was designed to determine the change in cardiac output following atropine iv to anaesthetised infants and small children. METHODS: Following Institutional Ethics Committee approval and written-informed consent, 20 ASA I or II unpremedicated patients aged from 1 to 36 mo were studied. Anaesthesia was induced with 5 mg.kg-1 thiopentone, 2 micrograms.kg-1 fentanyl and maintained with halothane 0.5% in nitrous oxide 66% in oxygen. Vecuronium 0.1 mg.kg-1 was used to provide muscular relaxation. Cardiac output was measured by non-invasive transthoracic blind continuous-wave Doppler echocardiography before and after the administration of 0.02 mg.kg-1 atropine iv. RESULTS: Atropine increased both heart rate and cardiac index by 31.1 +/- 12.8% and 29.4 +/- 17.3% respectively (P < 0.05). The cardiac index before atropine was 5.1 +/- 1.2 L.min-1.m-2 and the increase after atropine varied widely from 1.4 to 52.1%. Although atropine did not alter the overall stroke index the recorded changes ranged from -20.8 to +18.0%. There was no association between age and either cardiac index or % change in cardiac index after atropine. However, there was a positive but weak correlation between percentage change in heart rate and cardiac output (r2 = 0.46). CONCLUSION: Atropine causes a variable increase in cardiac output in infants and children aged between 1 and 36 mo. The change in cardiac output, considering the limits of the transthoracic echocardiography methodology, suggests that this is related to the increase in heart rate but is not dependent of age.

Anesthesia↗
PubMed1996

[Hypertonic solutions and intracranial pressure].

The properties of the endothelium differ between the brain and the remainder of the body. In most non-CNS tissues the size of the junctions between endothelial cells averages 65 A. Proteins do not cross these gaps, while sodium does. In the brain, the junction size is only 7 A, which is too small to allow crossing by sodium. Investigations with changes in osmotic and oncotic pressure have demonstrated that: (1) reducing osmolality results in edema formation in all tissues including normal brain; (2) a decrease in oncotic pressure is only associated with peripheral edema but not in the brain; (3) in case of brain injury, a decrease in osmolality elicits edema in the part of brain which remained normal; (4) similarly, a decrease in oncotic pressure does not cause an increase in brain edema in the injured part of the brain. The determinant factor of water exchange in the brain is mediated through the osmolality and not the oncotic pressure. The use of hypertonic solutions (Ringer lactate or NaCl) for intravascular fluid resuscitation of patients suffering from hypovolemic head trauma has gained popularity. A research survey in regard with this observation can be summarized as follows: NaCl 7.5% (2400 mOsm/l) is becoming the most popular hypertonic solution because of its favorable systemic and cerebral effects. It improves myocardial contractility, precapillary dilatation, and reactive venoconstriction, and it has a plasmatic expansion factor of 3.8. In regard to the brain tissue, it improves the PO2 and the cerebral blood flow (CBF) as a result of decreasing cerebrovascular resistance. Finally, it reduces the cortical water content of intact blood-brain barrier area. The overall consequence is reduction of intracranial pressure (ICP). Although the homeostasis of the cerebral intracellular compartment remains unknown, it is possible that brain cells are able to resist important osmolar overload. NaCl 7.5%/dextran 70.6% is clinically at this moment the most studied hypertonic/hyperoncotic agent in prehospital emergencies. Its effects on cerebral homeostasis are identical to NaCl 7.5%. However, the addition of a colloid agent has the advantage of prolonging the systemic effects without affecting the brain. The plasmatic expansion factor is 4.5, which is slightly superior to NaCl 7.5%. Mannitol improves CBF by maintaining autoregulation as a result of changes in viscosity and reactive cerebrovascular constriction. It generates an osmotic gradient which reduces the cerebral volume and subsequently the ICP. In the presence of a cryogenic cerebral lesion, its reductive effects on brain water are superior to the hypertonic/hyperoncotic solution. Because mannitol has less spectacular systemic responses than the other solutions, it is not indicated for resuscitation following hemorrhagic shock. In conclusion, it is important to note that hypotension and hypoxemia represent the determinant factors of secondary cerebral insults. Therefore, in the presence of patients with head injury and especially hemorrhagic shock, it is essential to ensure a cerebral perfusion pressure (CPP) of > 80 mm Hg. Hypertonic solutions have gained popularity in these clinical situations because of their combined effects on ICP, mean arterial pressure (MAP) and CPP. However, the therapeutic approach to polytraumatized patients with small intravascular volume (4-6 ml/kg) of hypertonic solutions should not be a substitute for the usual volemic resuscitation technique. The clinical indication for these solutions should be limited to the initial resuscitation maneuvers in traumatized patients. Prolonged use of hypertonic solutions for the purpose of intravascular resuscitation would only contribute to increasing the side effects and eventually counteract the initial beneficial advantages.

Blood Pressure↗
PubMed1996

[Peroperative risks in cerebral aneurysm surgery].

The perioperative complications associated with cerebral aneurysm surgery require a specific anaesthetic management. Four major perioperative accidents are discussed in this review. The anaesthetic and surgical management in case of rebleeding subsequent to the re-rupture of the aneurysm is mainly prophylactic. It includes haemodynamic stability assurance, maintenance of mean arterial pressure (MAP) between 80-90 mmHg during stimulation of the patient such as endotracheal intubation, application of the skull-pin head-holder, incision, and craniotomy. The aneurysmal transmural pressure should be adequately maintained by avoiding an aggressive decrease of intracranial pressure. Once the skull is open, the brain must be kept slack in order to decrease pressure under the retractors and avoid the risks of stretching and tearing of the adjacent vessels. If, despite these precautions, the aneurysm ruptures again. MAP should be decreased to 60 mmHg and the brain rendered more slack, in order to allow direct clipping of the aneurysm, or temporary clipping of the adjacent vessels. The optimal agents in this situation are isoflurane (which decreases CMRO2), intravenous anaesthetic agents (inspite their negative inotropic effect, they may potentially protect the brain) and sodium nitroprusside. Vasospasm occurs usually between the 3rd and the 7th day after subarachnoid haemorrhage. It may be seen peroperatively. The optimal treatment, as well as prophylaxis, is moderate controlled hypertension (MAP > 100 mmHg), associated with hypervolaemia and haemodilution, the so-called triple H therapy, with strict control of the filling pressures. Other beneficial therapies are calcium antagonists (nimodipine and nicardipine), the removal of the blood accumulated around the brain and in the cisternae, and possibly local administration of papaverine. Abrupt MAP increases are controlled in order to maintain adequate aneurysmal transmural pressure. Beta-blockers, local anaesthetics administered locally or intravenously, a carefully titrated level of anaesthesia, a maintained volaemia play a protective role. Cerebral oedema is sometimes already present at the opening of the skull or may arise later, due to a high pressure under the retractors, to the surgical manipulations of the brain or to brain ischaemia subsequent to temporary clipping. Its treatment is aggressive, with intravenous agents, mannitol, deep hypocapnia and/or lumbar drainage. Prophylaxis, according to the "brain homeostasis concept", is the preferred method to avoid these four peroperative accidents. It includes normal blood volume, normoglycaemia, moderate hypocapnia, normotension, soft manipulation of the brain and optimal brain relaxation.

Anesthesia, General↗
PubMed1996

[Enhancement of cardiac performance for prevention and treatment of delayed cerebral ischemia caused by vasospasm].

Following subarachnoid haemorrhage, delayed cerebral ischaemia from cerebral vasospasm remains the most important cause of mortality and morbidity in patients with surgically secured aneurysms. Therapy with haemodilution, hypertension and volume expansion has been recommended to prevent and treat delayed cerebral ischaemia in these patients on the basis of uncontrolled clinical series (level of evidence III to V, grade C recommendation). Despite the lack of controlled studies, the maintenance of a cardiac index > 3.5 L.min-1.m-2 and a systolic arterial pressure between 120 and 150 mmHg before clipping and 160 to 200 mmHg thereafter is recommended as a prophylactic or therapeutic measure for vasospasm. Close monitoring of neurological and cardiorespiratory status is important to avoid neurologic and systemic complications.

Cerebrovascular Circulation↗
PubMed1996

[Intubation conditions: importance of the rate of repetition of the train-of-four].

OBJECTIVES: To assess that neuromuscular relaxation onset of the adductor pollicis (AP) is related to neuromuscular stimulation rate. To assess that train-of-four (TOF) at 0.05 Hz is a more accurate indicator of optimal tracheal intubation time and conditions, than TOF at 0.08 Hz. STUDY DESIGN: Prospective, comparative, randomized double-blind study. PATIENTS: Forty adults, physical class ASA 1 or 2, undergoing general anaesthesia with tracheal intubation were allocated to two groups (n = 20) according to the sequence of stimulation of the AP: either TOF at 0.05 Hz (test group) or TOF at 0.08 Hz (control group). METHODS: Induction of anaesthesia was achieved with thiopentone, fentanyl and vecuronium (0.1 mg.kg-1). Neuromuscular monitoring was obtained with force displacement transducers attached to each AP. Tracheal intubation was performed once AP muscular response obtained with TOF at 0.05 Hz for test group and TOF at 0.08 Hz for control group was abolished. Results are expressed as mean +/- SEM. Fisher exact test was used for intubation conditions comparison. Curarization time between groups was compared with unpaired Student's t test (P < 0.05 accepted). RESULTS: TOF with 0.05 Hz stimulation significantly increased curarization time: 217 +/- 7 versus 162 +/- 6 s (P < 0.001). Intubation conditions were excellent in 95% and good in 5% of patients in the study group, compared to 15 and 40% in the control group, respectively (P < 0.01) in 45% of the control group patients coughing at intubation occurred. CONCLUSION: Low stimulation rate (TOF at 0.05 Hz) of AP is a reliable technique to determine the appropriate intubation time for patients paralyzed with vecuronium.

Humans↗
PubMed1996

Dimenhydrinate decreases vomiting after strabismus surgery in children.

Dimenhydrinate, an H1-receptor antagonist, has been used to both prevent and treat postoperative vomiting (POV) in children for several decades. However, its effectiveness for POV after strabismus surgery remains anecdotal. This study was designed to determine the effectiveness and side effects of dimenhydrinate for the prevention of POV in children after strabismus surgery. Eighty ASA physical status I or II children, ages 1-12 yr inclusive, who were undergoing strabismus surgery, were prospectively and randomly allocated to receive either dimenhydrinate 0.5 mg/kg intravenously (n = 40) or placebo (n = 40) at induction of anesthesia. The incidence of POV and the times to arousal (and discharge from the recovery room and hospital) were recorded postoperatively in a double blinded manner. For 24 h after discharge from the hospital, all emetic episodes and medications given were recorded by the parents. Demographic data did not differ between the groups. Children who received dimenhydrinate had significantly less POV both inhospital (10%) and overall (30%) than those who received placebo (in-hospital 38%, P < 0.008; overall 65%, P < 0.003). The times to arousal and discharge from the hospital did not differ between the two groups. Dimenhydrinate (0.5 mg/kg) is an effective, safe, and inexpensive antiemetic in children undergoing strabismus surgery. It significantly reduces the incidence of vomiting for 24 h postoperatively and is not associated with prolonged sedation or other adverse effects.

Antiemetics↗
PubMed1996

Enflurane decreases the threshold for vasoconstriction more than isoflurane or halothane.

Intraoperative hypothermia results largely from anesthetic-induced inhibition of tonic thermoregulatory vasoconstriction. Sufficient hypothermia, however, triggers peripheral vasoconstriction, which usually prevents further decrease in core temperature. The thermoregulatory effects of all volatile anesthetics have been tested in adults and/or children, but different anesthetics have not been directly compared. We therefore evaluated thermoregulatory responses during enflurane, isoflurane, and halothane administration. Anesthesia was maintained with 1 minimum alveolar anesthetic concentration (MAC) of halothane, isoflurane, or enflurane in 27 patients undergoing intraabdominal surgery. Patients were maintained normovolemic and normocapnic but were allowed to cool passively. A forearm minus fingertip, skin-temperature gradient of 4 degrees C identified significant vasoconstriction; the core temperature triggering vasoconstriction identified the threshold. Morphometric characteristics, initial core temperatures, ambient operating room temperatures, blood pressures, and anesthetic potencies were similar in each group. All eight patients given halothane vasoconstricted at a core temperature of 35.5 +/- 0.6 degrees C. Eight of the patients given isoflurane vasoconstricted at a core temperature of 35.2 +/- 0.5 degrees C. However, two others did not at minimum core temperatures of 34.0 and 33.8 degrees C. Only one patient given enflurane vasoconstricted at a core temperature of 34.6 degrees C. The other six patients never vasoconstricted, at minimum core temperatures of 33.6 +/- 0.4 degrees C. Our data indicate that enflurane profoundly inhibits thermoregulatory responses in children. The mechanism for this extraordinary inhibition remains unknown but does not result from any obvious anesthetic pharmacology or thermoregulatory physiology. We conclude that unwarmed pediatric patients will become colder when anesthetized with enflurane than with halothane or isoflurane.

Anesthetics, Inhalation↗
PubMed1995

It is not necessary to administer more than 10 micrograms.kg-1 of atropine to older children before succinylcholine.

It is common practice at the Hospital for Sick Children, Toronto, to administer atropine 20 micrograms.kg-1 prior to succinylcholine in infants and children. It is unclear whether "prophylactic" administration of this dose of atropine to older children (6-16 yr) is necessary. This study was designed to compare the changes in heart rate, rhythm and mean arterial pressure after administration of either atropine 10 or 20 micrograms.kg-1 with succinylcholine or vecuronium (control group) to older children anaesthetized with thiopentone. Thirty-six ASA I or II patients (6-16 yr) were studied. Anaesthesia was induced with thiopentone 5 mg.kg-1. Patients were randomly assigned to receive: (a) atropine 10 micrograms.kg-1 and succinylcholine 1.5 mg.kg-1 (n = 12), (b) atropine 20 micrograms.kg-1 and succinylcholine 1.5 mg.kg-1 (n = 13) or (c) vecuronium 0.1 mg.kg-1 (n = 11) to facilitate tracheal intubation. Heart rate and rhythm were recorded continuously using a computerised analogue interface whereas blood pressure was monitored non-invasively before induction of anaesthesia, immediately before and at one and three minutes after laryngoscopy. No difference was observed between patients who received atropine 10 or 20 micrograms.kg-1 prior to succinylcholine. No episode of sinus bradycardia occurred. Premature atrial contractions were observed in two patients (one succinylcholine/atropine 20 micrograms.kg-1, one vecuronium). Administration of atropine 20 micrograms.kg-1 prior to succinylcholine provides no advantage over atropine 10 micrograms.kg-1 in older children in terms of cardiovascular stability.

Adolescent↗
PubMed1995

Persistent low cerebral blood flow velocity following profound hypothermic circulatory arrest in infants.

Acute neurological morbidity following repair of congenital heart disease (CHD) in infancy is well recognized, particularly with the modalities of hypothermic cardiopulmonary bypass (CPB) and profound hypothermic circulatory arrest (PHCA). Reduced O2 delivery (perfusion defect) during rewarming following PHCA has been shown in the operating room. This reduction in cerebral blood flow coincides with disordered cerebral metabolism and oxygen utilisation after PHCA. The objective of this study was to extend the period of investigation of cerebral blood flow velocity (CBFV) behaviour in infants following PHCA to determine if hypoperfusion persisted in the paediatric intensive care unit (PICU). Ten patients undergoing CHD surgery were divided, based on the pump modality employed, into either mild hypothermic CPB or profound hypothermic CPB with circulatory arrest. Following admission to the PICU, sequential recordings of the mean CBFV in the middle cerebral artery, anterior fontanelle pressure, haemodynamic variables, tympanic membrane temperature, haematocrit and PaCO2 were performed. The PHCA group had a consistently reduced CBFV compared with the control group (P < 0.05). The CBFV values at one, two and four hours were 60 +/- 11, 51.8 +/- 11.4 and 52.6 +/- 11.9 respectively in the mild hypothermic CPB group. The CBFV values at one, two and four hours were 26.6 +/- 6.8, 32.6 +/- 10 and 34 +/- 8 respectively in the PHCA group. There was no difference in cerebral perfusion pressure between both groups. Tympanic temperature, haematocrit and PaCO2 did not vary between groups at any interval. This study demonstrates a sustained reduction in the CBFV pattern following PHCA into the postoperative period despite adequate cerebral perfusion pressures. This abnormality correlates with electroencephalographic aberrations documented after PHCA. It supports the concept of a prolonged unreactive cerebrovascular bed which could potentially contribute to the acute neurological morbidity following PHCA in neonates.

Blood Flow Velocity↗
PubMed1995

Post-tonsillectomy infiltration with bupivacaine reduces immediate postoperative pain in children.

Pain management after tonsillectomy in children remains a dilemma for the anaesthetist. A previous study demonstrated that the administration of lidocaine 1% topical spray to the peritonsillar fossae before tracheal extubation provided considerable immediate postoperative pain relief in infants and children. However, the pain relief was of short duration. We were hopeful that the use of bupivacaine would offer more prolonged pain relief because of its pharmacological characteristics. Therefore, this study was designed to compare the effects of bupivacaine 0.5% with 1:200,000 epinephrine administered after tonsillectomy either as topical spray or submucosal infiltration on postoperative pain in children. Forty-three patients aged two to ten years were randomized into three groups after tonsillectomy was performed. Group (1) received 0.5 ml.kg-1 normal saline spray; (2) received 2 mg.kg-1 bupivacaine 0.5% with 1:200,000 epinephrine peritonsillar infiltration in a similar volume to Group 1 and; (3) received 2 mg.kg-1 bupivacaine 0.5% with 1:200,000 epinephrine spray to both tonsillar beds. The patients in each group were compared postoperatively with regard to the quality of pain control using the Objective Pain Score, and their analgesic requirements. Peritonsillar infiltration of bupivacaine provided superior immediate postoperative analgesia as reflected by lower recovery room pain scores (P < 0.05) and opioid requirements (P < 0.01). Ward pain scores and analgesic requirements were similar among groups. Peritonsillar infiltration of bupivacaine 0.5% with 1:200,000 epinephrine provides better post-tonsillectomy pain control in the immediate postoperative period than bupivacaine spray or placebo.

Anesthetics, Local↗
PubMed1995

Should the routine use of atropine before succinylcholine in children be reconsidered?

It is common practice to administer atropine before a first dose of succinylcholine in infants and children. However, the administration of succinylcholine without atropine has not been investigated in children. This study was designed to compare cardiovascular changes after the administration of either atropine with succinylcholine or succinylcholine alone. In 41 ASA I or II patients aged from 1 to 12 yr anaesthesia was induced with thiopentone 5 mg.kg-1. Patients were randomly allocated to receive either atropine 20 micrograms.kg-1 and succinylcholine 1.5 mg.kg-1 (n = 20) or succinylcholine 1.5 mg.kg-1 alone (n = 21). Heart rate and rhythm were recorded continuously from two minutes before induction until two minutes after tracheal intubation. Blood pressure was measured non-invasively before and after induction of anaesthesia and both immediately and two minutes after laryngoscopy. One self-limiting episode of bradycardia was recorded during laryngoscopy in a child who received atropine. Heart rate increased in both groups compared with baseline values (108 +/- 25), with a greater increase in patients who had received atropine (150 +/- 13) than in those who had not (128 +/- 18) (P < 0.05). There was no difference in mean arterial pressure or incidence of arrythmias between the two groups. No recorded arrythmias were judged to be clinically important by a cardiologist. The incidence of bradycardia after succinylcholine in the absence of atropine in children aged from 1 to 12 yr appears to be lower than previously estimated. The use of atropine before a single dose of succinylcholine in children deserves to be reconsidered.

Adjuvants, Anesthesia↗
PubMed1994

End-tidal carbon dioxide measurement in infants and children during and after general anaesthesia.

We have examined the reliability of end-tidal carbon dioxide (PetCO2) monitoring as an estimate of arterial carbon dioxide tension (PaCO2) in spontaneously breathing infants and children. Forty patients were studied in the post-anaesthetic care unit; 20 < 12 kg and 20 > or = 12 kg. The PetCO2 was sampled via a 5 cm 16 gauge catheter taped below an external naris and this measurement was compared with the PaCO2 of a sample drawn from an indwelling arterial line. Twenty additional patients were studied during inhalational anaesthesia. The PetCO2 was measured both from the proximal end of the elbow connector and from a 5 cm cannula inserted through the elbow. An arterial blood gas sample was obtained simultaneously. The arterial to end-tidal (Pa-et) differences were compared between the two sites. Patients studied in the post-anaesthetic care unit showed good correlation between PetCO2 and PaCO2 regardless of weight: Pa-etCO2 of -0.6 +/- 3.6 (< 12 kg) and -1.1 +/- 2.8 mmHg (> or = 12 kg). Patients studied during mask anaesthesia showed better correlation between PetCO2 and PaCO2 when PetCO2 was sampled from the cannula: Pa-etCO2 of 3.5 +/- 4.8 mmHg (cannula), 8.6 +/- 4.5 (elbow) (P < 0.05). These results suggest that end-tidal CO2 monitoring is a useful and reliable method for assessing adequacy of ventilation in spontaneously breathing children weighing between 5.2 and 35 kg.

Anesthesia Recovery Period↗
PubMed1994

Awake intubation increases intracranial pressure without affecting cerebral blood flow velocity in infants.

Tracheal intubation is frequently required in neonatal anaesthetic practice. Awake intubation is one method of securing the airway and in certain circumstances, for many anaesthetists, can be preferable to intubation following induction of anaesthesia. Previous studies have inferred that the elevation in anterior fontanelle pressure observed during tracheal intubation in neonates was caused by an increase in cerebral blood flow although it was never measured. In this study, direct methods were used to observe changes in the cerebral circulation. Thirteen neonates, ASA I to III (E), aged from 1 to 34 days of age were studied. Patients were randomized to receive either tracheal intubation awake or following induction of anaesthesia with thiopentone 5 mg.kg-1 and succinylcholine 2 mg.kg-1. Heart rate, systolic arterial blood pressure, anterior fontanelle pressure, cerebral blood flow velocity (using transcranial Doppler sonography) and oxygen saturation were recorded at the following intervals: baseline (not crying), after intravenous atropine 0.02 mg.kg-1, during laryngoscopy, immediately after insertion of the endotracheal tube, one and five minutes later. The use of atropine masked the cardiovascular responses to intubation. Whereas the change in anterior fontanelle pressure from baseline was different between the groups (P < 0.05), the cerebral blood flow velocity variables were not. The rise in anterior fontanelle pressure seen in the awake group may be attributed to a reduction of the venous outflow from the cranium thereby increasing cerebral blood volume and subsequently the intracranial pressure.

Cerebrovascular Circulation↗