Bain circuit occluded by foreign body

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - The purpose of this report is to describe a potentially hypoxic event which occurred during mask induction with the Bain...     

Interpleural block: a new technique for regional anaesthesia during percutaneous nephrostomy and nephrolithotomy

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - Interpleural block was used in four patients undergoing percutaneous nephrostomy, one of whom also underwent percutaneous...     

Intrathecal midazolam reduces isoflurane MAC and increases the apnoeic threshold in rats

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - The purpose of this study was to examine the anaesthetic requirement of intrathecal midazolam in a dose-response fashion in...     

Prophylactic administration of histamine1 and histamine2 receptor blockers in the prevention of protamine-related haemodynamic effects

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - We studied the effects of the prophylactic administration of histamine1 and histamine2 receptor blockers on haemodynamic...     

Oral premedication for paediatric ambulatory anaesthesia: a comparison of midazolam and ketamine

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - To compare the clinical characteristics of two oral premedicants, midazolam and ketamine, 40 healthy children, one to six...     

The pharmacokinetic behaviour of opioids administered during cardiac surgery

Cardiac surgery with hypothermic cardiopulmonary bypass (CPB) is among the most commonly performed operations in Canada today. The potential effects of hypothermia and CPB on the disposition of certain opioids are reviewed. Reasons for prolongation of the elimination half-time of the opioids used during cardiac surgery are explored. The roles that age, hypothermia, protein binding and drug sequestration may play in changing opioid pharmacokinetic behaviour are examined and suggestions for future research are made.     

Oral midazolam premedication for children with congenital cyanotic heart disease under-going cardiac surgery: a comparative study

To determine whether oral midazolam is a safe and effective alternative to our current standard premedication for children with cyanotic congenital heart disease (CCHD), 30 children aged 1–6 yr, scheduled for elective cardiac surgery, were studied. The children were randomly assigned to one of two groups: Group I received oral midazolam 0.75 mg · kg^{? 1} 30 min before separation from their parents in the surgical waiting area, and Group II received oral or rectal pentobarbitone 2 mg · kg^{? 1} at 90 min, and morphine 0.2 mg· kg^{? 1} and atropine 0.02 mg· kg^{? 1} im at 60 min before separation. Heart rate, haemoglobin oxygen saturation (SpO₂) and anxiolysis and sedation scores were recorded at four times during the study: at baseline (immediately before premedication), immediately after administration of the premedication, at separation of children from parents in the waiting area and at the time of application of the face mask in the operating room. We found that in Group I, anxiolysis improved at separation from parents compared with baseline (P < 0.05) and sedation increased both at separation and on mask application (P < 0.05), whereas in Group II anxiolysis did not change at any time and sedation increased only at separation (P < 0.05). Intramuscular injection of morphine produced a transient decrease in mean SpO₂ (from 84% to 76%) (P < 0.05) that did not occur after ingestion of oral midazolam. The results of this study indicate that oral midazolam is a safe and effective replacement for the standard premedication for children with CCHD undergoing cardiac surgery and avoids the decrease in SpO₂ associated with im injections.     

Alfentanil infusion for sedation in infants and small children during cardiac catheterization

We have analyzed several sedation techniques for paediatric cardiac catheterization which offer stable conditions for a few hours investigation, and maintain spontaneous breathing. In the present study, after premedication with oral flunitrazepam 0.1 mg.kg-1, 14 children aged 1-17 mo were sedated with an individually titrated alfentanil infusion. Every patient was sedated to a level which produced no reaction to pain or any discomfort. The induction dose and the maintenance requirement of alfentanil were 24 +/- 8 micrograms.kg-1 and 32 +/- 8 micrograms.kg-1.hr-1 (mean +/- SD), respectively. These doses were less in cyanotic than in acyanotic patients: 21 +/- 6 vs 28 +/- 8 micrograms.kg-1 and 29 +/- 10 vs 34 +/- 3 micrograms.kg-1.hr-1, respectively (P less than 0.05). The mean plasma concentration of alfentanil during maintenance of sedation was 79 +/- 23 ng.ml-1. Ventilation of two children was assisted for a short time after an incremental bolus of alfentanil. It is concluded that an alfentanil infusion technique with close monitoring of breathing is a practical sedation method for paediatric cardiac catheterization.     

The initial distribution volume of glucose and cardiac output in the critically ill

Blood or plasma glucose concentration can be measured accurately and rapidly. However, after a glucose challenge metabolism may modify glucose kinetics, so that glucose has not been used as an indicator for dilution volumetry. To test the hypothesis that the initial distribution volume of glucose (IDVG) reflects cardiac output rather than glucose metabolism in the critically ill, the relationship between IDVG and thermodilution cardiac output was evaluated at 27 points in 13 non-surgical, critically ill patients without congestive heart failure. The IDVG was calculated from incremental plasma glucose concentrations using a one compartment model. Correlations were obtained between the IDVG and cardiac output (r = 0.89, n = 27, P < 0.001), and between the incremental plasma glucose concentrations three minutes after the injection and the IDVG (r = 0.94, n = 27, P < 0.001). No difference was found between the IDVG with or without continuous insulin infusions. The results indicate that the IDVG reflects cardiac output rather than glucose metabolism in patients without congestive heart failure.     

Clinical application of cardiac risk indices: How to avoid misleading numbers

Perioperative cardiac complications are associated with a high mortality rate. During the preoperative assessment the anaesthetist must determine if the patient is at risk so that appropriate interventions can be made to ensure the best possible outcome. Over the past three decades several indices have been proposed to identify the surgical patient at risk of cardiac morbidity or mortality. These indices can be thought of as diagnostic tests which determine the likelihood of perioperative cardiac complication. In this article the authors review the epidemiological basis of diagnostic tests and apply this theory to three currently available indices of perioperative risk: the American Society of Anesthesiologists physical status classification, the Goldman multifactorial cardiac risk index and a modified version devised by Detsky. A case history describing a surgical patient with unstable angina is first presented to show how different indices can lead to different predictions. These indices are then analysed as if they were diagnostic tests to predict cardiac complications after surgery. The characteristics of diagnostic tests such as sensitivity, specificity, positive and negative predictive values, and receiver operating characteristic curves are described and applied to the indices. Basic principles such as odds ratio, likelihood ratio and their relation to prevalence and post-test probability are also presented. This overview will help the anaesthetist to understand the limitations of risk indices as predictors of adverse cardiac outcome and to apply these scales more effectively to individual patients at different institutions.     

The evolution of anaesthesia as a specialty in Canada

Since 1847 anaesthesia in Canada has evolved through six phases. In the first (1847-1898), it was a craft without an academic and professional base. The second (1899-1919) was marked by the first academic appointments and by Canadians' wartime experiences of anaesthesia. The third phase (1920-1929) evidenced the professional satisfaction of anaesthesia and included the founding of the Canadian Society of Anaesthetists. In the fourth phase (1930-1943) the growth of the Royal College of Physicians and Surgeons of Canada, the introduction of certification and the founding of the definitive professional society--the Canadian Anaesthetists' Society--fostered the evolution of what was now becoming a recognizable specialty. The fifth phase (1944-1971) was one of resolution of problems affecting the status of anaesthesia: the first autonomous department of anaesthesia in a Canadian university was founded (at McGill in 1945), the Royal College Fellowship was approved for anaesthesia (in 1951), the Canadian Anaesthetists' Society Journal was launched (in 1954) and a single standard for certification of specialists was finally established (in 1971). In the sixth (1972-1989), the main elements were the assumption of responsibility for residency training by the universities and by the renaming of the journal as the Canadian Journal of Anaesthesia. Through these years of increasing professionalism, it has, however, been the accomplishments of individual Canadian physicians, facing many challenges, that have made the specialty in Canada recognizably Canadian.     

The stratification of cardiac surgical procedures according to use of blood products: a retrospective analysis of 1480 cases

The use of blood products in 1480 consecutive cases of adult cardiac surgical procedures over a period of 15 mth was studied retrospectively using the database of the Department of Anaesthesia of the Institut de Cardiologie de Montreal. Use of blood products was compared in patients having (1) coronary artery bypass grafting, (2) valvular surgery, (3) or a combination of 1 and 2. First operations were compared with reoperations. Overall, the use of homologous blood products was greatest in patients of Group 3, intermediate in patients of Group 2, and smallest in patients of Group I. Reoperations were associated with an increase in inlraoperative transfusion of packed red blood cells, but postoperative chest drainage was similar to first operations. When all blood products (packed red blood cells, fresh frozen plasma and platelets were taken into consideration, patients undergoing primary CABG or valve surgery were the least exposed to homologous blood donors (five and six units transfused respectively). Repeat CABG was associated with an intermediate exposure to homologous blood products (eight units). Finally, primary and repeat combined procedures, and repeat valve surgery were associated with the greatest exposure to foreign blood products (10, 13 and 10 units respectively). The data presented in this study provide a rational basis for stratification of procedures according to the expected use of blood products, particularly in view of future studies which may be planned to examine the efficiency of blood conservation strategies. Cette étude rétrospective rapporte l’utilisation des produits sanguins en chirurgie cardiaque de l’adulte à l’Institut de Cardiologie de Montréal chez 1480 patients opérés sous circulation extracorporelle entre novembre 1988 et avril 1990. Les patients out été regroupés selon l’intervention subie: 1) la revascularisation myocardique, 2) la chirurgie valvulaire, 3) une combinaison de 1 et de 2. Nous avons égalemenl comparé les interventions de premiere intention avec les réinterventions. A u total, les besoins en produits sanguins homologues out été les plus considérables chez les patients du groupe 3, intermédiaires chez les patients du groupe 2, et les plus faibles chez les patients du groupe I. Les réinterventions out été associées à une augmentation des transfusions de culots globulaires durant la chirurgie, mais non à des pertes sanguines postopératoires accrues. Lorsque tous les produits sanguins sont pris en consideration (culots globulaires, plasma, plaquettes), l’exposition (en nombre dunités) aux produits sanguins homologues était la plus faible chez les patients subissant une premiere chirurgie de revascularisation (cinq unités) on une chirurgie valvulaire de premiere intention (six unités). Dans la réintervention pour revascularisation myocardique Vexposition était intermédiaire (huit unités), alors qu’elle était la plus forte dans la chirurgie combinée, qu’elle soit primaire ou de réintervention (10 ou 13 unités). Les données présentées dans cette étude permettent de stratifier les chirurgies en fonction des besoins transfusionnels prévus et devraient nous guider dans la gestion des technologies visant à diminuer les pertes sanguines el l’exposition aux produits sanguins homologues en chirurgie cardiaque de l’adulte.     

Paediatric cardiac catheterization: innovations

In recent years interventional procedures have been introduced to the field of paediatric cardiac catheterization. These procedures continue to develop in complexity and increasingly are being applied to patients with reduced cardiovascular reserve, as an alternative to cardiac surgery or when cardiac surgery with cardiopulmonary bypass is contraindicated. More frequently anaesthetists are being called upon to provide support in sedating, anaesthetizing or/and resuscitating these patients. The purpose of this review is to give a comprehensive update of the interventional procedures and to review the anaesthetic management techniques as they apply to the catheterization laboratory. We will discuss possible complications and management strategies from our own experience and the experience of others. We have observed that as more complicated procedures are performed the anaesthetist plays a pivotal role in the management of the patient from arrival to departure from the cardiac catheterization laboratory, and in preventing mortality and major morbidity. Although the economic consequences of interventional cardiological techniques remain unclear, the field continues to expand and more complex procedures are continually being introduced.     

The initial distribution volume of glucose and cardiac output after haemorrhage in dogs

The purpose of the study was to evaluate the role of insulin in glucose kinetics after glucose administration using an insulinogenic index to indicate the magnitude of insulin response. The initial distribution volume of glucose (IDV-G) was calculated with a one-compartment model from repeated measurements of plasma glucose concentration three to seven minutes after administration of 100 mg · kg^?1 glucose. The IDV-G was compared with the insulin response and the thermodilution assessments of cardiac output, measured simultaneously both before and after induced haemorrhage (30 ml · kg^?1 over 30 min) in 12 adult mongrel dogs. The plasma insulin concentration was measured during the procedure and insulinogenic indices were calculated. There was no correlation between the IDV-G and insulinogenic indices, but there was a correlation between the IDV-G and thermodilution cardiac output before and after induced haemorrhage (r = 0.85, n = 24, P < 0.001). We conclude that the initial distribution volume of glucose is an indication of cardiac output in normo- and hypovolaemic dogs. Modification of glucose kinetics by the insulin response to glycaemic stimuli was negligible in that short period of time.     

Errors in the measurement of cardiac output by thermodilution

Cardiac output (CO) determination by thermodilution, which was introduced by Fegler in 1954, has gained wide acceptance in clinical medicine and animal experiments because it has several advantages over other methods with respect to simplicity, accuracy, reproducibility, repeated measurements at short intervals, and because there is no need for blood withdrawal. However, errors in determination of CO by thermodilution may be introduced by technical factors and the patients’ pathological conditions. The current review summarizes these issues and provides our recommendations, based on the medical literature published between 1954–1992. To obtain more reproducible and accurate CO values by thermodilution, one should make several determinations (1) by using 10 ml injectate at room temperature for adults and 0.15 ml · kg⁻¹ injectate for infants and children; (2) at evenly spaced intervals of the ventilation cycle; (3) when rapid intravenous fluid administration is discontinued; (4) by observing thermodilution curves so that baseline pulmonary artery temperature drift or the existence of intra- and extra-cardiac shunts are noticed. Finally, CO determination by thermodilution may be unreliable or impossible in patients with low CO slates and tricuspid or pulmonary regurgitation. Since non-invasive CO monitoring has not replaced CO determination by thermodilution, intimate knowledge of this method is crucial for anaesthetists to prevent errors in the management of patients. La mesure du débit cardiaque par thermodilution introduite par Fegler en 1954 est largement répandue en clinique et en recherche animale grace à ses nombreux avantages sur les autres méthodes: simplicité, précision, reproductiblé, répétivité à courts intervalles, absence de prélèvement sanguin. Cependant, dans son application il peut facilement s’introduire des erreurs d’origine technique ou pathologique. La présente revue résume ces questions et propose certaines recommandations, basées sur la littérature médicale publiée entre 1954 et 1992. Pour obtenir des mesures fiables et précises du débit cardiaque par thermodilution, il faut répéter les mesures: 1) avec 10 ml d’injectat maintenu à température de la pièce chez le adulte, 0,15 ml · kg^{− 1} chez l’enfant; 2) à des moments identiques du cycle respiratoire; 3) après l’arret d’une perfusion rapide de liquide intraveineux; 4) en observant les courbes de thermodilution pour pouvoir tenir compte de la dérive de la température initiale de l’artère pulmonaire et de la présence de shunts intraou extracardiaques. Finalement, le débit cardiaque par hémodilution peut manquer de fiabilité et peut même devenir impossible à mesurer chez les malades dont le débit est bas ou qui souffrent de régurgitation tricuspidienne ou pulmonaire. Comme le monitorage du débit cardiaque non invasif n’a pas encore remplacé la thermodilution, les anesthésistes doivent posséder une connaissance approfondie de cette méthode pour éviter des erreurs thérapeutiques graves.     

Regional anaesthesia for hernia repair in children: local vs caudal anaesthesia

The purpose of this study was to compare the effect of local anaesthesia (LA) with that of caudal anaesthesia (CA) on postoperative care of children undergoing inguinal hernia repair. This was a randomized, single-blind investigation of 202 children aged 1–13 yr. Anaesthesia was induced with N₂O/O₂ and halothane or propofol and maintained with N₂O/O₂/halothane. Local anaesthesia included ilioinguinal and iliohypogastric nerve block plus subcutaneous injection by the surgeon of up to 0.3 ml · kg^?1 bupivacaine 0.25% with 5 μg · kg^?1 adrenaline. The dose for caudal anaesthesia was 1 ml · kg^?1 up to 20 ml bupivacaine 0.2% with 5 μg · kg^?1 adrenaline. Postoperative pain was assessed with mCHEOPS in the anaesthesia recovery room, with postoperative usage of opioid and acetaminophen in the hospital, and with parental assessment of pain with a VAS. Vomiting, time to first ambulation and first urination were recorded. The postoperative pain scores and opioid usage were similar; however, the LA-group required more acetaminophen in the Day Care Surgical Unit. The incidence of vomiting and the times to first ambulation and first urination were similar. The LA-patients had a shorter recovery room stay (40 ± 9 vs 45 ± 15 min, P < 0.02). The postoperative stay was prolonged in the CA group (176 ± 32 vs 165 ± 26 min, P = 0.02). We conclude that LA and CA have similar effects on postoperative care with only slight differences.     

Nasal ketamine for paediatric premedication

Ketamine in a dose of 6 mg · kg⁻¹ was nasally administered in 86 healthy children (ASA I and II), aged from two to five years undergoing elective general, urological or plastic surgery, 20 to 40 min before the scheduled surgery time. These children were compared with 62 others, also aged from two to five years, in whom promethazine and meperidine, 1 mg · kg⁻¹ of each, were injected im. Sedation was started as excellent in 48 and as adequate in 19 children in the ketamine group, compared with nine and 12 respectively in Group 2 (P < 0.05), while salivation was similar in both groups. We conclude that nasal ketamine is an alternative to im preanaesthetic sedation administration in children aged from two to five years. Vingt à quarante minutes avant la chirurgie, de la kétamine 6 mg · kg⁻¹ est administrée par voie nasale à 86 enfants en bonne santé (ASA I et II), agés de deux à cinq ans programmés pour une intervention urologique ou plastique non urgente sous anesthésie générale. On compare ces enfants à 62 autres enfants du même age, auxquels on a injecté par la voie i.m., soit de la mépéridine, soit de la prométhazine, à la dose de 1 mg · kg⁻¹. La sédation est jugée excellente pour 48 et adéquate pour 19 des enfants du groupe kétamine, comparativement à 9 et 12 des enfants du groupe 2 (P < 0,05), alors que la salivation est identique dans les deux groupes. Nous en concluons que la kétamine nasale est une alternative a la prémédication intramusculaire pour des enfants de deux à cinq ans.     

Comparison of a rigid laryngoscope with the ultrathin fibreoptic laryngoscope for tracheal intubation in infants

The flexible ultrathin fibreoptic laryngoscope allows placement of endotracheal tubes as small as 2.5 mm internal diameter. The purpose of this study was to document the safety and efficacy of intubation using an ultrathin fibreoptic laryngoscope. Proved safety and efficacy would justify the routine use of fibreoptic laryngoscopy in normal infants to maintain skills needed for management of the difficult infant airway. In this prospective study, 40 infants <24 mo of age scheduled for elective surgery were randomly divided into two equal groups. After inhalation induction of anaesthesia, in 20 infants the trachea was intubated using direct rigid laryngoscopy, and in 20 using the ultrathin fibreoptic laryngoscope (size 1.8 mm OD) Olympus LFP. Time to successful intubation was recorded, as well as blood pressure, heart rate, end-tidal CO₂ and oxygen saturation. Airway trauma in the operating room, the post-anaesthesia care unit, and on the first postoperative day was recorded. The intubation times using rigid laryngoscopy were less than those using fibreoptic laryngoscopy (13.6 ± 0.9 sec (mean ± SEM) vs 22.8 ± 1.7 sec; P < 0.01). Oxygen saturation and end-tidal CO₂ readings were not different between the two groups. After intubation, blood pressure and heart rate increased equally in both groups, returning to normal within one to two minutes. There was no difference in the airway trauma between groups. We conclude that the ultrathin fibreoptic laryngoscope is a safe and effective method for tracheal intubation in infants and may be used routinely in order to maintain fibreoptic airway skills.     

Intrathecal meperidine for elective Caesarean section: a comparison with lidocaine

The purpose of this study was to determine the efficacy of intrathecal meperidine in patients undergoing Caesarean section, and also to compare meperidine with heavy lidocaine. Fifty fall-term pregnant women, ASA physical status I or II, presenting for elective Caesarean section under spinal anaesthesia were randomly divided into two groups with 25 in each, to receive either intrathecal meperidine or lidocaine. All patients received premedication with oral ranitidine, 150 mg, the night before surgery, and again two hours before surgery. Patients in the meperidine group were also given metoclopramide iv 10 mg one hour before surgery. After iv 20 ml·kg^?1 Ringer’s lactate, patients were given either 5% meperidine 1 mg · kg^?1 or 5% heavy lidocaine 1.2 to 1.4 ml intrathecally. The sensory and motor blockades in all except two patients in each group who required sedation at the time of skin incision were adequate for surgery. None of the mothers suffered from any major side effects. The incidence of hypotension was higher in the lidocaine group than in meperidine group (P < 0.05). Pruritus and drowsiness were more common in meperidine group than in lidocaine group (P < 0.01). All the newborns in both groups cried immediately after birth and had an Apgar scope > 7. The mean duration of postoperative analgesia was six hours in the meperidine group and one hour in the lidocaine group (P < 0.01). Postoperative analgesia requirement was less in the meperidine than in the lidocaine group (P < 0.01). It is concluded that intrathecal 5% meperidine in a dose of 1 mg·kg^?1 is superior to 5% heavy lidocaine because of the prolonged postoperative analgesia. The commercial 5% solution of meperidine can be used, without addition, for this purpose.     

Effets de l’halothane sur la ventilation et les gaz du sang artériel chez le rat avec ou sans paralysie diaphragmatique

Certains patients atteints de paralysie diaphragmatique ou de dysfonctionnement diaphragmatique maintiennent leur ventilation par la mise en jeu d’autres muscles que le diaphragme. L’anesthésie, modifiant le fonctionnement de ces muscles, représente un risque potentiel chez ces patients. Afin d’évaluer ce risque, nous avons étudié les effets de l’halothane sur la ventilation et sur les gaz du sang artériel sur un modèle de paralysie diaphragmatique bilatérale, le rat phrénicectomisé. L’étude a été réalisée sur 43 rats. L’efficacité de la phrénicectomie a été contrôlée par l’observation directe, après laparotomie. La laparotomie n’entraine pas de modification des gaz du sang. Chez 23 rats, une laparotomie a été effectuée et une artère carotide a été cathétérisée. Chez 11 rats témoins, les nerfs phréniques ont été abordés, sans être sectionnés. Chez 12 rats, les phréniques ont été sectionnés. La ventilation a été mesurée par une technique pléthysmographique, chez les rats éveillés, avant et après l’opération, puis chez les mêmes rats anesthésiés avec 1,1%, d’halothane inspiré. Les gaz du sang ont été mesurés après l’opération chez les rats éveillés, puis anesthésiés. Chez les 23 rats opérés on observe, après l’opération, une diminution du poids et de la température centrale, plus importante chez les phrénicectomisés que chez les témoins. Chez les 11 rats témoins, après l’opération, la ventilation augmente, sans modification des gaz du sang. Chez ces rats, l’halothane provoque une diminution de la ventilation minute et de la PaO₂ et une augmentation de la PaCO₂. La phrénicectomie entraine chez les 12 rats, éveillés, une augmentation de la ventilation minute, une hypoxémie et une hypercapnie. Chez ces rats, l’halothane entraine le décès dans trois cas, une diminution de la ventilation minute et une hypercapnie et une hypoxémie importantes chez les neuf autres rats. Les modifications des gaz du sang sont plus importantes que chez les témoins anesthésiés. Chez le rat intact, l’halothane provoque des modifications des gaz du sang comparables à celles observées chez d’autres espèces et chez l’homme. La présente étude confirme les effets de l’halothane sur les muscles respiratoires autres que le diaphragme. Elle met en évidence le risque respiratoire majeur que l’anesthésie peut fair courir aux patients dont la ventilation est maintenue par d’autres muscles que le diaphragme.