Keiko Kinouchi

Duration of Apnea in Anesthetized Infants and Children Required for Desaturation of Hemoglobin to 95%The Influence of Upper Respiratory Infection

Sixty-one patients ASA physical status 1-2 aged 1 month to 12 years undergoing elective surgery were included in the study. Anesthesia was induced via a mask with sevoflurane up to 5% and 66% nitrous oxide in oxygen. After paralysis with vecuronium (0.12 mg/kg iv), the trachea was intubated and the lungs were ventilated manually with 3% sevoflurane in oxygen until the end-tidal nitrous oxide decreased to less than 5%. Apnea was started by disconnecting the breathing circuit from the endotracheal tube. The time from the start of apnea to Spo2 of 95% was measured. Manual ventilation was reinstituted when Spo2 decreased to 95% and another set of vital signs was recorded. Twenty of 61 patients had symptoms of upper respiratory infection. The time to Spo2 of 95% correlated well with height, age, and body weight both by linear and non-linear regression analyses. The patients with symptomatic upper respiratory infection required less time for Spo2 to decrease to 95% compared to the asymptomatic children. We conclude that younger children require less time for Spo2 to decrease to 95%. The presence of upper respiratory infection is an additional factor increasing the susceptibility of small children to hypoxemia.

Duration of apnoea in anaesthetized children required for desaturation of haemoglobin to 95%: comparison of three different breathing gases.

In this study, we compared three gas compositions to determine if the duration of apnoea for Spo2 to decrease is proportionate to the oxygen fraction of the gas prior to apnoea. Twenty‐five patients ASA physical status 1–2 aged two months to 12 years were included in the study. Anaesthesia was induced via a mask with 5% sevoflurane and 66% N2O in oxygen. After paralysis with vecuronium (0.12 mg·kg−1, i.v.) the trachea was intubated and anaesthesia was maintained with sevoflurane and N2O in oxygen. When cardiovascular stability was obtained, the patient was randomly set to breathe one of three gas compositions: 1. oxygen (Fio2 1.0), 2. N2O/O2 (Fio2 0.4), and 3. air/O2 (Fio2 0.4). All three gas compositions included 2–4% of sevoflurane to maintain anaesthesia. After more than eight min of each gas breathing, apnoea was begun by disconnecting the breathing circuit from the tracheal tube. The time from the start of apnoea (Spo2 100%) to Spo2 of 95% (T95) was measured. T95 measured after breathing N2O/O2 and air/O2 were 34.6 ± 5.7 and 28.8 ± 4.7% of that measured after oxygen breathing (P < 0.001 vs oxygen breathing, P < 0.001 vs oxygen and N2O/O2 breathing), respectively. Preoxygenation before intubation was validated to delay the haemoglobin desaturation brought about by apnoea. An induction technique using a low Fio2 will allow rapid haemoglobin desaturation.

Arterial oxygenation during one lung ventilation

PurposeTo compare the effects of isoflurane and sevoflurane on artenal oxygenation and middle cerebral artery blood flow velocity during one lung ventilation.MethodsThis was a randomized, crossover study in 20 patients undergoing thoracotomy for oesophageal cancer and scheduled for long term one lung ventilation (OLV). They were randomized to one of two groups: group A. firstly isoflurane was administered followed by sevoflurane, and then isoflurane was resumed; group B. the order of the administration was reversed. Artenal blood gas samples were drawn at the start of OLV, 30 and 60 min after the initiation of OLV and the end of OLV (the change of volatile anesthetics was done 30 and 60 min after the start of OLV). Middle cerebral artery (MCA) was monitored continuously with the probe positioned over the temporal bone window. This probe transmitted 2 MHZ wave Doppler signals. Time-averaged MCA blood flow velocity was calculated from the signals.ResultsThe PaO values decreased 30 min after the start of OLV (364.4 ±33.4 mmHg vs 179.0 ± 19.5, and 338.7 ± 24.8 mmHg vs 139.7 ± 19.9 in groups A and B respectively), but there was no difference between the groups. Blood flow velocity of MCA did not change after the start of OLV (53.1 ± 3.2, 55.9 ± 3.0. 56.4 ± 2.4, and 54.1 ± 1.9 vs 50.8 ± 2.1, 50.7 ± 2.4, 53.7 ± 1.5, 50.8 ± 2.2 cm · sec−1 in groups A and B respectively): there was no difference between the groups. (P < 0.05).ConclusionIn clinical practice, the selection of either isoflurane and sevoflurane for OLV was of no difference in terms of the artena 1 blood oxygenation. With both agents MCA blood flow velocity was maintained during OLV.RésuméObjectifComparer les effets de l’isoflurane et du sévoflurane sur l’oxygénation arténelle et la vélocité du débit de l’artère cérébrale moyenne pendant la ventilation unipulmonaire.MéthodesCette étude aléatoire avec croisement regroupait 20 sujets thoracotomisés pour un cancer de l’oesophage et programinés pour une ventilation unipulmonaire (VUP) prolongée. Ils ont été répartis au hasard en deux groupes: le groupe A recevait de l’isoflurane suivi du sévoflurane et de l’isoflurane à nouveau; dans le groupe B, l’ordre des agerts était inversé. Des échantillons de sang étaient prélevés pour la gazométne arténelle au début de la VUP, 30 et 60 min plus tard, et à la fin de la VUP (l’échange d’anesthésique volatil survenait 30 et 60 min après l’initiation de la VUP) Un capteur placé sur l’os temporal permettait de monitorer l’artère cérébrale moyenne (ACM) en continu par la transmission d’ondes Doppler de 2 MHZ Ces signaux ont servi au calcul de la moyenne de la vélocité du débit de l’ACM en fonction du temps.RésultatsLes valeurs de la PaO2 ont diminué 30 min après le début de la VUP (respectivement dans les groupes A et B; 364,4 ± 33,4 mmHg à 179,0 ± 19,5 et 338,7 ± 24,8 mmHg à 139,7 ± 19,9) mais sans différence intergroupe La vélocité sanguine de l’ACM n’a pas changé après la mise en marche de la VUP (respectivement dans les groupes A et B; 53,1 t 3,2; 55,9 ± 3,0: 56,4 ± 2,4 et 54,1 ± 1,9 vs 50,8 ± 2,1; 50,7 ± 2,4; 53,7 ± 1,5: 50,8 ± 2,2 cm · s−1); il n’y a pas eu de différence entre les groupes (P < 0,05).ConclusionEn clinique, le choix de l’isoflurane ou du sévoflurane pour la VUP n’influence pas l’oxygénation artérielle Le débit sanguin de l’ACM se maintient pendant la VUP avec l’un et l’autre des agents.

A new modification of anaesthesia mask for fibreoptic intubation in children.

We made a paediatric anaesthesia mask suitable for fibreoptic intubation by modifying a commercially available disposable mask with a ventilation port (Vent port) on a side. We added a large fibreoptic port (FO port, 22 mm in ID) in the middle of the mask to allow the passage of all sizes of paediatric tracheal tubes. This FO port was covered with an elastic rubber membrane to allow air‐tight fibrescopic manipulation. Fibreoptic intubation was performed safely through the FO port under continuous manual ventilation with anaesthetic gases via a Vent port connected to the breathing circuit. We succeeded in tracheal intubation in several infants and children with difficult airway in less than ten min, mainly via the nasotracheal route. This fibreoptic mask provides a safer technique for fibreoptic intubation in patients with difficult airways, especially in infants and small children.

A rare case of upper airway obstruction in an infant caused by basal encephalocele complicating facial midline deformity.

A four‐month‐old male infant with basal encephalocele of the transsphenoidal type presented with upper airway obstruction and facial midline deformity, including cleft lip, cleft palate, hypertelorism and exophthalmos. Basal encephalocele is a rare disease, and usually not detectable from the outside. In this case, initially the cause of an upper airway obstruction was considered to be posterior rhinostenosis, and posterior rhinoplasty with inferior nasal conchectomy was scheduled. However, in preoperative examination, computed tomography (CT) and magnetic resonance imaging (MRI) revealed a bony defect in the sphenoidal bone and a cystic mass in communication with cerebrospinal fluid, herniating into the nasal cavity through the bony defect. The mass was diagnosed as a transsphenoidal encephalocele, the scheduled operation cancelled, and tracheostomy performed for airway management. The possibility of basal encephalocele should be considered in the case of upper airway obstruction with facial midline deformity.

Postbypass pulmonary artery pressure influences respiratory system compliance after ventricular septal defect closure

It is reported that surgical correction of left‐to‐right shunt improves respiratory function in paediatric cardiac patients. However, such correction sometimes does not result in an improvement of respiratory compliance. The purpose of this study was to look for factors determining changes in respiratory system compliance (Crs) in patients who underwent closure of ventricular septal defect (VSD closure). In a prospective study, 17 children (< 10 kg) who underwent VSD closure were enrolled. They were divided into two groups, according to postbypass mean pulmonary artery pressure (mPAP). The patients were allocated to Group C if mPAP was ≤ 18 mmHg (n=12) and to Group PH if > 18 mmHg (n=5). We compared the ratio of postoperative Crs to preoperative Crs (Cpost/Cpre) between the groups. A multiple occlusion technique was used to measure Crs. The Cpost/Cpre in group C was larger than that in group PH (1.11 ± 0.17 vs. 0.81 ± 0.12, P < 0.01). There was a correlation between postbypass mPAP and Cpost/Cpre (rs=0.49, P < 0.05), but no correlation was noted between preoperative mPAP, Qp/Qs or Rp/Rs and Cpost/Cpre. We concluded that high postbypass mPAP was associated with a perioperative decrease in Crs after VSD closure.

Brachial plexus birth injuries: anaesthesia for surgical nerve reconstruction and preoperative myelography and computed tomographic myelography.

Surgical nerve reconstruction for brachial plexus birth injuries and preoperative myelography and computed tomographic (CT) myelography require special anaesthetic considerations. Anaesthesia and medical records were retrospectively reviewed for the infants who underwent myelography, CT myelography (n=37) and microsurgical nerve reconstruction (n=34) at our institution from January 1993 to August 1996. Anaesthetic considerations include long duration of operation, perioperative respiratory complications and plaster application which makes reintubation difficult. Myelography for diagnosis requires a specific positioning of the patient with the head fixed in a midline and prone position.

Effects of pentazocine and other opioids on the potassium-evoked release of [3H]noradrenaline from guinea pig cortical slices

Noradrenaline release and its modulation via presynaptic opioid receptors were examined in guinea pig cortical slices. Slices preloaded with [3H]noradrenaline were superfused in the presence of desipramine (1 microM) and were stimulated by 16 mM K+. 1-Pentazocine inhibited the K+-evoked release of [3H]noradrenaline in a dose-dependent manner (3 x 10(-7)-10(-5) M), while d-pentazocine did not inhibit. This inhibitory effect of 1-pentazocine was antagonized by Mr 2266 (10(-6) M) but not by naloxone (10(-6) M). Among other opioids, dynorphin A-(1-13) and ethylketocyclazocine (kappa agonists) decreased the K+-evoked release of [3H]noradrenaline. Tyr-D-Ala-Gly-NMe-Phe-Gly-ol (DAGO, mu agonist) also inhibited [3H]noradrenaline release but was less potent than the kappa agonists. [D-Pen2,D-Pen5]enkephalin (DPDPE, delta agonist) and phencyclidine (sigma agonist) had no effects on the stimulated release of [3H]noradrenaline. Thus, it was shown that kappa receptors are the major subtype of opioid receptor involved in modulation of noradrenaline release in guinea pig cortex, and that 1-pentazocine inhibits the K+-evoked release of noradrenaline through activation of these receptors.

Improved viability of the low birth weight infant and the increasing needs for anaesthesia

The extensive use of surfactant and antenatal steroids has contributed to the improved survival of very low birth weight (VLBW, de®ned as < 1500 g) and extremely low birth weight (ELBW, de®ned as < 1000 g) infants. Intratracheal administration of surfactant became available for treatment of respiratory distress syndrome (RDS) in VLBW infants around 1988. Many authors have compared the mortality and morbidity of VLBW infants from the two periods, before and after surfactants became available, and invariably found improved survival of VLBW infants after the introduction of surfactant (1±4). In 1976, the World Health Organization de®ned fetuses weighing < 500 g as nonviable births (5). In 1995, the American Academy of Pediatrics and American College of Obstetricians and Gynecologists documented that the overall neonatal survival rate for infants born in 1987±90 during 23±25 weeks of gestation remained less than 40% and stated that the birth of an infant at, or before, 25 weeks of gestation, or weighing less than 750 g, presents a variety of complex medical, social, and ethical decisions (6). According to a 25-question survey sent to 3059 neonatologists practicing in the USA in 1992, 99% of neonatologists would resuscitate an infant born at 25 weeks gestation. More than 90% of neonatologists considered nonintervention or compassionate care appropriate for infants born at < 23 weeks gestation. Neonatologists who responded to this survey considered 23±24 weeks of gestation the limit of viability (7). After 1991, when the administration of antenatal steroids, the use of exogenous surfactant and the use of dexamethasone for bronchopulmonary dysplasia had become accepted treatments, the survival rates of 24 and 25 weeks gestation infants and their intact survival rates have been gradually increased. Many investigators have reported their survival rates to be near or over 50% (8±11). Survival rates at 22 and 23 weeks gestation, however, have been poor (8±11). To improve the survival and reduce morbidity of infants of 22± 26 weeks gestation, the optimization of fetal and perinatal condition and the management by a team of skilled personnel is mandatory. When the delivery at 22±26 weeks gestation is anticipated, maternal transport to a regional perinatal centre should be considered and discussed with the family. Many obstetricians and neonatologists consider clinicians should discuss the situation with informed parents to help decide the mode of delivery and whether to provide active treatment, including resuscitation, or to withhold resuscitation and give compassionate care to infants of 22±25 weeks of gestation (4,12±14). According to a survey sent to 450 physicians practicing obstetrics and gynaecology in the state of California in 1996, 60% of physicians believe that parents have a role in deciding not to resuscitate their infant born at 22 weeks gestation in the delivery room, and this decreases to less than 50% at 24 weeks, and decreases further to less than 30% by 26 weeks gestation (13). Surfactant and improved respiratory care have brought improved survival of VLBW and ELBW infants and their neurodevelopmental outcomes have been proved not to be worse than those of earlier years as many physicians feared (4,15). Because the infants with lower birth weight, who would not have survived in earlier days, are now surviving, the incidence of diseases relevant to prematurity or low birth weight may be increasing. The incidence of severe RDS, pneumothorax and pulmonary interstitial emphysema decreased, but the incidence of patent ductus arteriosus (PDA), retinopathy of prematurity (ROP), necrotizing enterocolitis and septicaemia in VLBW infants has not been reduced (3,10,16,17). The main risk factor for ROP is the prematurity itself (18). Since the exposure to high oxygen concentration is known to be contributory to the Paediatric Anaesthesia 2001 11: 131±133

Stereospecific effects of d- and l-pentazocine on contractions of the mouse vas deferens

The effects of the d- and l-isomers of pentazocine were compared to that of racemic pentazocine on contractions of the mouse isolated vas deferens. L-pentazocine inhibited electrically evoked contractions of the mouse vas deferens (MVD) in a dose-dependent manner (ID50 0.37 +/- 0.04 microM). In contrast, d-pentazocine augmented field stimulated contractions dose-dependently; per cent increases in contractions at 10 and 30 microM were 57.8 +/- 18.0 and 98.0 +/- 15.1%, respectively. Racemic pentazocine produced an intermediate effect between the two isomers. The effect of 1-pentazocine was antagonized by naloxone, whereas that of d-pentazocine was not. L-pentazocine did not effect the response of the MVD to exogenous norepinephrine at any concentration tested, while d-pentazocine depressed the response of the MVD to exogenous norepinephrine at one dose (0.3 microM). These findings demonstrate that d- and l-pentazocine produce opposite effects on the MVD. The effects of l-pentazocine are opioid mediated, while those of d-pentazocine are not. In the racemic mixture the opposing effects of the two isomers modulate each other, resulting in a diminished effect.