Can pediatric anesthesiologists detect an occluded tracheal tube in neonates?

UNLABELLED: To determine whether pediatric anesthesiologists can reliably detect occluded tracheal tubes, 18 pediatric anesthesiologists who were blindfolded and fitted with earplugs manually ventilated the lungs of 16 neonates. Consent was obtained from the parents of the neonates. All auditory signals from the monitors were silenced. Six conditions were studied (for 3 min each) in random order: three models of Ayre's t-piece with the Jackson Rees modification and two fresh gas flows (FGF) (2 and 6 L/min). During each condition, the tracheal tube was clamped at five predetermined but randomized times. The volume/pressure relationships of the three t-piece models were determined. Tube occlusions were detected more frequently at a low FGF (82%) than at a high FGF (64%) (P < 0.001). Experienced anesthesiologists (>8 yr experience) detected occlusions (83%) more frequently than less experienced (<2 yr experience) anesthesiologists (63%) (P < 0.027). There was no interaction between FGF and experience. The type of circuit did not affect the detection rate. We conclude that during isolated hand ventilation with the t-piece, pediatric anesthesiologists can detect >80% of occluded tubes provided they use a low FGF or have >8 yr experience, but only 60% of occluded tubes at high FGF or if they have <2 yr experience. IMPLICATIONS: Hand ventilation of the lungs in neonates has been used to detect changes in respiratory compliance, but laboratory models have failed to demonstrate its usefulness. We determined that pediatric anesthesiologists could detect 83% of tracheal tube occlusions in neonates if either the fresh gas flow was 2 L/minor the pediatric anesthesiologist was experienced (> 8 yr).

Buried Kirschner wire fixation in digital fusion.

There have been many methods utilized to fixate the proximal interphalangeal joints of the lesser digits for osseous fusion. The authors present a clinical retrospective review of a new alternative of buried Kirschner wire fixation. A review of forty-six Kirschner wires (30 cases) is presented.

The incidence of masseter muscle rigidity after succinylcholine in infants and children.

To determine whether the incidence of masseter muscle rigidity is affected by the anaesthetic induction sequence, we prospectively studied for ten months the anaesthetic course in 5,641 infants and children who received muscle relaxation to facilitate tracheal intubation. The anaesthetic induction sequence consisted of intravenous sodium thiopentone (STP) 5 mg.kg-1 alone, halothane induction alone 1-4%, or halothane followed by STP. Inhalational inductions with halothane included nitrous oxide and oxygen. Tracheal intubation was facilitated by either intravenous succinylcholine (Sch) at least 1.5 mg.kg-1 or by a non-depolarizing muscle relaxant. The induction sequence and all episodes of MMR were recorded. Ninety percent of the patients received Sch and 10% received a non-depolarising agent. Of those who received Sch, 88% (5,064 patients) were anaesthetised with STP and 12% (607 patients) were anaesthetised with halothane alone or halothane followed by STP. Masseter muscle rigidity was defined clinically by the transient inability to distract the mandible from the maxilla such that the mouth could not be opened or could only be opened with force. No children anaesthetised with STP followed by Sch developed MMR. One child (0.9%) developed MMR after halothane and Sch and two developed MMR after halothane, STP and Sch (0.4%). The incidence of MMR after Sch was less with STP than with halothane alone or with halothane and STP (P < 0.025). The peak CPK values in the three children who developed MMR were 17,580 IU.L-1 after halothane and Sch, and 7,280 IU.-1 and 3,273 IU.-1 after halothane, STP and Sch. There was no evidence of MH reactions in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Accuracy of end-tidal PCO2 measurements using a sidestream capnometer in infants and children ventilated with the Sechrist infant ventilator.

To determine the accuracy of end-tidal PCO2 (PETCO2) measurements analyzed with a sidestream capnometer in infants and children whose lungs were ventilated with a Sechrist infant ventilator and an Ayre's t-piece, we compared PETCO2 measurements obtained from the proximal (PETCO2-p) and distal (PETCO2-d) ends of the tracheal tube to arterial PCO2 (PaCO2) in 37 healthy infants and children between 1.3 and 24.5 kg. Both PETCO2-p and PETCO2-d accurately approximated PaCO2, however, the mean (+/- SD) arterial to end-tidal PCO2 difference (delta(a-ET)PCO2) was significantly greater with proximal (1.27 +/- 1.54 mmHg) than with distal sampling (0.64 +/- 1.64 mmHg) (P less than 0.01). In the subgroup of patients who weighted less than 12 kg, the delta(a-ET)PCO2 using proximal gas sampling (1.94 +/- 1.29 mmHg) was also significantly greater than it was using distal sampling (0.74 +/- 1.31 mmHg) (P less than 0.001). We conclude that although statistically different, both proximal and distal estimates of PETCO2 provide acceptable estimates of PaCO2 in healthy infants and children who are ventilated with a Sechrist infant ventilator and an Ayre's t-piece system.

Fresh gas formulae do not accurately predict end-tidal PCO2 in paediatric patients.

To determine the fresh gas flow (FGF) requirements in paediatric patients, we measured the FGFs needed to maintain distal end-tidal PCO2 (PETCO2) values at 30 and 38 mmHg in patients weighing between 3.8 and 20 kg ventilated with either a Sechrist Infant Ventilator IV-100B or an Air-Shields Ventimeter and a Mapleson D circuit. The FGF requirement was 500 ml.kg-1.min-1 to maintain a PETCO2 of 30 mmHg and 250 ml.kg-1.min-1 to maintain a PETCO2 of 38 mmHg when minute ventilation greater than or equal to FGF. When these formulae were used in a subsequent group of similar patients, a wide variation in PETCO2 measurements were obtained. We conclude that the safest and most accurate approach to determine the FGF requirement of paediatric patients is to continuously monitor the PETCO2 in each patient and to adjust the FGF accordingly.

Anterior fontanelle pressure responses to tracheal intubation in the awake and anaesthetized infant.

In order to define the changes in intracranial pressure which occur during tracheal intubation in young infants, a Ladd transducer was used to monitor anterior fontanelle pressure (AFP) non-invasively in awake (group 1, n = 14) and anaesthetized (group 2, n = 10) infants during intubation of the trachea. Heart rate and systolic arterial pressure were also recorded. In quiet, undisturbed infants, AFP (mean +/- SEM) was similar in groups 1 (9.6 +/- 0.5 mm Hg) and 2 (8.7 +/- 0.8 mm Hg); with crying, AFP increased significantly in both groups. During laryngoscopy in group 1, AFP increased to 33.5 +/- 3.6 mm Hg, which was significantly greater than in the quiet infant, but did not differ significantly from measurements in the crying infant. In group 2, AFP increased significantly to 15.8 +/- 18 mm Hg during laryngoscopy. This increase was significantly less than the group 1 response. Neither heart rate nor systolic arterial pressure changed significantly in either group during laryngoscopy--when compared with measurements in the quiet state. It was concluded that AFP increases significantly during intubation and during crying in the infant. The response to intubation is only partially attenuated by the prior administration of general anaesthesia.

End-tidal PCO2 measurements sampled at the distal and proximal ends of the endotracheal tube in infants and children.

To determine whether the site of gas sampling affects end-tidal gas measurements in pediatric patients, end-tidal PCO2 was measured continuously from the distal and proximal ends of the endotracheal tube in 60 infants and children ventilated with an Air-Shields Ventimeter and a partial rebreathing circuit. These data were compared with simultaneous arterial PCO2 measurements. In infants and children weighing greater than or equal to 12 kg, both distal and proximal end-tidal PCO2 values approximated arterial PCO2 measurements. In infants and children weighing less than 12 kg, however, only distal end-tidal PCO2 measurements approximated arterial PCO2 measurements. It is concluded that in infants and children weighing less than 12 kg, accurate end-tidal measurements can be obtained only from the distal end of the endotracheal tube.

Anesthesia for pediatric neurological and neuromuscular diseases.

Children with neurological and neuromuscular diseases often present anesthetic problems in the perioperative period. The anesthetic technique can play a significant role in altering the state of the brain during neurosurgical procedures through effects on the cerebral circulation and metabolism. Pre-existing neuromuscular disease may also have specific anesthetic implications such as cardiorespiratory involvement (eg, myotonia dystrophica), the potential for drug interactions (eg, myasthenia gravis) or abnormal responses to commonly used drugs (eg, malignant hyperthermia). In this review, the perioperative anesthetic considerations in a number of common neurological and neuromuscular conditions in the pediatric patient are discussed.

Anaesthetic considerations for separation of omphalo-ischiopagus tripus twins.

Anaesthesia for the separation of conjoined twins requires a multi-disciplinary team approach. We describe the anaesthetic management of a single-stage separation of 2 1/2-year-old omphalo-ischiopagus tripus conjoined twins. The successful 17 1/2-hour operation was conducted by five anaesthetists and 38 surgeons and nurses. Two major problems were encountered: massive blood loss in both twins (requiring transfusions of more than five and seven times their blood volumes) and a transient decrease in core temperatures after separation.

Anaesthetic considerations in Down's syndrome: experience with 100 patients and a review of the literature.

Down's Syndrome (Trisomy 21, T21) occurs in approximately 0.15 per cent of live births. In addition to the stigmata of the syndrome, other congenital defects are frequently found in these patients. Cardiac lesions are particularly prominent. To determine the complications associated with anaesthesia and surgery we examined the records of 100 consecutive patients (58 males, 42 females) who underwent surgery with general anaesthesia during a two year period, from March 1978-March 1980. In addition to the cardiac lesions, the low birth weight of Trisomy 21 infants, increased susceptibility to infections, atlanto-occipital dislocation, and reduced central nervous system catecholamine levels might be expected to result in an increased incidence of complications. This study of 100 patients with Trisomy 21 (T21) indicates that the incidence of complications is low. However, the anaesthetist must understand the pathophysiology of T21 in order to provide optimal anaesthetic care.

Anaesthesia for cerebral arteriovenous malformations in children.

Between 1966 and 1982, 46 patients underwent a total of 50 craniotomies for exploration and excision of cerebral arteriovenous malformations (AVMs) at The Hospital for Sick Children, Toronto. Thirty-three of these patients presented with intracranial haemorrhage, 13 of whom required emergency operations. Thirteen patients underwent elective surgery after investigation of a variety of medical complaints. In most cases, anesthesia was induced with thiopentone followed by a muscle relaxant to facilitate intubation. Anaesthesia was maintained with nitrous oxide and oxygen, a muscle relaxant, halothane and/or an intravenous narcotic, and positive pressure ventilation. In 60 percent of patients, blood loss was less than 20 per cent of estimated blood volume (EBV) although four children lost more than 50 per cent of their EBV. There were no deaths during operation. Controlled hypotension was employed in 30 operations to improve operating conditions during excision of deep-seated AVMs. Blood loss was similar in the non-hypotensive group, but these procedures tended to be of shorter duration. The advantages of various hypotensive techniques in children undergoing operations for cerebral AVMs are discussed and current anaesthetic management at The Hospital for Sick Children is described.

Anaesthetic management of arteriovenous malformations of the vein of Galen.

Arteriovenous malformations of the vein of Galen, though rare, are associated with a significant mortality. The anaesthetic management of patients with this defect during surgery may be complicated by massive blood loss and congestive heart failure. Four patients under 18 months of age underwent craniotomies for arteriovenous malformations of the vein of Galen. Since two required a second craniotomy for ligation of residual feeding vessels, there were six procedures in the four patients. Average blood loss per procedure was estimated at 126 per cent of blood volume. One patient died during operation and one had an intra-operative cardiac arrest. Both of these patients had associated cardiac failure. In the presence of a compromised myocardium, sudden blood loss or attempts at induced hypotension may result in inadequate diastolic perfusion of the heart and precipitate cardiac arrest. Consequently, these patients should be maintained in a euvolaemic state with transfusion and attempts at controlled hypotension should be avoided.

The uptake and excretion of nitrous oxide in the newborn.

In the newborn, the uptake of nitrous oxide into the alveolus is very rapid, as is the fall in alveolar levels following withdrawal of the agent. During recovery relatively large volumes of nitrous oxide are excreted in the first minute, after which the excretion rate rapidly declines, most of the gas having been eliminated.

The effect of splenectomy on circulatory adjustments to hypoxaemia in the anaesthetized dog.

Six intact and seven splenectomized dogs were subjected to a similar degree of hypoxaemia while under light anaesthesia and artificial ventilation. In the intact animals, heart rate, cardiac output, myocardial contractility and oxygen consumption were increased as a result of hypoxaemia; oxygen transport was not affected. In the splenectomized animals the changes in cardiac output and myocardial contractility were small, and oxygen availability was decreased.

A technique for measuring regional myocardial blood flow and its application in determining the effects of hyperventilation and halothane.

A method for measuring regional myocardial blood flow with a polarographic hydrogen-clearance technique, and its experimental application in dogs, are described. Under pentobarbitone anaesthesia, flow to the superficial (3 mm) and deep (8 mm) layers of the left ventricle was not significantly different. Neither hypocapnia (PaCO2 = 24 mm Hg) nor halothane significantly altered differential distribution of blood flow to the superficial and deep layers of the myocardium. Hypocapnia was followed by a fall in myocardial blood flow (MBF) associated with increased myocardial vascular resistance (MVR). Administration of halothane 0.5 per cent at normal levels of PaCO2 led to a fall in MBF of approximately 20 per cent with no significant changes in MVR.

Advantages of the prone position for neurosurgical procedures on the upper cervical spine and posterior cranial fossa in children.

The authors have reviewed the charts of 107 patients undergoing 119 surgical procedures in the prone position for posterior fossa or upper cervical lesions. The intraoperative complications encountered include cardiac arrhythmia, respiratory complications, cardiac arrest, hypothermia, air embolus and technical difficulties. In all but three children the problems were minor and easily remedied. The use of controlled ventilation appears to reduce blood loss, permits excellent relaxation of the exposed tissues and had some anesthetic advantages.