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Biomedical subjects

D J Steward

Publications and source records attributed to D J Steward.

At least 55 records · Page 3Linked to original sources
PubMed1984

Noninvasive arterial hemoglobin oxygen saturation versus transcutaneous oxygen tension monitoring in the preterm infant.

We found that results from a transcutaneous arterial hemoglobin oxygen-saturation monitor correlated well with those from a co-oximeter. The monitor was not disturbed by differing hematocrit levels, the presence of fetal hemoglobin, or hypotension. We also found that the results of simultaneous transcutaneous arterial hemoglobin oxygen saturation (StcaO2) and transcutaneous oxygen tension (PtcO2) monitoring were predictably correlated over a wide range of hemoglobin saturations in preterm infants. When StcaO2 was between 80% and 95%, PtcO2 was at a safe level of 40 to 80 torr in 94% of the patients studied. StcaO2 monitoring as an index of arterial oxygenation has several advantages for the preterm infant.

Arteries↗
PubMed1982

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.

Adolescent↗
PubMed1982

Linear airway dimensions in children: including those from cleft palate.

Linear airway dimensions from incisor teeth to vocal cords were measured from radiographs. Normal children were slightly taller and heavier than children being treated for cleft palate and had significantly longer upper airway dimensions. Tracheal length was measured in 50 normal children breathing spontaneously under general anaesthesia and was found to correlate best with body weight. Strong positive correlation with height was also found. Data from normal children in these two studies were used to calculate the distance from lips to mid-trachea to determine optimal length for a tracheal tube. Previously published data on airway lengths in children are reviewed.

Adolescent↗
PubMed1982

Treatment of segmental tracheomalacia and bronchomalacia by implantation of an airway splint.

A silastic reinforced marlex mesh splint was inserted surgically to support a collapsing airway in 3 children with tracheomalacia and 1 with bronchomalacia. The operation was well tolerated and no complications occurred. The splint successfully eliminated symptoms of airway collapse in all children. Its effect on airway growth is not yet certain. This method is applicable to patients with tracheomalacia in whom vascular suspension does not eliminate collapse and for those with bronchomalacia in whom pulmonary resection might otherwise be necessary.

Bronchi↗
PubMed1982

Myocardial pH during regional ischemia: evaluation of a fiber-optic photometric probe.

The relationship between the decrease in intramyocardial extracellular pH and the degree of stenosis of the left anterior descending (LAD) coronary artery was studied in eight dogs pretreated with propranolol. Intramyocardial pH was measured with a miniature glass pH electrode and with a new photometric pH probe that uses fiber-optic filaments to measure the color change of an indicator substance in a small permeable chamber. The LAD was cannulated and perfused from the axillary artery. Cannula flow was measured with an electromagnetic flow probe, and regional myocardial blood flow (RMBF) was measured with radioactive microspheres before and at the end of a period of critical stenosis, 2/3 reduction of flow, or total occlusion of the LAD cannula. In the region of the glass electrode, the mean RMBF (+/-SE) decreased by 16.3 +/- 3.3, 52.7 +/- 7.3, and 84.8 +/- 6.5% during the three levels of stenosis, and the pH correspondingly decreased by 0.05 +/- 0.01, 0.29 +/- 0.10, and 0.94 +/- 0.17 units. In the region of the photometric probe, the RMBF decreased 19.1 +/- 1.3, 47.2 +/- 6.7, and 84.3 +/- 6.0%, and the pH decreased by 0.05 +/- 0.02, 0.14 +/- 0.04, and 0.76 +/- 0.18 units. There was no statistically significant difference between the two types of pH sensor.

Animals↗
PubMed1982

Effect of multidose cardioplegia and cardioplegic solution buffering on myocardial tissue acidosis.

Multidose administration of cardioplegic solution during cardiac operation is intended to maintain both electromechanical arrest of the heart and myocardial hypothermia as well as to remove accumulated metabolites of anaerobic glycolysis. This study was conducted to assess the effect of multidose infusion of three different types of cardioplegic solution on tissue acidosis during global myocardial ischemia. Three groups of five dogs each were placed on cardiopulmonary bypass and the aorta was cross-clamped for 3 hours. The hearts were maintained at a constant temperature (20 degrees C) and cardioplegic solution was infused at an initial dose of 500 ml and five supplementary doses of 250 ml administered every 30 minutes. Group 1 received a crystalloid solution weakly buffered with sodium bicarbonate, Group 2 received a blood-based solution, and Group 3 received a crystalloid solution strongly buffered with histidine (Bretschneider's solution). The buffering capacities of the solutions used in Groups 2 and 3 were 40 and 60 times, respectively, that of the solution used in Group 1. The average myocardial tissue pH at the end of 3 hours of ischemia was 6.54 +/- 0.07 in Group 1, 7.23 +/- 0.05 in Group 2, and 7.19 +/- 0.06 in Group 3 (Group 1 significantly lower than Groups 2 and 3). Multidose infusion of a cardioplegic solution with low buffering capacity was unable to prevent the progressive development of tissue acidosis during 3 hours of ischemia. However, the multidose infusion of either blood-based or crystalloid solutions with high buffering capacity completely prevented any further reduction of tissue pH after the first 30 minutes of ischemia.

Acidosis↗
PubMed1981

Anaesthetic experience using a standard technique for laryngeal surgery in infants and children.

A 12 year review is presented of 1922 anaesthetic experiences on 285 patients presenting for microlaryngeal operations at the Hospital For Sick Children, Toronto. The lesions treated were laryngeal growths, 198 cases (69.5 per cent): subglottic stenosis, 81 cases (28.4 per cent); and posterior laryngeal cleft, 6 cases (2.1 per cent). The anaesthetic technique consisted of topical analgesia with lidocaine spray (3 mg kg-1) and pharyngeal insufflation of halothane and methoxyflurane both 1-1.5 per cent in oxygen through a special channel in the blade of a Jako Pilling microlaryngoscope in spontaneously breathing patients. Arterial blood gases sampled after 15 and 40 minutes of anaesthesia showed Paco2 = 6.29 +/- 0.31 kPa (47.1 +/-2.39 torr) and 6.44 +/- 0.16kPa (278 +/- 36.2 torr) respectively. Surgical exposure of the larynx was good allowing for a shorter operative time with minimal perioperative complications, in only 94 (4.89 per cent) of the 1922 anaesthetics.

Adolescent↗
PubMed1980

Anaesthesia for day-care surgery: a symposium (IV). Anaesthesia for paediatric out-patients.

Out-patient surgery for infants and children offers the advantages of minimal emotional upset, less risk of infection, and fiscal economy. Many different operations can be done in the out-patient department and most children can be accepted for general anaesthesia for these operations. Preparation of the child is similar to that required for in-patient surgery. Premedication is unnecessary and contraindicated. A variety of techniques may be selected for induction of anaesthesia without unduly prolonging recovery. General inhalation anaesthesia with halothane is preferred for maintenance. Careful tracheal intubation should be utilized whenever indicated. Regional analgesia has many advantages over narcotic analgesics in the treatment of post-operative pain. A follow-up service should be provided.

Ambulatory Surgical Procedures↗
PubMed1980

Intramyocardial pH during elective arrest of the heart: relative effects of hypothermia versus potassium cardioplegia on anaerobic metabolism.

Using an intramyocardial pH needle probe (21 gauge) to monitor myocardial metabolism during ischemia, we determined the effect of potassium cardioplegia at both moderate and deep hypothermia. Five groups of 5 dogs each were placed on cardiopulmonary bypass and the pH probe was inserted approximately 10 mm into the left ventricular free wall. Cardiac ischemia was achieved by cross-clamping the ascending aorta at 37 degrees C (Group 1), 27 degrees C (Group 2), or 17 degrees C (Group 3). In the remaining two groups, aortic cross-clamping was followed by the infusion of 600 to 800 ml of potassium cardioplegic solution adjusted to cardiac temperatures of 27 degrees C (Group 4) or 17 degrees C (Group 5). In each group, myocardial temperature was maintained constant, electrical and mechanical activity observed, and pH recorded until a plateau was reached or for 3 hours. Our results show a progressive and significant decrease in the metabolic rate with reduction in temperature over the 37 degrees to 17 degrees C range. By abolishing contractile activity, potassium cardioplegia markedly reduces the rate of hydrogen ion accumulation at 27 degrees C, but at 17 degrees C the additive effect of cardioplegia is much less pronounced. These observations support the principle of reducing contractile activity to a minimum during elective arrest of the heart but indicate that potassium cardioplegia does little to further reduce the rate of anaerobic metabolism, as shown by the measurement of intramyocardial pH, under conditions of deep hypothermia.

Animals↗
PubMed1980

Regional analgesia for postoperative pain in pediatric outpatient surgery.

Of 156 children undergoing elective inguinal herniotomy under general anesthesia, 81 also had a regional nerve block using Bupivacaine. All were treated as outpatients and recovery was assessed by postanesthetic room nurses and by interrogating the parents as to the child's behavior at home. It was concluded that the use of supplemental regional anesthesia reduced the general anesthetic requirements and the need for postoperative analgesics, thereby providing more rapid recovery to normal activity.

Ambulatory Surgical Procedures↗