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Biomedical subjects

J W Downing

Publications and source records attributed to J W Downing.

At least 19 recordsLinked to original sources
PubMed1989

Incidence of venous air embolism during cesarean section is unchanged by the use of a 5 to 10 degree head-up tilt.

One hundred healthy parturients were divided at random into two demographically similar groups and were positioned for cesarean section either horizontally or flexed 5 to 10 degrees head up, with a 15 degrees lateral tilt. A Doppler ultrasound transducer was positioned over the fourth intercostal space parasternally. Initially, two patients received spinal, three general, and 95 epidural anesthesia. Two patients subsequently needed general for failed epidural anesthesia. Changes in Doppler heart tones (greater than 15 sec duration) indicative of venous air embolism (VAE) were identified 15 times in 11 patients--seven in supine and four in head-up patients (no statistically significant difference). Six awake patients (three horizontal, three head-up) developed chest tightness or pain during surgery, but only one episode correlated with VAE. No patient developed breathlessness. Moderate hypotension (greater than 10% decrease in systolic arterial pressure [SAP]) occurred in seven of 11 (63.6%) patients with, and in 26 (29.2%) of 89 patients without, VAE (P less than 0.001). More severe hypotension (SAP less than 90 mm Hg) due to bleeding occurred once. We conclude that a modest (5-10 degrees) head-up position does not influence the occurrence of VAE in patients having cesarean section. An 11% incidence of clinically insignificant VAE, although low, is still worrisome, as even small air bubbles in the circulation are potentially harmful, especially if the foramen ovale is patent. VAE during cesarean section should be anticipated and the anesthetic management planned accordingly.

Adult↗
PubMed1987

Intravenous cannula fixing and dressing--comparison between the use of transparent polyurethane dressing and conventional technique.

A sterile, disposable, polyurethane intravenous catheter dressing (OpSite; Smith & Nephew), was compared with a conventional dressing for both convenience and cost. Despite lack of familiarity, the use of OpSite proved as easy and acceptable as the traditional non-sterile control method. OpSite was also as durable and would appear, on calculation, to be cheaper when intravenous therapy lasts longer than a day. OpSite is therefore recommended as the intravenous dressing of choice. Its use, or that of a similar sterile disposable product, should be considered mandatory for paediatric and other patients in whom sterility is vital, and in situations where intravenous infusion will continue for more than 24 hours.

Antisepsis↗
PubMed1987

Maternal deaths from neurological complications of hypertensive crises in pregnancy.

Fourteen maternal deaths from eclampsia or severe pre-eclampsia where disturbed cerebral function, as evidenced by prolonged unconsciousness, was given as the main cause of death are reviewed. Prolonged duration of seizures, hypotensive/hypoxic episodes, cerebral oedema and intracranial haematomas were most frequently identified as causative agents in the development of cerebral dysfunction. Failure to maintain an airway and iatrogenically induced hypotension were the two most important contributory factors to the patients' deaths. Management recommendations to prevent this type of maternal death are given.

Adult↗
PubMed1987

Cardiac and noncardiac malformations: observations in a population-based study.

A regional case-control study of congenital cardiovascular malformations (CCVMs) searches for all live-born infants in the community in whom the cardiac diagnosis has been confirmed by echocardiography, cardiac catheterization, surgery, or autopsy. Their families are studied in comparison to those of a representative sample of resident live-born infants. Detailed descriptions of noncardiac abnormalities are obtained from physician reports and maternal interviews expanded by medical record and death certificate data. Among 1,494 cases and 1,572 controls, chromosomal abnormalities, syndromes, heritable disorders, and suspect syndromes occurred with an overwhelming excess in cases (chromosomes, P less than 10(-4); syndromes/heritable disorders, P less than .005). Abnormalities affecting chromosomes 13, 18, and 21 constituted 93% of the cytogenetic defects. Syndromes and heritable disorders were of 39 types. Nonsyndromic abnormalities were three times more frequent in cases than in controls (P less than .005). Case excesses occurred for central nervous system malformations, eye disorders, major abdominal wall defects, and abnormalities of the alimentary and urinary tracts. Severe anomalies frequent among cases were those which also occur in certain recognized syndromes, and it is suggested that paired combinations of cardiac and other midline anomalies may represent "formes frustes" of syndromes with similar though variable phenotypic expressions. Cleft lip and palate, inguinal hernia, and lower limb anomalies occurred with equal frequency, suggesting their association with CCVMs by chance alone.

Chromosome Aberrations↗
PubMed1987

General anaesthesia in mothers with severe pre-eclampsia/eclampsia.

Twenty patients with severe pregnancy induced (PIH) or pregnancy aggravated (PAH) hypertension, undergoing general anaesthesia for Caesarean section were studied. All patients received a standard anaesthetic technique designed to control the potentially dangerous, reflex cardiovascular instability associated with laryngoscopy. The average increase in systolic arterial pressure (SAP) was 56.4 mm Hg following laryngoscopy and tracheal intubation.

Adolescent↗
PubMed1987

Fentanyl-droperidol supplementation of rapid sequence induction in the presence of severe pregnancy-induced and pregnancy-aggravated hypertension.

Twenty-six patients manifesting severe pregnancy-induced (PIH) or pregnancy-aggravated (PAH) hypertension who presented for emergency Caesarean section under general anaesthesia were studied. All patients came from a previously identified high risk group--namely greater than 25 yr, multiparous and with diastolic arterial pressures sustained at greater than 120 mm Hg. Our standard accelerated induction technique for the management of severely hypertensive mothers was modified to include the use of fentanyl and droperidol before induction. This modification of the induction sequence produced a clinically significant amelioration of the reflex sympathetic hypertensive response to laryngoscopy and intubation in most mothers receiving antihypertensive therapy, without apparent deleterious effect in the immediate postoperative period to those neonates unaffected by intrauterine asphyxia.

Adjuvants, Anesthesia↗
PubMed1987

Fresh gas flow requirements using the ADE anaesthetic system during late pregnancy.

Thirty-two pregnant patients at term undergoing elective Caesarean section were ventilated with a non-co-axial ADE anaesthetic system (E mode) supplied with fresh gas flows (FGF) of either 70 or 100 ml kg-1 min-1, on a random basis. Ventilation with an FGF of 70 ml kg-1 min-1 produced mean PaCO2 and PE' CO2 values of 6.48 +/- 1.15 kPa and 6.41 +/- 0.76 kPa, respectively. Patients were thus hypercapnic, which contrasts with the normocapnia achieved using an FGF of 100 ml kg-1 min-1 via the ADE system (E mode) (PaCO2 5.07 +/- 0.7 kPa; PE' CO2 4.83 +/- 0.46 kPa) (mean values +/- SD). The latter FGF is therefore recommended for the pregnant patient at term when using a Mapleson E system such as the Humphrey ADE apparatus.

Adolescent↗
PubMed1987

Cisternal cerebrospinal fluid concentrations of morphine following intrathecal and epidural administration in the baboon.

Eleven baboons, anaesthetised with ketamine, had catheters introduced into the cisterna magna. Morphine was injected at lumbar level intrathecally in six and epidurally in five. Cisternal CSF was sampled hourly and the morphine concentration measured using a high pressure liquid chromatograph. In two cases following intrathecal injection peaks of 180 ng/ml at 4 hours, and 2,200 ng/ml at 3 hours were detected. In the latter case there was associated error in sampling therefore this baboon had a repeat injection four weeks later. The maximum level of morphine obtained then was 139 ng/ml at 4 hours. In the epidural group peaks of 113 ng/ml and 53 ng/ml at 1 hour were measured in 2 baboons and 27 ng/ml at 6 hours in a third. In all six other baboons following either procedure no morphine was detected in the cisterna. We conclude that morphine injected either intrathecally or epidurally in primates does migrate centrally in varying quantities. This finding would seem to have some bearing on the unpredictability of reported episodes of respiratory depression following intraspinal morphine.

Animals↗
PubMed1987

Comparison of midazolam and thiopental for rapid sequence anesthetic induction for elective cesarean section.

Sixty healthy mothers undergoing elective cesarean section received at random either midazolam 0.2 mg/kg or thiopental 3.5 mg/kg with succinylcholine 1 mg/kg for rapid sequence intravenous anesthetic induction. Maintenance of anesthesia was identical in all patients: 50:50 N2O in oxygen, halothane 0.5% and pancuronium 0.05 mg/kg. Hemodynamic responses were similar, as were the biochemical status of mothers and infants, and maternal to fetal blood gas/acid base gradients. Correlation between maternal arterial and fetal (umbilical venous/arterial) pH, PCO2 and base excess values were statistically better with midazolam. However, 1-min Apgar minus color (A-C) scores less than 5/8 (representing "severe" neonatal depression) were recorded in five infants after midazolam, three of whom required tracheal intubation, and one whose mother was given thiopental. This difference reached statistical significance (P less than 0.05). It is concluded that midazolam is less suitable than thiopental for anesthetic induction in patients undergoing cesarean section.

Anesthesia, Obstetrical↗
PubMed1986

Halothane and the liver.

Explore the source record for details and available documents.

Chemical and Drug Induced Liver Injury↗
PubMed1986

The lower oesophageal sphincter and the anaesthetist.

Pulmonary aspiration of gastric contents during induction of, or emergence from, anaesthesia poses hazards for both surgical and obstetric patients requiring urgent operations. Little emphasis has been placed on the importance of the lower oesophageal sphincter in relation to regurgitation and aspiration. This is especially important since anaesthetic drugs have been known to both decrease and increase lower oesophageal sphincter (LOS) tone. Any drug that will decrease tone will increase the incidence of gastric oesophageal reflux while drugs that increase tone may decrease this hazard. This review outlines the problem of acid aspiration in relation to the LOS and the various drugs which may influence LOS pressure.

Anesthesia, General↗
PubMed1986

Single lever Humphrey A.D.E. low flow universal anaesthetic breathing system. Part I: Comparison with dual lever A.D.E., Magill and Bain systems in anaesthetized spontaneously breathing adults.

The single lever Humphrey A.D.E. anaesthetic system, in both coaxial and parallel (non-coaxial) forms, has recently been introduced. In principle the system offers efficient "universal" function by combining the advantages of Mapleson A, D and E systems. A within-patient comparison of its function in the Mapleson A mode (lever up) in spontaneously-breathing anaesthetized subjects was made to that of the original two lever A.D.E., the Magill (Mapleson A) and the Bain (Mapleson D) systems. The coaxial and parallel single lever A.D.E. systems functioned identically to each other and to the original two lever A.D.E. system, a mean fresh gas flow (FGF) of 51 ml X kg-1 X min-1 causing minimal rebreathing. Under identical conditions, the mean FGF required to just cause rebreathing increased to a mean of 71 ml X kg-1 X min-1 and 150 ml X kg-1 X min-1 with the Magill and the Bain systems respectively. With the single lever system, the switch to its Mapleson E mode for controlled ventilation involves the selection of the only alternative lever position (lever down) without further adjustment. The function and practical advantages in this E mode are presented in Part II.

Adolescent↗
PubMed1986

Single lever Humphrey A.D.E. lowflow universal anaesthetic breathing system. Part II: Comparison with Bain system in anaesthesized adults during controlled ventilation.

A clinical trial involving ten anaesthetized adult patients was conducted during controlled ventilation using the Humphrey A.D.E. system in the Mapleson "E" mode (lever down). With each patient acting as his or her own control, the parallel (non-coaxial) and coaxial versions of the single lever Humphrey A.D.E. system were compared, using capnography, to the Bain system (Mapleson D/E). All three systems behaved similarly with predictable patient normocarbia when a fresh gas flow of 70 ml X kg-1 X min-1 was used. The A.D.E. system has the added advantage that the switch from controlled to spontaneous ventilation (or vice versa) is achieved quickly and simply. Spontaneous, assisted or automatic controlled ventilation could be instituted at any time merely by the appropriate lever position.

Adult↗
PubMed1986

The cricoid yoke--a device for providing consistent and reproducible cricoid pressure.

An instrument is described which, when used during the accelerated induction technique, ensures that consistent and adequate cricoid pressure can be applied. Mothers undergoing general anaesthesia for elective Caesarean section were studied in order to illustrate the clinical application of the instrument. The consequences to intubating conditions of applying adequate cricoid pressure, and an assessment of the instrument's control over the incidence of regurgitation during operation were investigated.

Adult↗