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Biomedical subjects

D C Galletly

Publications and source records attributed to D C Galletly.

At least 55 records · Page 3Linked to original sources
PubMed1994

Leg elevation compared with Trendelenburg position: effects on autonomic cardiac control.

We have studied in 12 healthy male volunteers the effects of three different body positions (10 degrees head-down tilt, horizontal supine and supine with 50-cm leg elevation from the hip) on the spectral components of heart rate and finger plethysmographic amplitude variability. We have demonstrated the absence of any statistically significant difference in any measure of variability in the time of frequency domain for both of these measures between the three positions. We conclude that neither leg elevation nor 10 degrees head-down tilt is associated with any significant alteration in the dominant parasympathetic cardiac control in comparison with the resting supine position.

Adult↗
PubMed1993

Effect of inhalation of 30% nitrous oxide on spectral components of heart rate variability in conscious man.

1. Periodicities in cardiac interbeat interval may be resolved into discrete frequency components by applying Fourier analysis to heart rate time series. Low-frequency components (< 0.15 Hz) are believed to be under parasympathetic and sympathetic control, whereas a higher frequency component in phase with respiration is believed to be entirely parasympathetic. The ratio of the power in the low-/high-frequency spectrum gives an estimate of sympathetic/parasympathetic balance. 2. This study examined, using heart rate variability spectral analysis, the cardiac autonomic effects of breathing 30% N2O in normal subjects. While supine, the inhalation of N2O caused a significant fall in high-frequency power and a rise in the low-/high-frequency spectrum. During air breathing, tilting caused a significant rise in the mean blood pressure, heart rate, low-frequency power and low-/high-frequency spectrum. During N2O breathing, tilting caused a rise in the heart rate and the mean blood pressure, but no significant alteration in the power of individual spectral components. During tilting, the heart rate, the low-frequency and low-/high-frequency spectrum were less when breathing N2O than when breathing air. 3. These observations are consistent with the effect of N2O being an enhanced sympathetic balance of sinoatrial control, with the primary effect being through reduced parasympathetic tone. Enhanced sympathetic dominance of heart rate variability was seen on standing while subjects breathed air, but this effect was blunted with N2O.

Administration, Inhalation↗
PubMed1993

The influence of the H1 and H2 receptor antagonists, terfenadine and ranitidine on the hypotensive and gastric pH effects of the histamine releasing drugs, morphine and tubocurarine.

Morphine and tubocurarine may release histamine by direct mast cell degranulation which may result in systemic effects such as cutaneous flushing, local wheal and flare formation and hypotension. This randomised, double-blind study examined whether preoperative combined oral terfenadine (60 mg) and ranitidine (150 mg) attenuates the reduction in blood pressure and cutaneous flushing after the administration of tubocurarine and morphine in 60 patients undergoing elective gynaecological surgery. In addition, investigation was made of whether tubocurarine and morphine cause a significant decrease in gastric pH in comparison to the nonhistamine-releasing agents fentanyl and vecuronium. Patients were randomly assigned to one of three groups receiving either pre-operative terfenadine and ranitidine and intra-operative tubocurarine and morphine (group A); pre-operative placebo and intra-operative tubocurarine and morphine (group B); pre-operative placebo and intra-operative fentanyl and vecuronium (group C). Compared to group B, group A had less hypotension and tachycardia but no significant decrease in cutaneous flushing immediately following morphine and tubocurarine (p > 0.05). There were no significant differences in haemodynamic changes between the groups A and C. In those patients not pretreated with terfenadine and ranitidine (groups B and C), gastric pH decreased between 5 and 10 min following bolus administration of morphine and tubocurarine (group B), whereas patients receiving fentanyl and vecuronium (group C) had an increase in gastric pH. This suggests that histamine release following administration of morphine and tubocurarine is sufficient to increase gastric acidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-Blind Method↗
PubMed1993

A comparison of three ported cannulae available in New Zealand.

A comparison was made of the three 22-gauge ported intravenous cannulae available in New Zealand--Venflon 2, Vasofix Braunule and Insyte. All cannulae performed satisfactorily in terms of overall success of cannulation although significant differences were apparent in both clinical and laboratory performance. Anaesthetists' clinical preference was for Insyte and Venflon 2 brands, perceiving these to have greater ease of handling and better packaging. In a series of laboratory studies, Vasofix was found to have the highest flowrate, the fastest time to flashback and the lowest valve opening pressure. Insyte required the least force of penetration. Venflon 2 had the greatest margin of safety between pressure to inject through the port and pressure required to blow the syringe/port assembly apart. Potential problems were identified with the Insyte port valve mechanism.

Anesthesiology↗
PubMed1992

Relative effects of intrathecal administration of fentanyl and midazolam on A delta and C fibre reflexes.

The effects of fentanyl and midazolam, administered intrathecally, on somatosympathetic reflexes evoked by tibial nerve stimulation were investigated in 12 anaesthetized and paralysed dogs. Fentanyl depressed both the C and A delta fibre evoked reflexes in a dose ratio of approx 1:2. In contrast, midazolam had a greater effect on A delta compared with C fibre reflexes; while A delta reflexes were abolished by a total dose of 3 mg midazolam, C fibre reflexes were depressed by only 50%. The effect of fentanyl was reversed by naloxone (2 mg, i.v.) and that of midazolam by flumazenil (1 mg, i.v.). The results suggest that fentanyl and midazolam have different relative effects on A delta and C fibre pathways.

Anesthesia, Spinal↗
PubMed1992

Midazolam sedation reversed with flumazenil for cardioversion.

Midazolam was used for anaesthesia in 20 patients undergoing cardioversion; 10 received flumazenil, which caused immediate rapid reversal of anaesthesia, and these patients maintained SpO2 greater than 95%, breathing air, within 5-10 min. In contrast, patients in the placebo group were still partially sedated and required oxygen therapy for up to 2 h to maintain a normal SpO2. Arterial pressure, but not heart rate, also was greater in the flumazenil group in the recovery period.

Adult↗
PubMed1992

Heart rate periodicities during induction of propofol-nitrous oxide-isoflurane anaesthesia.

This study examined the variation in cardiac inter-beat interval during induction of anaesthesia with propofol and subsequent inhalation anaesthesia with nitrous oxide and isoflurane. In comparison with preoperative control values, heart rate variability was reduced by anaesthesia and there was a complex, but consistent, pattern of R-R interval change during induction. Immediately after propofol 2 mg kg-1, high frequency heart rate oscillations were replaced by low frequency oscillations (0.05 Hz). Subsequently, with decreasing propofol and deepening nitrous oxide-isoflurane anaesthesia, high frequency components returned towards, although not reaching, control values; low and, to a greater extent, mid range (0.1-Hz) frequency components remained reduced. We postulate that these alterations are consistent with an immediate but transient post-induction ventilatory depression, subsequent decrease in efferent sympathetic activity and reduction in baroreflex responsiveness. R-R interval analysis is suggested to be a useful tool in the evaluation of autonomic function during anaesthesia.

Adolescent↗
PubMed1992

Accuracy of text entries within a manually compiled anaesthetic record.

We have examined the accuracy of text entries within a manually compiled anaesthetic record by comparing the record of the anaesthetist with that of an observer, present throughout the procedure but whose sole purpose was the documentation of perioperative events. Eighty-six items of information were analysed for accuracy from 197 records. The mean proportion of omissions was 35% and the mean proportion of incorrect entries was 3.4%. Where no entry should have been made, the mean proportion of unwarranted entries was 1%. Accuracy varied according to the information contained; however, omissions were common for preoperative status, fluids, tourniquet use, aspects of monitoring, local anaesthesia and intraoperative problems. The most consistently accurate information was the description of the patient and that relating to intraoperative i.v. drug use. Inaccuracy was common for the majority of sites on the record, irrespective of their reflecting on the anaesthetist's performance. We suggest, therefore, that the reason for this inaccuracy of data was not related principally to anaesthetists' defensiveness, but may reflect their attitudes to the record's value and response to inadequacies in its design. The observed deficiencies in recording accuracy may affect patient safety during future anaesthesia and has relevance to medico-legal and epidemiological research.

Anesthesia↗
PubMed1992

Betamethasone-induced resistance to neuromuscular blockade: a comparison of atracurium and vecuronium in vitro.

Steroids induce resistance to neuromuscular blocking drugs. Betamethasone-induced resistance to vecuronium has been demonstrated in vitro, and a presynaptic site of interaction has been suggested. This study investigated whether atracurium is similarly affected. Rat phrenic nerve-hemidiaphragm preparations were bathed in a physiologic solution, and one-half were exposed to betamethasone (1 mumol/L). Dose responses were recorded for atracurium (8-13 mumol/L) and vecuronium (2-12 mumol/L) for control and betamethasone-treated preparations. In comparison to control, the betamethasone groups had significantly less depression of muscle contraction force at all concentrations of atracurium (P = 0.0004) and vecuronium (P = 0.002). The calculated ED50 (50% depression of muscle contraction force, expressed as mean +/- SEM) for atracurium was 8.83 +/- 0.62 mumol/L for controls and 11.19 +/- 0.54 mumol/L for betamethasone-treated preparations. The calculated ED50 for vecuronium was 4.72 +/- 0.41 mumol/L for controls and 6.84 +/- 0.66 mumol/L for betamethasone-treated preparations. Betamethasone therefore increased the ED50 for atracurium by 27% and vecuronium by 45%; however, the magnitudes of these differences were not significant (P = 0.74) between the neuromuscular blocking agents. These results indicate that betamethasone-induced resistance to nondepolarizing neuromuscular blockade affects both atracurium and vecuronium to similar degrees in vitro.

Animals↗
PubMed1991

Hypnotic and anaesthetic action of thiopentone and midazolam alone and in combination.

This study examined the interaction between i.v. administered midazolam and thiopentone on the loss of response to verbal command ("hypnosis") and the loss of response to transcutaneous electrical stimulation of the ulnar nerve ("anaesthesia") in patients presenting for minor elective surgery. Dose-response curves for thiopentone and midazolam individually and in combination were determined using the two end-points in 300 unpremedicated patients. For hypnosis a highly significant (P less than 0.001) supra-addictive (synergistic) interaction was found, the combination having 1.8 times the expected potency of the individual agents. Although midazolam failed to produce anaesthesia in the dose range used, the dose of thiopentone required to produce anaesthesia was reduced by 50% in the presence of midazolam. The mechanism of interaction and the potential role of benzodiazepine-barbiturate combinations are discussed and the observed synergistic anaesthesia interaction is used to explain the potentially dangerous combination of benzodiazepines with other potent CNS depressants such as barbiturates and alcohol.

Adult↗
PubMed1991

Interaction between betamethasone and vecuronium.

A possible interaction between betamethasone and vecuronium was examined in 20 rat phrenic nerve-hemidiaphragm preparations. Ten preparations were bathed in a physiological solution with betamethasone 1 mumol litre-1 added and, after a 30-min period were exposed to vecuronium at concentrations of 4, 6, 8 and 10 mumol litre-1 with vecuronium free washings between each exposure. Ten control experiments were performed also using a betamethasone-free bathing solution. In comparison with control, the betamethasone group had significantly (P = 0.0008) less depression of muscle contraction (twitch) force at all concentrations of vecuronium. The calculated ED50 (50% depression of muscle contraction force) was 5.65 mumol litre-1 for controls and 7.39 mumol litre-1 for betamethasone-pretreated preparations. This study confirms our previous clinical observations that an interaction occurs between vecuronium and betamethasone which is characterized by resistance to neuromuscular block.

Animals↗
PubMed1991

Acute tolerance from benzodiazepine night sedation.

The hypothesis that benzodiazepine night sedation causes acute tolerance to benzodiazepine sedation given the following morning was examined in six volunteers in a double blind, randomised, crossover study. Before each of three study days, subjects received midazolam 15 mg or flunitrazepam 2 mg or placebo as oral night sedation. They were then given intravenous midazolam 5 mg the following morning and the resulting sedative effects examined, using an observers sedation scale and a psychomotor test battery (critical flicker fusion frequency, digit-symbol substitution, reflex time, tapping test and a visual analogue sedation scale). Although a consistent pattern emerged with the greatest degree of sedation following the placebo night sedation and the least degree of sedation following the midazolam, with flunitrazepam intermediate, no statistically significant differences were present between the three treatment groups. The results indicate that single use of benzodiazepine night sedation is not an important influence on benzodiazepine requirements for intravenous sedation.

Adult↗
PubMed1991

Anaesthesia system errors.

A simple schema of anaesthesia system error evolution is described. This was used, with a modified critical incident technique, as a framework for data gathering and error analysis. The outline places emphasis on recovery pathways and, in addition to causal and contributory factors, was able to identify many factors which aided or hindered the processes of error detection, diagnosis and management. On average, 8.1 factors were identified which were considered to have significantly influenced the genesis and evolution of each reported error. Differences were apparent in the type of factors which determined error production and aspects of the recovery sequence. The described schema is suggested to be of value for data generation, and as a tool for discussion as part of anaesthesia quality assurance.

Accident Prevention↗
PubMed1991

The anaesthetic record: a confidential survey on data omission or modification.

A confidential survey was conducted among medical practitioners in New Zealand with a stated interest in anaesthesia to ascertain the proportion of those currently engaged in anaesthetic practice (thought to be approximately 325), who knowingly omit or alter undesirable physiological parameters from the anaesthetic record. Two hundred and forty-five replies were received from currently active anaesthetists. The reported frequency of occasional data omission or falsification was 55%. Those anaesthetists who intentionally manipulated data were more likely to be dissatisfied with their current anaesthetic record form, to view the record as an intraoperative distraction and less likely to perceive the record as being important for the use of future anaesthetists. There was no correlation between data manipulation and concerns over the medicolegal uses of the record.

Anesthesia Department, Hospital↗
PubMed1991

Level of consciousness on arrival in the recovery room and the development of early respiratory morbidity.

An audit review of 16,065 patients undergoing operative procedures under general anaesthesia was carried out to examine the relationship between early postoperative respiratory complications and the level of consciousness of patients on arrival in the recovery room. In patients aged over ten years, the incidence of respiratory complications was significantly (P less than 0.005) related to the level of consciousness independent of ASA grade or age. Since the level of consciousness of patients arriving in the recovery room could be modified by changes to anaesthetic practice it is concluded that a significant reduction in respiratory complications might be possible if anaesthetists used general anaesthetic techniques which returned patients awake to the recovery room.

Age Factors↗
PubMed1991

Is caffeine withdrawal the mechanism of postoperative headache?

This study examined the hypothesis that headache after general anesthesia is related to a caffeine withdrawal state. Two hundred eighty-seven patients undergoing minor elective procedures under general anesthesia were studied. Four to six hours after anesthesia each patient completed a questionnaire assessing his or her own alcohol, tobacco, and caffeine consumption, and the occurrence of postoperative side effects. A highly significant difference was found between the caffeine consumption of patients with and without preoperative (P = 0.0035) and postoperative (P less than 0.0001) headache. Logistic regression analysis of trend between headache and caffeine consumption suggested that with each 100-mg increase in caffeine consumption, there was a 12% increase in the odds of headache developing in the immediate preoperative period (P less than 0.0066) and a 16% increase in the odds of postoperative headache developing (P less than 0.0001). No relationship was found between headache and the patients' age, sex, usual frequency of headache, consumption of alcohol or nicotine, or the anesthetic agents or adjuvants used. It is concluded that postoperative headache is related to caffeine intake and that this relationship is explained, at least in part, by a perioperative caffeine withdrawal syndrome.

Adult↗