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Biomedical subjects

A R Wolf

Publications and source records attributed to A R Wolf.

At least 19 recordsLinked to original sources
PubMed2002

Rapid skin anaesthesia using high velocity lignocaine particles: a prospective placebo controlled trial.

BACKGROUND: Local anaesthetic creams (EMLA and Ametop) are used widely to provide pain free intravenous cannulation. However, they take a minimum of 45 minutes to become effective. AIMS: To evaluate a prototype device, dermal Powderject lidocaine (DPL), that delivers high velocity lignocaine particles into the skin. METHODS: A total of 132 children (aged 4-12 years) were randomised to receive either a sham delivery or a delivery of DPL on the skin at the antecubital fossa, or back of hand. Pain of intravenous cannulation was assessed four minutes later using self reporting behaviours and blinded observation with standard pain assessment tools. The trial was designed to measure both efficacy of skin anaesthesia and potential skin damage with increasing driving pressure of the device (30 or 40 bar), and different lignocaine particle sizes (<38 micrometer or 38-53 micrometer) in a block randomised fashion. RESULTS: A total of 128 patients were evaluable. There was a trend towards improved anaesthesia at higher device pressures at the antecubital fossa with both self reporting and blinded observation. Acceptable analgesia was achieved in 90% of patients for high pressure at both particle sizes compared to 60% and 40% for the sham device using self reporting measures. The observed differences using the blinded observer were similar: 90% v 20% (40 bar and small particles v sham), and 80% v 40% (40 bar and large particles v sham). At the back of hand the differences between active and sham devices were not significant. The device was well tolerated and not associated with pain on deployment. One patient had mild petechiae and oedema after deployment (Draize score of 3). CONCLUSIONS: This prototype device appears to provide significant skin anaesthesia at the antecubital fossa, but not at the back of hand. The device is not painful to use and causes only minor short term skin changes.

Anesthesia, Dental↗
PubMed2001

Post-operative recovery after inguinal herniotomy in ex-premature infants: comparison between sevoflurane and spinal anaesthesia.

We prospectively studied the post-operative recovery profile of 28 ex-premature infants undergoing inguinal herniotomy. All infants had a post-conceptual age of less than 46 weeks at the time of surgery and were randomized to receive either sevoflurane (group 1, 14 patients) or spinal anaesthesia (group 2, 14 patients). All patients received supplemental caudal analgesia before skin incision. Cardiorespiratory function was continuously recorded in all patients before and after surgery. A blinded observer analysed each paired recording for predefined episodes of apnoea, hypoxaemia or bradycardia and the reports were used to compare the two groups. Spinal anaesthesia was attempted unsuccessfully in four patients in group 2. Five patients in group 1 demonstrated an 'excess' number of episodes (median 4, range 3-12) of clinically silent post-operative cardiorespiratory complications. ('Excess' in our study was defined as a 3-fold or greater increase in the number of post-operative episodes of bradycardia or apnoea relative to pre-operative occurrence). Three of these patients had pre-existing abnormal respiratory function and accounted for 80% of the episodes (26/32) of post-operative bradycardia and all five episodes of post-operative apnoea identified. All episodes of bradycardia and apnoea were temporally unrelated. None of the remaining patients in group 2 demonstrated an unacceptable number of post-operative cardiorespiratory complications. Our limited study suggests that general anaesthesia with an inhalational agent such as sevoflurane may induce or unmask abnormalities of cardiopulmonary function in predisposed infants. Spinal anaesthesia may be preferable but it is potentially stressful for the infant and associated with a clinically significant failure rate.

Anesthesia, Spinal↗
PubMed2000

Reducing stress responses in the pre-bypass phase of open heart surgery in infants and young children: a comparison of different fentanyl doses.

High-dose opioids are advocated for paediatric cardiac surgery to suppress stress responses but they can produce unwanted side effects. There are no data on the dose-dependent effects of opioids on the stress response on which to base rational opioid administration. We conducted a dose ranging study on 40 children less than 4 yr undergoing elective open heart surgery using one of five fentanyl doses: 2, 25, 50, 100 or 150 micrograms kg-1 before surgery. The standardized anaesthetic also included pancuronium and isoflurane. Blood samples were taken at induction, before incision, after sternotomy, immediately before, and at the end of cardiopulmonary bypass. Patients in the 2 micrograms kg-1 group had significant rises in prebypass glucose (P < 0.01), pre- and post-bypass cortisol (P < 0.01), and pre- and post-bypass norepinephrine (P < 0.01). No significant rise occurred in glucose, cortisol and catecholamines in any of the higher dosage groups. Patients in the 2 micrograms kg-1 group had significantly higher mean systolic blood pressure (P < 0.02) and heart rate (P < 0.04). A balanced anaesthetic containing fentanyl 25-50 micrograms kg-1 is sufficient to obtund haemodynamic and stress responses to the pre-bypass phase of surgery. Higher doses of fentanyl (100 and 150 micrograms kg-1) offer little advantage over 50 micrograms kg-1, and can necessitate intervention to prevent hypotension.

Anesthesia, General↗
PubMed1999

Pain, nociception and the developing infant.

The study of paediatric pain and the provision of safe but reliable analgesia for all age groups has become a central issue in paediatric anaesthesia. For the practising paediatric anaesthetist, this represents a major challenge: the developing infant is not a single discrete entity but one that changes constantly with increasing maturity of individual organs. Recent developments in both basic and clinical sciences has given valuable insights into this process, giving the clinician a firm basis to provide analgesia at all ages. This review looks at some of the most interesting recent developments in this field.

Analgesia↗
PubMed1998

Modifying infant stress responses to major surgery: spinal vs extradural vs opioid analgesia.

Twenty-six infants due to undergo major abdominal or thoracic surgery under general anaesthesia were randomized to receive additional analgesia with group A) spinal/epidural analgesia; B) epidural analgesia or C) opioid analgesia with fentanyl. We wished to determine if spinal analgesia followed by epidural analgesia might result in more complete control of cardiovascular or stress responses than the other two treatment groups. Heart rate and blood pressure were recorded at five min intervals throughout surgery. Blood samples were taken for measurement of catecholamines and whole blood sugar on induction, 45 min after skin incision and at the end of surgery. Heart rate rose significantly at the start of surgery in groups B and C but not group A. Systolic blood pressures were higher in group C compared to A and B. The rise in plasma glucose concentrations was significantly different between the groups in the order C > B > A (P < 0.05). A similar trend was seen in the plasma adrenaline and noradrenaline concentrations but this failed to achieve significance due to the limited sample size.

Abdomen↗
PubMed1998

Changes in blood-gas tensions during apnoeic oxygenation in paediatric patients.

We report changes in arterial blood-gas tensions for up to 5 min of apnoeic oxygenation in 26 anaesthetized paediatric patients (21 children, five infants). Changes in oxygen and carbon dioxide tension were greatest in the first minute of apnoeic oxygenation. In subsequent minutes, rates of change in gas tension were approximately constant. The rate of decline in oxygen tension (31 (95% confidence interval (CI) 20.1-42.2) mm Hg min-1) was more than three times that reported in studies in adults. The rate of increase in carbon dioxide tension (4.2 (95% CI 3.7-4.7) mm Hg min-1) was similar to that reported in adults. After successful preoxygenation, oxygen tension remained greater than 290 mm Hg in all children (age > 1 yr) throughout the study. This was not the case in infants. We found no correlation between changes in blood-gas tensions and age or weight of patients. The small number of infants studied showed rapid decreases in oxygen tension which if sustained would be expected to limit the safe duration of apnoeic oxygenation, unlike adults where apnoeic oxygenation is limited by hypercapnia. Extrapolation of our results suggests that when preoxygenation has been successful, apnoeic oxygenation could continue safely in children for at least 10 min. Infants may become hypoxic after only 2 min.

Age Factors↗
PubMed1996

Recovery after desflurane anaesthesia in the infant: comparison with isoflurane.

We have studied 20 infants, aged 2.5-8 weeks, undergoing general anaesthesia for pyloromyotomy with either desflurane or isoflurane. Patients were anaesthetized with equivalent 1 MAC values for age and agent. A blinded observer recorded times to breathing, swallowing, movement, extubation and side effects after discontinuation of the agent. Recovery times in the desflurane group were significantly shorter than in the isoflurane group. The times to swallowing, movement and extubation in the desflurane group were 3.89 (SD 2.4) min, 5.33 (4.95) min, 7.5 (4.53) min, respectively, and 8.82 (2.40) min, 10.73 (3.93) min, 13.45 (4.20) in the isoflurane group. In addition, postoperative apnoea was documented in the isoflurane group but not in those infants receiving desflurane. There was no laryngospasm after extubation in either group. We conclude that desflurane possesses useful characteristics for recovery conditions in the infant and may be particularly useful in the ex-premature infant prone to apnoea and ventilatory depression.

Anesthesia Recovery Period↗
PubMed1995

Ventilatory arrest after a fluid challenge in a neonate receiving s.c. morphine.

S.c. infusions of morphine have been advocated for postoperative analgesia in children, but experience with this technique is limited. We report a case in which an s.c. infusion of morphine given after operation to a neonate failed to provide acceptable analgesia until the child had been adequately rehydrated. However, restoration of peripheral perfusion with a fluid challenge was followed by sudden ventilatory arrest which required resuscitation and naloxone infusion. This report emphasizes the dangers of giving morphine by a peripheral route in the dehydrated or hypovolaemic infant.

Analgesics, Opioid↗
PubMed1993

Pain relief for infants undergoing abdominal surgery: comparison of infusions of i.v. morphine and extradural bupivacaine.

We have undertaken a prospective, randomized double-blind study to compare extradural bupivacaine infusions with i.v. morphine infusions for postoperative analgesia in 32 infants younger than 4 yr undergoing abdominal surgery. "Sham" extradural or i.v. catheters were used to maintain the blinded nature of the study. Both techniques provided adequate analgesia for most of the 36-h postoperative period; differences in the pattern or quality of the analgesia were not detected. Patients in the i.v. morphine group were significantly more sedated; this was accompanied by slower ventilatory frequencies (26.7 (SD 1.8) b.p.m.) compared with the extradural group (33.6 (1.3) b.p.m.). Similarly, oxygen saturation was significantly less (P < 0.01) in patients receiving morphine (medians and quartiles of 94.0 (93-96)% compared with 96.0 (93-96)%). Mean systolic arterial pressure was similar in the two groups and there were no life-threatening complications. The lack of sedation was troublesome in three patients in the extradural group.

Abdomen↗
PubMed1993

Effect of extradural analgesia on stress responses to abdominal surgery in infants.

We studied 40 children younger than 4 yr having elective abdominal surgery under general anaesthesia supplemented with either systemic opioids or extradural bupivacaine. Venous blood samples were obtained before tracheal intubation to measure baseline concentrations of adrenaline, noradrenaline, glucose, ACTH and cortisol. Additional samples were obtained 45 min after the start of surgery, at the end of surgery, 1 h and 24 h after the end of surgery. Plasma concentrations of bupivacaine were measured also in the extradural group at each sampling time. Both techniques provided acceptable analgesia, but the perioperative increases in adrenaline, glucose and ACTH were significantly greater in the opioid group. Noradrenaline concentrations decreased to less than baseline values in the extradural group and were significantly less than in the opioid group. The perioperative increase in cortisol was similar in the two groups, despite the differences in ACTH responses. Most responses returned to the baseline values within 24 h. Plasma bupivacaine concentrations remained within safe limits during the study, but systemic concentrations increased in some of the patients during postoperative infusion with 0.125% bupivacaine.

Abdomen↗
PubMed1992

Propofol and alfentanil in children: infusion technique and dose requirement for total i.v. anaesthesia.

We estimated the dose of propofol (initial dose followed by a stepped infusion) when given with two different infusion rates of alfentanil for total i.v. anaesthesia in 59 children aged 3-12 yr. Patients in series 1 (four groups) received an alfentanil loading dose of 85 micrograms kg-1 and an infusion of 65 micrograms kg-1 h-1. Patients in series 2 (groups 5 and 6) received an alfentanil loading dose of 65 micrograms kg-1 and infusion of 50 micrograms kg-1 h-1. Parents gave their informed consent. Premedication comprised temazepam 0.3 mg kg-1. Glycopyrronium 5 micrograms kg-1 was administered and anaesthesia induced and maintained with alfentanil (loading dose and infusion) followed by propofol (loading dose and three-stage manual infusion scheme). Suxamethonium 1 mg kg-1 was used to facilitate tracheal intubation and the lungs were ventilated artificially to normocapnia with 30% oxygen in air. Probit analysis was used to determine the dose requirement of propofol. In series 1, the ED50 was 6.0 mg kg-1 h-1 (95% confidence limits 5.5-6.2 mg kg-1 h-1) and ED95 8.6 (6.8-7.8) mg kg-1 h-1. Corresponding values for series 2 were ED50 7.5 (8.0-9.8) mg kg-1 h-1 and ED95 10.5 (9.6-13.1) mg kg-1 h-1.

Adult↗
PubMed1991

Combined morphine-bupivacaine caudals for reconstructive penile surgery in children: systemic absorption of morphine and postoperative analgesia.

We wished to determine if the addition of a small dose of morphine (0.05 mg.kg-1) to a caudal solution of 0.25% bupivacaine could extend the duration of analgesia after major reconstructive penile surgery and also to measure the systemic absorption of morphine after caudal injection. Thirty children undergoing reconstructive penile surgery received a caudal injection of 0.25% bupivacaine 0.75 ml.kg-1 with or without morphine 0.05 mg.kg-1. All patients awoke pain-free, but eight of the fifteen patients receiving bupivacaine alone required supplementary injections of opioid postoperatively, whereas none of the patients receiving the bupivacaine-morphine mixture required additional opioids. The incidence of side-effects was similar for the two groups. Morphine was absorbed rapidly after caudal injection to reach a peak plasma level of 21.2 (+/- 4.8) ng.ml-1 at ten minutes and then fell to 10.1 (+/- 3.8) ng.ml-1 at one hour and 4.1 (+/- 2.6) ng.ml-1 at three hours. These levels are low compared with plasma levels associated with systemic analgesia. We conclude that the extended duration of analgesia from morphine 0.05 mg/kg given caudally is due at least in part to specific spinal analgesia.

Analgesia, Epidural↗