Inhaled Volatiles for Status Asthmaticus, Epilepsy, and Difficult Sedation in Adult ICU and PICU: A Systematic Review

OBJECTIVES

Inhaled volatile anesthetics support management of status asthmaticus (SA), status epilepticus (SE), and difficult sedation (DS). This study aimed to evaluate the effectiveness, safety, and feasibility of using inhaled anesthetics for SA, SE, and DS in adult ICU and PICU patients.

DATA SOURCES

MEDLINE, Cochrane Central Register of Controlled Trials, and Embase.

STUDY SELECTION

Primary literature search that reported the use of inhaled anesthetics in ventilated patients with SA, SE, and DS from 1970 to 2021.

DATA EXTRACTION

Study data points were extracted by two authors independently. Quality assessment was performed using the Joanna Briggs Institute appraisal tool for case studies/series, Newcastle criteria for cohort/case-control studies, and risk-of-bias framework for clinical trials.

DATA SYNTHESIS

Primary outcome was volatile efficacy in improving predefined clinical or physiologic endpoints. Secondary outcomes were adverse events and delivery logistics. From 4281 screened studies, the number of included studies/patients across diagnoses and patient groups were: SA (adult: 38/121, pediatric: 28/142), SE (adult: 18/37, pediatric: 5/10), and DS (adult: 21/355, pediatric: 10/90). Quality of evidence was low, consisting mainly of case reports and series. Clinical and physiologic improvement was seen within 1-2 hours of initiating volatiles, with variable efficacy across diagnoses and patient groups: SA (adult: 89-95%, pediatric: 80-97%), SE (adults: 54-100%, pediatric: 60-100%), and DS (adults: 60-90%, pediatric: 62-90%). Most common adverse events were cardiovascular, that is, hypotension and arrhythmias. Inhaled sedatives were commonly delivered using anesthesia machines for SA/SE and miniature vaporizers for DS. Few (10%) of studies reported required non-ICU personnel, and only 16% had ICU volatile delivery protocol.

CONCLUSIONS

Volatile anesthetics may provide effective treatment in patients with SA, SE, and DS scenarios but the quality of evidence is low. Higher-quality powered prospective studies of the efficacy and safety of using volatile anesthetics to manage SA, SE, and DS patients are required. Education regarding inhaled anesthetics and the protocolization of their use is needed.

Sedation and neurodevelopmental outcomes in PICU: Identification of study groups

BACKGROUND/AIMS

As little as 30 minutes of exposure to anesthetic and sedative agents may adversely affect the developing brain. Safe, humane management of critically ill infants requires the use of sedative agents, often for prolonged periods. We sought to identify two comparable groups of critical care patients who did or did not receive sedatives, with the aim of designing a long-term neurodevelopment follow-up study. This feasibility study aimed to determine if two comparable groups could be found.

METHODS

Infants with respiratory diagnoses having noninvasive ventilation without sedation (Group C) or intubation and ventilation with sedation (Group S) were identified by chart review. Charts of patients fulfilling the above inclusion criteria were searched for exclusion criteria including neurological disease, extreme prematurity, congenital cardiac disease, and genetic anomalies. Data were extracted to score pediatric severity of illness scores (PRISM and PELOD) for each patient. These scores were then compared using the absolute scores and by risk strata.

RESULTS

Group S included 33 patients and Group C had 39. The absolute PRISM and PELOD scores were different between groups. Comparing the groups in three risk strata (PRISM greater or less than 5 or 10), there were no significant differences between groups.

CONCLUSION

It is not possible to randomize infants to sedation or no sedation to investigate neurodevelopmental outcomes. This phase of the project aimed to determine the comparability of two groups of PICU patients. These findings indicate that these groups could be enrolled as exposed and control subjects in an outcomes study.

Enrollment challenges in multicenter, international studies: The example of the GAS trial

INTRODUCTION

Randomized trials are important for generating high-quality evidence, but are perceived as difficult to perform in the pediatric population. Thus far there has been poor characterization of the barriers to conducting trials involving children, and the variation in these barriers between countries remains undescribed. The General Anesthesia compared to Spinal anesthesia (GAS) trial, conducted in seven countries between 2007 and 2013, provides an opportunity to explore these issues.

METHODS

We undertook a descriptive analysis to evaluate the reasons for variation in enrollment between countries in the GAS trial, looking specifically at the number of potential subjects screened, and the subsequent application of four exclusion criteria that were applied in a hierarchical order.

RESULTS

A total of 4023 patients were screened by 28 centers in seven countries. Australia and the USA screened the most subjects, accounting for 84% of all potential trial participants. The percentage of subjects eliminated from the screened pool by each exclusion criterion varied between countries. Exclusion due to a predefined condition (H1) eliminated only 5% of potential subjects in Italy and the UK, but 37% in Canada. Exclusions due to a contraindication or a physician's refusal most impacted enrollment in Australia and the USA. The patient being "too large for spinal anesthesia" was the most commonly cited by anesthetists who refused to enroll a patient (64% of anesthetist refusals). The majority of surgeon refusals came from the USA, where surgeons preferred the patient to receive a general anesthetic. The percentage of approached parents refusing to consent ranged from a low of 3% in Italy to a high of 70% in the USA and Netherlands. The most frequently cited reason for parent refusal in all countries was a preference for general anesthesia (median: 43%, range: 32%-67%). However, a sizeable proportion of parents in all countries had a contrasting preference for spinal anesthesia (median: 25%, range: 13%-31%), and 23% of U.S. parents expressed concern about randomization.

CONCLUSION

The GAS trial highlights enrollment challenges that can occur when conducting multicenter, international, pediatric studies. Investigators planning future trials should be aware of potential differences in screening processes across countries, and that exclusions by anesthetists and surgeons may vary in reason, in frequency, and by country. Furthermore, investigators should be aware that the U.S. centers encountered particularly high surgeon and parental refusal rates and that U.S. parents were uniquely concerned about randomization. Planning trials that address these difficulties should increase the likelihood of successfully recruiting subjects in pediatric trials.

Differences in Blood Pressure in Infants After General Anesthesia Compared to Awake Regional Anesthesia (GAS Study-A Prospective Randomized Trial)

BACKGROUND

The General Anesthesia compared to Spinal anesthesia (GAS) study is a prospective randomized, controlled, multisite, trial designed to assess the influence of general anesthesia (GA) on neurodevelopment at 5 years of age. A secondary aim obtained from the blood pressure data of the GAS trial is to compare rates of intraoperative hypotension after anesthesia and to identify risk factors for intraoperative hypotension.

METHODS

A total of 722 infants ≤60 weeks postmenstrual age undergoing inguinal herniorrhaphy were randomized to either bupivacaine regional anesthesia (RA) or sevoflurane GA. Exclusion criteria included risk factors for adverse neurodevelopmental outcome and infants born at <26 weeks of gestation. Moderate hypotension was defined as mean arterial pressure measurement of <35 mm Hg. Any hypotension was defined as mean arterial pressure of <45 mm Hg. Epochs were defined as 5-minute measurement periods. The primary outcome was any measured hypotension <35 mm Hg from start of anesthesia to leaving the operating room. This analysis is reported primarily as intention to treat (ITT) and secondarily as per protocol.

RESULTS

The relative risk of GA compared with RA predicting any measured hypotension of <35 mm Hg from the start of anesthesia to leaving the operating room was 2.8 (confidence interval [CI], 2.0-4.1; P < .001) by ITT analysis and 4.5 (CI, 2.7-7.4, P < .001) as per protocol analysis. In the GA group, 87% and 49%, and in the RA group, 41% and 16%, exhibited any or moderate hypotension by ITT, respectively. In multivariable modeling, group assignment (GA versus RA), weight at the time of surgery, and minimal intraoperative temperature were risk factors for hypotension. Interventions for hypotension occurred more commonly in the GA group compared with the RA group (relative risk, 2.8, 95% CI, 1.7-4.4 by ITT).

CONCLUSIONS

RA reduces the incidence of hypotension and the chance of intervention to treat it compared with sevoflurane anesthesia in young infants undergoing inguinal hernia repair.

Neurodevelopmental outcome at 2 years of age after general anaesthesia and awake-regional anaesthesia in infancy (GAS): an international multicentre, randomised controlled trial

BACKGROUND

Preclinical data suggest that general anaesthetics affect brain development. There is mixed evidence from cohort studies that young children exposed to anaesthesia can have an increased risk of poor neurodevelopmental outcome. We aimed to establish whether general anaesthesia in infancy has any effect on neurodevelopmental outcome. Here we report the secondary outcome of neurodevelopmental outcome at 2 years of age in the General Anaesthesia compared to Spinal anaesthesia (GAS) trial.

METHODS

In this international assessor-masked randomised controlled equivalence trial, we recruited infants younger than 60 weeks postmenstrual age, born at greater than 26 weeks' gestation, and who had inguinal herniorrhaphy, from 28 hospitals in Australia, Italy, the USA, the UK, Canada, the Netherlands, and New Zealand. Infants were randomly assigned (1:1) to receive either awake-regional anaesthesia or sevoflurane-based general anaesthesia. Web-based randomisation was done in blocks of two or four and stratified by site and gestational age at birth. Infants were excluded if they had existing risk factors for neurological injury. The primary outcome of the trial will be the Wechsler Preschool and Primary Scale of Intelligence Third Edition (WPPSI-III) Full Scale Intelligence Quotient score at age 5 years. The secondary outcome, reported here, is the composite cognitive score of the Bayley Scales of Infant and Toddler Development III, assessed at 2 years. The analysis was as per protocol adjusted for gestational age at birth. A difference in means of five points (1/3 SD) was predefined as the clinical equivalence margin. This trial is registered with ANZCTR, number ACTRN12606000441516 and ClinicalTrials.gov, number NCT00756600.

FINDINGS

Between Feb 9, 2007, and Jan 31, 2013, 363 infants were randomly assigned to receive awake-regional anaesthesia and 359 to general anaesthesia. Outcome data were available for 238 children in the awake-regional group and 294 in the general anaesthesia group. In the as-per-protocol analysis, the cognitive composite score (mean [SD]) was 98.6 (14.2) in the awake-regional group and 98.2 (14.7) in the general anaesthesia group. There was equivalence in mean between groups (awake-regional minus general anaesthesia 0.169, 95% CI -2.30 to 2.64). The median duration of anaesthesia in the general anaesthesia group was 54 min.

INTERPRETATION

For this secondary outcome, we found no evidence that just less than 1 h of sevoflurane anaesthesia in infancy increases the risk of adverse neurodevelopmental outcome at 2 years of age compared with awake-regional anaesthesia.

FUNDING

Australia National Health and Medical Research Council (NHMRC), Health Technologies Assessment-National Institute for Health Research UK, National Institutes of Health, Food and Drug Administration, Australian and New Zealand College of Anaesthetists, Murdoch Childrens Research Institute, Canadian Institute of Health Research, Canadian Anesthesiologists' Society, Pfizer Canada, Italian Ministry of Heath, Fonds NutsOhra, and UK Clinical Research Network (UKCRN).

A comparison of three dose timings of methylprednisolone in infant cardiopulmonary bypass

Although commonly used in pediatric cardiopulmonary bypass (CPB) optimal dose and timing of steroid administration is unclear. We hypothesized that early administration of a commonly used dose of methylprednisolone given the evening before surgery (ultra-early) would be more effective in decreasing CPB-related inflammatory response than when given at induction of anesthesia (early) or in pump prime (standard).

This was a triple-arm, parallel, active control, superiority RCT including 54 infants <2 years old who were randomised to receive 30 mg/kg methylprednisolone at one of the 3 time points. Outcomes included alveolar-arterial oxygen gradient (AaDO2) during, 24, 48 and 72 hours post-CPB, IL-6, IL-8 and reduced (GSH) to oxidized (GSSG) glutathione ratio (pre-ultrafiltration on CPB, end-CPB and 24 hours), PICU length of stay (LOS) and ventilator days. Data were analysed using descriptive statistics and a random effects regression model.

The ultra-early group had higher Risk Adjusted Congenital Heart Surgery Score, lower age and longer CPB times than the other groups. No significant differences in AaDO2, IL-8, PICU LOS and ventilator days were observed between groups. Compared to the ultra-early group, the overall rise in IL-6 in the early and standard groups was lower, -27.8 pg/ml (95% CI -52.7,-2.9) and -35.3 pg/ml (95% CI -64.3,-6.34), respectively. GSH:GSSG was significantly lower in the standard group (-35.9; 95% CI -63.31,-8.5) at 24 hours post-CPB.

Ultra-early administration of methylprednisolone does not improve AaDO2 post-CPB, nor diminish cytokine release. Lower GSH:GSSG in the standard group suggests less oxidative stress. However despite statistical adjustments conclusions are limited by the unbalanced randomisation of the groups.

Extensive lower limb injuries in a child complicated by complex pain management and profound anemia

We describe a case of severe pain associated with extensive lower limb injures in a 5-year old, complicated by profound anemia in a Jehovah's Witness family. The study was carried out in a pediatric intensive care unit of a tertiary level university hospital. The patient was 5-year-old girl, with multiple open fractures and extensive soft tissue loss on her left foot and ankle due to a lawnmower injury leading to severe pain and profound anemia with management of the latter complicated by family beliefs. The interventions given were multi-modal pain management and treatment of severe anemia with avoidance of transfusion. A drop in hemoglobin from 11.6 g.dl(-1) at admission to a nadir of 4.3 g.dl(-1) on day 7 was observed. Effective pain control was achieved with nurse- and then patient-controlled analgesia plus adjuncts. Effective pain management and control of anxiety can be achieved by a multi-modal approach in young children. Profound anemia was treated without transfusion and without compromise of tissue healing.

Minimal exhaled nitric oxide production in the lower respiratory tract of healthy children aged 2 to 7 years

BACKGROUND

Exhaled nitric oxide (eNO) is elevated in inflammatory airway conditions, e.g. asthma. We measured eNO levels in normal preschool children for whom there is little data available and in whom the prevalence of asthma is high.

SUBJECTS AND METHODS

Fifty children, 2-7 years old, undergoing elective surgery, excluding airway procedures, were recruited. Children with known respiratory disease or acute viral infections were excluded. Gas for eNO measurement was collected in a non-diffusion bag via 1) the mask after inhalation induction of anesthesia, 2) endotreacheal tube (ETT) or laryngeal mask airway (LMA), and 3) during emergence. Measurement was off-line by chemiluminescent analyzer.

RESULTS

Mean eNO level by mask was 10.23 ppb (mean value+/-SD of 8.8-11.1 ppb) after induction and 8.35 ppb (mean value+/-SD of 5.9-10.8 ppb) on emergence. Mean eNO for the intubated group (n=25) was 0.75 ppb (mean value+/-SD of 0.4-1 ppb) (P<0.0001 vs mask); mean eNO for the LMA group (n=25) was 2.6 ppb (mean value+/-SD of 2-3.2 ppb), which differed from the mask (P<0.0001), and from ETT values (P<0.0001).

CONCLUSIONS

Most eNO is produced by the upper airway in healthy pre-school children. The lower airway constitutive eNO production is very low. The LMA does not completely isolate the upper airway and current mask collection techniques allow significant contamination of samples by sino-nasal eNO production in young children.

A case of propofol toxicity: further evidence for a causal mechanism

A 5-month-old boy required sedation after a cleft lip repair. He was sedated with propofol and intermittent fentanyl, requiring escalating doses over the subsequent 48 h. On the second post-operative day he developed a metabolic acidosis followed by multiple cardiac dysrhythmias, hepatic and renal failure. Propofol was stopped. His multisystem organ failure gradually resolved after initiation of charcoal haemoperfusion. Further investigation demonstrated an abnormality in acylcarnitine metabolism, similar to that found in one previous case report.

Management of postoperative chylothorax with nitric oxide: a case report

OBJECTIVE

To describe the use of inhaled nitric oxide in the management of refractory postoperative chylothorax.

DESIGN

Case report.

SETTING

A pediatric intensive care unit of a tertiary care children's hospital.

PATIENT

A neonate with refractory chylothoraces complicated by moderate pulmonary hypertension after a complicated arterial switch operation.

INTERVENTIONS

Administration of inhaled nitric oxide through a ventilator circuit.

MEASUREMENTS AND MAIN RESULTS

The institution of inhaled nitric oxide at 20 ppm resulted in a marked reduction in chest tube drainage and a decrease in echocardiographically estimated pulmonary artery pressure from 50%-75% systemic to 30%-50% systemic. Chest tube drainage doubled when the nitric oxide was decreased to 10 ppm and, again, dramatically decreased after raising nitric oxide back to 20 ppm. After 8 days of nitric oxide therapy, the chest tube drainage ceased. Nitric oxide therapy was successfully discontinued 19 days after initiation, with no recurrence of chylothorax. There was no effect of nitric oxide on systemic blood pressure. Methemoglobin levels while on NO remained <1.7%.

CONCLUSION

Consideration may be given to the use of inhaled nitric oxide in the therapy of refractory chylothoraces complicated by central venous hypertension.

Respiratory function in children during recovery from neuromuscular blockade

Residual neuromuscular blockade is a major risk factor for respiratory insufficiency. We examined the relationship between neuromuscular and respiratory function in 18 ASA I or II children aged 2-4 years. Lung function was measured by pneumotachography and transpulmonary pressure, neuromuscular transmission by first twitch response ratio (T1:T1) and train-of-four ratio (TOFR), before and at specific points in recovery from vecuronium paralysis. The tidal volume was directly related to maximal inspiratory pressure at occlusion (PIOCC), P < 0.001, whereas the minute ventilation (VE) was related to the respiratory drive (P0.1), P < 0.001. The best predictors of minute ventilation were the P0.1 (r = 0.57), and the TOFR (r = 0.62). PIOCC and P0.1 correlated closely (r = 0.889, P = 0.002) but TOFR and T1:T1 did not correlate with either. Our results show that the occlusion pressure measurements, P0.1 and PIOCC, were good predictors of both VE.kg-1 and respiratory work.

Use of adenosine in multiple doses for supraventricular tachycardia in an infant

The treatment of recurrent supraventricular tachycardia in a 3-week-old infant is described. Multiple doses of adenosine were used successfully to convert the dysrhythmia, without adverse effects or apparent tachyphylaxis.

Histamine release during cardiopulmonary bypass in neonates and infants

PURPOSE

Histamine release has been previously documented in adults and children during cardiopulmonary bypass (CPB). It has not been studied in neonates nor during deep hypothermic circulatory arrest (DHCA). Histamine effects could explain many perioperative complications of congenital cardiac surgery such as dysrhythmias and massive oedema. Therefore, documentation of histamine release in the perioperative period is of clinical importance. The source of histamine can be determined by measurement of tryptase which is released with histamine from mast cells but not basophils.

METHODS

Blood samples for histamine and tryptase were taken before and after specific events eg. cross-clamp removal, during anaesthesia and CPB in 14 infants and seven neonates undergoing complex congenital heart repairs and were analysed by commercial radioimmunoassays. Haemodynamic variables and pre and post-op weights were recorded to look for correlation between pathophysiological events and histamine release.

RESULTS

Histamine concentration decreased at the start of bypass (0.69 to 0.38 ng.ml-1 at five minutes, (P < .005). There were no changes associated with DHCA and a small rise with reventilation (P < 0.02). Histamine concentration was lower in neonates than in infants (P < 0.05) during CPB. Plasma histamine and tryptase concentrations did not correlate, suggesting histamine release was from basophils and not from mast cells. Haemodynamic variables did not correlate with histamine concentrations.

CONCLUSION

There was no major histamine release during CPB in infants and neonates. There was no relationship between histamine concentrations and clinical variables. Histamine released during CPB appears to come from basophils and may be a function of age.

Repeat epidural analgesia and unilateral block

The use of epidural analgesia has become so widespread in recent years that many women are now requesting repeat epidural analgesia for their second or subsequent labour. This study examines the incidence of problems at insertion and of inadequate block in 71 multiparae having second epidurals compared with 150 primiparae having their first epidural. Unilateral block occurred in 6.66% of primiparae and 18.3% of multiparae (P < 0.02). There was no association between difficulty of insertion of catheter, blood in needle/catheter or paraesthesia and unilateral blockade. Epidurals were inserted at a greater dilatation (P < 0.05) and there was a shorter time to delivery (P < 0.01) in the multiparous group. We conclude that unilateral block is thus more common in women receiving repeat epidurals.

Histamine release during paediatric cardiopulmonary bypass

Histamine release is part of the general inflammatory response and occurs during surgery and cardiopulmonary bypass (CPB) in adults. Few data are available for children. Histamine release was studied in 23 children undergoing CPB with standard anaesthetic and CPB techniques. Blood sampling was performed in relation to specific anaesthetic and surgical events, e.g., start of CPB, removal of aortic clamps, reventilation of the lungs. Plasma histamine was determined by a single isotope radioenzymatic technique. There was no consistent histamine release in the study population although there was an increase in plasma histamine concentration in some subjects after initiation of CPB (P < 0.05) and on removal of the aortic cross-clamp (P < 0.05). No correlation was demonstrated between histamine concentration and systolic arterial pressure, temperature, duration of CPB or cross-clamp time. Histamine concentration was positively correlated with heart rate.

Histamine release by morphine and diamorphine in man

Intravenous morphine and diamorphine are routinely used for postoperative analgesia but the relative histamine releasing abilities of these drugs have not been compared in man. Thirty-eight patients were randomly allocated to receive morphine (0.16 mg.kg-1) or diamorphine (0.08 mg.kg-1) after abdominal surgery. Blood samples for histamine were taken before, and at timed intervals after, opioid administration and analysed by an isotopic radioenzymatic technique. Haemodynamic parameters and pain scores were recorded before and after analgesic administration, and a series of eight basophil histamine release studies was also performed. Significant histamine release (plasma concentration > 2 ng.ml-1 or rise of > 700% baseline) occurred in 23.5% of the morphine group and 21.1% of the diamorphine group. Histamine was released earlier in those receiving diamorphine, but no significant change in haemodynamic parameters occurred, and no histamine release was demonstrated in the basophil histamine release studies. These findings suggest that morphine and diamorphine release histamine from mast cells rather than basophils.

Histamine release during paediatric cardiopulmonary bypass

Histamine release occurs during paediatric cardiopulmonary bypass at the time of removal of the aortic cross-clamp. Left atrial histamine levels are significantly (p less than 0.02) higher than right atrial levels at the time of reventilation of the lungs. These results suggest that histamine is released from the pulmonary vasculature following reperfusion.

Potentiation of atracurium neuromuscular blockade by enflurane: time-course of effect

This study was designed to determine the time required for potentiation of atracurium neuromuscular blockade after the introduction of enflurane. Ten ASA physical status I and II adults anesthetized with thiopental, nitrous oxide, and alfentanil were given 0.4 mg/kg atracurium besylate. The force of contraction of the adductor pollicis muscle in response to train-of-four stimulation of the ulnar nerve was recorded. When the first twitch (T1) of the train-of-four recovered to 10% of control, an atracurium infusion was started and adjusted to keep the level of blockade constant. After 15 min of stable blockade, 1.6%-1.7% end-tidal enflurane was started and maintained for up to 2 h. Venous blood samples were drawn and plasma atracurium concentrations were measured 15 min before and 0, 5, 10, 15, 30, 45, 60, 90, and 120 min after the introduction of enflurane. Atracurium plasma concentrations were 730 +/- 127 (SEM) ng/mL at time 0. During the first 30 min, no significant decrease in plasma levels occurred; but at 45 min, concentrations were only 67% +/- 8% of their initial value (P less than 0.01) and 48% +/- 2% at 120 min (P less than 0.01). This suggests that the interaction between enflurane and atracurium is time-dependent. Clinically, the interaction between atracurium and enflurane is negligible during procedures of less than 45 min.

Weaning from ventilation after cardiopulmonary bypass: evaluation of a non-invasive technique

Weaning of patients from IPPV after cardiopulmonary bypass (CPB) is usually monitored by frequent arterial blood gas analysis. Non-invasive monitoring has the advantage of providing continuous and instantaneous information and could reduce the frequency of arterial blood gas sampling. Twenty patients were studied to determine the reliability of capnometry and pulse oximetry in this situation. The effects of hypothermia and moderate haemodynamic instability were examined. A further 40 patients were then weaned using non-invasive monitoring. Correlation between PaCO2 and PETCO2 was 0.64-0.79 for the mass spectrometer and 0.67-0.81 for the infra-red analyser. No clinical problems arose. The detection rate for mild hypercarbia was 78.6 per cent and 50 per cent for hypoxia. Possible reasons for this are discussed. Once CO2 and O2 gradients are established, pulse oximetry and capnometry provide sufficiently reliable monitoring to enable weaning from IPPV, with the advantage of continuous display, and allow a reduction in the use of arterial blood gas analyses.

Relevance of histamine to the anaesthetist

Histamine is a widely distributed amine with many functions, both physiological and pathological. The anaesthetist may encounter histamine in several of these roles, many of which require further elucidation. Histamine research is involved in the investigation of release mechanisms and their modification, both having implications for the clinical situation.

Basophil histamine release studies in the evaluation of a new anaesthetic agent

Propofol (2,6-diisopropylphenol) has recently been introduced into clinical practice as an induction agent. This study evaluated the effect of propofol on basophil histamine release in 13 healthy subjects. No release was demonstrated in 11 subjects. Two subjects released histamine at the highest drug concentration, one also releasing at lower concentrations. Both subjects whose basophils released histamine in response to propofol were anaesthetists using the drug during the course of their practice.

Basophil histamine release. A study in allergy to suxamethonium

A patient who suffered a severe hypotensive episode after induction of anaesthesia, was subsequently found to show positive skin-test responses to suxamethonium. Investigation revealed that suxamethonium induced basophils from the patient to release histamine to an extent comparable to that found after exposure to anit-IgE. Basophils from control subjects showed no such response. Basophil histamine release may offer a useful approach to the investigation of adverse drug reactions.

Dysrhythmias following intravenous metoclopramide

A case is described in which administration of intravenous metoclopramide was twice followed by cardiac dysrhythmias. The literature is reviewed.