Intraoperative awareness due to malfunction of a Siemens 900B ventilator

A case of intraoperative awareness during a thoracotomy is described. The patient's recall coincided with an intraoperative period during which a Siemens 900B ventilator and a Siemens 952 isoflurane vaporiser were used. Subsequent assessment of this equipment with an anaesthetic agent analyzer revealed that, at the ventilator settings which had been used, the delivered anaesthetic vapour concentration varied greatly from the vaporizer settings. This problem eventually was traced to a malfunctioning inlet control valve on the ventilator. This complication may have been prevented if the end-tidal anaesthetic concentration had been monitored intraoperatively.     

Systemic lidocaine and human somatosensoryevoked potentials during sufentanil-isoflurane anaesthesia

The effect of systemically administered lidocaine on somatosensory evoked potentials (SSEPs) during general anaesthesia has not been widely reported. Knowledge of the influence of anaesthetic agents on evoked potentials assists in interpreting evoked potential waveforms. Accordingly, we studied the behaviour of cortical and subcortical (recorded at the second cervical vertebra) SSEPs after administration of intravenous lidocaine (3 mg.kg-1 bolus followed by infusion at 4 mg.kg-1.hr-1) during a sufentanil-based anaesthetic regimen in 16 patients undergoing abdominal or orthopaedic surgery. When compared to awake baseline recordings, the sufentanil-nitrous oxide, low-dose isoflurane anaesthetic depressed N1 amplitude by approximately 40% and prolonged latency by 10%. Fifteen minutes after establishment of this anaesthetic, the amplitude and latency of N1 were 1.13 +/- 0.56 microV and 19.81 +/- 1.63 msec, respectively. Within five minutes of adding lidocaine, amplitude decreased further to 0.84 +/- 0.39 microV (P = 0.001), while latency was extended to 20.44 +/- 1.48 msec (P = 0.01). Lidocaine did not affect cervical amplitude and prolonged latency only minimally. Despite the observed effects on amplitude and latency, SSEP waveforms were preserved and interpretable. Plasma lidocaine levels obtained at 5, 20, and 40 minutes after lidocaine were 5.17 +/- 1.33, 3.76 +/- 1.14, and 3.66 +/- 0.9 micrograms.dl-1, respectively. Our results indicate that systemically administered lidocaine at therapeutic plasma levels acts synergistically with a sufentanil-based anaesthetic to depress the amplitude and prolong the latency of SSEPs.     

High frequency jet ventilation via a tracheoscope for endobronchial laser surgery

Palliative surgery of malignant endobronchial tumours is associated with various anaesthetic risks. A technique is described using a neodymium:yttrium-aluminium-garnet (Nd:YAG) laser in combination with a special tracheoscope and high frequency jet ventilation (HFJV). The purpose of this technique is to provide separation of anaesthetic and surgical manipulations, good conditions of ventilation and easy access to the lungs for the surgeon. We present our experience with 14 adult patients in whom large endobronchial neoplasms were resected using this technique under intravenous anaesthesia and muscle relaxation. Careful perioperative monitoring and a good outcome allowed us to conclude that this set-up may contribute to improving efficiency and safety of endoscopic resections of endobronchial and/or endotracheal tumours.     

Baricity and the distribution of lidocaine in a spinal canal model

The role of the baricity of local anaesthetic solutions in determining the distribution of local anaesthetics injected into the subarachnoid space (and hence the level of anaesthesia) has been challenged. A recent study found no difference in the extent of cephalad spread of hyperbaric and isobaric solutions and concluded that density had no effect on the spread of local anesthetics. The present study, to determine the validity of this conclusion, utilized a spinal model filled with a “cerebrospinal fluid equivalent.” Following the injection of hyperbaric lidocaine, the local anaesthetic was most concentrated at the lower end of the column, whereas following the injection of isobaric solution the local anaesthetic was most concentrated around the site of injection. Therefore, baricity is an important determinant of local anaesthetic distribution in the subarachnoid space.     

Continuous spinal anaesthesia for abdominal surgery in a patient receiving amiodarone

The perioperative management of a 57-yr-old patient receiving chronic amiodarone therapy with a continuous spinal anaesthetic for a low anterior resection of the colon is discussed. The most appropriate anaesthetic technique for patients receiving chronic amiodarone therapy remains controversial, but the avoidance of general anaesthesia may be beneficial because of the risk of postoperative pulmonary failure. In this patient continuous spinal anaesthesia was slowly titrated to the desired level, coincident haemodynamic alterations were easily treated as they developed, and high serum local anaesthetic concentrations which occur with other regional anaesthetic techniques were avoided.     

Cardiac electrophysiology and conduction pathway ablation

Invasive cardiac electrophysiological (EP) testing and transcatheter ablation are new methods available for the diagnosis and treatment of complex dysrhythmias. The purpose of this review is to familiarize anaesthetists with these procedures. The information presented combines a literature review with the authors’ experience. This article reviews normal cardiac conduction, tachycardia pathogenesis, principles of cardiac EP study and techniques of conduction pathway ablation. The anaesthetic considerations, including the choice of anaesthetic agent, monitoring problems, drug interactions, special methods ofdysrhythmia termination in the EP lab, and complications specific to these procedures, are detailed. Balanced general anaesthesia or monitored anaesthesia care (MAC) sedation with benzodiazepines, propofol and narcotics are acceptable. Several conclusions can be drawn: transcatheter ablation is an effective treatment for many reentry tachycardias; anaesthetic assistance for this procedure will increasingly be needed; anaesthesia can easily be provided without influencing accurate EP testing; overdrive pacing is the method of choice for terminating tachydysrhythmias in the EP lab.     

Intrathecal midazolam reduces isoflurane MAC and increases the apnoeic threshold in rats

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - The purpose of this study was to examine the anaesthetic requirement of intrathecal midazolam in a dose-response fashion in...     

Caesarean section and phaeochromocytoma resection in a patient with Von Hippel Lindau disease

This report describes the anaesthetic management of a women with a term gestation, Von Hippel Lindau disease (VHLD), and a phaeochromocytoma, scheduled for a combined phaeochromocytoma resection and Caesarean section. Von Hippel Lindau disease is characterized by diffuse haemangioblastomas of the central nervous system (CNS) and viscera. It is also associated with phaeochromocytomas and renal cell carcinomas. Patients frequently have asymptomatic spinal cord and intracranial pathology. The patient and her fetus presented a challenge because of the anaesthetic restrictions imposed by VHLD, and her pregnancy. She was also at risk of developing malignant hypertension from the phaeochromocytoma. The patient was not a candidate for regional anaesthesia because of the possibility of spinal cord haemangioblastomas. She had received adrenergic blockade with phentolamine (total 30 mg a day) and propranolol (total 40 mg a day) since the 27th wk of gestation in order to control hypertension secondary to the phaeochromocytoma. General anaesthesia was administered with aggressive management of hypertension with adrenergic blockers (labetalol 1.0 mg · kg^?1 and esmolol 0.75 mg · kg^?1) and sodium nitroprusside 1.5 μg · kg^?1 (total). Before delivery of the baby, opioids, which could have resulted in a fetus with CNS depression, were avoided. After delivery, opioids (sufentanil 0.4 ng · kg^?1 hr^?1) were used to limit the use of inhalational anaesthesia which may contribute to uterine atony. Postoperative pain was managed with an intravenous narcotic infusion. Both patients had uneventful postoperative courses.     

Multicore myopathy in a patient with anhidrotic ectodermal dysplasia

We report a patient with multicore myopathy, a rare myopathy not previously reported in the anaesthetic literature. It is characterised by a myopathy of proximal muscles which tends to follow a benign course but may be associated with a severe form of cardiomyopathy. The myopathy is related to central core disease so these patients should be considered to have a potential for developing malignant hyperthermia. Complicating this case was an associated anhidrotic type of ectodermal dysplasia resulting in the absence of sweating, febrile episodes, recurrent pulmonary infections, conical and missing teeth, scaly skin and fine, sparse hair. The patient had a scoliosis repair which was uneventful but died three weeks later following a major pulmonary aspiration while on the ward. The cause of the aspiration is thought to have been unsuspected laryngeal incompetence associated with ectodermal dysplasia, the myopathy involving his bulbar muscles and analgesic medication.     

Convulsions after enflurane in a schizophrenic patient receiving neuroleptics

A schizophrenic patient suffered from an episode of unexpected grand mal seizure following an enflurance anaesthetic for biopsy of an orbital lesion. The seizure was brief and subsided spontaneously. An assessment of the anaesthetic technique and a thorough neurological examination which included a CT scan and an EEG, failed to demonstrate any obvious cause for the convulsion. The patient was not an epileptic and was receiving neuroleptic drugs preoperatively for the treatment of schizo-phrenia. A synergistic role of enflurane and neuroleptic drugs in producing seizure activity in this patient is a distinct possibility. Caution is therefore recommended when administering enflurane to patients on neuroleptic drugs.     

Nimodipine decreases the minimum alveolar concentration of isoflurane in dogs

Nimodipine is a calcium antagonist that binds with high affinity to neuronal membranes. It is a potent cerebrovasodilator and has been demonstrated also to affect neurotransmitter synthesis and release. Because patients undergoing surgery for intracranial aneurysms are frequently receiving nimodipine, the authors determined the MAC of isoflurane in six dogs before and during three infusion doses of nimodipine (0.5, 1.0 and 2.0 micrograms.kg-1.min-1). MAC was also determined in five dogs before and during infusion of the drug vehicle (10 microliters.kg-1.min-1). Nimodipine produced a reduction in MAC from 1.47 +/- 0.33% to 1.19 +/- 0.18, 1.15 +/- 0.18 and 1.15 +/- 0.09% during infusions of nimodipine 0.5, 1.0 and 2.0 micrograms.kg-1.min-1, respectively (P less than 0.05). Infusion of drug vehicle alone produced no change in MAC (1.39 +/- 0.15%). This reduction in anaesthetic requirement by nimodipine may be due to its effect on neurotransmission. Adjustments in anaesthetic dosage may be necessary in patients receiving nimodipine.     

Anaesthetic management of a child with Bartter’s syndrome

We report the anaesthetic management of an eight-year-old asthmatic boy with Bartter’s syndrome who had bilateral orchidopexy with caudal epidural analgesia. Bartter’s syndrome is a rare congenital disorder characterized by hypokalaemic hypochloraemic metabolic alkalosis, hyperaldosteronism, hyperreninaemia and hyperplasia of the juxtaglomerular apparatus of the kidneys. Characteristically, although these patients are normotensive they may be hypovolaemic. They may have unstable baroreceptor responses and show marked resistance to vasopressors. Hence, fluid, acid-base and electrolyte imbalances along with haemodynamic instability pose particular problems in their anaesthetic management. Previous case reports have described the management of these patients with general anaesthesia, our patient had his orchidopexy with caudal epidural analgesia using plain bupivacaine 0.5%. The patient was haemodynamically stable throughout surgery and was comfortable with caudal analgesia as the sole anaesthetic. Hypovalaemia, acid-base status and electrolyte imbalance were treated before instituting caudal epidural analgesia. We present this case report which describes the anaesthetic considerations in the light of the pathophysiology of Bartter’s syndrome.     

Renal transplantation and diabetic autonomic neuropathy

This report describes six episodes of cardiovascular collapse in the perioperative period of a young diabetic woman undergoing general anaesthesia for renal transplantation and a similar episode after a second anaesthetic. She was subsequently found to have an autonomic neuropathy. Recommendations for the management of similar patients are made.     

Toe skin temperature as a guide to epidural anaesthesia dosing

To determine the time for additional epidural anaesthesia, skin temperature of the big toe was evaluated in 50 patients undergoing mastectomy. Epidural catheters were placed at or near the T_5?6 intervertebral space and 12 ml, lidocaine 1.5% with 1:200,000 epinephrine were injected. When the skin temperature, which had increased following epidural anaesthesia, decreased by 0.3° C without an increase of systolic arterial blood pressure (ABP) of more than 20%, 8 ml lidocaine 1.5% were injected. If the skin temperature increased, the monitor was judged to have been useful. When ABP increased > 20% without a decrease of skin temperature, the monitor was judged not to have been useful. Monitoring of toe skin temperature was useful in 39 patients (78%) in estimating the time for the first additional dose of epidural anaesthetic. First, second and third intervals between injection were 96.5 ± 21.0 (n = 39), 69.7 ± 14.2 (n = 35) and 50.1 ± 12.2 min (n = 7), respectively. We conclude that, when epidural puncture is performed at upper thoracic levels, toe skin temperature can be a useful monitor to judge the time for additional anaesthetic.     

Anaesthetic considerations in the child with Menkes’ syndrome

The author presents and discusses the anaesthetic implications of a four-month-old infant with Menkes' syndrome who required tracheostomy. Menkes' syndrome is an X-linked recessive disorder of copper absorption and metabolism. Defective processing of copper results in abnormalities of several enzyme systems leading to severe dysfunction of multiple organ systems. Due to the progressive nature of this disorder and its severe effects on several different organ systems, most importantly the central nervous system, these children frequently require anaesthetic care during imaging procedures such as MRI or during various surgical operations. The high prevalence of seizure disorders, gastroesophageal reflux with the risk of aspiration, and airway complications related to poor pharyngeal muscle control are of concern to the anaesthetist. In addition, defective collagen formation, similar to that seen in Ehlers-Danlos syndrome, may be present. Identification of these associated conditions during the preoperative examination will guide the selection of appropriate, safe anaesthetic care for these children.     

MAO inhibitors and coronary artery surgery: a patient death

The mechanisms of action of monoamine oxidase inhibitors (MAOIs) suggest that patients taking them may respond with hyper- or hypotension when undergoing coronary artery surgery. We describe a case where MAOIs were present and fentanyl and midazolam were the anaesthetic agents used. The anaesthesia and surgery were performed without incident. Postoperative ICU care was complicated by hypertension, hyperthermia, and severe shivering followed by hypotension resistant to therapy and finally death. Diagnoses of pulmonary embolism and sepsis were unproven and may have played a role. The MAOIs may also have played a role. Reactions in patients while taking both meperidine and MAOIs are unusual and animals react differently from humans to a combination of MAOIs and narcotics. There are only five reported cases where fentanyl was given to patients on MAOIs. We conclude that, until there is more information, MAOIs should be discontinued, if possible, before surgery in which catecholamines may be needed.     

Advances in oral anti arrhythmic therapy: implications for the anaesthetist

Surgical patients often are receiving antiarrhythmic therapy. Thus, because anaesthetic agents can affect cardiac function and may interact with concurrent antiarrhythmic medications, the anaesthetist should be aware of the electrophysiology associated with dysrhythmias and their management. Tocainide, flecainide, mexiletine, encainide and amiodarone have been introduced recently and each has an unique pattern of bioavailability, metabolism and toxicity. Patients treated with these drugs need special concern as they have abnormal cardiovascular systems and may be at increased risk for perioperative morbidity. In addition, unexpected untoward reactions and toxicity can result from interactions of anaesthetic agents and these drugs. This review discusses normal cardiac electrophysiology, common dysrhythmias and the electrophysiological effects of the newer oral antiarrhythmic drugs.     

Caesarean section in a diabetic patient with a recent myocardial infarction

This is a report of a 38-yr-old parturient with multiple medical problems including diabetes mellitus, bronchial asthma, chronic myelogenous leukaemia, pre-eclampsia and a recent myocardial infarction. After medical management in the coronary care unit, it was decided to proceed with a Caesarean section. The choice of anaesthetic was made by the patient and had to be modified in accordance with her medical condition. Cardiovascular monitoring included PA catheterisation and transoesophageal echo-cardiography. A general anaesthetic was performed using fentanyl, thiopentone and succinylcholine. The outcome was satisfactory for both parturient and baby. Cette observation porte sur le cas d’une parturiente de 38 ans présentant de multiples problèmes dont un diabète, de l’asthme bronchique, une leucémie myelogène chronique, de la prééclampsie et un infarctus du myocarde récent. Après un séjour à l’unité de soins coronariens pour traitement, une césarienne est décidée. La patiente choisit son anesthésie, choix qu’il faut modifier pour des raison médicales. Le monitorage cardiovasculaire comprend la cathétérisme de l’artère pulmonaire et l’échographie transoesophagienne. L’anesthésie générale est réalisée avec du thiopentone, du fentanyl et de la succinylcholine. Les résultats sont favorables tant pour la mère que pour l’enfant.     

Laparoscopic cholecystectomy: the anaesthetist’s point of view

Although the surgical advantages of laparoscopic cholecystectomy (LC) have been reported, the anaesthetic problems associated with this new technique have not been well described. For the first 101 patients undergoing laparoscopic cholecystectomy at our institution, we prospectively documented intraoperative critical observations and adverse outcomes in the PACU (Post-Anaesthetic Care Unit). In order to put the magnitude of these problems into perspective, we compared, in an identical manner, the anaesthetic management and outcomes of two more familiar surgical groups, cholecystectomy by laparotomy (C), and laparoscopy for gynaecological examination (LG). For this new procedure LC, intraoperative hypotension (12.9%), and PACU hypothermia (31.4%), nausea and vomiting (12.9%) and desaturation (10.9%) were common but excessive pain (4.0%) was rare. Patients undergoing C, who were older and less healthy, tended to have fewer incidents of OR hypotension (3.4%) but in the PACU experienced more desaturation (25.9%) and excessive pain (12.9%) (P < or = 0.05). The younger and healthier LG group had fewer problems, less OR hypotension (0.4%), and less PACU nausea and vomiting (5.7%) and desaturation (1.3%) (P < or = 0.05). However, the LG group had a similar incidence of excessive pain (4.4%). We have documented considerable postoperative anaesthetic benefits for patients undergoing laparoscopic cholecystectomy compared with conventional cholecystectomy. However, there is still considerable perioperative morbidity compared with gynaecological laparoscopies. Now that specific problems have been identified, they may be amenable to specific anaesthetic interventions.     

Delayed awakening from general anaesthesia in a patient with Hunter syndrome

Hunter syndrome is one of a heterogeneous group of recessively inherited mucopolysaccharide storage diseases (MPS) with similar biochemical defects manifested by impairments in muco-polysaccharide catabolism with variable but progressive clinical courses. Abnormal accumulation and deposition of mucopoly-saccharides in the tissues of several organs lead to numerous anatomical, musculoskeletal and neurological abnormalities which are known to complicate anaesthetic and airway management. Hunter syndrome has a wide variance of clinical phenotypes ranging from mild to severe. We present a patient having physical and neurological features consistent with a severe clinical presentation of Hunter syndrome (MPS, Type II). Following a seemingly uneventful intraoperative anaesthetic course including isoflurane, nitrous oxide and fentanyl (0.93 μg · kg⁻¹), resumption of spontaneous ventilation and return to consciousness were delayed until intravenous naloxone (200 μg) was administered 100 min after the opioid administration. The cause of delayed recovery from anaesthesia in this patient is unknown. La maladie de Hunter fait partie du groupe des affections hétérogènes héréditaires et récessives des mucopolysaccharidoses (MPS) avec lesquelles elle partage les mêmes anomalies biochimiques. Celles-ci se manifestent par des altérations du catabolisme des mucopolysaccharides et une évolution variable et progressive. L’accumulation anormale de mucopolysaccharides dans les tissus de plusieurs organes provoque de nombreuses lésions musculo-squelettiques et neurologiques qui compliquent la gestion de l’anesthésie et des voies aériennes. Les phénotypes cliniques de la maladie de Hunter varient de légers à graves. Cette observation porte sur un patient qui présente des manifestations cliniques graves de la maladie de Hunter (MPS type II). A la suite d’une anesthésie sans problèmes réalisée avec de l’isoflurane, du protoxyde d’azote, et du fentanyl (0,93 μg · kg⁻¹), le retour normal à la ventilation spontanée et à la conscience est retardé jusqu’à l’administration de naloxone (200 mg) iv effectuée 110 min après le morphinique. La raison de ce retard est inconnue.