Isoflurane compared with nitrous oxide anaesthesia for intraoperative monitoring of somatosensory-evoked potentials

Intraoperative monitoring of somatosensoryevoked potentials is a routine procedure. To determine the depressant effect of nitrous oxide relative to isoflurane, the authors recorded the scalp, cervical and brachial plexusevoked responses to stimulation of the median nerve under different anaesthetic conditions. Eight subjects, age 35 ± 6 (SD) yr, weight 68 ± 12 kg, were studied. Following recording of awake control responses, anaesthesia was induced with thiopentone 5 mg· kg^{? 1} and fentanyl 3 μg· kg^{? 1} and was followed by succinylcholine 1 mg· kg^{? 1}. During normocapnia and normothermia, and with a maintenance infusion of fentanyl 3 μg · kg^{? 1}· hr^{? 1}, evoked potential recording was repeated under three different anaesthetic conditions; 0.6 MAC nitrous oxide, 0.6 MAC nitrous oxide ± 0.6 MAC isoflurane, and 0.6 MAC isoflurane. Among the anaesthetic conditions, the combination of nitrous oxide-isoflurane had the most depressant effect on the cortical amplitude (67 ± 4% reduction, P < 0.05). Nitrous oxide decreased the cortical amplitude more than an equipotent dose of isoflurane (60 ± 4% vs 48 ± 7%, P < 0.05). The latency was unchanged by nitrous oxide, but increased slightly by isoflurane and isofluranenitrous oxide anaesthesia (1.0 and 0.9 msec respectively, P < 0.05). We conclude that somatosensory-evoked potential monitoring is feasible both during nitrous oxide anaesthesia and isoflurane anaesthesia, but the cortical amplitude is better preserved during 0.6 MAC of isoflurane alone relative to 0.6 MAC of nitrous oxide alone. The depressant effect is maximal during nitrous oxideisoflurane anaesthesia but less than the predicted additive effect.     

Mechanisms of inhibition of endothelium-dependent relaxation by halothane,isoflurane, and sevoflurane

Volatile anaesthetics inhibit endothelium-dependent relaxation, but the underlying mechanism(s) have not been clarified. In an attempt to elucidate the mechanism(s), we determined the effects of halothane, isoflurane and sevoflurane on relaxation induced by acetylcholine and sodium nitro-prusside (SNP) and the cGMP formation elicited by exogenous nitric oxide (NO) and SNP in rat aortas. Acetylcholine (10^?7?10^?5M) - induced relaxation was attenuated by halothane (2%), isoflurane (2%) and sevoflurane (4%). SNP (10^?8 M) - induced relaxation was reduced by halothane (2%), but not by isoflurane (2%) or sevoflurane (4%). The cGMP level of NO-stimulated aorta was reduced by halothane (2%) and sevoflurane (4%), but not by isoflurane (2%). The cGMP level of SNP (10^?7 M) - stimulated aorta was reduced by halothane (2%), but not by isoflurane (2%) and sevoflurane (4%). We conclude that the mechanisms responsible for the inhibition of endothelium-dependent relaxation differ among anaesthetics. Isoflurane inhibits the relaxation mainly by inhibiting the formation of NO in the endothelium. In contrast, the effect of halothane on endotheliumdependent relaxation may be largely due to the inhibition of action of NO in the vascular smooth muscle and the effect of sevoflurane may be to inactivate NO or to inhibit the action of NO.     

Transcranial doppler sonography during isoflurane/N2O anaesthesia and surgery: flow velocity, “vessel area” and “volume flow”

Transcranial Doppler sonography (TCD) constitutes an advance in noninvasive monitoring of the cerebral circulation. However, as long as the diameter and cross-sectional area of the insonated middle cerebral artery (MCA) remain unknown, the derived flow velocities (v) are not informative. It is not known how the human MCA is influenced by anaesthetic agents. However, a TCD-modification allows noninvasive determination of “vessel area” (VA) and “volume flow” (VF) in MCA by analysing the backscattered Doppler power. This investigation evaluates the effects of isoflurane (in combination with N₂O and surgery) on v, VA and VF. In 14 patients (ASA I) scheduled for minor surgical or gynaecological operations, anaesthesia was induced with droperidol, alfentanil, thiopentone and vecuronium. After intubation ventilation with N₂O:O₂ = 3:2 was adjusted, to maintain endexpiratory carbon dioxide (FECO₂) constant between 4 and 5%. Baseline values of heart rate (HR), oscillometric mean arterial pressure (MAP), and TCD variables (v, VA VF) were measured before adding 2.4% isoflurane to the inspiratory mixture. Further measurementswere made 3, 6,10, and 20 min after starting isoflurane. Surgery commenced between the sixth and tenth minute after isoflurane application. The MAP,FeCO₂, and v showed only minor alterations; HR increased after 6, 10 and 20 min. Transcranial “vessel area” and “volume flow” showed increases after isoflurane inhalation. The increase of “vessel area” supports the assumption that isoflurane greater than 1 MAC dilates large human cerebral arteries, so that if flow velocities are considered alone, alterations of cerebral blood flow may easily be underestimated.     

Neuroleptic malignant syndrome and mivacurium: a safe alternative to succinylcholine?

Neuroleptic malignant syndrome (NMS) and malignant hyperthermia (MH) may have a common pathogenic mechanism; therefore, it has been suggested that known triggering agents for MH (such as succinylcholine) should be avoided in patients with NMS. Electroconvulsive therapy (ECT) continues to play a major therapeutic role in contemporary psychiatry, and succinylcholine has been the muscle relaxant of choice in attenuating violent muscle contractions induced by ECT. Mivacurium is a nondepolarizing muscle relaxant with a relatively rapid onset and a short duration of action, and to date it has been proved safe in MH- susceptible patients. In this case report, following succinylcholine use during ECT, a patient with NMS developed an increase in temperature and serum creatine kinase (CK) level, possibly due to an MH reaction. Since the patient’s mental status necessitated further ECT, mivacurium was administered during subsequent treatments and resulted in effective attenuation of muscle contractions without elevation of patient temperature or CK levels. In addition, there was no marked prolongation of the anaesthetic. Mivacurium is a suitable agent for patients with NMS undergoing ECT, as it has not been associated with precipitation of an MH response.     

Adjuvant propofol enables better control of nausea and emesis secondary to chemotherapy for breast cancer

We investigated the prophylactic antiemetic effect of added lowdose infusion of propofol in patients exhibiting nausea and vomiting refractory to dexamethasone and serotonin antagonist during non-cisplatin chemotherapy for breast cancer. In a prospective open longitudinal study, 117 patients who had more than five episodes of nausea and vomiting in their first chemotherapy cycle during the first 24 hr completed the study. They received in addition to the usual prophylactic antiemetic regimen a continuous intravenous infusion of 1 mg · kg^?1 · hr^?1 propofol started four hours before chemotherapy and continued up to 24 hr for the two subsequent cycles. The number of vomiting / nausea episodes, level of sedation, patient activity, appetite and preference for future chemotherapy cycles were assessed. In the propofol supplemented cycles 90 and 80% of patients, during the 1st and 2nd propofol-assisted cycle respectively, were free of nausea and vomiting during the first 24 hr after chemotherapy. Patients were more frequently active and had more appetite during the propofol-assisted cycles. No propofol-associated side effects were observed. We conclude that the addition of a subhypnotic infusion of propofol enables better control of nausea and vomiting caused by non-cisplatin chemotherapy in the first 24 hr post-treatment.     

Exacerbation of postdural puncture headache after epidural blood patch

The purpose of this report is to describe a new complication of epidural blood patch for inadvertent dural puncture. A dural tap in an obstetric patient was managed initially with a prophylactic blood patch via the epidural catheter. Despite this, 48 hr later, she developed post-dural puncture headache, neck, and shoulder pain, and was given a second epidural blood patch. This was followed by an immediate and severe exacerbation of her symptoms, which later resolved after the administration of diclofenac. There were no further sequelae. Although severe complications of epidural blood patch are rare, they are alarming. Exacerbation of the original symptoms of post-dural puncture headache caused by, or following, epidural blood patching has not previously been reported.     

Hydromorphone patient-controlled analgesia (PCA) after coronary artery bypass surgery

We conducted a study to compare the effectiveness of patientcontrolled analgesia (PCA) technique to conventional analgesic therapy (CAT) after coronary artery bypass graft (CABG). The PCA group received hydromorphone 0.1 mg · hr^?1 basal infusion and bolus doses of 0.2 mg Q 5 min (maximum 1.2 mg · hr^?1) while the CAT group received morphine 2.5 mg iv Q 30 min prn until extubation followed by prn meperidine 1 mg · kg^?1 im Q4 hr or acetaminophen 325 mg with codeine 30 mg po (1 or 2 tablets) when oral intake was possible. The degree of pain was assessed using a Visual Analogue Scale (VAS) starting after extubation and every 6–8 hr for the next 60 hr. Holter monitoring was initiated one hour after patient arrival in the Intensive Care Unit (ICU) and continued for 72 hr. Other measured variables were pulmonary function, sedation, side effects and total opioid requirements. Results show that the day-to-day VAS pain score decreased in the PCA group (P < 0.001) while it remained unchanged in CAT patients. The PCA patients had lower VAS pain scores at extubation (P < 0.05). During the third postoperative day, the PCA group had a lower VAS pain score, a lower incidence of severe pain defined as a score > 5 on the VAS scale, and a reduced incidence of myocardial ischaemia (P < 0.01). However, there was no difference in the duration, severity, area under the curve (AUC), or heart rate during ischaemic events. Postoperative pulmonary function was abnormal in both groups (NS) with minimal recovery by the fourth day. Opioid requirements, incidence of side effects and the degree of sedation were similar. We conclude that the PCA technique for analgesia provided slightly better results. The finding of a reduced incidence of myocardial ischaemia in the PCA group warrants further clinical investigation.     

Epidural opioid analgesia after Caesarean section: a comparison of patient-controlled analgesia with meperidine and single bolus injection of morphine

The quality of analgesia, patient satisfaction and incidence of side effects following a single bolus of epidural morphine were compared with patient-controlled epidural analgesia (PCEA) with meperidine during the first 24 hr after elective Caesarean section. Seventy-five women were randomly assigned to three equal groups. Group 1 received 30 mg epidural meperidine after delivery and PCEA with meperidine; Group 2 received 3 mg epidural morphine after delivery and PCEA with saline in a double-blind fashion. Group 3 received 3 mg epidural morphine after delivery without saline PCEA. Visual analogue pain scores (VAS) were higher with PCEA meperidine from 8–16 hr postoperatively (P < 0.05) than in both epidural morphine groups. Two patients in Group 1 and one in Group 3 required supplemental parenteral analgesia. The incidence of nausea was 16% in Group 1, compared with 52% in Group 2 and 56% in Group 3 (P < 0.01). Pruritus occurred in 24% of Group 1 patients, 84% of patients in Group 2 and 68% of patients in Group 3 (P< 0.001). Forty-six percent of patients in Group 1 were very satisfied with pain management, compared with 77% in Group 2 and 79% in Group 3. Nurse workload was higher in the PCEA study groups than in Group 3 (P< 0.05). A single bolus of epidural morphine provides superior analgesia and satisfaction at low cost, but with a higher incidence of nausea and pruritus than PCEA with meperidine.     

Phaeochromocytoma presenting as acute hyperamylasaemia and multiple organ failure

Phaeochromocytoma may present in many different ways. We report an unusual presentation of phaeochromocytoma in a man with hyperamylasaemia and multiple organ failure thought to be due to acute relapsing pancreatitis. Abdominal ultrasound and computerised tomography (CT) examinations revealed a mass at the tail of the pancreas. Fine needle biopsy of the mass precipitated headache, intense vasoconstriction and labile blood pressure. He proceeded to laparotomy, at which an 8 × 9 cm mass was found to be replacing the left adrenal gland. Histological examination revealed a phaeochromocytoma. This case illustrates that hyperamylasaemia and multiple organ failure may be unusual presentations of phaeochromocytoma and phaeochromocytoma should be considered in the differential diagnosis of a peripancreatic mass found by ultrasound or CT.     

Propofol sequestration within the extracorporeal circuit

Various drugs administered during cardiac anaesthesia are sequestered in the extracorporeal circuit in vitro, but it is uncertain whether this sequestration phenomenon affects plasma drug concentration in vivo. The present study was undertaken to evaluate (1) in vitro sequestration of propofol in the extracorporeal circuit and (2) whether the change in plasma propofol concentration induced by initiation of cardiopulmonary bypass in vivo can be explained by haemodilution. For the in vitro evaluation, three separate experiments with a closed circuit (membrane oxygenator, reservoir, and tubings) were performed. The pH and PCO₂ of the circulating solution (a mixture of Ringer’s acetate and whole blood) were maintained within the normal physiological range, and the temperature of the solution was 28° C. The solution was circulated at a flow of 4 L · min^?1 and propofol was added to the solution to achieve a concentration of 2 μg · ml^?1. Serial samples were taken from the circulating solution for measurement of propofol concentration by high performance liquid chromatography. In the in vivo part of the study, 14 patients received a continuous infusion of propofol, and samples for the determination of plasma propofol concentration and blood haematocrit were taken before and five and ten minutes after initiation of cardiopulmonary bypass. In vitro, at 5 and 120 min after addition of propofol into the circulating solution, approximately 65% and 25%, respectively, of the predicted propofol level was measurable in the solution. In vivo, five minutes after initiation of the cardiopulmonary bypass plasma propofol concentration decreased (P < 0.001) more (from 2.8 ±0.7 (mean ± SD) to 1.5 ± 0.5 μg · ml^?1, a 45 ± 12% decrease) than would have been predicted on the basis of acute haemodilution (a decrease in haematocrit from 0.39 ± 0.04 to 0.28 ± 0.03 is a 29 ± 4% decrease). Ten minutes after initiation of cardiopulmonary bypass, plasma propofol concentration was 1.6 ± 0.5 μg · ml^?1 (a 37 ± 27% decrease from the pre-bypass level) and haematocrit was 0.27 ± 0.04 (a 30 ± 6% decrease): the decrease in plasma propofol concentration was not different from the decrease observed in the haematocrit. In conclusion, propofol is markedly sequestered within the extracorporeal circuit in vitro. This sequestration may, to some extent, affect plasma propofol concentration in vivo.     

Cutaneous ionto-phoretic application of condensed lidocaine

The purpose of this study was to determine whether iontophoretic application of high concentrations of lidocaine, with the same current, would produce cutaneous local anaesthesia rapidly enough for clinical practice. Twenty healthy volunteers, 17 male and three female, were selected for study. After fiveminute or ten-minute iontophoresis using lidocaine 4, 10, 20, 30, 50%, we assessed the response to pin prick with a 27-gauge sterile needle inserted to the depth of 2 mm at five random locations in the iontophoretically-stimulated area. Also, plasma lidocaine concentrations were measured in the venous blood samples which had been taken from three male subjects, at 3, 10, and 30 min after iontophoresis with lidocaine 50%. The pain score after five-minute iontophoresis was higher than that after ten-minute iontophoresis, using each concentration of lidocaine (P< 0.001), whereas the pain scores had no correlation with lidocaine concentration within five-minute and ten-minute iontophoresis groups, respectively (P: NS). On the other hand, plasma lidocaine concentration was <1.0 μg · ml^?1 in all samples. No side effects other than erythema were observed after iontophoresis using high concentrations of lidocaine up to 50%. These results showed that by increasing the lidocaine concentration of the applied solution up to 50%, the application time of iontophoresis cannot be reduced from ten to five minutes without losing analgesic effect, although iontophoresis itself can be performed with safety.     

Anaesthetic management of an asthmatic child for appendicectomy

A 13-yr-old boy was scheduled for emergency appendicectomy because of abdominal pain. His preoperative medical history was complicated by a recent hospital admission for management of asthma. He had presented to hospital seven days earlier because of dyspnoea, tachypnoea and oxygen desaturation to 77% on room air. Following admission, he required intensive non-ventilatory management of his asthma, including intravenous salbutamol, methylprednisolone, and aminophylline, as well as use of an ipratroprium bromide inhaler and 100% oxygen by mask. He was discharged to the ward, and continued on prednisone (deltacortisone), beclomethasone inhaler, ipratroprium inhaler, and salbutamol inhaler. During his ICU stay, he complained of nonspecific abdominal pain, interpreted as gastro-oesophageal reflux. After four days, he was discharged to the ward. On his sixth hospital day, he began to experience right-sided lower abdominal pain and right shoulder pain. A surgeon was consulted, and the patient was found to have a very tender right lower quadrant with guarding and rebound pain. He was therefore scheduled for appendicectomy; antibiotic therapy with ampicillin, gentamicin, and metronidazole was initiated.     

Propofol anaesthesia in paediatric ambulatory patients: a comparison with thiopentone and halothane

The purpose of this study was to evaluate the haemodynamic changes during induction, as well as the speed and quality of recovery when propofol (vs thiopentone and/or halothane) was used for induction and maintenance of anaesthesia in paediatric outpatients. One hundred unmedicated children, 3–12-yr-old, scheduled for ambulatory surgery were studied. The most common surgical procedures performed were eye muscle surgery (42%), plastic surgery (21%), dental restoration (15%), and urological procedures (15%). The children were randomized to an anaesthetic regimen for induction/maintenance as follows: propofol/propofol infusion; propofol/halothane; thiopentone/halothane; halothane for both induction and maintenance. Succinylcholine 1.5 mg · kg^?1 was used to facilitate tracheal intubation and N₂O/O₂ were used as the carrier gases in each case. All maintenance drugs were titrated according to the clinical response of the patient to prevent movement and/or maintain BP ± 20% of baseline. Two patients (4%) who received propofol expressed discomfort during injection. The mean propofol dose required to prevent movement was 267 ± 83 μg · kg^?1 · min^?1. The overall pattern of haemodynamic changes, as well as awakening (extubation) times were not different among the four groups. Children who received propofol recovered faster (22 vs 29–36 min) (P < 0.05), were discharged home sooner (101 vs 127–144 min) (P < 0.05), and had less postoperative vomiting (4 vs 24–48%) (P < 0.05) than all others. There were no serious complications or adverse postoperative sequelae in any of the patients in the study. It is concluded that induction and maintenance of anaesthesia with propofol is a well-tolerated anaesthetic technique in children, and is associated with faster recovery and discharged as well as less vomiting than when halothane is used.     

Embolism detected by transoesophageal echocardiography during hip arthroplasty

This case report demonstrates embolization of echogenic material detected by transoesophageal echocardiography during a cemented total hip arthroplasty in a 76- yr- old woman without patent foramen ovale. During the placement of the acetabular and femoral components, and during relocation of the hip joint, a “snow flurry” appearing in the right atrium was followed by several highly echogenic and mobile emboli of various sizes, some of them with a vermiform shape 1 to 5 cm long. At skin closure, echogenic material was seen in the right branch of the pulmonary artery adherent to the vascular wall of the bifurcation of the main pulmonary artery. No changes were observed in any haemodynamic variable monitored (heart rate, systemic and right atrial pressures). Also, no desaturation was detected by pulse oximetry and blood gases at the time of embolism and there was no decrease in PetCO₂. This case report is in line with other studies which failed to show a haemodynamic impact of TEE detected emboli during THA.     

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.     

Malignant hyperthermia and calcium-induced heat production

The abnormal increase in intracellular Ca⁺⁺ in malignant hyperthermia (MH) is well documented, but the link between the increased Ca⁺⁺ concentration and high temperature remains speculative. We investigated the possibility that the Ca⁺⁺-induced change in the state of cell membranes may contribute to the temperature elevation. Calcium ion transforms phosopholipid membranes from the fluid to solid state. This is analogous to the freezing of water, and liberates latent heat. Differential titration calorimetry (DTC) measures heat production or absorption during ligand binding to macromolecules. When CaCl₂ solution was added to anionic dimyristoylphosphatidic acid (DMPA) and dimyristoylphosphatidylglycerol (DMPG) vesicle membranes in incremental doses, DTC showed that the heat production suddenly increased when the Ca⁺⁺ concentration exceeded about 120/μM. At this Ca⁺⁺ concentration range, these lipid membranes underwent phase transition. The latent heat of transition was measured by differential scanning calorimetry (DSC). The values were 7.1 ± 0.7 (SD, n = 4) kcal · mol^?1 of DMPA and 6.8 ± 0.7 (SD, n = 4) kcal · mol^?1 of DMPG. The study shows that Ca⁺⁺ produces heal when bound to lipid membranes. We are not proposing, however, that this is the sole source of heat. We contend that the lipid phase transition is one of the heat sources and it may trigger a hypermetabolic state by elevating the temperature of cell membranes. Because Ca⁺⁺ is implicated as the second messenger in signal transduction, multiple systems may be involved. More studies are needed to clarify how Ca⁺⁺ increases body temperature.     

Hypoxaemia and hypotension after intravenous codeine phosphate

This report describes a case of accidental intravenous administration of codeine phosphate (1 mg · kg^?1) to a previously healthy five-year-old boy, who was undergoing strabismus surgery. Hypoxaemia (SpO₂ 85% with FiO₂ of 1) and hypotension (systolic BP 65 mmHg) resulted, which responded to resuscitation with lactated Ringers (20 ml · kg^?1) and phenylephrine (2 μg · kg^?1). The degree of hypoxaemia observed in this case was severe, but was not associated with clinical evidence of bronchospasm. Possible mechanisms for this reaction might have included direct myocardial depression and histamine release. This case adds further support to the recommendation that codeine phosphate should never be administered intravenously.     

Cerebral arteriovenous malformations in children

The treatment of cerebral arteriovenous malformations (AVM) or vascular anomalies are challenging neurosurgical procedures for an anaesthetist. Large AVMs are uncommon in children. Only 18% of AVMs become symptomatic before the age of 15 yr. This series reviews the experience at this institution during the period of 1982 to 1992. The symptoms at the time of presentation are varied and include haemorrhage (50%), seizures and hydrocephalus (36%) or congestive cardiac failure (18%). Symptoms of congestive heart failure predominate in the new-born whilst neurological symptoms, such as stroke, seizures or hydrocephalus occur more commonly in infants and older children. Approximately one third of AVMs in childhood present acutely. Radiological investigations, e.g., CT scan, MRI and cerebral angiography are essential to identify the precise location of the lesion. Therapeutic intervention in the acute presentation may involve craniotomy for evacuation of haematoma and treatment of increased intracranial pressure (ICP). Control of seizures and congestive heart failure may take priority and allow time to plan the elective procedures of embolization and surgical excision of the AVM. Operative intervention is hazardous and peroperative complications can be expected in more than 50% of patients. The morbidity and mortality associated with cerebral AVM are high, especially in infants who present in the neonatal period with congestive cardiac failure. The overall mortality in this series was 20%. Children presenting with intracranial arteriovenous malformations require a multidisciplinary approach. The successful management of anaesthesia either for embolization or surgical resection necessitates an understanding of the disciplines of paediatric and neuroanaesthesia. Special care and specific attention to detail may contribute to reduce the high morbidity and mortality encountered in these compromised children.     

Anaesthesia for the patient with neonatal adrenoleukodystrophy

The authors present and discuss the care of a nine-month-old with neonatal adrenoleukodystrophy who required general anaesthesia for gastrointestinal endoscopy. Neonatal adrenoleukodystrophy is an inherited disorder of peroxisomal enzymes. Anaesthetic care may be affected by the presence of hypotonia, liver function abnormalities, gastroesophageal reflux, and impaired adrenocortical function. Preoperative sedation is contraindicated because of the risk of precipitating airway obstruction due to preexisting hypotonia. Anaesthetic induction and tracheal intubation should be performed to minimize the risk for aspiration of gastric contents. The choice of muscle relaxant should take into account the preexisting hypotonia as well as the possibility of hyperkalaemia in response to succinylcholine. Anaesthetic agents known to decrease the seizure threshold should be avoided in patients with a seizure disorder. In addition, anaesthetic agents that rely on the liver for metabolism should be used with caution in patients with cirrhosis. When time permits, these patients should be screened for adrenocortical insufficiency before surgery, and perioperative steroid coverage is advisable when preoperative testing of adrenocortical function is not feasible. While these patients eventually die after progressive deterioration, full recovery from the effects of anaesthesia and surgery can be achieved with attention to neurological, metabolic, and physical problems.     

Flumazenil as a diagnostic tool in the differential diagnosis of coma in a critically ill patient

The purpose of this report is to describe the use of flumazenil as a diagnostic aid in the differential diagnosis of coma in a patient with an inadvertent overdose of benzodiazepines. We report a patient with suspected septic encephalopathy whose level of consciousness markedly improved following flumazenil administration. Subsequent analysis revealed the presence of benzodiazepines and their metabolites in the blood and urine although the patient had not received benzodiazepines for over two weeks. The critically ill patient with multiorgan failure may have considerable derangement of benzodiazepine metabolism; therefore, if an obtunded patient’s level of consciousness improves following flumazenil administration, benzodiazepine intoxication must be considered.