Focused parathyroid surgery with intraoperative parathyroid hormone measurement as a day-case procedure.

BACKGROUND: This study assessed the feasibility, efficacy and safety of focused parathyroidectomy combined with intraoperative parathyroid hormone (IOPTH) measurement in a day-case setting. METHODS: Over 28 months 50 consecutive patients (mean age 63 (range 33-92) years) with clear evidence of unifocal disease on sestamibi scanning or ultrasonography underwent unilateral neck exploration via a small lateral incision. Blood samples for measurement of IOPTH were taken at induction of anaesthesia, before adenoma excision and after adenoma excision (at 5, 10 and 20 min). Ten patients were discharged within 23 h and 40 patients on the day of surgery. RESULTS: A solitary adenoma was identified in all but one patient, with a mean operating time of 30 (range 16-57) min. After parathyroidectomy, IOPTH levels fell appropriately except in one patient with multiglandular hyperplasia. No patient developed symptomatic hypocalcaemia during the 2 weeks after operation, enabling cessation of oral supplements. All patients remained normocalcaemic on follow-up (mean 26 (range 8-84) weeks) and histological examination confirmed parathyroid adenoma (48 patients), hyperplasia (one) or carcinoma (one). CONCLUSION: After accurate preoperative localization of uniglandular disease, patients with primary hyperparathyroidism may be managed successfully and safely by focused parathyroidectomy with IOPTH measurement as a day-case procedure.

A cost analysis of surgery for ruptured abdominal aortic aneurysm.

OBJECTIVE: This study compares our costs of salvaging patients with ruptured abdominal aortic aneurysms (AAA) with the costs for unruptured AAAs. METHODS: Details of all AAAs presenting over 18 months were obtained. Costs of repair were carefully calculated for each case and were based upon ITU and ward stay and the use of theatre, radiology and pathology services. We compared the costs in unruptured AAAs with both uncomplicated ruptures and ruptures with one or more system failure. RESULTS: The mortality rate for ruptures undergoing repair was 18% and for elective repairs was 1.6%. The median cost for uncomplicated ruptures was 6427 Pounds (range 2012-13,756 Pounds). For 12 complicated ruptures, it was 20,075 Pounds (range 13,864-166,446 Pounds), and for 63 unruptured AAAs, was 4762 Pounds (range 2925-47,499 Pounds). CONCLUSION: Relatively low operative mortality rates for ruptured AAA repair can be achieved but this comes at substantial cost. On average, a ruptured AAA requiring system support costs four times as much as an elective repair.

Effects of dexmedetomidine on isoflurane requirements in healthy volunteers. 1: Pharmacodynamic and pharmacokinetic interactions.

Dexmedetomidine is a highly selective alpha 2-adrenoceptor agonist with anaesthetic-sparing effects. We have determined the pharmacodynamic and pharmacokinetic interactions between dexmedetomidine and isoflurane in volunteers. Nine male subjects were allocated randomly to receive isoflurane anaesthesia preceded by infusion of dexmedetomidine on three separate occasions, 2 weeks apart. Dexmedetomidine target plasma concentrations were 0.0 (placebo), 0.3 ng ml-1 (low-dex) and 0.6 ng ml-1 (high-dex). End-tidal isoflurane concentrations at which gross purposeful movement and response to verbal commands occurred were identified. In the recovery period, sedation scores and digit symbol substitution tests were recorded. Venous blood samples were obtained before, during and after anaesthesia at predetermined intervals for measurement of plasma concentrations of dexmedetomidine and calculation of standard pharmacokinetic indices (AUC, Cl, Vss, T1/2 alpha, T1/2 beta). The end-tidal isoflurane concentration at which 50% of subjects first responded to the tetanic stimulus was 1.05% in the placebo group, 0.72% in the low-dex group and 0.52% in the high-dex group. We conclude that dexmedetomidine decreased isoflurane requirements in a dose-dependent manner and reduced heart rate, systolic and diastolic arterial pressures. Sedation and slight impairment of cognitive function persisted for several hours after anaesthesia and the end of infusion of dexmedetomidine. Isoflurane did not appear to influence the pharmacokinetics of dexmedetomidine.

Sevoflurane degradation by soda lime in a circle breathing system.

Sevoflurane is degraded by soda lime to a vinyl ether commonly referred to as compound A. We measured the concentration of compound A in the circle breathing system of 31 patients receiving sevoflurane anaesthesia. Inspiratory and expiratory gas samples were analysed using gas chromatography and flame ionisation detection. The end-tidal sevoflurane concentration and soda lime temperature were recorded. The peak compound A concentration ranged between 10 to 32 ppm in the inspiratory limb and 7 to 26 ppm in the expiratory limb. There was a positive correlation between the peak compound A concentration and the end-tidal sevoflurane concentration (r2 = 0.545, p < 0.0001) and the soda lime temperature (r2 = 0.301, p = 0.0014). We conclude that the end-tidal concentration of sevoflurane and the temperature of the soda lime are important variables in determining concentration of compound A in a circle system.

Serum fluoride concentration and urine osmolality after enflurane and sevoflurane anesthesia in male volunteers.

The purpose of this study was to measure the serum fluoride concentration after enflurane or sevoflurane anesthesia and to compare the effects of prolonged anesthesia with these drugs on renal concentrating function in male volunteers. The study was subdivided into three stages; an ascending dose study of 3.0 and 6.0 minimum alveolar anesthetic concentration (MAC) hours of sevoflurane alone, a 6.0-MAC-hour comparison of enflurane and sevoflurane, and a 9.0-MAC-hour comparison of enflurane and sevoflurane. Renal concentrating function was assessed by an 18-h period of fluid deprivation and the serum fluoride concentration was measured at intervals until 60 h postanesthesia. The maximum serum fluoride concentration was greater in the volunteers exposed to sevoflurane and reached a peak in the 9-MAC-hour sevoflurane group of 36.6 microM (SD 4.3) compared with 27.5 microM (SD 2.6) in the 9-MAC-hour enflurane group. However, the rapid decrease in the serum fluoride concentration after sevoflurane was such that there was no difference between the areas under the fluoride concentration-time curves. There were no significant differences between the median maximum urine osmolalities after enflurane or sevoflurane anesthesia. Prolonged anesthesia with enflurane or sevoflurane is not associated with impaired renal concentrating function despite an increase in the serum fluoride concentration.

In vitro potency and mode of action of ANQ9040: a novel fast acting muscle relaxant.

1. The in vitro potency and mode of action of the novel, rapid-onset steroidal relaxant ANQ9040 were characterized in the rat isolated phrenic nerve hemidiaphragm. 2. At 32 degrees C, ANQ9040 antagonized neurally evoked contractures with EC50s of 21.5 microM for unitary twitches; 14.4 microM for 2 Hz 'trains of four'; and 7.5 microM for 50 Hz (2 s) tetanic stimulus trains. 3. (+)-Tubocurarine was 22-24 times more potent than ANQ9040 in comparative organ bath experiments. 4. Intracellular recording from endplates revealed that ANQ9040 (0.53-10.0 microM) dose-dependently and reversibly decreased the amplitude of miniature-endplate potentials (IC50 of circa 0.95 microM) without changing transmembrane potential. 5. Surmountable antagonism of subthreshold responses to exogenous (ionophoretic) acetylcholine provided evidence for a non-depolarizing and competitive blockade of post-junctional nicotinic receptors. 6. Sucrose gap recordings of phrenic nerve action potentials revealed that, at concentrations up to 32 microM, ANQ9040 produced no tonic or frequency-dependent antagonism of axonic Na+ channels. 7. We conclude that ANQ9040 is a relatively low-affinity, non-depolarizing, nicotinic antagonist. The in vitro results are discussed in relation to factors impinging on relaxant kinetics and current models for frequency-dependent fade.

Safety and potency of ANQ 9040 in male volunteers.

BACKGROUND: ANQ 9040 is an experimental nondepolarizing neuromuscular relaxant. Initial investigations in animals had indicated a rapid onset of action comparable to that of succinylcholine. The purpose of this study was to assess the safety and potency of ANQ 9040 in humans. METHODS: ANQ 9040 was assessed in 41 male volunteers. Anesthesia was induced with propofol and maintained with a propofol infusion and 60% N2O/40% O2. Neuromuscular function was measured by mechanomyography using train-of-four stimulation of the ulnar nerve every 12 s. After an initial pilot study, 23 volunteers received a single dose of ANQ 9040 of between 0.5 and 1.1 mg/kg to determine the dose-response relationship. The final 10 volunteers were given twice the estimated ED95 of ANQ 9040 as a single bolus dose. RESULTS: The estimated ED50 and ED95 of ANQ 9040 were 0.6 and 1.3 mg/kg, respectively. Apart from an increase in heart rate, no important adverse effects were noted after ANQ 9040 administration in the dose range 0.5-1.1 mg/kg. In the volunteers who received 2.6 mg/kg ANQ 9040, a substantial increase in plasma histamine was observed. This was associated with a 12% decrease in mean arterial pressure and a 49% increase in heart rate. In this group, the mean onset time to neuromuscular block was 51.3 s. CONCLUSIONS: ANQ 9040 is a rapid-onset neuromuscular blocking agent. However, twice the ED95 dose is associated with significant histamine release and tachycardia. This finding suggests that this drug will not be useful in clinical practice.

The effectiveness of pre-operative advice to stop smoking: a prospective controlled trial.

Patients who smoke cigarettes suffer increased postoperative morbidity. A prospective, controlled trial was designed to evaluate the effectiveness of written pre-operative advice to stop smoking before admission for elective surgery and to record the duration of abstinence immediately before the operation. Although the advice was ineffective in persuading patients to stop smoking, it was associated with a reduction in the amount of tobacco consumed. Nicotine and carbon monoxide have important short-term adverse effects but 15% of all patients continued to smoke within an hour of surgery. If patients are unable to give up cigarette smoking completely, it is still worthwhile stopping on admission to hospital.

A prospective study of liver function in infants and children exposed to daily isoflurane for several weeks.

Eleven infants and children presenting for daily radiotherapy for a period of at least 2 weeks were anaesthetised with isoflurane in 33% oxygen and nitrous oxide. They were unpremedicated and given no other agents to supplement anaesthesia. The average number of exposures was 24 (SD 11; range 10-39) and the total anaesthetic time per exposure varied between 15 and 30 minutes. Liver function was assessed by determining serum total bilirubin, aspartate amino transferase, gamma glutamyl transferase and alkaline phosphatase before the start of treatment and at 5-daily intervals thereafter. There was no measurable change in any of these determinants of liver function. All children accepted daily induction of anaesthesia with isoflurane. Induction, maintenance and recovery from anaesthesia were uncomplicated.