Gerhard A. Baer

Peripherally administered sufentanil inhibits pain perception after postpartum tubal ligation.

The clinical effectiveness of locally administered opioids is still under discussion; in particular, the potency of morphine in settings other than intra-articular arthroscopy has been questioned. We developed another pain model, postpartum resection of the fallopian tubes for sterilisation, in which each patient serves as her own control when one side is infiltrated with the active drug (in this study sufentanil 5 mg) and the contralateral side with normal saline. In the control group both sides are infiltrated with plain saline. After 30 min from the end of anaesthesia onwards, 26 out of 30 patients observed significant pain relief on the side of the sufentanil infiltration, which in 11 patients lasted until the end of the observation period 24 h postoperatively; no difference was observed in the control group. In our pain model with a high assay sensitivity, the infiltration of one side with the lipophilic test drug, sufentanil, caused local analgesia in primarily non-inflamed tissue. The use of each patient as her own control excluded inter-subject bias.

End-tidal oxygen concentration and pulse oximetry for monitoring oxygenation during intratracheal jet ventilation

Objective. In this study, we evaluated the usefulness of end-tidal oxygen monitoring during intratracheal jet ventilation (ITJV) for endolaryngeal laser surgery.Methods. A total of 20 consecutive patients of both genders scheduled for endolaryngeal procedures under general anesthesia were studied. Inspiratory oxygen concentration and respiratory rate were varied, with patients serving as their own controls. Readings of pulse oximetry, airway oxygen, and carbon dioxide concentrations were recorded, and arterial blood samples for blood gas analysis were taken.Results. At jet cycle rates of 20 cycles/min, end-tidal oxygen (ETo2) concentration indicated alveolar hypoxia 30 to 60 sec before hypoxemia was detected by pulse oximetry. Jet mixing of inspiratory and expiratory gas caused a larger difference between end-tidal and arterial gas concentrations than normally seen with conventional ventilation. Correlations between ETo2 concentrations, oxygen saturations, and arterial oxygen levels depended on respiratory rate and inspiratory oxygen concentration; correlations were stronger at low than at high inspiratory oxygen concentrations and stronger at low than at high respiratory rates.Conclusions. ETo2 concentration should be maintained well over 21% during ITJV to prevent alveolar and arterial hypoxia. Monitoring of respiratory oxygen concentrations at jet cycle rates of 20 cycles/min and less verifies safe oxygen levels during laser surgery, and confirms adequate alveolar oxygenation.

Does abstinence from smoking or a transdermal nicotine system influence atracurium-induced neuromuscular block?

The purpose of the present study was to investigate the interaction of chronic smoking and the actions of atracurium (ATR).Twenty nonsmokers (NON-SMOK) were compared with 80 smokers, who were randomized into three groups: 30 patients received 21 mg/d transdermal nicotine system >or=to10 h before fentanyl/thiopental/N2 O/O2/isoflurane anesthesia (TD-NICO), whereas the abstinent group received a placebo transdermal system (ABST, n = 30). The TD-NICO and ABST groups refrained from smoking for at least 10 h before the induction of anesthesia. A third group was allowed to smoke until 1-3 h before anesthesia (SMOK, n = 20). Neuromuscular block was monitored using a Relaxograph[trade mark sign] (Datex, Helsinki, Finland). The electromyographic response was recorded from the first dorsal interosseus muscle of the hand. The inspiratory isoflurane concentration was kept constant at 0.7 vol% in all patients. After an initial bolus dose of 0.5 mg/kg ATR, no significant difference was observed among the groups regarding onset time and maximal neuromuscular block. In Group ABST, the duration of block until 25% recovery of T1 was 48.2 +/- 10.1 min, which was significantly longer (analysis of variance post hoc tests) than in Groups TD-NICO, SMOK, and NON-SMOK (42.7 +/- 7.1, 41.4 +/- 10.4, and 42.8 +/- 7.3 min, respectively). The maintenance dose of ATR in Group ABST (0.23 +/- 0.03 mg [center dot] kg-1 [center dot] h (-1)) was smaller than in Groups TD-NICO, SMOK, and NON-SMOK (0.30 +/- 0.07, 0.32 +/- 0.06, and 0.32 +/- 0.05 mg [center dot] kg-1 [center dot] h-1, respectively). We conclude that abstinence from smoking increases the duration of ATR-induced neuromuscular block and reduces the maintenance dose of ATR in smokers. Perioperative use of a transdermal nicotine system prevents these abstinence-induced changes in duration and maintenance-dose. Implications: The purpose of the present study was to investigate the interaction of chronic smoking and atracurium. Smokers who refrain from smoking for >10 h require a smaller maintenance dose of atracurium than nonsmokers. However, using a transdermal nicotine system prevents the decrease in maintenance dose during abstinence. (Anesth Analg 1998;87:430-3)

Non-steroidal anti-inflammatory drugs for postoperative pain relief

Non-steroidal anti-inflammatory drugs (NSAIDs) block both cyclo-oxygenase-1 and −2. The ratio of potency against cylco-oxygenase-1: potency against cyclo-oxygenase-2 explains the profile of efficacy and side effects of these agents. NSAIDs inhibit nociceptive transmission through C-fibres, but presumably not through Adelta-fibres. They relieve pain and display synergistic effects with opioids when administered intrathecally. The spectre of side effects was in favour of NSAIDs when compared with opioids in only a few controlled studies. A pre-emptive effect of NSAIDs on postoperative pain is still discussed. NSAIDs should be used with caution in the elderly, in the intensive care unit, and in patients with bronchial asthma, reduced renal function, or impaired gastroduodenal mucosal protection.

Threshold currents of platinum electrodes used for functional electrical stimulation of the phrenic nerves for treatment of central apnea.

Stability of threshold currents during long‐term use of phrenic nerve stimulation has been questioned.

The effect of diclofenac and ketoprofen on halothane MAC in rabbit

Non-steroidal anti-inflammatory drugs obviously act also on the central nervous system. We, therefore, studied the effect of diclofenac 3 mg/kg and ketoprofen 4 mg/kg on the minimum alveolar concentration (MAC) of halothane in 10 New Zealand White rabbits. After determination of halothane MAC, total doses of NSAIDs were administered intravenously as three subdoses: 12.5%, 37.5% and 50% of the total dose. Depth of anaesthesia did not increase significantly after the first two doses with either drug. With ketoprofen, halothane MAC increased after subdose 3 from 1.52 (SD 0.42) vol% to 1.9 (SD 0.36) vol% (p<0.01). With diclofenac, halothane MAC increased after subdose 3 from 1.44 (SD 0.18) vol% to 1.60 (SD 0.39) vol% (ns). With both drugs, large interindividual differences of MAC appeared after full doses of NSAIDs.

Children's drawings as a measure of anxiety level: a clinical pilot study

Background : No simple method exists to distinguish children in need for premedication. The present study was planned to detect preoperative anxiety levels of children by rating their drawings.

What to prefer during jet ventilation for endolaryngeal procedures, risk of barotrauma or of aspiration of contaminating material?

endotracheal tube, e.g., 2.5–3.0 mm ID. The combined diameter of the body of the catheter (approximately 1 mm) and the endotracheal tube may be as small as 3.5 mm. The catheter balloon position can be confirmed by passing a small FOB through the endotracheal tube or by fluoroscopy. To avoid airway injury, anesthesiologists must be mindful of the diameters of both the airways and devices placed therein. Appropriate maneuvers must be performed to ensure that tight-fitting endotracheal tubes are not placed to facilitate single-lung ventilation in infants and children.

Neuromuscular blocking characteristics of vecuronium after tubocurarine-induced "fade". An experimental double-blind clinical study.

AbstractObjective: The fade in train-of-four (TOF) monitoring is considered to be due to blocking of the prejunctional nicotinic acetylcholine receptors (AchRs). During onset of the neuromuscular block (NMB) tubocurarine (TC) causes more fade in the TOF responses than vecuronium (VEC). Therefore we wanted to investigate whether onset or duration of action of VEC or TC would be improved with a priming dose of an agent with different prejunctional activity. Methods: The rates of NMB were measured following priming doses of 0.15 mg · kg−1 of TC and 0.015 mg ·  kg−1 of VEC with 6 min priming time. The individual time course of action of 0.6 mg · kg−1 of TC (1.13 × ED 95) and 0.1−0.2 mg · kg−1 of VEC (1.75–3.5 × ED95) were examined with a priming dose of the same agent or the other agent, by measurement of changes in the evoked compound EMG from the hypothenar muscle. Results: Priming doses of TC decreased mean TOF ratio to 67% [95% confidence interval (CI) = 56–78] during priming time, which was significantly lower than after priming with VEC 87% (76–97; P < 0.001). Despite the higher TOF ratio, the priming dose of VEC accelerated the onset time of intubation dose of TC more than the priming dose of TC (P = 0.0018). Priming with TC prolonged the duration of VEC-induced NMB by 35–70 min compared with priming with VEC, which means that a small priming dose of TC changes VEC from a muscle relaxant with intermediate action to a long-acting agent. Conclusion: Priming with TC caused a lower TOF ratio; however, priming with TC did not accelerate the onset time of either agent as much as priming with VEC. It appears that potentiation of NMB after combination of VEC and TC is not dependent on “fade” receptors.