[Closed anesthetic systems]. / Lukkede anaestesisystemer.

Anaesthesia with closed anaesthetic systems demands knowledge of the physiology of the patients and of how the various anaesthetic gases behave in the organism as only the gases which the patients produces and absorbs are eliminated and replaced. The system is educational as it provides knowledge of the genuine absorption of oxygen and anaesthetic gases. The method is favourable to the environment as only the gases which are used are supplied and it is thus economical in use although investment in monitoring equipment is necessary. In practice, induction and waking of the patient are complicated with this system and it requires an anaesthetist who constantly adjusts the gases in the circuit.

[Low-flow anesthesia systems]. / Lav-flow-anaestesisystemer.

At present, when economy and environment receive high priority, the ideal anaesthesia system with inhalation anaesthetics is a closed circle system in which only the gases which the patient consumes or produces are replaced or eliminated. Low-flow (LF) anaesthesia in which the fresh gas flow which is employed in a closed system, provides a stable system compares with closed anaesthesia systems. Compared with open systems and circler systems with considerable fresh gas flow, the LF system provides advantages as regards economy, environment and exposure of staff to inhalation anaesthetics. The special conditions involved in LF anaesthesia are described in detail with the hope that the method will obtain more widespread distribution than is the case in Denmark today. If greater safety under anaesthesia is desired, eg by monitoring the concentrations of CO2, O2 and inhalation anaesthetics which the patients inspire and expire, this monitoring equipment can be financed by introduction of LF anaesthesia.

The effect of metoclopramide on gastric contents after preoperative ingestion of sodium citrate.

Because sodium citrate is known to increase both gastric pH and gastric volume while metoclopramide decreases gastric volume, we evaluated, in a double-blind randomized study, the effect of combining metoclopramide with sodium citrate on gastric pH and volume after induction of anesthesia in 60 female patients to determine whether gastric pH could be increased at the same time that gastric volume was decreased. All patients received 50-ml sodium citrate. To mimic standard anesthetic practice, all patients were premedicated: 20 patients received meperidine alone, 20 received meperidine plus 20-mg metoclopramide, and 20 received diazepam plus 20-mg metoclopramide. Metoclopramide failed to decrease median gastric volume or to increase the number of patients with gastric volumes less than 25 ml. There was no difference in median pH values in the three groups of patients. In patients receiving metoclopramide, the risk of pH values less than 2.5 was greater with gastric volumes less than 25 ml than in patients with volumes greater than or equal to 25 ml. We conclude that preoperative metoclopramide does not decrease gastric volume in patients premedicated with meperidine or diazepam and that when gastric volume was less than 25 ml the neutralizing effect of sodium citrate was lost.

Catatonia after epidural morphine.

A 43-year-old male with bronchogenic carcinoma was treated with continuous morphine via a thoracic epidural catheter. On the fifth day, after a total dose of 24 mg morphine chloride in 10 or 20 ml saline, he developed hallucinations, hyperthermia, spasticity, narcolepsy and opisthotonos. Respiratory rate and blood pressure were unaffected. Intravenous naloxone reversed all neurological abnormalities. This unusual syndrome was probably caused by a rostal spread of morphine. The location of the catheter and volume seem to be important variables. Hallucinations are important signs of impending intoxication.

Influence of epidural morphine on postoperative pain, endocrine-metabolic, and renal responses to surgery. A controlled study.

In order to assess the analgesic properties of epidural low-dose morphine and its possible influence on the adrenocortical, hyperglycemic, renal, electrolyte and leukocyte responses to surgery and nitrogen excretion, a double-blind randomized study was undertaken in 14 otherwise healthy patients admitted for hysterectomy under halothane, N2O/o2 anesthesia. Before induction of anesthesia, an epidural catheter was introduced into the lumbar epidural space. After induction of anesthesia, either morphine 4 mg in 10 ml saline or 10 ml saline was injected into the epidural space, according to the allocation. Postoperatively, the degree of pain was evaluated by mean of a visual analogue scale (0-10). When pain score exceeded 5 points during the 24 -h trial, either 4 mg morphine in saline or saline was given epidurally. If the pain score did not decrease more than 2 points after an epidural injection, morphine was given parenterally (5 mg i.v. +5 mg i.m.). The results showed that pain scores, duration of pain relief and doses of morphine differed significantly between groups (P less than 0.05). Plasma concentration of cortisol and glucose, plasma-and urine electrolytes, 24-h creatinine and free-water clearances, diuresis, fluid balance, leukocyte count and nitrogen excretion differed insignificantly between groups. In conclusion, epidural low-dose morphine is a superior alternative to conventional postoperative pain treatment because of greater and longer lasting pain relief, without apparent side-effects. The measured endocrine-metabolic and renal response did not differ between groups, indicating that low-dose epidural morphine does not inhibit afferent neurogenic stimuli from the site of surgical trauma.

Thiopentone-nitrous oxide-halothane anaesthesia and suxamethonium: pretreatment with pancuronium and gallamine.

Eighty healthy adult patients randomly allocated to four groups received pancuronium 0.01, 0.015, 0.02 mg kg-1 or gallamine 0.3 mg kg-1 i.v. 3 min before induction. Just before induction of anaesthesia, the patients were examined for signs and symptoms of neuromuscular blockade. After induction of anaesthesia with thiopentone, suxamethonium 1.5 mg kg-1 was administered i.v. Five minutes later the second dose was injected. No serious arrhythmia was seen in any of the four groups following the repeated dose of suxamethonium. However, the highest dose of pancuronium (0.02 mg kg-1) caused an unacceptably high frequency of partial neuromuscular blockade.

Gastric contents and pH after oral premedication.

Forty women, aged 26-40 years, were investigated with regard to gastric contents and pH before general anaesthesia. The patients were divided into two groups (20 in each). Group 100 received 0.3 mg kg-1 diazepam orally with 100 ml of water 2 h before surgery. Group 50 received 0.3 mg kg-1 diazepam with 50 ml of water 2 h before surgery. The amount of gastric content was significantly greater in Group 100 than in Group 50 (P less than 0.05). There was no statistical difference in pH values between the groups. The number of patients with both gastric pH less than 2.5 and gastric volume greater than 25 ml was significantly higher in Group 100 compared to Group 50 (P less than 0.05). We cannot recommend the use of oral premedication using these amounts of water, considering the increased risk of aspiration of gastric contents.

Effect of ketanserin on cerebral blood flow autoregulation in healthy volunteers.

The effect of a clinically relevant dose of ketanserin (10 mg as a bolus followed by an infusion of 6 mg/h) on cerebral blood flow (CBF) and CBF autoregulation was examined in 12 healthy volunteers. Changes in CBF were estimated by the cerebral arteriovenous-oxygen saturation difference method, while mean arterial blood pressure (MABP) was increased by norepinephrine and decreased by ganglionic blockade (trimethaphan camphosulphonate) combined with lower body negative pressure one hour after the infusion of ketanserin. During ketanserin infusion, MABP fell insignificantly by 2.5 mmHg (6 to -2), while CBF rose insignificantly by 5 ml/100 g/min. Autoregulation was preserved in all volunteers. CO2-correction factors from 0 to 4.6% CBF/0.1 kPa were used. The lower limit of CBF autoregulation was 82 mmHg (80-86) with an SE of 3 mmHg (1-5) similar to a previous control group of healthy volunteers. Aside from a major decrease in MABP in one subject, no adverse side effects were observed. The present study shows that CBF autoregulation is maintained during ketanserin infusion.

Pretreatment with non-depolarizing muscle relaxants: the influence on neuromuscular transmission and pulmonary function.

The influence of pretreatment with non-depolarizing muscle relaxants on the neuromuscular transmission was evaluated in 40 healthy, awake, non-premedicated volunteers using train-of-four (TOF) nerve stimulation and measurement of vital capacity (VC), inspiratory force (IF), peak expiratory flow (PEF), and forced expiratory volume in the first second (FEV1). The subjects were randomly allocated to one of four groups: group I received pancuronium 0.01 mg/kg; group II pancuronium 0.015 mg/kg; group III gallamine 0.3 mg/kg, and group IV gallamine 0.4 mg/kg intravenously. TOF ratio decreased significantly in groups II, III and IV but not in group I following precurarization. Median (25 and 75 percentiles) TOF ratios after pretreatment wer 94(92-96), 89 (86-93), 92 (89-93), and 93 (87-96), respectively. Overall there were decreases in VC, IF, and PEF, but only the decrease in PEF was statistically significant in all four groups. FEV1 was unchanged. The most pronounced decrease in VC, IF, and PEF (11, 29, and 29%, respectively) was seen one subject in group II with a TOF-ratio of 63 following precurarization. Four subjects (20%) in groups II and IV experienced difficulty in breathing. All subjects were, however, able to maintain head lift for more than 10 s, and none needed respiratory support. Seventy percent of all subjects had various minor complaints as, for instance, blurred vision and difficulty in swallowing. It is concluded that the higher doses of pancuronium 90.015 mg/kg) and gallamine (0.4 mg/kg) cannot be recommended for routine precurarization.