Peribulbar anaesthesia: a double-blind comparison of three local anaesthetic solutions

A prospective, randomised, double-blinded study comparing three agents for peribulbar anaesthesia is reported. Sixty patients undergoing extracapsular cataract extraction under local anaesthesia were randomly allocated to receive peribulbar anaesthesia with lignocaine 2% with adrenaline; prilocaine 3% with felypressin 0.03 IU.ml-1 or 2% lignocaine and 0.5% bupivacaine in a ratio of 1:1, using a standardised two-injection technique. The pain of injection, time of onset of the block and the operating conditions at the start and finish of surgery were assessed. Peribulbar anaesthesia using lignocaine 2% was significantly more painful than the other solutions. The onset of anaesthesia adequate for surgery was similar in all three groups. Prilocaine 3% with felypressin was associated with the greatest number of blocks providing total akinesia of the eye. Inadequate duration of anaesthesia was seen in only one case; the solution used for this block was 2% lignocaine.     

Venous levels of lignocaine and bupivacaine after peribulbar block

Twenty-five patients undergoing elective cataract day surgery were studied after receiving a dual-injection peribulbar block with a mixture consisting of equal volumes of 2% lignocaine and 0.75% bupivacaine with hyaluronidase. A maximum of 10ml of solution was used for the initial block; supplementary injections of up to 10 ml were given to five patients. Venous blood was taken prior to the block and then 1, 10, 20, 30, 60 and 90 min after the block. The peak mean concentrations of lignocaine (0.722 μg. ml⁻¹) and bupivacaine (0.353 μg. ml⁻¹)were found at 10–20 min after injection when no top-up was given and at 10 min after the top-up injection when required. All measured serum concentrations of lignocaine and bupivacaine were below the accepted toxic levels of the two drugs. However, the highest individual toxicity score after a top-up was 0.915 which was very close to the toxicity threshold (= 1) when a scoring system was used to assess the combined levels.     

The EMLA patch—a new type of local anaesthetic application for dermal analgesia in children

The skin application of EMLA cream under a Tegaderm dressing was compared in children with a new combined dressing/local anaesthetic patch—the EMLA patch. The analgesic effect during venepuncture was assessed using a visual analogue scale (patients) and a verbal rating scale (investigator). Skin adhesiveness and incidence of local skin reactions with the two types of application were also studied. The study was designed as an open randomised trial with two parallel groups. Sixty children, aged between 5 and 15 years were evaluated. After a minimum application time of 60 min an intravenous cannula was inserted. There was no difference in analgesia as assessed by the patients or the investigators. Mild discomfort at removal of the occlusive dressing/patch was observed in a few patients, but there was no difference in the adhesiveness of the Tegaderm dressing and the EMLA patch. Only mild local skin reactions (with paleness in the anaesthetised skin area) were observed in both groups. It was concluded that both the EMLA patch and the Tegaderm/EMLA cream dressing provide effective dermal analgesia for venepuncture with a 0.8 mm (outer diameter) cannula. The two types of application were indistinguishable but the ease of application of the patch is a distinct advantage.     

The control of intra-ocular pressure during the induction of anaesthesia for emergency eye surgery. A high-dose vecuronium technique

A technique of rapid sequence induction of anaesthesia for use in patients with penetrating eye injuries is described. This utilises a three maximal breaths method of pre-oxygenation, the intravenous injection of thiopentone and high dose vecuronium (0.2 mg/kg). Using the loss of eyelash reflex as the starting point for timing, all patients were intubated after 60 seconds without coughing and bucking. No postintubation increases in intra-ocular pressure were seen in 70% of patients and in no patient did the increase in intra-ocular pressure exceed 5 mmHg. After 3 minutes of apnoea, the minimum haemoglobin oxygen saturation was 94% with a mean value of 97.6%.     

Comparison of 0.75% levobupivacaine with 0.75% racemic bupivacaine for peribulbar anaesthesia

In a single centre, randomised, double-blind study 50 patients scheduled for intra-ocular surgery received 0.75% levobupivacaine or 0.75% racemic bupivacaine for peribulbar anaesthesia. There were no significant differences in the mean (SD) volume of levobupivacaine (11 (2.7) ml) or racemic bupivacaine (10 (2.6) ml) required, time to satisfactory block (levobupivacaine-13 (5.6) min; racemic bupivacaine-11 (4.4) min), peri-operative pain scores or frequency of adverse events between levobupivacaine and racemic bupivacaine. The safer side-effect profile of levobupivacaine may offer significant advantages in the elderly population undergoing cataract extraction in whom intercurrent disease is common.     

Plasma concentrations of bupivacaine during extradural anaesthesia for Caesarean section

The clinical effects and plasma levels associated with the use of 0.5% bupivacaine with and without the addition of 1:200,000 adrenaline (5 micrograms/ml) were studied in 30 patients who underwent extradural anaesthesia for elective Caesarean section. The addition of adrenaline to bupivacaine prolongs analgesia, reduces the degree of hypotension and delays its onset. Plasma bupivacaine levels were consistently lower when adrenaline was added, but this difference was significant only at 10 minutes after the initial dose. Prolonging the interval between increments seems to be a more reliable way to reduce plasma concentration than the addition of the catecholamine.     

The effects of vecuronium on intra-ocular pressure

The effects of vecuronium on intra-ocular pressure were investigated in doses of 0.1 mg/kg during steady state anaesthesia (n = 5), 0.1 mg/kg as part of a normal sequence induction preceded by thiopentone (n = 10), and 0.15 mg/kg as part of a rapid sequence induction with vecuronium administered prior to thiopentone (n = 10). Administration of vecuronium during steady state anaesthesia was associated with a significant decrease. Vecuronium produced a small reduction in pressure during a normal sequence induction, following a significant reduction after thiopentone. Tracheal intubation during normal sequence and rapid sequence inductions produced increases in pressure above the pre-intubation value (significantly so in the case of normal sequence induction); however, the intra-ocular pressure always remained below the pre-induction value, which suggests that vecuronium 0.15 mg/kg is a suitable relaxant as part of a rapid sequence induction technique where the use of suxamethonium is contraindicated.     

Subarachnoid block with hyperbaric lignocaine

A double-blind study was carried out in 20 patients to compare 5% hyperbaric lignocaine and 0.5% hyperbaric bupivacaine for subarachnoid block. The injections were made in the lateral position and the patients turned supine immediately. The onset, extent and duration of sensory and motor blockade, the quality of anaesthesia, cardiovascular effects and the frequency of side effects were studied. Cephalad spread of analgesia was high (T4-5) with both solutions. Bupivacaine produced a longer duration of action in the lumbar and sacral segments but the duration in the thoracic segments was similar. There was a considerable degree of hypotension in both groups but this responded readily to ephedrine. Hyperbaric lignocaine is an alternative to hyperbaric bupivacaine and its shorter duration of action in the lumbar and sacral segments is advantageous when a fast recovery is desirable.     

Comparison of hyperbaric and plain bupivacaine with hyperbaric cinchocaine as spinal anaesthetic agents

In a double-blind study, 90 patients (ASA 1 or 2) received spinal anaesthesia with 2 ml hyperbaric cinchocaine 0.5%, 4 ml hyperbaric bupivacaine 0.5% or 4 ml plain bupivacaine 0.5%. All injections were made in the left lateral position, and the patients turned supine immediately. Hyperbaric bupivacaine produced a significantly faster and a higher dermatomal level of bilateral complete sensory blockade than the other solutions (p less than 0.005 for each). The duration of sensory blockade was significantly longer with plain bupivacaine than with either hyperbaric solution (p less than 0.0005). The intensity of sensory blockade was significantly greater with both bupivacaine solutions than with hyperbaric cinchocaine (p less than 0.05). Onset and intensity of motor blockade were similar with all agents, but motor blockade was of significantly shorter duration with hyperbaric bupivacaine than the other agents (p less than 0.0005). Hyperbaric bupivacaine appears to be the best agent for rapid and intense sensory blockade of intermediate duration. Plain bupivacaine is more appropriate if a longer duration of action but a lower height of blockade are required, and has the advantage of less cardiovascular disturbance.     

A comparison of the pharmacodynamics of rocuronium and vecuronium during halothane anaesthesia

Thirty healthy patients were randomised to receive either a single bolus dose of rocuronium 0.6 mg.kg-1 or vecuronium 0.1 mg.kg-1 during halothane anaesthesia. Onset time, duration 25, duration 75 and train-of-four 70 were measured. The onset of neuromuscular blockade following rocuronium was more rapid than vecuronium (p = 0.0001). All other pharmacodynamic parameters were similar. During the first minute following injection of the neuromuscular blocking agent, the heart rate increased by 36% in the rocuronium group but remained stable in those patients who received vecuronium (p = 0.0008). No adverse effects were noted in either group.     

A comparison of lignocaine with prilocaine in axillary brachial plexus anaesthesia

Twenty patients received either lignocaine 1.5% with 1/200,000 adrenaline (group L), or prilocaine 1.5% plain (group P) as a brachial plexus block for surgery to the upper limb, in a randomised double-blind study. The two groups were comparable in age, weight and duration of surgery and there were no significant differences between the two groups with regard to onset, pattern or degree of sensory loss. The degree of motor loss was also comparable. The group L patients had a statistically significant longer duration of sensory loss than those in group P. All the blocks were performed using the same technique and provided complete surgical anaesthesia. Prilocaine 1.5% plain provides adequate sensory and motor blockade for brachial plexus anaesthesia and is a suitable agent for medium duration surgery to the upper limb.