Comparison of articaine and bupivacaine/lidocaine for sub-Tenon's anaesthesia in cataract extraction.

BACKGROUND: Articaine is the most widely used local anaesthetic for dental anaesthesia in Germany, Italy and The Netherlands and has recently been introduced and licensed for dental use in the UK. We have previously shown articaine to be superior to a standard mixture of bupivacaine 0.5%/lidocaine 2% for peribulbar anaesthesia. Sub-Tenon's anaesthesia arguably provides a safer method of anaesthetic delivery for cataract surgery. A blunt cannula is used in this technique, thus greatly reducing the risk of globe perforation, intrathecal injection and sight-threatening periocular haemorrhage. METHODS: We compared articaine and bupivacaine/lidocaine for sub-Tenon's anaesthesia in cataract surgery. RESULTS: Sub-Tenon's anaesthesia using articaine 2% resulted in a more rapid onset of motor block compared with a bupivacaine/lidocaine (P=0.0076). Ocular movement scores were significantly lower from 2 min after injection until the end of surgery (P=0.031 ANOVA). CONCLUSION: Articaine 2% is safe and effective for sub-Tenon's anaesthesia and is a suitable alternative to the traditional bupivacaine 0.5%/lidocaine 2% mixture.

Comparison of articaine and bupivacaine/lidocaine for peribulbar anaesthesia by inferotemporal injection.

BACKGROUND: Articaine is a novel amide local anaesthetic with a shorter duration of action than prilocaine. METHODS: In a randomized, double-blind study we compared the efficacy of 2% articaine with epinephrine 1:200,000 with a mixture of 0.5% bupivacaine and 2% lidocaine with epinephrine 1:200,000 for peribulbar anaesthesia in cataract surgery using a single inferotemporal injection. Eighty-two patients were randomly allocated to one of two groups to receive peribulbar anaesthesia with 6-7 ml of articaine or a bupivacaine/lidocaine mixture. Both solutions contained hyaluronidase 30 iu ml(-1). Ocular movement was scored at 2 min intervals up to 10 min, at the end of surgery and at time of discharge from hospital. Time to readiness for surgery and any complications (proptosis, chemosis, pain) were recorded. RESULTS: The articaine group demonstrated a rapid onset of peribulbar block with mean time (SD) to readiness for surgery of 4.2 (4.5) min compared with 7.2 (5.7) min in the bupivacaine/lidocaine group (P=0.0095). The block obtained in the articaine group was dense with eye movement scores at 2, 4, 6, 8 and 10 min all significantly reduced (P<0.01 at each interval). There was also a faster offset of the block in the articaine group (P=0.0009). There was no difference in incidence of minor complications between the groups. CONCLUSIONS: Two per cent articaine is safe and effective for peribulbar anaesthesia by inferotemporal injection and is a suitable alternative to the traditional mixture of 0.5% bupivacaine and 2% lidocaine.

Comparison of articaine and bupivacaine/lidocaine for single medial canthus peribulbar anaesthesia.

In a single-centre, randomized, double-blind study, we compared the efficacy of 2% articaine with that of a mixture of 0.5% bupivacaine and 2% lidocaine for peribulbar anaesthesia in cataract surgery, using a single medial canthus injection technique. Eighty-two patients were allocated randomly to receive 7-9 ml of a mixture of 0.5% bupivacaine and 2% lidocaine or an equal volume of 2% articaine with 1:200,000 epinephrine. Hyaluronidase 30 iu ml(-1) was added to both solutions. The degree of akinesia was scored 1, 5 and 10 min after the block, at the end of surgery and at discharge from the day case unit. Primary outcome measures were the difference in ocular movement scores 5 min after block and the need for supplementary inferolateral injections. There was greater akinesia in the articaine group at 5 min (P=0.01). Ten patients (24%) in the articaine group and 21 patients (51%) in the bupivacaine/lidocaine group required a supplementary injection (P=0.02). The mean (SD) volume of local anaesthetic required to achieve adequate block for surgery was 9.7 (2.1) ml in the articaine group and 11.0 (2.2) ml in the bupivacaine/lidocaine group (P=0.01). There was a faster offset of akinesia after surgery in the articaine group (P=0.01). There were no differences between groups in the incidence of reported pain or of minor complications. In our study, 2% articaine with 1:200,000 epinephrine was safe and efficacious for single medial canthus peribulbar anaesthesia.

Effect of L-lysine on nitric oxide production in ovine endotoxaemia.

Excess production of nitric oxide contributes to the refractory hypotension associated with sepsis and is dependent upon precursor availability, L-arginine. Endothelial uptake of L-arginine by the y+ transporter can be inhibited by another cationic amino acid, L-lysine. This study was undertaken to determine the effects of L-lysine in an anaesthetized ovine model of endotoxaemia in which nitric oxide production is known to be limited by L-arginine availability. The haemodynamic effects of i.v. L-lysine (500 mg kg-1) were compared with those of a known inhibitor of nitric oxide synthase, NG-nitro-L-arginine-methyl ester, L-NAME (25 mg kg-1) and with control animals (n = 6 per group). Serum nitrates, the stable end metabolite of nitric oxide production, were also measured. L-NAME administration caused a significant increase in systemic and pulmonary vascular resistance (P < 0.0001), mean arterial pressure (P < 0.0001) and a reduction in serum nitrate concentrations (P < 0.0001). The administration of L-lysine had no effect on systemic or pulmonary vascular resistance, mean arterial pressure or serum nitrate concentrations. We conclude that the administration of L-lysine does not inhibit nitric oxide production in this model.

Elevated levels of serum nitrate, a stable end product of nitric oxide, in women with pre-eclampsia.

OBJECTIVES: Nitric oxide released from vascular endothelial cells is a potent vasodilator and inhibits platelet adhesion. It has been suggested that decreased nitric oxide production from dysfunctional endothelial cells is implicated in the pathophysiology of pre-eclampsia. In this study evidence was sought for abnormal production of nitric oxide in pre-eclamptic women. PARTICIPANTS: Blood was collected from 20 women presenting with pre-eclampsia, from 20 matched healthy pregnant controls and from 12 nonpregnant women of childbearing age. METHODS: Serum nitrate, the stable end metabolite of nitric oxide, was measured by vanadium III chloride reduction and chemiluminescence. RESULTS: Sera from women with pre-eclampsia had significantly higher nitrate concentrations (mean 47.4 mumol/L [SD 13.6]) compared with healthy pregnant (mean 31.2 mumol/L [SD 9.14]) and nonpregnant (mean 32.1 mumol/L [SD 10.0]) controls. CONCLUSIONS: These results do not support the hypothesis that decreased endothelial cell nitric oxide production may be important in the pathophysiology of pre-eclampsia. On the contrary, serum nitrate levels are increased which may reflect either increased production of nitric oxide from an unidentified source or decreased elimination through the kidneys.

Predictors of postoperative myocardial ischaemia. The role of intercurrent arterial hypertension and other cardiovascular risk factors.

One hundred and eighty-three patients were studied to examine the role of a number of risk factors in the development of silent ischaemia after general anaesthesia for general and vascular surgery. We collected evidence of cardiovascular risk factors using a binary questionnaire. The patients were monitored pre- and postoperatively using a Holter ECG monitor. Usable data were collected on 140 patients. Pre-operative silent myocardial ischaemia was found to be strongly associated with postoperative silent myocardial ischaemia (odds ratio: 10.8, 95% confidence intervals: 3.8-30.7). A history of hypertension, indicated by treatment with antihypertensive drugs, was associated with increased risk (odds ratio: 2.58, 95% confidence intervals: 1.12-5.96). A linear trend was found for risk associated with increasing admission systolic blood pressure (odds ratio: 1.20 for each 10-mmHg increase in systolic pressure, 95% confidence intervals: 1.01-1.42). An association between vascular surgery and postoperative silent myocardial ischaemia was also confirmed (odds ratio: 2.36, 95% confidence intervals: 1.1-5.1).

L-arginine augments nitric oxide production and mesenteric blood flow in ovine endotoxemia.

We studied the effects of administrating the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), or the nitric oxide precursor, L-arginine, on hemodynamic variables and serum nitrate concentrations in an anesthetized ovine model of endotoxemia to assess the effects on regional visceral blood flow and to determine whether L-arginine availability limits nitric oxide production. Animals received Escherichia coli endotoxin (2 micrograms/kg) followed 2 h later by L-NAME (25 mg/kg), L-arginine (0.575 g/kg), or saline administered over 1 h followed by an infusion of the same dose over 8 h (n = 6 per group). Renal and mesenteric blood flow were measured by placement of electromagnetic flow probes, and serum nitrate concentrations were determined using vanadium III chloride or nitrate reductase reduction to nitric oxide or nitrite, respectively. The results showed L-NAME significantly increased systemic vascular resistance (P < 0.01), decreased serum nitrate concentrations (P < 0.05), and caused a transient reduction in mesenteric blood flow (P < 0.05). L-Arginine caused a reduction in systemic vascular resistance (P < 0.01), increased mesenteric blood flow (P < 0.001) and conductance (P < 0.05). There were no significant changes in renal arterial blood flow in either group. We conclude that the availability of L-arginine limits nitric oxide production in endotoxemia and, furthermore, that L-arginine administration in this model causes significant mesenteric vasodilatation. L-NAME administration had only limited effect on visceral blood flow despite a marked increase in systemic vascular resistance and a reduction in nitric oxide production.

Effects of oxygen and nitric oxide in oxygen on pulmonary arterial pressures of children with congenital cardiac defects.

Inhaled nitric oxide is a specific pulmonary vasodilator. This study was undertaken to assess the effect on pulmonary arterial pressure of administering 100% oxygen compared with nitric oxide in oxygen. Thirteen mechanically ventilated children undergoing routine cardiac catheterization for the investigation of congenital heart disease were studied. Pulmonary arterial pressures were measured during inhalation of 30% oxygen (baseline), 100% oxygen, and nitric oxide (40 parts per million) in oxygen. In addition, in six children the pulmonary/systemic blood flow ratio and pulmonary vascular resistance were calculated using oxygen content, an assumed value for oxygen uptake, and the Fick principle. Results were compared using analysis of variance and the Wilcoxon signed-rank test. Pulmonary arterial pressure decreased from a mean value of 29.5 mmHg (SD 15.1) to 25.6 mmHg (SD 9.3), p = 0.048, after increasing the inspired oxygen fraction from 0.3 to 1.0. The addition of nitric oxide caused a further reduction to 22.9 mmHg (SD 7.9), p = 0.0001. There was no change in systemic arterial pressure or heart rate during the study period, but a small increase occurred in the mean methemoglobin level (1.1% to 1.3%) p = 0.039. Changes in the pulmonary/systemic blood flow ratio and pulmonary vascular resistance (n = 6) were not significant. Nitric oxide in oxygen appears to be a more potent pulmonary vasodilator than oxygen alone in pediatric patients with congenital cardiac defects.

The effect of cricoid pressure application on airway patency.

STUDY OBJECTIVE: To assess the incidence of upper airway obstruction associated with the application of cricoid pressure (Sellick's maneuver) by experienced anesthetists. DESIGN: Randomized, blinded study. SETTING: Anesthetic rooms at John Radcliffe Hospital, Oxford, United Kingdom. PATIENTS: Fifty ASA I patients undergoing routine general anesthesia for elective surgery requiring tracheal intubation. INTERVENTIONS: Following induction of anesthesia and muscle relaxation, a senior anesthetist applied cricoia pressure in the manner described by Sellick. Patients were ventilated with or without cricoid pressure, with the order of intervention randomized, and the observer blinded to all maneuvers. MEASUREMENTS AND MAIN RESULTS: Effect on airway patency was assessed by measuring expired tidal volume (VT) and peak inspiratory pressure (PIP) when ventilated using a face mask with and without cricoid pressure applied, and with and without an oropharyngeal airway in place. Application of cricoid pressure caused a significant reduction in mean expired VT (p < 0.001) and a significant increase in PIP (p < 0.001) compared with control values. Complete airway occlusion occurred in 11% of applications. CONCLUSIONS: The use of manual cricoid pressure, even by experienced anesthetists, causes a degree of airway obstruction and can cause complete airway occlusion.

Resistant hypertension and preoperative silent myocardial ischaemia in surgical patients.

We studied 325 patients undergoing elective noncardiac surgery who had preoperative ambulatory ECG monitoring performed for a duration of 5130 h (range 8-24 h; mean 15.8 h). Sixty-four subjects (20%) had one or more episodes of ST segment depression consistent with myocardial ischaemia. Of all preoperative cardiovascular variables measured, the presence of elevated arterial pressure, despite patients being maintained on long term antihypertensive therapy, was the only factor associated significantly with the presence of preoperative silent myocardial ischaemia (P < 0.002). This correlation was confirmed when arterial hypertension was defined in four separate ways. The incidence of silent ischaemia in these patients was 33-55%. We suggest that admission arterial pressure may therefore be a useful screening test to identify patients at risk of preoperative myocardial ischaemia.

Nitric oxide treatment for fulminant pulmonary hypertension.

A 3 year old child with known pulmonary haemosiderosis suffered acute circulatory collapse secondary to raised pulmonary vascular resistance. Nitric oxide inhalation produced a profound improvement in circulatory parameters and gaseous exchange. Nitric oxide may have a therapeutic role in acute pulmonary hypertensive crisis.