Amnesia for dental procedures and mood change following treatment with nitrous oxide or midazolam

Fifty-eight patients undergoing restorative dental treatment at Guy's Hospital had been previously allocated on the basis of clinical assessment, including that of their dental anxiety, to treatment under local anaesthetic alone or in combination with i.v. midazolam or inhalation nitrous oxide. They were tested before and after dental treatment to determine their memory of dental procedures and changes in mood and bodily symptoms. The patients allocated to the midazolam treatment had significantly higher pre-treatment scores on the Bond & Lader mood factors of "anxiety" and "discontent". All the groups showed significant pre- to post-treatment reductions in sweating, palpitations, restlessness, dry mouth, muscular tension, nausea, loss of appetite and upset stomach and the extent of these reductions were not different for the different treatments. Midazolam treatment resulted in significantly greater reductions in self-ratings of bodily symptoms of anxiety, shaking and trembling compared with the control (local anaesthetic) group. Nitrous oxide resulted in a significant reduction in irritability, compared with controls. Both midazolam and nitrous oxide significantly reduced the patients' memory of the dental procedures and the impairments in memory were independent of any changes in anxiety or sedation. Of the items remembered there were no differences between the groups in their ratings of how well explained, how pleasant or unpleasant, or how painful the procedures were.

Response of laryngeal receptors to water solutions of different osmolality and ionic composition

Water-responsive laryngeal receptors with fibres in the superior laryngeal nerve were studied to characterize the specific physicochemical properties of aqueous solutions that activate these endings. The responses to water (37 degrees C) of 141 receptors were studied in 39 anaesthetized dogs breathing through a tracheostomy with the larynx functionally isolated. Of the 89 receptors stimulated by water, 53 were also challenged with isosmotic (275-315 mOsm) solutions of dextrose and sodium gluconate at 37 degrees C. Receptors that only responded to water (n = 31) with a long delay, long duration discharge were generally respiratory modulated. On the other hand, laryngeal receptors that responded to all test solutions (n = 22) with a short delay, short duration discharge were generally not respiratory modulated. We conclude that the former type of receptor responds to lower osmolality, whereas the latter responds to the lack of chloride ions in the test solutions. These two types of receptor may be responsible for the cough and bronchoconstriction induced by inhaled aerosols of different osmolalities and ionic compositions.

An evaluation of lidocaine hydrocarbonate compared with lidocaine hydrochloride for inferior alveolar nerve block

The purpose of this study was to measure the degree of anesthesia obtained with 2.2% lidocaine hydrocarbonate, 2.2% lidocaine hydrocarbonate with 1:100,000 epinephrine, and 2% lidocaine hydrochloride with 1:100,000 epinephrine for inferior alveolar nerve block. Using a repeated-measures design, 30 subjects randomly received an inferior alveolar injection of each solution over the course of three successive appointments. The first molar, first premolar, lateral incisor, and contralateral canine (control) were blindly tested with an Analytic Technology pulp tester at 3-min cycles for 60 min. Anesthetic success was defined as no subject response to the maximum output (80 reading) of the pulp tester within 16 min and maintenance of this reading for the remainder of the testing period. Although subjects felt numb subjectively, anesthetic success as defined here ranged from 3% to 10% for the plain lidocaine hydrocarbonate; for the lidocaine hydrocarbonate and lidocaine hydrochloride solutions with epinephrine, success ranged from 37% to 63%. We conclude that 2.2% lidocaine hydrocarbonate without vasoconstrictor is not as effective as the other two preparations for inferior alveolar nerve block. The 2.2% lidocaine hydrocarbonate with epinephrine and 2%.

A quantitative double-blind evaluation of the antinociceptive effects of perineurally administered morphine compared with lidocaine

In two double-blind, placebo-controlled investigations, morphine and lidocaine were administered perineurally to the ulnar nerve. Thresholds (warmth and pain) and pain-evoked brain potentials (amplitude and latency) to argon laser stimulation were measured up to 120 min after the injection. Hypalgesia to laser pain was detected 15 min after the injection of morphine and 5 min after the injection of lidocaine. The duration of hypalgesia and analgesia was less than 15 min for morphine and 85 min for the lidocaine injection. Both morphine and lidocaine increased the latency of the brain potentials, which indicates that the same blocking mechanisms could be involved. Pin-prick analgesia was obtained 5 min after the injection of lidocaine, but 15-30 min elapsed before the laser pain was inhibited maximally. Laser pulses can activate larger skin areas than needle pricks, indicating that a central summation of the activity from many cutaneous nociceptors is important in order to obtain a reliable indicator of adequate analgesia.

[Analysis of failures of spinal anesthesia as a function of practice development in a university hospital]

This study is a retrospective analysis of 303 consecutive spinal anaesthesia performed in orthopaedic patients of a University Hospital between January and December 1990. Failure of spinal anaesthesia was defined as the requirement for general anaesthesia to perform surgery. The parameters studied as possible risk factors of failure were patients demographics, local anaesthetic agents and solutions and techniques of spinal anaesthesia (single injection versus continuous spinal anaesthesia). Failures were related to inadequate or incomplete extension of sensory blockade or to difficulties to perform spinal injection. Continuous spinal anaesthesia was performed in 209 patients mostly with 0.5% isobaric bupivacaine, while 94 patients received a single injection of either hyperbaric 0.5% tetracaine with adrenaline or 0.5% bupivacaine or 5% lidocaine. Failures occurred in 6.3% of the cases but were significantly less frequent with continuous spinal anaesthesia (4.8%) than with the conventional technique (9.6%). The incidence of failure was higher with hyperbaric tetracaine (11.1%) confirming its poor reliability. Inadequate extension of the anaesthetic block was the main cause of failure whatever the spinal anaesthetic technique. These results point out the reliability of continuous spinal anaesthesia but problems may occasionally occur due to spinal catheter misplacement.

Mapping in the atrioventricular junction

Ectopic conduction is defined as the premature exit of the cardiac impulse from the specialized conduction system across a damaged Purkinje-ventricular muscle interface. This anomalous form of atrioventricular (AV) conduction was induced in the dog heart by lidocaine injection of the His bundle-interventricular septum interface and by ischemic damage of the AV junction subsequent to anterior septal artery ligation in the dog heart. The electrocardiogram (ECG) manifestation of ectopic conduction is the loss of initial forces and replacement of the Q waves with delta waves. In order to verify these effects, the authors devised a multi-electrode, malleable plaque (63 electrode sites) that could be secured at the AV junction during venous occlusion in the open-chest, anesthetized dog. Preliminary maps indicated a dramatic change in activation that proceeded from apex to base of the heart in the control state and reversed after ischemic damage to the His bundle. In vitro, it was possible to induce ectopic conduction by lidocaine injection at the interface of the right bundle branch and septal muscle. Microelectrode studies demonstrated that foot potentials, for example, electrotonic, or subthreshold potentials mediated the connection from Purkinje to muscle in the damaged zone. In a recent set of experiments in vivo, subthreshold stimulation (STS) was delivered to simulate electrotonic potentials to the His bundle region, and right ventricular apex, using multipolar electrode catheters. In the normal heart, STS delivered as DC constant current or pulse trains (1000 Hz, 50 ms pulse duration) induced shortened P-R intervals and delta waves with or without bundle branch block patterns.(ABSTRACT TRUNCATED AT 250 WORDS)

[Ocular circulatory changes caused by retrobulbar anesthesia with and without added adrenaline]

In 80 patients, retrobulbar anesthesia (RBA; 5 ml of a lidocaine-bupivacaine mixture with hyaluronidase) with or without addition of adrenaline (after-mixing concentration 1:500,000) was performed preoperatively. In 2 examination series, the acute and medium-term effects of RBA on the following ocular circulatory variables were investigated: ocular pulsation volume (PVoc), systolic ciliary and retinal perfusion pressures or blood pressures, respectively (method: oculo-oscillo-dynamography).

RESULTS

RBA with adrenaline: Directly after injection, PVoc was reduced by an average of 49%, the ocular perfusion and blood pressures were lowered by averages of 8.0 and 4.3 mmHg, respectively, and the intraocular pressure (Pio; hand-applanation tonometer) was elevated by 3.5 mmHg. 15 min after injection, PVoc and the ocular perfusion and blood pressures were even slightly more reduced, whereas Pio had reassumed its pre-injection level. RBA without adrenaline: During both time periods after injection, the reduction of PVoc averaged 10% less compared to RBA with adrenaline. The changes in ocular perfusion and blood pressures and in Pio, however, were not significantly different from RBA with adrenaline.

CONCLUSIONS

The lowering of PVoc--which variable is determined mainly by the pulsatile choroidal blood flow--in concert with the lowered ciliary perfusion and blood pressures is indicative of a reduced ciliary blood flow during RBA. Because of the decreased retinal perfusion and blood pressures, there is also a higher risk of reduced blood supply to the retina. Only to some degree, the observed inhibitory RBA effects on ocular circulation can be explained by adrenaline, and to an even smaller degree by the only transient Pio elevation.

Fetal heart rate variability after epidural fentanyl during labor

The effects of epidural fentanyl on fetal heart rate (FHR) were examined in 39 parturients, 19 given 75 micrograms epidural fentanyl and 20 given normal saline in 5-mL volumes administered randomly after establishment of adequate epidural lidocaine analgesia. Fetal heart rate was measured 15 min before and 15 min after lidocaine epidural analgesia, and for 60 min at 5-min intervals after administration of epidural fentanyl/placebo. A perinatologist blinded to the injected epidural solution analyzed FHR tracings. Epidural injections of fentanyl and saline, when given during established epidural lidocaine analgesia, were associated with equal reductions in FHR variability and the frequency of FHR accelerations (P less than 0.003). Neonatal outcome was also similar in both groups. The clinical significance, if any, of these moderate reductions in FHR during epidural lidocaine analgesia is unclear.

Buffered versus plain lidocaine as a local anesthetic for simple laceration repair

STUDY OBJECTIVE

Buffered lidocaine was compared with plain lidocaine as a local anesthetic for simple lacerations.

DESIGN

Randomized, double-blind, prospective clinical trial.

SETTING

Urban emergency department.

TYPE OF PARTICIPANTS

Ninety-one adult patients with simple linear lacerations were enrolled. Patients with allergy to lidocaine and patients with an abnormal mental status were excluded.

INTERVENTIONS

Each wound edge was anesthetized with either plain or buffered lidocaine using a randomized, double-blind protocol. The pain of infiltration was measured with a previously validated visual analog pain scale.

MEASUREMENTS AND MAIN RESULTS

Analysis of pooled data and paired data (using patients as their own controls) revealed that infiltrating buffered lidocaine was significantly less painful than plain lidocaine (P = .03 and P = .02, respectively). There was no significant difference in the anesthetic effectiveness of the two agents during suturing.

CONCLUSION

Buffered lidocaine is preferable to plain lidocaine as a local anesthetic agent for the repair of simple lacerations.

Cervical analgesic facet joint arthrography

We report on our experience with cervical analgesic facet joint arthrography in 11 patients (30 joints), of whom nine had previous spinal surgery. In this type of patient we have found the procedure to be a diagnostic test as well as a preoperative guide to the neurosurgeon, but not a permanent therapy.

Arthroscopic surgery of the knee under local anesthesia

This report delineates the efficacy of local anesthesia in the performance of arthroscopic surgery of the knee. A retrospective review of 500 cases revealed that only three required administration of general anesthesia to successfully complete the procedure. A prospective study comparing fentanyl, midazolam, and fentanyl/midazolam combinations as intravenous supplements was performed. Meticulous surgical technique combined with local anesthesia and some form of intravenous sedation in minimal therapeutic dosage will provide satisfactory conditions to perform surgical arthroscopy of the knee.

Iontophoresis for eyelid anesthesia

Local anesthesia is appropriate for eyelid surgery, but patients fear the pain of injections. We evaluated iontophoresis of lidocaine for eyelid skin anesthesia to pinprick pain sensation in normal subjects, and prior to regional infiltration of the anesthetic agent in patients undergoing eyelid surgery. After iontophoresis of lidocaine hydrochloride 4% solution to one randomly chosen eyelid, pinprick skin sensation was tested in a double-masked manner. Subjective pain scores of 10 subjects were significantly less (P less than .008) on the iontophoresis treated eyelids (0.25) than on the untreated eyelids (2.55). Nine patients undergoing bilateral upper eyelid surgery had iontophoresis applied to one randomly chosen eyelid prior to the usual anesthetic injections. In this double-masked evaluation, patients reported significantly less pain (P less than .02) on the treated eyelids (1.4) than on the untreated eyelids (4.7). We conclude that iontophoresis is effective for achieving short-term, superficial anesthesia of eyelid skin.

[Changes in systemic circulation under induced total spinal block and choice of vasopressors]

Total spinal block by using 2% lidocaine 0.5 ml.kg-1 (10.0 mg.kg-1) was carried out in adult mongrel dogs. The effects of atropine 0.02 mg.kg-1, isoproterenol 0.5 mcg.kg-1, methoxamine 0.1 mg.kg-1 and ephedrine 0.5 mg.kg-1 to counteract circulatory changes by total spinal block were studied. Atropine did not exert any marked influence on circulatory system. Isoproterenol elevated HR, LV dp/dt max and CI temporarily, but did not decrease MAP and SVR. Methoxamine elevated MAP and SVR, but decreased CI. Ephedrine is a drug of choice for this situation because it elevated HR, MAP, LV dp/dt max and SVR.

Effects of 2% lignocaine on somatosensory evoked potentials recorded in the extradural space

We have studied the effects of extradural administration of 2% lignocaine at the L3-4 interspace on somatosensory evoked potentials recorded in the cervical extradural space before corrective surgery for idiopathic adolescent scoliosis. Eight patients in whom the equivalent volume of 0.9% sodium chloride solution was administered into the lumbar extradural space acted as a control group. Lignocaine 2% resulted in a decrease in overall amplitude, but its main effect was a significant decrease in the amplitude of the second and third peaks, suggesting an action on the dorsal columns of the spinal cord. A significant increase in latency was found in both the lignocaine and sodium chloride groups. We conclude that the use of extradural 2% lignocaine in patients undergoing scoliosis surgery may interfere with the intraoperative monitoring of somatosensory evoked potentials.

[Heart arrest during spinal anesthesia for transurethral resection of the prostate. Apropos of a case]

We report a cardiac arrest in a 66 years healthy patient during a spinal anesthesia for a transurethral resection of prostate. The accident occurred one hour and fifteen minutes after the subarachnoidal injection of hyperbaric lidocaine 80 mg, at the end of surgery, but before any postural change. We attempt to elucidate the surgical or anesthesiologic precipitating factors that lead to the cardiac arrest in this patient. However, there was no real etiology that formally explained the genesis of the accident. This case is to add to a series of recently published accidents that occurred during spinal anesthesia in healthy patients.

Myocardial preservation using lidocaine blood cardioplegia

Prevention of ventricular fibrillation after aortic unclamping using lidocaine hydrochloride as an additive to cold potassium blood cardioplegia was studied prospectively in 46 patients undergoing elective myocardial revascularization. Patients were similar with respect to age, ventricular function, severity of coronary artery disease, cross-clamp time, completeness of revascularization, frequency of internal thoracic artery grafting, systemic temperature at the time of cross-clamp removal, and mean infusate volume and temperature. Patients receiving lidocaine blood cardioplegia (group 1, 23 patients) had a significant reduction in the incidence of ventricular fibrillation (22% versus 74%; p less than 0.0005) and in the mean number of cardioversion attempts required to defibrillate the heart (0.5 +/- 1.3 versus 1.9 +/- 0.97; p less than 0.0005) after cross-clamp removal compared with controls (group 2, 23 patients). There were no differences between the two groups postoperatively with regard to cardiac enzyme release, hemodynamic measurements, or clinical outcome. Patients receiving lidocaine blood cardioplegia tended to have a lower incidence of new postoperative atrial fibrillation (9% versus 26%). Ventricular function was preserved equally in both groups. We conclude that lidocaine is a safe additive to potassium blood cardioplegia and significantly reduces the incidence of ventricular fibrillation after aortic unclamping.

A comparison of epidural narcotics, with and without a test dose, to epidural lidocaine for extracorporeal shock wave lithotripsy

We sought to compare epidural lidocaine to several short-acting epidural narcotics for their efficacy in controlling pain during extracorporeal shock wave lithotripsy (ESWL), hemodynamic changes, side effects and patient acceptance. To determine what contribution, if any, the local anesthetic test dose makes to the above factors, we also compared epidural sufentanil with and without a preceding test dose of local anesthetic with epinephrine. One hundred ASA I-III patients scheduled for elective ESWL were divided equally into five groups to receive one of the following epidural drugs through an epidural catheter: 2% lidocaine with 1:200,000 epinephrine (Group L), 1000 micrograms alfentanil (Group A), 200 micrograms fentanyl (Group F) or 60 micrograms sufentanil (Groups S and S-). Group S- differed from all other groups in omission of the test dose and direct injection of the opioid through the epidural needle. Significant hypotension occurred in 20% of patients in Group L compared to 0% in the narcotic groups (p less than 0.01). Clinically significant respiratory depression was not observed in any group. Mild pruritus was observed in up to 60% of patients in the narcotic groups (p less than 0.01). Sedation was observed in all of the narcotic groups, particularly in Group S-, in which more than half of patients were drowsy (p less than 0.05). Requirements for adjuvant analgesics during ESWL were highest in Group A. Patient acceptance was high throughout the study. We conclude that epidural alfentanil, fentanyl and sufentanil are as effective as epidural lidocaine plus epinephrine in providing analgesia during ESWL.(ABSTRACT TRUNCATED AT 250 WORDS)

Tubeless anaesthesia for microlaryngeal surgery

An anaesthetic technique for laryngeal microsurgery is described and evaluated using intravenous propofol infusion and topical lignocaine with the patient breathing spontaneously without an endotracheal tube. Eighty adult patients divided into two groups according to their ASA status (Group A; 58 ASA I and II; Group B; 22 ASA III and IV) were analysed. Operating conditions were good in all but one case. Good anaesthesia was achieved in about 70% of patients. The requirement for propofol was less in Group B. Blood pressures decreased significantly following induction (P less than 0.001) but returned towards the preoperative values after ten minutes in Group A patients whereas the recovery was slower in Group B. Apnoea occurred on induction in about 40% of patients overall. PaCO2 showed a similar small increase in both groups. Oxygenation was adequate. The results show that propofol as an infusion in this simple tubeless technique is satisfactory. As the technique was considered potentially hazardous in those patients with upper airway obstruction, such patients were not included in this study.

Iatrogenic contamination of multidose vials in simulated use. A reassessment of current patient injection technique

An investigation of the potential spread of iatrogenic infections through contaminated multidose vials was performed. Contamination of a multidose vial was hypothesized to occur after a single syringe is used to inject an infected patient with medication, and the same syringe subsequently is used to withdraw additional medication from the multidose vial. If the contaminated multidose vial is used for another patient, an iatrogenic infection may be spread. Laboratory study of this injection technique found that viral plaque-forming units could be transmitted to a multidose vial in this manner. A survey of 100 fellows of the American Academy of Dermatology from the United States found that 24% of the respondents used this potentially unsafe procedure. The potential for iatrogenic spread of the human immunodeficiency virus and hepatitis B virus is described. Recommendations to avoid patient infection are made.

End-tidal carbon dioxide monitoring during awake blind nasotracheal intubation

STUDY OBJECTIVE

To test the usefulness of the end-tidal carbon dioxide monitor in facilitating awake blind nasotracheal intubation in patients with potentially difficult airways.

DESIGN

Randomized, controlled comparison of regimen.

SETTING

Inpatient surgery clinic at a university hospital.

PATIENTS

Sixty-one consecutive patients with potentially difficult airways.

INTERVENTIONS

After airway anesthesia with 4% lidocaine was administered to all patients, either fentanyl and diazepam (n = 30) or fentanyl alone (n = 31) was given intravenously before the awake blind nasotracheal intubation procedure.

MEASUREMENTS AND MAIN RESULTS

End-tidal carbon dioxide concentration, arterial blood pressure, heart rate, and arterial oxygen saturation (by pulse oximeter) were measured in each patient during the awake blind nasotracheal intubation procedure. The day after anesthesia and surgery, each patient was asked to assess the degree of discomfort experienced during the procedure. In 54 of 61 patients, the end-tidal carbon dioxide monitor facilitated awake blind nasotracheal intubation. End-tidal carbon dioxide was significantly higher in patients given both fentanyl and diazepam than in those given fentanyl alone (7.4% +/- 1.4% vs 5.9% +/- 0.9%, respectively; p less than 0.05), but no patient in either group recalled the awake intubation as extremely uncomfortable.

CONCLUSIONS

Monitoring of end-tidal carbon dioxide is useful and valuable in both facilitating blind nasotracheal intubation and avoiding profound hypoventilation.

Cardiopulmonary effects of epidurally administered xylazine in the horse

This study was designed to determine whether the epidural administration of an alpha2 agonist, xylazine, would produce measurable changes in arterial blood pressure, electrocardiographic (ECG) activity and arterial blood gas values in horses. Six horses were given each of four treatments: epidural xylazine, intravenous xylazine, epidural lidocaine and epidural saline. A carotid artery catheter was used to measure arterial blood pressure and to collect samples for blood gas analysis before treatment and at intervals post treatment. Heart rate, arterial pressures, ECG activity and respiratory rate were recorded at the same intervals. No significant changes were recorded between time intervals or between individual treatments. It was concluded that this method of xylazine administration to horses produced potent caudal analgesia without measurable cardiopulmonary effects.

Fourier analysis of the relation between the discharge of quadriceps motor units and periodic mechanical stimulation of cat knee joint receptors

It has been widely assumed that joint receptors contribute to the reflex regulation of movement and posture, although there have been few clear demonstrations of joint-mediated reflex actions on alpha-motoneurones other than those attributable to flexor reflex afferents. The present study extends our recent work on joint-mediated reflexes by using Fourier analysis of spike train interactions to demonstrate that restricted mechanical activation of a small number (one to five) of knee joint receptors by localized indentation of the joint capsule can modify the firing pattern of quadriceps motoneurones in decerebrated cats. The modulation of this discharge pattern can be reversibly abolished by application of droplets of lignocaine directly to the joint nerve and consequently can be attributed unambiguously to articular afferents. Activation of single joint afferents could on occasion produce changes in motor unit firing patterns, but usually activation of two or more was required before secure effects were observed. Increasing the intensity of indentation (resulting in activation of greater numbers of joint receptors) increases the strength of coupling between joint afferent input and motor unit responses, although the relationship is not linear. The relation between the discharge patterns of pairs of motor units was also examined, and it was found that significant coupling occurred at the stimulus frequency, superimposed on a 'background' coupling from unidentified sources. The phase relationship between pairs of motor units was not affected by the periodic stimulus. However, it was observed that if two motor units were firing independently of one another in the absence of capsule probing, maintained capsular indentation produced a striking synchronization between the discharges of the two motor units. These experiments show strong joint-mediated reflex effects on motor unit firing indicating that joint receptors may have an important role to play in motor control.

Comparison of four local extradural anaesthetic solutions for elective caesarean section

We have examined a combination of two local anaesthetics to see if the resultant solution is superior to the agents individually. This study shows that a mixture of bupivacaine and lignocaine provided an excellent alternative to bupivacaine alone, and was superior to 2% lignocaine with adrenaline for elective Caesarean section. By reducing the dose of bupivacaine used, the combination may reduce the risk of cardiotoxicity.