Thomas D. McSweeney

Comparison of effects of lidocaine hydrochloride, buffered lidocaine, diphenhydramine, and normal saline after intradermal injection

STUDY OBJECTIVE To evaluate pain and the spread of analgesia when local anesthetics are given as an intradermal injection into the dorsal aspect of the hand. DESIGN Randomized, double-blinded, placebo-controlled study. SETTING University medical center. PATIENTS 40 consenting adult volunteers. INTERVENTIONS Volunteers were randomly assigned to receive a 0.25-mL injection of either lidocaine hydrochloride (1%), buffered lidocaine, diphenhydramine (1%), or placebo (0.9% sodium chloride solution) into the dorsal aspect of both hands. MEASUREMENTS The volunteers used a visual analog scale to compare the pain of needle insertion and solution injection. Then at 1, 2, 5, 10, 20, and 30 minutes after intradermal injection, the extent of the analgesic area was marked on a strip of tape placed horizontally across the hand. Then at 32 minutes after intradermal injection, the extent of the analgesic area was marked on a strip of tape placed vertically across the hand. The volunteers were called each day and asked the duration of their numbness or hyperesthesia until their hands were no longer numb or sore. MAIN RESULTS Buffered lidocaine during intradermal infiltration was found to be significantly (p < 0.05) less painful than either lidocaine hydrochloride or diphenhydramine and equivalent to placebo. Diphenhydramine and lidocaine hydrochloride during intradermal infiltration induced significantly (p < 0.05) more pain than buffered lidocaine or placebo. Lidocaine hydrochloride displayed a significantly (p < 0.05) larger diameter of analgesia than placebo by 1 minute after the injection, buffered lidocaine by 2 minutes after injection, and diphenhydramine by 5 minutes after injection. By 20 minutes after injection, diphenhydramine diameter of analgesia was significantly (p < 0.05) larger than placebo but significantly less than buffered lidocaine. By 30 minutes after injection, diphenhydramine diameter of analgesia was equivalent to placebo whereas buffered lidocaine and lidocaine diameters were still significantly (p < 0.05) larger than placebo. Diphenhydramine injection resulted in numbness that lasted significantly (p < 0.05) longer than other study solutions whereas buffered lidocaine and lidocaine injections resulted in numbness that lasted significantly longer than placebo. Diphenhydramine injection resulted in hyperesthesia that lasted for 2 or more days in 12 of the volunteers. CONCLUSION There is a reduction of infiltration pain using buffered lidocaine as opposed to lidocaine and diphenhydramine. Although lidocaine injection resulted in a slightly faster spread of analgesic diameter, buffered lidocaine was equivalent to lidocaine from minute 2 until minute 30. Therefore, to obtain optimal anesthetic conditions, we recommend that buffered lidocaine be given 2 minutes before performing catheterization, whereas diphenhydramine should be given 5 minutes before catheterization, but only when buffered lidocaine cannot be used.

Lidocaine local anesthesia for arthroscopic knee surgery

Forty-five patients were evaluated during knee arthroscopy performed using local anesthesia produced by lidocaine with epinephrine to determine the dose-response relationship for operative analgesia. Serum lidocaine concentrations were also measured. Patients were randomized prospectively to receive 20 mL of 0.5%, 1.0%, or 1.5% lidocaine with epinephrine intraarticularly. Intraoperative discomfort was measured by verbal response on an 11-point linear pain scale. Pain scores were significantly higher in patients receiving 0.5% lidocaine during the first 45 min of surgery (P = 0.03). After 45 min, pain scores continued to be higher in the 0.5% lidocaine group than in the 1.0% or 1.5% groups, but the differences were not statistically significant. Ninety-four percent of patients in the 1.5% lidocaine group were willing to repeat this anesthetic technique for surgery compared with 83% of those in the 1.0% lidocaine group and 75% of those in the 0.5% lidocaine group (P > 0.05). The duration of postoperative analgesia was similar in all groups. Serum lidocaine concentrations before and 15, 30, 60, and 120 min after instillation of lidocaine were highest in the 1.5% lidocaine group with a peak concentration of 278 ng/mL. No patient had symptoms of lidocaine toxicity. We recommend that lidocaine concentrations of 1.0% or 1.5% be used when 20 mL is instilled intraarticularly for knee arthroscopy based on patient comfort and absence of lidocaine toxicity.

Evaluation of a new blood-conserving arterial line system for patients in intensive care units

ObjectiveTo evaluate blood samples obtained from a new blood-conserving arterial line system for the presence of hemodilution or heparin contamination. DesignProspective, clinical trial. SettingA coronary intensive care unit in a tertiary-care teaching hospital. PatientsCardiovascular patients in whom invasive arterial blood pressure monitoring was indicated. InterventionsPaired blood samples were obtained from a conventional arterial line system and a new blood-conserving arterial line system for the measurement of hematocrit and partial thromboplastin time, and compared to evaluate for the presence of either hemodilution or heparin contamination. Measurements and Main ResultsA Bland-Altman bias analysis of the variability between the two blood draw methods was performed. The analysis indicated that a) a randomly determined partial thromboplastin time obtained from the blood-conserving arterial line would lie between 3.32 and −5.11 of the partial thromboplastin time taken from the conventional arterial line value with 95% confidence; and b) a randomly determined hematocrit obtained from the blood-conserving arterial line would lie between 1.97 and −1.85 of the hematocrit taken from the conventional arterial line value with 95% confidence. ConclusionsWe conclude that a) blood samples obtained with the blood-conserving arterial line demonstrate no evidence of hemodilution or heparin contamination; b) the blood-conserving arterial line provides blood samples without the need for an initial volume of blood to be discarded; c) the blood-conserving arterial line provides a means for blood conservation in the intensive care setting. (Crit Care Med 1993; 21:507–511)

A Comparison of Fentanyl-O2 and Sufentanil-O2 for Cardiac Anesthesia

In a prospective randomized study of 48 patients scheduled to undergo elective coronary artery surgery, sufentanil (20 μg/kg) was compared with fentanyl (100 μg/kg) anesthesia by assessing hemodynamic and plasma catecholamine level responses to surgery. At 15 points during the study, cardiovascular dynamics were recorded. At six points in the study, arterial blood was obtained for simultaneous assays of plasma concentrations of epinephrine, norepinephrine, and dopamine. Neither mean cardiovascular dynamics nor catecholamine concentrations were statistically significantly different between the groups preoperatively. Both agents provided generally stable hemodynamics during surgery. Sufentanil was associated with decreased systemic vascular resistance at several time points with concurrent increased cardiac index and heart rate. Although catecholamine levels increased somewhat during cardiopulmonary bypass in both groups, there were no significant differences between the groups at any point except that at chest closure patients given sufentanil had significantly lower dopatnine concentrations than those given fentanyl. Times for recovery from surgery failed to show any difference between the two groups of patients. Blood pressure increases with patients given sufentanil compared favorably with those given fentanyl. We conclude that at these doses, with this surgery, there were no major clinical differences, though sufentanil produced significantly lower systemic vascular resistance at several events and had a lower plasma dopamine concentration after cardiopulmonary bypass.

Esmolol reduces autonomic hypersensitivity and length of seizures induced by electroconvulsive therapy

We evaluated the clinical effectiveness of esmolol, an ultra-short-acting, β1-adrenergic receptor blocking drug, to control the sinus tachycardia and increase in arterial blood pressures induced by electroconvulsive therapy (ECT). Each of 20 patients, ASA physical status I-III, participated in a double-blind, randomized study involving four match-pair trials (placebo versus esmolol) during ECT. Each patient acted as his or her own control (total number of ECT procedures, 160). We administered a 4-min infusion of either placebo or esmolol at the rate of 500 μg · kg−1 · min−1. We then induced anesthesia with methohexital and succinylcholine. After administration of electrical stimulation for ECT, the rate of infusion decreased to 300 μg · kg−1 · min−1 for three additional minutes and was then discontinued. Statistically significant reductions in mean heart rate from minute 2 until minute 15 and in maximum heart rate (the mean of each patients maximum heart rate after seizure changed from 152 ± 23 to 115 ± 24 beats/min) occurred in patients given esmolol. During and immediately after infusion, arterial blood pressure also decreased. Finally, the length of seizures decreased, as manifested clinically from 48 ± 18 to 39 ± 14 s and on electroencephalogram from 86 ± 41 to 67 ± 28 s. We conclude that esmolol effectively controls the hyperdynamic response to ECT and reduces the length of seizures. The significance of the latter to the overall effectiveness of ECT is not known.

An evaluation of a new two-electrode myocardial electrical impedance monitor for detecting myocardial ischemia.

The objective of this study was to determine the efficacy of a two-electrode myocardial electrical impedance (MEI) monitor in reproducibly detecting induced myocardial ischemia by comparing MEI changes with hemodynamic changes, including sonomicrometric changes. With institutional approval, 80 dogs were anesthetized with sodium thiamylal, intubated, ventilated, and had venous, arterial, and pulmonary artery catheters placed. Medial sternotomy was performed to facilitate myocardial exposure and allow the left anterior descending coronary artery (LAD) to be isolated. Two pacing electrodes were attached to the myocardium to measure MEI with a monitor. Seventy dogs were randomly assigned to the 15, 30, 45, 60, or 120 min LAD occlusion group. Sonomicrometric transducers were attached to the myocardium of the ten remaining dogs and their LAD was occluded for 36 min. MEI increased immediately after LAD occlusion to a level significantly more (P <0.05) than baseline and returned to the baseline level upon reperfusion. Twenty dogs developed ventricular fibrillation with no attempts at resuscitation. MEI changes paralleled the sonomicrometric changes expected with ischemia. No significant cardiovascular hemodynamic changes were found with less than 45 min of LAD occlusion. Sixty and 120 min LAD occlusion resulted in significant decreases in cardiac output. The results of these experiments demonstrate that the two-electrode MEI monitor reproducibly changes in response to myocardial ischemia. Implications We used dogs to determine if we could measure myocardial ischemia using a device that measures impedance and demonstrated that a two-electrode myocardial electrical impedance monitor reliably reflected changes induced by myocardial ischemia.

Effect of oral clonidine premedication on anesthetic requirement, hormonal response, hemodynamics, and recovery in coronary artery bypass graft surgery patients

STUDY OBJECTIVE To examine how premedication with clonidine affects opioid use, hemodynamic effects, hormonal responses, and recovery effects. DESIGN Double blind, placebo-controlled study. SETTING Operating room and surgical intensive care unit of a university medical center. PATIENTS 54 patients undergoing elective coronary artery bypass graft (CABG) surgery. INTERVENTIONS Patients received approximately 5 micrograms/kg of oral clonidine or a placebo together with 40 micrograms/kg lorazepam 90 minutes prior to titrated sufentanil induction of anesthesia. Thirty minutes prior to cardiopulmonary bypass, a second dose of either approximately 5 micrograms/kg clonidine or placebo was given as a slurry via a nasogastric tube. MEASUREMENTS AND MAIN RESULTS Opioid use, hemodynamic effects, hormonal responses, and recovery effects were recorded. Values for ten hemodynamic variables were compiled on the evening prior to surgery, prior to induction, and during seven additional events and compared. Catecholamines and beta-endorphins were measured prior to induction, after intubation, and after sternotomy. The amount of sufentanil used for induction, maintenance, and total opioid were compared. The times to awakening and response to verbal commands were compared. The two groups exhibited similar patient demographics, cardiopulmonary bypass time, and duration of surgery. Patients receiving clonidine required significantly (p < 0.04) less sufentanil for induction (clonidine: 2.19 +/- 0.95 micrograms/kg vs. placebo: 2.93 +/- 1.07 micrograms/kg) and total amount of sufentanil (clonidine: 9.1 +/- 3.9 micrograms/kg vs. placebo: 11.7 +/- 4.6 micrograms/kg). Patients receiving clonidine required significantly (p < 0.01) less isoflurane (9.7 +/- 6.8 MAC min vs. 19.7 +/- 9.9 MAC min) to maintain heart rate (HR) and mean arterial pressure (MAP) to within 15% of baseline without significant differences in other vasoactive drugs. Catecholamine concentrations were significantly (p < 0.02) lower in patients receiving clonidine without any difference in beta-endorphin concentrations. Patients receiving clonidine had significantly (p < 0.02) lower HR, systolic arterial pressure, MAP, and systemic vascular resistance prior to induction than patients receiving placebo without differences in other hemodynamic variables. CONCLUSION Clonidine decreases opioid use and lowers hormonal response while maintaining stable hemodynamics in patients undergoing CABG with sufentanil anesthesia.

Defining the dose range for esmolol used in electroconvulsive therapy hemodynamic attenuation.

We evaluated the clinical effectiveness of esmolol, an ultra-short-acting, β-adrenergic receptor blocking drug, to control the sinus tachycardia and increase in arterial blood pressure induced by electroconvulsive therapy (ECT). Each of 20 patients, ASA physical status IIII, participated in a double-blind, randomized Latin-Square study involving two matched-pair trials (placebo versus esmolol given as a 500-μg/kg bolus followed by either 300 μg-kg-1-min-1 [high dose], 200 μg-kg_1-min_1 [medium dose], or 100 μg-kg_1-min_1 [low dose] infusion of esmolol) during ECT. Each patient acted as his or her own control (total number of ECT procedures were 160). We administered a 1-min bolus of placebo (normal saline) or esmolol at the rate of 500 μg-kg_1-min_1 followed by either high-, medium-, or low-dose esmolol or placebo for an additional 3 min. We then induced anesthesia with methohexital (1 mg/kg) and succinylcholine (0.5 mg/kg) IV. Ninety seconds after the administration of succinylcholine, the electrical stimulus was applied to induce seizure. The infusion of placebo or esmolol was discontinued 3 min after the electrical stimulus. Significant decreases were found in mean heart rate from minute 3 until minute 7 and in the maximum heart rate. The mean of each patients maximum heart rate after seizure changed from 147 ± 18 bpm in placebo patients to 112 ± 20 bpm in high-dose esmolol patients; to 121 ± 23 bpm in medium-dose esmolol patients; and to 124 ± 20 bpm in low-dose esmolol patients. Mean arterial blood pressure was significantly lower in the high-dose esmolol patients (100 ± 18 mm Hg) compared with the same patients given placebo (122 ± 25 mm Hg). Finally, the side effect of clinically determined length of seizures decreased in the high- (36 ± 14 s) and medium-dose (34 ± 14 s) esmolol patients as compared with placebo (42 ± 11 s) patients. Low-dose esmolol did not significantly reduce the clinically determined length of seizure (38 ± 11 s). We conclude that the 100-μg-kg-1-min-1 infusion following a 500-μg/kg bolus of esmolol effectively controls the hyperdynamic response to ECT.

The carbon dioxide rate of rise in awake apneic humans

Currently available estimates of the PaCO2 rate of rise in resting humans with resting lung volume were gathered during general anesthesia. The PaCO2 rate of rise during apnea in awake subjects was determined to acquire a value that may be more applicable to awake, ventilator-dependent, critically ill patients. Clinically, apnea occurs at functional residual capacity. With FiO2 = 1.0, 20 volunteers held their breaths at functional residual capacity for 0, 10, and 20 seconds, and then for as long as possible. They exhaled through an infrared CO2 analyzer after each interval to determine end-tidal pCO2. An estimate of the logarithmic PaCO2 rise during breath holding at functional residual capacity was 7 mmHg during the first 10 seconds (43 mmHg/minute), 2 mmHg during the next 10 seconds (13 mmHg/minute), and 6 mmHg/minute thereafter. In conclusion, PaCO2 increases more rapidly in awake apneic humans than earlier thought. The values reported herein probably are better for estimating duration of apnea in conscious, critically ill patients than are values obtained during general anesthesia.

Postoperative course after sufentanil or fentanyl anesthesia for coronary artery surgery

Postoperative hemodynamic effects were compared in 50 patients randomly selected to receive either sufentanil, 25 micrograms/kg, or fentanyl, 100 micrograms/kg, anesthesia for coronary artery bypass grafting. The two groups exhibited similar patient demographics; dose of premedicants and muscle relaxants; and use of inhalation agents. Values for 15 hemodynamic variables were recorded at baseline and at six postoperative times. The times to awakening, response to verbal commands, and extubation were also noted. Patients who received sufentanil had a more stable course, with higher cardiac outputs, lower systemic vascular resistances, and a lower incidence of hypertension. Postoperatively, the two groups had similar values for time to awakening, response to verbal commands, and extubation. Elimination half-lives differed significantly: 554 +/- 91 minutes (fentanyl) versus 277 +/- 60 minutes (sufentanil). Serum concentrations of both decreased linearly. The added advantages of postoperative hemodynamic stability could be important in the choice of anesthetic.