Nikolaus Mayer

Ultrasonographic Guidance Improves Sensory Block and Onset Time of Three-in-One Blocks

The use of ultrasound reduces the onset time, improves the quality of sensory block, and minimizes the risks associated with the supraclavicular approach for brachial plexus and stellate ganglion blockade.The present study was designed to evaluate whether ultrasound also facilitates the approach for 3-in-1 blocks. Forty patients (ASA physical status II or III) undergoing hip surgery after trauma were randomly assigned to two groups. In the ultrasound (US) group, 20 mL bupivacaine 0.5% was administered under US guidance, whereas in the control group, the same amount and concentration of local anesthetic was administered with the assistance of a nerve stimulator (NS). After US- or NS-based identification of the femoral nerve, the local anesthetic solution was administered, and the distribution of the local anesthetic solution was visualized and recorded on videotape in the US group. The quality and the onset of the sensory block was assessed by using the pinprick test in the central sensory region of each of the three nerves and compared with the same stimulation on the contralateral leg every 10 min for 60 min. The rating was performed using a scale from 100% (uncompromised sensibility) to 0% (no sensory sensation). Heart rate, noninvasive blood pressure, and oxygen saturation were measured at short intervals for 60 min. The onset of sensory blockade was significantly shorter in Group US compared with Group NS (US 16 +/- 14 min, NS 27 +/- 16 min, P < 0.05). The quality of the sensory block after injection of the local anesthetic was also significantly better in Group US compared with Group NS (US 15% +/- 10% of initial value, NS 27% +/- 14% of initial value, P < 0.05). A good analgesic effect was achieved in 95% of the patients in the US group and in 85% of the patients in the NS group. In the US group, visualization of the cannula tip, the femoral nerve, the major vessels, and the local anesthetic spread was possible in 85% of patients. Incidental arterial puncture (n = 3) was observed only in the NS group. We conclude that an US-guided approach for 3-in-1 block reduces the onset time, improves the quality of the sensory block and minimizes the risks associated with this regional anesthetic technique. Implications: The onset time and the quality of a regional anesthetic technique for the lower extremity is improved by ultrasonographic nerve identification compared with older techniques. (Anesth Analg 1997;85:854-7)

Magnesium sulfate reduces intra- and postoperative analgesic requirements

In a randomized, double-blind study with two parallel groups, we assessed the analgesic effect of perioperative magnesium sulfate administration in 46 ASA physical status I or II patients undergoing arthroscopic knee surgery with total IV anesthesia. The patients received either magnesium sulfate 50 mg/kg preoperatively and 8 mg [center dot] kg-1 [center dot] h-1 intraoperatively or the same volume of isotonic sodium chloride solution IV. Anesthesia was performed with propofol (2 mg/kg for induction, 6-8 mg [center dot] kg- 1 [center dot] h- 1 for maintenance), fentanyl (3 [micro sign]g/kg for induction), and vecuronium (0.1 mg/kg for intubation). Intraoperative pain was defined as an increase of mean arterial blood pressure and heart rate of more than 20% from baseline values after the induction of anesthesia and was treated with bolus fentanyl (1-2 [micro sign]g/kg). Postoperative analgesia was achieved with fentanyl (0.5 [micro sign]g/kg) and evaluated using the pain visual analog scale for 4 h. During the intraoperative and postoperative periods, patients in the magnesium group required significantly less fentanyl than those in the control group (control group 0.089 +/- 0.02 [micro sign]g [center dot] kg-1 [center dot] min-1 versus magnesium group 0.058 +/- 0.01 [micro sign]g [center dot] kg-1 [center dot] min- 1; P < 0.05 and control group 0.021 +/- 0.013 [micro sign]g [center dot] kg-1 [center dot] min-1 and magnesium group 0.0031 +/- 0.0018 [micro sign]g [center dot] kg-1 [center dot] min-1; P < 0.01 for intraoperative and postoperative periods, respectively). We conclude that, in a clinical setting with almost identical levels of surgical stimulation, IV magnesium sulfate administration reduces intraoperative and postoperative analgesic requirements compared with isotonic sodium chloride solution administration. Implications: The perioperative administration of IV magnesium sulfate reduces intra- and postoperative analgesic requirements in patients with almost identical levels of surgical stimulus. Our results demonstrate that magnesium can be an adjuvant to perioperative analgesic management. (Anesth Analg 1998;87:206-10)

Hemodynamic and analgesic effects of clonidine added repetitively to continuous epidural and spinal blocks.

Clonidine in spinal and epidural blocks prolongs anesthesia, but can cause hypotension and bradycardia.The aim of our study was to compare hemodynamic and analgesic effects of spinal versus epidural clonidine alone and after repetitive dosing. In a prospective, randomized, double-blind study, we evaluated 40 patients scheduled for lower extremity orthopedic surgery under continuous spinal or epidural anesthesia with bupivacaine 0.5% (initial dose 5 mg and 50 mg, respectively). In either spinal or epidural technique one-half of patients received clonidine (150 micro gram) in addition to bupivacaine. Repeat doses of the same anesthetic mixture were allowed in cases of subsequent pain. Mean arterial pressure (MAP) and heart rate were recorded for 6 h after each injection. Duration of clinically useful anesthesia was defined as the time from drug administration to first sensation of pain. Intrathecal, but not epidural, clonidine decreased MAP significantly compared with bupivacaine alone. MAP after intrathecal clonidine with bupivacaine was lower than epidural clonidine with bupivacaine 5 and 6 h after injection. Repetitive administration caused no further decrease in MAP. Onset time required to surgical anesthesia (sensory block of T11) did not differ among the four groups. Duration of spinal and epidural anesthesia was increased more than two fold by clonidine. In summary, the addition of clonidine prolongs analgesia by either route. These results may be explained by clonidines sites of action in hemodynamic control and the density of bupivacaine-induced block. (Anesth Analg 1995;80:322-7)

Continuous Spinal Anesthesia with a Microcatheter and Low-Dose Bupivacaine Decreases the Hemodynamic Effects of Centroneuraxis Blocks in Elderly Patients

This prospective randomized study was designed to investigate the hemodynamic effects and quality of continuous spinal anesthesia (CSA) after rapid injection of a low dose of 0.5% bupivacaine through a 32-gauge microcatheter. The method was compared with continuous epidural (CEA) and single-dose spinal anesthesia (SSA). Seventy-seven elderly patients (ASA II-III) ranging from 57 to 94 yr old and undergoing lower limb surgery were assigned to CSA (n = 26), CEA (n = 26), and SSA groups (n = 25). In all three groups, mean arterial pressure (MAP) and heart rate (HR) were assessed continuously for 30 min after initial injection, as well as after every reinjection of local anesthetic in the CSA and CEA groups. Bupivacaine (0.5%) was used as a local anesthetic. The initial doses were 1 mL of CSA, 10 mL of CEA, and 3 mL of SSA. The reinjection doses were 1 mL of CSA and 5 mL of CEA. In the CSA group, MAP did not decrease, whereas in the CEA group, the maximum decrease was 15% +/- 3% (mean +/- SEM) for the initial injection, 12% +/- 2% for the first repetition, and 13% +/- 2% for the second repetition. In the SSA group, the largest decrease of MAP was 19% +/- 2%. All changes of MAP in the CEA and SSA groups were significantly larger compared with CSA group (P < 0.05). A total of seven patients in these two groups needed vasopressors due to a decrease of MAP of more than 30% from baseline values. Heart rate did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pentoxifylline on hemodynamics and oxygenation in septic and nonseptic patients

OBJECTIVE To evaluate the effects of pentoxifylline on hemodynamics and systemic oxygenation in septic and nonseptic critically ill patients. DESIGN Prospective clinical investigation. SETTING Intensive care unit (ICU) of a university hospital. PATIENTS Nineteen critically ill patients were included in the study 1 to 4 days after their admission to the ICU. A systemic inflammatory response syndrome was present in 12 patients, fulfilling at least two of the American College of Chest Physicians/ Society of Critical Care Medicine Consensus Conference criteria. The other seven patients did not fulfill these criteria and were classified as nonseptic. INTERVENTIONS All patients were mechanically ventilated. The dosage of catecholamines was kept constant during the entire study period and at least during 15 mins before the start of the study. In both study groups, pulmonary and radial artery catheters were inserted and 5 mg/kg of pentoxifylline (diluted in 300 mL of physiologic saline) was intravenously administered over a period of 180 mins at a rate of 100 mL/hr. MEASUREMENTS AND MAIN RESULTS Hemodynamic variables, oxygen transport (DO2), oxygen uptake (VO2), and oxygen extraction ratio were determined before pentoxifylline, after 2.5 mg/kg of pentoxifylline, after 5 mg/kg of pentoxifylline, and 60 mins after the termination of pentoxifylline. Repeated-measures analysis of variance and Mann-Whitney test were used for statistical analysis. At baseline, there were significant differences between the septic and the nonseptic groups in mean pulmonary arterial pressure (septic: 31 +/- 5 mm Hg; nonseptic: 26 +/- 7 mm Hg, p < .05), and pulmonary vascular resistance index (PVRI) (septic: 344 +/- 121 dyne.sec/ cm5.m2; nonseptic: 233 +/- 100 dyne.sec/cm5.m2, p < .05). In the septic group, significant increases in heart rate and cardiac index were observed. Systemic vascular resistance index and PVRI decreased. No significant changes in hemodynamic variables occurred in the nonseptic group. In both groups, DO2 and VO2 increased significantly, while oxygen extraction ratio remained unchanged. CONCLUSIONS The administration of pentoxifylline to septic patients results in a significant improvement in hemodynamic performance compared with critically ill nonseptic patients. The better hemodynamic state is accompanied by an increase in DO2 and VO2 with unchanged oxygen extraction ratio.

Resistive polymer versus forced-air warming: comparable heat transfer and core rewarming rates in volunteers.

BACKGROUND: Mild perioperative hypothermia increases the risk of several severe complications. Perioperative patient warming to preserve normothermia has thus become routine, with forced-air warming being used most often. In previous studies, various resistive warming systems have shown mixed results in comparison with forced-air. Recently, a polymer-based resistive patient warming system has been developed. We compared the efficacy of a standard forced-air warming system with the resistive polymer system in volunteers. METHODS: Eight healthy volunteers participated, each on two separate study days. Unanesthetized volunteers were cooled to a core temperature (tympanic membrane) of 34°C by application of forced-air at 10°C and a circulating-water mattress at 4°C. Meperidine and buspirone were administered to prevent shivering. In a randomly designated order, volunteers were then rewarmed (until their core temperatures reached 36°C) with one of the following active warming systems: (1) forced-air warming (Bair Hugger warming cover #300, blower #750, Arizant, Eden Prairie, MN); or (2) polymer fiber resistive warming (HotDog whole body blanket, HotDog standard controller, Augustine Biomedical, Eden Prairie, MN). The alternate system was used on the second study day. Metabolic heat production, cutaneous heat loss, and core temperature were measured. RESULTS: Metabolic heat production and cutaneous heat loss were similar with each system. After a 30-min delay, core temperature increased nearly linearly by 0.98 (95% confidence interval 0.91–1.04)°C/h with forced-air and by 0.92 (0.85–1.00)°C/h with resistive heating (P = 0.4). CONCLUSIONS: Heating efficacy and core rewarming rates were similar with full-body forced-air and full-body resistive polymer heating in healthy volunteers.

Three-in-one blocks with ropivacaine: evaluation of sensory onset time and quality of sensory block.

The purpose of this prospective, randomized, double-blinded study was to evaluate the sensory onset time and the quality of sensory block of ropivacaine, a new long-acting local anesthetic, compared with bupivacaine, for 3-in-1 blocks. Fifty ASA physical status I–III patients undergoing hip surgery after trauma were randomly assigned to two study groups of 25 patients each. The two study groups received a 3-in-1 block with either 20 mL of ropivacaine 0.5% or 20 mL of bupivacaine 0.5%. Blocks in both groups were performed using a nerve stimulator. The sensory onset time and the quality of sensory block was assessed by pinprick test in the central sensory region of each of the three nerves and compared with the same stimulation in the contralateral leg. We used a scale from 100% (normal sensation) to 0% (no sensory sensation). We did not find significant differences in sensory onset times between the ropivacaine group and the bupivacaine group (30 ± 11 vs 32 ± 10 min). The quality of sensory blocks was also comparable between the study groups (19% ± 20% vs 21% ± 15%). We conclude that the sensory onset time and quality of sensory block during 3-in-1 blocks performed with ropivacaine are comparable to those with bupivacaine. Ropivacaine is described as being less potent than bupivacaine, making this local anesthetic promising for 3-in-1 blocks because of its reportedly lower incidence of cardiovascular and central nervous system complications. Implications Ropivacaine 0.5% has a sensory onset time and quality of sensory block during 3-in-1 blocks similar to that of bupivacaine 0.5%. Ropivacaine is described as being less potent than bupivacaine, making it a promising local anesthetic for 3-in-1 blocks because of its reportedly lower cardiovascular and central nervous system toxicity.

Effects of propofol on the function of normal, collateral-dependent, and ischemic myocardium.

To examine the effects of propofol on the function of normal, collateral-dependent, and acutely ischemic myocardium, nine mongrel dogs were chronically instrumented with hydraulic occluders and ameroid constrictors were inserted around the left coronary artery, pressure transducers in the left ventricle, and heparin-filled catheters in the descending aorta and the left atrium. Regional function of normal, collateral-dependent, and acutely ischemic myocardium was assessed by sonomicrometry. Propofol (5 mg/kg intravenously) reduced function in normal myocardium (-15% ± 5%, 1 min and −14% ± 5%, 3 min after injection) and in collateral-dependent myocardium (-14% ± 5% and −13% ± 5%) to similar degrees, whereas ischemic myocardial function deteriorated significantly more (-25% ± 10% and −23% ± 10%, P < 0.01). Although left ventricular end-diastolic pressure remained unchanged and left ventricular contractility was reduced (-16% ± 4%, 1 min and −15% ± 3%, 3 min after propofol, P < 0.01), significant increases in heart rate (35% ± 7% and 26% ± 7%, P < 0.01) and decreases in coronary perfusion pressure (-14% ± 5%, P < 0.05 and −19% ± 6%, P < 0.01) occurred, likely affecting the function of ischemic myocardium. Thus, whereas collateral-dependent myocardium tolerated these adverse hemodynamic effects, ischemic myocardium responded with impairment of regional function that was significantly more pronounced than the impairment which occurred in normal or collateral-dependent areas after a 5 mg/kg intravenous bolus of propofol.

Pentoxifylline attenuates the increase in whole blood viscosity after transfusion

Background:  Pentoxifylline improves tissue oxygenation and intestinal blood flow in models of haemorrhagic shock, and it has been used for the treatment of intermittent claudication due to its beneficial effects on haemorheology. We investigated the effects of pentoxifylline on whole blood viscosity during packed red‐blood cell transfusion in critically ill adult patients.

In vivo modulation of human neutrophil function by pentoxifylline in patients with septic syndrome.

The influence of pentoxifylline on human polymorphonuclear granulocyte (PMN) respiratory burst activity (RBA) was studied in 23 patients fulfilling the established criteria of sepsis and in 10 healthy donors. Pentoxifylline (PTX) was administered (5 mg/kg) by intravenous infusion in 13 septic patients over a period of 180 min. The control group consisted of 10 patients with septic syndrome who received an infusion of physiological saline. For determination of RBA, 10 mL of blood was drawn at respective time intervals before, during, and after treatment with PTX or a placebo. RBA measurements were performed using a chemiluminescence assay after stimulation of PMN with formyl-methionyl-leucyl-phenylalanine (FMLP), phorbol-myristate-acetate, and opsonized zymosan, respectively. RBA measurements of each patient were performed in replicate samples. CL was measured for 1 h at respective time intervals (1, 3, 5, 8, 10, 15 min etc.). RBA of PMN of septic patients was compared with RBA of PMN of healthy donors and patients receiving PTX were compared with controls. Our results demonstrate that PMN of patients with sepsis had an increased oxidative response compared with healthy donors. We found that PTX administered intravenously was able to reduce this reactivity. RBA was significantly decreased during PTX infusion when PMN were stimulated with FMLP and phorbol-myristate-acetate, compared with the control group. No significant decrease was observed when PMN were stimulated with opsonized zymosan. These data suggest that PTX may be a valuable drug in septic state.