A novel supraclavicular approach to brachial plexus block.

We describe a novel supraclavicular approach to the brachial plexus. Designated as the intersternocleidomastoid technique, this new approach was tested in unembalmed cadavers. It was then applied for evaluation to 150 ASA grade I or II patients scheduled for elective surgery or physiotherapy of the upper limb or for treatment of reflex sympathetic dystrophy associated with painful shoulder. The new approach was easy to master because of a very simple surface landmark, i.e., the triangle formed by the sternocleidomastoid heads, which were visible and palpable in most patients studied (90%). The procedure was effective intraoperatively, providing satisfactory anesthesia in 140 patients (93%), partially satisfactory blocks in 6 (4%), and unsatisfactory blocks in only 4 (3%). The catheter entry point is cephalad enough not to obscure the surgical field on the shoulder. Catheter insertion was successful in 63 of 70 patients. Postoperative analgesia was provided for 48 h or more in 45 patients and for 24 h in 18 patients. Only minor complications were observed: asymptomatic phrenic nerve block in 89 patients (60%), transient Horner's syndrome in 15 (10%), transient recurrent laryngeal nerve blockade in 2, and misplacement of the catheter into the subclavian vein in 1 patient. No pneumothorax was observed.

A new axillary approach for continuous brachial plexus block. A clinical and anatomic study.

Catheter insertion in the neurovascular space by axillary approach allows a continuous brachial plexus block and/or postoperative analgesia. We developed a perivenous technique whereby the approach to the neurovascular sheath is guided under fluoroscopy by a preopacified axillary vein. A randomized study compared this technique to the technique of Selander in ASA grade I-II patients scheduled for surgery or painful physiotherapy of the hand. The study was performed in 36 patients randomly divided into two groups. In Group 1 (n = 18), the catheter was placed according to the technique described by Selander. In Group 2 (n = 18), the catheter was placed using our perivenous technique. A complete block was obtained in all the patients of Group 2 vs only 50% of the patients in Group 1 (P < 0.05). In Group 1 a partial block was observed in 17%, with failure in 33% of the patients. There was no difference in the two groups regarding the time required to perform either technique, the duration of the complete block, the pain score, or the amount of continuously administrated bupivacaine during the first 48 h postoperatively. The plasma concentrations of total bupivacaine (high-performance liquid chromatography) were low in successful blocks, with no differences in the two groups; the median value was 0.68 microgram/mL (95% confidence interval: 0.62-0.89). The concentrations were higher (P < 0.01) in failed blocks; the median value was 1.69 micrograms/mL (95% confidence interval: 0.58-2.8). A complementary anatomic study of three arms from fresh cadavers allowed verification of the correct localization of the Teflon cannula and flexible catheter, as well as homogeneous diffusion of the methylene blue inside the brachial plexus. The perivenous technique for continuous axillary brachial plexus block may improve the success rate due to its radiologic and accurate location of the neurovascular sheath.

Effects of oral clonidine premedication and postoperative i.v. infusion on haemodynamic and adrenergic responses during recovery from anaesthesia.

The effects of clonidine, a central alpha 2-adrenoreceptor agonist, on haemodynamic and catecholamine changes were assessed during emergence from anaesthesia, a period which is associated with increased sympathetic nervous discharge, hypertension and tachycardia. According to a double-blind randomized design, 32 patients received either clonidine, preoperatively given by oral route (3.5 micrograms.kg-1) and postoperatively by i.v. infusion (0.3 microgram.kg-1.h-1), or a placebo. Perioperative management was similar in both groups. Measurements were made in the recovery room, before starting clonidine or placebo infusions for evaluation of clonidine premedication, and then during infusion as follows: when core temperature reached 37 degrees C; then 2 h, and 6 h later. Prior to starting infusions, mean blood pressure (88 +/- 15 vs 103 +/- 14 mmHg) (11.7 +/- 2.0 vs 13.7 +/- 1.9 kPa), heart rate (67 +/- 8 vs 87 +/- 17 beats.min-1) and plasma norepinephrine levels (462 +/- 393 vs 615 +/- 361 pg.ml-1) were lower in the clonidine group. Only at the latest measurement (6 h after core temperature reached 37 degrees C) did clonidine elicit significant effects. The values during clonidine infusion compared to placebo were at this time: mean blood pressure (73 +/- 10 vs 86 +/- 13 mmHg) (9.7 +/- 1.3 vs 11.5 +/- 1.7 kPa), heart rate (71 +/- 6 vs 93 +/- 13 beats.min-1) and plasma norepinephrine levels (240 +/- 224 vs 451 +/- 111 pg.ml-1). Our results suggest that: 1) preoperative clonidine may improve the haemodynamic profile associated with anaesthetic discontinuation, but 2) i.v. infusion (0.3 microgram.kg-1.h-1) did not prolong this effect during the early postoperative period in the face of the sympathetic nervous discharge of recovery.

Additive effects of dihydralazine during enflurane or isoflurane hypotensive anaesthesia for spinal fusion.

Sixteen patients (13-38 yr) undergoing spinal fusion for scoliosis under controlled hypotension were studied to determine the haemodynamic and neuroendocrine responses to IV dihydralazine (1.0 mg.kg-1) followed by 0.5 and 1 MAC of enflurane or isoflurane. Twenty minutes after dihydralazine administration mean arterial pressure (-20 per cent) and systemic vascular resistance (-50 per cent) decreased, and cardiac index (+57 per cent), heart rate (+37 per cent) and intrapulmonary shunt increased. Plasma renin activity and aldosterone and norepinephrine levels increased. Further decreases in mean arterial pressure and in systemic vascular resistance were observed when 0.5 MAC enflurane or isoflurane were added. With 1 MAC anaesthetic levels a further decrease in mean arterial pressure was observed in both groups, but pressure fell to a lower level with isoflurane than with enflurane (p less than 0.01). The reduction of arterial blood pressure to a level of 50-60 mmHg for three to four hours was easy to control and was free of complications. The preliminary IV administration of dihydralazine allowed a reduced volatile agent concentration which attenuated undesirable haemodynamic effects, in spite of renin and norepinephrine release, and permitted a rapid intraoperative awakening.

Effects of systemic morphine and epidural bupivacaine on postoperative oxygen consumption during rewarming.

The alterations in hemodynamics and oxygen consumption as a consequence of continuous epidural infusions of bupivacaine at room temperature and conventionally administered morphine were studied during recovery from general anesthesia for total hip replacement. Twenty-four patients were randomized to receive either bupivacaine or morphine in the recovery room. The bupivacaine group received from 6 to 12 ml per hour of 0.25% bupivacaine epidurally. Patients in the morphine group received 0.1 mg/kg of morphine intramuscularly no more frequently than every 4 hours. A pulmonary artery flotation catheter was inserted into each patient to determine hemodynamics and oxygen consumption at three instances: before analgesia, when pulmonary artery blood temperature reached 36 degrees C, and when it reached 37 degrees C. During the rewarming there was a decrease in mean arterial blood pressure and the systemic vascular resistance index and an increase in heart rate. The whole body oxygen consumption index increased in the bupivacaine group at the last measuring point but was stable in the morphine group. There was no effect on the arterial-venous oxygen content difference in either group. At 37 degrees C, the cardiac index and oxygen consumption index were significantly higher in the bupivacaine group than in the morphine group. In contrast to regional analgesia, systemic morphine administration can partially antagonize cardiovascular response to postoperative rewarming because it induces a stable oxygen demand.

Hemodynamic effects of continuous norepinephrine infusion in dogs with and without hyperkinetic endotoxic shock.

We compared, at constant preload maintained by polygeline (gelatin) infusion, the hemodynamic effects of continuous infusion of norepinephrine (0.5, 1, and 1.5 micrograms/kg X min) in anesthetized dogs with and without hyperdynamic endotoxic shock. In both groups, norepinephrine infusion increased systolic, diastolic and mean aortic BP, cardiac index, stroke index, index of myocardial contractility, and mean pulmonary artery pressure. No significant change in right atrial pressure, left ventricular end-diastolic pressure, heart rate, systemic vascular resistance, or pulmonary vascular resistance was observed. Oxygen consumption index and oxygen extraction ratio remained unchanged. Increases in systolic aortic BP were dose-related, whereas maximal effects on other variables were obtained at 0.5 to 1 microgram/kg X min. The rise in aortic pressure resulted from an increased cardiac index but not from an increased systemic vascular resistance. Stroke index increased as contractility improved. The slight alpha-adrenergic effect of continuous, low-dose norepinephrine infusion did not impede the beneficial effects of the marked beta-adrenergic stimulation on cardiac function. The combination of these two effects improved hemodynamic disturbances of hyperdynamic endotoxic canine shock.

Air entrainment during high-frequency jet-ventilation. Simulation of a bronchoscopy with a lung model.

Air entrainment contribution to jet-ventilation during bronchoscopy was evaluated as a lung model (increasing compliance and airway resistance). Ventilation was provided through a 10 mm internal diameter tube using either jet alone without air entrainment, or injection with air entrainment (coaxial and lateral injectors). Three I/E ratios (0.25, 0.43 and 0.67) and nine rates of ventilation, ranging from 20 to 300 c X min-1, were assessed. The driving pressure of the injected air was 350 +/- 10 kPa. Air entrainment is an important part of total ventilation (63.7 +/- 5.5%). The magnitude of air entrainment depends upon the levels of peak and end expiratory airway pressures. Increase in lung volume varies linearly with the end expiratory pressure. Air entrainment contributes to keep the tidal volume above the model dead-space. CO2 elimination is related to the magnitude of ventilated volumes. The amount of entrained air interferes with the FIO2 of delivered gases. During bronchoscopy, lateral injection should be preferred because of smaller airway pressures (- 31.2 +/- 0.6%) and lung volumes, while tidal volumes remain adequate.

What changes can be expected during high frequency jet ventilation when the rate of ventilation, the I:E ratio and the driving pressure are modified? A laboratory study.

Changes in minute ventilation, tracheal airway pressure and lung volume have been measured using a jet ventilator (VS 600) during different rates of ventilation, I:E ratios and driving pressures. A lung model with a slightly increased compliance and an increased airway resistance was used. Five rates of ventilation (from 60 to 230 b.p.m.), three I:E ratios (0.25, 0.43, 0.67) and three driving pressures (200, 300 and 400 kPa) were studied. The increases in the rate of ventilation did not modify minute ventilation significantly, decreased peak airway pressure only slightly and increased end-expiratory pressure and lung volume. The increases in I:E ratio produced increases in minute ventilation, peak airway pressure, end-expiratory pressure and lung volume. The increases in driving pressure induced changes similar to those produced by the alterations in I:E ratio.

[Hemodynamic effects of flunitrazepam in coronary patients. Postoperative study immediately after digestive tract and orthopedic surgery]. / Effets hémodynamiques du flunitrazépam chez le coronarien. Etude en période postopératoire immédiate après chirurgie digestive et orthopédique.

The present study was designed to evaluate the haemodynamic effects of flunitrazepam used for sedation in the post operative period after abdominal or orthopedic surgery. Patients with coronary artery disease (C.A.D.) were divided in two groups; in group II stable cardiac failure was present. Results did not show any significant haemodynamic changes after flunitrazepam in both groups. Flunitrazepam is a haemodynamic secure and valuable agent for sedation during recovery for patients with C.A.D. even in stable cardiac failure.

Jet ventilation using low or high frequencies, during bronchoscopy.

Jet ventilation, through a bronchoscope, was evaluated using a lung model (normal compliance and increased airway resistance). Three I/E ratios (0.25, 0.43, 0.67) and seven rates of ventilation (from 20 to 230 cycles per min (c min-1) were studied with the bronchoscope either unoccluded or partially occluded by a telescope. Increases in I/E ratio induced increases in minute ventilation, peak airway pressure, end-expiratory pressure and lung volume. Increase in the rate of ventilation decreased peak airway pressure, increased end-expiratory pressure and lung volume; minute ventilation increased in parallel with the increase in the rate of ventilation or remained constant when a high I/E ratio was used. The introduction of the telescope reduced minute ventilation, as a result of a decrease in the amount of air entrained, and increased end-expiratory pressure and lung volume. The risk of barotrauma as a result of high peak pressure is reduced during high frequency jet ventilation, but the increase in lung volume, particularly when the telescope is introduced, may be of clinical importance.

[Pneumomediastinum and subcutaneous emphysema after translaryngeal jet ventilation]. / Pneumomédiastin et emphysème sous-cutané au décours d'une ventilation translaryngée par oxygène pulsé.

The use of emergency transtracheal jet ventilation in a 62 year-old female with laryngeal papillomatosis and respiratory distress is reported. Adequate ventilation of the lungs with an intermittent jet of oxygen under high pressure (5 bar) allowed anaesthesia and surgery to be carried out. Pathogenesis of the mediastinal and subcutaneous emphysema discovered at the end of the procedure is discussed.