Incidence of bradycardia during recovery from spinal anaesthesia: influence of patient position.

We administered 0.5% plain bupivacaine 4 ml intrathecally (L2-3 or L3-4) in three groups of 20 patients, according to the position in which they were nursed in the post-anaesthesia care unit (PACU): supine horizontal, 30 degrees Trendelenburg or hammock position (trunk and legs 30 degrees elevated). Patients were observed until anaesthesia descended to less than S1. The incidence of severe bradycardia (heart rate < 50 beat min-1) in the PACU was significantly higher in patients in the Trendelenburg position (60%) than in the horizontal (20%, P < 0.01) or hammock (10%, P < 0.005) position. After 90 min, following admission to the PACU, only patients in the hammock position did not have severe bradycardia. In this late phase, the incidence of severe bradycardia in the Trendelenburg group was 35% (P < 0.005) and 10% in patients in the supine horizontal position. In four patients, severe bradycardia first occurred later than 90 min after admission to the PACU. The latest occurrence of severe bradycardia was recorded 320 min after admission to the PACU. We conclude that for recovery from spinal anaesthesia, the Trendelenburg position should not be used and the hammock position is preferred.

[30 degree trunk elevation of the patient and quality of lumbar epidural anesthesia. Effects of elevation in operations on the lower extremities]. / 30 grad Rumpfhochlagerung des Patienten und Qualität der lumbalen Epiduralanästhesie. Auswirkungen der Lagerung bei Operationen an der unteren Extremität.

The spread and intensity of lumbar epidural anaesthesia are unpredictable. Moreover, segments L5 and S1 are frequently missed. In this study the effect of 30 degrees trunk elevation on the spread and intensity of lumbar epidural sensory and motor blockade and on the cardiovascular system were studied. METHODS. After oral premedication with 7.5 mg midazolam, 30 patients 20 to 40 years of age, ASA 1-2, were randomly allocated to one of two groups according to their body position during injection of 20 ml 2% lidocaine (3 + 8 + 9 ml) into a lumbar epidural catheter (L2/3 or L3/4) and during the following 30 min: supine horizontal position or supine 30 degrees trunk elevation with 30 degrees leg elevation (hammock position). The patients received 500 ml Ringer solution before the epidural injection, followed by more Ringer solution. Systolic and diastolic blood pressures and heart rate were monitored noninvasively every 5 min; 30 min after the epidural injection the spread of analgesia (dullness of pinprick) and anaesthesia (no sensation of pinprick) as well as motor block according to Bromage were tested. A spread of anaesthetic segments including T12 to L3 was considered adequate for hip surgery, L3 to L5 for knee surgery, and L3 to S2 for foot surgery. Student's t-test, ANOVA, chi-square (Wilcoxon), and Mann-Whitney tests were used for statistical analysis. P < 0.05 was considered statistically significant. RESULTS. The median cephalad level of analgesia was lower in patients with the hammock position than those with the horizontal position (L1 vs T10; P < 0.05). There was no significant difference in the cranial level of anaesthesia (L2 vs L1) (Table 2). No significant difference was seen in the number of patients having adequate anaesthesia for hip surgery. Anaesthesia in the segments L5 and S1 was seen in 2/15 patients in the horizontal position and 8/15 patients in the hammock position (P < 0.05). The hammock position resulted in a higher percentage of patients having adequate anaesthesia for knee surgery (60% vs 13%; P < 0.05) and foot surgery (53% vs 13%; P < 0.05) (Table 3). Motor block was more profound in patients in the hammock position (Table 4). Blood pressure and heart rate did not change significantly in patients in the horizontal position (Fig. 1); there was a decrease in both systolic (7 mmHg) and diastolic (5 mmHg) blood pressures in patients in the hammock position. Heart rate did not change significantly (Fig. 2). No patient needed vasopressor support; the body position could be maintained in all patients during the observation period. One or two epidural reinjections according to the spread of anaesthesia 30 min after the first injection and to the scheduled operation resulted in adequate anaesthesia in every patient. DISCUSSION. More patients in the hammock position developed adequate anaesthesia in the relevant segments for knee and foot operations than patients in the horizontal position. These included the frequently missed segments L5 and S1. Patients in the hammock position had a clinically insignificant drop in systolic and diastolic blood pressure. In contrast to the young and healthy patients in this study, more severe cardiovascular changes might result in geriatric and/or ill patients subjected to a hammock position. For this reason, use of the technique in geriatric and/or ill patients requires special attention.

[The effect of central nervous modulation on the quality of epidural blockade.]. / Der Einfluß zentralnervöser Modulation auf die Qualität der Epiduralblockade.

Conventional clinical dosages of local anesthetics may not be sufficient to block conduction of all afferent impulses, which is important for an effective epidural sensory blockade. Further depression of the transmission of information can be accomplished by central modulating mechanisms, preventing sensory perception. Since there are interindividual differences in the quality of modulating mechanisms, standardized depression of impulse propagation by the local anesthetic is associated with a wide variation in the total depression of afferent impulses. For that reason, the results of a particular dosage of a local anesthetic will be variable regarding the amount of epidural sensory blockade perceived. A continuous epidural technique using a catheter permits the dosage to be individualized by means of additional injections. Patients with a low pain threshold require a more highly concentrated local anesthetic. The addition of opioids to the local anesthetic will permit the use of lower concentrations of the local anesthetic itself. Optimal use of diagnostic, prognostic, and therapeutic epidural blockades is possible only if the influence of modulating mechanisms is taken into account.

Pain threshold and subjectively perceived epidural sensory blockade with 0.5% bupivacaine.

We investigated the relationship between patients' pain thresholds and the quality of the subjectively perceived epidural sensory blockade (SPESB). The pain thresholds of 50 patients were evaluated with a modification of the submaximum effort tourniquet technique. There was a significant correlation between pain threshold and the number of subjectively perceived anesthetic and analgesic segments, the likelihood of developing an extensive SPESB being greater in patients with higher pain thresholds. Forty-one percent of patients with pain scores of less than 10 mm on the visual analogue scale, but no patient with a pain score of 20 mm or more, developed anesthesia in ten or more spinal segments.

[Comparative study of the effect of midazolam and hypnomidate on the cardiovascular system]. / Vergleichende Untersuchungen der Wirkung von Midazolam und Hypnomidate auf die Herz- und Kreislauffunktion.

A randomized study of the induction agents Midazolam and Hypnomidate on 20 patients without cardiovascular disease only showed a minimal effect of both agents on blood pressure, heart rate and myocardial function. Inspite of small differences after injection of Midazolam or Hypnomidate, neither of the agents appears superior to the other. Midazolam is an i.v. induction agent with minimal cardiovascular effect and good hypnotic properties.

Effects of pattern of ventilation on pulmonary metabolism and mechanics.

Effects of three patterns of mechanical ventilation on pulmonary mechanics, lung phospholipid and surface activity were studied in the normal closed-chest dog. The patterns were continuous mechanical ventilation with: 1) tidal volume (VT)=15 ml/kg; 2) VT=15 ml/kg with 10 cm H2O positive end-expiratory pressure (PEEP); 3) VT=50 ml/kg. THE DOGS IN EACH GROUP WERE VENTILATED FOR 24 HOURS, WITH CAREFUL ATTENTION PAID TO MAINTENANCE OF NORMAL BLOOD GASES, FLUID BALANCE, AND CARDIAC OUTPUT. The animals were sacrificed and the lungs studied to determine pressure-volume curves, dry lung weight/wet lung weight ratios, phospholpid contents and surface activities. The results were compared with control values in acutely sacrificed unventilated dogs. No significant change from controls was found with any pattern of ventilation employed with the exception of the tendency for lungs ventilated with PEEP to retain fluid (decreased dry lung weight/wet lung weight ratio).