Extradural Anaesthesia Research Articles

MATERNAL AND FETAL HAEMODYNAMIC EFFECTS OF SPINAL AND EXTRADURAL ANAESTHESIA FOR ELECTIVE CAESAREAN SECTION

Serial haemodynamic investigations were performed in 32 women who were allocated randomly to receive either spinal or extradural anaesthesia for elective Caesarean section. Cardiac output was measured by Doppler and cross-sectional echocardiography at the aortic valve. Doppler flow velocity waveforms were recorded also from the umbilical artery. Preloading with Ringer lactate solution 1 litre increased cardiac output in both groups. After injection of bupivacaine, cardiac output remained increased in the extradural group, but decreased in the spinal group. This was associated with an increase in umbilical artery pulsatility index in the spinal group. Umbilical artery pH was less in the spinal group (7.22 vs 7.27), although no neonate was depressed at birth. The maximum percentage change in cardiac output and umbilical artery pulsatility index correlated with umbilical artery pH (r = 0.54, r = 0.72, respectively). There was no significant correlation with change in arterial pressure.

EFFECT OF ADRENALINE ON EXTRADURAL ANAESTHESIA, PLASMA LIGNOCAINE CONCENTRATIONS AND THE FETO-PLACENTAL UNIT DURING ELECTIVE CAESAREAN SECTION

Extradural anaesthesia was induced with either 2% lignocaine or 2% lignocaine with adrenaline 1:200,000 in 20 patients undergoing elective Caesarean section. With the adrenaline-containing solution, a smaller dose of lignocaine was required to produce an adequate block and the lignocaine concentrations in both mother and neonate were significantly smaller compared with the plain solution. Arterial pressures were less in the adrenaline group, but there was no difference in umbilical flow velocity waveform, fetal heart rate or fetal outcome. Neither feto-placental circulation nor fetal outcome were affected adversely by episodes of hypotension or the ephedrine used for treatment.

EFFECTS OF EXTRADURAL BUPIVACAINE WITH ADRENALINE FOR CAESAREAN SECTION ON UTEROPLACENTAL AND FETAL CIRCULATION

We have studied the effects of an extradural block using bupivacaine with adrenaline 90-100 micrograms on blood flow in the maternal uterine and placental arcuate arteries and the fetal umbilical, renal and middle cerebral arteries, using a colour Doppler technique in eight healthy parturients undergoing elective Caesarean section. Fetal myocardial function was investigated simultaneously by M-mode echocardiography. Maternal heart rate increased and diastolic arterial pressure decreased after extradural administration of bupivacaine with adrenaline. The latter effect was relieved by increasing the infusion rate in every case and none of the patients required vasopressors. There were no significant differences in maternal or fetal blood velocity waveforms, and no significant changes were found in any of the fetal myocardial measurements relative to control values. These observations suggest that extradural anaesthesia using bupivacaine with adrenaline does not have an adverse effect on vascular resistance in the uteroplacental or fetal circulations or on fetal myocardial function in normal pregnancy when bupivacaine-adrenaline is administered fractionally and maternal hypotension is prevented by rapid crystalloid volume loading.

EFFECT OF I.V. LOW-DOSE ADRENALINE AND PHENYLEPHRINE INFUSIONS ON PLASMA CONCENTRATIONS OF BUPIVACAINE AFTER LUMBAR EXTRADURAL ANAESTHESIA IN ELDERLY PATIENTS

Thirty patients undergoing primary total hip replacement under lumbar extradural anaesthesia with 0.75% bupivacaine 25 ml were allocated randomly to receive either low-dose adrenaline or phenylephrine infusions i.v. throughout surgery. Haemodynamic measurements and arterial blood samples were obtained before the extradural injection and at 10, 20, 30, 40, 50, 60 and 90 min thereafter. Peak arterial plasma concentrations of bupivacaine were observed 10 min after extradural anaesthesia and were significantly lower in patients receiving adrenaline infusions. Cardiac output was significantly greater in patients receiving adrenaline infusions (P less than 0.01). It is postulated that the smaller circulating concentrations of bupivacaine observed in patients receiving adrenaline were caused by increased cardiac output and a greater volume of distribution than in patients receiving phenylephrine.

EFFECTS OF EXTRADURAL ANAESTHESIA ON UMBILICAL AND UTEROPLACENTAL ARTERIAL FLOW VELOCITY WAVEFORMS

Flow velocity waveforms were recorded from the umbilical artery and uteroplacental arterial circulations of 15 women undergoing elective Caesarean section under extradural anaesthesia. The systolic: diastolic ratios of the flow velocity waveform were determined before and after extradural block. Extradural block did not alter fetal or maternal heart rates; however, umbilical artery systolic:diastolic ratio decreased from a mean (SD) of 2.4 (0.42) to 2.26 (0.38) (P = 0.049). There were no significant changes in the uteroplacental systolic:diastolic ratios. These results were compared with those from a control group in which no statistically significant changes in maternal and fetal systolic:diastolic ratios or heart rates were observed. The application of a pulse correction factor to standardize the data to fixed maternal and fetal heart rates had little effect on the significance of the findings. Extradural block in normal pregnant women during late gestation was associated with a small reduction in umbilical artery systolic:diastolic ratios, suggesting a decrease in downstream fetoplacental vascular resistance.

HAEMODYNAMIC EFFECTS AND OUTCOME ANALYSIS OF HYPOTENSIVE EXTRADURAL ANAESTHESIA IN CONTROLLED HYPERTENSIVE PATIENTS UNDERGOING TOTAL HIP ARTHROPLASTY

We have examined the safety of induced hypotension produced by extradural anaesthesia in patients with medically controlled hypertension. The haemodynamic response to induced hypotension was assessed in 38 non-hypertensive and 31 controlled hypertensive patients. All received extradural anaesthesia to T4 or above which decreased mean arterial pressure to 52 mm Hg and 55 mm Hg in normotensive and hypertensive patients, respectively. Cardiac output (thermodilution) was maintained by low dose i.v. infusions of adrenaline (1-5 micrograms min-1). No differences in the haemodynamic response to induced hypotension were observed in hypertensive patients. Data were collected also from 987 consecutive patients (353 hypertensive and 634 non-hypertensive) undergoing total hip replacement. Patients with hypertension were significantly older (68 vs 60 yr; P less than 0.001) and had greater ASA ratings (P less than 0.001). The smallest recorded systolic pressures were reduced more in patients with hypertension (57% vs 52%, respectively; P less than 0.001). The mean duration of maintained intraoperative hypotension (100 and 98 min) and estimated intraoperative blood loss (278 vs 281 ml) were similar in each group. After operation, two patients developed myocardial infarctions. None developed acute renal failure or stroke. There were three deaths; one of a patient who had hypertension. This suggests that induced hypotension with extradural anaesthesia is a safe technique for patients with medically controlled hypertension undergoing total hip arthroplasty.

ZONES OF DIFFERENTIAL SENSORY BLOCK DURING EXTRADURAL ANAESTHESIA

We have measured spinal segmental levels of anaesthesia to light touch (LT), pinprick (PP) and cold temperature discrimination (TE) during 2% lignocaine extradural anaesthesia in 22 patients, to determine if zones of differential sensory block develop during extradural anaesthesia and, if so, the extent to which TE extends beyond PP or LT levels and how age affects differential block. The median thoracic dermatomal levels were 4.5 for LT, 2.0 for PP and 2.0 for TE. Zones of differential sensory block developed within 5 min of extradural injection of local anaesthetic, and persisted for the next 55 min. In all instances, PP extended more cephalad than LT, and TE extended above PP levels. There were no differences in the extent of zones between the two groups of patients with mean ages of 28 and 48 yr. Thus, during extradural anaesthesia, sympathetic denervation extended one to two spinal segments above the sensory levels of LT and PP anaesthesia, age (28 vs 48 yr) affected neither the cephalad extent nor the width of zones of differential block, and PP levels of anaesthesia were closer to presumed levels of sympathetic block than were LT levels.

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AnaesthesiaVolume 46, Issue 6 p. 505-505 Free Access Reply A.W. Harrop-Griffiths, A.W. Harrop-Griffiths St. Mary's Hospital, London W2 1NY Edgware General Hospital, Edgware, MiddlesexSearch for more papers by this authorA. Ravalia, A. Ravalia St. Mary's Hospital, London W2 1NY Edgware General Hospital, Edgware, MiddlesexSearch for more papers by this authorD.A. Browne, D.A. Browne St. Mary's Hospital, London W2 1NY Edgware General Hospital, Edgware, MiddlesexSearch for more papers by this authorP.N. Robinson, P.N. Robinson St. Mary's Hospital, London W2 1NY Edgware General Hospital, Edgware, MiddlesexSearch for more papers by this author A.W. Harrop-Griffiths, A.W. Harrop-Griffiths St. Mary's Hospital, London W2 1NY Edgware General Hospital, Edgware, MiddlesexSearch for more papers by this authorA. Ravalia, A. Ravalia St. Mary's Hospital, London W2 1NY Edgware General Hospital, Edgware, MiddlesexSearch for more papers by this authorD.A. Browne, D.A. Browne St. Mary's Hospital, London W2 1NY Edgware General Hospital, Edgware, MiddlesexSearch for more papers by this authorP.N. Robinson, P.N. Robinson St. Mary's Hospital, London W2 1NY Edgware General Hospital, Edgware, MiddlesexSearch for more papers by this author First published: June 1991 https://doi.org/10.1111/j.1365-2044.1991.tb11702.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References 1 Gamil M. Serial peak expiratory flow rates in mothers during Caesarean section under extradural anaesthesia. British Journal of Anaesthesia 1989; 62: 415– 8. Volume46, Issue6June 1991Pages 505-505 ReferencesRelatedInformation

SENSITIVITY, SPECIFICITY AND PREDICTIVE VALUE OF THE SENSATION OF WARMTH AS A METHOD OF DETECTING INADVERTENT SUBARACHNOID INJECTION OF LOCAL ANAESTHETIC WHEN PERFORMING EXTRADURAL BLOCKS

In order to test if the rate of onset of sensation of warmth in the legs after the injection of 0.5% bupivacaine might discriminate between subarachnoid and extradural injection, 150 urological patients were allocated randomly to receive either spinal anaesthesia with isobaric (IS) or hyperbaric (HS) 0.5% bupivacaine, or extradural anaesthesia with isobaric 0.5% bupivacaine. The volume of the local anaesthetic for spinal anaesthesia and for the extradural test dose was 3-4 ml. The patients were asked to report at once if they had a sensation of warmth in the legs during or after injection of local anaesthetic. The mean time to the sensation of warmth was significantly shorter in the spinal groups (80 (SEM 10) s in IS and 76 (8.0) s in HS) than in the extradural group (558 (38) s). However, six patients in the IS and two in the HS group had no sensation of warmth.

UTEROPLACENTAL AND FETAL HAEMODYNAMICS DURING EXTRADURAL ANAESTHESIA FOR CAESAREAN SECTION

We have studied the effects of extradural anaesthesia with bupivacaine (plain) in eight healthy parturients undergoing elective Caesarean section, on blood flow in maternal uterine and placental arcuate arteries and in fetal umbilical, renal and middle cerebral arteries, using a colour Doppler technique. Simultaneously, fetal myocardial function was investigated by M-mode echocardiography. Maternal and fetal blood velocity waveform indices did not change significantly. We found no changes in fetal myocardial function with extradural anaesthesia, except for an increase in the right ventricular inner end-diastolic dimensions. These results suggest that extradural anaesthesia has no detrimental effects on uteroplacental and fetal circulations in the uncomplicated pregnancy when maternal hypotension is avoided with rapid prehydration.

COMPARISON OF FOUR SUBARACHNOID SOLUTIONS IN A NEEDLE-THROUGH-NEEDLE TECHNIQUE FOR ELECTIVE CAESAREAN SECTION

We have used both spinal and extradural anaesthesia with a 26-gauge, long spinal needle through a 16-gauge Tuohy needle for elective Caesarean section. Four different subarachnoid solutions of bupivacaine were compared: 0.5% heavy bupivacaine alone, or with adrenaline, fentanyl or adrenaline and fentanyl. The incidence of complications and time of regression of the sensory block were analysed. The technique is recommended because it allows rapid onset of anaesthesia and the advantages of an extradural catheter. The subarachnoid solution of choice was 0.5% heavy bupivacaine 12.5 mg with fentanyl 10 micrograms.

COMPARISON OF INCREMENTAL SPINAL ANAESTHESIA USING A 32-GAUGE CATHETER WITH EXTRADURAL ANAESTHESIA FOR ELECTIVE CAESAREAN SECTION

Forty-three mothers who had requested regional anaesthesia for elective Caesarean section were allocated randomly to receive either extradural anaesthesia with pH-adjusted 2% lignocaine with 1/200,000 adrenaline, or incremental spinal anaesthesia using a 32-gauge catheter with 0.5% plain bupivacaine. Increments of lignocaine or bupivacaine were given with the aim of achieving a block from T4 to S5. The spinal catheter was quicker to place (median 3 min, range 1-45 min, compared with median 10 min, range 1.5-50 min) and spinal anaesthesia was quicker to establish (median 20 min, range 10-46 min compared with median 48 min, range 15-59 min) compared with the extradural technique. The maximum height of the spinal block was significantly higher (median T3-4, range T5-T3) than the extradural group (median T5, range T6-T3). The total dose of intrathecal 0.5% bupivacaine was unpredictable, with a mean dose of 2.7 ml and a range between 1.5 ml and 7.4 ml. Haemodynamic stability and the quality of the block were similar between the groups. There were two mild spinal-headaches in the spinal group. All the spinal catheters were removed intact.

Extradurals and Shivering Effects of Cold and Warm Extradural Saline Injections in Volunteers

We tested the hypothesis that cooling the extradural space may provoke shivering, by giving three 80-ml extradural injections of warm (39.8±1.2°C) or cold (17±2.2°C) saline to four healthy volunteers, whilst recording central temperature and electromyographic activity from four muscles. The first injection (always cold) did not induce shivering in any of the subjects. The second and third injections, randomly cold or warm, were given after induction of shivering with cold blankets, but had no detectable effects on the intensity of shivering. This suggests that shivering in extradural anaesthesia does not result solely from cooling of the extradural space.

COMPARISON OF EXTRADURAL ROPIVACAINE AND BUPIVACAINE

Ropivacaine, a new long acting amide type local anaesthetic, was compared with bupivacaine in a randomized double-blind study. One hundred and ten patients undergoing extradural anaesthesia received a test dose of 3 ml of 1% lignocaine with adrenaline which was followed by 15 ml of one of five solutions: 0.5, 0.75 or 1.0% ropivacaine or 0.5 or 0.75% bupivacaine. There was little difference between the groups with respect to speed of onset or sensory block. The duration of analgesia was increased by increasing the concentration of both drugs, but this had minimal effect on onset time or extent of block. When the same concentration of each drug was administered, there were inconsistent differences in duration of sensory block, none of which was statistically significant. Increasing concentration of both drugs resulted in greater degree and longer duration of motor block. Ropivacaine produced a slower onset, shorter duration and less intense motor block than the same concentration of bupivacaine. The cardiovascular changes were similar in all groups.

COMPARISON OF RINGER'S ACETATE WITH 3% DEXTRAN 70 FOR VOLUME LOADING BEFORE EXTRADURAL CAESAREAN SECTION

We have studied haemodilution and cardiovascular responses to i.v. hydration with either 3% dextran 70 (Dx70) or Ringer's acetate using a non-invasive cardiac output monitor (BoMed NCCOM3-R7) in 40 healthy parturients undergoing Caesarean section under extradural anaesthesia. Haemodilution was more pronounced, and central venous pressure, mean arterial pressure and cardiac index maintained at greater values, after treatment with Dx70. Colloid osmotic pressures (COP) decreased by 1.7 mm Hg after loading with 3% Dx70, and by 5.6 mm Hg in mothers treated with Ringer's acetate (P less than 0.001). The transthoracic fluid index decreased more after hydration with Ringer's acetate (P less than 0.001), indicating an increase in lung water. In spite of these maternal changes, there were no differences in neonatal bioimpedance or values of haemoglobin, PCV, albumin and COP in umbilical cord blood, and only one case of respiratory distress. We conclude that colloids may be preferable to crystalloids for circulatory preload for extradural Caesarean section, as greater haemodynamic stability was maintained and increases in lung water avoided.

Effect of Adrenaline, Fentanyl and Warming of Inject ate on Shivering Following Extradural Analgesia in Labor

In order to assess factors which might clinically modify shivering associated with extradural anesthesia, 84 parturients were randomly divided into 4 groups. Group I received extradural block with 0.5% bupivacaine at room temperature. Group II received plain 0.5% bupivacaine warmed to 38.5–39°C. Group III received room temperature 0.5% bupivacaine with added 1:200,000 epinephrine. Group IV received room temperature 0.5% bupivacaine with 50 jug of fentanyl. The injectate volume was 10 ml in all patients. Data collected included demographics, cardiorespiratory parameters, pain and anxiety levels, labor ward ambient temperature, presence or absence of shivering before blockade, post block development of analgesia, presence of shivering, patient temperature and cardiovascular parameters.

EXTRADURAL ANAESTHESIA IN PATIENTS WITH PREVIOUS LUMBAR SPINE SURGERY

We studied prospectively 1381 patients undergoing extradural anaesthesia for total hip or total knee replacement, to determine if extradural anaesthesia can be performed reliably in patients who have had previous lumbar spine surgery. Fifty-two of the 57 patients (91.2%) who had undergone lumbar spine surgery received a successful extradural anaesthetic, and 1307 of 1324 patients without previous back surgery had successful extradural anaesthesia (98.7% success) (P less than 0.0001). No late complications were observed. Causes for failure of extradural anaesthesia in patients who had previously undergone lumbar spine surgery included technical difficulty (three) and inadequate spread (two).

Extradural Anaesthesia for Caesarean Section in Achondroplasia

We describe the successful management of a 26-yr-old achondroplastic dwarf undergoing elective Caesarean section under extradural anaesthesia. The patient had marked thoraco-lumbar kyphoscoliosis and clinical features which suggested that tracheal intubation would prove difficult. Block sufficient for surgery required only 5 ml of 0.5% bupivacaine and, apart from an initial unilateral block and mild intraoperative hypotension, her perioperative course was uneventful.

EXTRADURALS AND SHIVERING: EFFECTS OF COLD AND WARM EXTRADURAL SALINE INJECTIONS IN VOLUNTEERS

We tested the hypothesis that cooling the extradural space may provoke shivering, by giving three 80-ml extradural injections of warm (39.8 +/- 1.2 degrees C) or cold (17 +/- 2.2 degrees C) saline to four healthy volunteers, whilst recording central temperature and electromyographic activity from four muscles. The first injection (always cold) did not induce shivering in any of the subjects. The second and third injections, randomly cold or warm, were given after induction of shivering with cold blankets, but had no detectable effects on the intensity of shivering. This suggests that shivering in extradural anaesthesia does not result solely from cooling of the extradural space.

PREOPERATIVE SEDATION BEFORE REGIONAL ANAESTHESIA: COMPARISON BETWEEN ZOLPIDEM, MIDAZOLAM AND PLACEBO

The quality of premedication induced by oral midazolam and zolpidem, a new imidazopyridine hypnotic, was assessed in a controlled, double-blind study in 93 patients undergoing elective surgery under spinal or extradural anaesthesia. The patients were allocated randomly to three groups. Each group received the same treatment twice at two different doses. The night before operation, patients received zolpidem 10 mg, midazolam 7.5 mg or placebo and, 1 h before operation, zolpidem 20 mg, midazolam 15 mg or placebo. The sleep inducing effects of the drugs were comparable. Zolpidem and midazolam were significantly more effective sedatives than placebo 45 min after administration, but no difference was noted between the drugs. There was a comparable incidence of anterograde amnesia with zolpidem and midazolam, but the onset was shorter after zolpidem. Side effects were comparable in the three groups. Zolpidem is an effective hypnotic with a rapid onset and short duration of action which may be an alternative to midazolam for premedication.