Effect of posture on extradural pressure

Relationship of Abdominal Circumference and Trunk Length With Spinal Anesthesia Block Height in Geriatric Patients Undergoing Transurethral Resection of Prostate

INTRODUCTION

Spinal anesthesia is commonly used for various surgical procedures. Prediction of spinal anesthesia block height is always a challenging task for anesthetists. Higher than desired levels of spinal anesthesia blocks are associated with serious side effects, while inadequate block height does not provide satisfactory surgical anesthesia. In this study, we observed the relationship between the ratio of trunk length (TL) and square of the abdominal circumference (AC²) and spinal anesthesia sensory block height in geriatric patients undergoing transurethral resection of the prostate (TURP).

MATERIAL & METHODS

This is a cross-sectional study conducted at the Aga Khan University Hospital Karachi, Pakistan, on geriatric patients undergoing TURP under spinal anesthesia. Forty-three elderly patients (American Society of Anaesthesiology level I-III) between 60 and 80 years were recruited for the study. In hospital wards, trunk length (TL) and abdominal circumference were recorded before the procedure. In the operating rooms, spinal anesthesia was performed at L3-L4 intervertebral space with 0.5% hyperbaric bupivacaine 10mg (2mls). Block height was measured by the placement of ice pads at different dermatomes. Spearman rank correlation coefficient was used to analyze the physical parameters (TL/AC²) and spinal anesthesia block height.  Results: The ratio of trunk length and square of the abdominal circumference (TL/AC²) correlates with spinal anesthesia block height in geriatric patients, where the spearman rank correlation coefficient was r =-0.284 with p = 0.015.

CONCLUSION

The ratio of the long axis (TL) and transection area of the abdomen (AC²), which coincides with (TL/AC²), correlated with spinal anesthesia sensory block height. Hence, elderly patients with a low TL/AC² ratio will have higher block height after spinal anesthesia.

Randomized clinical trial of acetazolamide administration and/or prone positioning in mitigating wound complications following untethering surgeries

OBJECTIVE No evidence-based guideline has been approved for the postoperative management of pediatric patients with tethered cord syndrome (TCS). The purpose of this randomized clinical trial was to evaluate the effectiveness of prone positioning and acetazolamide administration on complication rates following spinal cord untethering surgeries. METHODS From October 2012 to February 2015, patients with a primary diagnosis of TCS who were admitted to the Children's Medical Center Hospital of Iran were randomly allocated to 1 of 4 intervention modality groups postoperatively: 1) Group A, acetazolamide administration for 10 days; 2) Group B, prone positioning for 10 days; 3) Group C, acetazolamide administration and prone positioning for 10 days; and 4) Group D, no intervention. CSF leakage, CSF collection, wound dehiscence, operative site infection, and secondary surgical wound repair were considered failure. RESULTS A total of 161 patients were enrolled in this study (Group A, n = 39 [24.2%]; Group B, n = 41 [25.5%]; Group C, n = 39 [24.2%]; and Group D, n = 42 [26.1%]). The overall failure rate was 12.42% (20 patients). Complication rates through pooled analyses were as follows: CSF leakage (n = 9, 5.6%), CSF collection (n = 12, 7.5%), wound dehiscence (n = 2, 1.2%), and infection of operation site (n = 3, 1.9%). Two patients (1.2%) required surgical secondary wound repair due to complications. CSF leakage and collection rates were significantly lower in patients who underwent prone positioning (p = 0.042 and 0.036, respectively). The administration of acetazolamide, either isolated or in combination with prone positioning, not only could not significantly lower the complication rates, but also added the burden of side effects. CONCLUSIONS The current study demonstrates the possible role of prone positioning in mitigating the complication rates subsequent to untethering surgeries. Clinical trial registration no.: NCT01867268 ( clinicaltrials.gov ).

Etiology and use of the "hanging drop" technique: a review

Background. The hanging drop (HD) technique presumably relies on the presence of subatmospheric epidural pressure. It is not clear whether this negative pressure is intrinsic or an artifact and how it is affected by body position. There are few data to indicate how often HD is currently being used. Methods. We identified studies that measured subatmospheric pressures and looked at the effect of the sitting position. We also looked at the technique used for cervical and thoracic epidural anesthesia in the last 10 years. Results. Intrinsic subatmospheric pressures were measured in the thoracic and cervical spine. Three trials studied the effect of body position, indicating a higher incidence of subatmospheric pressures when sitting. The results show lower epidural pressure (−10.7 mmHg) with the sitting position. 28.8% of trials of cervical and thoracic epidural anesthesia that documented the technique used, utilized the HD technique. When adjusting for possible bias, the rate of HD use can be as low as 11.7%. Conclusions. Intrinsic negative pressure might be present in the cervical and thoracic epidural space. This effect is more pronounced when sitting. This position might be preferable when using HD. Future studies are needed to compare it with the loss of resistance technique.

Full-term pregnant women have higher lumbar epidural pressure than non-pregnant women: a preliminary report

The objective of this study was to compare the lumbar epidural pressure of full-term pregnant women with that of non-pregnant women. The epidural pressure of 20 full-term pregnant women and 15 non-pregnant women was measured during epidural needle insertion in the lateral position (T0), and at 30-s intervals following insertion (T1-T3), after the patient was turned supine (T4-T6), and after local anaesthetic injection (T7-T9). Results showed that the average epidural pressures following epidural insertion in the lateral position (average of T1-T3), in the supine position (average of T4-T6), and after local anaesthetic injection (average of T7-T9) were all significantly higher in the pregnant women compared with those who were not pregnant (p= 0.0293, 0.0109 and 0.0309, respectively). Epidural pressures increased significantly after women were turned supine (p < 0.001). Average epidural pressures were positive for all time points, T0-T9. It was concluded that the epidural pressure in the pregnant women was higher than in those who were not pregnant, both in the lateral and the supine position.

Internal jugular vein compression to assess the correct placement of an epidural catheter in postpartum women

We investigated whether the increase in epidural pressure produced by jugular compression could be used as a test for correct placement of epidural catheters in 20 postpartum women who had good epidural analgesia during labour. We measured the epidural pressure by using the epidural catheter as a manometer, and measured the rise in the meniscus in response to jugular vein compression whilst the epidural catheter was still in the epidural space. The catheter was then withdrawn until the tip lay just outside the epidural space and the response to jugular vein compression reassessed. In all subjects, jugular vein compression produced a rise in the meniscus only whilst the catheter tip lay in the epidural space. Jugular compression is a useful test for confirming the correct placement of the epidural catheter.

The effect of body position on the ‘hanging drop’ method for identifying the extradural space in anaesthetized dogs

OBJECTIVES

To assess the accuracy of the 'hanging drop method' for identifying the extradural space in anaesthetized dogs positioned in sternal or lateral recumbency.

STUDY DESIGN

Prospective randomized-experimental study.

ANIMALS

Seventeen clinically healthy adult dogs, 10 females and seven males weighing 8.4-26.2 kg.

METHODS

Dogs were positioned in either sternal (n = 8) or lateral (n = 9) recumbency under general anaesthesia. A 20 SWG spinal needle pre-filled with 0.9% saline was advanced through the skin into the lumbosacral extradural space and the response of the saline drop recorded, i.e. whether it: 1) was aspirated from the hub into the needle; 2) remained within the hub, or 3) moved synchronously with i) spontaneous respiration, ii) heart beat or iii) manual lung inflation. The position of the needle tip was ultimately determined by positive contrast radiography.

RESULTS

One dog positioned in lateral recumbency was excluded from the study because bleeding occurred from the needle hub. Saline was aspirated into the needle in seven of eight dogs held in sternal recumbency but in none of the dogs positioned in lateral recumbency. Accurate needle tip placement in the extradural space was confirmed by positive contrast radiography in all dogs.

CONCLUSION AND CLINICAL RELEVANCE

The 'hanging drop' method, when performed with a spinal needle, appears to be a useful technique for identifying the location of the extradural space in anaesthetized medium-sized dogs positioned in sternal, but not in lateral recumbency. The technique may yield 'false negative' results when performed in dogs positioned in sternal recumbency.

Development of a neurosurgical operating table for adult cattle and changes in intracranial pressure and blood pressure in adult cattle undergoing long-time isoflurane anesthesia

We developed a neurosurgical operating table for restraining adult cattle in the sternal recumbent position during long-time inhalation anesthesia, and examined intracranial pressure (ICP), blood pressure and blood gases during isoflurane anesthesia. We confirmed that the maintenance of inhalation anesthesia, the restraint of cattle in the sternal recumbent position and bringing the cattle out of anesthesia could all be carried out safely using the operating table we produced. For the purposes of the present experiment, the cattle were divided into 2 groups: the SR group, which underwent sternal recumbency for 8 hr under isoflurane anesthesia using the neurosurgical operating table, and the RR group, which underwent right lateral recumbency for 3 hr under isoflurane anesthesia on a standard operating table. The mean ICP was found to be significantly lower in the SR group than in the RR group during anesthesia, and PaO2 was significantly higher in the SR group. In the SR group, no complications such as regurgitation or ruminal tympany occurred for 8 hr after the induction of anesthesia, and recovery from anesthesia was uneventful. In contrast, all RR cattle showed ruminal tympany and regurgitated ruminal fluid at 3 hr after the induction of anesthesia. Thus, the neurosurgical operating table developed in the present study may be useful for long-time anesthesia and neurosurgery of adult cattle.

Spinal CSF absorption in healthy individuals

The present study examines the extent of spinal cerebrospinal fluid (CSF) absorption in healthy individuals in relation to physical activity, CSF production, intracranial pressure (ICP), and spinal CSF movement. Thirty-four healthy individuals aged 21-35 yr were examined by lumbar puncture and radionuclide cisternography with repeated imaging. ICP was registered before and after CSF drainage, and CSF production was calculated. Spinal CSF absorption was calculated as reduction in spinal radionuclide activity. The radionuclide activity in the spinal subarachnoidal space was gradually decreased by 20 +/- 13% (mean +/- SD) during 1 h. The reduction was higher in active than in resting individuals (27 +/- 12% vs. 13 +/- 9%). The mean ICP in 19 of the individuals was 13.6 +/- 3.1 cm H(2)O. B-waves were found in 79% of the individuals, with a mean frequency of 0.6 +/- 0.3 min(-1). The mean CSF production rate was 0.34 +/- 0.13 ml/min. There were no correlations between radionuclide reduction, spinal movement of the radionuclide, and CSF production rate. The spinal radionuclide reduction found in this study indicates a spinal CSF absorption of 0.11-0.23 ml/min, more pronounced in active than in resting individuals.

Multivariate regression analysis of epidural pressure in cattle

OBJECTIVE

To evaluate the effects of growth, maturity, and pregnancy on epidural pressure in cattle.

ANIMALS

50 healthy Holstein cattle (18 heifers, 23 lactating cows, and 9 pregnant nonlactating cows).

PROCEDURE

Each of the cattle was restrained in a standing position. Height of the second lumbar vertebra's transverse process (2LTP) and humeral tuberosity (HT) on the right side as well as abdominal girth (AG) were measured in each animal, and body condition score (BCS) was ascertained. Skin caudal to the first lumbar spinous process was aseptically prepared, and anesthetic was injected. After inserting a 16-gauge 120-mm Tuohy needle in the ligamentum flavum, a calibrated pressure transducer was connected to the needle. Then, the needle was introduced into the epidural space, and epidural pressure was recorded.

RESULTS

Mean +/- SD residual epidural pressure of heifers (-9.3+/-3.3 mm Hg) was significantly higher than that of lactating (-174+/-5.5 mm Hg) or nonlactating (-14.5+/-2.4 mm Hg) cows. Stepwise regression of 5 variables revealed that only the difference in height between 2LTP and HT (2LTP - HT) in heifers and only BCS in lactating cows were significantly correlated with residual epidural pressure. For all cattle, the optimal equation (R2 = 0.47) describing the relationship was y = -12.7 + 6.3x, - 0.4x2 - 0.1x3, where y is epidural pressure, x1 is BCS, x2 is 2LTP - HT, and x3 is age.

CONCLUSIONS AND CLINICAL RELEVANCE

Negative epidural pressure was detected in standing cattle. Growth, maturity, and pregnancy affect epidural pressure in cattle.

Paravertebral venous plexus distention (Batson's): an inciting etiologic agent in lumbar radiculopathy as observed by venous angiography

Can the paravertebral plexus of veins adjacent to the spinal nerve root within the narrow confines of the lateral neural canal be a collateral generator of radicular pain when no other evidence of spinal pathology is evident? A patient with complaints of intractable lumbar radiculopathy and an otherwise unremarkable clinical neuromusculoskeletal examination, as well as normal imaging and electrodiagnostic studies, is reviewed with special reference to symptomatic and paravertebral venous responses to both a Valsalva maneuver and dipyridamole infusion as imaged by magnetic venous angiography.

A survey of epidural technique and accidental dural puncture rates among obstetric anaesthetists

Five hundred UK obstetric anaesthetists were surveyed to investigate retrospectively the relationship between experience, rotation of the epidural needle within the epidural space, choice of loss-of-resistance agent and accidental dural puncture (ADP) rate. Responses were received from 390 (78%) of the members surveyed. Anaesthetists with more than 15 years' experience are more likely to perform an epidural with the patient in the lateral position (P < 0.001), use loss-of-resistance to air to detect the epidural space (P < 0.001) and rotate the epidural needle after identifying the epidural space (P = 0.001) when compared to those of less experience. A reduced inadvertent dural puncture rate was found to be associated with increased frequency of performing the procedure (P = 0.012), greater experience of the practitioner (P = 0.049) and non-rotation of the epidural needle (P = 0.023). There are three components that can alter from case to case; patient positioning, loss-of-resistance agent and needle rotation. Loss-of-resistance agent and patient positioning in isolation did not significantly influence ADP rate. This study suggests that the combination of practising lateral patient positioning, loss-of-resistance to saline and non-rotation of the epidural needle significantly reduces ADP rate (P = 0.035).

The effect of increasing degrees of spinal flexion on cerebrospinal fluid pressure

The effects of increasing degrees of flexion on cerebrospinal fluid pressure were investigated in 12 neurosurgical patients requiring lumbar subarachnoid drains. Cerebrospinal fluid pressure and central venous pressure were measured in three positions: fully flexed ('chin on chest'), flexed at ninety degrees and straight. There was a significant increase in cerebrospinal fluid pressure on moving from the fully flexed to the flexed position (p < 0.0001), but not from the flexed to the straight position. These results were mirrored by smaller changes in central venous pressure. In patients without intracranial pathology these increases in cerebrospinal fluid pressure are probably unimportant. However, intracranial pathology may result in low cerebral perfusion pressures and any increase in cerebrospinal fluid pressure in this group may be harmful. The fully flexed position should be avoided when inserting lumbar drains in at risk patients.

Epidural pressure and postdural puncture headache in the parturient

Forty patients in whom the dura had been punctured accidentally and 10 patients who had received spinal anaesthesia required epidural blood patching for relief of severe postdural puncture headache (PDPH). Before injecting blood, the epidural pressure was measured, using an epidural catheter as a manometer. Mean epidural pressure in the left lateral position was 6.4 cm H(2)O (range 0.5-12 cm H(2)O). Epidural pressure was not related to the size of needle hole or prophylactic infusion of saline into the epidural space. In 5 patients with inadvertent dural tap, there was a statistically significant decrease (P<0.02) in epidural pressure from 14.9 cm H(2)O (range 11-22 cm H(2)O) before PDPH to 6.9 cm H(2)O (range 5-8.5 cm H(2)O) when they developed PDPH. The benefits of performing an epidural blood patch through a catheter placed in the epidural space are discussed.

Epidural pressure during infusion of saline in the parturient

Epidural pressure was measured in 17 post-partum patients who were receiving prophylactic infusion of saline into the epidural space after an inadvertent dural tap. During the infusion, the mean (+/-SD) epidural pressure was 19.1 (+/-4.3) cm H(2)O. Four patients complained of severe interscapular pain during the infusion. The epidural pressure in these patients was higher than 24 cm H(2)O. Prophylactic infusion of saline into the epidural space failed to prevent postdural puncture headache in 10 patients.

Severe headache following an epidural ‘top-up’

Half an hour after a normal delivery under epidural analgesia, a patient was given a top-up of 10 ml 0.25% bupivacaine for suture of a small vaginal tear. The patient developed severe headache, nausea and vomiting immediately after the top-up. Initially these symptoms were attributed to a complication of epidural analgesia. However, a raised epidural pressure led to a diagnosis of hypertensive encephalopathy.

Alteration of maternal posture and its immediate effect on epidural pressure

A study was undertaken to investigate the changes in pressure inside the epidural space in parturients in the first stage of labour. The purpose was to see whether acute local pressure changes in the epidural space were consistent with the hypothesis that there is physical movement of cerebrospinal fluid with certain changes in maternal posture. Pressure changes were measured via the epidural catheter through which continuous infusion epidural analgesia was administered, using a pressure transducer kept at the level of the lumbar spine. The mothers moved through a series of postures that reflected those expected during the course of labour and delivery. The pressure within the catheter was recorded during these manoeuvres. The pressure changes which were found, taken in conjunction with the associated investigations of others, are consistent with the hypothesis.

Obstetric epidural test doses. A reappraisal

A number of obstetric fatalities related to epidural anaesthesia have been reported recently. In each case catheter or needle misplacement had resulted in a lethal intrathecal or intravascular injection. In this review these cases and a number of other similar but nonfatal reports are examined. In many cases, essential safety checks such as the aspiration test and the test dose had not been performed before the epidural injection but in others one or both of these tests had been used and had failed to predict the complication. Safety test failures generally occurred because ineffective tests were used or because effective tests were inadequately interpreted. This is not surprising because although textbooks recommend a bewildering variety of test doses, they seldom give precise details as to how they should be conducted. A detailed test dose protocol is recommended, which will safely warn of epidural catheter and needle misplacement in the most effective manner possible. If the protocol is used, accidental subarachnoid and intravascular injections can be reduced to a minimum, but they will still occur. It is emphasised that these complications should not cause fatalities if trained personnel and adequate resuscitation facilities are available.