Saudi Journal of Anaesthesia

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 13  |  Issue : 1  |  Page : 52--59

Comparative study of mid-thoracic spinal versus epidural anesthesia for open nephrectomy in patients with obstructive/restrictive lung disease: A randomized controlled study


Nazmy Edward Seif, Ahmed Mohamed ELbadawy 
 Department of Anesthesia, Faculty of Medicine, Cairo University, Cairo, Egypt

Correspondence Address:
Dr. Nazmy Edward Seif
Department of Anesthesia, Faculty of Medicine, Cairo University, Kasr Al-Ainy St., Cairo
Egypt

Abstract

Background: The aim of this randomized controlled study is to compare the safety and efficacy of thoracic spinal versus thoracic epidural anesthesia for open nephrectomy in patients with obstructive/restrictive lung disease. Methods: Sixty patients with mild to moderate chronic obstructive/restrictive lung disease undergoing open nephrectomy were randomized into two groups, 30 patients each. The thoracic spinal group (TSA) group received ultrasound guided mid-thoracic spinal anesthesia, and the thoracic epidural group (TEA) group received thoracic epidural anesthesia. All blocks were performed at the T7-T8. Hemodynamics, visual analogue scale score, sensory and motor block profile as well as any adverse events, and patient satisfaction were all reported. Results: Both blocks were successfully performed and were effective for surgery in all patients, with the exception of only one patient in TSA group who needed to receive general anesthesia even after IV midazolam because of extreme anxiety and was excluded from the study analysis. The sensory block ranges were quiet close, with T2-T5 for the TSA group and T3-T6 for the TEA group as the upper level and L3-L5 as the same lower level. The values for the onset time and the duration of sensory and motor blocks were lower in TSA group. There were no statistically significant differences existed in intraoperative VAS, and hemodynamics between the two groups. Postoperative adverse effects were negligible and insignificant, with no case reporting any neurological sequel. Conclusion: Ultrasound guided thoracic spinal anesthesia can be performed safely and effectively for open nephrectomy in patients with obstructive/restrictive lung disease with the potential for an early ambulation and great patient satisfaction.



How to cite this article:
Seif NE, ELbadawy AM. Comparative study of mid-thoracic spinal versus epidural anesthesia for open nephrectomy in patients with obstructive/restrictive lung disease: A randomized controlled study.Saudi J Anaesth 2019;13:52-59


How to cite this URL:
Seif NE, ELbadawy AM. Comparative study of mid-thoracic spinal versus epidural anesthesia for open nephrectomy in patients with obstructive/restrictive lung disease: A randomized controlled study. Saudi J Anaesth [serial online] 2019 [cited 2019 Feb 18 ];13:52-59
Available from: http://www.saudija.org/text.asp?2019/13/1/52/248849


Full Text



 Introduction



Chronic obstructive and restrictive lung diseases pose a challenge to the anesthetist because of the increased risk of perioperative comorbidities. General anesthesia (GA) and in particular endotracheal intubation and intermittent positive pressure ventilation (IPPV) is associated with adverse outcomes. Such patients are prone to laryngospasm, bronchospasm, cardiovascular instability, barotraumas, hypoxemia, and increased need of postoperative ventilation.[1] Nephrectomy has traditionally been performed under GA; however, spinal anesthesia has lower postoperative mortality and fewer complications than GA.[2] A review of 141 prospective, randomized trials comparing neuraxial versus GA demonstrated decreased mortality and decreased incidence of postoperative pulmonary and cardiac complications, renal failure, and deep venous thrombosis in the patients receiving neuraxial anesthesia.[3],[4] Thoracic spinal anesthesia has been used recently as an alternative anesthetic technique for patients with severe lung disease and for healthy patients, for procedures such as cholecystectomy and breast surgery.[2],[5] In recent studies, it was found that a greater distance between the dura mater and the spinal cord exists in the mid-thoracic region (T7-T8), which makes spinal needle introduction into the subarachnoid space at that level more safe, but still strict precautions are needed.[6],[7]

Investigating the applicability of various alternative regional anesthetic techniques to GA, for nephrectomy candidates having lung disease, would be of great clinical relevance to avoid airway manipulation, muscle relaxant usage, and mechanical ventilation with their possible complications in this population.

With the unavailability of previously conducted studies, the main objective of the current one is to compare mid-thoracic spinal versus epidural anesthesia for open nephrectomy in patients with obstructive/restrictive lung disease. The primary outcome of our study was to evaluate patient satisfaction if ultrasound guided mid-thoracic spinal anesthesia is used as the sole anesthetic technique. The secondary outcomes were to compare ultrasound guided mid-thoracic spinal versus epidural anesthesia as regard the efficacy, sensory and motor blocks, visual analogue scale (VAS) score, hemodynamic parameters, and intra- and postoperative complications.

We hypothesized that providing mid-thoracic subarachnoid block under ultrasound guidance would be feasible and effective as well as thoracic epidural anesthesia when used for open nephrectomy in lung disease patients.

 Methods



Following approval of the trial protocol by the Institute Local Research and Ethics Committee and registration to ClinicalTrials.gov with ID: NCT03324490, a written informed consent form was obtained from all recruited patients, after being given a full explanation about the experimental procedure.

The study was conducted in Kasr Al-Ainy Hospital on 60 nephrectomy candidate patients, aged between 18 and 70 years, American Society of Anesthesia (ASA) class II or III, diagnosed to have either mild [Forced Expiratory Volume 1/Forced Vital Capacity (FEV1/FVC) <70%, FEV1 at least 80% of predicted] to moderate [FEV1/FVC <70%, FEV1 50%–80% of predicted] obstructive and mild [Total Lung Capacity (TLC) 65%–80%] to moderate [TLC 50%–65%] restrictive lung disease; with exclusion of patients having any condition contraindicating regional anesthesia or being allergic to any of the study drugs.

Routine preoperative evaluation, including history taking, general examination, and laboratory investigations, was performed for all patients. The patients were assured that any pain, anxiety, or discomfort during surgery would be treated effectively or, if they preferred, conversion to GA.

Using computer and sealed envelope randomization, the patients were assigned to receive either thoracic spinal anesthesia [thoracic spinal group (TSA) group: n = 30] or thoracic epidural anesthesia [thoracic epidural group (TEA) group: n = 30]. After the insertion of an 18 G IV cannula, each patient was pre-medicated with midazolam 2 mg, ranitidine 50 mg, and ondansteron 4 mg; a volume of 10 ml/kg of Ringer acetate solution was infused intravenously.

Upon arrival to the operating theater, all patients were monitored using 5-lead electro-cardiogram with S-T segment analysis, pulse oximetry, and non-invasive blood pressure.

Every patient was instructed to assume the sitting position with the head flexed. Ultrasound guidance with a 2–5 MHz curved array probe (SonoSite M-Turbo; SonoSite Inc., Bothell, Washington, USA) was used to determine the required level. The counting up method from the last rib was applied to underline the T7-T8 vertebral levels. The probe was oriented in a sagittal direction and placed at the level of the 12th rib in a para-sagittal plane 2 cm from the midline. The probe was moved in a cephalad direction, and the ribs were counted up until the 7th or 8th rib was reached; the probe was then directed medially to identify the ligamentum flavum at the T7-T8 inter-vertebral space, and a skin mark was performed to identify the correct level of the block.

Under complete aseptic conditions, after sterilization of the back, the skin of the puncture site was infiltrated with 2 ml lidocaine 2%, and an epidural catheter was inserted for all patients of both groups. The “Prefix Custom Epidural Anesthesia Tray” with an 18 G Tuohy epidural needle and a 20 G epidural catheter was used as the epidural set. The epidural space was accessed using para-median approach with the loss of resistance to air method. The epidural catheter was threaded in the space and tapped in place, leaving 3 cm within the epidural space. The epidural catheters were tested by negative aspiration through the catheter and by injection of 3 ml lidocaine 2% to exclude intravenous or subarachnoid insertion.

Spinal anesthesia was then performed for patients of the TSA group only, using a 27 G pencil point needle with an introducer (Braun Melsungen, Melsungen, Germany) in the same space (T7-T8). When correct placement was confirmed by the free flow of clear CSF, 1.5 ml of hyperbaric bupivacaine 0.5% (7.5 mg) in addition to 0.5 ml fentanyl (25 μg) and 5 μg dexmedetomidine were injected.

Patients of the TEA group initially received 5–10 ml of a mixed preparation of 0.5% isobaric bupivacaine with 2 μg fentanyl per ml volume as a bolus dose using the epidural catheter, this was followed by a continuous infusion of 5–10 ml/h started 1 h after the bolus dose and continued throughout the procedure.

At first, all patients laid flat in the supine position till full establishment of the block; then they were placed in a “modified supine position” having the chest and upper abdomen positioned at a 45° angle from the operating table and the lower abdomen placed as flat as possible (a torque configuration, with a long sandbag behind the back maintaining this position) while breaking the table at the anatomic landmark of the anterior superior iliac spine. Supplemental oxygen 2–3 l/min was administered through a face mask or nasal prongs.

The upper and lower levels of sensory block were assessed by warm/cold discrimination and pin prick methods every 5 min after performing the block until reaching the desired block level from T4 to L2, then re-assessed every 15 min until the end of the procedure. Surgery was initiated only when an adequate sensory block was achieved. The degree of motor block in the lower limbs was assessed at the same time points by the modified Bromage scale [0: free movement of legs and feet; 1: just able to flex knees with free movement of feet; 2: unable to flex knees but with free movement of feet; and 3: unable to move legs or feet]. The time required to achieve the desired sensory level was recorded. The maximum upper and lower sensory levels reached were recorded. During the procedure, the patients were encouraged to report any discomfort or pain.

Intraoperative anxiety was treated with re-assurance and midazolam bolus of 1–2 mg intravenously. Pain was initially treated by pethidine 1 μg/kg IV boluses and intravenous infusion of 1 g paracetamol. Supplemental epidural injections were to be administered in aliquots of 5 ml isobaric bupivacaine 0.5% only if sensory block reseeds below T5 dermatome, and systemic drugs were ineffective in controlling pain. GA was to be given if all the above measures fail to relieve pain, if the surgeons face a technical difficulty of the surgery necessitating conversion to GA or in case of lack of patient satisfaction with regional anesthesia at any time during the procedure. Nausea and vomiting were treated by additional intravenous administration of 4 mg of ondansteron. The need for supplemental analgesics or anti-emetics was recorded.

10 cm VAS score was assessed every 30 min intraoperatively and until patient discharged from the post-anesthesia care unit (PACU). Vital signs [mean blood pressure (MBP), heart rate (HR), and oxygen saturation (spO2)] were recorded every 5 min for the first 30 min and then every 15 min till the end of the procedure.

Hydration was maintained during surgery with Ringer acetate solution 10 ml/kg/h. Any episode of hypotension or bradycardia was recorded. Hypotension (defined as decrease in MBP >20% of the baseline) was treated initially with ephedrine 10 mg IV followed by a fluid bolus of 250 ml Ringer acetate solution if needed. Bradycardia (defined as HR <50 bpm) was treated with atropine 0.5 mg IV. Blood transfusions and other procedures followed the usual standards.

Operative time and any intraoperative incidents, as well as the total volume of local anesthetic used, were recorded. In the PACU, the sensory level of the block was assessed every 15 min and the time until complete regression of the block was recorded. The degree of motor block was assessed at the same time points. The patients were discharged from the PACU after total regression of the block, provided that postoperative pain was well controlled by systemic analgesics; in the form of ketolorac 30 mg IV, paracetamol 1 g IV, and/or nalbuphine 5–20 mg IM whenever needed. Epidural catheters were removed just prior to patients discharge to their respective wards. Other postoperative events potentially related to the anesthetic procedure, such as urinary retention, pruritis, post-dural puncture headache, or any neurologic sequel, were also recorded. The patient's degree of satisfaction was evaluated after discharge from the PACU and graded as excellent, fair, or poor.

Statistical analysis

Data were statistically described in terms of mean ± standard deviation (± SD), median and range, or frequencies (number of cases) and percentages when appropriate. The comparison of numerical variables between the study groups was done using Student t test for independent samples. For comparing categorical data, Chi-square test was performed. Exact test was used instead when the expected frequency is less than 5. The P values less than 0.05 was considered statistically significant. All statistical calculations were done using computer program IBM Statistical Package for the Social Science (SPSS; IBM Corp, Armonk, NY, USA) release 22 for Microsoft Windows.

Sample size

Sample size calculation was done using the comparison of patient satisfaction score between TSA and TEA groups. As reported in previous publication,[8] the mean ± SD of patient satisfaction in TSA group was approximately 3.6 ± 0.9, and in TEA group it was approximately 2.9 ± 0.9. Accordingly, we calculated that the minimum proper sample size was 27 participants in each arm to be able to detect a real difference of 0.7 units with 80% power at α = 0.05 level using Student's t test for independent samples. The sample size calculation was done using StatsDirect statistical software version 2.7.2 for MS Windows, StatsDirect Ltd., Cheshire, UK.

 Results



Sixty-three patients fulfilled the criteria of the study candidate for open nephrectomy in Kasr Al-Ainy Hospital. Three patients refused to participate in the study. The remaining sixty agreed to participate in the study (recruitment of the patients was started at November 2017). The included patients were randomized into two groups (n: 30 in each group): Group 1 (TSA); operation was done under thoracic spinal anesthesia. One patient of this group was converted to GA as the patient was irritable and uncooperative even after activation of epidural anesthesia and IV midazolam. This patient was excluded from the analysis, and therefore, 29 patients were included in the analysis. Group II (TEA); operation was done under thoracic epidural anesthesia (n: 30 patients), included in the analysis [Figure 1].{Figure 1}

The two groups were comparable with respect to age, gender, and ASA status, type of respiratory disease (obstructive and restrictive), ASA category, duration of anesthesia, and the intraoperative blood loss with no statistically significant differences between the two groups (P > 0.05), as shown in [Table 1].{Table 1}

The desired level of sensory block for surgery (T6-L2) was achieved in all patients of both groups, but the mean time for the block to reach this level was 6 ± 2 min in TSA group and 17 ± 2 min in TEA group, which was statistically significant (P < 0.05). In addition, there was statistically significant difference between the two groups as regarding the mean time to reach the maximum sensory block; it was 8 ± 2 and 19 ± 2 min in TSA and TEA, respectively (P < 0.05) [Table 2].{Table 2}

There was no statistically significant difference between both groups as regarding the maximum upper and lower level of sensory block as well as the intraoperative VAS. The mean time of 2-segment sensory block regression was longer in the TEA group (221 ± 23 min) than that in the TSA group (113 ± 11 min). Only one patient from TSA group needed intraoperative IV analgesia in the form of pethidine 50 mg. The mean time to 1st rescue analgesia was longer in TEA group (416 ± 33 min) than that in the TSA group (360 ± 22 min) [Table 2].

As regarding the motor block, there was no statistically significant difference between the two groups in the Bromage scale before surgery, but at the end of surgery, it was 0–1 in 23 patient (79.3%) and 2–3 in 6 patients (20.68%) in TSA group and 2–3 in all patients (100%) of TEA group. In addition, the mean time of regression of the Bromage scale to 0 was shorter in TSA group (261 ± 25 min) than that in the TEA group (342 ± 26 min) [Table 3].{Table 3}

The studied cardiovascular changes (i.e., mean arterial blood pressure [ABP] and HR) were minor and insignificantly affected the two groups [Figure 2] and [Figure 3]. Four patients of the TSA group and three patients of TEA group developed intraoperative hypotension treated with IV fluids and ephedrine (5–10 mg). In addition, two patients of TSA group and one patient of TEA group developed bradycardia which was treated with IV atropine 0.5 mg, but these results were statistically insignificant (P > 0.05). Three patients from TSA group and two patients from TEA group developed intraoperative nausea and vomiting which was treated with IV ondansetrone 4 mg. There was no intraoperative pruritus or anxiety reported in all patients [Table 4].{Figure 2}{Figure 3}{Table 4}

There was no postoperative urine retention, nausea and vomiting, itching, neurological sequelae, or post-dural puncture headache reported in any patient of both groups. In the TSA group, twenty-six patients (89.65%) were totally satisfied, two patients (6.89%) reported average satisfaction, and only one patient (3.44%) was unsatisfied. In the TEA group, twenty-eight patients (93.33%) were totally satisfied and two patients (6.66%) reported average satisfaction [Table 5].{Table 5}

 Discussion



Patients with major medical problems, especially respiratory disease, have high risk of intra- as well as postoperative complications when undergoing GA. Thoracic epidural anesthesia has been found effective as the sole anesthetic technique for nephrectomy when GA implies a high risk. In addition, many investigators reported that segmental spinal anesthesia can be used safely in patients with severe lung disease.[9],[10],[11] This study compares the feasibility and effectiveness of these two regional anesthetic regimens as possible alternatives to GA during nephrectomy procedures.

In our studied population, either segmental subarachnoid or epidural mid-thoracic blocks were successfully performed and provided adequate level of surgical anesthesia, sufficient enough to operate for nephrectomy, with controllable hemodynamic effects while avoiding any airway manipulation.

The T7-8 intervertebral space was chosen to perform the block for two reasons. First is to cover the surgical field extending from T5 to L2 and allowing segmentation of the spinal block, as the injected local anesthetic and opioids exert their highest effects on the surgically relevant segmental levels. The second reason, for choosing this level, was depending on the MRI results found by both Lee et al.[12] and Imbelloni et al.[6] Lee demonstrated that a larger distance between the dura mater and the spinal cord exists at the T6 level (9.5 ± 1.8 mm); whereas Imbelloni noted that the largest posterior subarachnoid distance is at T2 and T10 levels; providing the fact that in the mid-thoracic region, the spinal cord is more vertically located and distant from the dura, minimizing the potential risk of its injury because of the substantially wider posterior dural – spinal cord distance.

In addition, Lee et al. concluded, in their anatomical study, that placing the patient in a head-down sitting position increases the posterior separation of the dura mater and the spinal cord, compared with both the supine and the lateral positions, favoring our choice of the sitting position with forced thoracic flexion.

A proactive insertion of an epidural catheter was done for patients of the spinal anesthesia group to act as a safe valve in case of an unexpected lengthy procedure. Accordingly, dexmedetomidine was added to the neuro-axially injected mixture, to prolong both sensory and motor blocks.[13]

The sensory block range achieved in the TSA group was insignificantly wider than that in the TEA group [T2-T5 vs. T3-T6 as the upper level and L3-L5 as the same lower level], adequately covering the desired surgical dermatomes without extensive spread to unnecessary spinal segments in either group. This was aided by the choice of the middle of the thoracic region as the injection level, gaining benefit of the normal concavity of the vertebral canal at the thoracic region. These block levels match those obtained by Van Zurdet et al., with their choice of the T10 level to perform the initial segmental anesthesia for laparoscopic cholecystectomy and reaching T2-T4 as the upper level and L1-L5 as the lower level of the sensory block.[14]

The occurring degree of lower limbs motor block is explained by the physical spread of the local anesthetic to the lumbosacral nerve roots.

A significant delay in the onset time needed to achieve the desired sensory block levels, as well as the time to reach its maximum, were noted in the TEA group compared with the TSA group [17 ± 2 min vs. 6 ± 2 min and 19 ± 2 min vs. 8 ± 2 min, respectively].

However, the time to two segments regression of the sensory block and the complete regression time of the motor block were both faster in the TSA group [113 ± 11 min vs. 221 ± 23 min and 261 ± 25 min vs. 342 ± 26 min, respectively].

In addition, the previous variation in the quality of the sensory block between the two study groups also explains the earlier need for postoperative analgesia in the TSA group [360 ± 22 min vs. 416 ± 33 min in the TEA].

Furthermore, there was a significant difference between the duration for motor block regression and the time till the 1st rescue analgesic dose used as a reflection of fading of the sensory block, in each group [261 ± 25 min vs. 360 ± 22 min in the TSA group and 342 ± 26 min vs. 416 ± 33 min in the TEA group]; the former being much more shorter.

These results are in agreement with those found by Imbelloni et al. in their comparative study between conventional-dose and low-dose hyperbaric bupivacaine in laparoscopic cholecystectomy under spinal anesthesia.[15]

Subsequently, 23 patients in the TSA group (79.3%) were able to move from the table to the stretcher un-aided, compared to “0%” in the TEA group, giving the former the advantage of an earlier ambulation, partly because of the smaller dose of bupivacaine used in our study being injected in the thoracic region and partly because of the deposition of this hyperbaric dose (in the TSA group patients) predominantly on the sensory nerve roots (posterior) in relation to the motor nerve roots (anterior and uppermost).

Concerning the hemodynamic variables, studied as mean ABP and HR, the cardiovascular changes were minor and insignificantly affected the two groups, as reflected in the minimal and similar need for vasopressor support of both groups; in spite the expected reduction of the sympathetic tone secondary to the block of cardiac fibers (T1-T4). This may be because of the fact that our patients were adequately pre-loaded and remained conscious throughout the procedure, avoiding significant central depression of circulation.

In contrast, Elakany et al.[16] proved that hypotension and bradycardia developed in 15% of cases that received segmental thoracic spinal anesthesia. However, our findings coincide with those of Imbelloni L E,[15] who used a similarly reduced dose of hyperbaric bupivacaine (7.5 mg) given in combination with fentanyl, and achieved less hemodynamic instability and fewer adverse events.

As for the concern of affection of the respiratory parameters resulting from thoracic nerves block, the peripheral “SpO2” was well preserved within the range of 96–100%; as the diaphragm which is the main inspiratory muscle was unaffected being innervated by the phrenic nerve (originating from C3-5), whereas expiration occurs passively.

VAS values did not differ intraoperatively between the two study arms. Intraoperative I.V. analgesia was needed for only one patients in the TSA group [P value: 0.076], whereas additional epidural injection was given as a rescue dose for one patients in the TEA group (3.44%). Conversion to GA was required for just one patient in the TSA group due to persistent anxiety and irritability [P value: 0.76].

Being performed under U/S guidance, no parethesia was encountered during initial spinal needle insertion, with no case reporting any neurological sequelae. This incidence is lower than those noted by Imbelloni et al.[17] (6.6%) and Van Zudert et al.[14] (5%).

No significant differences were noticed between the spinal and the epidural groups concerning the intra- and postoperative adverse effects, namely pruritis, nausea, and vomiting; whereas neither urinary retention nor post-dural puncture headache occurred in any patient.

At the end of surgery, the patients were remarkably satisfied with both techniques, and the satisfaction scores in both groups were comparable (89.65% and 93.33% excellent for the TSA and the TEA groups, respectively; P value: 0.64).

 Conclusion



In summary, our present study shows that either of the thoracic spinal or epidural segmental block provides adequate intraoperative anesthesia for surgical nephrectomy; and that both can be effectively and safely used as an alternative technique where GA is not advisable, without any significant complications and with a considerably high patient satisfaction rate.

The lower local anesthetic dose of the subarachnoid block, which is otherwise compensated by the addition of dexmedetomidine, was translated in a faster recovery of motor and sensory functions, giving this technique the advantage of earlier ambulation.

Limitations to this study are the relatively small number of patients included as well as performing surgery with patients in a modified supine position requested by the surgeon. Further studies with larger sample sizes and different patient position (lateral position) are required to detect any potential disadvantages or complications associated with the techniques. Nevertheless, familiarity and experience with these techniques should always be considered.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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