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Rev. Bras. Anestesiol. vol.54 no.4 Campinas July/Aug. 2004
Bilateral pleural block: analgesia and pulmonary functions in postoperative of median laparotomies*
Bloqueo pleural bilateral: analgesia y funciones pulmonares en pós-operatorio de laparotomias medianas
Karl Otto Geier, M.D.
Anestesiologista do Hospital Municipal de Pronto Socorro de Porto Alegre/RS; Anestesiologista Colaborador da Clindor do Hospital São Lucas da PUC/RS; Mestre em Cirurgia pela UFRGS
BACKGROUND AND OBJECTIVES:
Notwithstanding pleural block having become almost an analgesic panacea, contradictory
results have been published. This study aimed at observing analgesic and spirometric
behavior of pulmonary function in the immediate postoperative period of 21 patients
submitted to urgency median laparotomies under bilateral pleural block.
METHODS: Bilateral pleural block was induced in the supine position with 20 mL of 0.375% bupivacaine with 1:400,000 epinephrine administered via catheter in each hemithorax during the immediate postoperative period. Randomized bupivacaine and saline were administered by residents or nurses blind to syringes content, and their analgesic outcomes were evaluated according to Prince Henry's pain score by comparing pre and post bilateral pleural block values. As a function of postoperative pain, spirometric tests of pulmonary function were also applied via a portable spirometer.
RESULTS: All bupivacaine patients referred postoperative analgesia with mean duration of 247.75 ± 75 minutes although there has been mild residual pain in the suprapubic region of five patients (8%) and in the xiphoid apophysis in two patients (3.2%). No analgesic effect was obtained with saline. Pulmonary function evaluated pre and post-blockade were improved with bupivacaine in FVC (p < 0.0367) and FEV1 (p < 0.0051). No improvement was seen in EFP (p < 0.059) and FEV1/FVC ratio (p < 0.1263).
CONCLUSIONS: In our study, postoperative pain control with bilateral pleural block after urgency median laparotomies was null with saline. With bupivacaine, however, analgesia was not considered fully effective in all patients during movements on bed and deep breathing. Pleural block does not seem to have the same analgesic outcome for all patients.
Key Words: ANALGESIA: postoperative; ANESTHETIC TECHNIQUES, Regional: interpleural block; SURGERY, Abdominal
JUSTIFICATIVA Y OBJETIVOS:
No obstante el bloqueo pleural haber sido convertido casi en una panacea analgésica,
fueron publicados resultados contradictorios. El objetivo de este estudio fue
observar el desempeño analgésico y espirométrico de las funciones
pulmonares en el pós-operatorio inmediato de 21 pacientes con el bloqueo
pleural bilateral en laparotomias medianas de urgencia.
MÉTODO: Bloqueo pleural bilateral fue realizado en decúbito dorsal horizontal en 21 pacientes con 20 ml de bupivacaína a 0,375% con adrenalina a 1:400.000 administrados por catéter en cada hemitórax durante el pós-operatorio inmediato. Soluciones aleatorias de bupivacaína y de solución fisiológica fueron administradas por estudiantes en la práctica o enfermeras que desconocían el contenido de las jeringas, y sus resultados analgésicos evaluados de acuerdo con la escala de dolor Prince Henry al comparar los valores pre y pós-bloqueo pleural bilateral. En función del dolor pós-operatorio, ensayos espirométricos de las funciones pulmonares también fueron determinados mediante un espirómetro portátil.
RESULTADOS: Analgesia pós-operatoria, con duración media de 247,75 ± 75 minutos fue constatada en todos los pacientes con la bupivacaína, aunque haya persistido dolor residual de menor intensidad en la región suprapúbica en cinco pacientes (8%) y en dos pacientes en la apófisis xifóide (3,2%). Ningún efecto analgésico fue obtenido con solución fisiológica. De frente al dolor pós-operatorio, las funciones pulmonares, evaluadas antes y después de los bloqueos, registraron mejoría con la bupivacaína en CVF (p < 0,0367), y en el FEV1 (p < 0,0051), y ninguna en el PEF (p < 0,059) y cuociente FEV1/CVF (p < 0,1263).
CONCLUSIONES: En el presente estudio, el control del dolor pós-operatorio por el bloqueo pleural bilateral en laparotomias medianas de urgencia fue nulo con solución fisiológica. Entre tanto, con la bupivacaína el resultado de la analgesia no fue considerado totalmente efectivo en todos los pacientes, durante la movimentación en el lecho y la respiración profunda. El bloqueo pleural parece no tener el mismo resultado analgésico en todos los pacientes.
Pleural block was introduced approximately 20 years ago, as result of the serendipity of two Norwegian anesthesiologists1 who believed had reproduced with multiple intercostal nerve blockades2,3 the same observations of other authors about postoperative billiary tract analgesia by subcostal incision and peripheral regional anesthesia of fractured ribs3,4. At radiological investigation of the spread of the contrast, seemingly introduced in the intercostal space via catheter, they have observed that the contrast had been deposited between the pleurae. Anesthetic solution administration by pleural space catheterization had effectively reproduced the same analgesia of intercostal nerves block5. To explain this analgesia, the authors considered anesthetizing several intercostal nerves during retrograde anesthetic solution spread, from the pleural space to the extrapleural space, phenomenom currently confirmed6. In addition to intercostal nerves1, other nervous strutures may be blocked7. While unilateral pleural block is almost exclusively used for ipsilateral analgesia, bilateral pleural block has virtually not been used. This study has evaluated bilateral pleural block analgesia and spirometric changes of respiratory functions in median laparotomies.
After the Hospital's Ethics Committee approval and their consent, participated in this study 21 patients physical status ASA I and II, weighing more than 50 kg, who were submitted to bilateral pleural block in the Post-Anesthetic Care Unit (PACU), during the immediate postoperative period of median laparotomies determined by stab and gunshot wounds, perforated gastric ulcer and urgency reinterventions. All surgeries were performed in the Hospital de Pronto Socorro under general anesthesia after induction with thiopental (5 mg.kg-1), succinylcholine (1 mg.kg-1), fentanyl (3 to 5 µg.kg-1) and vecuronium (0.08 mg.kg-1), and maintenance with enflurane (1.5% to 2.5%), fentanyl and vecuronium in fractional doses, with late postoperative recovery in the ward. Bilateral pleural blocks were performed in patients without residual analgesia, access way infection, active pleural diseases (pleural effusions) or pulmonary diseases (bronchospastic).
Similar to other studies, modified Prince Henry's score (PHS)8 used by several Scandinavian authors9 was used to evaluate postoperative pain intensity (0 = no pain at rest and moving in bed; 1 = pain when coughing, without pain at deep breathing; 2 = mild to moderate pain during deep breathing, without pain at rest; 3 = mild pain at rest; 4 = moderate pain at rest; 5 = severe pain at rest).
The study involved two stages. In the first stage, bupivacaine was compared to saline (placebo) in 11 patients. In the second stage, pulmonary function under analgesic effect were evaluated in remaining 10 patients. Analgesic evaluations and pre-blockade pulmonary tests (control) were compared to post-blockade values (study) 30 minutes after anesthetic solution administration. Spirometric tests were applied only after the first pain complaint because position is extremely uncomfortable and difficult in the immediate postoperative period due to pain. The best of two measurements was selected. New bupivacaine doses were administered via catheter at approximately 5-hour intervals, due to drug's pharmacokinetics and pharmacodynamics. Weaker analgesics were administered at patients request. According to the study design, bilateral pleural analgesia was induced during the day, leaving the night period for parenteral analgesia so that procedures related to study observations would not disturb the night rest of remaining ward patients.
Expiratory Flow Peak (EFP), Forced Expiratory Volume in 1 second (FEV1) and Forced Vital Capacity (FVC) were evaluated with a portable spirometer (Clement Clarke International Ltd Enhance VMI®, Edimburg), with patients' dorsum positioned 45º to the level of the bed. The study was closed when patients stabilized in PHS level 3, corresponding to a period varying 24 hours to slightly more than 48 hours.
Bilateral pleural block was induced with patients in the supine position with abducted arms, flexed forearms and hands placed laterally or under the head. After desinfection of the median axillary line with iodine alcohol, 4th or 5th rib was located by palpation in the horizontal nipple plane. Then, puncture pathway was anesthetized until rib's periosteum with 2% lidocaine. The same puncture pathway was reproduced with Tuohy needle until contacting the rib. Tuohy needle was then displaced toward upper rib border and going beyond it a few milimeters. Needle mandrel was replaced by a syringe adequate to loss of resistance to air test for pleural space identification. Needle-syringe set was then slowly introduced while a mild digital pressure was exerted on the embolus. In some cases, when the needle reached pleural cavity, pressure gradient between atmospheric pressure on the embolus (positive) and sub-atmospheric pleural pressure (negative) would suck the embolus during inspiration. With the needle tip in the pleural space, bevel was turned to pulmonary apex in the posterior coronal axillary plane. Syringe was immediately replaced by epidural catheter insertion of approximately 20 cm. External portion of the catheter was fixed with adhesive material on the skin up to the infraclavicular fossa, and an antibacterial filter was adapted to its edge. The same procedure was repeated for the other hemithorax.
A Portex® 16G Minipak® puncture was used for each hemithorax, in addition to two identical syringes with 20 mL of the same solution: 0.375% bupivacaine with 1:400,000 epinephrine or saline. Syringes were prepared by the author in batches of three pairs, with two pairs containing bupivacaine and one pair containing saline (placebo). After being labelled 1a, 1b; 2a, 2b; and 3a, 3b, pairs were packed in transparent plastic bags and maintained in a fresh place and away from light. Subsequent batches were prepared according to this model as patients required maintenance of analgesia. By identifying the syringes, we prevented the use of a hybrid pair, that is, a pair made up of one syringe with bupivacaine and the other with saline. At pain complaint, nurses or trauma residents blind to syringes content would apply PHS to evaluate pain level (control value). Then, in the supine position with the dorsum at approximately 45º, pulmonary function were evaluated with the spirometer and patients were returned to the supine position with the trunk slightly elevated at approximately 10º. In the sequence, nurses or residents would randomly choose a pair of syringes and injected their contents via catheter slowly and simultaneously during inspiratory movements, in a period never less than 5 minutes for the solutions to flow from paravertebral apex to lower portions through the costovertebral leak, reaching intercostal nerves. PHS and spirometer measurements were repeat 30 minutes after (study values).
Patients demographics data and analgesia duration are expressed in mean and standard deviation. Mann-Whitney test was applied to determine whether bupivacaine or saline doses were randomly administered throughout the study. Pleural analgesia results were expressed in relative frequencies and analgesia was characterized when there was a decrease of one or more PHS values. Fisher's Exact test was used in the second stage of the study to evaluate comparative analgesic effects between bupivacaine and saline.
Pulmonary function spirometric changes were analyzed by relative frequencies and median with inter quartile interval. Paired Wilcoxon's test for EFP, VEF1, FVC and VEF1/FVC before and after bupivacaine administration aimed at evaluating ventilatory parameters changes. For all statistical tests, p < 0.05 was considered statistically significant.
Forty two catheters were inserted in the pleural space, through which 79 pleural administrations were performed, being 62 with bupivacaine and 17 with saline (placebo), in patients whose characteristics are shown in table I.
The study lasted slightly more than 48 hours and mean effect per bupivacaine dose was 249.75 ± 93.67 minutes, with a mean postoperative duration of 201.42 ± 72.33 minutes in 21 patients, 250.95 ± 103.33 minutes in 21 patients, 293.75 ± 84.72 minutes in 15 patients, 312 ± 65.72 minutes in 5 patients, 330 ± 127.27 minutes in 2 patients and 240 minutes in 1 patient, with the 1st, 2nd, 3rd, 4th, 5th and 6th bupivacaine dose, respectively.
The improvement/no improvement outcome with bupivacaine and saline according to PHS has been determined by Fisher's Exact test (Table II).
The same was not true for pleural saline administration. Only one patient has referred mild analgesia throughout the abdominal incision with decrease of just one PHS level.
Under bupivacaine effect, however, pain although decreased throughout surgical incision (T7-T12) has remained residual in some moments (Table V).
Spirometric evaluation of pulmonary functions was obtained in stage two for 10 patients (Table VI) with clinical and statistically significant improvement with bupivacaine, although some measurements were lower, probably due to expiratory flow leakage between the spirometer mouthpiece and the oral cavity.
Pulmonary evaluations: EFP (L.min-1), VEF1 (L/1 sec), FVC (L) and VEF1/FVC (Tiffeneau index) were expressed in relative frequencies through median (spread measurement). Paired Wilcoxon's test pre and post bupivacaine was expressed in relative frequencies through median (dispersion measurement). Spirometric tests profile before and after bilateral pleural blocks are shown in tables VII, VIII, IX and X.
Since any interventional procedure is subject to complications and being bilateral pleural block an invasive technique, there have been complications, which are shown in table XI.
Radiological evaluation was performed approximately 7 hours after catheters insertion in the first 7 patients and as there were no radiological signs of pneumothorax and/or phrenic nerve paralysis, chest X-ray was only requested for remaining patients when there was suspicion of pneumothorax.
There were no pharmacodynamic manifestations of toxicity with 20 mL of 0.375% bupivacaine with 1:400,000 epinephrine in each hemithorax when 3 mg.kg-1 bupivacaine dose was established to be administered at 5-hour intervals.
Postoperative analgesia of interventions knowingly very painful, including chest and abdominal procedures, has to be efficient to provide adequate immediate postoperative comfort by mitigating neuroendocrine-metabolic responses. In most cases, opioids in this stage have ambivalent results, either with insufficient analgesia or with secondary effects. Local (incision infiltration) or regional (individual block of intercostals nerves) postoperative analgesia with local anesthetics is seldom used.
Abdominal wall innervation is achieved by homologous intercostal spinal nerves, which cross along the anterior median line extending from the xyphoid apophysis to the pubic symphysis (T7-T12). Thus, median incisions need anesthetic block of intercostals nerves on both sides. As from this anatomic understanding, this study was performed with bilateral pleural block with 0.375% bupivacaine with 1:400,000 epinephrine as an alternative for opioid analgesia. Pleural block is nothing more than multiple anesthetic blocks of several intercostal nerves or of several segments of the sympathetic chest chain6, by the administration of local anesthetics between visceral and parietal pleurae1 in the supine position. Gravity action on administered volume and retrograde spread of the anesthetic solution from the pleural space to the extrapleural space determine neural tissue soaking. Patients' positioning is then relevant for the pharmacological success. With the target hemithorax facing upwards, 90º lateral position results in the soaking of the paravertebral sympathetic chain while 45º lateral position determines the soaking of intercostal nerves (Figure 1)10.
Bilateral pleural block is needed for abdominal wall analgesia in median incisions, thus the change in position. For such, patients should be positioned now in one then in other lateral position. Since we are talking about the immediate postoperative period of laparotomies with extensive median incisions, common in urgency surgeries, these maneuvers, in addition to being uncomfortable are potentially morbid by suture dehiscence. As an alternative, bilateral pleural block by median axillary line was proposed with patients remaining in the supine position1.
Notwithstanding pleural block analgesia is questioned for thoracotomies11-13 and laparotomies14, observations in our country have revealed satisfactory analgesia15-17.
The analgesic effect of our study has been evaluated by Prince Henry Score before and after bilateral pleural block. This score is specifically related to the immediate postoperative period with active chest and upper abdominal movements, respiratory physical therapy and coughing. Our study has shown that analgesia was not fully effective, although patients have referred changes in PHS (Table II and III). Five patients (23.8%) have referred low intensity pain in the suprapubic region (T12) and two patients (8.5%) have referred pain in the xyphoid region (Table XI). If 20 mL of anesthetic solution cover approximately 6 to 7 metamers18, enough to cover T7-T12 and knowing that A, delta b and C nervous fibers making up intercostal nerves respond well to local anesthetics without impairing respiratory mechanics, incomplete analgesia observed in our study might have been due to: 1) insufficient anesthetic volume to reach all involved intercostal nerves; 2) inadequate patient positioning; 3) insufficient anesthetic solution concentration; or 4) the combination of such factors.
There is a consensus that maximum bupivacaine dose should be 3 mg.kg-1 with 1:200,000 epinephrine. Mean bupivacaine permanence is approximately 5 hours. Our study has complied with such considerations.
Analgesic effect was also indirectly measured by spirometric tests of pulmonary functions before and after blockades due to the incompatibility between diaphragm movements and high abdominal incision pain.
Short and superficial ventilatory regimen is characteristic of pain caused by movement and/or displacement of tissues injured by high abdominal incisions, traumas and chest incisions. The more severe the pain, the higher the functional residual capacity decrease which allows for postoperative microatelectasis and pneumonia's. Respiratory function measurements, especially EFP, VEF1 and FVC are useful for patients submitted to thoracotomies and high abdominal surgeries. After pleural blockade it has been observed that just VEF1 and FVC have decreased20 and that phrenic nerve paralysis21 is a potential intercurrence which may promote 50% vital capacity decrease20 however without hemoglobin saturation changes or clinical manifestations20. In the case of bilateral pleural block, the possibility of bilateral phrenic paralysis becomes a concern. However, posterior catheter positioning and its distance from the phrenic nerve, which is anterior and medial to the mediastinum, associated to a mild cephalad positioning of patients' trunk during anesthetic solution administration favoring its flow through costovertebral leak22,23 and dependent regions, prevent diaphragm paralysis.
A CT image of one patient has shown spread of contrast injected by pleural catheters. Image cross-section was very low, showing contrast distribution from the right hemithorax to the aorta. Since this patient had no clinical signs or symptoms of respiratory failure, additional X-ray studies were not requested (Figure 2).
The more posterior is the catheter, thus closer to the costo-vertebral leak, the more prolonged is the analgesia20,23. Original pleural analgesia duration was in average 10 hours in 78 out of 81 patients24. In our series of 21 patients, only one has referred 10 hours relief and 2 patients 8 hours relief during the 62 bupivacaine blockades in which results have been extremely significant for bupivacaine (p < 0.001) (Table II) as compared to saline.
In evaluating analgesia promoted by saline, there has been decrease of just one PHS level (Table II and V) after five pleural blocks, different from Brismar et al.25 findings. In both cases, the small series of pleural blocks with saline solution was interrupted to prevent prolonged suffering of patients medicated with placebo in the immediate postoperative period when pain is more severe in the first 48 hours.
Catheters with more than 48 hours (2 patients) were sent to the lab for microbiological analysis. From the four duly identified catheters, only one has shown staphylococcus epidermidis contamination of low virulence and seemingly without major clinical significance.
In summary, there has been no postoperative pain control with bilateral pleural block in urgent median laparotomies when saline was administered. However, when bupivacaine was administered, resulting analgesia was not fully effective during movement on bed and deep breathing. Pleural block does not seem to have the same outcome for all patients.
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Dr. Karl Otto Geier
Address: Rua Cel. Camisão, 172
ZIP: 90540-030 City: Porto Alegre, Brazil
Submitted for publication August
Accepted for publication November 6, 2003
* Received from Hospital Municipal de Pronto Socorro de Porto Alegre, RS