High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia in outpatient procedures: clinical implications

Abstracts

JUSTIFICATIVA E OBJETIVOS: Sob bloqueio peridural torácico baixo ou médio, as alterações hemodinâmicas são facilmente controladas. Como o bloqueio peridural torácico alto (T2-T3) acomete, freqüentemente, as raízes do plexo braquial (C4)C5-T1(T2), algumas destas responsáveis pela formação do nervo frênico (C3-C4-C5) é de se supor, possíveis repercussões motoras deste último. O presente estudo realizado em cirurgias estéticas, sob bloqueio peridural segmentar isolado em T2-T3 ou associado ao bloqueio peridural segmentar em T11-T12, avaliou as repercussões motoras na dinâmica respiratória assim como nos membros superiores e inferiores. MÉTODO: Trinta e duas pacientes, estado físico ASA I e II, sem doença pulmonar broncoespástica, em atividade e peso corporal igual ou superior a 50 kg, foram submetidas a 21 bloqueios peridurais torácicos isolados em T2-T3 e as 11 restantes, a bloqueios combinados em T11-T12, com ropivacaína a 7,5% (45 a 90 mg) associada ao sufentanil (10 a 20 µg). Repercussões hemodinâmicas, respiratórias e motoras nos membros superiores e inferiores foram avaliadas respectivamente, sob monitorização não-invasiva, espirometria, força de preensão da mão e escala de Bromage. RESULTADOS: A média de duração das cirurgias mamárias foi de 105 minutos com depressão motora dos membros superiores (p < 0,001), com recuperação motora acontecendo aos 117,2 ± 51,3 minutos e a primeira manifestação de dor aos 485 ± 221,2 minutos. As cirurgias combinadas, que tiveram uma duração média de 165 minutos, com depressão motora dos membros inferiores grau 1, em 40% e grau 2, em 60% das pacientes pela escala de Bromage, sua recuperação ocorreu aos 223,9 ± 57,1 minutos e a primeira manifestação de dor em repouso, aos 555 ± 197,9 min. As funções pulmonares, VEF1 (l/seg); PFE (l.min-1); CVF (litros) apresentaram-se alteradas respectivamente, em 15,20% (p < 0,009); 13,36% (p < 0,029) e 18,09% (p < 0,007), com elevação de 8,75% do VEF1/CVF (p < 0,162). Hipotensão arterial (< 30 % dos valores iniciais) e bradicardia (< 55 bpm) ocorreram em cinco pacientes e tremores durante os bloqueios, em treze pacientes. CONCLUSÕES: Sob bloqueio torácico alto ou cérvico-torácico com doses e volumes reduzidos de soluções anestésicas, ocorrem repercussões motoras nos membros superiores e nas funções pulmonares. No entanto, a julgar por observações preliminares e do presente estudo, as alterações espirométricas foram estatisticamente significativas, porém, sem expressão clínica na dinâmica respiratória, sendo essencialmente decorrentes da paralisia dos nervos intercostais, mais que do nervo frênico.

ANESTESIA; TÉCNICAS ANESTÉSICAS; TÉCNICAS ANESTÉSICAS

SCIENTIFIC ARTICLE

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia in outpatient procedures: clinical implications^*

Peridural torácica alta asociada o no a la peridural torácica baja en pacientes ambulatoriales: implicaciones clínicas

Djalma Sperhacke, M.D.^I; Karl Otto Geier, M.D.^II; João Carlos Correia Eschiletti, M.D. ^III

^IAnestesiologista da Clínica Rio Branco

^IIAnestesiologista 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

^IIICirurgião Plástico da Clínica Rio Branco

^{Correspondence}

SUMMARY

BACKGROUND AND OBJECTIVES: Hemodynamic changes are easily controlled under low or median thoracic epidural block. Since high thoracic epidural block (T₂-T₃) often affects brachial plexus roots (C₄) C₅-T₁(T₂), some of them responsible for phrenic nerve formation (C₃-C₄-C₅), potential motor repercussions on this nerve are to be expected. Our study performed during cosmetic surgeries under isolated segmental epidural block in T₂-T₃ or associated to segmental epidural block in T₁₁-T₁₂, has evaluated motor repercussions on respiratory dynamics, upper and lower limbs.

METHODS: Participated in this study 32 patients physical status ASA I and II, without active bronchospastic pulmonary disease and body weight equal to or above 50 kg, 21 of whom were submitted to isolated thoracic epidural blocks in T₂-T₃ and the remaining patients (11) were submitted to a combined thoracic epidural blocks in T₁₁-T₁₂ with 7.5% ropivacaine (45 to 90 mg) associated to sufentanil (10 to 20 µg). Hemodynamic, respiratory and upper and lower limbs motor repercussions were evaluated by noninvasive monitoring, spirometry hand grasping strength and Bromage score, respectively.

RESULTS: Mean mammary surgeries duration was 105 minutes with upper limbs motor depression (p < 0.001), with motor recovery at 117.2 ± 51.3 min and first pain complaint at 485 ± 221.2 min. Combined surgeries with mean duration of 165 min, with lower limbs motor depression level 1 in 40% and level 2 in 60% of patients according to Bromage score, with recovery at 223.9 ± 57.1 min and first pain complaint at rest at 555 ± 197.9 min. Pulmonary functions VEF1 (L/sec); PFE (L.min^-1); FVC (liters) were changed in 15.20% (p < 0.009); 13.36% (p < 0.029) and 18.09% (p < 0.007), respectively, with 8.75% VEF1/FVC increase (p < 0.162). There has been hypotension (< 30% above baseline values) and bradycardia (< 55 pbm) in 5 patients and shivering during blockade in 13 patients.

CONCLUSIONS: Under high thoracic or cervico-thoracic blockades with decreased anesthetic solution doses and volumes, there have been upper limbs and pulmonary functions motor repercussions. However, according to preliminary observations and this study, spirometric changes were statistically significant, but without clinical expression in respiratory dynamics, being essentially more a consequence of intercostal nerves than of phrenic nerve paralysis.

Key Words: ANESTHESIA, Ambulatorial; ANESTHETIC TECHNIQUES, Regional: thoracic epidural

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: Sobre bloqueo peridural torácico bajo o medio, las alteraciones hemodinâmicas son fácilmente controladas. Como el bloqueo peridural torácico alto (T₂-T₃) acomete, frecuentemente, las raíces del plexo braquial (C₄)C₅-T₁(T₂), algunas de estas responsables por la formación del nervio frénico (C₃-C₄-C₅) es de suponer, posibles repercusiones motoras de este último. El presente estudio realizado en cirugías estéticas, sobre bloqueo peridural segmentar aislado en T₂-T₃ o asociado al bloqueo peridural segmentar en T₁₁-T₁₂, evaluó las repercusiones motoras en la dinámica respiratoria así como en los miembros superiores e inferiores.

MÉTODO: Treinta y dos pacientes, estado físico ASA I y II, sin molestia pulmonar broncoespástica, en actividad y peso corporal igual o superior a 50 kg, fueron sometidos a 21 bloqueos peridurales torácicos aislados en T₂-T₃ y las 11 restantes, a bloqueos peridurales torácicos en T₁₁-T₁₂, con ropivacaína a 7,5% (45 a 90 mg) asociada al sufentanil (10 a 20 µg). Repercusiones hemodinámicas, respiratorias y motoras en los miembros superiores e inferiores fueron evaluadas respectivamente, sobre monitorización no invasiva, espirometria, fuerza de preensión de la mano y escala de Bromage.

RESULTADOS: La media de duración de las cirugías mamarias fue de 105 min con depresión motora de los miembros superiores (p < 0,001), con recuperación motora aconteciendo a los 117,2 ± 51,3 min y la primera manifestación de dolor a los 485 ± 221,2 min. Las cirugías combinadas, que tuvieron una duración media de 165 min, con depresión motora de los miembros inferiores grado 1, en 40% y grado 2, en 60% de los pacientes por la escala de Bromage, cuya recuperación ocurrió 223,9 ± 57,1 min y la primera manifestación de dolor en reposo, a los 555 ± 197,9 min. Las funciones pulmonares, VEF1 (l/seg); PFE (l.min^-1); CVF (litros) se presentaron alteradas respectivamente, en 15,20% (p < 0,009); 13,36% (p < 0,029) y 18,09% (p < 0,007), con elevación de 8,75% del VEF1/CVF (p < 0,162). Hipotensión arterial (< 30 % de los valores iniciales) y bradicardia (< 55 bpm) ocurrieron en cinco pacientes y tremores durante los bloqueos, en trece pacientes.

CONCLUSIONES: Sobre bloqueo torácico alto o cérvico-torácico con dosis y volúmenes reducidos de soluciones anestésicas, ocurren repercusiones motoras en los miembros superiores y en las funciones pulmonares. Entre tanto, a juzgar por observaciones preliminares y del presente estudio, las alteraciones espirométricas fueron estadísticamente significativas, pero, sin expresión clínica en la dinámica respiratoria, siendo esencialmente decurrentes de la parálisis de los nervios intercostales, más que del nervio frénico.

INTRODUCTION

Mastectomies and thoracoplasties under thoracic epidural block were firstly performed more than 50 years ago¹. Since then, few studies on the subject have been published. In addition to Figueiredo¹, other Brazilian studies have outlined segmental epidural anesthesia with low anesthetic volumes for cervico-brachial procedures² and thoraco-abdominal plastic surgeries³. However, when segmental epidural anesthesia is not the objective, large anesthetic volumes are needed, especially for associated surgeries⁴. All authors^1-4 emphasize hemodynamic changes and have shown that these can be controlled. Thoraco-abdominal motor involvement affecting pulmonary functions, however, has only been evaluated in a small series of patients submitted to high abdominal wall surgeries with epidural blockade of the lower thoracic third (T₈-T₉)⁵. Since high thoracic epidural block often affects brachial plexus roots (C₄-C₅-T₁-T₂), some of them responsible for phrenic nerve formation (C₃-C₄-C₅), potential motor repercussions in this nerve are to be expected. Spirometric evaluations of respiratory dynamics, however, have indicated unchanged or mildly decreased pulmonary tests⁶. This study, performed with female patients submitted to cosmetic surgeries under segmental epidural block in T₂-T₃ and in T₁₁-T₁₂ with low volume of 7.5% ropivacaine plus sufentanil has objectively evaluated motor repercussions on upper (UL) and lower (LL) limbs⁷ and, indirectly, on respiratory muscles by pulmonary functions spirometric test.

METHODS

After the Institution's approval and their consent, participated in this study 32 adult female patients, physical status ASA I and II, without active bronchospastic pulmonary disease, weighing 50 kg or above in whom the behavior of epidural blocks was randomly and continuously observed in outpatient setting. Blockades were distributed in 21 isolated blockades in T₂-T₃ and the 11 remaining blockades were combined with blockades in T₁₁-T₁₂. Peripheral venous access with 18G catheter was obtained and continuous 15 to 20 mL.kg^-1 saline solution with glucose and lactated Ringer's were infused for the first 45 minutes, followed by maintenance rate to control hemodynamic stability. Noninvasive monitoring consisted of cardiac electric activity (continuous ECG with 5 electrodes placed on patients' dorsum), heart rate (bpm), systolic blood pressure (SBP), mean blood pressure (MBP), diastolic blood pressure (DBP) and hemoglobin oxygen saturation (SpO₂), and was recorded at zero, 5, 15, 30, 60, 90, 120, 150 and 180 minutes. Before anesthetic block and in the sitting position, patients were informed about spirometric and upper limb motor tests. In both cases, values obtained for the last 19 patients before (control/reference values) and 20 minutes after blockade (study values) were compared. As from a deep breathe, the following were observed for epidural blocks in T₂-T₃: a) levels of high thoracic expansion amplitude as compared to low thoracic amplitude (level 0 = deep breathe without distortions between high and low thoracic expansion; level 1 = deep breathe with mild high thoracic distortion and normal low thoracic expansion; level 2 = deep breathe with moderate high thoracic distortion and normal low thoracic expansion; level 3 = deep breathe with marked high thoracic distortion or without high thoracic expansion and mild low thoracic distortion; level 4 = apnea); b) pulmonary function with portable Enhance VMI^® spirometer (Clement Clarke International, Edinburgh); and c) upper limbs motor involvement by hand grasping an Erka^®, Germany mercury column pressure cuff previously inflated to 40 mmHg (level 0 = normal grasping; level 1 = 33% grasping decrease as compared to baseline; level 2 = 33% to 66% grasping decrease as compared to baseline; level 3 = 66% to 100% grasping decrease as compared to baseline but still with digital movements). When combined with epidural block in T₁₁-T₁₂, motor block repercussions on lower limbs, hip and inguinal region were evaluated by modified Bromage's score⁷.

All patients were submitted to segmental epidural blocks aiming at decreasing local anesthetic dose and volume, in the sitting position with lower limbs pending outside the table, feet placed on a support, head bent with chin touching the externum, forearms over thighs and shoulders supported by a nurse positioned in front of them, under level 2 sedation according to Mackenzie's sedation score⁸ with intravenous titrated midazolam (1 to 3 mg). Three non-cooperative patients were excluded due to sedation level 3. After previously blocking punctures pathway (T₂-T₃ and T₁₁-T₁₂) with 2% lidocaine, an 18G Tuohy needle was introduced by median puncture until the epidural space, identified by loss of resistance to air. While isolated blockades in T₂-T₃ aimed at mammaplasties with or without tumescent axillary and arm posterior and medial faces (T₁-T₂) liposuctions (1 epinephrine ampoule in 400 mL saline), T₁₁-T₁₂ blockades aimed at combined surgical procedures, with high abdominal liposuctions and abdominplasty or low abdominal liposuctions of trochanter (L₁-L₂) and medial thigh region (L₁-L₃). In those cases, epidural access T₁₁-T₁₂ with 18G catheter positioned in the epidural space up to 4 cm, respectively in the cephalad direction for surgeries involving higher metamers and caudally for lower metamers was prioritized. Catheter patency was tested with 1 to 2 mL anesthetic solution and before fixing it on the skin until the suprascapular region, T₂-T₃ blockade was induced. In the sequence, after dorsal placement of electrodes, patients were placed in the supine position and slightly head up < 10º while lower limbs were wrapped and raised in the "open knife" position to prevent blood retention in lower extremities and to maintain Frank-Starling reflex. Twenty minutes after and with the blockade installed, a mild 45º head up position would allow for new pulmonary test measurement. In mammary surgeries, with or without arm or axillary liposuction, single dose anesthetic solution was 7.5% ropivacaine (6 mL = 45 mg) plus sufentanil (2 mL = 10 µg), in a total volume of 8 mL and slowly administered. For associated abdominal surgeries, the volume of the same mixture has varied 12 mL to 14 mL (75 to 90 mg of 7.5% ropivacaine and 10 µg sufentanil) as a function of weight, and was administered via catheter approximately 15 minutes after surgery completion. When needed, booster doses equivalent to 50% of the initial dose were administered for longer surgeries going beyond 200 minutes. Dermatomes level and sensitivity were evaluated by the anesthesiologist through 27G needle prick during mammaplasties, every 3 minutes until final blockade installation, approximately at 20 minutes, or by the surgeon with surgical clamp on metamers involved in combined interventions. All surgeries were performed under 2 L.min^-1 oxygen flow via nasal catheter. Blockade adverse events were recorded.

RESULTS

Patients' demographics data (n = 32) and types of surgery are shown in table I.

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

Mean duration of isolated mammary surgeries or combined with arm liposuctions was 105 and 165 minutes, respectively, while mean total motor recovery was 117.2 ± 51.3 minutes (105 to 130 minutes). First pain complaint was at 485 ± 22.1 minutes (400 to 820 minutes). In combined surgeries, total lumbosacral motor recovery by Bromage's scale was 223.9 ± 57.1 minutes (198 to 327 minutes) and first pain complaint at rest at 555 ± 197.9 minutes (203 to 645 minutes). Three patients received booster dose.

Spirometric evaluations of respiratory dynamics under high thoracic epidural anesthesia are shwon below (table II).

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

Epidural block in T₂-T₃ of 29 patients (from 32 patients, 3 were excluded for non cooperation during tests) has recorded asymmetric sensory distribution as from C₈ (Figure 1). Loss of cranial sensitivity was unequal in two patients in metamers C₇ and C₆ with predominance in one side, and in 3 patients in metamers C₅ and C₄. Caudal sensory block was uniformly located in T₆-T₇.

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

In parallel, upper limbs motor block has revealed pre-blockade (125.5 ± 21.9 mmHg)/post-blockade (79.9 = 26.7 mmHg) to the right, and pre-blockade (121.34 ± 23.44 mmHg)/post-blockade (85.4 ± 26.9 mmHg) to the left, which were clinically and statistically significant (p < 0.001). Motor intensity levels by grasping score were: right hand, level 1 = 15.8% (3 patients); level 2 = 36.8% (7 patients); level 3 = 47.4% (9 patients); left hand, level 1 = 31.6% (6 patients); level 2 = 47.4% (9 patients); level 3 = 21% (4 patients) (Figures 2, 3 and Table III).

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

As a function of catheter orientation in the epidural space, cranial sensory spread of T₁₁-T₁₂ has reached or overlapped lower T₂-T₃ blockade limits and caudal spread has reached the sacral region. Epidural motor block in T₁₁-T₁₂ was evaluated by modified Bromage's scale, recording level 1 or partial in 4 patients (40%) and level 2 or semi-complete in 6 patients (60%) (Figure 3).

Oxymetry and hemodynamic parameters are shown in figures 4, 5 and 6 and table IV.

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

Brazilian Journal of Anesthesiology, 2004; 54: 4: 479 - 490

High thoracic epidural anesthesia associated or not to low thoracic epidural anesthesia

in outpatient procedures: clinical implications

Djalma Sperhacke; Karl Otto Geier; João Carlos Correia Eschiletti

Statistical Analysis

Demographics data are shown in mean, standard deviation and amplitude. Bromage scale data, epidural blocks para-effects and spirometric pulmonary functions test were expressed in relative frequencies using paired Student's t test for variables EFP, VEF1, FVC and VEF1/FVC aiming at evaluating ventilatory parameters changes.

Paired Student's t test was used for Hand Grasping scores before and after T₂-T₃ blockade, and ANOVA parametric test (Analysis of Variance) for repeated measures followed by significant minimum differences test were used to compare hemodynamic means (SBP, MBP, DBP and HR). Significance level was p < 0.05.

DISCUSSION

In Brazil, epidural block has become popular for outpatient cosmetic mammaplasties with or without sedation. Continuous propofol⁴ or midazolam⁹ with or without fentanyl are titrated to obtain sedation levels in regional anesthesia. Because the level of sleepiness is a marker to determine sedation regardless of its pharmacological etiology, Mackenzie's Sedation Score⁸ was used for midazolam. The level of ideal sedation in regional anesthetic techniques is "conscious sedation"¹⁰ or level 2⁸, especially when patient's cooperation is needed for some research tests.

Notwithstanding chest dermatomes for mammaplasties be located between T₁-T₅, there is the need to include cervical dermatome C₅, whose root also participates in the formation of the phrenic nerve. As a function of nervous fibers thickness, regional anesthesia with local anesthetics on the neuraxis is dissociative, being more cranial for b fibers (sympathetic), and more caudal for Aa fibers (motor) and, in the intermediate position, sensory fibers. Three reasons are considered for such phenomenon: 1) higher motor fibers resistance as compared to sensory fibers; 2) insufficient anesthetic solution spread to reach at least three consecutive Ranvier nodules¹¹ of motor roots located within the dural "sleeve" at intervertebral foramens level¹²; and 3) physiological susceptibility of nervous fibers to local anesthetics, as a consequence of sodium and potassium channels density and metabolic activity of ion pumps¹².

Something similar must have happened with hand motor evaluation involving radial [C₅-(T₁)], median [(C₅-T₁] and ulnar [C₇-(T₁)] nerves, and with forearm bending through the cutaneous muscle (C₅-C₇). The act of closing the hand, squeezing or not objects, as well as the ability to bend and extend the elbow, recruit the referred nerves. Grasp exerted on a pressure cuff previously inflated to 40 mmHg of a mercury column, checked before and 20 minutes after blockade installation gives quantitative information about changes in hand motor activity. In general, anesthetized dermatomes do not overlap corresponding miotomes. This is what happens with upper limbs due to peripheral brachial plexus distribution and ropivacaine's pharmacokinetics in the epidural space.

Although epidural blocks in T₂-T₃ in our study have also recorded loss of sensitivity in C₄, cranial anesthetic solution spread in the epidural space has not been uniform as from C₈ with different sensory (Figure 1) and motor (Figure 2) block levels. Cranially, as from C₇, medullary cervical widening caused by higher neural density aimed at upper limbs, results in epidural space decrease and may influence anesthetic solution spread. In addition to epidural space narrowing, there are other causes¹⁴ although there are divergences as to the role of "plica mediana dorsalis"¹⁵, which is the conjunctive band between dura and ligamentum flavum in the epidural space dividing it in one ventral and two postero-lateral compartments¹⁶. Since ropivacaine has high anesthetic dissociation as compared to bupivacaine, and especially in relation to lidocaine when added to sufentanil of intense segmental lipophylic property, it may asymmetrically impregnate the narrow cervical epidural space. Both were chosen due to these pharmacological properties to obtain good metameric anesthesia with low risk for respiratory depression as compared to hydrophilic morphine.

In addition to diaphragm, sternocleidomastoid (C₂-C₃)¹⁷, medium (C₃-C₄)¹⁷, anterior and posterior (C₅-C₈)¹⁸ scalene muscles participate in deep breathe. On the other hand, lower intercostal nerves participate on diaphragm innervation¹⁷. As a function of these uniquenesses, it is supposed that motor medullary integrity of the cervical contingent, including the phrenic nerve, in the presence of motor paralysis of all intercostal muscles, will assure respiratory continuity and vice-versa^19,20. However, cervical epidural blockade, according to some investigators^6,21, determines a certain involvement of the phrenic nerve with 25% decrease in VEF1 and 9% in PaO₂, although without clinical expression. Conversely, Wittich et al.²², inducing epidural block in C₇-T₁ with 18 mL of 0.5% bupivacaine or 1% mepivacaine, during head and neck surgeries, some of them extending to the chest for oncologic mastectomies, have observed and increase in VEF1 in patients with chronic obstructive pulmonary disease. Similarly, with tracheostomy metamers level C₃ and C₄ under epidural block in C₇-T₁, with loss of sensitivity in C₂, with 6 mL of 1.5% lidocaine, there has been no spontaneous ventilation decrease²². In this patient, "handshaking" test was normal.

Motor depression of intercostal muscles may be evaluated by coughing²⁴, by clinical observation of chest expansion during deep breathe, by magnetometry of forced chest expansion²⁵, by electromyography, by arterial blood gas analysis or spirometric test. Total pulmonary capacity is obtained with maximum inspiration and expiration as fast and intense as possible in a portable spirometer to obtain Forced Vital Capacity (FVC). Other pulmonary functions may be evaluated during this expiratory maneuver, such as Forced Expiratory Volume in the first second (FEV1) and Expiratory Flow Peak (EFP). FEV1 is more easily reproduced for being effort-dependent, but EFP is also a good indicator in the initial stage of breathing where internal intercostal muscles (T₁-T₁₁) and abdominal muscles (T₆-L₁) have active participation. According to arterial blood gas analysis and spirometric tests, high thoracic epidural block should not be the reason for respiratory distress. Although the sensation of dispnea may^5,21 or not^26,27 be a consequence of mild hypercapnia, respiratory distress referred by few patients may be a consequence of the excitation of "J" receptors of alveolar walls, as result of blood accumulation or vasodilation by thoracic sympathetic block, especially in dependent regions²⁸, or by partial blockade of respiratory muscles motor fibers with decreased respiratory dynamics, phenomenon especially observed in anxious patients.

Most of the times, hemoglobin desaturation depends on respiratory depression promoted by preanesthetic opioids or associated to epidural or spinal anesthetic solutions, changes in chest compliance²⁹, tachypnea with low tidal air volume resulting in low effective alveolar ventilation and inhaled O₂ concentration. Since patients in our study have received oxygen via nasal catheter during the procedures, values obtained were stable or slightly higher that baseline values (Figure 4). It is worth highlighting that anxiety and sedation may influence oximetry. In fact, this has been observed in some anxious and worried patients who presented tachypnea and initial oximetry values lower than intraoperative values during "conscious" sedation with midazolam.

Under lumbar epidural block, the persistence of abdominal and lower limbs motor activity is relevant during labor and hospital discharge in outpatient procedures, respectively. In our study, we have given priority to motor function in territories reached by epidural block in lower limbs by Bromage score⁷, for being more practical and doable than Van Zundert et al. Score³⁰, because according to the latter, as from the supine position, not all patients are able to bend the trunk toward lower limbs.

Muscle shivering during blockade might not have been a sign of bupivacaine toxicity, due to the low dose used, but rather a thermoregulating reflex in an attempt to maintain body temperature as opposed to heat dissipation by peripheral vasodilation of sympathetic block.

Circulatory changes promoted by high thoracic epidural anesthesia are related to sympathetic block which decreases heart rate (negative chronotropism) and contractility (negative inotropism). In relaxed volunteers, plasma catecholamine levels during different epidural blockade levels (T₈, T₄, C₈) have not recorded significant norepinephrine decrease, suggesting that chemical sympathectomy is only partial³¹ and that compensatory vasoconstriction of other territories not affected by nervous block attenuates blood pressure decrease.

Outpatient setting discharge after epidural block implies motor block recovery of affected limbs without residual instability on upper limbs. Hand motor function evaluation is also a criterium for hospital discharge. However, since there is no quantitative test for upper limbs involvement, subjective "handshaking" test was replaced by an adaptation of Bouaziz et al.'s technique³² to determine hand muscle strength. Motor control of lower limbs, responsible for orthostatic posture stability without dizziness, should allow normal ambulation without help. In parallel, the presence of spontaneous micturition, hemodynamic stability, tolerance to food intake, lack of nausea and vomiting, and postoperative analgesia complete discharge criteria³³.

Two thirds of phrenic roots partially participate on upper limbs plexus formation, especially it if is pre-fixed. Although most authors have not observed possible motor repercussions on upper limbs under high thoracic or cervico-thoracic blockades with decreased anesthetic doses and volumes, these in fact occur, as it has been quantitatively shown in this study by the pressure cuff with mercury column. However, according to preliminary observations and to this study, mild spirometric changes without clinical repercussions are observed under thoracic epidural block, being more a consequence of intercostal nerves paralysis than of phrenic nerve paralysis, resulting in respiratory dynamics preservation.

ACKNOWLEDGEMENTS

The author acknowledges the epidemiologist Tânia Hirakata and Martin Geier for their help in this study.

REFERENCES

Submitted for publication July 21, 2003

Accepted for publication November 06, 2003

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*

Received from Clínica Rio Branco de Porto Alegre, RS

Publication Dates

• Publication in this collection
  22 Sept 2004
• Date of issue
  Aug 2004

History

• Received
  21 July 2003
• Accepted
  06 Nov 2003