CLINICAL REPORT

 

Paresthesia at the median nerve territory: adverse effect of the peripheral nerve stimulator? Case report^*

 

Parestesia en el territorio del nervio mediano: efecto adverso del estimulador de nervio periférico?  Relato de caso

 

 

Carlos Henrique Viana de Castro, TSA, M.D.^I; Giovanni Menezes Santos, M.D.^I; Niwton Carlos Toledo, TSA, M.D.^II; José Roberto de Rezende Costa, TSA, M.D.^III

^IEspecialista em Terapia Intensiva e Clínica Médica
^IILegista, pós-graduado em Auditoria Médica pela Fundação Educacional Lucas Machado, Faculdade de Ciências Médicas de Minas Gerais
^IIILegista, pós-graduado pelo Instituto de Ciências Biológicas da UFMG em Farmacologia Cardiovascular

Correspondence

 

 

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SUMMARY

BACKGROUND AND OBJECTIVES: Anesthesiology is developing and improving techniques, drugs and equipment, especially monitoring devices. The peripheral nerve stimulator has been used to adequately evaluate muscle relaxation and recovery. This report aimed at showing that, although the importance of modern monitoring, it may sometimes not be innocuous, thus generating suspicion about its supposedly lack of side-effects.
CASE REPORT: A fifty-six year-old woman was submitted to cosmetic mammaplasty. Her previous history included: diabetes mellitus, hypothyroidism, hypertension and obesity, all under good clinical control, and with no previous anesthetic complications. Surgery was performed without intercurrences and at the end patient was transferred to PACU. Before being discharged, patient complained of severe paresthesia exactly on the territory of the median nerve where the peripheral nerve stimulator had been placed. This complaint disappeared after 48 h and patient was discharged in good conditions.
CONCLUSIONS: Monitoring with peripheral nerve stimulator is important and should be recommended. For such, one must adequately fix and position the limb. However, such position may, in some cases, lead to neurological complications compatible with postoperative nervous compression. So, one must be alert to differential diagnosis and, in our case, it seems that the adverse effect was not caused by the nerve stimulator but by the positioning of the left upper limb.

Key words: COMPLICATIONS, Neurological: paresthesia; EQUIPMENTS: nerve stimulator

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RESUMEN

JUSTIFICATIVA Y OBJETIVOS: La Anestesiologia se ha desenvuelto continuamente y viene sucesivamente mejorando sus técnicas, fármacos, bien como sus equipamientos, especialmente aquellos para monitorización. De entre éstos, el estimulador de nervio periférico se destaca para evaluación adecuada del nivel de relajamiento neuromuscular y su recuperación. Se objetivó mostrar en este relato que, aun cuando la monitorización moderna sea importante, por veces, puede no ser innocua, generando sospechas sobre su supuesta ausencia de efectos adversos.
RELATO DO CASO: Una paciente de 56 años fue sometida a cirugía estética mamaria. Sus antecedentes contenían relato de diabetes mellitus, hipotiroidismo, hipertensión arterial, dislipidemia y obesidad, todos con buen control clínico, medicamentoso y laboratorial, sin mención de complicaciones anestésicas en cirugías anteriores. El procedimiento transcurrió sin interocurrencias y a su término, la paciente fue encaminada a la sala de recuperación pós-anestésica. En ésta, antes de recibir alta, presentó queja importante de parestesia en el territorio del nervio mediano de la mano izquierda, o sea, exactamente en el local donde quedó el estimulador de nervio periférico. Tal queja se redució en las próximas 48 horas, habiendo recibido la paciente alta hospitalar, sin otros problemas o alteraciones del examen físico.
CONCLUSIONES: La monitorización con el estimulador de nervio periférico es importante y debe ser preconizada. Para tanto, se debe fijar y posicionar el miembro adecuadamente. No obstante, esta posición puede, en algunos casos, traer cuadros neurológicos compatibles con compresiones nerviosas agudas, en el pós-operatorio. De esta forma, se debe atentar para diagnósticos diferenciales y, en este caso, el efecto adverso posiblemente no fue ocasionado pelo estimulador de nervio y, si, por el posicionamiento del miembro superior izquierdo.

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INTRODUCTION

Anesthesia monitoring is being continuously developed with the introduction of new monitors immediately added to the clinical practice and allowing for an accurate reading and interpretation of clinical data. This is the case of the peripheral nerve stimulator (PNS) the use of which is not confined to operating rooms but has reached Intensive Care Units (ICU) where it allowed for better neuromuscular blocker (NMB) administration, thus reducing cost and side-effects ^1,2. In anesthesia, the use of PNS is justified by NMB pharmacodynamic variations and, especially to analyze muscle relaxation recovery. Baillard has recently shown a 42% incidence of TOF lower than 0.7 in the Post Anesthetic Recovery Unit (PACU), even with intermediary action NMBs ³. Although the benefits of modern monitoring, one must pay attention to their side-effects.

This study aimed at reporting a carpal tunnel syndrome case where paresthesia on the median nerve territory has been triggered by patient's hand positioning, supposedly as a function of PNS.

 

CASE REPORT

A patient 56 years of age old was admitted for mammary prosthesis and correction of left breast scar. Her medical history showed diabetes mellitus under pioglitazone; hypothyroidism treated with L-tiroxine with good clinical and laboratorial control; obesity; hypertension under candesartan and propanolol; dyslipidemia treated with gamfibrosil. Ergonomic test has not shown ischemic alterations and ECG has only revealed abnormal diastolic relaxation. Other hematological and biochemical tests were normal.

Her surgical history was: appendicectomy, tonsillectomy, partial hysterectomy and mammaplasty. The first three surgeries evolved without intercurrences and the last presented a complication by abscess formation.

Physical evaluation revealed: BP - 110/70 mmHg; HR - 68 bpm; height - 161 cm; weight - 84 kg; body mass index - 32.6. Remaining physical tests had no major changes. In the operating room patient was premedicated with 3 mg intravenous midazolam and general anesthesia was induced. Monitoring consisted of ECG, pulse oximetry, capnography, halogenate gases analyzer, peripheral nerve stimulator (PNS) on the left upper limb (Figures 1a and 1b) and right upper limb noninvasive blood pressure.

Induction was then performed with propofol (2 mg.kg^-1), rocuronium (0.6 mg.kg^-1), fentanyl (3 µg.kg^-1) and, after lack of response to simple stimulus at PNS, tracheal intubation was performed with an endotracheal tube size 7.5. Apart from lasting 4.30 hours, surgery was performed without abnormalities.

After surgery the patient awakened, was extubated without problems and sent to the PACU where she remained for 70 minutes. Before PACU discharge, she complained of paresthesia on the left hand median nerve territory. An orthopedist was requested and identified normal radial and ulnar pulses and positive Phalen test. Paresthesia was progressively reduced along 48 hours. Patient was discharged without complaints.

 

DISCUSSION

Carpal tunnel syndrome is a consequence of the compression of the median nerve in the carpal tunnel. It appears in patients 30 to 60 years of age and is five times more frequent in women. Systemic factors associated to carpal tunnel syndrome are: obesity, hypothyroidism, diabetes mellitus, amyloidosis and Raynaud's disease. On the other hand, local factors, such as edema, infection, tumors and nodes, contribute to the limitation of the carpal tunnel space. When symptoms appear during pregnancy, they often disappear after delivery. Occasionally, symptoms may be triggered by an inadequate positioning of the fist during sleep, which is a situation close to our case report because a inadequate position for a prolonged period may have triggered the clinical event. Paresthesia in the median nerve sensory distribution is the most frequent carpal tunnel syndrome symptom. Tinel signal, median nerve percussion on the fist and fist flexion for 60 seconds (Phalen and Inverted Phalen Test) may trigger paresthesia. Gellman et al.⁴ have evaluated carpal tunnel pressures in patients with carpal tunnel syndrome in the neutral position - 90-degree flexion and extension - and have recorded 32 mmHg, 99 mmHg and 110 mmHg, respectively, while control group pressures (without carpal tunnel syndrome) were 25 mmHg in the neutral position, 31 mmHg for flexion and 30 mmHg for extension of the fist. Carpal tunnel syndrome management varies with the severity of symptoms and may range from drugs to surgical decompression.

PNS is a device which is being increasingly used and should be recommended in the presence of NMBs. To accurately interpret stimuli, patient's hands should be accurately positioned and fixed so that movements of other muscle groups will not interfere with the readings (Figures 1a and 1b). However, a vicious position in susceptible patients may trigger acute nervous compression leading to a postoperative neurological event. It is possible that the side-effect described had no direct relationship with PNS electrical stimulus, but being caused by the patient's hand positioning and would be triggered even without the device.

 

REFERENCES

01. Rudis MI, Sikora CA, Angus E et al - A prospective, randomized, controlled evaluation of peripheral nerve stimulation versus standard clinical dosing of neuromuscular blocking agents in critically ill patients. Crit Care Med, 1997;25:575-583.         [ Links ]

02. Zarowitz BJ, Rudis MI, Lai K et al - Retrospective pharmaco-e conomic evaluation of dosing vecuronium by peripheral nerve stimulation versus standard clinical assessment in critically ill patients. Pharmacotherapy, 1997;17:327-332.         [ Links ]

03. Baillard C, Gehan G, Reboul-Marty J et al - Residual curarization the recovery room after vecuronium Br J Anaesth, 2000;84: 394-395.         [ Links ]

04. Jobe MT, Wright PE - Peripheral Nerve Injuries em Cannale: Campbell's Operative Orthopaedics, 9^th Ed, Mosby, 1998; 3685-3692.         [ Links ]

 

 

Correspondence to:
Dr. Carlos Henrique Viana de Castro
Address: Rua do Mosteiro, 37/701 - Vila Paris
ZIP: 30380-780 City: Belo Horizonte, Brazil

Submitted for publication December 7, 2000
Accepted for publication March 12, 2001

 

 

* Received from Hospital Mater Dei, Belo Horizonte, MG