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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094

Rev. Bras. Anestesiol. vol.58 no.2 Campinas Mar./Apr. 2008

http://dx.doi.org/10.1590/S0034-70942008000200008 

CLINICAL REPORT

 

Accidental subarachnoid administration of 4 mg of morphine. Case report

 

Administración inadvertida de 4 mg de morfina por vía subaracnoidea. Relato de caso

 

 

Bruno Salomé de Morais, TSAI; Yerkes Pereira SilvaII; Marcos Guilherme C. Cruvinel, TSAI; Carlos Henrique Viana de Castro, TSAI; Marco Victor HermetoIII

IAnestesiologista do Hospital Lifecenter
IIAnestesiologista do Hospital Lifecenter; Mestre e Doutor em Pediatria pela UFMG
IIIIntensivista do Hospital Lifecenter

Correspondence to

 

 


SUMMARY

BACKGROUND AND OBJECTIVES: The subarachnoid administration of morphine is a well-established anesthetic technique of postoperative analgesia due to its efficacy, safety and low cost. The objective of this paper was to report the accidental subarachnoid administration of 4 mg of morphine complicated by atrial fibrillation after administration of naloxone.
CASE REPORT: A 45-year old male patient with 75 kg, 1.72 m, physical status ASA II, hypertensive, was scheduled for reconstruction of the anterior cruciate ligament of the left knee. After spinal anesthesia, it was noticed that the vial of morphine had been changed resulting in the accidental subarachnoid administration of 4 mg of morphine (0.4 mL of the 10 mg vial). Respiratory rate varied from 12 to 16 bpm and the patient remained hemodynamically stable without intraoperative complaints. Thirty minutes after admission to the post-anesthesia recovery unit the patient developed vomiting and diaphoresis being treated with 0.4 mg of naloxone followed by continuous infusion of 0.2 mg.h-1 until the symptoms had subsided. Continuous naloxone infusion was maintained in the Intensive Care Unit (ICU), where blood pressure, heart rate, respiratory rate and oxygen saturation were monitored as well as the presence of nausea, pruritus, vomiting, sedation, pain and urinary retention. Two hours after arriving at the ICU the patient developed acute atrial fibrillation without hemodynamic instability. Sinus rhythm was reestablished after the administration of 150 mg of amiodarone and discontinuation of the naloxone infusion. During the following 18 hours the patient remained hemodynamically stable and did not experience any other intercurrence until his discharge from the hospital.
CONCLUSIONS: The present report is an alert for the risk of inadvertently switching of drugs during anesthesia, stressing the importance of referring patients being treated for opiate overdose to the ICU, due to the potential adverse reactions.

Key Words: ANALGESICS: morphine; ANESTHETIC TECHNIQUE, Regional: subarachnoid; COMPLICATIONS: accidental injection, atrial fibrillation.


RESUMEN

JUSTIFICATIVA Y OBJETIVOS: La administración de morfina por vía subaracnoidea es la técnica bien establecida para la analgesia postoperatoria debido a su eficacia, seguridad y bajo costo. La administración inadvertida de 4 mg de morfina por vía subaracnoidea complicada por fibrilación atrial después de la administración de naloxona fue el objetivo de este relato.
RELATO DEL CASO: Paciente del sexo masculino, 45 años, 75 kg, 1,72 m, estado físico ASA II, hipertenso, a ser sometido a la reconstrucción del ligamento cruzado anterior de la rodilla izquierda. Después de la realización de la raquianestesia, fue constatado cambio de la ampolla de morfina, con administración de 4 mg (0,4 mL de la ampolla de 10 mg) por vía subaracnoidea. La frecuencia respiratoria osciló entre 12 y 16 incursiones respiratorias por minuto y el paciente se mantuvo estable hemodinámicamente sin quejarse en el intraoperatorio. Después de 30 minutos de la admisión en la SRPA, presentó vómitos y sudor, tratados con 0,4 mg de naloxona seguidos de infusión continua de 0,2 mg.h-1 hasta el desaparecimiento de los síntomas. La infusión continua de naloxona se mantuvo en la Unidad de Cuidados Intensivos (UCI), donde la presión arterial, frecuencia cardíaca, frecuencia respiratoria, saturación de oxígeno se monitorearon. También se comprobó la presencia de náusea, prurito, vómito, sedación, dolor y retención urinaria. Después de 2 horas de admisión en la UCI, el paciente presentó fibrilación atrial aguda sin inestabilidad hemodinámica. El ritmo sinusal fue reestablecido después de 150 mg de amiodarona e interrupción de la infusión de naloxona. En las 18 horas siguientes presentó estabilidad hemodinámica y evolucionó sin otras intercurrencias hasta su alta.
CONCLUSIONES: El presente relato nos avisa sobre el riesgo del cambio de medicamentos durante la anestesia y resalta la importancia del envío de los pacientes en tratamiento de sobredosis de opioides a la UCI a causa de sus potenciales efectos adversos.


 

 

INTRODUCTION

The subarachnoid administration of morphine is a well-establish technique of postoperative analgesia due to its efficacy, safety and low cost being widely used for surgeries in the lower limbs and abdomen 1-4.

The objective of this report was to present a case of accidental subarachnoid administration of 4 mg of morphine during reconstruction of the anterior cruciate ligament, which was complicated by atrial fibrillation after the administration of naloxone.

 

CASE REPORT

A 45-year old patient weighing 75 kg, 1.72 m, physical status ASA II, with hypertension treated with losartan was scheduled for reconstruction of the anterior cruciate ligament of the left knee. After venipuncture with a 20G Teflon® catheter and institution of monitoring with electrocardiogram (ECG) (DII and V5 derivations), pulse oximetry and non-invasive automatic blood pressure, the patient received 100 µg of fentanyl, 2 mg of midazolam, 2 g of cephalothin and 10 mg of dexamethasone intravenously. Ten milligrams of 0.5% hyperbaric bupivacaine and 80 µg of morphine were prepared for the spinal anesthesia using 3 and 1 mL syringes, respectively. The patient was placed in left lateral decubitus (LLD), the area was cleaned with 70% alcohol and the skin was infiltrated with 50 mg of 1% lidocaine using a 13 x 4.5 mm needle. A 27G Withacre needle was used for the subarachnoid puncture, done at the L3-L4 level and the solution containing bupivacaine and morphine was injected slowly. The patient remained in LLD for 15 minutes and afterwards was placed in dorsal decubitus for the surgery. The vials were then checked and it was verified that the vial of morphine had been switched, with the inadvertent subarachnoid administration of 4 mg of morphine (0.4 mL of the 10 mg vial) instead of 80 µg (0.4 mL of the 200 µg vial). The respiratory rate (RR) of the patient varied from 12 to 16 breaths per minute and he remained hemodynamically stable without intraoperative complaints (150 minutes). At the end of the procedure, 4 mg of ondansetron were administered and he was transferred to the post-anesthesia recovery unit (PACU) where he was monitored with continuous ECG, pulse oximeter, non-invasive blood pressure and respiratory frequency monitor. Thirty minutes after admission to the PACU the patient developed vomiting and diaphoresis being treated with 0.4 mg of naloxone followed by the continuous infusion of this drug at 0.1 mg.h-1, which was adjusted to 0.2 mg.h-1 until resolution of the symptoms. Ninety minutes after admission to the PACU the patient was transferred to the ICU and blood pressure, respiratory rate and oxygen saturation were monitored and he was also observed for the development of nausea, pruritus, vomiting, sedation, pain and urinary retention. Two hours after arriving at the ICU the patient developed acute atrial fibrillation (AF), which was not associated with hemodynamic instability. Normal sinus rhythm was reestablished after the administration of 150 mg of amiodarone and discontinuation of the infusion of naloxone. The patient remained hemodynamically stable during the following 18 hours and in the morning he was transferred for a private room. During this period, he complained of pain (6 in a verbal pain scale from 0-10), vomiting and urinary retention, which were treated with a non-hormonal anti-inflammatory drug, ondansetron and bladder catheterization, respectively. After this period he remained asymptomatic until being discharged from the hospital.

 

DISCUSSION

Some cases of opioid overdose with the subarachnoid injection of this drug have been described and most occurred during the treatment of chronic pain in which tolerance is a well-known effect 5-8. There are very few reports on overdose in the perioperative period 9-10.

Accidental subarachnoid morphine overdose under different circumstances has been reported, including inadvertent puncture of the dura mater during spinal puncture, catheter migration and change of vials, with doses varying from 0.06 to 450 mg 6,9. In the case reported here a grave mistake was done, i.e., the vial opened by the assisting nurse was not checked. The vial was misplaced in the drawer where the 200 µg.mL-1 vials are stored. The accident could have been prevented by double checking the medication.

Depending on the route of administration, excessive doses of morphine can cause several complications such as hypothermia, nausea, vomiting, pruritus, urinary retention, seizures, pulmonary edema, respiratory depression, coma and death 11-13.

Several treatments for subarachnoid opioid overdose have been described, like drainage of the cerebrospinal fluid, intravenous infusion of naloxone and ventilatory support. In the case reported here, infusion of 0.2 mg.h-1 of naloxone was enough to control the undesirable effects of morphine.

Naloxone is a competitive antagonist of opioid receptors without agonist action, being a good option for the treatment of morphine overdose. Due to its short duration of action (30 to 45 minutes), repeated doses or continuous infusion are recommended whenever a lasting antagonism is necessary 14,15. Despite antagonizing the adverse effects of opioids, infusion of naloxone is associated with hypertension, cardiac arrhythmias and pulmonary edema, which are related with the sudden increase in sympathetic tonus 16-18.

The patient developed atrial fibrillation (AF) without hemodynamic repercussions approximately three hours after the institution of naloxone infusion, which was discontinued immediately and normal sinus rhythm was reestablished after the administration of amiodarone. Naloxone should be administered parsimoniously, at the smallest dose necessary to reverse the undesirable effects of opioids. Infusion of up to 5 µg.kg.h-1 of naloxone is recommended for the prevention of respiratory depression without affecting the analgesia produced by the neuroaxial administration of opioids 14. Even receiving small doses (3 µg.kg.h-1), the patient developed AF. After discontinuation of the infusion, the patient did not have further episodes of AF despite the development of pain, vomiting and urinary retention, which were properly treated.

The present report alerts anesthesiologists for the risk of accidental change of the medication during anesthesia and emphasizes the importance of referring patients treated for opioid overdose to the ICU due to the potential side effects.

 

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Correspondence to
Dr. Bruno Salomé de Morais
Rua Donato da Fonseca, 212/102 – Coração de Jesus
30380-260 Belo Horizonte, MG
E-mail: brunomoraisanest@yahoo.com.br

Submitted em 29 de março de 2007
Accepted para publicação em 26 de dezembro de 2007

 

 

* Received from Departamento de Anestesiologia do Hospital Lifecenter, Belo Horizonte, MG