TY  - CHAP
M1  - Book, Section
TI  - Case Study 5
A1  - Hoffman, Robert S.
A1  - Howland, Mary Ann
A1  - Lewin, Neal A.
A1  - Nelson, Lewis S.
A1  - Goldfrank, Lewis R.
Y1  - 2015
N1  - 
T2  - Goldfrank's Toxicologic Emergencies, 10e
AB  - HistoryA  54  year-old  man  presented  to  the  emergency  department  (ED)  complaining  that  he  was  weak  and  dizzy  and  felt  as  if  he  was  about  to  pass  out.  His  past  medical  history  was  significant  for  opioid  dependence.  He  recently  saw  an  alternative  medical  provider  and  was  given  a  natural  remedy  to  help  him  detoxify.  Prior  to  therapy,  he  was  on  daily  methadone,  but  transitioned  to  hydrocodone  in  preparation  for  treatment.  He  was  treated  by  his  provider  approximately  3  to  4  hours  before  presentation  and  sent  to  the  ED  because  he  was  unwell.  He  denied  nausea,  vomiting,  diarrhea,  lacrimation,  or  other  symptoms  consistent  with  opioid  withdrawal.  In  triage,  his  pulse  was  35  beats/min,  so  the  patient  was  rushed  to  the  critical  care  area.Immediate  Assessment  and  ManagementOn  arrival  to  the  critical  care  area  he  was  awake  but  complaining  of  weakness.  Vital  signs  were:  blood  pressure,  128/62  mm  Hg;  pulse,  35  beats/min,  respiratory  rate,  14  breaths/min;  temperature,  98.4°F  (36.9°C);  oxygen  saturation,  98%  on  room  air;  and  glucose,  110  mg/dL.  A  general  physical  examination  was  unremarkable  and  specifically  noted  the  absence  of  mydriasis,  piloerection,  rhinorrhea,  or  lacrimation.  An  electrocardiogram  (ECG)  was  obtained  (Fig.  CS5–1),  which  was  notable  for  sinus  bradycardia  with  a  QT  interval  of  approximately  600  msec  and  an  abnormally  shaped  T  wave.  Blood  was  sent  for  a  complete  blood  count  and  electrolytes.  The  patient  was  attached  to  continuous  cardiac  monitoring.Suddenly,  the  patient  lost  consciousness  and  became  pulseless.  A  rhythm  strip  captured  the  event  (Fig.  CS5–2),  which  was  determined  to  be  torsade  de  pointes  (TdP)  (Chap.  16).  The  event  was  self-limited  but  recurred,  at  which  time  he  was  given  2  g  of  magnesium  sulfate  intravenously  followed  by  a  continuous  magnesium  infusion  at  1  g/h.  His  cardiac  rhythm  returned  to  sinus,  and  he  was  moved  to  the  cardiac  intensive  care  unit  (CCU)  where  a  temporary  transvenous  pacemaker  was  inserted.What  Is  the  Differential  Diagnosis?In  addition  to  congenital  and  acquired  intrinsic  cardiac  conditions  and  electrolyte  abnormalities  (Chap.  19),  numerous  xenobiotics  from  diverse  chemical  classes  are  associated  with  QT  interval  prolongation  and  the  risk  of  TdP.  These  xenobiotics,  which  typically  share  an  ability  to  block  myocardial  potassium  channels  (Chap.  16),  can  be  found  throughout  this  text.  Common  classes  of  xenobiotics  in  which  some  members  are  associated  with  QT  interval  prolongation  and  some  specific  examples  are  listed  in  Table  CS5–1.  Readers  are  referred  to  www.crediblemeds.com,  a  comprehensive  Web  site  that  stratifies  pharmaceuticals  by  risk.  It  is  noteworthy  that  many  nonpharmaceutical  xenobiotics  also  are  listed  in  the  table  and  text.What  Rapid  Clinical  and  Laboratory  Analyses  Can  Help  Determine  the  Etiology  and  Guide  Therapy  for  This  Patient's  Presentation?Because  the  differential  diagnosis  is  so  extensive,  broad  laboratory  testing  is  not  advocated  to  determine  the  etiology  in  patients  with  unclear  causes  for  QT  interval  prolongation.  Instead,  efforts  should  be  directed  at  thorough  history  taking,  as  the  cause  may  become  evident.  Patients  should  have  routine  electrolytes  measured,  because  hypokalemia,  hypocalcemia,  and  hypomagnesemia  can  all  either  be  the  primary  cause  of  QT  interval  prolongation  or  be  contributory  when  another  etiology  exists.  Since  these  electrolyte  abnormalities  can  be  ...
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/19
UR  - accesspharmacy.mhmedical.com/content.aspx?aid=1108439022
ER  -