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Prevalence of Malignant Hyperthermia Diagnosis in New York State Ambulatory Surgery Center Discharge Records 2002 to 2011

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Background: Malignant hyperthermia (MH) is a rare yet potentially fatal pharmacogenetic disorder triggered by exposure to inhaled anesthetics and the depolarizing neuromuscular blocking drug succinylcholine. Epidemiologic research on MH is largely limited to inpatients. In this study, we examined the prevalence of recorded MH diagnosis in patients discharged from ambulatory surgery centers (ASCs). Methods: We analyzed the New York State Ambulatory Surgery Dataset for the years 2002 to 2011 and identified patients with a discharge diagnosis of MH due to anesthesia by using the International Classification of Disease, Ninth Revision, Clinical Modification code 995.86. MH prevalence was assessed by demographic, clinical, and ASC characteristics. Results: During the study period, 31 of 17,092,765 discharges from ASCs had a recorded diagnosis of MH, yielding a prevalence of 0.18 per 100,000 discharges (95% confidence interval, 0.12-0.25). The prevalence of recorded MH diagnosis per discharge differed significantly across age groups and surgical procedure categories. All patients with a recorded diagnosis of MH were from hospital-based ASCs and were discharged alive from ASCs. Conclusions: The prevalence of recorded MH diagnosis in ASC patients is approximately 1 per 500,000 and varies considerably with surgical procedures.
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February 2016 Volume 122 Number 2 www.anesthesia-analgesia.org 449
Copyright © 2015 International Anesthesia Research Society
DOI: 10.1213/ANE.0000000000001054
Malignant hyperthermia (MH) is an autosomal-
dominant genetic disorder of the skeletal muscle,
linked to ryanodine receptor (RYR1) gene muta-
tions.1 This pharmacogenetic clinical syndrome is triggered
by sensitivity to volatile inhaled anesthetic gases (e.g., sevo-
urane, desurane, isourane) and the depolarizing neuro-
muscular blocking drug succinylcholine, leading to skeletal
muscle hypermetabolism.2 Epidemiologic data on MH are
scant. The prevalence of MH due to anesthesia in surgical
patients treated in New York State hospitals is estimated to
be approximately 1 per 100,000.3 There is little information
about the prevalence of MH in patients treated in the ambu-
latory care setting.
Since the early 1980s advances in medical technol-
ogy, the changes in payment arrangements and increasing
health care costs have contributed to the increase of ambu-
latory surgery centers (ASCs) in the United States.4 ASCs
are health care facilities that provide same-day surgical care
outside the hospital setting, including diagnostic and pre-
ventive procedures. They are considered to be more practi-
cal and generally less expensive than hospitals.4 According
to the National Center for Health Statistics of the Centers
for Disease Control and Prevention, in 2010, ambulatory
surgery cases totaled 18.7 million, accounting for 63.6%
of all surgical procedures.5 From 1996 to 2006, the rate of
visits to freestanding ASCs tripled, whereas the rate in hos-
pital-based ASCs remained unchanged.4 According to the
Healthcare Cost and Utilization Project (HCUP), the num-
ber of ASCs increased from 336 in 1985 to 6167 in 2008.6 To
ensure patient safety in ambulatory care settings, it is neces-
sary to better understand the epidemiology of MH in ASCs.7
The purpose of this study was to estimate the prevalence of
MH diagnosis and characterize factors associated with MH
diagnosis recorded in a large sample of ASC discharges.
METHODS
This study meets the criteria for the Protection of Human
Subjects exemption 4 (research involving preexisting data)
of the United States Code of Federal Regulations (45 CFR
46.101). The study was deemed exempt from review by the
IRB’s Administrative Review Committee at the Columbia
University Medical Center (New York, NY).
Data Source
Data for this study came from HCUP State Ambulatory
Surgery Databases (SASD) for New York State from 2002 to
2011. SASD contains the New York State’s ambulatory sur-
gery discharge records, including abstracts from hospital-
owned ASCs and nonhospital-owned freestanding ASC
facilities.6 A facility is considered hospital based if any 1 of
the 3 criteria is met6: (1) an American Hospital Association
(AHA) hospital identier can be determined; (2) the facility
provides inpatient data to the HCUP project, but no AHA
hospital identier can be determined; and (3) documentation
BACKGROUND: Malignant hyperthermia (MH) is a rare yet potentially fatal pharmacogenetic dis-
order triggered by exposure to inhaled anesthetics and the depolarizing neuromuscular blocking
drug succinylcholine. Epidemiologic research on MH is largely limited to inpatients. In this study,
we examined the prevalence of recorded MH diagnosis in patients discharged from ambulatory
surgery centers (ASCs).
METHODS: We analyzed the New York State Ambulatory Surger y Dataset for the years 2002 to
2011 and identied patients with a discharge diagnosis of MH due to anesthesia by using the
International Classification of Disease, Ninth Revision, Clinical Modication code 995.86. MH
prevalence was assessed by demographic, clinical, and ASC characteristics.
RESULTS: During the study period, 31 of 17,092,765 discharges from ASCs had a recorded
diagnosis of MH, yielding a prevalence of 0.18 per 100,000 discharges (95% condence inter-
val, 0.12–0.25). The prevalence of recorded MH diagnosis per discharge differed signicantly
across age groups and surgical procedure categories. All patients with a recorded diagnosis of
MH were from hospital-based ASCs and were discharged alive from ASCs.
CONCLUSIONS: The prevalence of recorded MH diagnosis in ASC patients is approximately 1 per
500,000 and varies considerably with surgical procedures. (Anesth Analg 2016;122:449–53)
Prevalence of Malignant Hyperthermia Diagnosis in
New York State Ambulatory Surgery Center Discharge
Records 2002 to 2011
Zhen Lu, MPH,* Henry Rosenberg, MD, Joanne E. Brady, PhD,* and Guohua Li, MD, DrPH*‡
From the *Department of Epidemiology, Columbia University Mailman
School of Public Health, New York, New York; Department of Medical
Education and Clinical Research, Saint Barnabas Medical Center, Livingston,
New Jersey; and Department of Anesthesiology, Columbia University
College of Physicians and Surgeons, New York, New York.
Accepted for publication September 8, 2015.
Funding: This study was supported in part by the Malignant Hyperthermia
Association of the United States, Sherburne, NY, and by Grant 1 R49 CE002096
from the National Center for Injury Prevention and Control, Centers for
Disease Control and Prevention to the Center for Injury Epidemiology and
Prevention at Columbia University. Its contents are solely the responsibil-
ity of the authors and do not necessarily represent the ofcial views of the
Centers for Disease Control and Prevention.
Conict of Interest: See Disclosures at the end of the article.
Reprints will not be available from the authors.
Address correspondence to Guohua Li, MD, DrPH, Department of Anesthe-
siology, Columbia University College of Physicians and Surgeons, 622 West
168th St., PH5-505, New York, NY 10032. Address e-mail to GL2240@cumc.
columbia.edu.
Copyright © 2015 International Anesthesia Research Society. Unauthorized reproduction of this article is prohibited.
Malignant Hyperthermia in Ambulatory Surgery
450 www.anesthesia-analgesia.org ANESTHESIA & ANALGESIA
provided by the data source clearly indicates the facility is
hospital based. An AHA hospital identier cannot always
be determined for hospital-based facilities because hospi-
tals may not be matched to the AHA. The SASD database
contains clinical and nonclinical information on all patients
including patient diagnoses and procedures, admission
and discharge status, patient demographics (e.g., gender,
age, and race), payment source (Medicare, Medicaid, pri-
vate insurance, and uninsured), and some hospital char-
acteristics. HCUP state databases are discharge-level (not
patient) les in which each record represents 1 ambula-
tory surgical visit. The Agency for Healthcare Research
and Quality aggregates International Classication of Disease,
Ninth Revision, Clinical Modication (ICD-9-CM) diag-
nostic coding into meaningful clinical groups: the Clinical
Classication Software (CCS) codes.8 According to HCUP,
the record selection criteria for ambulatory surgery dis-
charges varied from 2009 to 2011, resulting in uctuation in
record counts in these years.a
Study Sample
The study sample consisted of all ASC discharges in New
York State from 2002 through 2011. MH cases were identi-
ed by screening all the discharge diagnoses using the ICD-
9-CM code 995.86 to indicate MH due to anesthesia.
Statistical Analysis
The prevalence of MH due to anesthesia was calculated
based on all ASC discharges in SASD from 2002 to 2011.
MH prevalence was examined according to patient char-
acteristics including age, sex, payment type, exposure to
anesthesia, and comorbid conditions. Comorbidities were
identied by applying the Charlson Comorbidity Score to
ICD-9-CM codes in the data sets.9,10 We calculated the prev-
alence of MH for 5-year intervals and examined trends in
MH prevalence from 2002 to 2011 and also calculated the
95% condence intervals (CIs) using the normal approxima-
tion method.11 Comparisons of prevalence among different
patient groups were performed with SAS version 9.4 (SAS
Institute, Cary, NC); and χ2 or Fisher exact test was used
to compare categorical variables. Statistical signicance was
dened as P < 0.05.
RESULTS
Prevalence
The SASD database for 2002 to 2011 contained 17,092,765
ASC discharge records; of them, 31 had an MH diagnosis.
The overall prevalence of MH was 0.18 (95% CI, 0.12–0.25)
per 100,000 discharges (Table 1). The difference in MH prev-
alence across all groups of exposure to anesthesia, including
exposure to no anesthesia, was not statistically signicant
(P = 0.065; Table 1). However, the prevalence of MH for
patients who received general anesthesia was 2.5 times (95%
CI, 1.12–5.56, P = 0.025) the prevalence for those receiving
other anesthesia including local and regional anesthesia
(Table 1). The estimated prevalence of MH diagnosis per
100,000 discharges increased from 0.11 (95% CI, 0.03–0.18)
in 2002 to 2006 to 0.24 (95% CI, 0.14–0.34) in 2007 to 2011 (P
= 0.001; Table 1). The difference in MH prevalence between
sexes was not statistically signicant (P = 0.76; Table 1).
Through cross-referencing revisit les (except for 2002
SASD that was unavailable) and other discharge variables
such as race, birth year, and birth month, all 31 patients with
a diagnosis of MH were deemed unique individual patients.
Based on revisit les of 2009 to 2011, 28.5% of ASC patients
had repeat visits within 3 years.
Characteristics of MH Cases
Of the 31 patients with a diagnosis of MH, 53.6% were
younger than 45 years, 88.0% were Caucasian, and 55.0%
were male (Table1). All of the patients with a diagnosis of
MH were discharged to home or self-care with the excep-
tion of 1 patient being transferred to a short-term hospital.
Based on the Charlson-Deyo Comorbidity Score 1, 26.0% of
the MH patients had at least 1 signicant preexisting medi-
cal condition. Of 31 MH patients, 50.0% received general
anesthesia, whereas 33.0% received administration of other
anesthesia, such as local and regional anesthesia (Table 1).
More than half of those with an MH diagnosis had private
insurance as the primary payer for receiving medical ser-
vices from ASCs, whereas approximately 39.0% of those
diagnosed as MH susceptible were covered by Medicare
and Medicaid (Table 1). All 31 patients with a diagnosis of
MH were alive at the time of discharge from the ASCs. All
patients diagnosed with MH were recorded in discharges
from hospital-based ASCs. Based on the CCS codes, the dif-
ference in MH prevalence across all diagnosis categories
was not statistically signicant (P=0.68; Table2). The MH
prevalence per discharge differed signicantly across all
CCS surgery categories (P= 0.01), with the highest preva-
lence (1.66 per 100,000 discharges; 95% CI, 0.00–3.39) being
found in surgeries of the ear, such as tympanoplasty, myrin-
gotomy, and mastoidectomy (Fig.1).
Ambulatory Services
The number of freestanding ASCs in New York State
increased almost threefold within 10 years, whereas the
number of hospital-based ASCs remained unchanged
(Fig.2). Furthermore, the number of surgical visits to free-
standing ASCs increased over the decade. Based on the
SASD of 2002 to 2007, 92% of the ASC visits were surgical
visits, and the remaining were likely preoperative assess-
ment visits and postoperative follow-up visits because there
were no procedure codes recorded for these visits. The top
3 surgery categories performed in ASCs from 2002 to 2007
were digestive system (29.7%), musculoskeletal system
(12.5%), and eye (12.2%).
DISCUSSION
This study provides valuable information for understand-
ing the epidemiologic patterns of MH in ASC settings. The
results indicate that the prevalence of MH among ASCs in
New York State between 2002 and 2011 is 0.18 per 100,000
discharges (95% CI, 0.12–0.25). In previous studies, the
prevalence of MH in hospital surgical patients was found
to be approximately 1 per 100,000 in New York State3 and
aDetails of the record selection criteria are provided in the New York State
Ambulatory Surgery Databases le composition notes. Available at http://
www.hcup-us.ahrq.gov/db/state/sasddist/sasddist_filecompny.jsp.
Accessed July 20, 2014.
Copyright © 2015 International Anesthesia Research Society. Unauthorized reproduction of this article is prohibited.
February 2016 Volume 122 Number 2 www.anesthesia-analgesia.org 451
1.3 patients per 100,000 in the United States.12 To our knowl-
edge, this study is among the rst to estimate the prevalence
of MH in ambulatory settings. The results indicate that the
overall prevalence of MH in ASCs in New York State is
much less than reported in hospital surgical patients, prob-
ably due to enhanced MH awareness and preferential treat-
ment of MH-susceptible patients in the inpatient setting. It
is important to note that the prevalence of MH discussed
in this study encompasses both MH susceptibility and MH
incidents.
Our results also indicate that 16.7% of patients with
an MH diagnosis did not receive anesthesia. Because
patients in ASCs usually undergo low-risk surgical pro-
cedures such as extraction of lens, which are less com-
plex and less invasive than those performed in hospital
settings, the anesthesia care often involves only regional
and local anesthetics, decreasing the risk of triggering
MH among MH-susceptible patients. Compared with
hospitals, freestanding ASCs have fewer resources and
capabilities to provide advanced treatment for urgent and
Table 1. Prevalence and 95% CIs of Malignant Hyperthermia due to Anesthesia by Patient Characteristics in
Ambulatory Surgery Centers, New York State, 2002 to 2011
Patient characteristics
Number of
discharges
Number of discharges
with MH diagnosis
Prevalence per
100,000 discharges 95% CI
Age (y)a
<18 1,216,824 b0.41 0.05–0.77
18–44 4,282,667 13 0.30 0.14–0.47
45–64 6,493,986 b0.09 0.02–0.17
65+ 5,016,563 b0.14 0.04–0.24
Sexa
Female 7,259,368 14 0.19 0.09–0.29
Male 9,829,732 17 0.17 0.09–0.26
Charlson-Deyo Comorbidity Index
0 15,211,242 23 0.15 0.09–0.21
1+ 1,881,523 b0.43 0.13–0.72
Exposure to anesthesiac
General anesthesia 4,629,061 15 0.32 0.02–0.26
Other anesthesia 7,708,034 —b0.13 0.05–0.21
No anesthesia 3,621,951 b0.14 0.02–0.26
Payment typea
Medicare/Medicaid 6,400,123 12 0.19 0.08–0.29
Private insurance 8,833,991 16 0.18 0.09–0.27
Other 1,533,246 b0.20 0.00–0.42
Year of discharge
2002–2006 7,439,713 b0.11 0.03–0.18
2007–2011 9,653,052 23 0.24 0.14–0.34
ASC type
Hospital based 14,434,194 31 0.22 0.14–0.29
Freestanding 2,658,571 0 0
Total 17,092,765 31 0.18 0.12–0.25
ASC=ambulatory surgery center ; CI=condence interval; MH=malignant hyperthermia.
aThere were 82,484 discharges with age less than 1 year, 241 (<0.00%) discharges with missing information on age; 0.02% discharges with missing information
on sex; and 325,405 (1.90%) discharges with missing information on payment type.
bThese data are not presented as the report of data for any subgroup with 10 or fewer subjects is prohibited by the Healthcare Cost and Utilization Project State
Ambulatory Surgery Databases data use agreement.
cThere were 1,133,719 (6.63%) discharges and 1 case with missing information on exposure to anesthesia.
Table 2. Prevalence and 95% CIs of Malignant Hyperthermia due to Anesthesia by Clinical Diagnosis
Categorya in Ambulatory Surgery Centers, New York State, 2002 to 2011
Diagnosis category
Number of
discharges
Prevalence per
100,000 discharges 95% CI
Respiratory system 640,412 0.63 0.01–1.24
Complication pregnancy, birth, puerperium 597,551 0.34 0.00–0.80
Digestive system 2,995,634 0.23 0.06–0.41
Musculoskeletal, Connective tissue 1,877,673 0.21 0.00–0.42
Nervous system, sense organs 2,531,522 0.20 0.02–0.37
Neoplasm 2,133,060 0.19 0.00–0.37
Genitourinary system 1,595,996 0.19 0.00–0.40
Circulatory system 1,069,211 0.09 0.00–0.28
Other 1,446,160 0.07 0.00–0.21
Total 17,092,698b0.18 0.00–0.25
CCS = Clinical Classication Software; CI = condence interval.
aCCS is used to aggregate clinical diagnosis categories. Individual malignant hyperthermia cases are not presented because the report of data for any subgroup
with 10 or fewer subjects is prohibited by the State Ambulatory Surgery Databases data use agreement.
bThere were 67 discharges missing a CCS diagnosis category.
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Malignant Hyperthermia in Ambulatory Surgery
452 www.anesthesia-analgesia.org ANESTHESIA & ANALGESIA
life-threatening events. Many ASCs do not have imme-
diate laboratory access to make a diagnosis and moni-
tor its treatment.13 Therefore, MH-susceptible patients or
patients who have been diagnosed with MH might choose
to undergo surgery without general anesthesia or in hos-
pital settings that are better equipped to manage a MH cri-
sis, providing another plausible explanation for the lower
prevalence of MH in ASCs.
Consistent with previous studies of inpatient popula-
tions, the age group for patients with the highest prevalence
of MH in ASCs is <45 years.12 Although previous studies
in hospital surgery patients reported a higher prevalence
of MH in males than in females,3,12 this study did not nd
a signicant difference between sexes in the prevalence of
MH in ASCs, due in part to the modest number of MH
cases included in the study. One possible explanation for
the divergent nding from hospital surgery patients might
be differences in utilization patterns of ASCs between
sexes. Another nding of the study is that the category of
ear surgery has the highest prevalence of MH. Insertion
of tympanostomy tubes is the most common ambulatory
surgery performed on children in the United States.14
One possible reason for the increased prevalence of MH
in patients undergoing ear surgery might be that these
patients are more likely to develop postoperative fever,
and thus, the fever may be misdiagnosed as MH. It is
also possible that the heightened prevalence of MH in ear
surgery resulted from confounding factors, such as type
of anesthesia. Further research using larger datasets and
more sophisticated statistical techniques may help under-
stand whether there is a causal relationship between ear
surgery and excess risk of MH.
Our study has several limitations. First, our data sets
did not contain variables that would allow us to distin-
guish incident MH events from visits where patients have
a family history of MH or documented MH susceptibility.
ICD-9 codes are likely to be more accurate for calculating
disease prevalence than for calculating disease incidence
because incidence requires identication of new cases or
cases without previous documentation.15 The prevalence of
MH as found in this study is the combined cases of inci-
dence and MH-susceptible individuals during their stay
in the ASCs. As suggested by an earlier study, to improve
specicity of searches for incident MH events using admin-
istrative databases such as SASD, it might be meaningful to
include information on surgical procedure and dantrolene
administration.16 Another approach is to review medical
records for patients with a recorded diagnosis of MH in
combination with ICD codes because clinical evidence will
be useful in differentiating incident MH cases from MH
susceptibility in ASCs.15 The absence of ICD-9-CM surgical
procedures since 2008 in the data set made it impossible
for us to examine the associations between MH prevalence
and types of surgical procedures among ambulatory sur-
gery patients in recent years.
Second, SASDs are proprietary databases that focus on
discharge diagnoses. The accuracy and completeness of
MH diagnosis and coding may vary across facilities. Based
on a recent study, the most common reason for inaccurate
MH coding for hospital discharge records is because of high
fever unrelated to anesthesia.16 The study also nds that
prevalence of MH susceptibility is more likely to be cap-
tured accurately by ICD-9-CM code than MH incidence,16
implying that by using administrative databases such as
SASD, the MH prevalence found in our study could be
reecting a larger proportion of MH-susceptible patients
rather than MH incidence. Since the diagnosis code was rst
introduced in 1997,16 familiarity of MH coding among phy-
sicians and medical coders might vary signicantly across
ASCs, leading to potential underreporting, misdiagnosis, or
miscoding of MH cases in our data sets. As demonstrated by
our study, the number of freestanding ASCs has increased
threefold over the decade, but no MH case was reported
from any freestanding ASCs. This observation suggests that
compared with hospital-based ASCs in which physician
experts or well-trained medical coders could identify and
report MH cases, freestanding ASCs might lack experienced
medical staff to recognize the disease and record MH cases
accurately. Further evaluation of the sensitivity and speci-
city of MH coding in outpatient administrative databases
might help improve the accuracy of epidemiologic studies
in ambulatory care settings.
Figure 1. Prevalence per 100,000 discharges and SE of malignant
hyperthermia due to anesthesia by surgical procedure category in
ambulatory surgery centers, New York State, 2002 to 2007. Clinical
Classication Software is used to aggregate surgical procedure cat-
egories. Eight percent of discharges were missing information on
surgical procedure category.
Figure 2. Number of ambulatory surger y center (ASC) discharges in
New York State, 2002 to 2011.
Copyright © 2015 International Anesthesia Research Society. Unauthorized reproduction of this article is prohibited.
February 2016 Volume 122 Number 2 www.anesthesia-analgesia.org 453
Third, the prevalence reported in our study was based
on the number of ambulatory surgery discharges, rather
than unique individual patients. MH patients who were
transferred from other health care facilities and died in
the emergency room before admission to the hospital are
not included in the SASD. Unplanned admissions to hos-
pitals after ambulatory surgery were estimated to occur
in 0.5% to 1.5% of cases.17,18 Finally, because of the mod-
est number of MH cases in the study sample, our analy-
sis was limited to descriptive statistics. In the absence of
multivariate analysis, it was not possible for us to iden-
tify the risk factors for MH in ASCs with adjustment for
confounding factors.
Despite these limitations, the large sample size of the
SASD database enable epidemiologic analyses of a rare
medical condition such as MH. Among ASC discharges in
New York State, the overall prevalence of MH was less than
among hospital discharges. Even though our study shows
that all 31 patients with a recorded diagnosis of MH were
discharged alive from ASCs, we cannot conclude that it is
safe for patients with MH susceptibility to have surgery in
an ambulatory setting. Conversely, MH susceptibility is not
a contraindication for anesthesia and surgery in an ambu-
latory setting. All facilities where anesthesia is provided
should be prepared to recognize, treat, and manage an MH
crisis according to the guidelines established by accredit-
ing agencies and the Malignant Hyperthermia Association
of the United States. The ndings of our study should be
valuable for informing health care policy and developing
clinical guidelines to ensure patient safety in ASCs. E
DISCLOSURES
Name: Zhen Lu, MPH.
Contribution: This author reviewed the literature, analyzed the
data, and wrote the draft manuscript.
Attestation: Zhen Lu has seen the original study data, reviewed
the analysis of the data, and approved the nal manuscript.
Conicts of Interest: Zhen Lu declares no conicts of interest.
Name: Henry Rosenberg, MD.
Contribution: This author helped design the study, interpret
the ndings, and revise the manuscript.
Attestation: Henry Rosenberg has seen the original study
data, reviewed the analysis of the data, and approved the nal
manuscript.
Conicts of Interest: Henry Rosenberg reported a conict of
interest with Eagle Pharmaceuticals (Woodcliff Lakes, NJ) and
received a 1-time speaking fee from Eagle Pharmaceuticals, a
company that manufactures Ryanodex, a concentrated formu-
lation of dantrolene approved for the treatment of malignant
hyperthermia.
Name: Joanne E. Brady, PhD.
Contribution: This author helped supervise the statistical anal-
ysis, interpret the results, and write the manuscript.
Attestation: Joanne E. Brady has seen the original study data,
reviewed the analysis of the data, and approved the nal
manuscript.
Conicts of Interest: Joanne E. Brady declares no conicts of
interest.
Name: Guohua Li, MD, DrPH.
Contribution: This author designed the study, acquired the
data, supervised the data analysis, and oversaw the develop-
ment of the manuscript.
Attestation: Guohua Li has seen the original study data,
reviewed the analysis of the data, approved the nal manuscript,
and is the author responsible for archiving the study les.
Conicts of Interest: Guohua Li declares no conicts of interest.
This manuscript was handled by: Sorin J. Brull, MD.
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... Malignant hyperthermia (MH) is a rare life-threatening condition (incidence 0.2-1.6 in 100,000) triggered by exposure to volatile anesthetics (halothane, enflurane, isoflurane, desflurane, or sevoflurane) or succinylcholine. [68][69][70] In susceptible patients, these agents induce an uncontrolled hypermetabolic state resulting in a dramatic increase in oxygen consumption, CO 2 production, and hyperthermia. Early signs of MH include hypercapnia and sinus tachycardia; later signs include muscle rigidity, hyperthermia, and tachypnea. ...
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Cardiac arrest in the operating room and in the immediate postoperative period is a potentially catastrophic event that is almost always witnessed and is frequently anticipated. Perioperative crises and perioperative cardiac arrest, although often catastrophic, are frequently managed in a timely and directed manner because practitioners have a deep knowledge of the patient's medical condition and details of recent procedures. It is hoped that the approaches described here, along with approaches for the rapid identification and management of specific high-stakes clinical scenarios, will help anesthesiologists continue to improve patient outcomes.
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Malignant hyperthermia is an extremely rare, potentially lethal disorder that occurs in susceptible patients who are exposed to triggering agents such as volatile anesthetic gases or depolarizing muscle relaxants. The clinical manifestations of malignant hyperthermia include hypermetabolism, hyperthermia, hypercapnia, and sustained skeletal muscle rigidity, which result in cardiac arrest, brain damage, and death. It is associated with a high morbidity and mortality rate if not recognized immediately and treated appropriately. We report a case of suspected malignant hyperthermia in a young male patient undergoing axillary osmidrosis surgery.
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Halogenated anesthetics and succinylcholine administration occasionally cause serious complications such as malignant hyperthermia, rhabdomyolysis, and hyperkalemia in patients with neuromuscular diseases. Sensitivity to anesthetic agents can accentuate dysautonomia, cardiomyopathy, dysrhythmias, atelectasis, and nosocomial infections. Pre-operative evaluation is important. Regional anesthesia should be used whenever feasible. We discuss the complications and peri-operative considerations of anesthesia administration to patients with neuromuscular disease.
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Background Malignant hyperthermia (MH) is a low-frequency, high-impact event that many certified registered nurse anesthetists may be unprepared to manage due to limited clinical experience. Method A pretest, posttest, repeated-measures design was used to evaluate whether certified registered nurse anesthetists' MH knowledge improved immediately after and three months after high-fidelity simulation training. Technical and nontechnical skills were assessed during simulation training. Results After implementation, mean MH knowledge scores and self-confidence levels remained higher at three-month postimplementation than pretest scores. Conclusion MH simulation training increased participant's knowledge and self-confidence needed to manage an MH crisis.
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Prompt attention to the common neuromuscular emergencies (NME) that could present during pregnancy is essential for maternal-fetal wellbeing. Pregnancy in itself has its own challenges in management, and dealing with an NME during that critical time period is of utmost importance. This chapter describes common neuromuscular emergencies that could present during pregnancy. Neurologists are often expected to deal with a neuromuscular emergency in a pregnant female. It is often difficult to evaluate and treat these patients without proper understanding of the disease process. The physiologic changes during pregnancy, labor, and puerperium increase the maternal risk of neuromuscular complications. The purpose of the chapter is not to detail about every single neurologic disorder which could happen in pregnant females but to focus on commonly encountered neuromuscular emergencies confronted by the treating physician and how to practically deal with it. Most common disorders are listed below according to the location of injury: 1. Spinal cord: Trauma 2. Nerve and nerve roots: Guillain-Barre syndrome, compression-related nerve injuries 3. NM junction: Myasthenia gravis 4. Muscle: Inflammatory muscle disease
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Background: In 1997, the International Classification of Diseases (ICD), 9th Revision Clinical Modification (ICD-9) coding system introduced the code for malignant hyperthermia (MH) (995.86). The aim of this study was to estimate the accuracy of coding for MH in hospital discharge records. Methods: An expert panel of anesthesiologists reviewed medical records for patients with a discharge diagnosis of MH based on ICD-9 or ICD-10 codes from January 1, 2006 to December 31, 2008 at six tertiary care medical centers in North America. All cases were categorized as possible, probable, or fulminant MH, history of MH (family or personal) or other. Results: A total of 47 medical records with MH diagnoses were reviewed; 68.1% had a documented surgical procedure and general anesthesia, and 23.4% (95% CI, 12.3-38.0%) had a possible, probable, or fulminant MH event. Dantrolene was given in 81% of the MH events. All patients judged to have an incident MH event survived to discharge. Family and personal history of MH accounted for 46.8% of cases. High fever without evidence of MH during admission accounted for 23.4%, and the reason for MH coding was unclear in 6.4% of cases. Conclusions: Approximately one quarter of ICD-9 or ICD-10 coded MH diagnoses in hospital discharge records refer to incident MH episodes and an additional 47% to MH susceptibility (including personal history or family history). Information such as surgical procedure, anesthesia billing data, and dantrolene administration may aid in identifying incident MH cases among those with an ICD-9 or ICD-10 coded MH diagnosis in their hospital discharge records.
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We analyzed cases of malignant hyperthermia (MH) reported to the North American MH Registry for clinical characteristics, treatment, and complications. Our inclusion criteria were as follows: AMRA (adverse metabolic/musculoskeletal reaction to anesthesia) reports between January 1, 1987 and December 31, 2006; "very likely" or "almost certain" MH as ranked by the clinical grading scale; United States or Canadian location; and more than one anesthetic drug given. An exclusion criterion was pathology other than MH; for complication analysis, patients with unknown status or minor complications attributable to dantrolene were excluded. Wilcoxon rank sum and Pearson exact chi(2) tests were applied. A multivariable model of the risk of complications from MH was created through stepwise selection with fit judged by the Hosmer-Lemeshow statistic. Young males (74.8%) dominated in 286 episodes. A total of 6.5% had an MH family history; 77 of 152 patients with MH reported >or=2 prior unremarkable general anesthetics. In 10 cases, skin liquid crystal temperature did not trend. Frequent initial MH signs were hypercarbia, sinus tachycardia, or masseter spasm. In 63.5%, temperature abnormality (median maximum, 39.1 degrees C) was the first to third sign. Whereas 78.6% presented with both muscular abnormalities and respiratory acidosis, only 26.0% had metabolic acidosis. The median total dantrolene dose was 5.9 mg/kg (first quartile, 3.0 mg/kg; third quartile, 10.0 mg/kg), although 22 patients received no dantrolene and survived. A total of 53.9% received bicarbonate therapy. Complications not including recrudescence, cardiac arrest, or death occurred in 63 of 181 patients (34.8%) with MH. Twenty-one experienced hematologic and/or neurologic complications with a temperature <41.6 degrees C (human critical thermal maximum). The likelihood of any complication increased 2.9 times per 2 degrees C increase in maximum temperature and 1.6 times per 30-minute delay in dantrolene use. Elevated temperature may be an early MH sign. Although increased temperature occurs frequently, metabolic acidosis occurs one-third as often. Accurate temperature monitoring during general anesthetics and early dantrolene administration may decrease the 35% MH morbidity rate.
Article
Objective: Insertion of tympanostomy tubes is the most common ambulatory surgery performed on children in the United States. Tympanostomy tubes are most often inserted because of persistent middle ear fluid, frequent ear infections, or ear infections that persist after antibiotic therapy. Despite the frequency of tympanostomy tube insertion, there are currently no clinical practice guidelines in the United States that address specific indications for surgery. This guideline is intended for any clinician involved in managing children, aged 6 months to 12 years, with tympanostomy tubes or being considered for tympanostomy tubes in any care setting, as an intervention for otitis media of any type. Purpose: The primary purpose of this clinical practice guideline is to provide clinicians with evidence-based recommendations on patient selection and surgical indications for and management of tympanostomy tubes in children. The development group broadly discussed indications for tube placement, perioperative management, care of children with indwelling tubes, and outcomes of tympanostomy tube surgery. Given the lack of current published guidance on surgical indications, the group focused on situations in which tube insertion would be optional, recommended, or not recommended. Additional emphasis was placed on opportunities for quality improvement, particularly regarding shared decision making and care of children with existing tubes. ACTION STATEMENTS: The development group made a strong recommendation that clinicians should prescribe topical antibiotic eardrops only, without oral antibiotics, for children with uncomplicated acute tympanostomy tube otorrhea. The panel made recommendations that (1) clinicians should not perform tympanostomy tube insertion in children with a single episode of otitis media with effusion (OME) of less than 3 months' duration; (2) clinicians should obtain an age-appropriate hearing test if OME persists for 3 months or longer (chronic OME) or prior to surgery when a child becomes a candidate for tympanostomy tube insertion; (3) clinicians should offer bilateral tympanostomy tube insertion to children with bilateral OME for 3 months or longer (chronic OME) and documented hearing difficulties; (4) clinicians should reevaluate, at 3- to 6-month intervals, children with chronic OME who did not receive tympanostomy tubes until the effusion is no longer present, significant hearing loss is detected, or structural abnormalities of the tympanic membrane or middle ear are suspected; (5) clinicians should not perform tympanostomy tube insertion in children with recurrent acute otitis media (AOM) who do not have middle ear effusion in either ear at the time of assessment for tube candidacy; (6) clinicians should offer bilateral tympanostomy tube insertion to children with recurrent AOM who have unilateral or bilateral middle ear effusion at the time of assessment for tube candidacy; (7) clinicians should determine if a child with recurrent AOM or with OME of any duration is at increased risk for speech, language, or learning problems from otitis media because of baseline sensory, physical, cognitive, or behavioral factors; (8) in the perioperative period, clinicians should educate caregivers of children with tympanostomy tubes regarding the expected duration of tube function, recommended follow-up schedule, and detection of complications; (9) clinicians should not encourage routine, prophylactic water precautions (use of earplugs, headbands; avoidance of swimming or water sports) for children with tympanostomy tubes. The development group provided the following options: (1) clinicians may perform tympanostomy tube insertion in children with unilateral or bilateral OME for 3 months or longer (chronic OME) and symptoms that are likely attributable to OME including, but not limited to, vestibular problems, poor school performance, behavioral problems, ear discomfort, or reduced quality of life and (2) clinicians may perform tympanostomy tube insertion in at-risk children with unilateral or bilateral OME that is unlikely to resolve quickly as reflected by a type B (flat) tympanogram or persistence of effusion for 3 months or longer (chronic OME).
Article
Objectives: Implementation of the International Statistical Classification of Disease and Related Health Problems, 10th Revision (ICD-10) coding system presents challenges for using administrative data. Recognizing this, we conducted a multistep process to develop ICD-10 coding algorithms to define Charlson and Elixhauser comorbidities in administrative data and assess the performance of the resulting algorithms. Methods: ICD-10 coding algorithms were developed by "translation" of the ICD-9-CM codes constituting Deyo's (for Charlson comorbidities) and Elixhauser's coding algorithms and by physicians' assessment of the face-validity of selected ICD- 10, codes. The process of carefully developing ICD-10 algorithms also produced modified and enhanced ICD-9-CM coding algorithms for the Charlson and Elixhauser comorbidities. We then used data on in-patients aged 18 years and older in ICD-9-CM and ICD-10 administrative hospital discharge data from a Canadian health region to assess the comorbidity frequencies and mortality prediction achieved by the original ICD-9-CM algorithms, the enhanced ICD-9-CM algorithms, and the new ICD-10 coding algorithms. Results: Among 56,585 patients in the ICD-9-CM data and 58,805 patients in the ICD-10 data, frequencies of the 17 Charlson comorbidities and the 30 Elixhauser comorbidities remained generally similar across algorithms. The new ICD-10 and enhanced ICD9-CM coding algorithms either matched or outperformed the original Deyo and Elixhauser ICD-9-CM coding algorithms in predicting in-hospital mortality. The C-statistic was 0.842 for Deyo's ICD9-CM coding algorithm, 0.860 for the ICD-10 coding algorithm, and 0.859 for the enhanced ICD-9-CM coding algorithm, 0.868 for the original Elixhauser ICD-9-CM coding algorithm, 0.870 for the ICD-10 coding algorithm and 0.878 for the enhanced ICD-9-CM coding algorithm. Conclusions: These newly developed ICD-10 and ICD-9-CM comorbidity coding algorithms produce similar estimates of comorbidity prevalence in administrative data, and may outperform existing ICD-9-CM coding algorithms.
Article
Administrative databases are increasingly used for studying outcomes of medical care. Valid inferences from such data require the ability to account for disease severity and comorbid conditions. We adapted a clinical comorbidity index, designed for use with medical records, for research relying on International Classification of Diseases (ICD-9-CM) diagnosis and procedure codes. The association of this adapted index with health outcomes and resource use was then examined with a sample of Medicare beneficiaries who underwent lumbar spine surgery in 1985 ( n = 27,111). The index was associated in the expected direction with postoperative complications, mortality, blood transfusion, discharge to nursing home, length of hospital stay,and hospital charges. These associations were observed whether the index incorporated data from multiple hospitalizations over a year's time, or just from the index surgical admission. They also persisted after controlling for patient age. We conclude that the adapted comorbidity index will be useful in studies of disease outcome and resource use employing administrative databases.
Article
Malignant hyperthermia (MH) is a pharmacogenetic syndrome that variably expresses itself on exposure to triggering agents. MH prevalence in the United States is not well documented. In this study, we assessed the prevalence of MH in New York State hospitals. Using New York hospital discharge data for the years 2001 through 2005, we identified all patients with a diagnosis of MH due to anesthesia using International Classification of Diseases, Ninth Revision, Clinical Modification code 995.86. MH prevalence was evaluated by demographic and clinical characteristics. Of the 12,749,125 discharges from New York hospitals during the study period, 73 patients had a recorded diagnosis of MH due to anesthesia. Nearly three quarters of the MH patients were male and 71% were patients from emergency/urgent admissions. The estimated prevalence rate of MH was 0.96 (95% confidence interval [CI] 0.67-1.24) per 100,000 surgical discharges and 1.08 (95% CI 0.75-1.41) per 100,000 discharges in which there was any indication of exposure to anesthesia. The estimated prevalence of MH for males was 2.5 to 4.5 times the rate for females. The prevalence of MH due to anesthesia in surgical patients treated in New York State hospitals is approximately 1 per 100,000. MH risk in males is significantly higher than in females.
Article
Malignant hyperthermia (MH) is a potentially fatal pharmacogenetic disorder with an estimated mortality of less than 5%. The purpose of this study was to evaluate the current incidence of MH and the predictors associated with in-hospital mortality in the United States. The Nationwide Inpatient Sample, which is the largest all-payer inpatient database in the United States, was used to identify patients discharged with a diagnosis of MH during the years 2000-2005. The weighted exact Cochrane-Armitage test and multivariate logistic regression analyses were used to assess trends in the incidence and risk-adjusted mortality from MH, taking into account the complex survey design. From 2000 to 2005, the number of cases of MH increased from 372 to 521 per year. The occurrence of MH increased from 10.2 to 13.3 patients per million hospital discharges (P = 0.001). Mortality rates from MH ranged from 6.5% in 2005 to 16.9% in 2001 (P < 0.0001). The median age of patients with MH was 39 (interquartile range, 23-54 yr). Only 17.8% of the patients were children, who had lower mortality than adults (0.7% vs. 14.1%, P < 0.0001). Logistic regression analyses revealed that risk-adjusted in-hospital mortality was associated with increasing age, female sex, comorbidity burden, source of admission to hospital, and geographic region of the United States. The incidence of MH in the United States has increased in recent years. The in-hospital mortality from MH remains elevated and higher than previously reported. The results of this study should enable the identification of areas requiring increased focus in MH-related education.
Article
Administrative databases are increasingly used for studying outcomes of medical care. Valid inferences from such data require the ability to account for disease severity and comorbid conditions. We adapted a clinical comorbidity index, designed for use with medical records, for research relying on International Classification of Diseases (ICD-9-CM) diagnosis and procedure codes. The association of this adapted index with health outcomes and resource use was then examined with a sample of Medicare beneficiaries who underwent lumbar spine surgery in 1985 (n = 27,111). The index was associated in the expected direction with postoperative complications, mortality, blood transfusion, discharge to nursing home, length of hospital stay, and hospital charges. These associations were observed whether the index incorporated data from multiple hospitalizations over a year's time, or just from the index surgical admission. They also persisted after controlling for patient age. We conclude that the adapted comorbidity index will be useful in studies of disease outcome and resource use employing administrative databases.
Article
The purpose of this study was to examine the frequency of return hospital visits after ambulatory surgery discharge and to identify any predictor variables for its occurrence. A retrospective review of hospital records for all patients returning to the same hospital within 30 days after ambulatory surgery was conducted. Data on return hospital visits that resulted in rehospitalization (as an inpatient or to the ambulatory surgery unit [ASU]) or treatment as an outpatient in the emergency room were recorded. A total of 6243 patients underwent ambulatory surgery over 12 consecutive months and 187 returned to the same hospital of which 1.3% were for complications. Of all the returns, 54% returned to the emergency room (ER) and 46% were rehospitalized as inpatients or to ASU. To identify factors associated with an increased likelihood of return, two case controls for each return visit were obtained from medical records of ambulatory surgical patients operated on during the same time period. Results of the multivariate analysis on the matched case controls identified urology as the only significant surgical service that predicted returns. (Odds ratio 27.87; confidence interval [CI] 3.78-74.86; P = 0.0002). A separate analysis of the most common ASU procedures performed identified two surgical procedures that predicted hospital return as compared with overall ambulatory surgery population: patients undergoing varicocelectomy and hydrocelectomy procedures were 8.3 times more likely to return (CI 2.090-23.75; P = 0.0042); patients undergoing dilation and curettage were three times as likely to return (CI 1.78-5.55; P = 0.0002). Bleeding was the most common reason for all hospital returns (41.5%), with 76.5% of these patients treated and discharged through the ER. The increased likelihood of return visits after urology procedures warrants further evaluation. As patients with bleeding were most likely to return to the ER and discharged, more effective pre- and postprocedure patient education may further reduce this occurrence. Better informing patients regarding the prognosis of bleeding, and advising them of medical alternatives, could reduce inappropriate patient returns to the ER.