Elsevier

Annals of Vascular Surgery

Volume 44, October 2017, Pages 393-399
Annals of Vascular Surgery

Clinical Research
Impact of Ambient Temperature on Incidence of Acute Lower Limb Ischemia

This article was presented in abstract form as: Law Y., Chan Y.C., Cheng S.W. The impact of ambient temperature on acute thromboembolic lower limb ischemia, at The 16th Congress of Asian Society for Vascular Surgery and the 10th Asian Venous Forum, Bangkok, Thailand, December 2015.
https://doi.org/10.1016/j.avsg.2017.03.189Get rights and content

Background

This was a retrospective study to explore the possible association between atmospheric temperatures with the occurrence of acute leg ischemia (ALI).

Methods

A linear regression analysis was performed for a period of 10 years on the impact of ambient temperature on the incidence of ALI. Mean ambient temperature on a daily basis was retrieved electronically from our observatory, and the daily incidence of ALI was retrieved from the Clinical Data Analysis and Reporting (CDAR) system. CDAR system could retrieve clinical data from all 42 public hospitals in our region, which provided almost 90% inpatient care of the population. Daily incidence was defined as total number of emergency admissions from all 42 pubic hospitals due to ALI from 00:00 till 23:59 hr of that day.

Results

For the 10-year period, spanning from January 2005 to December 2014, there were a total of 634 recorded ALI with revascularization, 608 (95.9%) of which underwent emergency femoral embolectomy, 15 (2.4%) underwent thrombolysis, and 11 (1.7%) underwent thrombolysis and embolectomy. ALIs with primary amputation or conservative management were excluded from the study. The average daily incidence of ALI was 0.170. A linear regression model was built using mean ambient temperature as independent variable and incidence of ALI as dependent variables. The line of best fit was drawn through the data points. The daily incidence of ALI could be predicted by ambient temperature (in °C) with the equation: incidence = 0.274–0.004 × temperature (linear regression; r = −0.053, r2 = 0.003, F = 10.42, and P = 0.001). In other words, daily incidence was 0.274 at 0°C; and for every 10°C increase, the incidence would drop by 0.040. At 30°C, daily incidence of ALI was 0.154.

Conclusions

This study showed an association of cold temperature and ALI in our population. Measures to protect the susceptible population from cold temperatures should be considered.

Introduction

Many studies have shown that there is tangible association between cold weather and the incidence of acute cardiovascular events in terms of coronary syndrome,1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 cerebrovascular accidents,15, 16, 17, 18, 19, 20, 21, 22, 23, 24 aortic dissection,25, 26, 27 and rupture of aortic aneurysm.28, 29, 30, 31, 32 We have previously shown that there was a relationship between meteorological variables and the daily incidence of acute aortic events in terms of aortic dissection and rupture.33 No previous studies had been conducted to examine the relationship between cold ambient temperature and the incidence of acute leg ischemia (ALI), although we were often referred more cases in the winter months. The definition of ALI is any sudden decrease in limb perfusion causing a potential threat to limb viability.34 Presentation ranged from few hours up to 2 weeks' duration. Embolism is the most common etiology, followed by in situ thrombosis and other rare causes like dissection and trauma.

The aim of this 10-year population-based longitudinal retrospective study was to conduct a pan-territory survey to scrutinize the relationship between daily atmospheric temperature and the incidence of ALI.

Section snippets

Study Population

Hong Kong, a subtropical territory with distinct summer and winter, is an optimal place to perform observational study of this sort. The use of household heater is not common. Hence, people are open to the true ambient atmospheric temperature. Hong Kong is one of the most densely populated areas in Southeast Asia with 7.4 million people concentrated in 1,104 square kilometers (426 square miles), equating to an overall population density of about 6,300 people/square kilometers of land, 93.6% of

Results

During the 10-year study period from January 1, 2005 to December 31, 2014, there were a total of 634 cases of ALI with revascularization (Fig. 1); 608 (95.9%) of which underwent emergency femoral embolectomy, 15 (2.4%) underwent thrombolysis, and 11 (1.7%) underwent thrombolysis and embolectomy. The average daily incidence of ALI was 0.170 (range 0–3). Table I summarized our patients' baseline demographics.

Discussion

To the best of our knowledge, this is the first study in the world's literature to evaluate the effects of ambient temperature on the occurrence of ALI. This confirms our belief that more patients with ALI were referred to our vascular unit in the winter months.

Initial search of all ALI over 10 years revealed 1,764 cases, of which 634 underwent revascularization (either embolectomy or/and thrombolysis), 229 primary amputations, and 901 conservative managements. A large proportion of ALI did not

Conclusions

This 10-year population-based longitudinal study is the first pan-territory survey to show an association between cold temperature and ALI. Our findings suggested that measures to protect the susceptible population from cold temperatures should be considered.

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    The authors declare no conflicts of interest to disclose.

    The authors received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

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