An Association Between Systolic Blood Pressure and Stroke Among Patients With Impaired Consciousness in Out-of-Hospital Emergency Settings

Taro Irisawa; Taku Iwami; Tetsuhisa Kitamura; Chika Nishiyama; Tomohiko Sakai; Kayo Tanigawa-Sugihara; Sumito Hayashida; Tatsuya Nishiuchi; Tadahiko Shiozaki; Osamu Tasaki; Takashi Kawamura; Atsushi Hiraide; Takeshi Shimazu

Disclosures

BMC Emerg Med. 2013;13(24) 

In This Article

Results

During these 10 years, a total of 1,840,784 emergency patients were documented during the study period in Osaka City (Figure 1). Among 1,463,890 adult patients, 643,141 had medical causes excluding obstetrical and trauma causes, 128,678 yielded an impaired consciousness, and 106,706 with prehospital SBP data were eligible for our analyses.

Figure 1.

Study flow of emergency patients from January 1, 1998 to December 31, 2007. EMS: emergency medical service.

Table 2 shows the characteristics between 106,706 patients with SBP value and 21,972 patients without SBP value. In patients with SBP, mean men age was 63.1 years, and 54.2% were male. The proportion of mild impaired consciousness was 70.7%, moderate impaired consciousness 15.9%, and severe impaired consciousness 13.4%, respectively. Forty-nine percent of patients with impaired consciousness were assessed in a private residence. Mean initial SBP was 139.5 mmHg. Time interval from call to hospital arrival was 25.1 minutes. Although there were statistically significant differences because of the very large number, the characteristics between the groups were almost similar.

Table 3 shows the characteristics of eligible patients with impaired consciousness by prehospital SBP. As a whole, the proportion of patients with severe impaired consciousness significantly increased from 14.5% in the <100 mmHg SBP group to 27.6% in the > =200 mmHg SBP group (P for trend <0.001). Because there was an increase on the proportion of severe disturbance from 10.6% in the 101–120 mmHg group to 14.5% in the = <100 mmHg suggesting that low BP might be a factor in the altered mentation, the group with 101–120 mmHg SBP was defined as a reference group to show the relationship between prehospital SBP and stroke occurrence among patients with impaired consciousness.

The proportions of patients with or without stroke according to the SBP were noted in Table 4. Among patients with impaired consciousness, 31.0% had the proportion of stroke (SAH 1.5%, ICH 6.3%, and IS 23.2%, respectively). This significantly increased from 17.1% to 63.7% (P for trend <0.001). The trends by the subtype of stroke were qualitatively similar.

Figure 2 shows the relationship between SBP measured by EMS in prehospital settings and stroke occurrence among patients with impaired consciousness. The occurrence of stroke significantly increased with increasing SBP (AOR 1.34, 95% CI 1.33 to 1.35), and the AOR of the SBP > =200 mmHg group versus the SBP 101–120 mmHg group was 5.26 (95% CI 4.93 to 5.60). In the subgroup analyses in the Figure 3, the AOR for 20 mmHg-increment of SBP was 1.48 (95% CI 1.43 to 1.52) in SAH, 1.69 (95% CI 1.66 to 1.72) in ICH, and 1.14 (95% CI 1.13 to 1.15) in IS, and the AOR of SAH and ICH was greater than that of IS. The AOR of the SBP > =200 mmHg group versus the SBP 101–120 mmHg group was 9.76 (95% CI 7.86 to 12.12) in SAH, 16.16 (95% CI 14.43 to 18.10) in ICH, and 1.52 (1.42 to 1.62) in IS, and the AOR of SAH and ICH was greater than that of IS.

Figure 2.

Relationship between SBP measured by EMS personnel in prehospital settings and the risk of stroke occurrence among patients with impaired consciousness. AORs: adjusted odds ratios.

Figure 3.

Relationships between SBP measured by EMS personnel in prehospital settings and the risk of stroke occurrence by its stroke subtype among patients with impaired consciousness. (A) SAH, (B) ICH, and (C) IS. AORs; adjusted odds ratios; SAH: subarachnoid hemorrhage; IS: ischemic stroke; ICH: intracranial hemorrhage.

Table 5 shows the relationship between prehospital SBP and stroke occurrence by impaired consciousness level. The AOR of the SBP > =200 mmHg group versus the SBP 101–120 mmHg group was 16.84 (95% CI 11.71 to 24.21) in mild disturbance and 11.55 (95% CI 6.70 to 19.90) in moderate disturbance among SAH patients, and 21.19 (95% CI 17.86 to 25.13) in mild disturbance, 13.58 (95% CI 10.71 to 17.22) in moderate disturbance, and 12.61 (95% CI 10.35 to 15.35) in severe disturbance among ICH patients.

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