Prehospital Nitroglycerin in Tachycardic Chest Pain Patients: A Risk for Hypotension or Not?

Figures & data

Table 1. Provincial prehospital nitroglycerin protocol: 2010-2012 (Quebec, Canada)⁹

Indication	Contraindication
Age ≥ 35 years with chest pain of suspected cardiac origin*	- Allergy to nitrates- Traumatic chest pain
or	- Medication for erectile dysfunction < 24-48 hours
Age < 35 years with chest pain of suspected cardiac origin* and known for coronary artery disease	- Pregnancy- Systolic blood pressure < 100 mmHg-50 > heart rate >150

* Chest pain of suspected cardiac origin is defined as: Non–trauma-related chest pain or discomfort between the umbilicus and the jaw, including back and arms. The pain must be originating from the anterior chest (including retrosternal), may be in the form of a tightness, pressure, vise-like, squeezing, choking, punching, or indigestion, and be less than 12 hours duration if continuous. The pain should not be epigastric, subcostal, or located only in the arms or jaw; is not felt as a shock, a needle, a burn, a cut, a knife, or a pinch; and is not increased with inspiration or movement. In a patient with known coronary artery disease (CAD), the pain may be different from that previously described if it matches the patient's usual angina symptoms.

Figure 1. Inclusion/exclusion diagram. *Epinephrine and salbutamol cases were excluded for potential confounding effects on heart rate. ASA and oxygen cases were not excluded. ^† No vital signs taken within 15 minutes after the first dose of NTG, or calls lasting more than 2 hours ^‡ Patient presenting with pre-NTG BP under 100 mmHg

Table 2. Univariate comparison between non-tachycardic patients and tachycardic patients

	Non-tachycardic	Tachycardic	P-value
N	8,251	2,057
Outcomes*
Hypotension (SBP < 90 mm Hg)[%]	239 [2.9]	81 [3.9]	0.02
Drop in blood pressure > 30 mm Hg [%]	2,684 [32.5]	773 [37.6]	< 0.01
Change to consciousness [%]	39 [0.5]	12 [0.6]	0.64
Bradycardia [%]	131 [1.6]	10 [0.5]	< 0.01
Cardiac arrest [%]	26 [0.3]	4 [0.2]	0.5
Age^†
Mean years [SD]	68.2 [14.7]	65.8 [15.2]	< 0.01
Sex*
Women [%]	4,055 [49.1]	1,040 [50.6]	0.26
Men [%]	4,196 [50.9]	1,017 [49.4]
Medical History*
CAD [%]	4,832 [58.6]	1,115 [54.2]	< 0.01
Diabetes [%]	1,825 [22.1]	485 [23.6]	0.16
Dyslipidemia [%]	3,233 [39.2]	695 [33.8]	< 0.01
Hypertension [%]	4,313 [52.3]	1,011 [49.1]	0.01
Heart rate pre-NTG^†
Mean BPM [SD]	78.0 [12.3]	116.3 [15.6]	< 0.01
Systolic blood pressure pre-NTG^†
Mean mmHg [SD]	145.7 [24.7]	150.1 [26.0]	< 0.01
Treatment^†
Mean doses of NTG [SD]	2.5 [1.1]	2.5 [1.1]	0.39

* Significance determined using the Chi square test (0.05) or ^† Mann-Whitney test (0.05).

Table 3. Adjusted odds ratios for the primary outcome model [CI: 95%]

	Hypotension
Tachycardia*	1.60 [1.23–2.08]
Blood-pressure, preNTG (unit: 10mmHg)	0.64 [0.61–0.69]
Male ^†	0.90 [0.72–1.14]
Age group ^‡
53-68	1.30 [0.97–1.74]
69-85	1.13 [0.89–1.45]
86 and older	1.07 [0.87–1.32]
Medical History §
CAD	0.95 [0.74–1.23]
Diabetes	1.13 [0.86–1.49]
Dyslipidemia	1.15 [0.89–1.49]
Hypertension	1.04 [0.80–1.34]

Bolding indicates significant AOR (alpha = 0.05).

* non-tachycardia.

^† female.

^‡ 35-52.

^§ no history.

Table 4. Adjusted odds ratios for the secondary outcome model [CI: 95%]

	Blood pressure drop	Bradycardia	Reduced level of consciousness	Cardiac arrest
Tachycardia *	1.11 [1.00–1.24]	0.33 [0.17–0.64]	1.27 [0.66–2.44]	0.59 [0.21–1.72]
Blood-pressure, preNTG	1.43 [1.40–1.46]	0.88 [0.82–0.95]	0.85 [0.75–0.97]	0.92 [0.78–1.08]
(unit: 10mmHg)
Male ^†	0.92 [0.84–1.01]	2.42 [1.67–3.51]	1.33 [0.75–2.36]	2.31 [1.01–5.27]
Age group ^‡
53–68	1.07 [0.95–1.22]	2.38 [1.47–3.87]	0.31 [0.08–1.27]	0.43 [0.10–1.82]
69–85	0.92 [0.84–1.02]	0.83 [0.56–1.22]	0.45 [0.15–1.31]	0.81 [0.26–2.51]
86 and older	1.03 [0.95–1.12]	0.92 [0.68–1.26]	0.61 [0.32–1.15]	0.94 [0.43–2.07]
Medical History §
CAD	1.08 [0.98–1.20]	1.03 [0.70–1.51]	0.53 [0.28–1.00]	0.26 [0.10–0.66]
Diabetes	1.01 [0.90–1.12]	0.97 [0.64–1.46]	0.79 [0.36–1.76]	0.80 [0.26–2.43]
Dyslipidemia	1.00 [0.90–1.10]	0.88 [0.60–1.28]	0.75 [0.38–1.50]	0.90 [0.36–2.24]
Hypertension	1.01 [0.91–1.11]	1.05 [0.72–1.52]	1.18 [0.62–2.24]	1.28 [0.56–2.97]

Bolding indicates significant AOR (alpha = 0.05).

* non-tachycardia.

^† female.

^‡ 35-52.

^§ no history.