Deep Accidental Hypothermia with Core Temperature Below 24°C Presenting with Vital Signs

Abstract

Pasquier, Mathieu, Noemi Zurron, Barbara Weith, Pierre Turini, Fabrice Dami, Pierre-Nicolas Carron, and Peter Paal. Deep accidental hypothermia with core temperature below 24°C presenting with vital signs. High Alt Med Biol. 15:58–63, 2014.— Background: According to the Swiss hypothermia clinical staging, patients with stage III are unconscious with preserved vital signs, with core temperature usually between 24° and 28°C. With stage IV, vital signs are absent with core temperature <24°C.

Aims:

To describe a patient presenting with HT stage III with vital signs but a core temperature of <24°C, and to search for similar patients in the medical literature.

Materials and methods:

MEDLINE was used to search for cases of deep accidental hypothermia (<24°C) and preserved vital signs.

Results:

We found 22 cases in addition to our case (n=23). Median age was 44 years (IQR 36; range 4–83) and median core temperature 22°C (IQR 1.7; 17–23.8). Vital signs were often minimal. Seven patients developed ventricular fibrillation (VF). Twenty patients survived with excellent neurological outcome.

Conclusions:

Vital signs can be present in hypothermic patients with core temperature <24°C. In deeply hypothermic patients, a careful check and prolonged check of vital functions should be made, as vital signs may be minimal. The clinical Swiss staging remains valuable in the prehospital evaluation of hypothermic patients; its correlation with core temperature should be better defined.

Introduction

Accidental hypothermia is defined as an unintentional drop in core body temperature <35°C. One of the main risks of hypothermia is cardiac arrest, which can occur at a core temperature <32°C and is very likely at <28°C (Brown et al., 2012). Hypothermia can be classified according to the Swiss staging system, based on the clinical presentation and vital signs of a patient (hypothermia stages I–V, Table 1) (Brown et al., 2012). This staging is favored over the traditional ones because it allows a core temperature estimation based on clinical findings. This is especially valuable in the prehospital environment where a reliable assessment of the core temperature is often not feasible (Soar et al., 2010). According to the Swiss staging, the core temperature of an unconscious patient with preserved vital signs is 24°–28°C (stage III), while patients with a core temperature <24°C are without vital signs (stage IV, Table 1). Both stages have a potentially good outcome if treated correctly (Brown et al., 2012).

Table 1.

Swiss Staging of Hypothermia

Stage	Clinical findings	Core temperature, °C
HT I	Conscious, shivering	35 to 32°C
HT II	Impaired consciousness, not shivering	<32 to 28°C
HT III	Unconscious, not shivering, vital signs present	<28 to 24°C
HT IV	No vital signs	<24°C
HT V	Death due to irreversible hypothermia	<13.7°C?

Adapted from Durer et al., 2003. The lowest core temperature with which someone survived an accidental hypothermia was 13.7°C (Gilbert et al., 2000).

We recently successfully treated a patient suffering from deep accidental hypothermia with preservation of a spontaneous circulation despite a core temperature of 21°C. Along with the description of this case, we aimed to identify published cases of patients with deep accidental hypothermia (core temperature <24°C) and vital signs.

Case Description

A 53-year-old woman was found unconscious at 7:00 am on the street under 2 cm of fresh snow. The ambient temperature was −6°C. At arrival of the emergency medical services, the patient was breathing with 10 breaths min⁻¹ and ECG showed a sinus bradycardia of 30 min⁻¹. Blood pressure and oxygen saturation were not measurable, but a femoral pulse was palpable. The Glasgow Coma Scale (GCS) was 6, total body rigidity was noted, and the pupils were dilated and unresponsive to light. Oxygen was provided by a face mask, and warm fluids were infused intravenously during the 10 min transport to the nearest hospital. There, a rectal temperature of 21°C was measured at 7:45 am. The patient was anesthetized, an endotracheal tube was placed, and forced air rewarming was started (Bair Hugger, 3M, Rüschlikon, Switzerland). Transfer to the nearest hospital with extracorporeal rewarming capacity took 35 minutes. Esophageal temperature at arrival at 9 am was 24.5°C. An endovascular catheter (Icy, CoolGard, Alsius, Irvine, CA) was inserted into the femoral vein and active internal rewarming was initiated. A core temperature of 32°C was reached 4 hours later. The patient was extubated the same day at 4:30 pm and was discharged from hospital 3 days after her admission without any sequelae. Her last memory before waking up in hospital was having consumed alcohol in a bar. Blood alcohol level at hospital admission was 71.6 mmolL⁻¹.

Materials and Methods

We used MEDLINE to search for a maximum of cases of deep accidental hypothermia (core temperature <24°C) with vital signs. The keyword «hypothermia» was used and the research was limited on case reports; we excluded studies on therapeutic, iatrogenic, and neonatal hypothermia and larger studies (e.g., prospective and retrospective) where vital signs of single patients, which were pertinent to this study, were not reported. There were no restrictions with regard to language or year of publication. The last access to MEDLINE was on July 1st, 2013. Additional relevant articles were hand-searched.

We recorded data on age, sex, vital parameters at the first contact, risk factors for accidental hypothermia, the rewarming method, neurological outcome, and survival. Descriptive statistics are presented as median with interquartile range.

Results

By screening 3077 abstracts, we found 22 cases of deep accidental hypothermia presenting with vital signs. The demographic characteristics and vital signs of the patients, as well as those of our patient, are reported in Table 2.

Table 2.

Summary of Characteristics of Patients with Deep Hypothermia (<24°C) Without Initial Cardiac Arrest

Publication	T° (°C) / site	Age/sex	HR (min⁻¹)	Rhythm	RR (min⁻¹)	SBP (mmHg)	Neurology	Pupils	Outcome	CPC	Reason for cooling (except exposure)	Main rewarming method
Rollstin et al., 2013	17 ND	37 F	39	AF	ND	ND	GCS 10	ND	Discharged to mental facility after 2 days	1	drugs	endovascular
Block et al., 1992	19 rectal	24 F	30–40	ND broad QRS	ND	50	GCS 5	Fixed dilated	Discharged home	1	drugs	warm infusions
Feiss et al., 1987	19 rectal	27 F	40	ND	3.5	NM	Areactive coma	Fixed dilated	Discharged home after 1 week	1	ethanol	ECR
Wickstrom et al., 1976	20 rectal	45 F	slow	ND	shallow	ND	Comatose	ND	Discharged home after 9 days	1	ethanol	ECR
Visetti et al., 1998	20 tympanic	83 F	20	sinus	3	60	Weak response to pain	Medium reactive	Discharged home	1	-	PL
Pasquier et al.	21 rectal	53 F	30	sinus	10	NM (palpable pulse)	GCS 6	Fixed dilated	Discharged home after 3 days	1	ethanol	endovascular
Raheja et al., 1981	21 ND	44 M	ND	ND	agonal	NM	ND	Dilated reactive	Discharged home after 16 days	ND	ethanol	PL
Kugelberg et al., 1967	21.4 rectal	59 M	30–50	AF	normal	70	Weak response to pain	Small	Discharged home after 42 days	1	ethanol	ECR
Splittgerber et al., 1986	21.6 rectal	ND M	60	ND	15	90	ND	small	Death hours after rewarming	5	ethanol	PL+ECR
Brodersen et al., 1996	21.8 ND	63 F	50	ND broad QRS	ND	NM	Unconscious	fixed dilated	Discharged to mental facility after 4 days	1	drugs	haemofiltration
Oberhammer et al., 2008	22 tympanic	29 M	60	ND	ND	ND (palpable pulse)	GCS 7	ND	Discharged home after 17 days	1	avalanche	ECR
Radke et al., 2005	22 tympanic	44 F	42	junctional	ND	100	GCS 10	Medium fixed	Discharged to mental facility after 3 days	1	drugs / ethanol	ECR
Papenhausen et al., 2001	22 ND	4 F	179	ND	ND	123	GCS 9	ND	Discharged home after 4 days	1	-	PL
Drenck et al., 1986	22 rectal	65 F	40	sinus	2	NM	areactive coma	ND	Discharged home	1	drugs	PL
Truscott et al., 1973	22 rectal	23 F	54	ND	slow	NM (palpable pulse)	unconnscious	ND	Death after 133 days	1	traumatic paraplegia	ECR
Fell et al., 1968	22 esophageal	42 F	ND	ND	just breathing	ND (palpable pulse)	uncounscious	Small	Discharged home after 5 weeks	1	drugs / immersion	ECR
Koppenberg et al., 2012	22.6 bladder	16 M	70	sinus	ND	121	GCS 7	Fixed dilated	Discharged home	1	snow burial	forced airwarm infusions
Laniewicz et al., 2008	22.7 bladder	68 F	30–40	junctional	6	NM	GCS 5	ND	Death after 8 days	4	-	endovascular
Wanscher et al., 2012	23 ND	16 F	ND	ND PVC	resp. distress	ND	GCS 3	ND	Discharged home after 3 days	1	immersion	ND
Raheja et al., 1981	23 rectal	45 M	25	sinus	agonal	NM (palpable pulse)	Coma	Dilated reactive	Discharged home after 28 days	ND	ethanol	warm infusions
Drenck et al., 1986	23.3 rectal	65 F	40	sinus	2	NM	Areactive coma	ND	Discharged home	1	drugs	PL
Ricou et al., 1985	23.5 rectal	34 F	45	junctional	7	70	GCS 3	Medium reactive	Discharged home after 8 days	1	drugs / ethanol / anorexia	ECR
Wickstrom et al., 1976	23.8 rectal	64 M	24	idioventricular	ND	68	Comatose	ND	Discharged home	1	-	ECR

The patients are listed in ascending order from the lowest core body temperature. AF, atrial fibrillation; CPC, cerebral performance categories (1 indicates normal or slightly diminished cerebral function, 5 is brain dead); ECR, extracorporeal rewarming; GCS, Glasgow Coma Scale; HR, heart rate; ND, not documented; NM, not measurable; PL, peritoneal lavage; PVC, premature ventricular contractions; RR, respiratory rate; SBP, systolic blood pressure; T°, core temperature.

The male:female ratio was 1:2.3. Median age was 44 years (IQR 36, range 4–83) and core temperature 22°C (IQR 1.7; 17–23.8). Heart rate was recorded in 19 patients (median 40; IQR 19; 24–179) and the respiratory rate in 8 (median 4.8; IQR 6; 2–15). Measurement of systolic blood pressure was attempted in 18 cases, but a numerical value was obtained only in 9 (median 70; IQR 32; 50–123). The GCS ranged from 3/15 to 10/15.

The causes of hypothermia besides exposure to low ambient temperature were immersion (2 patients) (Fell et al., 1968; Wanscher et al., 2012) and snow burial (2 patients) (Oberhammer et al., 2008; Koppenberg et al., 2012). Additional risk factors for hypothermia included acute alcohol intoxication (9 patients) (Kugelberg et al., 1967; Wickstrom et al., 1976; Raheja et al., 1981; Ricou et al., 1985; Splittgerber et al., 1986; Feiss et al.,1987; Radke et al., 2005), drugs (8 patients) (Fell et al., 1968; Ricou et al., 1985; Drenk et al., 1986; Block et al., 1992; Brodersen et al., 1996; Radke et al., 2005; Rollstin et al., 2013), and anorexia and traumatic paraplegia in one patient each (Truscott et al., 1973; Ricou et al., 1985).

Seven patients developed ventricular fibrillation (Fell et al., 1968; Truscott et al., 1973; Wickstrom et al., 1976; Splittgerber et al., 1986; Feiss et al.,1987; Papenhausen et al., 2001; Oberhammer et al., 2008). The main rewarming methods used were extracorporeal rewarming (10 cases) (Kugelberg et al., 1967; Fell et al., 1968; Truscott et al., 1973; Wickstrom et al., 1976 ; Feiss et al.,1987; Ricou et al., 1985; Splittgerber et al., 1986; Radke et al., 2005; Oberhammer et al., 2008); peritoneal lavage (6 cases) (Raheja et al., 1981; Splittgerber et al., 1986; Drenk et al., 1986; Visetti et al., 1998 ; Papenhausen et al., 2001), hemofiltration (1 case) (Brodersen et al., 1996), and endovascular rewarming in our case and in another two (Laniewicz et al., 2008; Rollstin et al., 2013). The neurological outcome of the 20 survivors was excellent. The death of two of the three patients who died was attributed to other causes than hypothermia (Truscott et al., 1973; Splittgerber et al., 1986;).

Discussion

We identified 23 deeply hypothermic patients (<24°C) who had vital signs and thus did not correlate with the clinical stage HT IV of the commonly used Swiss staging of accidental hypothermia. One advantage of this empirical staging system is that it enables rescuers to stage hypothermia in the prehospital setting using only clinical means, based on the presence of vital signs. Any clinical stage is assigned to a respective temperature range. We have shown that some patients do not fit into this staging system as they present with vital signs even at core temperatures <24°C. This could lead to inappropriate management of these critically hypothermic patients.

The vital signs of the patients reported in this study varied considerably. For example, the heart rate ranged from 24 min⁻¹ to 179 min⁻¹. The blood pressure was often not measurable, but reached 120 mmHg in one patient. Similarly, the respiratory rate which was often the only detectable vital sign varied between 2 and 15 min⁻¹ (Drenk et al., 1986). These findings highlight the importance of a careful and prolonged check of vital signs in deeply hypothermic patients, since vital signs can be minimal. In HT III patients, CPR should not be performed, although signs of life may be minimal as this may trigger ventricular fibrillation. Failure in detecting minimal vital signs in HT IV patients may lead to declaring a patient dead on site, whereas he may have survived with good outcome with proper treatment (Strapazzon et al.; 2012). Therefore, in deeply hypothermic patients, careful and prolonged assessment of vital signs (up to 1 min) is of utmost importance.

Hypothermia III may be defined as “Unconscious, vital signs present”, while HT IV is defined by “No vital signs”. Therefore the presence of signs of life in deeply hypothermic patients could have led to an overestimation of the core temperature and an underestimation of the risk of cardiac arrest. The fact that seven out of 23 patients (30%) developed VF highlights the high risk of cardiac arrest in deeply hypothermic patients. In these cases, cardiac arrest developed soon after arrival in the ED in two patients (Fell et al., 1968; Truscott et al., 1973), during medical care in two (Splittgerber et al., 1986; Oberhammer et al., 2008), during mobilization in the ED in one (Feiss et al.,1987), and during endotracheal intubation in two (Wickstrom et al., 1976; Papenhausen et al., 2001). Timely placement of defibrillation electrodes and careful handling of the patient through the entire management are therefore required. Current guidelines recommend advanced airway management if deemed necessary for oxygenation, but the benefits of the procedure have to be weighed against the risk of triggering VF (Soar et al., 2010; Brown et al., 2012). Guidelines on accidental hypothermia recommend that patients at risk of cardiac arrest (e.g., systolic blood pressure <90mmHg, ventricular arrhythmia, core temperature <28°C) should be primarily transferred to a hospital capable of extracorporeal rewarming, because this rewarming technique offers survival rates of 50%–100% in patients with hypothermia-induced cardiac arrest (Brown et al., 2012; Wanscher et al.; 2012). Overestimating the core temperature because of present vital signs could also lead to choose a hospital that does not offer proper rewarming facilities (Paal et al.; 2013).

In these 23 deeply hypothermic patients, five had fixed, dilated pupils despite not being in cardiac arrest, emphasizing the fact that classical signs of death cannot be interpreted inconsiderately in deeply hypothermic patients. Guidelines have been developed to overcome the dilemma of when to initiate CPR in hypothermic patients who do not have signs of life (Soar et al., 2010; Brown et al., 2012; Paal et al., 2012). As soon as the decision is taken to resuscitate a hypothermic patient, CPR should be performed continuously (Nolan et al., 2012). For longer transports a mechanical CPR may be advisable (Putzer et al., 2013). All patients except one (Papenhausen et al., 2001) who developed cardiac arrest during the management, were rewarmed extracorporeally. Our patient and two others (Laniewicz et al., 2008, Rollstin et al.; 2013) were rewarmed with intravascular catheter rewarming, a system that uses a closed-loop circuit through which warm fluid circulates, and which is in line with current guidelines (Soar et al., 2010; Brown et al., 2012). The neurological outcome of the survivors was excellent, which underlines the neuroprotective effects of deep hypothermia.

Conclusions

According to the Swiss staging of hypothermia, no vital signs would be expected when the core temperature is <24°C. This case study shows that some patients still have vital signs, although often minimal, at such low temperatures. Deeply hypothermic patients with vital signs should be carefully handled to minimize the risk of VF and should be transported to the nearest hospital with extracorporeal rewarming facilities. The clinical Swiss staging remains valuable in the prehospital evaluation of hypothermic patients where a reliable measurement of the core temperature is not possible. However, its correlation with the core temperature should be better defined. The recently established International Hypothermia Registry (https://www.hypothermia-registry.org) may provide in the future sufficient evidence for a better assignment of body temperature ranges to clinical symptoms.

Footnotes

Acknowledgments

We would like to thank Danielle Wyss for proofreading and final translation.

Author Disclosure Statement

No competing financial interests exist.

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