What's new in emergency medicine

The following represent additions to UpToDate from the past six months that were considered by the editors and authors to be of particular interest. The most recent What's New entries are at the top of each subsection.

ADULT RESUSCITATION

Effectiveness of introducer (bougie) for tracheal intubation (January 2024)

While the tracheal tube introducer (commonly referred to as a "bougie") is widely considered an important tool for emergency intubation, high-quality evidence supporting its role has been limited. In a new systematic review and meta-analysis of 18 studies involving over 9000 adult patients, use of an introducer was associated with a higher overall rate of successful first-pass intubation compared with no introducer (in most cases an tracheal tube with a stylet) [1]. First-pass success rates were higher using an introducer regardless of the method of intubation (ie, direct versus video laryngoscopy) or where intubation was performed (eg, emergency department, intensive care unit, prehospital). The introducer was most effective in patients (n = 585 in five studies) with a Cormack-Lehane III or IV view. We consider the introducer an essential tool for difficult airway management that should be readily available in the emergency department. (See "Endotracheal tube introducers (gum elastic bougie) for emergency intubation", section on 'Evidence of effectiveness'.)

Extracorporeal cardiopulmonary resuscitation (December 2023)

Extracorporeal cardiopulmonary resuscitation (ECPR) is being increasingly used, but data are limited and the benefits are uncertain. In a recent meta-analysis of 11 studies (10,000 patients) who underwent CPR, compared with standard CPR, ECPR was associated with decreased in-hospital mortality and increased long-term favorable neurologic outcome and survival at one year [2]. The benefit of ECPR was confined to patients with in-hospital cardiac arrest. These data support the growing practice of ECPR in select patients likely to benefit. (See "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)", section on 'Sudden cardiac arrest (extracorporeal cardiopulmonary resuscitation)'.)

Heart rate control in septic shock (December 2023)

Beta blockade has the potential to limit harm from the adrenergic overdrive that occurs in septic shock. However, data to support heart rate control in patients with septic shock are limited. In a recent, unblinded randomized trial of 126 patients with septic shock-related tachycardia (heart rate ≥95/min) who were receiving norepinephrine, the beta blocker landiolol did not reduce organ failure as measured by the sequential organ failure assessment score [3]. Furthermore, landiolol was associated with increased 28-day mortality compared with standard care (37 versus 25 percent). We continue to avoid the routine use of beta blockers in patients with septic shock. (See "Investigational and ineffective pharmacologic therapies for sepsis", section on 'Heart rate control'.)

ENVIRONMENTAL EMERGENCIES

Mortality in older persons after short-term weather disasters (April 2024)

Severe weather events damage infrastructure and disrupt society, leading to direct and indirect impacts on health that can disproportionately affect vulnerable populations, including older adults. In an analysis of 42 short-term weather disasters in the United States between 2011 and 2016, emergency department utilization and mortality were higher among traditional fee-for-service Medicare beneficiaries in affected counties compared with matched control counties in the week following the disaster [4]. Higher rates of mortality persisted for six weeks and translated to an estimated 20 to 31 excess deaths per storm in the post-disaster week. Targeted solutions to minimize disruptions to health care delivery may help reduce adverse health impacts of weather events in older persons and other vulnerable populations. (See "Climate emergencies", section on 'Hurricane and flood risks to health'.)

Supraglottic airway for out-of-hospital cardiac arrest from drowning (April 2024)

In a drowning victim with cardiac arrest, ventilation is generally considered the most important initial treatment since the arrest is typically due to hypoxemia. Few studies have evaluated the optimal pre-hospital airway management technique specifically for drowning victims with out-of-hospital cardiac arrest. A propensity score-matched pre-hospital registry study with nearly 12,000 patients found that compared with use of a supraglottic airway (SGA), tracheal intubation was associated with a slightly higher rate of return of spontaneous circulation (5.8 versus 4.7 percent), but there was no difference in one-month survival or good neurologic outcomes [5]. These results suggest that even though pre-hospital tracheal intubation may be the optimal approach, an SGA is an acceptable alternative. (See "Drowning (submersion injuries)", section on 'Bystander interventions and prehospital care'.)

GENERAL ADULT EMERGENCY MEDICINE

Reversal strategy for intracerebral hemorrhage associated with direct factor Xa inhibitors (May 2024)

The optimal reversal strategy for direct factor Xa inhibitors (apixaban, edoxaban, rivaroxaban) in acute intracerebral hemorrhage (ICH) is uncertain. In the ANNEXA-I trial, which randomly assigned 530 patients with factor Xa inhibitor-associated ICH to andexanet alfa or standard care (typically including a prothrombin complex concentrate [PCC]), patients assigned to andexanet had higher rates of hemostasis than those assigned to standard therapy (67 versus 53 percent) [6]. However, thrombotic events, including ischemic stroke and myocardial infarction, were more common with andexanet (10.3 versus 5.6 percent). Mortality and functional outcomes at 30 days were similar. Based on these results, we individualize selection of andexanet alfa or PCC for direct factor Xa inhibitor reversal in acute ICH and other life-threatening bleeding; previously, we favored andexanet in most cases. Andexanet may restore hemostasis more effectively than PCC but is associated with higher thrombotic risk. (See "Reversal of anticoagulation in intracranial hemorrhage", section on 'Reversal agent options'.)

ACEP consensus guidelines on topical anesthetics for simple corneal abrasions (April 2024)

Dispensing or prescribing a topical anesthetic for management of corneal abrasions in emergency department (ED) patients is generally discouraged because of concern of causing permanent corneal damage. The American College of Emergency Physicians (ACEP) published consensus guidelines recommending that in adult ED patients with simple corneal abrasions, prescribing or providing a commercial topical anesthetic for 24 hours (no more than 1.5 to 2 mL total) after presentation was safe and improved analgesia and patient satisfaction [7]. Even though we agree that brief use of a topical anesthetic for a small, simple corneal abrasion is safe and provides superior analgesia, we disagree with these broader recommendations since errors in diagnosis of corneal abrasions are common and overuse is difficult to prevent because topical anesthetic is typically supplied in 4 to 15 mL bottles. (See "Corneal abrasions and corneal foreign bodies: Management", section on 'Pain control'.)

Precautions for individuals with COVID-19 in the community (April 2024)

In March 2024, the United States Centers for Disease Control and Prevention updated guidance for precautions for people with COVID-19 in the community [8]. Such individuals should stay at home until their symptoms are improving and they have been afebrile for 24 hours without the use of antipyretics. They can subsequently resume normal activities but are encouraged to use other precautions (eg, masking, social distancing, good ventilation) for an additional five days to further reduce the risk of transmission to others. These measures are particularly important when around persons who are at increased risk for severe disease (eg, advanced age, immunocompromise, cardiopulmonary disease). (See "COVID-19: Infection prevention for persons with SARS-CoV-2 infection".)

Unchanged emergency department discharge rates for pulmonary embolism (April 2024)

Outpatient anticoagulation to avoid hospitalization is safe for a select group of patients with acute pulmonary embolism (PE). However, a recent study of over 1.6 million emergency department (ED) visits for PE in the United States reported that ED discharge rates for PE were unchanged between 2012 and 2020 (38 versus 33 percent) [9]. Among low-risk patients, only one third were discharged from the ED. However, this study was unable to determine whether other factors may have prevented discharge such as drug accessibility, concurrent deep vein thrombosis, and right ventricular burden. Although not conclusive, this study suggests that increased physician awareness is needed to encourage safe ED discharge of low-risk patients with PE. (See "Treatment, prognosis, and follow-up of acute pulmonary embolism in adults".)

Ideal oxygen targets in COVID-19 (April 2024)

In patients with acute respiratory failure due to coronavirus-2019 (COVID-19), ideal oxygenation targets are unclear. A recent study of spontaneously breathing or mechanically ventilated hospitalized adults with acute respiratory failure due to COVID-19 reported that targeting an arterial oxygen tension (PaO₂) ≥60 mmHg was associated with more days alive without ventilatory support compared with a target ≥90 mmHg [10]. However, there was no overall mortality benefit. Although the study was limited by lack of blinding and early cessation for slow enrollment, it supports our recommendation of targeting a peripheral oxygen saturation between 90 and 96 percent or PaO₂ ≥60 mmHg, when feasible. (See "COVID-19: Respiratory care of the nonintubated hypoxemic adult (supplemental oxygen, noninvasive ventilation, and intubation)", section on 'Oxygenation targets'.)

Ensitrelvir for mild to moderate COVID-19 (March 2024)

Although nirmatrelvir-ritonavir reduces hospitalization and death from COVID-19,drug interactions preclude its use in some patients. Ensitrelvir is an oral protease inhibitor that prevents SARS-CoV-2 replication and has fewer drug interactions. In a randomized, double-blinded trial of over 1800 patients with mild to moderate COVID-19 (majority vaccinated) in Asia in early 2022, five days of ensitrelvir reduced time to symptom resolution by one day compared with placebo [11]. Since only two participants (one in each arm) had a COVID-19-related hospitalization within the 28-day study period, it is unknown whether the drug prevents hospitalizations or death from COVID-19. Ensitrelvir is approved for emergency use in Japan; it is undergoing US Food and Drug Administration approval process in the United States. (See "COVID-19: Management of adults with acute illness in the outpatient setting", section on 'Therapies of limited or uncertain benefit'.)

Emergency physician-performed point-of-care ultrasound for cholecystitis (February 2024)

Emergency physician-performed point-of-care ultrasound can be helpful when evaluating an adult with right upper quadrant pain, but test characteristics vary depending on the operator and indication. A meta-analysis with over 1700 patients found that the sensitivity and specificity of point-of-care ultrasound for acute cholecystitis was 71 and 94 percent, respectively [12]. These findings suggest this rapid, bedside imaging modality can help expedite care if cholecystitis is identified but may not be sufficient to rule out the diagnosis. (See "Evaluation of the adult with nontraumatic abdominal or flank pain in the emergency department", section on 'Role of point-of-care ultrasound'.)

Guidelines on management of acute respiratory distress syndrome (February 2024)

The American Thoracic Society recently updated their guidelines on the management of patients ventilated for acute respiratory distress syndrome (ARDS) [13]. Compared with previous recommendations, emphasis was placed on the value of systemic corticosteroid administration, early use of extracorporeal membrane oxygenation, and use of neuromuscular blockade, particularly in patients with severe ARDS. Recommendations also focus on the avoidance of recruitment maneuvers, especially prolonged maneuvers. We agree with these recommendations. (See "Acute respiratory distress syndrome: Ventilator management strategies for adults", section on 'Introduction'.)

Time window to start dual antiplatelet therapy for high-risk TIA or minor ischemic stroke (January 2024)

There is evidence from several randomized trials that early initiation of short-term dual antiplatelet therapy (DAPT) for select patients with high-risk transient ischemic attack (TIA) or minor ischemic stroke reduces the risk of recurrent ischemic stroke. The evidence comes from trials that started DAPT within 12 to 24 hours of symptom onset. Results from the recent INSPIRES trial suggest that DAPT is still beneficial when started up to 72 hours after symptom onset [14]. Although the time window is extended by the results from INSPIRES, we start DAPT as soon as possible for patients with high-risk TIA or minor ischemic stroke. (See "Early antithrombotic treatment of acute ischemic stroke and transient ischemic attack", section on 'High-risk TIA and minor ischemic stroke'.)

GENERAL PEDIATRIC EMERGENCY MEDICINE

Concussion and mental health disorders in children and adolescents (March 2024)

Ongoing research continues to examine the complex relationship between concussion and mental health disorders. In a recent case-control study of over 18,000 children (≤17 years old) with concussion and over 37,000 matched controls, concussion was associated with an increased risk for a new diagnosis of a behavior disorder at two and four years after injury [15]. For most diagnoses, the absolute numbers were low. Confidence in a causal relationship is limited by risk of confounding and reliance on an electronic medical record for establishing lack of baseline behavioral problems prior to injury. Whether pediatric concussion is an independent risk factor for new behavioral problems after recovery remains unclear. (See "Concussion in children and adolescents: Management", section on 'Mental health disorders'.)

Increasing exposure to illicit fentanyl in young children in the United States (March 2024)

The potent opioid fentanyl is commonly implicated in fatal adult and pediatric poisonings, but there are limited data on accidental nonfatal exposures in young children. In the United States between 2013 and 2023, calls to poison control centers for children ≤6 years of age exposed to illicit fentanyl increased from 5 to 539 annually [16]. More than 80 percent were children ≤2 years old or were exposed at home. Most patients had severe effects and half received naloxone. These data confirm the seriousness of the presence of illicit fentanyl in the households of young children and suggest it as a focus for prevention measures. (See "Opioid intoxication in children and adolescents", section on 'Epidemiology'.)

PROCEDURES

New guidelines for airway management in infants (January 2024)

Very young children are at higher risk of complications of airway management than children in older age groups; however, guidelines for infants have been lacking. In 2024, the European Society of Anesthesiology and Intensive Care and the British Journal of Anesthesia published joint guidelines for airway management in neonates and infants [17]. A summary of their recommendations appears in the following table (table 1). (See "Airway management for pediatric anesthesia", section on 'Pediatric airway management guidelines'.)

Videolaryngoscopy for endotracheal intubation in critically ill children (January 2024)

Use of videolaryngoscopy (VL) in children provides a shared view during emergency endotracheal intubation (ETI) that permits an experienced physician observer to give assistance to the proceduralist. In a multicenter quality study of VL during ETI in pediatric intensive care units with standardized coaching by an attending, over 3500 ETIs were performed with VL, and use of VL increased from 30 percent to 89 percent of ETIs over four years [18]. Compared with direct laryngoscopy, VL was associated with lower adverse events (9 versus 15 percent). The majority of proceduralists were residents or fellows. These findings and prior studies confirm the safety of VL during emergency ETI in children and demonstrate the value of standardized coaching during the procedure for less experienced clinicians. (See "Technique of emergency endotracheal intubation in children", section on 'Video versus direct laryngoscopy'.)

TOXICOLOGY

Medetomidine found in United States and Canadian illicit fentanyl (May 2024)

Medetomidine, an alpha-2 adrenergic receptor agonist used as a veterinary sedative (similar to xylazine), has been found in illicit fentanyl in Philadelphia, Pittsburgh, Chicago, Toronto, and Vancouver [19]. Dexmedetomidine is the main active ingredient in medetomidine. Poisoning with alpha-2 adrenergic receptor agonists can cause sedation, bradycardia, and hypotension. However, it is unclear to what extent these adulterants are contributing to toxicity in patients with opioid overdose and whether naloxone reverses their toxicity compared with the coused opioid. Opioid adulteration with an alpha-2 adrenergic agonist should be on the differential diagnosis of patients with opioid overdose, but management largely remains administration of opioid reversal antidotes and supportive care. (See "Acute opioid intoxication in adults", section on 'Opioid adulterants, including krokodil' and "Clonidine, xylazine, and related imidazoline poisoning", section on 'Clonidine and other imidazoline medications'.)

New guidelines for cannabinoid hyperemesis syndrome (May 2024)

Cannabinoid hyperemesis syndrome (CHS) causes severe abdominal pain and vomiting that occurs in a cyclical pattern associated with prolonged, regular cannabis use. Standard antiemetics (eg, ondansetron, metoclopramide) are typically ineffective. The Guidelines for Reasonable and Appropriate Care in the Emergency Department (GRACE-4) from the Society for Academic Emergency Medicine suggest using dopamine antagonists such as droperidol or haloperidol in addition to usual care to manage symptoms of CHS in adult patients [20]. Capsaicin cream may be used as an adjunct but is often less effective. We agree with these guidelines, but typically reserve capsaicin for second-line therapy. (See "Cannabinoid hyperemesis syndrome", section on 'All patients: IV fluids, dopamine antagonists'.)

Multiple-dose activated charcoal for amatoxin-containing mushroom poisoning (March 2024)

Ingesting mushrooms that contain amatoxins can cause acute liver injury, liver and multisystem organ failure, and death. Multiple-dose activated charcoal (MDAC), which increases elimination of amatoxins by blocking enterohepatic recirculation, is a frequently used therapy, typically combined with other antidotes. A systematic review that included nearly 1200 patients (665 received MDAC, 2 received single-dose activated charcoal) with amatoxin-containing mushroom poisoning found that activated charcoal administration was associated with higher transplant-free survival (83 versus 75 percent) [21]. These findings support our recommendation to administer MDAC to patients with suspected amatoxin-containing mushroom ingestion. (See "Amatoxin-containing mushroom poisoning (eg, Amanita phalloides): Clinical manifestations, diagnosis, and treatment", section on 'Elimination enhancement'.)

Delta-8 tetrahydrocannabinol use by United States adolescents (March 2024)

Delta-8 tetrahydrocannabinol (THC) is typically a minor cannabinoid found in cannabis, but can also be synthesized. It is increasingly found in United States (US) cannabis products, often marketed as low delta-9 THC. A survey of US twelfth graders in 2023 found that 11 percent reported using delta-8 THC within the past 12 months, compared with 30 percent reporting marijuana use [22]. Delta-8 THC use was lower in states with cannabis legalization (8 versus 14 percent) or delta-8 THC regulation (6 versus 14 percent). These findings suggest that delta-8 THC is a public health concern in adolescents, particularly in states that do not regulate it and have not legalized marijuana for adult use. (See "Cannabis (marijuana): Acute intoxication", section on 'Cannabis formulations'.)

Xylazine and fentanyl detection in overdose deaths (March 2024)

Xylazine (street name "Tranq") is an alpha-2 adrenergic agonist increasingly found as an adulterant in or co-administered with illicit fentanyl; whether the combined use of xylazine with fentanyl or other opioids increases the risk of overdose death is unclear. In a retrospective study of over 3000 fentanyl-related overdose fatalities over four years, the median postmortem fentanyl concentration was higher in the 148 cases that also had xylazine detected; significantly more decedents with xylazine detected had very high fentanyl concentrations (>40 mcg/L) [23]. This finding suggests that co-administration of xylazine may permit tolerance to higher doses of fentanyl and may be associated with decreased, rather than increased, lethality. The mechanism of this effect is not clear and requires further study. (See "Clonidine, xylazine, and related imidazoline poisoning", section on 'Epidemiology'.)

Diethylene glycol poisoning outbreak in Indonesia (February 2024)

Diethylene glycol (DEG) ingestion causes gastrointestinal symptoms followed by an elevated anion gap metabolic acidosis, acute kidney injury (AKI), and delayed neurologic toxicity in survivors. Outbreaks continue to occur when DEG is substituted for the more expensive propylene glycol in liquid/syrup medications. In Indonesia in 2022, 52 previously healthy children who had taken a syrup-based antipyretic or cough medication were treated for rapidly progressing AKI [24]. DEG and/or ethylene glycol were identified in 16 out of 17 patients who had toxicology testing performed. Most children required kidney replacement therapy and 34 died. DEG and/or ethylene glycol poisoning must be on the differential diagnosis of any child with a rapidly progressing AKI. (See "Methanol and ethylene glycol poisoning: Management", section on 'Diethylene glycol'.)

Insulin-euglycemia therapy for phosphide poisoning (January 2024)

The metallic phosphide rodenticides, zinc and aluminum phosphide, cause shock, cardiac dysfunction, dysrhythmias, respiratory failure, and metabolic acidosis. In acute poisoning, mortality is very high, treatment is primarily supportive (including vasopressors, bicarbonate, and magnesium infusion), and no antidote exists. In a trial of 108 patients with aluminum phosphide poisoning and hypotension or acidosis, compared with supportive care and norepinephrine, insulin-euglycemia therapy reduced mortality (65 versus 96 percent) and tracheal intubation (61 versus 82 percent), and improved mean arterial pressure six hours after poisoning (65 versus 13 mmHg) [25]. These findings suggest that insulin-euglycemia therapy may be beneficial in critically ill patients poisoned with phosphide poisoning. (See "Overview of rodenticide poisoning", section on 'Zinc and aluminum phosphide'.)

Photobiomodulation therapy for local tissue damage from snake envenoming (January 2024)

Photobiomodulation therapy (also called low-level laser therapy [LLLT]) may decrease inflammation and enhance healing following envenoming by snake species that cause local tissue damage or myonecrosis. In a trial of 60 patients with Bothrops snakebites all of whom received antivenom, LLLT decreased pain intensity scores, extent of edema, and extremity circumference compared with no LLLT [26]. LLLT is a promising adjunct to antivenom, but more trials and access to equipment are needed before it can be recommended for routine use. (See "Snakebites worldwide: Management", section on 'Photobiomodulation'.)

National practice guidelines not associated with increased MOUD prescribing in the ED (January 2024)

In emergency department (ED) patients who survive an opioid overdose, initiation of medications for opioid use disorder (MOUD) is associated with decreased one-year mortality (approximately 5 percent without MOUD). However, prescribing rates are low and multiple barriers exist. A study of more than 20,000 ED visits for opioid toxicity in Canada found that even though MOUD prescribing increased between 2013 and 2020, it was still relatively low (<6 percent) and was not improved by the publication of Canadian clinical practice guidelines in 2018 [27]. These findings suggest that EDs and health systems need to make systematic efforts to implement and maintain MOUD-initiation programs that directly engage clinicians to overcome barriers and increase rates of prescribing. (See "Acute opioid intoxication in adults", section on 'Prevention of recurrent opioid overdose'.)

Methemoglobinemia in infants due to contaminated hospital water supply (January 2024)

Methemoglobinemia is a potentially life-threatening condition in which heme iron becomes oxidized, preventing oxygen delivery. A report from a hospital in Japan described methemoglobinemia in 10 neonates who were fed infant formula prepared with tap water from the general hospital water supply [28]. The cause was identified as high levels of nitrites, and the source was traced to contamination by an anticorrosion agent from the heating system that entered the water supply due to a malfunctioning valve. All 10 survived, although 3 required methylene blue therapy. Infants are especially susceptible to methemoglobinemia because they have lower baseline levels of the enzyme that converts heme iron back to its normal state. (See "Methemoglobinemia", section on 'Nitrates and nitrites (from foods, drugs, preservatives, and chemicals)'.)

Avoiding intubation in acutely poisoned but stable, unresponsive adults (December 2023)

In unresponsive patients with trauma or undifferentiated coma, tracheal intubation is generally recommended to protect the airway and prevent aspiration. However, the benefit of intubation is unclear in stable poisoned patients who have decreased level of consciousness but are oxygenating and ventilating adequately. In a randomized trial of 225 adults with acute poisoning and coma (GCS score ≤8), compared with airway management at the physician’s discretion, individuals not intubated unless hypoxia, seizure, vomiting, or hypotension developed had a lower likelihood of mechanical ventilation (18 versus 60 percent), intensive care unit admission (40 versus 66 percent), or adverse events from intubation (6 versus 15 percent); they also had a lower risk of pneumonia [29]. These findings support avoiding intubation solely for a GCS score ≤8 in stable, unresponsive poisoned patients who are expected not to deteriorate based upon the suspected poison (eg, ingestion of a short-acting sedative such as ethanol). (See "Initial management of the critically ill adult with an unknown overdose", section on '"A": Airway stabilization'.)

TRAUMA

Validation of a low-risk rule for children with blunt abdominal trauma (May 2024)

The Pediatric Emergency Care Applied Research Network (PECARN) has previously derived a clinical prediction rule in children with blunt abdominal trauma who are at low risk for intraabdominal injury (IAI) that requires acute intervention (eg, laparotomy, blood transfusion, or prolonged hospitalization). The PECARN rule has now been validated in a multicenter, prospective cohort of over 7500 children with blunt abdominal trauma [30]. As in the derivation cohort, the rule identified patients at low risk of IAI requiring acute intervention with high sensitivity (100 percent) and negative predictive value (100 percent; prevalence of IAI requiring acute intervention, 2 percent). Based on these findings, children at low risk according to the PECARN rule do not require abdominal and pelvic computed tomography during initial evaluation. (See "Pediatric blunt abdominal trauma: Initial evaluation and stabilization", section on 'PECARN low-risk rule'.)

Skin preparation prior to fracture repair (March 2024)

The optimal preparation of contaminated or dirty wounds and whether any skin preparation can influence surgical site infection (SSI) independent of other factors (eg, prophylactic systemic antibiotics) are unknown. In a multiple-period, cluster-randomized, crossover trial comparing skin preparation with iodine povacrylex in alcohol versus chlorhexidine gluconate in alcohol in 1700 open fracture repairs, the incidence of superficial or deep SSI was similar for both approaches [31]. Based on these findings, which are consistent with those from a previous trial, either chlorhexidine- or iodine-based skin preparations can be used prior to surgery for open, traumatic lower extremity wounds. (See "Surgical management of severe lower extremity injury", section on 'Limb preparation and skin antisepsis'.

Whole blood transfusion for severe traumatic hemorrhage (January 2024)

For severe traumatic hemorrhage, whole blood transfusion is an alternative to balanced component transfusion (1:1:1 ratio of packed red blood cells/plasma/platelets). In an observational study comparing these two approaches, low titer group O whole blood transfusion was associated with lower 24-hour mortality (8 versus 19 percent) and lower volume of blood products received at 72 hours (48 versus 82 mL/kg) [32]. The survival benefit was greatest in patients with shock or coagulopathy. While this study suggests improved outcomes for whole blood transfusion, randomized trials are needed to determine which transfusion strategy might be superior and which patients would benefit the most. (See "Ongoing assessment, monitoring, and resuscitation of the severely injured patient", section on 'Whole blood transfusion'.)