Cardiovascular complications of prehospital emergency anaesthesia in patients with return of spontaneous circulation following medical cardiac arrest: a retrospective comparison of ketamine-based and midazolam-based induction protocols

Abstract

BackgroundHypotension following intubation and return of spontaneous circulation (ROSC) after cardiac arrest is associated with poorer patient outcomes. In patients with a sustained ROSC requiring emergency anaesthesia, there is limited evidence to guide anaesthetic practice. At the Essex & Herts Air Ambulance Trust, a UK-based helicopter emergency medical service, we assessed the relative haemodynamic stability of two different induction agents for post-cardiac arrest medical patients requiring prehospital emergency anaesthesia (PHEA).MethodsWe performed a retrospective database review over a 5-year period between December 2014 and December 2019 comparing ketamine-based and midazolam-based anaesthesia in this patient cohort. Our primary outcome was clinically significant hypotension within 30 min of PHEA, defined as a new systolic BP less than 90 mm Hg, or a 10% drop if less than 90 mm Hg before induction.ResultsOne hundred ninety-eight patients met inclusion criteria. Forty-eight patients received a ketamine-based induction, median dose (IQR) 1.00 (1.00–1.55) mg/kg, and a 150 midazolam-based regime, median dose 0.03 (0.02–0.04) mg/kg. Hypotension occurred in 54.2% of the ketamine group and 50.7% of the midazolam group (p=0.673). Mean maximal HRs within 30 min of PHEA were 119 beats/min and 122 beats/min, respectively (p=0.523). A shock index greater than 1.0 beats/min/mm Hg and age greater than 70 years were both associated with post-PHEA hypotension with ORs 1.96 (CI 1.02 to 3.71) and 1.99 (CI 1.01 to 3.90), respectively. Adverse event rates did not significantly differ between groups.ConclusionPHEA following a medical cardiac arrest is associated with potentially significant cardiovascular derangements when measured up to 30 min after induction of anaesthesia. There was no demonstrable difference in post-induction hypotension between ketamine-based and midazolam-based PHEA. Choice of induction agent alone is insufficient to mitigate haemodynamic disturbance, and alternative strategies should be used to address this.

Cardiorespiratory consequences of attenuated fentanyl and augmented rocuronium dosing during protocolised prehospital emergency anaesthesia at a regional air ambulance service: a retrospective study

“…A post hoc power analysis calculation was performed to establish the sample needed to observe a decrease of 20% in hypotension based on a previous study in hypotension in medical patients (alpha value 0.05, beta value 0.2), resulting in the need to collect a dataset of 360 in each group [ 4 ]. Data relating to sex, age, weight, reason for PHEA, patient outcome, observations and drugs administered were extracted.…”

“…Drug dosing has remained a challenge; one in five trauma patients have been shown to have an episode of hypotension within the first ten minutes of induction of PHEA [ 3 ]. In medical patients, the statistics are worse, with over 50% of patients having an episode of hypotension recorded in one study [ 4 ]. The detrimental impact of hypotension on outcomes has been observed in a number of pathologies; in traumatic brain injury concerns have been raised for more than 30 years that any early episode of hypotension can result in increased mortality [ 5 ].…”

“…Over the last decade in the UK, many prehospital critical care services have transitioned to a regime involving 3 mcg/kg fentanyl, 2 mg/kg ketamine and 1 mg/kg rocuronium (‘3:2:1’) [ 7 ]. The consensus for medical patients in PHEA remains unclear; one study showed no difference between a ketamine or midazolam based regimen in rates of hypotension for post return of spontaneous circulation patients [ 4 ]. There has also been increasing evidence that a higher dose of rocuronium (≥ 1.4 mg/kg) may improve the first pass success (FPS) rate, particularly in those patients who are most unwell and have a high shock index [ 8 ].…”

Impact of enhanced personal protective equipment on safety and logistics of pre-hospital emergency anaesthesia during the COVID-19 pandemic: a retrospective crossover study

“… Patient safety outcome measures: first pass intubation success (FPS), airway rescue techniques and complications (namely hypoxaemia (SpO 2 <90% and hypotension SBP <90 mm Hg). [ 4 ]. Key timings (999 call to patient side, 999 call to pre-hospital emergency anaesthesia, pre-hospital emergency anaesthesia to hospital, hospital arrival to available and total job cycle duration).…”

“…Patient safety outcome measures: first pass intubation success (FPS), airway rescue techniques and complications (namely hypoxaemia (SpO 2 <90% and hypotension SBP <90 mm Hg). [ 4 ].…”