Chapter 47. Safety During Transport of Critically Ill Patients
Susana B. Martins, M.D., M.Sc.
Kaveh G. Shojania, M.D.
University of California, San Francisco School of Medicine
and Institute for Health Policy Studies
Background
The care of acutely ill patients routinely includes
transportation, both within a given hospital to undergo tests and procedures,
and between hospitals, as patients may require transfer to other facilities for
specialized services. Critically ill patients in particular commonly require
such transfers and are at high risk for complications en route.1-4
Developing practices to reduce or minimize this necessary risk represents a
potentially important area of patient safety research. This chapter focuses on
transportation of critically ill patients by health professionals (paramedics,
nurses, physicians and/or respiratory therapists) between hospitals (to receive
higher levels of care) and within the hospital (for diagnostic or therapeutic
procedures).
Stabilization before transport, in the field or in the
transferring hospital, and the mode of transferring patients from the field to
specialized centers also present important research and policy
questions.5 However, we regarded these issues as clinical research
topics and quality improvement issues for the fields of pre-hospital and
emergency medicine, rather than patient safety in general, and so do not review
this literature here.
Practice Description
Intrahospital transport refers to transportation of
patients within a hospital for the purpose of undergoing diagnostic or
therapeutic procedures or transfer to a specialized unit. In the context of this
chapter, this generally involves movement of critically ill patients from
intensive care areas of the hospital (including intensive care units, emergency
departments, operating theaters and recovery rooms) to areas typically not
involved in the delivery of such care (e.g., a hospital radiology department).
Equipment and staffing used for intrahospital transport varies by hospital,
clinical service and patient acuity. Studies of intrahospital transport have
mainly focused on the adequacy of patient monitoring and ventilator support. The
specific practices evaluated in this chapter include:
- The continued use of mechanical ventilation instead of switching to
manual ventilation. Manual ventilation involves a self-inflating
bag with or without a volumeter, while mechanical ventilation consists of a
portable, time-cycled, volume-constant transport ventilator.
- The use of specialized transfer units during intrahospital
transport. The unit is attached to the patient's bed and contains all
equipment necessary to meet the patient's needs (ventilation, monitoring and
infusion of drugs) in the ICU and during transport. The unit works as a
stand-alone unit.
Interhospital transport refers to transportation of
patients between hospitals by ground or air ambulance. Interhospital transport
teams vary widely in composition, training and experience. The transport team
does not always include a physician; even when a physician is present, his or
her training may not include skills necessary for this task.6-8
Nurses and respiratory therapists frequently accompany critically ill patients
during interhospital transport. Some paramedics receive special training in
skills necessary for the interhospital transport of critically ill
patients.9 As with physicians, the training of nurses and respiratory
therapists assigned responsibility for interhospital transport varies widely.
Equipment used during interhospital transport also varies widely,6,7
but the practices evaluated in the literature mainly relate to the use of
specialized transport teams.
Specialized transport teams characteristically receive
consistent and high levels of training and experience in the transportation of
critically ill patients,10-12 compared with teams assembled ad
hoc. Further details of the composition of these teams are presented in
connection with the specific studies reviewed below (see Table 47.1). Because of
the relative paucity of studies of practices for improving the safety of patient
transport, we have reviewed the pediatric and adult literature together.
Prevalence and Severity of the Target Safety
Problem
Adverse events during transport of critically ill patients fall
into two general categories: mishaps related to intensive care (e.g., lead
disconnections, loss of battery power, loss of intravenous access, accidental
extubation, occlusion of the endotracheal tube, or exhaustion of oxygen supply),
and physiologic deteriorations related to critical illness (e.g., worsening
hypotension or hypoxemia). Unfortunately many studies do not distinguish clearly
between these 2 categories. Further complicating assessments of patient
transport as a safety problem is the confounding effect of patient selection, as
patents requiring intra- or interhospital transport likely represent a sicker
patient population than unselected critically ill patients. In fact, one
case-control study reported no differences in adverse events (equipment-related
or physiologic) in critically ill adults during the period of intrahospital
transportation as compared to matched subjects in the ICU.13
Death during transport is a rare event. The majority of studies
reported no mortality during intrahospital transport13-17 or
interhospital transport,18,19 and some do not mention
deaths.21-23,24
For intrahospital transport of critically ill patients,
reported rates of adverse events range from 5.9% to
66%.13,14,16,21,22,25 (We could find no comparable reports of event
rates for critically ill children.) Much of this variation undoubtedly reflects
definitional differences, but differences in patient populations also contribute
to this wide range. For instance, a prospective study of 50 high-risk adult
cardiac patients reported arrhythmias in 84% of patients, with 52% of these
arrhythmias providing an indication for emergency treatment.17 These
event rates are clearly much higher than would be observed in an unselected
population of critically patients. Similarly, Insel et al showed a significantly
higher incidence of hemodynamic changes requiring therapeutic intervention when
intrahospital transport involved transfers from the operating room to the ICU
compared with patients transported from the ICU to diagnostic
procedures.26
In contrast to the above, the literature on adverse events
during interhospital transport has generally involved critically ill children,
not adults. Reported rates of adverse events during pediatric interhospital
transport range from 0 to 75%.2,10-12,19,24,27-29 In one of these
studies, a prospective cohort design reported a morbidity ratio of 1.85 (95% CI:
1.12-3.06) for pediatric patients transported from another hospital to the
pediatric ICU (PICU) as compared with those admitted directly (emergency room
and wards). Importantly, this increased morbidity reflected an increased rate of
"intensive care events" such as plugged endotracheal tubes and loss of
intravenous access, not an increase in physiologic events. Patients experiencing
such adverse events tended to have higher morbidity scores (on the PRISM scale)
and lower therapy level (TISS) scores prior to transport. Thus, as noted above,
confounding of differences in patient sickness and intensity of therapy could
account for much of the observed variation in transport-associated
morbidity.24
Opportunity for Impact
A survey conducted in 1990 to review voluntary compliance with
the American Academy of Pediatrics (AAP) recommendations to include physicians
with higher level of training (at least 3rd year residency) reported
that only 28% of hospitals with a pediatric critical care transport team met
this recommendation. All teams included a nurse with pediatric experience and a
varying degree of training, and 50% of teams included a respiratory
therapist.7
Return to Contents
Subchapter 47.1. Interhospital Transport
Study Designs and Outcomes
We identified 3 studies with at least a Level 3 study design
and Level 2 outcomes (see Table 47.1). Two of these studies10,12
involved pediatric patients. One12 reported the prospective comparison of
outcomes for high-risk pediatric patients admitted to two different ICU's, one
of which employed a specialized transport team, while the other followed the
standard practice of using non-specialized teams. The specialized team consisted
of a second-year pediatric resident and a pediatric ICU nurse, both trained in
pediatric advanced life support, and a respiratory therapist with pediatric
experience. Non-specialized teams varied in composition—a physician was not
always present and level of training in pediatric care for other personnel was
not standardized. The other pediatric study, from England,10
retrospectively compared outcomes using a specialized team for the transport of
intubated newborns from hospitals within 80 miles to a NICU at a referral center
to outcomes during a control period in which transport was performed by ad
hoc doctor/nurse teams. The specialized teams included physicians with more
years of experience and dedicated transport nurses with specialized training, as
well as slight equipment improvements (humidifier for ventilator and
invasive/noninvasive blood pressure monitoring).
The third study (the one involving adults) describes the
experience of a London teaching hospital that receives critically ill patients
from other facilities by two methods: either accompanied by the receiving
hospital's special retrieval team consisting of an ICU physician, nurse, and
medical physics technician (a technician to fix and maintain equipment) or
standard ambulance transport, with an escorting physician supplied by the
referring hospital.
The 2 pediatric studies10,12 reported adverse events
during transportation. We counted adverse events related to intensive care (e.g.,
accidental extubation) as Level 2 and physiologic events (e.g., ph < 7.2) as
Level 3. (A case could be made for classifying both types of adverse events as
Level 3, as neither has a clearly established relationship to adverse events of
interest). All studies provided information on case mix in the study and control
groups.
Evidence for Effectiveness of the Practice
Although of theoretical and practical concern, the literature
to support the scope, frequency and outcome of adverse events during
transportation is sparse and methodologically weak. Most studies are small
descriptive studies of local practices. Factors that limit comparability between
studies include a variety of definitions for transport-related adverse events,
unclear descriptions of transport team training and experience, diverse
equipment availability and different scoring systems for severity of illness
(APACHE II, APACHE III, Glasgow Coma Scale, PRISM, etc). Many confounders affect
the evaluation of transportation of a critically ill patient, among them
selection bias, the intervention received at primary hospital, time spent at
primary hospital, adequate stabilization before transport and duration of
transport.
As shown in Table 47.1, 2 studies involving pediatric
populations revealed reductions in intensive care-related adverse events through
the use of specialized teams for interhospital transport.10, 12 In
one of the studies, patients transported by the standard (non-specialized) team
were older and more likely to have trauma as a diagnosis.12 This difference in
patient populations clearly limits the ability to interpret the results,
although the direction of bias this might introduce is not clear. The other
pediatric study 10 reported no significant differences in basic
clinical and demographic factors between the 2 patient populations, but did not
report PRISM scores.
The single study in adults did not report intensive
care-related adverse events, but did observe significant reductions in surrogate
physiologic markers and a non-significant reduction in mortality within 12 hours
of arrival at the receiving facility. Although an observational study, there
were no differences in the patient populations in terms of demographic factors,
basic physiology measurements (FiO2, PaO2,
PaCO2, PaO2/FiO2, MAP, heart rate and
temperature) or sophisticated measures of severity of illness (APACHE II,
Simplified Acute Physiological Score-SAPS II).
Studies were underpowered to detect significant mortality
differences.
Potential for Harm
A delay in the transfer of critically ill patients to referral
hospitals because the specialized team is not available in timely fashion could
create a potential for harm although one study showed no delay or cancellation
due to unavailability of specialist team.11
Costs and Implementation
Although no firm recommendation can be made, the costs and
implementation requirements may only be feasible for tertiary centers that have
enough volume to justify the investment in human and physical resources. Time
out of hospital will vary depending on the time required to stabilize the
patient—not the focus of our study. (One study reported an increase in
stabilization time from 80-105 minutes (p<0.0001) after the implementation of
a specialized team10 and another reported no difference in duration
of transport between non-specialized and specialized team.12) The
third study did not mention duration of transport.
Comment
This practice has high face validity, and what little evidence
exists does support the practice. No direct potential for harm exists, but
adopting this practice without further study might unnecessarily strain scarce
healthcare resources. Moreover, if adopted as a standard of care, lack of timely
availability of designated transport personnel may become a factor in delaying
inter-facility transfers. For some critically ill patients, the time lost in
assembling the transport team may have a greater negative impact than the safety
gained by their eventual presence. Further research on this topic is required,
fundamentally controlling for confounders and improving outcome measures to
include morbidity. Two areas that have evolved enormously over the last 2
decades are training requirements of health personnel and the quality of
transport monitoring and ventilation equipment.
Return to Contents
Subchapter 47.2. Intrahospital Transport
Study Designs and Outcomes
As shown in Table 47.2, the 3 studies of manual versus
mechanical ventilation employed a randomized (or quasi-randomized) controlled
design. Randomization procedures were not described in two studies30,31 and used the last digit of the patient record in one
study.32 The quasi-randomized study32 implemented a
crossover design using manual ventilation or transport ventilator on one leg of
the journey and vice-versa on the other leg.
Two studies reported on Level 2 and 3 outcomes30, 32
and one on level 3 outcomes,31 venous pressure, oxygen saturation,
PetCO2 and mean airway pressure during transport. All studies report
on before-after variation, one study30 also reported on minute
variations during the first 8 minutes of transport (see Table 47.2). Only one
study reported scores for severity of illness (PRISM).30 Case-mix was
inadequately reported in one study31 and not reported in
another.32
It is worth briefly noting a third practice which involves the
use of mobile bed/monitor units versus standard procedure for intrahospital
transportation. Studies on this topic are limited to descriptive experiences of
local practice with no definition or systematic evaluation of adverse
events,17,33-35 so these practices were not reviewed further.
Evidence for Effectiveness of the Practice
The clinical significance of the hyperventilation observed in
manually ventilated patients during intrahospital transportation has yet to be
determined. Mechanical ventilation was associated with respiratory alkalosis
when precision of ventilatory settings was inaccurate. No adverse effect, (i.e.,
morbidity) was observed as a result of the method of ventilation. Use of a
volumeter when manually ventilating a patient reduced the risk of
hyperventilation. Studies were underpowered to detect significant mortality
differences.
Potential for Harm
Inadequate maintenance and/or precision of transport ventilator
may create an opportunity for harm.
Costs and Implementation
Portable mechanical ventilators are much more expensive,
require more hours of training to manipulate and frequent use to maintain
experience. Costs were not mentioned.
Comment
One randomized controlled trial in pediatric postoperative
cardiac patients showed an increase in markers of hyperventilation for patients
in the manually-ventilated group. Otherwise, manual ventilation appears to
achieve results comparable to portable mechanical ventilation. Use of a
volumeter when manually ventilating patients, and the addition of a blender to
reduce FiO2 when manually ventilating neonates,30 may
adequately reduce the risks of hyperventilation, rendering mechanical
ventilation during intrahospital transport unnecessary.
Table 47.1. Specialized transport teams versus standard care for
interhospital transport
Study Setting |
Study Design, Outcomes |
Main Results |
Critically ill children transported to two PICU's in Albany, NY
(specialized transport team) and Syracuse, NY (standard care):
1992-9412 |
Level 3, Level 2 |
Significant decrease adverse event related to intensive care for
patients transported with specialized team compared to standard care: 1/47
(2%) vs. 18/92 (20%), p<0.05
For physiologic adverse events the decrease was minimal and not
significant: 5/47 (11%) vs. 11/92 (12%) p>0.05 |
Intubated newborns transported by specialized doctor/nurse team
(increased training and experience) to NICU in Nottingham, England:
1994-95, and historical control period during which non-specialized (ad
hoc) doctor/nurse team transported patients to the same NICU:
1991-9310 |
Level 3, Levels 2&3a |
Nonsignificant reduction in endotracheal tube-related events (blocked
or dislodged endotracheal tubes): 0/146 (95% CI: 0-3.2%) patients
transported by specialized teams vs. 3/73 (4.1%, 95% CI: 1.1-12.3%) by ad
hoc teams
Reductions also observed in adverse physiologic end-points; such as
abnormal ph (p<0.05) and abnormal temperature (p<0.001) |
Critically ill adults transported to a university ICU in London:
1996-1997; specialist team with mobile ICU compared with emergency
ambulance with medical escort11 |
Level 3, Levels 1&3 |
Mortality within 12h of arrival at the receiving facility: 5/168 (3%,
95% CI: 1.1-7.2%) vs. 7/91 (7.7%, 95% CI: 3.4-15.7%)
70% reduction in number of patients arriving in serious metabolic
acidosis when transported by a specialist team (p=0.008): pH<7.1: 5/168
(3%) vs. 10/91 (11%)
50% reduction in number of patients arriving in a dangerously
hypotensive state when transported by a specialist team (p=0.03):
MAP<60mmHg 15/168 (8.9%) vs. 16/91 (17.6%)
|
Table 47.2 Manual versus mechanical ventilation for intrahospital
transportation
Study Setting |
Study Design, Outcomes |
Main Results |
30 ventilator dependent, critically ill adults in ICU: manually
ventilated with self-inflating bag group, manually ventilated
self-inflating bag with volumeter, and mechanically ventilated group
(Federal Republic of Germany)31 |
Level 1, Level 3 |
Pre/post transport: PaCO2 decreased from 41 ± 2 to 34 ± 2 (p<0.01) and
pH increased from 7.40 ± 0.02 to 7.46 ± 0.03 (p<0.05) after manual ventilation, and
PaCO2 decreased from 40 ± 1 to 35 ± 2 (p<0.01) and pH increased from 7.42 ± 0.01 to 7.47 ± 0.01
(p<0.01) after using transport ventilator. No differences were observed
in the group that received manual ventilation with a volumeter. |
28 critically ill adults and adolescents transported from emergency
department for diagnostic procedures in a University Hospital: manual
ventilation versus transport ventilator (US)32 |
Level 1, Level 2&3 |
Pre/post transport: PaCO2 decreased from 39 ± 4 to 30 ± 3 (p<0.05) and
pH increased from 7.39 ± 0.03 to 7.51 ± 0.02 (p<0.05) after manual ventilation as compared
to conventional ventilation. No differences between transport mechanical
ventilation and conventional ventilation. No significant changes in
oxygenation, heart rate or blood pressure in either group.
2/14 patients had supraventricular tachycardia (no clinical
significance) during transport in the manually ventilated group and none
in the transport ventilator group. |
51 pediatric postoperative cardiac surgery patients who were
transported within hospital while intubated: manually ventilated versus
mechanically ventilated (US)30 |
Level 1, Level 2&3 |
Pre/post transport: Statistically significant decrease in
PetCO2 [32 ± 1.6 to 26 ± 1.4] in manually ventilated as compared to
mechanically ventilated [35 ± 1.1 to33 ± 1.7] patients (p=0.02). No significant difference in
other ventilatory parameters, airway pressure and hemodynamic
parameters.
Minute-to-minute variations: greater amount of fluctuation and lower
mean values in PetCO2 (p<0.05) in the manually ventilated
group when compared to the mechanically ventilated group.
No clinical changes reported. |
References
1. Pollack MM, Alexander SR, Clarke N, Ruttimann UE, Tesselaar HM, Bachulis
AC. Improved outcomes from tertiary center pediatric intensive care: a statewide
comparison of tertiary and nontertiary care facilities. Crit Care Med
1991;19:150-159.
2. Kanter RK, Tompkins JM. Adverse events during interhospital transport:
physiologic deterioration associated with pretransport severity of illness.
Pediatrics 1989;84:43-48.
3. Borker S, Rudolph C, Tsuruki T, Williams M. Interhospital referral of
high-risk newborns in a rural regional perinatal program. J Perinatol
1990;10:156-163.
4. McCloskey KA, Faries G, King WD, Orr RA, Plouff RT. Variables predicting
the need for a pediatric critical care transport team. Pediatr Emerg
Care 1992;8:1-3.
5. Young JS, Bassam D, Cephas GA, Brady WJ, Butler K, Pomphrey M.
Interhospital versus direct scene transfer of major trauma patients in a rural
trauma system. Am Surg 1998;64:88-91; discussion 91-92.
6. Dryden CM, Morton NS. A survey of interhospital transport of the
critically ill child in the United Kingdom. Paediatr Anaesth
1995;5:157-160.
7. McCloskey KA, Johnston C. Pediatric critical care transport survey: team
composition and training, mobilization time, and mode of transportation.
Pediatr Emerg Care 1990;6:1-3.
8. Gentleman D, Jennett B. Audit of transfer of unconscious head-injured
patients to a neurosurgical unit. Lancet 1990;335:330-334.
9. Domeier RM, Hill JD, Simpson RD. The development and evaluation of a
paramedic-staffed mobile intensive care unit for inter-facility patient
transport. Prehospital Disaster Med 1996;11:37-43.
10. Leslie AJ, Stephenson TJ. Audit of neonatal intensive care
transport-closing the loop. Acta Paediatr 1997;86:1253-1256.
11. Bellingan G, Olivier T, Batson S, Webb A. Comparison of a specialist
retrieval team with current United Kingdom practice for the transport of
critically ill patients. Intensive Care Med 2000;26:740-744.
12. Edge WE, Kanter RK, Weigle CG, Walsh RF. Reduction of morbidity in
interhospital transport by specialized pediatric staff. Crit Care Med
1994;22:1186-1191.
13. Hurst JM, Davis K, Johnson DJ, Branson RD, Campbell RS, Branson PS. Cost
and complications during in-hospital transport of critically ill patients: a
prospective cohort study. J Trauma 1992;33:582-585.
14. Szem JW, Hydo LJ, Fischer E, Kapur S, Klemperer J, Barie PS. High-risk
intrahospital transport of critically ill patients: safety and outcome of the
necessary "road trip". Crit Care Med 1995;23:1660-1666.
15. Wallen E, Venkataraman ST, Grosso MJ, Kiene K, Orr RA. Intrahospital
transport of critically ill pediatric patients. Crit Care Med
1995;23:1588-1595.
16. Indeck M, Peterson S, Smith J, Brotman S. Risk, cost, and benefit of
transporting ICU patients for special studies. J Trauma
1988;28:1020-1025.
17. Taylor JO, Chulay, Landers CF, Hood W, Abelman WH. Monitoring high-risk
cardiac patients during transportation in hospital. Lancet
1970;2:1205-1208.
18. Macnab AJ. Optimal escort for interhospital transport of pediatric
emergencies. J Trauma 1991;31:205-209.
19. Barry PW, Ralston C. Adverse events occurring during interhospital
transfer of the critically ill. Arch Dis Child 1994;71:8-11.
20. Duke G, Green J. Outcome of critically ill patients undergoing
interhospital transfer. Medical Journal of Australia
2001;174:122-125.
21. Smith I, Fleming S, Cernaianu A. Mishaps during transport from the
intensive care unit. Crit Care Med 1990;18:278-281.
22. Andrews PJ, Piper IR, Dearden NM, Miller JD. Secondary insults during
intrahospital transport of head-injured patients. Lancet
1990;335:327-330.
23. Braman SS, Dunn SM, Amico CA, Millman RP. Complications of intrahospital
transport in critically ill patients. Ann Intern Med
1987;107:469-473.
24. Kanter RK, Boeing NM, Hannan WP, Kanter DL. Excess morbidity associated
with interhospital transport. Pediatrics 1992;90:893-898.
25. Kalisch BJ, Kalisch PA, Burns SM, Kocan MJ, Prendergast V. Intrahospital
transport of neuro ICU patients. J Neurosci Nurs 1995;27:69-77.
26. Insel J, Weissman C, Kemper M, Askanazi J, Hyman AI. Cardiovascular
changes during transport of critically ill and postoperative patients. Crit
Care Med 1986;14:539-542.
27. Bion JF, Wilson IH, Taylor PA. Transporting critically ill patients by
ambulance: audit by sickness scoring. Br Med J (Clin Res Ed)
1988;296:170.
28. Waddell G, Scott PD, Lees NW, Ledingham IM. Effects of ambulance
transport in critically ill patients. Br Med J 1975;1:386-389.
29. Britto J, Nadel S, Maconochie I, Levin M, Habibi P. Morbidity and
severity of illness during interhospital transfer: impact of a specialised
paediatric retrieval team. BMJ 1995;311:836-839.
30. Dockery WK, Futterman C, Keller SR, Sheridan MJ, Akl BF. A comparison of
manual and mechanical ventilation during pediatric transport. Crit Care
Med 1999;27:802-806.
31. Gervais HW, Eberle B, Konietzke D, Hennes HJ, Dick W. Comparison of blood
gases of ventilated patients during transport. Crit Care Med
1987;15:761-763.
32. Hurst JM, Davis K, Branson RD, Johannigman JA. Comparison of blood gases
during transport using two methods of ventilatory support. J Trauma
1989;29:1637-1640.
33. Link J, Krause H, Wagner W, Papadopoulos G. Intrahospital transport of
critically ill patients. Crit Care Med 1990;18:1427-1429.
34. Holst D, Rudolph P, Wendt M. Mobile workstation for anaesthesia and
intensive-care medicine. Lancet 2000;355:1431-1432.
35. Hanning CD, Gilmour DG, Hothersal AP, Aitkenhead AR, Venner RM, Ledingham
IM. Movement of the critically ill within hospital. Intensive Care Med
1978;4:137-143.
Return to Contents
Proceed to Next Chapter