Blunt Thoracic Trauma (BTT), Pain Management in

An evidence-based outcome evaluation

2nd review—2003

I Statement of Problem and Questions to be Addressed

Studies of the consequences and treatment of blunt thoracic trauma (BTT) remain hampered by a varying pathologic definition of the disease. Entities typically classified as BTT include chest wall lesions such as rib fractures, flail chest and soft tissue contusion; intrapleural lesions such as hemothorax and pneumothorax; parenchymal lung injuries such as pulmonary contusion and lung laceration; and finally mediastinal lesions such as blunt cardiac injury.^{[1] [2]} For purposes of this evidence-based review we are concerned primarily with those injuries to the chest wall that produce their morbidity through pain and it’s associated mechanical ventilatory impairment. Thus, blunt chest trauma (BTT) is defined here to include soft tissue trauma and injuries to the bony thorax such as rib fractures and flail chest.^[3]

Within the scope of this definition, the incidence and morbidity of BTT clearly remains significant. Rib fractures themselves are believed to be very common and have been documented in up to two thirds of the cases of chest trauma.^{[4] [5]} In another review 10% of all patients admitted to one trauma center had radiographic demonstration of rib fractures.^[3] Isolated single or multiple rib fractures are one of the most common injuries in the elderly, at about 12% of all fractures, with an increasing incidence recorded as the population ages.^[6] The true incidence of bony thoracic injury may be under-reported as up to 50% of fractures may be undetected radiographically^[7] .

For patients with blunt chest wall trauma the morbidity and mortality are significant. These injuries are associated with pulmonary complications in more than one-third of cases^[3] and pneumonia in as many as 30% of cases.^{[3] [8] [9]} Patients over 65 may be even more prone to major complications after blunt chest wall injury^{[3] [10] [11] [12]} with 38% respiratory morbidity from isolated rib fractures in another review.^[13] Since blunt chest wall trauma causes death indirectly, through pulmonary and non-pulmonary complications, the true mortality rate for these injuries is hard to evaluate. In one study, 6% of patients with blunt chest trauma died and at least 54% of these deaths could be directly attributed to secondary pulmonary complications.^[3] An elderly group of patients suffered an 8% mortality from isolated rib fractures.^[13] Mortality of isolated flail chest has been as high as 16%.^[14] The incremental costs attached to pulmonary complications of blunt chest trauma has not been addressed in the literature, but clearly would be measured in “ICU days” and “ventilator days”, both expensive commodities.

The treatment for injuries of the bony thorax has varied over the years, ranging from various forms of mechanical stabilization^{[15] [16]} through obligatory ventilatory support.^{[17] [18] [19]} It is now generally recognized that pain control, chest physiotherapy and mobilization are the preferred mode of management for BTT.^{[9] [20]} Failure of this regimen and ensuing mechanical ventilation sets the stage for progressive respiratory morbidity and mortality.^{[3] [8] [20]} Consequently, several different strategies of pain control have been employed, including intravenous narcotics, local rib blocks, pleural infusion catheters, paravertebral blocks and epidural analgesia. Each of these modalities has its own unique advantages and disadvantages and the overall most efficacious method has not previously been clearly identified. Subsequently, analgesic practices vary widely in this crucial setting. In one recent review, the majority of BTT patients were still managed with intravenous or oral narcotics.^[21] Other authors noted that epidural catheters were offered in only 22% of elderly BTT patients and 15% of a younger cohort.^[9]

This review seeks to identify the optimal method(s) of pain control for patients with blunt chest trauma. The specific questions which will be addressed utilizing an evidence-based approach for outcome evaluation are:

1. Which patients with blunt chest trauma are at particular risk for respiratory morbidity due to a pain and deserve special attention to pain management?
2. With consideration for safety, feasibility and therapeutic effectiveness, what is the optimal method of pain control in blunt chest trauma?
3. For the recommended modality / modalities, what technical recommendations can be made for the administration of analgesia in blunt chest trauma.
   1. Anesthetic and technology concerns
   2. Nursing considerations

II Process

A computerized search was conducted of the Medline, Embase and Cochrane controlled trials databases for North American and European English language literature for the period from 1966 through July 1, 2003. The initial search terms were “chest injuries”, “thoracic injuries”, “rib fractures” and “flail chest”. These were cross-referenced for the secondary terms “analgesia”, “anesthesia” and “pain”. This search initially yielded 213 articles. 128 of these articles were excluded as being case studies, reviews, letters, or otherwise irrelevant to the questions being asked. This yielded a file of 85 articles for review. An additional 51 articles were obtained from the references of these studies yielding a total of 136 studies for review and grading. 91 of these were deemed appropriate for inclusion in the final evidentiary tables.

The practice parameter workgroup for analgesia in blunt thoracic trauma consisted of five trauma surgeons, one trained as a thoracic surgeon, two anesthesiologists and one trauma clinical nurse specialist. All studies were reviewed by two committee members and graded according to the standards recommended by the EAST Ad Hoc Committee for Guideline Development.^[22] Grade I evidence was also sub-graded for quality of design utilizing the Jahad Validity Scale published in Controlled Clinical Trials in 1996.^[23] Any studies with conflicting grading were reviewed by the committee chairperson and were all Grade I studies. Recommendations were formulated based on a committee consensus regarding the preponderance and quality of evidence.

III Recommendations

A. Efficacy of Analgesic Modalities

Level I

1. Use of epidural analgesia (EA) for pain control after severe blunt injury and non-traumatic surgical thoracic pain significantly improves subjective pain perception and critical pulmonary function tests compared to intravenous narcotics. EA is associated with less respiratory depression, somnolence and gastrointestinal symptoms than IV narcotics. EA is safe with permanent disability being extremely rare and negligible mortality attributable to treatment.

Level II

1. Epidural analgesia may improve outcome as measured by ventilator days, ICU length of stay and hospital lengths of stay.
2. There is some class I and adequate class II evidence to indicate that paravertebral or extrapleural infusions are effective in improving subjective pain perception and may improve pulmonary function.

Level III

1. Though paravertebral or extrapleural analgesia is effective, there is an inadequate quantity of comparative evidence or information regarding safety to establish any recommendation with regard to overall efficacy.
2. The information regarding both the effectiveness and safety of intrapleural and intercostal analgesia is contradictory and experience with trauma patients is minimal. Consequently no recommendation can be made regarding overall efficacy of this modality.

B. Clinical Application of Pain Management Modalities to Treatment of Blunt Thoracic Trauma

Level 1

1. Epidural analgesia is the optimal modality of pain relief for blunt chest wall injury and is the preferred technique after severe blunt thoracic trauma.

Level II

1. Patients with 4 or more rib fractures who are>65 years of age should be provided with epidural analgesia unless this treatment is contraindicated.
2. Younger patients with 4 or more rib fractures or patients aged>65 with lesser injuries should also be considered for epidural analgesia.

Level III

1. The approach for pain management in BCT requires individualization for each patient. Clinical performance measures (pain scale, pulmonary exam / function, ABG) should be measured as judged appropriate at regular intervals.
2. Presence in elderly patients of cardiopulmonary disease or diabetes should provide additional impetus for epidural analgesia as these co­morbidities may increase mortality once respiratory complications have occurred.
3. Intravenous narcotics, by divided doses or demand modalities may be used as initial management for lower risk patients presenting with stable and adequate pulmonary performance as long as the desired clinical response is achieved.
4. High-risk patients who are not candidates for epidural analgesia should be considered for paravertebral (extrapleural) analgesia commensurate with institutional experience.
5. A specific recommendation cannot be made for intrapleural or intercostal analgesia based on the available evidence but its’ apparent safety and efficacy in the setting of thoracic trauma has been reported.

C. Technical Aspects of Epidural analgesic agents

Level I

There is insufficient Class I and Class II evidence to establish any specific techniques of epidural analgesia as a standard of care.

Level II

Combinations of a narcotic ( i.e. – fentanyl ) and a local anesthetic (i.e.­bupivicaine) provide the most effective epidural analgesia and are the preferred drug combinations for use by this route. Use of such combinations allows decreased doses of each agent and may decrease the incidence of side effects attributable to each.

Level III

1. While reliable literature describes the safe use of epidural analgesia on regular surgical floors, most victims of blunt thoracic trauma receiving this modality of treatment will have other primary indications for a higher level of care. Consequently, such patients in general, should be nursed in a monitored setting with cardiac monitoring and continuous pulse oximetry.
2. There is insufficient evidence at this time to make a recommendation regarding the use of continuous epidural infusion vs. intermittent injection in trauma patients.

IV Scientific Foundation

a. Historical Perspective

The treatment of blunt thoracic trauma has undergone dramatic evolution over the twentieth century. In the first half of the century, the primary emphasis was on mechanical stabilization of the bony injury. This was first done by such external devices as sandbags or traction systems, and later by various surgical methods such as wires or screws.^[24] After 1950, the concept of “internal pneumatic stabilization” with positive pressure mechanical ventilation was developed.^[25] This became more prevalent and obligatory mechanical ventilation became the standard for chest wall trauma.^[26]

The management of severe, blunt thoracic trauma evolved into the modern era with the publication of two studies in 1975. In a small series, Trinkle,^[27] demonstrated that optimal pain control, chest physiotherapy and noninvasive positive pressure ventilation could avert the need for intubation and mechanical ventilation. Also in 1975, Dittman ^[28] published the first in a series of 3 articles on pain management in blunt chest trauma. In the first study, nineteen patients with multiple rib fractures and flail segments were treated with continuous epidural analgesia while intubation and mechanical ventilation were withheld. Using objective clinical criteria to monitor progress ( vital capacity, respiratory rate and tidal volume), seventeen patients were successfully managed without positive pressure ventilation. Dittman ^[29] subsequently showed that 46 of 49 (94%) of spontaneously breathing patients maintained a vital capacity greater than 13 ml/kg and avoided positive pressure ventilation through the use of morphine analgesia via a thoracic epidural catheter. Other European studies demonstrated good clinical results with epidural analgesia in blunt chest wall injuries when combined with pulmonary toilet and selective mechanical ventilation.^[30-32]

Thus, the management of blunt thoracic trauma today focuses on both the underlying lung injury and on optimization of mechanics through chest physiotherapy and optimal analgesia.^{[30] [ 33-36]} The critical importance of measuring ventilatory function tests as an objective means of monitoring adequacy of this analgesia was emphasized by the authors of the early studies.^[33-36] Subsequent studies of pain management in blunt thoracic trauma patients would utilize the same methodology and additionally focus on comparisons between modalities and on objective outcome parameters.^{[ 37-40]}

b. Modalities of Analgesia

Intravenous Narcotic

Intravenous narcotics have historically been the initial and most prevalent modality for relief of surgical and traumatic pain of all types. They are administered either by intermittent injection when pain is noted by the patient,^[41] or continuous infusion.^[42] Most recently intravenous patient-controlled analgesia (PCA) has been developed to exploit the benefits of both methods.^{[43] [44]} In this modality a baseline intravenous infusion of morphine is provided and the patient may elicit an additional bolus for breakthrough pain.

The obvious advantages of intravenous narcotics are ease of administration and monitoring by nursing without the risks of an invasive procedure or need for specialized personnel. The efficacy of this modality for blunt chest wall trauma is controversial. Intravenous narcotics have been shown to improve pain scores and vital capacity, yet some clinicians consider them inadequate in this setting.^{[41] [43]} The disadvantages of systemic narcotics are the tendency to cause sedation, cough suppression, respiratory depression and hypoxemia.^[42]

Epidural Narcotics / Anesthetics

Epidural Analgesia (EDA) is a method whereby narcotics, anesthetic agents or combinations thereof are introduced into the spinal epidural space at the thoracic or lumbar level to provide regional analgesia. This is accomplished by introduction of a polyvinyl catheter into the epidural space and delivery of agents by either a bolus, continuous infusion, or more recently by a demand system.^{[32] [39] [45-50]}

The major advantage of EDA is its apparent effectiveness in the absence of sedation.^{[32] [39] [45-50]} Epidural has been shown to result in an increased functional residual capacity (FRC), lung compliance and vital capacity, a decreased airway resistance and increased pO2.^[45] Tidal volume is increased and chest wall paradox in flail segments in reduced.^[28] Patients with EDA generally remain awake and can cooperate with pulmonary toilet.^{[28] [47]}

There are numerous real and theoretical disadvantages to EDA. Insertion may be technically demanding. Epidural anesthetics can cause hypotension, particularly in the face of hypovolemia, and occasional epidural infection.^{[46] [47]} Epidural hematoma, accidental entry into the spinal canal and spinal cord trauma can also occur.^[45]

Inadvertent “high block” may lead to respiratory insufficiency. By combining an epidural narcotic with the anesthetic agent, the dose of anesthetic can be decreased and these effects mitigated. However, the narcotic can cause nausea, vomiting, urinary retention, pruritis and occasionally respiratory depression.^{[28] [42] [51]} The contraindications to epidural may prove problematic in the trauma patient. These include fever, coagulation abnormalities of even minor degrees and altered mental status. There is some anecdotal concern that the bilateral analgesia effect may mask the symptoms of intra-abdominal injury.^[52] Finally, nursing intensity in monitoring for the effects of sympathetic block is somewhat more demanding than that for intravenous analgesia.^[53]

Intercostal Nerve Block

Intercostal analgesia or “intercostal nerve block” traditionally involves individual injections of local anesthetic into the posterior component of the intercostal space.^{[45] [54-56]} Because of segmental overlap of intercostal nerves, it is necessary to induce block above and below any given fractured rib. Blocks of adequate scope have been shown to relieve pain with multiple rib fractures and improve peak expiratory flow rate and volume.^[57] However, the effect lasts only approximately six hours.

As a unilateral block, hypotension is rare and bladder and lower extremity sensation are preserved. The disadvantages of intercostal block include the need to palpate the fractured ribs for injection, and the need for multiple and repeated injections.^[45] Local anesthetic toxicity may theoretically occur because of the higher doses needed and the incidence of pneumothorax increases with the number of ribs blocked.^[58] Also, inducing block for upper rib fractures is technically difficult due to proximity of the scapula. Intercostal catheterization and continuous infusion has been successfully used and mitigates the need for multiple injections.^{[43] [54]} However, the anatomic endpoint of catheter placement, piercing of the “posterior intercostal membrane” is often unclear raising the possibility of misplacement.^[59-61] The full anatomic limits of the spread of intercostal drugs is unclear.^[60-61]

Intrapleural Anesthesia

Intrapleural analgesia involves placement of a local anesthetic agent into the pleural space via an indwelling catheter.^[62] The produces a unilateral intercostal nerve block across multiple dermatomes by gravity-dependent retrograde diffusion of agent across the parietal pleura.^[45] As a unilateral modality it has advantages similar to intercostal block as regards hypotension and bladder and lower extremity sensation. Successful use of this modality has been reported in blunt thoracic trauma patients.^{[38] [63-65]}

In terms of disadvantages, a significant amount of anesthetic may be lost if a tube thoracostomy is in place, which is often the case with trauma patients.^{[66] [67]} This can be mitigated by temporary “clamping” of the thoracostomy which in turn evokes concerns of tension pneumothorax. Conversely, in the absence of a tube thoracostomy, intrapleural catheter placement may cause a pneumothorax. The presence of hemothorax, also common in thoracic trauma patients may theoretically impair diffusion of anesthetic.^[68] Since distribution of agent is gravity-dependent, effectiveness also varies with patient position, catheter position and location of fractured ribs. Diffusion is most widespread when supine which is not optimal for pulmonary function in the trauma patient.^[45] Conversely, the semi-upright position may allow disproportionate diffusion inferiorly and adversely affect diaphragmatic function.^[69]

Thoracic Paravertebral Block

Figure 1. The anatomic location of delivery for the various modalities of regional thoracic analgesia From Karmakar MJ, Anthony MH, Acute Pain Management of Patients with Multiple Rib Fractures. J Trauma 2003; 54: 615-625

Thoracic Paravertebral block involves the administration of a local anesthetic agent in close proximity to the thoracic vertebrae. This can be achieved by intermittent injection, bolus via a catheter or continuous infusion and produces a unilateral somatic and sympathetic block which extended over multiple dermatomes.^{[31] [43] [66] [70-76]}

Despite the fact that little recent investigation has been done with his modality, its theoretical advantages are numerous. It does not require painful palpation of ribs, is not in conflict with the scapula and is felt by some to be technically easier than epidural.^{[74] [77]} Because there is no risk of spinal cord injury as with epidural, this modality can be instituted on sedated or anesthetized patients. It has few contraindications and requires no special nursing management.^{[73] [74]} The most common complications are vascular puncture, pleural puncture and pneumothorax.^[45] The unilateral nature of the block makes hypotension rare, preserves bladder sensation and allows monitoring of the lower extremity neurological exam when necessary.

The anatomic location of delivery for the various modalities of regional thoracic analgesia is illustrated in Figure 1.

c. Support for Risk Assessment in Blunt Thoracic Trauma

In 1993, Sariego,^[78] showed that while trauma score and ISS predicted mortality in blunt thoracic trauma, neither identfied those survivors who would develop pulmonary complications. Clearly, factors leading to pulmonary sepsis and / or mechanical ventilation set the stage for severe morbidity or mortality. Studies addressing risk assessment in blunt thoracic trauma are tabulated in table 2.

Extent of injury to bony thorax

In a very large (n=692) retrospective class II series, Svennevig ^[79] identified the presence of four or more rib fractures as an independent predictor of dramatically increased mortality. Patients with 3 or less fractures suffered only a 2.5% mortality while those with four or more had a 19% mortality (p<.05). Similarly, in a large (n=105,000) state registry review (Class III) Lee ^[80] noted a 4% mortality rate for 2,477 patients with three or more rib fractures and a 1% rate for a similar group with two or less fractures. (p<.001) The “two or less” fracture group had a statistically similar mortality to the control group in which the patients had no rib fractures.

Figure 2. From Ziegler V et al, Mortality and Morbidity of Rib Fractures. J Trauma 37:975-979

Finally, Ziegler,^[81] also in a large retrospective review (n=711), analyzed mortality in relation to incrementally increasing number of rib fractures. He found 5% mortality with 1-2 fractures, 13% mortality with 3-4 fractures and 29% mortality with 7 or more fractures. Analysis of these results did identify an inflection point for increased mortality at four fractures as noted in figure 2. It should be noted that only 6% of patients had isolated rib fractures and correction was not made for ISS, which tracked the number of fractures. Consequently, the contribution of the primary chest wall injury to mortality cannot not be isolated reliably.

Age

The salient class II study was performed by Bergeron and associates^[82] in 2002. His group prospectively divided 405 patients with rib fractures in to a “65 or above age group” and a “less than 65 age group”. The elderly patients had a significantly higher co­morbidity rate (61% vs. 8% p<.0001) Their analysis corrected for varying ISS, co­morbidity and a slight difference in mean fracture number. They identified a five times greater risk of dying in the over 65 age group (9% vs. 19% morality p <.01). This finding is most compelling since the elderly group had a significantly lower ISS despite their higher mortality. (p<.031)

Figure 3. Number of Rib Fractures vs. incidence pneumonia for Elderly and Young Populations. From Bulger EM, Rib Fractures in the Elderly. JTrauma, 48: 1040-1047

Finally, an elegant attempt to relate the cumulative or synergistic effects of age and extent of chest wall injury was made by Bulger and colleagues^[83] in their retrospective (class II) study of 458 blunt thoracic trauma patients. These authors also divided their population into a customary “65 or older group” and a “younger than 65” group which were well matched in terms of injury severity. Pneumonia and mortality occurred twice as frequently in the older group (31% vs. 17% and 22% vs. 10% respectively; both p<.01). Similarly, pneumonia and mortality tracked the number of rib fractures in both groups with a mortality odds ratio of 1.2 for each additional fractured rib at any age.(p<.001) Not surprisingly, the rate of pneumonia increased more rapidly with increasing rib fractures for the elderly group as noted in figure 3.

Figure 4. Number of Rib Fractures vs. % Mortality for Elderly and Young Populations. From Bulger EM, Rib Fractures in the Elderly. JTrauma, 48: 1040-1047

The critical finding in this study is that ventilator days, ICU days, hospital length of stay (LOS) and mortality increased more rapidly with increasing number of rib fractures for the elderly population. However, this difference was only statistically significant in the mid-range of rib fractures, three through six, giving rise to a characteristic curve for these parameters. (p<.05 or less) This distinctive pattern is illustrated in figure 4 by the “number of fractures vs mortality” plot.

The authors postulate that this characteristic curve results from the poor tolerance by the elderly for “moderate" levels of injury which are well tolerated by a younger cohort. At the upper extremes of chest wall injury, both groups do poorly and the curves again approach. All in all the cumulative effect of age and severity of chest wall injury was powerful. In this study, an elderly person with six rib fractures had a mortality risk of 24% and a pneumonia rate of 35% vs. 10% and 20% respectively for a younger patient. ((p<.05).

Co-morbidity

Barnea and colleagues^[84] retrospectively reviewed 77 elderly (age>65) with isolated rib fractures. They identified a strong relationship between non-survival and the presence of diabetes or congestive heart failure. (p=.0095 and .001 ) Similarly, Alexander^[85] retrospectively reviewed 62 elder patients with isolated rib. Complications occurred in 55% (n=17) of patients with cardiopulmonary disease ( “CPD+” for coronary artery disease or chronic obstructive lung disease) but in only 13% (n=4) of those without. (“CPD-“) (p<.05) Mortality occurred in only in the CPD+ group (10% n=3 p<.05) Upgrade in level of care was more common in the CPD + group. Length of ICU stay and hospital stay was double in the CPD+ group. (p<.03).

Conversely, Ziegler ^[81] in a retrospective review of 711 patients was unable to find a correlation between mortality and the co-morbidities of chronic obstructive lung disease (n=37), diabetes (n=55) or hypertension (n=155). There was also no increase in mortality noted for patients with coronary artery disease (n=116) as defined by a previous myocardial infarction or treatment for angina or for patients with a previous stroke (N=27) Specific statistical information is not provided in this study.

Concurrent extrathoracic injury

The cumulative effect of distant injury on the mortality of blunt thoracic trauma has rarely been specifically addressed. In Svennevig’s ^[79] retrospective, class II review of 652 blunt trauma patients previously discussed, the presence of one extrathoracic injury did not significantly increase mortality. However, the presence of two extrathoracic injuries increased mortality dramatically, and the highest death rate occurred in the thoracoabdominal injury sub-group. (see table 1)

This would not seem surprising as the injury severity score has traditionally been accepted as an overall predictor of mortality. However a number of studies suggest that ISS may not be a valid predictor of risk of death in the elderly.^{[86] [87] [88]} Consequently, the incremental effect of distant injury on the mortality of blunt thoracic trauma becomes difficult to assess.

d. Support for Choice of Pain Management Modality

1. Effectiveness of Analgesic Modalities

Thoracic Epidural Analgesia

Studies relating to epidural analgesia are summarized in table 3. The greatest recent experience with invasive, regional pain management in the Western world, and in North America in particular rests with epidural modalities (EDA). Yet there is minimal compelling evidence that EDA improves outcome in trauma patients. Review yielded only one credible study to this end; Ullman et al,^[39] in a landmark class I review in 1989 randomized 28 isolated blunt chest trauma (BCT) patient to receive continuous epidural narcotic or intermittent IV injection. The epidural group had significantly less ventilator days (3.1+ 1.4 vs 18.3+ 8.1, p<.05), shorter ICU length of stay ( 5.9+ 1.5 vs 18.7+5.3, p<.02), and shorter hospital length of stay (14.9+ 2.2 vs 47.7+14.6, p<.02). The EDA group also had a tracheostomy rate of 7% vs 38% for the control group. Though the sample size was small, the study was adequately powered to the detect the differences indicated.

In an early, class II study, Gibbons ^[30] in 1973, noted that 27 blunt chest trauma patients treated with lumbar EDA anesthetic required ventilatory support half as frequently as 30 patients who received intravenous narcotic or single dose intercostal blocks. However, randomization criteria are not specified and there was hesitancy to use thoracic EDA for upper rib fractures at that time. Similarly, in a retrospective study, Wisner ^[40] applied multiple logistic regression analysis to registry data of 465 elderly patients with blunt chest trauma. His group identified the use of EDA as an independent predictor of decreased mortality and pulmonary complications in elderly blunt trauma patients.

Similarly, though EDA is virtually routine in elective thoracic surgery, literature supporting improved outcomes are surprising scare for this popular application as well. The solitary class I study in this field was available only as recently as 2003. In this work, Della Rocca^[89] showed a 9 day versus 11 day hospital stay for 280 thoracotomy patients who received EDA compared to a similar control group. However, the application of outcome measures from an elective thoracic surgery population to the multiple trauma patient is without validation and conceptually problematic.

Conversely, while quality proof of improved outcome is limited, the evidence that epidural modalities improve subjective pain scores and a variety of pulmonary functions in blunt thoracic trauma patients is abundant and compelling. (see tabulation table “Epidural Analgesia”) Four additional class I studies,^{[37] [38] [42] [44]} five class two studies ^{[29] [30] [46] [50] [90]} and five class III studies ^{[28] [32] [49] [91] [92]} document significant improvements in commonly accepted analog pain scales and such pulmonary parameters as vital capacity, tidal volume, negative inspiratory force (NIF), maximum inspiratory flow rate (MIF) and minute ventilation (Ve). Among salient class I studies, Moon^[44] performed a randomized comparison of narcotic / anesthetic epidural with PCA in two well-matched groups (n=24) of blunt chest trauma patients. The EDA group had a continual increase in maximal inspiratory force (24% from baseline) over the first 3 days while the PCA group had an 18% decrease in the same period. Similarly, initial tidal volume (Vt) for the two groups was not significantly different. However, Vt for the PCA group fell 56% by day three while that for the EDA group rose by 48%. At the end of this study period, mean Vt was 590 ml for the EDA group vs. 327 ml for the PCA group.(p<.05). Subjective pain scores were similarly dramatically improved ( 3.8 for EDA vs 6.2 for PCA p<.05).

Similarly, Mackersie et al^[42] randomized 32 multiple rib fracture patients to receive fentanyl by either continuous epidural route or continuous intravenous infusion. Mean vital capacity (VC) was dramatically improved in the EDA group vs the IV group ( 5.1 ml/kg vs 2.8 ml/kg; p<.002) as was maximum inspiratory pressure ( 17 cm H20 vs 5.3 cm H20; p <..05). In this study there was no significant change produced in tidal volume, respiratory rate or minute volume assessed to either method. Though there was a trend toward better improvement in subjective pain scores with EDA, this did not reach statistical significance for the small study group. Similarly, in an early, but sizeable class II observational study, Worthley^[47] treated 147 non-ventilated patients with bolus EDA using local anesthetic. A doubling of vital capacity was noted after each dose of the epidural. 9% of patients required mechanical ventilation.

The literature derived from elective thoracic surgery is similarly supportive of the benefits of epidural modalities. Four credible class I studies totaling over 600 patients document very significant improvements in subjective pain control and pulmonary function.^{[89] [93-95]} One well-designed, class I study failed to identify any subjective pain score benefits to lumbar epidural fentanyl vs. continuous fentanyl infusion.^[96] However, the study population was small (n=30), combination epidural anesthetic was not used and dosing was subjectively titrated for equivalent pain control. Conversely, in a very large prospective review of 2670 EDA patients and 1026 IVA controls, Flisberg ^[97] noticed dramatic improvement in subjective pan scale.

Other Analgesic Modalities

Little evidence exists for the efficacy of other modalities of invasive, regional analgesia. Ideally these methods should first be compared to control cases receiving intravenous medication to establish baseline effectiveness. They should then be compared to epidural modalities, with which the most experience exists so as to identify the most effective technique. Studies relating to other modalities of analgesia are summarized in tables 4 through 6.

Paravertebral block as described in greater detail above, is a method in which a bolus injection of anesthetic or a continuous infusion is delivered to the thoracic paravertebral space at the level of rib fractures producing a unilateral, multilevel somatic and sympathetic block.^{[72] [74]} This method is essentially a modality of extrapleural analgesia as the drug is delivered posterior to the parietal pleura but anterior to the costotransverse ligament near the spine. While there are a number of anecdotal reports, ^{[70] [71] [98-100]} the evidence supporting this modality in trauma patients or general thoracic patients is scant. In a small prospective study, (class II) Gilbert^[70] administered a single paravertebral anesthetic dose to a mixed group of patients suffering blunt or penetrating thoracic trauma. VC increased by 65%, and respiratory rate decreased by 35%, both to highly significant degrees. Pain scale improved significantly while measures of flow rates (MMEFR and FEV1/FVC) were unchanged. In a similar class II, prospective study, Karmakar^[76] administered continuous paravertebral anesthetic to fifteen patients with isolated unilateral rib fractures. There was highly significant (all p<.01 to .0001) sustained improvements in analog pain scores, vital capacity, and peak expiratory flow rate (PEFR). Interestingly, oxygen saturation (SaO2) and O2 index (paO2/FiO2 ratio) also improved significantly. (P<.05)

Extrapleural analgesia is a technique closely related to the paravertebral modality whereby a catheter is positioned in an extrapleural location and a continuous infusion of local anesthetic is delivered. In a prospective class I study, Haenal ^[43] administered continuous extrapleural anesthetic to fifteen patients with three or more unilateral rib fractures without other injuries. Visual analog pain scale halved and incentive spirometry doubled. This was significant despite the small study size.(p<.05) The authors of this study further noted that an anesthesiologist was not utilized to initiate this therapy at their institution. Similar results have been reported in two class II ^{[102] [104]} and one class I ^[103] study in the thoracic surgery literature.

Intrapleural catheters are placed percutaneously in patients with or without chest tubes and used to infuse local anesthetics. They have also been placed through the tracts of in situ tube thoracostomies. Among the salient class I studies, Gabram ^[104] randomized 42 blunt chest trauma patients to receive systemic narcotics (IVA) or intrapleural anesthetics (IPA) Half the IVA group required crossover to another modality or received mechanical ventilation while this occurred in only 10% of the IPA group. (p<.05) Changes in pulmonary functions did not reach statistical significance. In a randomized, blinded study Kottenbelt ^[64] administered intrapleural anesthetic or intrapleural saline to 120 blunt and penetrating trauma patients. 62% of the test group but only 15% of the placebo group received satisfactory analgesia by a visual analog scale. (p<.00001) Additionally, responders in the treated group had maintenance of their pain relief for a significantly longer period. (3.9 hrs vs. .9 hours; p<.005) Pulmonary functions were not assessed. Conversely, in a class I blinded study of IPA anesthetic vs. IPA placebo in 16 blunt trauma patients, Short ^[68] identified no difference in pulmonary function tests, arterial blood gases, subjective pain score or breakthrough narcotic use. It is noted that the study size was limited. In similar study, Schneider ^[105] found no benefit to IPA in terms of pain scale, length of stay or sparing of intravenous narcotics.

Intercostal block (ICB) was initially performed both by multiple single injections but more recently through a percutaneously placed catheter.^[31] Murphy ^[54] retrospectively reviewed 57 trauma and general surgery patients treated with multiple intercostal catheter injections of bupivicaine. In this anecdotal, class III study, patients allowed chest wall palpation and appeared to tolerate physiotherapy better after catheter injection. Analgesia duration was 8 to 12 hours with one dose. All further reviews of ICB were embedded in comparative studies and will be considered as such below.

Comparative Studies

Few comparative studies of the treatment of thoracic pain are to be found in the trauma or general thoracic literature. Shinohara ^[38] performed a small, randomized cross-over study examining intrapleural (IPA) and epidural (EDA) in 17 patients with multiple unilateral rib fractures. Subjective pain scores were similar, but since IPA induced a unilateral sympathetic block, blood pressure did not fall with IPA while it did with EDA. This difference was not significant however. Luchette and associates ^[37] similarly performed a prospective randomized comparison of continuous EDA anesthetic vs intermittent IPA anesthetic in nineteen blunt thoracic trauma patients. Their epidural patients had significantly less pain at rest and with motion and this difference continued to widen and was dramatic by day three. Breakthrough IV narcotic use was proportionately different also. Most importantly in this study, tidal volume and negative inspiratory pressure differences were highly significant by day 3 in favor of the epidural route. ( All p<.05) Vital capacity and minute volume were unaffected. .These authors concluded that continuous epidural was superior to the intrapleural route in terms of pain control and pulmonary function improvement. Though performed in thoracic surgery patients (N=40), Bachmann-Mennenga ^[56] carried out an elegant randomized four-limb study comparing intercostal block, intrapleural analgesia, thoracic epidural block and intravenous narcotic. In their study intercostal and epidural produced the greatest pain relief to a high degree of significance (p<.01) and had commensurate low levels of narcotic use. Intrapleural block had no narcotic-sparing effect over baseline IV analgesia even though catheter placement was confirmed at surgery. It was postulated that the thoracostomy tubes were draining off the anesthetic agent. Though most effective, the epidural route gave the least systemic anesthetic levels. The authors concluded that epidural an intercostal anesthetics constituted the most effective modalities for control of thoracic pain. Other studies in thoracic surgery patients show preference for intrapleural over intercostal analgesia and paravertebral over intrapleural routes.^{[37] [38] [55] [56] [66]} However all comparative studies are few and their total patient numbers small. Comparative studies are summarized in table 7.

2. Complications and Safety of Analgesic Modalities

Epidural

A number of sizeable studies have addressed the safety of epidural analgesia in various populations. Scherer^[106] performed a prospective observational ( class II) study of 1071 patients in which he reviewed the complication rates but did not address the incidence of expected minor side effects. Patients received epidural narcotic or combination narcotic / analgesic. His group’s findings are indicated in table 8.

Overall treatment related complications were seen in 37 patients (3.5%). The peripheral nerve damage seen in .8% of patients was limited to tingling in various extremities, all of which resolved spontaneously. It is not clear if some of these may have been related to patient positioning during surgery. There were no sensory or motor deficits, meningitis or permanent neurologic sequelae. Though 116 patients (10.8%) showed at least one abnormal clotting parameter, there were no clinical hemorrhagic events related to the procedure. One patient experienced respiratory depression temporally related to injection which required intubation. He recovered without sequelae. The authors concluded that EDA was a safe modality with minimal risk of technique –related or pharmacological complications.

Similarly, Ready^[107] and colleagues retrospectively reviewed 1100 postoperative epidural catheters managed outside of an intensive care setting. Narcotics only were used and therefore anesthetic complications such as hypotension were not assessable. These authors noted significant rates of pruritis (25%) and nausea (29%), though neither of these complications were disabling and were generally managed successfully. The only significant catheter-related problem was dislodgment which occurred at the rate of 3%. The salient complications noted in this study are summarized in table 9.

It should be noted for completeness that as of April 1998, the Food and Drug Administration had recorded fifty spontaneous anecdotal safety reports describing the development of epidural hematomas with the concurrent use of low molecular weight heparins (i.e. – enoxaparin sodium) and epidural analgesia. The use of these medications for deep venous thrombosis prophylaxis may be a relative contraindication to epidural modalities.^{[108] [109]}

Several studies have attempted to address comparative EDA complication rates against a control of intravenous narcotic.^{[39] [42] [89] [92] [93] [95-97]} These studies are summarized in table 10 In general, the smaller studies are often conflicting and fail to identify the same differences in types or rates of complications.^{[39] [42] [92-94]} When considering several larger class I and II comparative reviews, it is evident that each modality has a unique complication profile but that in both cases, the rates of significant morbidity are low. Intravenous analgesia tends to have significantly more respiratory depression, central sedative effects and gastrointestinal effects. Conversely epidural modalities tend to have more peripheral neurologic effects, pruritis, and when anesthetic agents are used, mild hypotensive effects. Luchette et al reported significant hypotenson with test boluses of Lidocaine.^[37] However, all in all both modalities have similar, excellent safety profiles.

Other Modalities

The single large class II review of paravertebral analgesia, achieved with local anesthetic agents prospectively identified a 10% failure rate in 367 cases.^[75] (see table 11) Hypotension requiring treatment occurred in 4.6%. Vascular puncture without morbidity occurred in 3.8% Pleural puncture without pneumothorax occurred in 1.1% and an additional .5% of patients (n=18) developed a pneumothorax. Some degree of contralateral anesthesia occurred in 1%. There were no instances of entrance into the spinal canal. It should be noted that these cases were accrued from three institutions and therefore represent only modest experience at each center. The time course of the study is not specified and the yearly experience at each institution may be small, thereby accounting for the increased complication and failure rate. Though the authors felt the complication rate was similar to that for epidural, other studies have identified lower epidural complication rates at approximately 3%.^{[39] [42] [89] [95]} Regardless, no serious complications attributable to PVA were noted in this study. Other studies on paravertebral analgesia are tabulated in the table. A solitary case of transient Horner’s Syndrome was reported.^[76] The single small class II study of the closely-related extrapleural analgesia noted no drug or catheter-related complications.^[43]

The majority of small class I studies addressing the safety of intrapleural catheters identify no significant drug or catheter related complications for a total of 151 patients.^{[38] [55] [64] [68] [104]} However one prospective observational study of 18 patients noted 11 incorrectly positioned catheters.^[110] Seven were in lung tissue and three in the chest wall. One tension pneumothorax resulted. The authors postulated that these poor results were experience-dependent. In a small randomized comparative study, Richardson ^[66] noted significant bupivicaine toxicity with intrapleural catheters that did not occur with the paravertebral route. Studies addressing the safety of intrapleural analgesia are summarized in table 12.

The solitary retrospective, class III study addressing complication of intermittent intercostal block via an indwelling catheter, identified no catheter or drug-related complications in 57 patients.^[54] (see table 13)

e. Technical Recommendations regarding conduct of Epidural Analgesia

Studies regarding technical recommendations for the conduct of epidural analgesia are summarized in table 14.

1. Pharmacology

In 1990, Cicala and colleagues^[111] compared the effectiveness of a thoracic epidural local anesthetic to a lumbar epidural narcotic in blunt trauma patients. This group found that both modalities were equally effective in decreasing pain scores and the anesthetic agent was modestly superior in improving pulmonary function tests. The sample size was small (n=14) though the study was randomized and blinded. The authors theorized that the anesthetic agent benefits pulmonary function by blocking inhibitory neural impulses destined for the diaphragm thereby improving diaphragmatic function.

The bulk of the information regarding the pharmacology of epidural analgesia arises from elective thoracic surgical literature. In a randomized blinded study of 53 thoracic surgery patients, Logas showed that epidural narcotic was significantly more effective than anesthetic in subjective pain relief.^[94] The combination was even more effective. Similarly, other randomized, blinded studies have showed lower pain scores and greater IV narcotic sparing with combination therapy as compared to epidural narcotic or anesthetic alone.^{[112] [113]} Also, it is possible to use lower doses of both agents when used in combination.^[112]

2. Mode of Infusion

The only study comparing continuous to bolus epidural in trauma patients (blunt and penetrating) was conducted by Kurek and colleagues^[114] in 1997. In this retrospective study, the continuous infusion method had a slightly, though significantly higher complication rate (p<.05) than the bolus route. The most common complications with the continuous method were motor blockade (18%), nausea/vomiting (18%) and catheter leaks (12%). For bolus infusions nausea/vomiting ( (25%), mental status changes (21%) and local erythema (13%) were most common. There were no serious or permanent complications in either group.

3. Nursing Environment

Ready and colleagues^[53] conducted a large retrospective review (n=1106) of a mixed patient population with epidural catheters managed at a general surgical floor level of care. Catheter related complications occurred in less than 5% of patients. None were serious complications and there were no deaths.

IVA = Intravenous analgesia, EDA = epidural analgesia, IPA = intrapleural analgesia, EPA = extrapleural analgesia, PVA = paravertebral analgesia, ICB = intercostal block, PFTS = pulmonary function tests, ABG = arterial blood gases

V Summary

In identifying the patients at high risk for morbidity and mortality from blunt chest trauma, outcome clearly worsens with increasing numbers of rib fractures and increasing age. However, identifying a true “inflection point” in the morality curve at which to apply our resources is difficult for either of these parameters. Additionally, as a marker of overall injury severity, it is unclear to what extent ameliorating the effects of fractures themselves will improve outcome. Consequently, studies such as those by Svennevig^[10] which identify rib fractures as an independent predictor of mortality are the most valuable. Yet, it should be remembered that the mortality identified in all studies is nonetheless real, and attempts to minimize the thoracic contribution to that mortality is appropriate for those patients at significant risk of dying.

While it is clear that certain analgesic modalities improve subjective pain sensation, the importance of this to recovery, other than in the humanistic sense is unclear. While improvement in objective pulmonary function can clearly be documented, the correlation of this to outcome remains somewhat elusive. Just how much improvement in vital capacity is needed to significantly impact ventilator days, or ICU length of stay, or survival? While most would conceptually agree that improved pulmonary parameters are a good sign in blunt chest injury, the factors affecting outcome particularly in multi-trauma patients are complex and interwoven. Significant populations of isolated chest-injured patients are difficult to mobilize for study. Studies derived from elective thoracic surgery are certainly more available and clearly deal with isolated chest wall pain. However their validity as models of trauma patients are questionable at best, at least in terms of outcome measures.

As far as effectiveness and complication rates for various modalities, it is reasonable to assume that regional anesthetic techniques, like surgical procedures, have a significant learning curve. Lack of experience with a given modality may contribute to lower success rates and increased complications thereby negatively impacting on the tendency for future investigation.. Modalities such as intrapleural, extrapleural or paravertebral analgesia may have greater potential for safety than has been realized and fewer contraindications which may thus augment their applicability to a trauma population. If efficacy were adequately documented, each of the described modalities offers the promise of it’s own unique advantages which would further enhance the armamentarium and pain control flexibility of the trauma surgeon and trauma anesthesiologist. However, the only analgesic modality for which widespread experience exists today in trauma patients is that of epidural administration of narcotics and anesthetics. It is clear that epidural administration of narcotic / analgesic combinations are highly effective in controlling subjective pain and improving pulmonary function. In experienced hands its’ rate of complication is minimal and of significant morbidity virtually negligable. Contraindications particularly prevalent in the trauma patient, such as slightly abnormal coagulation, spinal fractures and fever may limit its use though the extent to which this occurs is not known.

Consequent to the above issues, this group’s recommendations reflect what is known and reasonable regarding identification of those patients at risk from blunt thoracic injury and those analgesic modalities most likely to provide a net positive effect on their outcome.

VI Areas for Future Development

Based on assessment of current and recent work, the following areas are appropriate for further research:

1. Outcome studies regarding epidural analgesia in trauma patients -the effect on primary outcomes of this widely used modality needs to be better defined.
2. Outcome studies involving pulmonary function parameters - A correlation needs to be established between improvements in pulmonary function and outcome measures so as to define specific physiologic goals for therapies
3. Effectiveness / safety of other modalities. – additional investigations need to further evaluate the basic and comparative efficacy of intrapleural, paravertebral / extrapleural and intercostal modalities. Each of these modalities holds the promise of specific advantages and could extend the flexibility of analgesia if efficacy and safety could be better defined.
4. New Frontiers – Emerging modalities such as liposomal –encapsulated anesthetic agents (ref) offer the potential for safer and more prolonged regional anesthesia. Trauma surgeons should partner with anesthesiologists to evaluate the applicability of new analgesic modalities for thoracic trauma patients.

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Evidentiary Tables