Respiratory failure following intercostal nerve blockade

Ultrasound-guided parasternal injection in dogs: a cadaver study

OBJECTIVES

To describe the technique of performing an ultrasound-guided distal parasternal intercostal block and to determine the distribution of two volumes of methylene blue dye solution injected in canine cadavers.

STUDY DESIGN

Prospective cadaver study.

ANIMALS

A group of seven canine cadavers weighing 12-34 kg.

METHODS

The space between the transversus thoracic and the internal intercostal muscles is a virtual cavity. Ultrasound-guided injections in the distal (parasternal) intercostal space were performed using dye solution at 0.05 mL kg^-1 in each intercostal space from the second to seventh (LV, low volume, six injections per dog) in one hemithorax, and 0.1 mL kg^-1 in the third, fifth and seventh intercostal spaces (HV, high volume, three injections in each dog) on the contralateral side. Anatomical dissection was carried out to describe dye spread characteristics and staining of intercostal nerves.

RESULTS

The ultrasonographic landmarks for injection were identified in each cadaver. In the LV group the solution was found in every intercostal space (36/36), whereas the HV injection stained six intercostal spaces in two dogs, five in two, and in two dogs the solution was found in four and three spaces, respectively, demonstrating multisegmental distribution. Intrapleural staining was observed after two injections.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasound-guided injection of 0.05 mL kg^-1 at the distal intercostal space resulted in staining of the intercostal nerve in all dogs when performed in every space and may be an appropriate alternative to previously reported techniques. A single injection of 0.1 mL kg^-1 may anaesthetize more than one intercostal nerve, but not consistently. Clinical investigations are warranted to better characterize and to refine this locoregional technique.

Effect of Intercostal Nerve Block with 0.5% Bupivacaine on Peak Expiratory Flow Rate and Arterial Oxygen Saturation in Rib Fractures

BACKGROUND

This prospective study was undertaken to evaluate the efficiency of intercostal nerve block (ICNB) with 0.5% bupivacaine (Marcaine) for pain relief in patients with rib fractures and to correlate the degree of pain relief with changes in the peak expiratory flow rate (PEFR) and oxygen saturation (Sao2).

METHODS

Twenty-one consecutive adult patients admitted with rib fractures associated with severe pain formed the basis of the study. Chest pain was scored on a four-point scale before ICNB, 1 hour after ICNB, and 24 hours after ICNB. Sao2 was measured before and immediately after ICNB. PEFR was measured before and immediately after ICNB.

RESULTS

Pain score and PEFR before and after ICNB showed statistically significant differences (p = 0.0000, df = 20). There was a significant difference between Sao2 before and after ICNB.

CONCLUSION

Significant increases in Sao2 and PEFR occur after ICNB with 0.5% bupivacaine, which also provides sustained analgesia, leading to improvement in respiratory mechanics.

Bupivacaine with and without epinephrine for intercostal nerve block

In a double-blinded study, 15 American Society of Anesthesiologists class I or II patients, following lateral thoracotomy with general anesthesia, were randomized into two groups for intercostal nerve block with either bupivacaine, 0.5%, and epinephrine, 1:200,000, or plain bupivacaine, 0.5%. Blood concentrations of bupivacaine, epinephrine, and norepinephrine were serially measured. Blood pressure, heart rate, respiratory rate, temperature, and electrocardiogram were monitored. Peak blood bupivacaine concentrations were significantly lower in patients receiving bupivacaine with epinephrine. Peak epinephrine concentrations were significantly greater in patients receiving bupivacaine with epinephrine, but still within a safe range. No significant differences were seen in heart rate, blood pressure, respiratory rate, or temperature between the two groups, and/no dysrhythmias occurred. Peak norepinephrine concentrations were not significantly different between the two groups. The potential risk of toxic bupivacaine blood concentrations associated with intercostal nerve blocks can be reduced by the addition of epinephrine at a concentration of 1:200,000.