BMIからアセスメントする筋肉内注射時の適切な注射針刺入深度の検討

Appropriate Needle Insertion Depth for Intramuscular Injection Based on Assessment of BMI

要旨

　目的：BMIを指標とした実践に即した筋注時の針の刺入深度を明らかにすることである．

　方法：18歳以上の553名（男性259名，女性294名）を対象とし，身長，体重，三角筋部と中殿筋部の皮下組織厚，および三角筋厚を測定した．BMIと皮下組織厚の関連を明らかにし，また筋厚を参考にし，筋注に必要な実際的な針刺入深度を明らかにした．

　結果：三角筋部においては，皮下組織厚（cm）は男性0.04×BMI−0.25，女性0.04×BMI−0.17と表せた．ただし，BMI＜18.5の対象者の場合三角筋厚が薄いため，骨膜を損傷する恐れがあった．したがって，針の刺入深度は，18.5≦BMI＜30.0で1.5cm，BMI≧30.0で2.0cmとするのが適切と考えられた．中殿筋部においては，皮下組織厚（cm）は男性0.05×BMI−0.38，女性0.05×BMI−0.03と表せた．ただし，皮下組織厚の厚さからBMI≧30.0では皮下投与になる可能性があった．したがって，針の刺入深度は，BMI＜18.5では1.5cm，18.5≦BMI＜30.0では2.0cmとするのが適切と考えられた．

　結論：BMIを指標とした実際的な筋注における針の刺入深度は，三角筋部では18.5≦BMI＜30.0は1.5cm，BMI≧30.0は2.0cm，中殿筋部ではBMI＜18.5は1.5cm，18.5≦BMI＜30.0は2.0cmが適切と考えられた．

　Aim: The present study was conducted to clarify the appropriate needle insertion depth for intramuscular injection based on assessment of BMI.

　Methods: The participants were 553 individuals more than 18 years old. We measured their height, weight, subcutaneous tissue thickness over the deltoid and gluteus medius, and muscle thickness of the deltoid. We clarified the association between BMI and subcutaneous tissue thickness, with reference to muscle thickness, we clarified the appropriate needle length for intramuscular injection.

　Results: Subcutaneous tissue thickness over the deltoid was 0.04×BMI−0.25 in males, and 0.04×BMI−0.17 in females. However, in individuals with a BMI of ＜18.5, there was a risk of hitting the bone because the deltoid muscle was thin. Therefore, the appropriate needle length was 1.5cm for BMI ≤18.5−＜30.0, and 2.0cm for BMI≥30.0. Subcutaneous tissue thickness over the gluteus medius was 0.05×BMI−0.38 in males, and 0.05×BMI−0.03 in females. However, in individuals with a BMI of ≥30.0, there was a risk of subcutaneous injection because of thick subcutaneous tissue over the gluteus medius. Therefore, the appropriate needle length was 1.5cm for BMI＜18.5, and 2.0cm for BMI≥18.5−＜30.0.

　Conclusion: The appropriate needle insertion depth for intramuscular injection into the deltoid is 1.5cm for BMI＜18.5−＜30.0 and 2cm for BMI≥30.0, whereas that for the gluteus medius is 1.5cm for BMI ＜18.5 and 2.0cm for BMI≥18.5−＜30.0.