Trong y học, đặc biệt là tại các khoa điều trị đau, Lidocain là hoạt chất gây tê được ứng dụng vô cùng rộng rãi trong tiêm khớp hay phong bế thần kinh. Dù mang lại hiệu quả giảm đau vượt trội và được đánh giá là tương đối an toàn, người bệnh và nhân viên y tế vẫn không được lơ là trước những biến chứng nguy hiểm có thể xảy ra.
Lidocain (còn có tên biệt dược khác là Xylocain hay Lignocain) thuộc nhóm thuốc gây tê có cấu trúc amit. Điểm đặc trưng của Lidocain là khả năng gây giãn mạch tại vị trí tiêm, vì thế nó thường được phối hợp chung với các chất co mạch để hạn chế tối đa tốc độ hấp thu vào hệ tuần hoàn. So với Novocain, Lidocain có tác dụng nhanh, mạnh và kéo dài hơn đáng kể. Bên cạnh vai trò gây tê bề mặt và gây tê sâu, hoạt chất này còn được sử dụng để điều trị và chống loạn nhịp tim.
Về cơ chế tác động, Lidocain ức chế dòng ion natri đi qua màng tế bào thần kinh, giúp ổn định màng và ngăn chặn quá trình khử cực. Nhờ đó, thuốc phong bế sự phát sinh cũng như dẫn truyền các xung động thần kinh, mang lại hiệu quả vô cảm nhanh chóng cho một vùng cơ thể.
Lidocain được chỉ định rộng rãi trong kỹ thuật tiêm khớp và phong bế thần kinh
Ngoài ra, nhờ cơ chế chẹn kênh Na+ làm giảm nồng độ natri nội bào, Lidocain còn giúp chống loạn nhịp thất hiệu quả trong các trường hợp cấp tính như ngoại tâm thu thất, nhịp nhanh thất hay rung thất sau nhồi máu cơ tim, hoặc trong quá trình can thiệp tim mạch.
Các tác dụng không mong muốn thường gặp khi dùng Lidocain
Dù được sử dụng rộng rãi, Lidocain vẫn có thể gây ra nhiều tác dụng phụ tùy thuộc vào liều lượng và đường dùng thuốc:
– Khi gây tê thông thường: Bệnh nhân có thể gặp các triệu chứng như đau đầu, hạ huyết áp đột ngột, khó thở, rối loạn nhịp tim, block tim, ngủ lịm hoặc thậm chí là trụy tim mạch.
– Khi điều trị rối loạn nhịp: Dùng đúng liều thuốc khá an toàn. Tuy nhiên, nếu tiêm tĩnh mạch quá nhanh, thuốc dễ gây ra hội chứng yếu nút xoang hoặc làm tăng mức độ block nhĩ – thất sẵn có.
– Khi dùng liều cao hoặc kéo dài: Tiêm tĩnh mạch liều cao (trên 150mg) dễ dẫn đến tình trạng nhiễm độc thuốc với các biểu hiện như chóng mặt, tê bì vùng quanh miệng, nôn mửa, nhìn mờ, vật vã, co giật, giảm sức co bóp cơ tim và nhịp tim chậm.
– Trường hợp mẫn cảm nặng: Lidocain có thể kích hoạt các phản ứng dị ứng nghiêm trọng như viêm da, co thắt phế quản và sốc phản vệ nguy hiểm đến tính mạng.
Chống chỉ định tuyệt đối: Không tự ý hoặc sử dụng Lidocain cho người mắc hội chứng Adams-Stokes, block nhĩ – thất, rối loạn xoang – nhĩ, suy cơ tim nặng hoặc rối loạn chuyển hóa porphyrin.
Cách phòng ngừa và xử trí tai biến do Lidocain gây tê
Để đảm bảo an toàn tuyệt đối khi sử dụng Lidocain trong thực hành lâm sàng, các y bác sĩ cần đặc biệt tuân thủ các nguyên tắc sau:
– Chuẩn bị đầy đủ trang thiết bị cấp cứu: Luôn sẵn sàng các phương tiện hồi sức cấp cứu về thần kinh, hô hấp và tim mạch trước khi tiến hành gây tê cho bệnh nhân.
– Phối hợp chất co mạch hợp lý: Kết hợp Lidocain với Adrenalin giúp kéo dài thời gian tê và giảm thiểu độc tính. Tuy nhiên, tuyệt đối không dùng phối hợp này ở các vùng đầu chi (ngón tay, ngón chân, quy đầu) vì nguy cơ gây hoại tử do thiếu máu cục bộ.
– Kỹ thuật tiêm chính xác: Thực hiện thao tác chuẩn xác để tránh tiêm nhầm vào mạch máu. Tiêm sai vị trí, đặc biệt là vào vùng dưới nhện, vùng đầu, cổ hay quanh chân răng… có thể gây ngừng thở đột ngột.
– Thận trọng với các đối tượng đặc biệt: Phải giảm liều lượng rõ rệt ở người cao tuổi, người suy kiệt thể trạng, bệnh nhân cấp tính hoặc có bất thường về thần kinh. Đối với sản khoa, phong bế cạnh cổ tử cung bằng Lidocain liều cao có thể gây chậm nhịp tim thai hoặc nguy hiểm hơn là tử vong thai nhi.
– Hạn chế tiếp xúc kim loại: Do Lidocain phản ứng mạnh với kim loại gây kích ứng nặng tại chỗ tiêm, nên tránh để dung dịch thuốc tiếp xúc lâu với các bộ phận kim loại của bơm kim tiêm.
– Theo dõi sát sao khi gây tê tủy sống/ngoài màng cứng: Kỹ thuật này dễ gây hạ huyết áp và chậm nhịp tim. Nếu xuất hiện các dấu hiệu ngộ độc như bồn chồn, nhìn mờ, co giật, ngừng thở… cần lập tức hỗ trợ hô hấp, truyền dịch và dùng thuốc vận mạch cấp cứu.
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