Reducing cardiovascular responses to laryngoscopy and tracheal intubation: a comparison of equipotent doses of tramadol, nalbuphine and pethidine, with placebo.

The stress response to tracheal intubation may be obtunded by opioids given with induction of anesthesia. Tramadol is an opioid acting on mu-receptors and the monoaminergic pain modulating systems. This study examined vasomotor responses to tracheal intubation after equipotent doses of tramadol, nalbuphine and pethidine (3.0, 0.3 mg/kg(-1), and 1.5 mg/kg(-1), respectively), and placebo, given prior to induction of anesthesia in 118 healthy patients. Premedication and induction of anesthesia were standardized. Recordings of HR and SAP were made prior and subsequent to induction of anesthesia, and at 1, 3, 5 and 7 minutes after tracheal intubation. Prior to laryngoscopy and intubation, HR increased in all groups (p < or = 01, all comparisons), but least so after nalbuphine, whilst SAP remained unchanged after placebo, tramadol and pethidine, but fell after nalbuphine (p < 0.025). Maximum increases in HR (p < or = 0.005, all comparisons) and SAP (p < or = 0.02, all comparisons) occurred one minute after intubation. Maximum HR after placebo (108 SD 15 bpm), tramadol (107 SD 20 bpm), pethidine (113 SD 16 bpm) and nalbuphine (110 SD 26 bpm) was similar; with placebo HR remained faster than baseline until the seventh minute but had returned to baseline by the fifth minute with the opioids. Maximum SAP with tramadol (151 SD 26 mmHg) was similar to that with placebo (157 SD 20 mmHg), but was greater than after pethidine (136 SD 27 mmHg; p < 0.05) and nalbuphine (135 SD 19 mmHg; p < 0.02). With each test drug SAP returned to baseline by the third minute. It is concluded that, in these doses, 1) tramadol does not attenuate the chronotropic nor the inotropic response to tracheal intubation, and 2) pethidine and nalbuphine reduce only the inotropic response to airway instrumentation.