Painful regional anaesthesia induces an immunological stress reaction: the model of retrobulbar anaesthesia

Short term general anesthesia for retro-bulbar block in ophthalmic surgery generates no significant hypercapnia

To assess the impact of short time hypnosis for retro-bulbar anesthesia on ventilation in patients undergoing ophthalmic surgery of the anterior eye chamber. In all patients, a combined continuous transcutaneous carbon dioxide tension (PtcCO₂) and partial oxygen saturation (SpO₂) measurement was applied in addition to routine monitoring. To enable unconscious application of retro-bulbar anesthesia, intravenous thiopental was given in one to multiple bolus doses. Transient breathing support included chin lift, Esmarch maneuver and manual hand-bag ventilation via face mask. Main endpoints were apnea time, recovery time according to the Richmond Agitation Sedation Scale, as well as SpO₂ and PtcCO₂ readings at predefined time points. Fifty-two patients with a mean age of 68 ± 13 years were included. Average thiopental dose was 2.7 ± 0.6 mg/kg. In seven (13.5%) patients repeated doses of thiopental were necessary to a total of 3.3 ± 1.1 mg/kg. Except one patient, no severe, significant or clinical relevant hypercapnia or desaturation periods were observed, and the occurring elevation of PtcCO₂ values did not correlate with the application of repeated doses of thiopental or the need for the Esmarch maneuver. Higher PtcCO₂ values were associated with the presence of hypertension and smoking. Apnea (p < 0.001) and recovery (p = 0.003) time were significantly prolonged in the patients needing the Esmarch maneuver. Short term anesthesia with thiopental in ophthalmic surgery is associated with a mild but not clinically relevant hypercapnia.

Cataract surgery anaesthesia: is topical anaesthesia really better than retrobulbar?

PURPOSE

To compare the effectiveness for the patient of retrobulbar anaesthesia (RBA) and topical anaesthesia (TA) in cataract surgery by phacoemulsification.

METHODS

We performed a prospective, randomized study on 115 patients operated at our clinic using the two anaesthesia techniques. The RBA group comprised 57 patients (20 women, 37 men; age 72 +/- 10 years); the TA group comprised 58 patients (20 women, 38 men; age 74 +/- 10 years). Measured parameters were: blood pressure; heart rate; blood oxygen saturation level; serum adrenaline, noradrenaline and cortisol levels; white blood cell count; indicated pain during the procedure, and pain as reported by the patient afterwards. Two psychological tests were used: the State-Trait Anxiety Inventory (STAI), and the patient-selected face-scale test. Statistical analysis was performed using Student's t-test and the chi-square test. Results were also analysed using a logistic regression model.

RESULTS

Both types of anaesthesia were adequate for the surgical procedure. In the RBA group fewer patients experienced pain during surgery (p < 0.01) and fewer recalled any perioperative discomfort. With RBA the objective parameters were more stable than with TA, and systolic blood pressure was significantly lower (p = 0.01). The logistic model was able to predict perioperative pain with 93% certainty. Pain sensitivity was higher in younger patients and in patients with higher initial cortisol and noradrenaline serum levels.

CONCLUSIONS

Both methods of anaesthesia are appropriate, but phacoemulsification with TA is more painful than with RBA. In hypertonic patients and younger patients who are more susceptible to pain, TA should be avoided or used in combination with individualized sedation.

Oral premedication with low dose midazolam modifies the immunological stress reaction after the setting of retrobulbar anaesthesia

BACKGROUND/AIMS

An acute immunological stress reaction was previously reported to occur after the painful setting of retrobulbar anaesthesia before intraocular surgery. This study was conducted to find out whether an oral low dose premedication with midazolam would modify the immunological stress reaction.

METHODS

32 patients undergoing intraocular surgery using retrobulbar anaesthesia were included in a randomised, double blind trial. They received premedication with either 3.75 mg midazolam or placebo 30 minutes before the retrobulbar injection. Counts of leucocyte subpopulations, cardiovascular, and psychometric parameters were measured repetitively before and after the retrobulbar injection.

RESULTS

The numbers of leucocytes increased significantly in the placebo group after the setting of retrobulbar anaesthesia (before retrobulbar injection: 6687 (SD 1025) cells x10(6)/l; after injection: 7067 (1022) cells x10(6)/l, p=0.0009) caused by rising numbers of neutrophils (before injection: 4111 (1063) cells x10(6)/l; after injection: 4352 (1147) cells x10(6)/l, p=0.0007) and natural killer cells (before injection: 290 (84) cell x10(6)/l; after injection 354 (133) cells x10(6)/l, p=0.003). There was no significant increase in total leucocytes (before injection: 5997 (1288) cells x10(6)/l; after injection: 6189 (1215) cells x10(6)/l) or in any leucocyte subpopulation in the midazolam group. A significant rise in systolic blood pressure occurred in the placebo group, but not in the midazolam group.

CONCLUSION

A low dose premedication with midazolam attenuates the immunological and cardiovascular stress reactions occurring with retrobulbar anaesthesia.